/BundleTransformer.SassAndScss/Resources/sass_in_one.rb

# This is necessary to set so that the Haml code that tries to load Sass
# knows that Sass is indeed loading,
# even if there's some crazy autoload stuff going on.
SASS_BEGUN_TO_LOAD = true unless defined?(SASS_BEGUN_TO_LOAD)

# This is necessary for loading Sass when Haml is required in Rails 3.
# Once the split is complete, we can remove it.
#require 'erb'
require 'set'
require 'enumerator'
require 'stringio'
require 'strscan'
require 'rbconfig'

module Sass
  # The root directory of the Sass source tree.
  # This may be overridden by the package manager
  # if the lib directory is separated from the main source tree.
  # @api public
  ROOT_DIR = File.expand_path(File.join(__FILE__, "../../.."))
end
require 'set'

module Sass
  module Util
    # A map from sets to values.
    # A value is \{#\[]= set} by providing a set (the "set-set") and a value,
    # which is then recorded as corresponding to that set.
    # Values are \{#\[] accessed} by providing a set (the "get-set")
    # and returning all values that correspond to set-sets
    # that are subsets of the get-set.
    #
    # SubsetMap preserves the order of values as they're inserted.
    #
    # @example
    #   ssm = SubsetMap.new
    #   ssm[Set[1, 2]] = "Foo"
    #   ssm[Set[2, 3]] = "Bar"
    #   ssm[Set[1, 2, 3]] = "Baz"
    #
    #   ssm[Set[1, 2, 3]] #=> ["Foo", "Bar", "Baz"]
    class SubsetMap
      # Creates a new, empty SubsetMap.
      def initialize
        @hash = {}
        @vals = []
      end

      # Whether or not this SubsetMap has any key-value pairs.
      #
      # @return [Boolean]
      def empty?
        @hash.empty?
      end

      # Associates a value with a set.
      # When `set` or any of its supersets is accessed,
      # `value` will be among the values returned.
      #
      # Note that if the same `set` is passed to this method multiple times,
      # all given `value`s will be associated with that `set`.
      #
      # This runs in `O(n)` time, where `n` is the size of `set`.
      #
      # @param set [#to_set] The set to use as the map key. May not be empty.
      # @param value [Object] The value to associate with `set`.
      # @raise [ArgumentError] If `set` is empty.
      def []=(set, value)
        raise ArgumentError.new("SubsetMap keys may not be empty.") if set.empty?

        index = @vals.size
        @vals << value
        set.each do |k|
          @hash[k] ||= []
          @hash[k] << [set, set.to_set, index]
        end
      end

      # Returns all values associated with subsets of `set`.
      #
      # In the worst case, this runs in `O(m*max(n, log m))` time,
      # where `n` is the size of `set`
      # and `m` is the number of assocations in the map.
      # However, unless many keys in the map overlap with `set`,
      # `m` will typically be much smaller.
      #
      # @param set [Set] The set to use as the map key.
      # @return [Array<(Object, #to_set)>] An array of pairs,
      #   where the first value is the value associated with a subset of `set`,
      #   and the second value is that subset of `set`
      #   (or whatever `#to_set` object was used to set the value)
      #   This array is in insertion order.
      # @see #[]
      def get(set)
        res = set.map do |k|
          next unless subsets = @hash[k]
          subsets.map do |subenum, subset, index|
            next unless subset.subset?(set)
            [index, subenum]
          end
        end
        res = Sass::Util.flatten(res, 1)
        res.compact!
        res.uniq!
        res.sort!
        res.map! {|i, s| [@vals[i], s]}
        return res
      end

      # Same as \{#get}, but doesn't return the subsets of the argument
      # for which values were found.
      #
      # @param set [Set] The set to use as the map key.
      # @return [Array] The array of all values
      #   associated with subsets of `set`, in insertion order.
      # @see #get
      def [](set)
        get(set).map {|v, _| v}
      end
    end
  end
end

module Sass
  # A module containing various useful functions.
  module Util
    extend self

    # An array of ints representing the Ruby version number.
    # @api public
    RUBY_VERSION = ::RUBY_VERSION.split(".").map {|s| s.to_i}

    # The Ruby engine we're running under. Defaults to `"ruby"`
    # if the top-level constant is undefined.
    # @api public
    RUBY_ENGINE = defined?(::RUBY_ENGINE) ? ::RUBY_ENGINE : "ruby"

    # Returns the path of a file relative to the Sass root directory.
    #
    # @param file [String] The filename relative to the Sass root
    # @return [String] The filename relative to the the working directory
    def scope(file)
      File.join(Sass::ROOT_DIR, file)
    end

    # Converts an array of `[key, value]` pairs to a hash.
    #
    # @example
    #   to_hash([[:foo, "bar"], [:baz, "bang"]])
    #     #=> {:foo => "bar", :baz => "bang"}
    # @param arr [Array<(Object, Object)>] An array of pairs
    # @return [Hash] A hash
    def to_hash(arr)
      Hash[arr.compact]
    end

    # Maps the keys in a hash according to a block.
    #
    # @example
    #   map_keys({:foo => "bar", :baz => "bang"}) {|k| k.to_s}
    #     #=> {"foo" => "bar", "baz" => "bang"}
    # @param hash [Hash] The hash to map
    # @yield [key] A block in which the keys are transformed
    # @yieldparam key [Object] The key that should be mapped
    # @yieldreturn [Object] The new value for the key
    # @return [Hash] The mapped hash
    # @see #map_vals
    # @see #map_hash
    def map_keys(hash)
      to_hash(hash.map {|k, v| [yield(k), v]})
    end

    # Maps the values in a hash according to a block.
    #
    # @example
    #   map_values({:foo => "bar", :baz => "bang"}) {|v| v.to_sym}
    #     #=> {:foo => :bar, :baz => :bang}
    # @param hash [Hash] The hash to map
    # @yield [value] A block in which the values are transformed
    # @yieldparam value [Object] The value that should be mapped
    # @yieldreturn [Object] The new value for the value
    # @return [Hash] The mapped hash
    # @see #map_keys
    # @see #map_hash
    def map_vals(hash)
      to_hash(hash.map {|k, v| [k, yield(v)]})
    end

    # Maps the key-value pairs of a hash according to a block.
    #
    # @example
    #   map_hash({:foo => "bar", :baz => "bang"}) {|k, v| [k.to_s, v.to_sym]}
    #     #=> {"foo" => :bar, "baz" => :bang}
    # @param hash [Hash] The hash to map
    # @yield [key, value] A block in which the key-value pairs are transformed
    # @yieldparam [key] The hash key
    # @yieldparam [value] The hash value
    # @yieldreturn [(Object, Object)] The new value for the `[key, value]` pair
    # @return [Hash] The mapped hash
    # @see #map_keys
    # @see #map_vals
    def map_hash(hash, &block)
      to_hash(hash.map(&block))
    end

    # Computes the powerset of the given array.
    # This is the set of all subsets of the array.
    #
    # @example
    #   powerset([1, 2, 3]) #=>
    #     Set[Set[], Set[1], Set[2], Set[3], Set[1, 2], Set[2, 3], Set[1, 3], Set[1, 2, 3]]
    # @param arr [Enumerable]
    # @return [Set<Set>] The subsets of `arr`
    def powerset(arr)
      arr.inject([Set.new].to_set) do |powerset, el|
        new_powerset = Set.new
        powerset.each do |subset|
          new_powerset << subset
          new_powerset << subset + [el]
        end
        new_powerset
      end
    end

    # Restricts a number to falling within a given range.
    # Returns the number if it falls within the range,
    # or the closest value in the range if it doesn't.
    #
    # @param value [Numeric]
    # @param range [Range<Numeric>]
    # @return [Numeric]
    def restrict(value, range)
      [[value, range.first].max, range.last].min
    end

    # Concatenates all strings that are adjacent in an array,
    # while leaving other elements as they are.
    #
    # @example
    #   merge_adjacent_strings([1, "foo", "bar", 2, "baz"])
    #     #=> [1, "foobar", 2, "baz"]
    # @param arr [Array]
    # @return [Array] The enumerable with strings merged
    def merge_adjacent_strings(arr)
      # Optimize for the common case of one element
      return arr if arr.size < 2
      arr.inject([]) do |a, e|
        if e.is_a?(String)
          if a.last.is_a?(String)
            a.last << e
          else
            a << e.dup
          end
        else
          a << e
        end
        a
      end
    end

    # Intersperses a value in an enumerable, as would be done with `Array#join`
    # but without concatenating the array together afterwards.
    #
    # @param enum [Enumerable]
    # @param val
    # @return [Array]
    def intersperse(enum, val)
      enum.inject([]) {|a, e| a << e << val}[0...-1]
    end

    # Substitutes a sub-array of one array with another sub-array.
    #
    # @param ary [Array] The array in which to make the substitution
    # @param from [Array] The sequence of elements to replace with `to`
    # @param to [Array] The sequence of elements to replace `from` with
    def substitute(ary, from, to)
      res = ary.dup
      i = 0
      while i < res.size
        if res[i...i+from.size] == from
          res[i...i+from.size] = to
        end
        i += 1
      end
      res
    end

    # Destructively strips whitespace from the beginning and end
    # of the first and last elements, respectively,
    # in the array (if those elements are strings).
    #
    # @param arr [Array]
    # @return [Array] `arr`
    def strip_string_array(arr)
      arr.first.lstrip! if arr.first.is_a?(String)
      arr.last.rstrip! if arr.last.is_a?(String)
      arr
    end

    # Return an array of all possible paths through the given arrays.
    #
    # @param arrs [Array<Array>]
    # @return [Array<Arrays>]
    #
    # @example
    #   paths([[1, 2], [3, 4], [5]]) #=>
    #     # [[1, 3, 5],
    #     #  [2, 3, 5],
    #     #  [1, 4, 5],
    #     #  [2, 4, 5]]
    def paths(arrs)
      arrs.inject([[]]) do |paths, arr|
        flatten(arr.map {|e| paths.map {|path| path + [e]}}, 1)
      end
    end

    # Computes a single longest common subsequence for `x` and `y`.
    # If there are more than one longest common subsequences,
    # the one returned is that which starts first in `x`.
    #
    # @param x [Array]
    # @param y [Array]
    # @yield [a, b] An optional block to use in place of a check for equality
    #   between elements of `x` and `y`.
    # @yieldreturn [Object, nil] If the two values register as equal,
    #   this will return the value to use in the LCS array.
    # @return [Array] The LCS
    def lcs(x, y, &block)
      x = [nil, *x]
      y = [nil, *y]
      block ||= proc {|a, b| a == b && a}
      lcs_backtrace(lcs_table(x, y, &block), x, y, x.size-1, y.size-1, &block)
    end

    # Returns information about the caller of the previous method.
    #
    # @param entry [String] An entry in the `#caller` list, or a similarly formatted string
    # @return [[String, Fixnum, (String, nil)]] An array containing the filename, line, and method name of the caller.
    #   The method name may be nil
    def caller_info(entry = caller[1])
      info = entry.scan(/^(.*?):(-?.*?)(?::.*`(.+)')?$/).first
      info[1] = info[1].to_i
      # This is added by Rubinius to designate a block, but we don't care about it.
      info[2].sub!(/ \{\}\Z/, '') if info[2]
      info
    end

    # Returns whether one version string represents a more recent version than another.
    #
    # @param v1 [String] A version string.
    # @param v2 [String] Another version string.
    # @return [Boolean]
    def version_gt(v1, v2)
      # Construct an array to make sure the shorter version is padded with nil
      Array.new([v1.length, v2.length].max).zip(v1.split("."), v2.split(".")) do |_, p1, p2|
        p1 ||= "0"
        p2 ||= "0"
        release1 = p1 =~ /^[0-9]+$/
        release2 = p2 =~ /^[0-9]+$/
        if release1 && release2
          # Integer comparison if both are full releases
          p1, p2 = p1.to_i, p2.to_i
          next if p1 == p2
          return p1 > p2
        elsif !release1 && !release2
          # String comparison if both are prereleases
          next if p1 == p2
          return p1 > p2
        else
          # If only one is a release, that one is newer
          return release1
        end
      end
    end

    # Returns whether one version string represents the same or a more
    # recent version than another.
    #
    # @param v1 [String] A version string.
    # @param v2 [String] Another version string.
    # @return [Boolean]
    def version_geq(v1, v2)
      version_gt(v1, v2) || !version_gt(v2, v1)
    end

    # Throws a NotImplementedError for an abstract method.
    #
    # @param obj [Object] `self`
    # @raise [NotImplementedError]
    def abstract(obj)
      raise NotImplementedError.new("#{obj.class} must implement ##{caller_info[2]}")
    end

    # Silence all output to STDERR within a block.
    #
    # @yield A block in which no output will be printed to STDERR
    def silence_warnings
      the_real_stderr, $stderr = $stderr, StringIO.new
      yield
    ensure
      $stderr = the_real_stderr
    end

    @@silence_warnings = false
    # Silences all Sass warnings within a block.
    #
    # @yield A block in which no Sass warnings will be printed
    def silence_sass_warnings
      old_silence_warnings = @@silence_warnings
      @@silence_warnings = true
      yield
    ensure
      @@silence_warnings = old_silence_warnings
    end

    # The same as `Kernel#warn`, but is silenced by \{#silence\_sass\_warnings}.
    #
    # @param msg [String]
    def sass_warn(msg)
      return if @@silence_warnings
      warn(msg)
    end

    ## Cross Rails Version Compatibility

    # Returns the root of the Rails application,
    # if this is running in a Rails context.
    # Returns `nil` if no such root is defined.
    #
    # @return [String, nil]
    def rails_root
      if defined?(::Rails.root)
        return ::Rails.root.to_s if ::Rails.root
        raise "ERROR: Rails.root is nil!"
      end
      return RAILS_ROOT.to_s if defined?(RAILS_ROOT)
      return nil
    end

    # Returns the environment of the Rails application,
    # if this is running in a Rails context.
    # Returns `nil` if no such environment is defined.
    #
    # @return [String, nil]
    def rails_env
      return ::Rails.env.to_s if defined?(::Rails.env)
      return RAILS_ENV.to_s if defined?(RAILS_ENV)
      return nil
    end

    # Returns whether this environment is using ActionPack
    # version 3.0.0 or greater.
    #
    # @return [Boolean]
    def ap_geq_3?
      ap_geq?("3.0.0.beta1")
    end

    # Returns whether this environment is using ActionPack
    # of a version greater than or equal to that specified.
    #
    # @param version [String] The string version number to check against.
    #   Should be greater than or equal to Rails 3,
    #   because otherwise ActionPack::VERSION isn't autoloaded
    # @return [Boolean]
    def ap_geq?(version)
      # The ActionPack module is always loaded automatically in Rails >= 3
      return false unless defined?(ActionPack) && defined?(ActionPack::VERSION) &&
        defined?(ActionPack::VERSION::STRING)

      version_geq(ActionPack::VERSION::STRING, version)
    end

    # Returns an ActionView::Template* class.
    # In pre-3.0 versions of Rails, most of these classes
    # were of the form `ActionView::TemplateFoo`,
    # while afterwards they were of the form `ActionView;:Template::Foo`.
    #
    # @param name [#to_s] The name of the class to get.
    #   For example, `:Error` will return `ActionView::TemplateError`
    #   or `ActionView::Template::Error`.
    def av_template_class(name)
      return ActionView.const_get("Template#{name}") if ActionView.const_defined?("Template#{name}")
      return ActionView::Template.const_get(name.to_s)
    end

    ## Cross-OS Compatibility

    # Whether or not this is running on Windows.
    #
    # @return [Boolean]
    def windows?
      RbConfig::CONFIG['host_os'] =~ /mswin|windows|mingw/i
    end

    # Whether or not this is running on IronRuby.
    #
    # @return [Boolean]
    def ironruby?
      RUBY_ENGINE == "ironruby"
    end

    ## Cross-Ruby-Version Compatibility

    # Whether or not this is running under Ruby 1.8 or lower.
    #
    # Note that IronRuby counts as Ruby 1.8,
    # because it doesn't support the Ruby 1.9 encoding API.
    #
    # @return [Boolean]
    def ruby1_8?
      # IronRuby says its version is 1.9, but doesn't support any of the encoding APIs.
      # We have to fall back to 1.8 behavior.
      ironruby? || (Sass::Util::RUBY_VERSION[0] == 1 && Sass::Util::RUBY_VERSION[1] < 9)
    end

    # Whether or not this is running under Ruby 1.8.6 or lower.
    # Note that lower versions are not officially supported.
    #
    # @return [Boolean]
    def ruby1_8_6?
      ruby1_8? && Sass::Util::RUBY_VERSION[2] < 7
    end

    # Checks that the encoding of a string is valid in Ruby 1.9
    # and cleans up potential encoding gotchas like the UTF-8 BOM.
    # If it's not, yields an error string describing the invalid character
    # and the line on which it occurrs.
    #
    # @param str [String] The string of which to check the encoding
    # @yield [msg] A block in which an encoding error can be raised.
    #   Only yields if there is an encoding error
    # @yieldparam msg [String] The error message to be raised
    # @return [String] `str`, potentially with encoding gotchas like BOMs removed
    def check_encoding(str)
      if ruby1_8?
        return str.gsub(/\A\xEF\xBB\xBF/, '') # Get rid of the UTF-8 BOM
      elsif str.valid_encoding?
        # Get rid of the Unicode BOM if possible
        if str.encoding.name =~ /^UTF-(8|16|32)(BE|LE)?$/
          return str.gsub(Regexp.new("\\A\uFEFF".encode(str.encoding.name)), '')
        else
          return str
        end
      end

      encoding = str.encoding
      newlines = Regexp.new("\r\n|\r|\n".encode(encoding).force_encoding("binary"))
      str.force_encoding("binary").split(newlines).each_with_index do |line, i|
        begin
          line.encode(encoding)
        rescue Encoding::UndefinedConversionError => e
          yield <<MSG.rstrip, i + 1
Invalid #{encoding.name} character #{e.error_char.dump}
MSG
        end
      end
      return str
    end

    # Like {\#check\_encoding}, but also checks for a `@charset` declaration
    # at the beginning of the file and uses that encoding if it exists.
    #
    # The Sass encoding rules are simple.
    # If a `@charset` declaration exists,
    # we assume that that's the original encoding of the document.
    # Otherwise, we use whatever encoding Ruby has.
    # Then we convert that to UTF-8 to process internally.
    # The UTF-8 end result is what's returned by this method.
    #
    # @param str [String] The string of which to check the encoding
    # @yield [msg] A block in which an encoding error can be raised.
    #   Only yields if there is an encoding error
    # @yieldparam msg [String] The error message to be raised
    # @return [(String, Encoding)] The original string encoded as UTF-8,
    #   and the source encoding of the string (or `nil` under Ruby 1.8)
    # @raise [Encoding::UndefinedConversionError] if the source encoding
    #   cannot be converted to UTF-8
    # @raise [ArgumentError] if the document uses an unknown encoding with `@charset`
    def check_sass_encoding(str, &block)
      return check_encoding(str, &block), nil if ruby1_8?
      # We allow any printable ASCII characters but double quotes in the charset decl
      bin = str.dup.force_encoding("BINARY")
      encoding = Sass::Util::ENCODINGS_TO_CHECK.find do |enc|
        bin =~ Sass::Util::CHARSET_REGEXPS[enc]
      end
      charset, bom = $1, $2
      if charset
        charset = charset.force_encoding(encoding).encode("UTF-8")
        if endianness = encoding[/[BL]E$/]
          begin
            Encoding.find(charset + endianness)
            charset << endianness
          rescue ArgumentError # Encoding charset + endianness doesn't exist
          end
        end
        str.force_encoding(charset)
      elsif bom
        str.force_encoding(encoding)
      end

      str = check_encoding(str, &block)
      return str.encode("UTF-8"), str.encoding
    end

    unless ruby1_8?
      # @private
      def _enc(string, encoding)
        string.encode(encoding).force_encoding("BINARY")
      end

      # We could automatically add in any non-ASCII-compatible encodings here,
      # but there's not really a good way to do that
      # without manually checking that each encoding
      # encodes all ASCII characters properly,
      # which takes long enough to affect the startup time of the CLI.
      ENCODINGS_TO_CHECK = %w[UTF-8 UTF-16BE UTF-16LE UTF-32BE UTF-32LE]

      CHARSET_REGEXPS = Hash.new do |h, e|
        h[e] =
          begin
            # /\A(?:\uFEFF)?@charset "(.*?)"|\A(\uFEFF)/
            Regexp.new(/\A(?:#{_enc("\uFEFF", e)})?#{
              _enc('@charset "', e)}(.*?)#{_enc('"', e)}|\A(#{
              _enc("\uFEFF", e)})/)
          rescue
            # /\A@charset "(.*?)"/
            Regexp.new(/\A#{_enc('@charset "', e)}(.*?)#{_enc('"', e)}/)
          end
      end
    end

    # Checks to see if a class has a given method.
    # For example:
    #
    #     Sass::Util.has?(:public_instance_method, String, :gsub) #=> true
    #
    # Method collections like `Class#instance_methods`
    # return strings in Ruby 1.8 and symbols in Ruby 1.9 and on,
    # so this handles checking for them in a compatible way.
    #
    # @param attr [#to_s] The (singular) name of the method-collection method
    #   (e.g. `:instance_methods`, `:private_methods`)
    # @param klass [Module] The class to check the methods of which to check
    # @param method [String, Symbol] The name of the method do check for
    # @return [Boolean] Whether or not the given collection has the given method
    def has?(attr, klass, method)
      klass.send("#{attr}s").include?(ruby1_8? ? method.to_s : method.to_sym)
    end

    # A version of `Enumerable#enum_with_index` that works in Ruby 1.8 and 1.9.
    #
    # @param enum [Enumerable] The enumerable to get the enumerator for
    # @return [Enumerator] The with-index enumerator
    def enum_with_index(enum)
      ruby1_8? ? enum.enum_with_index : enum.each_with_index
    end

    # A version of `Enumerable#enum_cons` that works in Ruby 1.8 and 1.9.
    #
    # @param enum [Enumerable] The enumerable to get the enumerator for
    # @param n [Fixnum] The size of each cons
    # @return [Enumerator] The consed enumerator
    def enum_cons(enum, n)
      ruby1_8? ? enum.enum_cons(n) : enum.each_cons(n)
    end

    # A version of `Enumerable#enum_slice` that works in Ruby 1.8 and 1.9.
    #
    # @param enum [Enumerable] The enumerable to get the enumerator for
    # @param n [Fixnum] The size of each slice
    # @return [Enumerator] The consed enumerator
    def enum_slice(enum, n)
      ruby1_8? ? enum.enum_slice(n) : enum.each_slice(n)
    end

    # Returns the ASCII code of the given character.
    #
    # @param c [String] All characters but the first are ignored.
    # @return [Fixnum] The ASCII code of `c`.
    def ord(c)
      ruby1_8? ? c[0] : c.ord
    end

    # Flattens the first `n` nested arrays in a cross-version manner.
    #
    # @param arr [Array] The array to flatten
    # @param n [Fixnum] The number of levels to flatten
    # @return [Array] The flattened array
    def flatten(arr, n)
      return arr.flatten(n) unless ruby1_8_6?
      return arr if n == 0
      arr.inject([]) {|res, e| e.is_a?(Array) ? res.concat(flatten(e, n - 1)) : res << e}
    end

    # Returns the hash code for a set in a cross-version manner.
    # Aggravatingly, this is order-dependent in Ruby 1.8.6.
    #
    # @param set [Set]
    # @return [Fixnum] The order-independent hashcode of `set`
    def set_hash(set)
      return set.hash unless ruby1_8_6?
      set.map {|e| e.hash}.uniq.sort.hash
    end

    # Tests the hash-equality of two sets in a cross-version manner.
    # Aggravatingly, this is order-dependent in Ruby 1.8.6.
    #
    # @param set1 [Set]
    # @param set2 [Set]
    # @return [Boolean] Whether or not the sets are hashcode equal
    def set_eql?(set1, set2)
      return set1.eql?(set2) unless ruby1_8_6?
      set1.to_a.uniq.sort_by {|e| e.hash}.eql?(set2.to_a.uniq.sort_by {|e| e.hash})
    end

    # Like `Object#inspect`, but preserves non-ASCII characters rather than escaping them under Ruby 1.9.2.
    # This is necessary so that the precompiled Haml template can be `#encode`d into `@options[:encoding]`
    # before being evaluated.
    #
    # @param obj {Object}
    # @return {String}
    def inspect_obj(obj)
      return obj.inspect unless version_geq(::RUBY_VERSION, "1.9.2")
      return ':' + inspect_obj(obj.to_s) if obj.is_a?(Symbol)
      return obj.inspect unless obj.is_a?(String)
      '"' + obj.gsub(/[\x00-\x7F]+/) {|s| s.inspect[1...-1]} + '"'
    end

    ## Static Method Stuff

    # The context in which the ERB for \{#def\_static\_method} will be run.
    class StaticConditionalContext
      # @param set [#include?] The set of variables that are defined for this context.
      def initialize(set)
        @set = set
      end

      # Checks whether or not a variable is defined for this context.
      #
      # @param name [Symbol] The name of the variable
      # @return [Boolean]
      def method_missing(name, *args, &block)
        super unless args.empty? && block.nil?
        @set.include?(name)
      end
    end

    private

    # Calculates the memoization table for the Least Common Subsequence algorithm.
    # Algorithm from [Wikipedia](http://en.wikipedia.org/wiki/Longest_common_subsequence_problem#Computing_the_length_of_the_LCS)
    def lcs_table(x, y)
      c = Array.new(x.size) {[]}
      x.size.times {|i| c[i][0] = 0}
      y.size.times {|j| c[0][j] = 0}
      (1...x.size).each do |i|
        (1...y.size).each do |j|
          c[i][j] =
            if yield x[i], y[j]
              c[i-1][j-1] + 1
            else
              [c[i][j-1], c[i-1][j]].max
            end
        end
      end
      return c
    end

    # Computes a single longest common subsequence for arrays x and y.
    # Algorithm from [Wikipedia](http://en.wikipedia.org/wiki/Longest_common_subsequence_problem#Reading_out_an_LCS)
    def lcs_backtrace(c, x, y, i, j, &block)
      return [] if i == 0 || j == 0
      if v = yield(x[i], y[j])
        return lcs_backtrace(c, x, y, i-1, j-1, &block) << v
      end

      return lcs_backtrace(c, x, y, i, j-1, &block) if c[i][j-1] > c[i-1][j]
      return lcs_backtrace(c, x, y, i-1, j, &block)
    end
  end
end

module Sass
  # Handles Sass version-reporting.
  # Sass not only reports the standard three version numbers,
  # but its Git revision hash as well,
  # if it was installed from Git.
  module Version
    include Sass::Util

    # Returns a hash representing the version of Sass.
    # The `:major`, `:minor`, and `:teeny` keys have their respective numbers as Fixnums.
    # The `:name` key has the name of the version.
    # The `:string` key contains a human-readable string representation of the version.
    # The `:number` key is the major, minor, and teeny keys separated by periods.
    # If Sass is checked out from Git, the `:rev` key will have the revision hash.
    # For example:
    #
    #     {
    #       :string => "2.1.0.9616393",
    #       :rev    => "9616393b8924ef36639c7e82aa88a51a24d16949",
    #       :number => "2.1.0",
    #       :major  => 2, :minor => 1, :teeny => 0
    #     }
    #
    # If a prerelease version of Sass is being used,
    # the `:string` and `:number` fields will reflect the full version
    # (e.g. `"2.2.beta.1"`), and the `:teeny` field will be `-1`.
    # A `:prerelease` key will contain the name of the prerelease (e.g. `"beta"`),
    # and a `:prerelease_number` key will contain the rerelease number.
    # For example:
    #
    #     {
    #       :string => "3.0.beta.1",
    #       :number => "3.0.beta.1",
    #       :major => 3, :minor => 0, :teeny => -1,
    #       :prerelease => "beta",
    #       :prerelease_number => 1
    #     }
    #
    # @return [{Symbol => String/Fixnum}] The version hash
    def version
      return @@version if defined?(@@version)


      #numbers = File.read(scope('VERSION')).strip.split('.').
      numbers = "3.2.0.alpha.0".strip.split('.').
        map {|n| n =~ /^[0-9]+$/ ? n.to_i : n}
      name = "Bleeding Edge"
      @@version = {
        :major => numbers[0],
        :minor => numbers[1],
        :teeny => numbers[2],
        :name => name
      }

      if numbers[3].is_a?(String)
        @@version[:teeny] = -1
        @@version[:prerelease] = numbers[3]
        @@version[:prerelease_number] = numbers[4]
      end

      @@version[:number] = numbers.join('.')
      @@version[:string] = @@version[:number].dup

      if rev = revision_number
        @@version[:rev] = rev
        unless rev[0] == ?(
          @@version[:string] << "." << rev[0...7]
        end
      end

      @@version[:string] << " (#{name})"
      @@version
    end

    private

    def revision_number
      if File.exists?(scope('REVISION'))
        rev = File.read(scope('REVISION')).strip
        return rev unless rev =~ /^([a-f0-9]+|\(.*\))$/ || rev == '(unknown)'
      end

      return unless File.exists?(scope('.git/HEAD'))
      rev = File.read(scope('.git/HEAD')).strip
      return rev unless rev =~ /^ref: (.*)$/

      ref_name = $1
      ref_file = scope(".git/#{ref_name}")
      info_file = scope(".git/info/refs")
      return File.read(ref_file).strip if File.exists?(ref_file)
      return unless File.exists?(info_file)
      File.open(info_file) do |f|
        f.each do |l|
          sha, ref = l.strip.split("\t", 2)
          next unless ref == ref_name
          return sha
        end
      end
      return nil
    end
  end

  extend Sass::Version

  # A string representing the version of Sass.
  # A more fine-grained representation is available from Sass.version.
  # @api public
  VERSION = version[:string] unless defined?(Sass::VERSION)
end

# The module that contains everything Sass-related:
#
# * {Sass::Engine} is the class used to render Sass/SCSS within Ruby code.
# * {Sass::Plugin} is interfaces with web frameworks (Rails and Merb in particular).
# * {Sass::SyntaxError} is raised when Sass encounters an error.
# * {Sass::CSS} handles conversion of CSS to Sass.
#
# Also see the {file:SASS_REFERENCE.md full Sass reference}.
module Sass
  # Compile a Sass or SCSS string to CSS.
  # Defaults to SCSS.
  #
  # @param contents [String] The contents of the Sass file.
  # @param options [{Symbol => Object}] An options hash;
  #   see {file:SASS_REFERENCE.md#sass_options the Sass options documentation}
  # @raise [Sass::SyntaxError] if there's an error in the document
  # @raise [Encoding::UndefinedConversionError] if the source encoding
  #   cannot be converted to UTF-8
  # @raise [ArgumentError] if the document uses an unknown encoding with `@charset`
  def self.compile(contents, options = {})
    options[:syntax] ||= :scss
    Engine.new(contents, options).to_css
  end

  # Compile a file on disk to CSS.
  #
  # @param filename [String] The path to the Sass, SCSS, or CSS file on disk.
  # @param options [{Symbol => Object}] An options hash;
  #   see {file:SASS_REFERENCE.md#sass_options the Sass options documentation}
  # @raise [Sass::SyntaxError] if there's an error in the document
  # @raise [Encoding::UndefinedConversionError] if the source encoding
  #   cannot be converted to UTF-8
  # @raise [ArgumentError] if the document uses an unknown encoding with `@charset`
  #
  # @overload compile_file(filename, options = {})
  #   Return the compiled CSS rather than writing it to a file.
  #
  #   @return [String] The compiled CSS.
  #
  # @overload compile_file(filename, css_filename, options = {})
  #   Write the compiled CSS to a file.
  #
  #   @param css_filename [String] The location to which to write the compiled CSS.
  def self.compile_file(filename, *args)
    options = args.last.is_a?(Hash) ? args.pop : {}
    css_filename = args.shift
    result = Sass::Engine.for_file(filename, options).render
    if css_filename
      options[:css_filename] ||= css_filename
      open(css_filename,"w") {|css_file| css_file.write(result)}
      nil
    else
      result
    end
  end
end


require 'strscan'
require 'set'
require 'digest/sha1'
require 'stringio'

module Sass
  # Sass cache stores are in charge of storing cached information,
  # especially parse trees for Sass documents.
  #
  # User-created importers must inherit from {CacheStores::Base}.
  module CacheStores
  end
end

module Sass
  module CacheStores
    # An abstract base class for backends for the Sass cache.
    # Any key-value store can act as such a backend;
    # it just needs to implement the
    # \{#_store} and \{#_retrieve} methods.
    #
    # To use a cache store with Sass,
    # use the {file:SASS_REFERENCE.md#cache_store-option `:cache_store` option}.
    #
    # @abstract
    class Base
      # Store cached contents for later retrieval
      # Must be implemented by all CacheStore subclasses
      #
      # Note: cache contents contain binary data.
      #
      # @param key [String] The key to store the contents under
      # @param version [String] The current sass version.
      #                Cached contents must not be retrieved across different versions of sass.
      # @param sha [String] The sha of the sass source.
      #                Cached contents must not be retrieved if the sha has changed.
      # @param contents [String] The contents to store.
      def _store(key, version, sha, contents)
        raise "#{self.class} must implement #_store."
      end

      # Retrieved cached contents.
      # Must be implemented by all subclasses.
      # 
      # Note: if the key exists but the sha or version have changed,
      # then the key may be deleted by the cache store, if it wants to do so.
      #
      # @param key [String] The key to retrieve
      # @param version [String] The current sass version.
      #                Cached contents must not be retrieved across different versions of sass.
      # @param sha [String] The sha of the sass source.
      #                Cached contents must not be retrieved if the sha has changed.
      # @return [String] The contents that were previously stored.
      # @return [NilClass] when the cache key is not found or the version or sha have changed.
      def _retrieve(key, version, sha)
        raise "#{self.class} must implement #_retrieve."
      end

      # Store a {Sass::Tree::RootNode}.
      #
      # @param key [String] The key to store it under.
      # @param sha [String] The checksum for the contents that are being stored.
      # @param obj [Object] The object to cache.
      def store(key, sha, root)
        _store(key, Sass::VERSION, sha, Marshal.dump(root))
      rescue TypeError, LoadError => e
        Sass::Util.sass_warn "Warning. Error encountered while saving cache #{path_to(key)}: #{e}"
      end

      # Retrieve a {Sass::Tree::RootNode}.
      #
      # @param key [String] The key the root element was stored under.
      # @param sha [String] The checksum of the root element's content.
      # @return [Object] The cached object.
      def retrieve(key, sha)
        contents = _retrieve(key, Sass::VERSION, sha)
        Marshal.load(contents) if contents
      rescue EOFError, TypeError, ArgumentError, LoadError => e
        Sass::Util.sass_warn "Warning. Error encountered while reading cache #{path_to(key)}: #{e}"
      end

      # Return the key for the sass file.
      #
      # The `(sass_dirname, sass_basename)` pair
      # should uniquely identify the Sass document,
      # but otherwise there are no restrictions on their content.
      #
      # @param sass_dirname [String]
      #   The fully-expanded location of the Sass file.
      #   This corresponds to the directory name on a filesystem.
      # @param sass_basename [String] The name of the Sass file that is being referenced.
      #   This corresponds to the basename on a filesystem.
      def key(sass_dirname, sass_basename)
        dir = Digest::SHA1.hexdigest(sass_dirname)
        filename = "#{sass_basename}c"
        "#{dir}/#{filename}"
      end
    end
  end
end
module Sass
  module CacheStores
    # A backend for the Sass cache using the filesystem.
    class Filesystem < Base
      # The directory where the cached files will be stored.
      #
      # @return [String]
      attr_accessor :cache_location

      # @param cache_location [String] see \{#cache\_location}
      def initialize(cache_location)
        @cache_location = cache_location
      end

      # @see Base#\_retrieve
      def _retrieve(key, version, sha)
        return unless File.readable?(path_to(key))
        contents = nil
        File.open(path_to(key), "rb") do |f|
          if f.readline("\n").strip == version && f.readline("\n").strip == sha
            return f.read
          end
        end
        File.unlink path_to(key)
        nil
      rescue EOFError, TypeError, ArgumentError => e
        Sass::Util.sass_warn "Warning. Error encountered while reading cache #{path_to(key)}: #{e}"
      end

      # @see Base#\_store
      def _store(key, version, sha, contents)
        # return unless File.writable?(File.dirname(@cache_location))
        # return if File.exists?(@cache_location) && !File.writable?(@cache_location)
        compiled_filename = path_to(key)
        # return if File.exists?(File.dirname(compiled_filename)) && !File.writable?(File.dirname(compiled_filename))
        # return if File.exists?(compiled_filename) && !File.writable?(compiled_filename)
        FileUtils.mkdir_p(File.dirname(compiled_filename))
        File.open(compiled_filename, "wb") do |f|
          f.puts(version)
          f.puts(sha)
          f.write(contents)
        end
      rescue Errno::EACCES
        #pass
      end

      private

      # Returns the path to a file for the given key.
      #
      # @param key [String]
      # @return [String] The path to the cache file.
      def path_to(key)
        File.join(cache_location, key)
      end
    end
  end
end
module Sass
  module CacheStores
    # A backend for the Sass cache using in-process memory.
    class Memory < Base
      # Since the {Memory} store is stored in the Sass tree's options hash,
      # when the options get serialized as part of serializing the tree,
      # you get crazy exponential growth in the size of the cached objects
      # unless you don't dump the cache.
      #
      # @private
      def _dump(depth)
        ""
      end

      # If we deserialize this class, just make a new empty one.
      #
      # @private
      def self._load(repr)
        Memory.new
      end

      # Create a new, empty cache store.
      def initialize
        @contents = {}
      end

      # @see Base#retrieve
      def retrieve(key, sha)
        if @contents.has_key?(key)
          return unless @contents[key][:sha] == sha
          obj = @contents[key][:obj]
          obj.respond_to?(:deep_copy) ? obj.deep_copy : obj.dup
        end
      end

      # @see Base#store
      def store(key, sha, obj)
        @contents[key] = {:sha => sha, :obj => obj}
      end
      
      # Destructively clear the cache.
      def reset!
        @contents = {}
      end
    end
  end
end
module Sass
  module CacheStores
    # A meta-cache that chains multiple caches together.
    # Specifically:
    #
    # * All `#store`s are passed to all caches.
    # * `#retrieve`s are passed to each cache until one has a hit.
    # * When one cache has a hit, the value is `#store`d in all earlier caches.
    class Chain < Base
      # Create a new cache chaining the given caches.
      #
      # @param caches [Array<Sass::CacheStores::Base>] The caches to chain.
      def initialize(*caches)
        @caches = caches
      end

      # @see Base#store
      def store(key, sha, obj)
        @caches.each {|c| c.store(key, sha, obj)}
      end

      # @see Base#retrieve
      def retrieve(key, sha)
        @caches.each_with_index do |c, i|
          next unless obj = c.retrieve(key, sha)
          @caches[0...i].each {|c| c.store(key, sha, obj)}
          return obj
        end
        nil
      end
    end
  end
end
module Sass
  # A namespace for nodes in the Sass parse tree.
  #
  # The Sass parse tree has three states: dynamic, static Sass, and static CSS.
  #
  # When it's first parsed, a Sass document is in the dynamic state.
  # It has nodes for mixin definitions and `@for` loops and so forth,
  # in addition to nodes for CSS rules and properties.
  # Nodes that only appear in this state are called **dynamic nodes**.
  #
  # {Tree::Visitors::Perform} creates a static Sass tree, which is different.
  # It still has nodes for CSS rules and properties
  # but it doesn't have any dynamic-generation-related nodes.
  # The nodes in this state are in the same structure as the Sass document:
  # rules and properties are nested beneath one another.
  # Nodes that can be in this state or in the dynamic state
  # are called **static nodes**.
  #
  # {Tree::Visitors::Cssize} is then used to create a static CSS tree.
  # This is like a static Sass tree,
  # but the structure exactly mirrors that of the generated CSS.
  # Rules and properties can't be nested beneath one another in this state.
  #
  # Finally, {Tree::Visitors::ToCss} can be called on a static CSS tree
  # to get the actual CSS code as a string.
  module Tree
    # The abstract superclass of all parse-tree nodes.
    class Node
      include Enumerable

      # The child nodes of this node.
      #
      # @return [Array<Tree::Node>]
      attr_accessor :children

      # Whether or not this node has child nodes.
      # This may be true even when \{#children} is empty,
      # in which case this node has an empty block (e.g. `{}`).
      #
      # @return [Boolean]
      attr_accessor :has_children

      # The line of the document on which this node appeared.
      #
      # @return [Fixnum]
      attr_accessor :line

      # The name of the document on which this node appeared.
      #
      # @return [String]
      attr_writer :filename

      # The options hash for the node.
      # See {file:SASS_REFERENCE.md#sass_options the Sass options documentation}.
      #
      # @return [{Symbol => Object}]
      attr_reader :options

      def initialize
        @children = []
      end

      # Sets the options hash for the node and all its children.
      #
      # @param options [{Symbol => Object}] The options
      # @see #options
      def options=(options)
        children.each {|c| c.options = options}
        @options = options
      end

      # @private
      def children=(children)
        self.has_children ||= !children.empty?
        @children = children
      end

      # The name of the document on which this node appeared.
      #
      # @return [String]
      def filename
        @filename || (@options && @options[:filename])
      end

      # Appends a child to the node.
      #
      # @param child [Tree::Node, Array<Tree::Node>] The child node or nodes
      # @raise [Sass::SyntaxError] if `child` is invalid
      def <<(child)
        return if child.nil?
        if child.is_a?(Array)
          child.each {|c| self << c}
        else
          self.has_children = true
          @children << child
        end
      end

      # Compares this node and another object (only other {Tree::Node}s will be equal).
      # This does a structural comparison;
      # if the contents of the nodes and all the child nodes are equivalent,
      # then the nodes are as well.
      #
      # Only static nodes need to override this.
      #
      # @param other [Object] The object to compare with
      # @return [Boolean] Whether or not this node and the other object
      #   are the same
      # @see Sass::Tree
      def ==(other)
        self.class == other.class && other.children == children
      end

      # True if \{#to\_s} will return `nil`;
      # that is, if the node shouldn't be rendered.
      # Should only be called in a static tree.
      #
      # @return [Boolean]
      def invisible?; false; end

      # The output style. See {file:SASS_REFERENCE.md#sass_options the Sass options documentation}.
      #
      # @return [Symbol]
      def style
        @options[:style]
      end

      # Computes the CSS corresponding to this static CSS tree.
      #
      # @return [String, nil] The resulting CSS
      # @see Sass::Tree
      def to_s
        Sass::Tree::Visitors::ToCss.visit(self)
      end

      # Converts a static CSS tree (e.g. the output of \{Tree::Visitors::Cssize})
      # into another static CSS tree,
      # with the given extensions applied to all relevant {RuleNode}s.
      #
      # @todo Link this to the reference documentation on `@extend`
      #   when such a thing exists.
      #
      # @param extends [Sass::Util::SubsetMap{Selector::Simple => Selector::Sequence}]
      #   The extensions to perform on this tree
      # @return [Tree::Node] The resulting tree of static CSS nodes.
      # @raise [Sass::SyntaxError] Only if there's a programmer error
      #   and this is not a static CSS tree
      def do_extend(extends)
        node = dup
        node.children = children.map {|c| c.do_extend(extends)}
        node
      rescue Sass::SyntaxError => e
        e.modify_backtrace(:filename => filename, :line => line)
        raise e
      end

      # Iterates through each node in the tree rooted at this node
      # in a pre-order walk.
      #
      # @yield node
      # @yieldparam node [Node] a node in the tree
      def each(&block)
        yield self
        children.each {|c| c.each(&block)}
      end

      # Converts a node to Sass code that will generate it.
      #
      # @param options [{Symbol => Object}] An options hash (see {Sass::CSS#initialize})
      # @return [String] The Sass code corresponding to the node
      def to_sass(options = {})
        Sass::Tree::Visitors::Convert.visit(self, options, :sass)
      end

      # Converts a node to SCSS code that will generate it.
      #
      # @param options [{Symbol => Object}] An options hash (see {Sass::CSS#initialize})
      # @return [String] The Sass code corresponding to the node
      def to_scss(options = {})
        Sass::Tree::Visitors::Convert.visit(self, options, :scss)
      end

      # Return a deep clone of this node.
      # The child nodes are cloned, but options are not.
      #
      # @return [Node]
      def deep_copy
        node = dup
        node.children = children.map {|c| c.deep_copy}
        node
      end

      protected

      # @see Sass::Shared.balance
      # @raise [Sass::SyntaxError] if the brackets aren't balanced
      def balance(*args)
        res = Sass::Shared.balance(*args)
        return res if res
        raise Sass::SyntaxError.new("Unbalanced brackets.", :line => line)
      end
    end
  end
end
module Sass
  module Tree
    # A static node that is the root node of the Sass document.
    class RootNode < Node
      # The Sass template from which this node was created
      #
      # @param template [String]
      attr_reader :template

      # @param template [String] The Sass template from which this node was created
      def initialize(template)
        super()
        @template = template
      end

      # Runs the dynamic Sass code *and* computes the CSS for the tree.
      # @see #to_s
      def render
        Visitors::CheckNesting.visit(self)
        result = Visitors::Perform.visit(self)
        Visitors::CheckNesting.visit(result) # Check again to validate mixins
        result, extends = Visitors::Cssize.visit(result)
        result = result.do_extend(extends) unless extends.empty?
        result.to_s
      end
    end
  end
end
require 'pathname'
require 'uri'

module Sass::Tree
  # A static node reprenting a CSS rule.
  #
  # @see Sass::Tree
  class RuleNode < Node
    # The character used to include the parent selector
    PARENT = '&'

    # The CSS selector for this rule,
    # interspersed with {Sass::Script::Node}s
    # representing `#{}`-interpolation.
    # Any adjacent strings will be merged together.
    #
    # @return [Array<String, Sass::Script::Node>]
    attr_accessor :rule

    # The CSS selector for this rule,
    # without any unresolved interpolation
    # but with parent references still intact.
    # It's only set once {Tree::Node#perform} has been called.
    #
    # @return [Selector::CommaSequence]
    attr_accessor :parsed_rules

    # The CSS selector for this rule,
    # without any unresolved interpolation or parent references.
    # It's only set once {Tree::Visitors::Cssize} has been run.
    #
    # @return [Selector::CommaSequence]
    attr_accessor :resolved_rules

    # How deep this rule is indented
    # relative to a base-level rule.
    # This is only greater than 0 in the case that:
    #
    # * This node is in a CSS tree
    # * The style is :nested
    # * This is a child rule of another rule
    # * The parent rule has properties, and thus will be rendered
    #
    # @return [Fixnum]
    attr_accessor :tabs

    # Whether or not this rule is the last rule in a nested group.
    # This is only set in a CSS tree.
    #
    # @return [Boolean]
    attr_accessor :group_end

    # @param rule [Array<String, Sass::Script::Node>]
    #   The CSS rule. See \{#rule}
    def initialize(rule)
      merged = Sass::Util.merge_adjacent_strings(rule)
      @rule = Sass::Util.strip_string_array(merged)
      @tabs = 0
      try_to_parse_non_interpolated_rules
      super()
    end

    # If we've precached the parsed selector, set the line on it, too.
    def line=(line)
      @parsed_rules.line = line if @parsed_rules
      super
    end

    # If we've precached the parsed selector, set the filename on it, too.
    def filename=(filename)
      @parsed_rules.filename = filename if @parsed_rules
      super
    end

    # Compares the contents of two rules.
    #
    # @param other [Object] The object to compare with
    # @return [Boolean] Whether or not this node and the other object
    #   are the same
    def ==(other)
      self.class == other.class && rule == other.rule && super
    end

    # Adds another {RuleNode}'s rules to this one's.
    #
    # @param node [RuleNode] The other node
    def add_rules(node)
      @rule = Sass::Util.strip_string_array(
        Sass::Util.merge_adjacent_strings(@rule + ["\n"] + node.rule))
      try_to_parse_non_interpolated_rules
    end

    # @return [Boolean] Whether or not this rule is continued on the next line
    def continued?
      last = @rule.last
      last.is_a?(String) && last[-1] == ?,
    end

    # Extends this Rule's selector with the given `extends`.
    #
    # @see Node#do_extend
    def do_extend(extends)
      node = dup
      node.resolved_rules = resolved_rules.do_extend(extends)
      node
    end

    # A hash that will be associated with this rule in the CSS document
    # if the {file:SASS_REFERENCE.md#debug_info-option `:debug_info` option} is enabled.
    # This data is used by e.g. [the FireSass Firebug extension](https://addons.mozilla.org/en-US/firefox/addon/103988).
    #
    # @return [{#to_s => #to_s}]
    def debug_info
      {:filename => filename && ("file://" + URI.escape(File.expand_path(filename))),
       :line => self.line}
    end

    private

    def try_to_parse_non_interpolated_rules
      if @rule.all? {|t| t.kind_of?(String)}
        # We don't use real filename/line info because we don't have it yet.
        # When we get it, we'll set it on the parsed rules if possible.
        parser = Sass::SCSS::StaticParser.new(@rule.join.strip, 1)
        @parsed_rules = parser.parse_selector('') rescue nil
      end
    end
  end
end

module Sass::Tree
  # A static node representing a Sass comment (silent or loud).
  #
  # @see Sass::Tree
  class CommentNode < Node
    # The text of the comment, not including `/*` and `*/`.
    #
    # @return [String]
    attr_accessor :value

    # Whether the comment is loud.
    #
    # Loud comments start with ! and force the comment to be generated
    # irrespective of compilation settings or the comment syntax used.
    #
    # @return [Boolean]
    attr_accessor :loud

    # Whether or not the comment is silent (that is, doesn't output to CSS).
    #
    # @return [Boolean]
    attr_accessor :silent

    # @param value [String] See \{#value}
    # @param silent [Boolean] See \{#silent}
    def initialize(value, silent)
      @lines = []
      @silent = silent
      @value = normalize_indentation value
      @loud = @value =~ %r{^(/[\/\*])?!}
      @value.sub!("#{$1}!", $1.to_s) if @loud
      super()
    end

    # Compares the contents of two comments.
    #
    # @param other [Object] The object to compare with
    # @return [Boolean] Whether or not this node and the other object
    #   are the same
    def ==(other)
      self.class == other.class && value == other.value && silent == other.silent
    end

    # Returns `true` if this is a silent comment
    # or the current style doesn't render comments.
    #
    # Comments starting with ! are never invisible (and the ! is removed from the output.)
    #
    # @return [Boolean]
    def invisible?
      if @loud
        return false
      else
        @silent || (style == :compressed)
      end
    end

    # Returns whether this comment should be interpolated for dynamic comment generation.
    def evaluated?
      @loud
    end

    private

    def normalize_indentation(str)
      pre = str.split("\n").inject(str[/^[ \t]*/].split("")) do |pre, line|
        line[/^[ \t]*/].split("").zip(pre).inject([]) do |arr, (a, b)|
          break arr if a != b
          arr + [a]
        end
      end.join
      str.gsub(/^#{pre}/, '')
    end
  end
end
module Sass::Tree
  # A static node reprenting a CSS property.
  #
  # @see Sass::Tree
  class PropNode < Node
    # The name of the property,
    # interspersed with {Sass::Script::Node}s
    # representing `#{}`-interpolation.
    # Any adjacent strings will be merged together.
    #
    # @return [Array<String, Sass::Script::Node>]
    attr_accessor :name

    # The name of the property
    # after any interpolated SassScript has been resolved.
    # Only set once \{Tree::Visitors::Perform} has been run.
    #
    # @return [String]
    attr_accessor :resolved_name

    # The value of the property.
    #
    # @return [Sass::Script::Node]
    attr_accessor :value

    # The value of the property
    # after any interpolated SassScript has been resolved.
    # Only set once \{Tree::Visitors::Perform} has been run.
    #
    # @return [String]
    attr_accessor :resolved_value

    # How deep this property is indented
    # relative to a normal property.
    # This is only greater than 0 in the case that:
    #
    # * This node is in a CSS tree
    # * The style is :nested
    # * This is a child property of another property
    # * The parent property has a value, and thus will be rendered
    #
    # @return [Fixnum]
    attr_accessor :tabs

    # @param name [Array<String, Sass::Script::Node>] See \{#name}
    # @param value [Sass::Script::Node] See \{#value}
    # @param prop_syntax [Symbol] `:new` if this property uses `a: b`-style syntax,
    #   `:old` if it uses `:a b`-style syntax
    def initialize(name, value, prop_syntax)
      @name = Sass::Util.strip_string_array(
        Sass::Util.merge_adjacent_strings(name))
      @value = value
      @tabs = 0
      @prop_syntax = prop_syntax
      super()
    end

    # Compares the names and values of two properties.
    #
    # @param other [Object] The object to compare with
    # @return [Boolean] Whether or not this node and the other object
    #   are the same
    def ==(other)
      self.class == other.class && name == other.name && value == other.value && super
    end

    # Returns a appropriate message indicating how to escape pseudo-class selectors.
    # This only applies for old-style properties with no value,
    # so returns the empty string if this is new-style.
    #
    # @return [String] The message
    def pseudo_class_selector_message
      return "" if @prop_syntax == :new || !value.is_a?(Sass::Script::String) || !value.value.empty?
      "\nIf #{declaration.dump} should be a selector, use \"\\#{declaration}\" instead."
    end

    # Computes the Sass or SCSS code for the variable declaration.
    # This is like \{#to\_scss} or \{#to\_sass},
    # except it doesn't print any child properties or a trailing semicolon.
    #
    # @param opts [{Symbol => Object}] The options hash for the tree.
    # @param fmt [Symbol] `:scss` or `:sass`.
    def declaration(opts = {:old => @prop_syntax == :old}, fmt = :sass)
      name = self.name.map {|n| n.is_a?(String) ? n : "\#{#{n.to_sass(opts)}}"}.join
      if name[0] == ?:
        raise Sass::SyntaxError.new("The \"#{name}: #{self.class.val_to_sass(value, opts)}\" hack is not allowed in the Sass indented syntax")
      end

      old = opts[:old] && fmt == :sass
      initial = old ? ':' : ''
      mid = old ? '' : ':'
      "#{initial}#{name}#{mid} #{self.class.val_to_sass(value, opts)}".rstrip
    end

    private

    def check!
      if @options[:property_syntax] && @options[:property_syntax] != @prop_syntax
        raise Sass::SyntaxError.new(
          "Illegal property syntax: can't use #{@prop_syntax} syntax when :property_syntax => #{@options[:property_syntax].inspect} is set.")
      elsif resolved_value.empty?
        raise Sass::SyntaxError.new("Invalid property: #{declaration.dump} (no value)." +
          pseudo_class_selector_message)
      end
    end

    class << self
      # @private
      def val_to_sass(value, opts)
        val_to_sass_comma(value, opts).to_sass(opts)
      end

      private

      def val_to_sass_comma(node, opts)
        return node unless node.is_a?(Sass::Script::Operation)
        return val_to_sass_concat(node, opts) unless node.operator == :comma

        Sass::Script::Operation.new(
          val_to_sass_concat(node.operand1, opts),
          val_to_sass_comma(node.operand2, opts),
          node.operator)
      end

      def val_to_sass_concat(node, opts)
        return node unless node.is_a?(Sass::Script::Operation)
        return val_to_sass_div(node, opts) unless node.operator == :space

        Sass::Script::Operation.new(
          val_to_sass_div(node.operand1, opts),
          val_to_sass_concat(node.operand2, opts),
          node.operator)
      end

      def val_to_sass_div(node, opts)
        unless node.is_a?(Sass::Script::Operation) && node.operator == :div &&
            node.operand1.is_a?(Sass::Script::Number) &&
            node.operand2.is_a?(Sass::Script::Number) &&
            (!node.operand1.original || !node.operand2.original)
          return node
        end

        Sass::Script::String.new("(#{node.to_sass(opts)})")
      end

    end
  end
end
module Sass::Tree
  # A static node representing an unproccessed Sass `@`-directive.
  # Directives known to Sass, like `@for` and `@debug`,
  # are handled by their own nodes;
  # only CSS directives like `@media` and `@font-face` become {DirectiveNode}s.
  #
  # `@import` and `@charset` are special cases;
  # they become {ImportNode}s and {CharsetNode}s, respectively.
  #
  # @see Sass::Tree
  class DirectiveNode < Node
    # The text of the directive, `@` and all.
    #
    # @return [String]
    attr_accessor :value

    # @param value [String] See \{#value}
    def initialize(value)
      @value = value
      super()
    end
  end
end
module Sass::Tree
  # A static node representing a `@media` rule.
  # `@media` rules behave differently from other directives
  # in that when they're nested within rules,
  # they bubble up to top-level.
  #
  # @see Sass::Tree
  class MediaNode < DirectiveNode
    # The media query (e.g. `print` or `screen`).
    #
    # @return [String]
    attr_accessor :query

    # @see RuleNode#tabs
    attr_accessor :tabs

    # @see RuleNode#group_end
    attr_accessor :group_end

    # @param query [String] See \{#query}
    def initialize(query)
      @query = query
      @tabs = 0
      super('')
    end

    # @see DirectiveNode#value
    def value
      "@media #{query}"
    end
  end
end
module Sass
  module Tree
    # A dynamic node representing a variable definition.
    #
    # @see Sass::Tree
    class VariableNode < Node
      # The name of the variable.
      # @return [String]
      attr_reader :name

      # The parse tree for the variable value.
      # @return [Script::Node]
      attr_reader :expr

      # Whether this is a guarded variable assignment (`!default`).
      # @return [Boolean]
      attr_reader :guarded

      # @param name [String] The name of the variable
      # @param expr [Script::Node] See \{#expr}
      # @param guarded [Boolean] See \{#guarded}
      def initialize(name, expr, guarded)
        @name = name
        @expr = expr
        @guarded = guarded
        super()
      end
    end
  end
end
module Sass
  module Tree
    # A dynamic node representing a mixin definition.
    #
    # @see Sass::Tree
    class MixinDefNode < Node
      # The mixin name.
      # @return [String]
      attr_reader :name

      # The arguments for the mixin.
      # Each element is a tuple containing the variable for argument
      # and the parse tree for the default value of the argument.
      #
      # @return [Array<(Script::Node, Script::Node)>]
      attr_reader :args

      # @param name [String] The mixin name
      # @param args [Array<(Script::Node, Script::Node)>] See \{#args}
      def initialize(name, args)
        @name = name
        @args = args
        super()
      end
    end
  end
end

module Sass::Tree
  # A static node representing a mixin include.
  # When in a static tree, the sole purpose is to wrap exceptions
  # to add the mixin to the backtrace.
  #
  # @see Sass::Tree
  class MixinNode < Node
    # The name of the mixin.
    # @return [String]
    attr_reader :name

    # The arguments to the mixin.
    # @return [Array<Script::Node>]
    attr_reader :args

    # A hash from keyword argument names to values.
    # @return [{String => Script::Node}]
    attr_reader :keywords

    # @param name [String] The name of the mixin
    # @param args [Array<Script::Node>] See \{#args}
    # @param keywords [{String => Script::Node}] See \{#keywords}
    def initialize(name, args, keywords)
      @name = name
      @args = args
      @keywords = keywords
      super()
    end
  end
end
module Sass
  module Tree
    # A dynamic node representing a function definition.
    #
    # @see Sass::Tree
    class FunctionNode < Node
      # The name of the function.
      # @return [String]
      attr_reader :name

      # The arguments to the function. Each element is a tuple
      # containing the variable for argument and the parse tree for
      # the default value of the argument
      #
      # @return [Array<Script::Node>]
      attr_reader :args

      # @param name [String] The function name
      # @param args [Array<(Script::Node, Script::Node)>] The arguments for the function.
      def initialize(name, args)
        @name = name
        @args = args
        super()
      end
    end
  end
end
module Sass
  module Tree
    # A dynamic node representing returning from a function.
    #
    # @see Sass::Tree
    class ReturnNode < Node
      # The expression to return.
      # @type [Script::Node]
      attr_reader :expr

      # @param expr [Script::Node] The expression to return
      def initialize(expr)
        @expr = expr
        super()
      end
    end
  end
end

module Sass::Tree
  # A static node reprenting an `@extend` directive.
  #
  # @see Sass::Tree
  class ExtendNode < Node
    # The parsed selector after interpolation has been resolved.
    # Only set once {Tree::Visitors::Perform} has been run.
    #
    # @return [Selector::CommaSequence]
    attr_accessor :resolved_selector

    # The CSS selector to extend, interspersed with {Sass::Script::Node}s
    # representing `#{}`-interpolation.
    #
    # @return [Array<String, Sass::Script::Node>]
    attr_reader :selector

    # @param selector [Array<String, Sass::Script::Node>]
    #   The CSS selector to extend,
    #   interspersed with {Sass::Script::Node}s
    #   representing `#{}`-interpolation.
    def initialize(selector)
      @selector = selector
      super()
    end
  end
end

module Sass::Tree
  # A dynamic node representing a Sass `@if` statement.
  #
  # {IfNode}s are a little odd, in that they also represent `@else` and `@else if`s.
  # This is done as a linked list:
  # each {IfNode} has a link (\{#else}) to the next {IfNode}.
  #
  # @see Sass::Tree
  class IfNode < Node
    # The conditional expression.
    # If this is nil, this is an `@else` node, not an `@else if`.
    #
    # @return [Script::Expr]
    attr_reader :expr

    # The next {IfNode} in the if-else list, or `nil`.
    #
    # @return [IfNode]
    attr_accessor :else

    # @param expr [Script::Expr] See \{#expr}
    def initialize(expr)
      @expr = expr
      @last_else = self
      super()
    end

    # Append an `@else` node to the end of the list.
    #
    # @param node [IfNode] The `@else` node to append
    def add_else(node)
      @last_else.else = node
      @last_else = node
    end

    # @see Node#options=
    def options=(options)
      super
      self.else.options = options if self.else
    end

    def _dump(f)
      Marshal.dump([self.expr, self.else, self.children])
    end

    def self._load(data)
      expr, else_, children = Marshal.load(data)
      node = IfNode.new(expr)
      node.else = else_
      node.children = children
      node.instance_variable_set('@last_else',
        node.else ? node.else.instance_variable_get('@last_else') : node)
      node
    end

    # @see Node#deep_copy
    def deep_copy
      node = super
      node.else = self.else.deep_copy if self.else
      node
    end
  end
end

module Sass::Tree
  # A dynamic node representing a Sass `@while` loop.
  #
  # @see Sass::Tree
  class WhileNode < Node
    # The parse tree for the continuation expression.
    # @return [Script::Node]
    attr_reader :expr

    # @param expr [Script::Node] See \{#expr}
    def initialize(expr)
      @expr = expr
      super()
    end
  end
end

module Sass::Tree
  # A dynamic node representing a Sass `@for` loop.
  #
  # @see Sass::Tree
  class ForNode < Node
    # The name of the loop variable.
    # @return [String]
    attr_reader :var

    # The parse tree for the initial expression.
    # @return [Script::Node]
    attr_reader :from

    # The parse tree for the final expression.
    # @return [Script::Node]
    attr_reader :to

    # Whether to include `to` in the loop or stop just before.
    # @return [Boolean]
    attr_reader :exclusive

    # @param var [String] See \{#var}
    # @param from [Script::Node] See \{#from}
    # @param to [Script::Node] See \{#to}
    # @param exclusive [Boolean] See \{#exclusive}
    def initialize(var, from, to, exclusive)
      @var = var
      @from = from
      @to = to
      @exclusive = exclusive
      super()
    end
  end
end

module Sass::Tree
  # A dynamic node representing a Sass `@each` loop.
  #
  # @see Sass::Tree
  class EachNode < Node
    # The name of the loop variable.
    # @return [String]
    attr_reader :var

    # The parse tree for the list.
    # @param [Script::Node]
    attr_reader :list

    # @param var [String] The name of the loop variable
    # @param list [Script::Node] The parse tree for the list
    def initialize(var, list)
      @var = var
      @list = list
      super()
    end
  end
end
module Sass
  module Tree
    # A dynamic node representing a Sass `@debug` statement.
    #
    # @see Sass::Tree
    class DebugNode < Node
      # The expression to print.
      # @return [Script::Node] 
      attr_reader :expr

      # @param expr [Script::Node] The expression to print
      def initialize(expr)
        @expr = expr
        super()
      end
    end
  end
end
module Sass
  module Tree
    # A dynamic node representing a Sass `@warn` statement.
    #
    # @see Sass::Tree
    class WarnNode < Node
      # The expression to print.
      # @return [Script::Node]
      attr_reader :expr

      # @param expr [Script::Node] The expression to print
      def initialize(expr)
        @expr = expr
        super()
      end
    end
  end
end
module Sass
  module Tree
    # A static node that wraps the {Sass::Tree} for an `@import`ed file.
    # It doesn't have a functional purpose other than to add the `@import`ed file
    # to the backtrace if an error occurs.
    class ImportNode < RootNode
      # The name of the imported file as it appears in the Sass document.
      #
      # @return [String]
      attr_reader :imported_filename

      # @param imported_filename [String] The name of the imported file
      def initialize(imported_filename)
        @imported_filename = imported_filename
        super(nil)
      end

      def invisible?; to_s.empty?; end

      # Returns the imported file.
      #
      # @return [Sass::Engine]
      # @raise [Sass::SyntaxError] If no file could be found to import.
      def imported_file
        @imported_file ||= import
      end

      # Returns whether or not this import should emit a CSS @import declaration
      #
      # @return [Boolean] Whether or not this is a simple CSS @import declaration.
      def css_import?
        if @imported_filename =~ /\.css$/
          @imported_filename
        elsif imported_file.is_a?(String) && imported_file =~ /\.css$/
          imported_file
        end
      end

      private

      def import
        paths = @options[:load_paths]

        if @options[:importer]
          f = @options[:importer].find_relative(
            @imported_filename, @options[:filename], @options.dup)
          return f if f
        end

        paths.each do |p|
          if f = p.find(@imported_filename, @options.dup)
            return f
          end
        end

        message = "File to import not found or unreadable: #{@imported_filename}.\n"
        if paths.size == 1
          message << "Load path: #{paths.first}"
        else
          message << "Load paths:\n  " << paths.join("\n  ")
        end
        raise SyntaxError.new(message)
      rescue SyntaxError => e
        raise SyntaxError.new(e.message, :line => self.line, :filename => @filename)
      end
    end
  end
end
module Sass::Tree
  # A static node representing an unproccessed Sass `@charset` directive.
  #
  # @see Sass::Tree
  class CharsetNode < Node
    # The name of the charset.
    #
    # @return [String]
    attr_accessor :name

    # @param name [String] see \{#name}
    def initialize(name)
      @name = name
      super()
    end

    # @see Node#invisible?
    def invisible?
      !Sass::Util.ruby1_8?
    end
  end
end
# Visitors are used to traverse the Sass parse tree.
# Visitors should extend {Visitors::Base},
# which provides a small amount of scaffolding for traversal.
module Sass::Tree::Visitors
  # The abstract base class for Sass visitors.
  # Visitors should extend this class,
  # then implement `visit_*` methods for each node they care about
  # (e.g. `visit_rule` for {RuleNode} or `visit_for` for {ForNode}).
  # These methods take the node in question as argument.
  # They may `yield` to visit the child nodes of the current node.
  #
  # *Note*: due to the unusual nature of {Sass::Tree::IfNode},
  # special care must be taken to ensure that it is properly handled.
  # In particular, there is no built-in scaffolding
  # for dealing with the return value of `@else` nodes.
  #
  # @abstract
  class Base
    # Runs the visitor on a tree.
    #
    # @param root [Tree::Node] The root node of the Sass tree.
    # @return [Object] The return value of \{#visit} for the root node.
    def self.visit(root)
      new.send(:visit, root)
    end

    protected

    # Runs the visitor on the given node.
    # This can be overridden by subclasses that need to do something for each node.
    #
    # @param node [Tree::Node] The node to visit.
    # @return [Object] The return value of the `visit_*` method for this node.
    def visit(node)
      method = "visit_#{node_name node}"
      if self.respond_to?(method)
        self.send(method, node) {visit_children(node)}
      else
        visit_children(node)
      end
    end

    # Visit the child nodes for a given node.
    # This can be overridden by subclasses that need to do something
    # with the child nodes' return values.
    #
    # This method is run when `visit_*` methods `yield`,
    # and its return value is returned from the `yield`.
    #
    # @param parent [Tree::Node] The parent node of the children to visit.
    # @return [Array<Object>] The return values of the `visit_*` methods for the children.
    def visit_children(parent)
      parent.children.map {|c| visit(c)}
    end

    NODE_NAME_RE = /.*::(.*?)Node$/

    # Returns the name of a node as used in the `visit_*` method.
    #
    # @param [Tree::Node] node The node.
    # @return [String] The name.
    def node_name(node)
      @@node_names ||= {}
      @@node_names[node.class.name] ||= node.class.name.gsub(NODE_NAME_RE, '\\1').downcase
    end

    # `yield`s, then runs the visitor on the `@else` clause if the node has one.
    # This exists to ensure that the contents of the `@else` clause get visited.
    def visit_if(node)
      yield
      visit(node.else) if node.else
      node
    end
  end
end
# A visitor for converting a dynamic Sass tree into a static Sass tree.
class Sass::Tree::Visitors::Perform < Sass::Tree::Visitors::Base
  # @param root [Tree::Node] The root node of the tree to visit.
  # @param environment [Sass::Environment] The lexical environment.
  # @return [Tree::Node] The resulting tree of static nodes.
  def self.visit(root, environment = Sass::Environment.new)
    new(environment).send(:visit, root)
  end

  protected

  def initialize(env)
    @environment = env
  end

  # If an exception is raised, this add proper metadata to the backtrace.
  def visit(node)
    super(node.dup)
  rescue Sass::SyntaxError => e
    e.modify_backtrace(:filename => node.filename, :line => node.line)
    raise e
  end

  # Keeps track of the current environment.
  def visit_children(parent)
    with_environment Sass::Environment.new(@environment) do
      parent.children = super.flatten
      parent
    end
  end

  # Runs a block of code with the current environment replaced with the given one.
  #
  # @param env [Sass::Environment] The new environment for the duration of the block.
  # @yield A block in which the environment is set to `env`.
  # @return [Object] The return value of the block.
  def with_environment(env)
    old_env, @environment = @environment, env
    yield
  ensure
    @environment = old_env
  end

  # Sets the options on the environment if this is the top-level root.
  def visit_root(node)
    @environment.options = node.options if @environment.options.nil? || @environment.options.empty?
    yield
  rescue Sass::SyntaxError => e
    e.sass_template ||= node.template
    raise e
  end

  # Removes this node from the tree if it's a silent comment.
  def visit_comment(node)
    return [] if node.invisible?
    if node.evaluated?
      node.value.gsub!(/(^|[^\\])\#\{([^}]*)\}/) do |md|
        $1+Sass::Script.parse($2, node.line, 0, node.options).perform(@environment).to_s
      end
      node.value = run_interp([Sass::Script::String.new(node.value)])
    end
    node
  end

  # Prints the expression to STDERR.
  def visit_debug(node)
    res = node.expr.perform(@environment)
    res = res.value if res.is_a?(Sass::Script::String)
    if node.filename
      $stderr.puts "#{node.filename}:#{node.line} DEBUG: #{res}"
    else
      $stderr.puts "Line #{node.line} DEBUG: #{res}"
    end
    []
  end

  # Runs the child nodes once for each value in the list.
  def visit_each(node)
    list = node.list.perform(@environment)

    with_environment Sass::Environment.new(@environment) do
      list.to_a.map do |v|
        @environment.set_local_var(node.var, v)
        node.children.map {|c| visit(c)}
      end.flatten
    end
  end

  # Runs SassScript interpolation in the selector,
  # and then parses the result into a {Sass::Selector::CommaSequence}.
  def visit_extend(node)
    parser = Sass::SCSS::CssParser.new(run_interp(node.selector), node.line)
    node.resolved_selector = parser.parse_selector(node.filename)
    node
  end

  # Runs the child nodes once for each time through the loop, varying the variable each time.
  def visit_for(node)
    from = node.from.perform(@environment)
    to = node.to.perform(@environment)
    from.assert_int!
    to.assert_int!

    to = to.coerce(from.numerator_units, from.denominator_units)
    range = Range.new(from.to_i, to.to_i, node.exclusive)

    with_environment Sass::Environment.new(@environment) do
      range.map do |i|
        @environment.set_local_var(node.var,
          Sass::Script::Number.new(i, from.numerator_units, from.denominator_units))
        node.children.map {|c| visit(c)}
      end.flatten
    end
  end

  # Loads the function into the environment.
  def visit_function(node)
    @environment.set_function(node.name,
      Sass::Callable.new(node.name, node.args, @environment, node.children))
    []
  end

  # Runs the child nodes if the conditional expression is true;
  # otherwise, tries the else nodes.
  def visit_if(node)
    if node.expr.nil? || node.expr.perform(@environment).to_bool
      yield
      node.children
    elsif node.else
      visit(node.else)
    else
      []
    end
  end

  # Returns a static DirectiveNode if this is importing a CSS file,
  # or parses and includes the imported Sass file.
  def visit_import(node)
    if path = node.css_import?
      return Sass::Tree::DirectiveNode.new("@import url(#{path})")
    end

    @environment.push_frame(:filename => node.filename, :line => node.line)
    root = node.imported_file.to_tree
    node.children = root.children.map {|c| visit(c)}.flatten
    node
  rescue Sass::SyntaxError => e
    e.modify_backtrace(:filename => node.imported_file.options[:filename])
    e.add_backtrace(:filename => node.filename, :line => node.line)
    raise e
  ensure
    @environment.pop_frame
  end

  # Loads a mixin into the environment.
  def visit_mixindef(node)
    @environment.set_mixin(node.name,
      Sass::Callable.new(node.name, node.args, @environment, node.children))
    []
  end

  # Runs a mixin.
  def visit_mixin(node)
    handle_include_loop!(node) if @environment.mixins_in_use.include?(node.name)

    original_env = @environment
    original_env.push_frame(:filename => node.filename, :line => node.line)
    original_env.prepare_frame(:mixin => node.name)
    raise Sass::SyntaxError.new("Undefined mixin '#{node.name}'.") unless mixin = @environment.mixin(node.name)

    passed_args = node.args.dup
    passed_keywords = node.keywords.dup

    raise Sass::SyntaxError.new(<<END.gsub("\n", "")) if mixin.args.size < passed_args.size
Mixin #{node.name} takes #{mixin.args.size} argument#{'s' if mixin.args.size != 1}
 but #{node.args.size} #{node.args.size == 1 ? 'was' : 'were'} passed.
END

    passed_keywords.each do |name, value|
      # TODO: Make this fast
      unless mixin.args.find {|(var, default)| var.underscored_name == name}
        raise Sass::SyntaxError.new("Mixin #{node.name} doesn't have an argument named $#{name}")
      end
    end

    environment = mixin.args.zip(passed_args).
      inject(Sass::Environment.new(mixin.environment)) do |env, ((var, default), value)|
      env.set_local_var(var.name,
        if value
          value.perform(@environment)
        elsif kv = passed_keywords[var.underscored_name]
          kv.perform(@environment)
        elsif default
          default.perform(env)
        end)
      raise Sass::SyntaxError.new("Mixin #{node.name} is missing parameter #{var.inspect}.") unless env.var(var.name)
      env
    end

    with_environment(environment) {node.children = mixin.tree.map {|c| visit(c)}.flatten}
    node
  rescue Sass::SyntaxError => e
    if original_env # Don't add backtrace info if this is an @include loop
      e.modify_backtrace(:mixin => node.name, :line => node.line)
      e.add_backtrace(:line => node.line)
    end
    raise e
  ensure
    original_env.pop_frame if original_env
  end

  # Runs any SassScript that may be embedded in a property.
  def visit_prop(node)
    node.resolved_name = run_interp(node.name)
    val = node.value.perform(@environment)
    node.resolved_value = val.to_s
    yield
  end

  # Returns the value of the expression.
  def visit_return(node)
    throw :_sass_return, node.expr.perform(@environment)
  end

  # Runs SassScript interpolation in the selector,
  # and then parses the result into a {Sass::Selector::CommaSequence}.
  def visit_rule(node)
    parser = Sass::SCSS::StaticParser.new(run_interp(node.rule), node.line)
    node.parsed_rules ||= parser.parse_selector(node.filename)
    yield
  end

  # Loads the new variable value into the environment.
  def visit_variable(node)
    return [] if node.guarded && !@environment.var(node.name).nil?
    val = node.expr.perform(@environment)
    @environment.set_var(node.name, val)
    []
  end

  # Prints the expression to STDERR with a stylesheet trace.
  def visit_warn(node)
    @environment.push_frame(:filename => node.filename, :line => node.line)
    res = node.expr.perform(@environment)
    res = res.value if res.is_a?(Sass::Script::String)
    msg = "WARNING: #{res}\n"
    @environment.stack.reverse.each_with_index do |entry, i|
      msg << "        #{i == 0 ? "on" : "from"} line #{entry[:line]}" <<
        " of #{entry[:filename] || "an unknown file"}"
      msg << ", in `#{entry[:mixin]}'" if entry[:mixin]
      msg << "\n"
    end
    Sass::Util.sass_warn msg
    []
  ensure
    @environment.pop_frame
  end

  # Runs the child nodes until the continuation expression becomes false.
  def visit_while(node)
    children = []
    with_environment Sass::Environment.new(@environment) do
      children += node.children.map {|c| visit(c)} while node.expr.perform(@environment).to_bool
    end
    children.flatten
  end

  def visit_directive(node)
    if node.value['#{']
      node.value = run_interp(Sass::Engine.parse_interp(node.value, node.line, 0, node.options))
    end
    yield
    node
  end

  private

  def run_interp(text)
    text.map do |r|
      next r if r.is_a?(String)
      val = r.perform(@environment)
      # Interpolated strings should never render with quotes
      next val.value if val.is_a?(Sass::Script::String)
      val.to_s
    end.join.strip
  end

  def handle_include_loop!(node)
    msg = "An @include loop has been found:"
    mixins = @environment.stack.map {|s| s[:mixin]}.compact
    if mixins.size == 2 && mixins[0] == mixins[1]
      raise Sass::SyntaxError.new("#{msg} #{node.name} includes itself")
    end

    mixins << node.name
    msg << "\n" << Sass::Util.enum_cons(mixins, 2).map do |m1, m2|
      "    #{m1} includes #{m2}"
    end.join("\n")
    raise Sass::SyntaxError.new(msg)
  end
end
# A visitor for converting a static Sass tree into a static CSS tree.
class Sass::Tree::Visitors::Cssize < Sass::Tree::Visitors::Base
  # @param root [Tree::Node] The root node of the tree to visit.
  # @return [(Tree::Node, Sass::Util::SubsetMap)] The resulting tree of static nodes
  #   *and* the extensions defined for this tree
  def self.visit(root); super; end

  protected

  # Returns the immediate parent of the current node.
  # @return [Tree::Node]
  attr_reader :parent

  def initialize
    @extends = Sass::Util::SubsetMap.new
  end

  # If an exception is raised, this adds proper metadata to the backtrace.
  def visit(node)
    super(node.dup)
  rescue Sass::SyntaxError => e
    e.modify_backtrace(:filename => node.filename, :line => node.line)
    raise e
  end

  # Keeps track of the current parent node.
  def visit_children(parent)
    with_parent parent do
      parent.children = super.flatten
      parent
    end
  end

  # Runs a block of code with the current parent node
  # replaced with the given node.
  #
  # @param parent [Tree::Node] The new parent for the duration of the block.
  # @yield A block in which the parent is set to `parent`.
  # @return [Object] The return value of the block.
  def with_parent(parent)
    old_parent, @parent = @parent, parent
    yield
  ensure
    @parent = old_parent
  end

  # In Ruby 1.8, ensures that there's only one `@charset` directive
  # and that it's at the top of the document.
  #
  # @return [(Tree::Node, Sass::Util::SubsetMap)] The resulting tree of static nodes
  #   *and* the extensions defined for this tree
  def visit_root(node)
    yield

    # In Ruby 1.9 we can make all @charset nodes invisible
    # and infer the final @charset from the encoding of the final string.
    if Sass::Util.ruby1_8? && parent.nil?
      charset = node.children.find {|c| c.is_a?(Sass::Tree::CharsetNode)}
      node.children.reject! {|c| c.is_a?(Sass::Tree::CharsetNode)}
      node.children.unshift charset if charset
    end

    return node, @extends
  rescue Sass::SyntaxError => e
    e.sass_template ||= node.template
    raise e
  end

  # Registers an extension in the `@extends` subset map.
  def visit_extend(node)
    node.resolved_selector.members.each do |seq|
      if seq.members.size > 1
        raise Sass::SyntaxError.new("Can't extend #{seq.to_a.join}: can't extend nested selectors")
      end

      sseq = seq.members.first
      if !sseq.is_a?(Sass::Selector::SimpleSequence)
        raise Sass::SyntaxError.new("Can't extend #{seq.to_a.join}: invalid selector")
      end

      sel = sseq.members
      parent.resolved_rules.members.each do |seq|
        if !seq.members.last.is_a?(Sass::Selector::SimpleSequence)
          raise Sass::SyntaxError.new("#{seq} can't extend: invalid selector")
        end

        @extends[sel] = seq
      end
    end

    []
  end

  # Modifies exception backtraces to include the imported file.
  def visit_import(node)
    # Don't use #visit_children to avoid adding the import node to the list of parents.
    node.children.map {|c| visit(c)}.flatten
  rescue Sass::SyntaxError => e
    e.modify_backtrace(:filename => node.children.first.filename)
    e.add_backtrace(:filename => node.filename, :line => node.line)
    raise e
  end

  # Bubbles the `@media` directive up through RuleNodes
  # and merges it with other `@media` directives.
  def visit_media(node)
    if parent.is_a?(Sass::Tree::RuleNode)
      new_rule = parent.dup
      new_rule.children = node.children
      node.children = with_parent(node) {Array(visit(new_rule))}
      # If the last child is actually the end of the group,
      # the parent's cssize will set it properly
      node.children.last.group_end = false unless node.children.empty?
    else
      yield
    end

    media = node.children.select {|c| c.is_a?(Sass::Tree::MediaNode)}
    node.children.reject! {|c| c.is_a?(Sass::Tree::MediaNode)}
    media.each {|n| n.query = "#{node.query} and #{n.query}"}
    (node.children.empty? ? [] : [node]) + media
  end

  # Asserts that all the mixin's children are valid in their new location.
  def visit_mixin(node)
    # Don't use #visit_children to avoid adding the mixin node to the list of parents.
    node.children.map {|c| visit(c)}.flatten
  rescue Sass::SyntaxError => e
    e.modify_backtrace(:mixin => node.name, :filename => node.filename, :line => node.line)
    e.add_backtrace(:filename => node.filename, :line => node.line)
    raise e
  end

  # Converts nested properties into flat properties
  # and updates the indentation of the prop node based on the nesting level.
  def visit_prop(node)
    if parent.is_a?(Sass::Tree::PropNode)
      node.resolved_name = "#{parent.resolved_name}-#{node.resolved_name}"
      node.tabs = parent.tabs + (parent.resolved_value.empty? ? 0 : 1) if node.style == :nested
    end

    yield

    result = node.children.dup
    if !node.resolved_value.empty? || node.children.empty?
      node.send(:check!)
      result.unshift(node)
    end

    result
  end

  # Resolves parent references and nested selectors,
  # and updates the indentation of the rule node based on the nesting level.
  def visit_rule(node)
    parent_resolved_rules = parent.is_a?(Sass::Tree::RuleNode) ? parent.resolved_rules : nil
    # It's possible for resolved_rules to be set if we've duplicated this node during @media bubbling
    node.resolved_rules ||= node.parsed_rules.resolve_parent_refs(parent_resolved_rules)

    yield

    rules = node.children.select {|c| c.is_a?(Sass::Tree::RuleNode) || c.is_a?(Sass::Tree::MediaNode)}
    props = node.children.reject {|c| c.is_a?(Sass::Tree::RuleNode) || c.is_a?(Sass::Tree::MediaNode) || c.invisible?}

    unless props.empty?
      node.children = props
      rules.each {|r| r.tabs += 1} if node.style == :nested
      rules.unshift(node)
    end

    rules.last.group_end = true unless parent.is_a?(Sass::Tree::RuleNode) || rules.empty?

    rules
  end
end
# A visitor for converting a Sass tree into a source string.
class Sass::Tree::Visitors::Convert < Sass::Tree::Visitors::Base
  # Runs the visitor on a tree.
  #
  # @param root [Tree::Node] The root node of the Sass tree.
  # @param options [{Symbol => Object}] An options hash (see {Sass::CSS#initialize}).
  # @param format [Symbol] `:sass` or `:scss`.
  # @return [String] The Sass or SCSS source for the tree.
  def self.visit(root, options, format)
    new(options, format).send(:visit, root)
  end

  protected

  def initialize(options, format)
    @options = options
    @format = format
    @tabs = 0
  end

  def visit_children(parent)
    @tabs += 1
    return @format == :sass ? "\n" : " {}\n" if parent.children.empty?
    (@format == :sass ? "\n" : " {\n") + super.join.rstrip + (@format == :sass ? "\n" : " }\n")
  ensure
    @tabs -= 1
  end

  # Ensures proper spacing between top-level nodes.
  def visit_root(node)
    Sass::Util.enum_cons(node.children + [nil], 2).map do |child, nxt|
      visit(child) +
        if nxt &&
            (child.is_a?(Sass::Tree::CommentNode) &&
              child.line + child.value.count("\n") + 1 == nxt.line) ||
            (child.is_a?(Sass::Tree::ImportNode) && nxt.is_a?(Sass::Tree::ImportNode) &&
              child.line + 1 == nxt.line) ||
            (child.is_a?(Sass::Tree::VariableNode) && nxt.is_a?(Sass::Tree::VariableNode) &&
              child.line + 1 == nxt.line)
          ""
        else
          "\n"
        end
    end.join.rstrip + "\n"
  end

  def visit_charset(node)
    "#{tab_str}@charset \"#{node.name}\"#{semi}\n"
  end

  def visit_comment(node)
    content = if @format == :sass
      content = node.value.gsub(/\*\/$/, '').rstrip
      if content =~ /\A[ \t]/
        # Re-indent SCSS comments like this:
        #     /* foo
        #   bar
        #       baz */
        content.gsub!(/^/, '   ')
        content.sub!(/\A([ \t]*)\/\*/, '/*\1')
      end

      content =
        unless content.include?("\n")
          content
        else
          content.gsub!(/\n( \*|\/\/)/, "\n  ")
          spaces = content.scan(/\n( *)/).map {|s| s.first.size}.min
          sep = node.silent ? "\n//" : "\n *"
          if spaces >= 2
            content.gsub(/\n  /, sep)
          else
            content.gsub(/\n#{' ' * spaces}/, sep)
          end
        end

      content.gsub!(/\A\/\*/, '//') if node.silent
      content.gsub!(/^/, tab_str)
      content.rstrip + "\n"
    else
      spaces = ('  ' * [@tabs - node.value[/^ */].size, 0].max)
      content = if node.silent
        node.value.gsub(/^[\/ ]\*/, '//').gsub(/ *\*\/$/, '')
      else
        node.value
      end.gsub(/^/, spaces) + "\n"
      content
    end
    if node.loud
      if node.silent
        content.gsub!(%r{^\s*(//!?)}, '//!')
      else
        content.sub!(%r{^\s*(/\*)}, '/*!')
      end
    end
    content
  end

  def visit_debug(node)
    "#{tab_str}@debug #{node.expr.to_sass(@options)}#{semi}\n"
  end

  def visit_directive(node)
    res = "#{tab_str}#{node.value}"
    return res + "#{semi}\n" unless node.has_children
    res + yield + "\n"
  end

  def visit_each(node)
    "#{tab_str}@each $#{dasherize(node.var)} in #{node.list.to_sass(@options)}#{yield}"
  end

  def visit_extend(node)
    "#{tab_str}@extend #{selector_to_src(node.selector).lstrip}#{semi}\n"
  end

  def visit_for(node)
    "#{tab_str}@for $#{dasherize(node.var)} from #{node.from.to_sass(@options)} " +
      "#{node.exclusive ? "to" : "through"} #{node.to.to_sass(@options)}#{yield}"
  end

  def visit_function(node)
    args = node.args.map do |v, d|
      d ? "#{v.to_sass(@options)}: #{d.to_sass(@options)}" : v.to_sass(@options)
    end.join(", ")

    "#{tab_str}@function #{dasherize(node.name)}(#{args})#{yield}"
  end

  def visit_if(node)
    name =
      if !@is_else; "if"
      elsif node.expr; "else if"
      else; "else"
      end
    str = "#{tab_str}@#{name}"
    str << " #{node.expr.to_sass(@options)}" if node.expr
    str << yield
    @is_else = true
    str << visit(node.else) if node.else
    str
  ensure
    @is_else = false
  end

  def visit_import(node)
    quote = @format == :scss ? '"' : ''
    "#{tab_str}@import #{quote}#{node.imported_filename}#{quote}#{semi}\n"
  end

  def visit_media(node)
    "#{tab_str}@media #{node.query}#{yield}"
  end

  def visit_mixindef(node)
    args =
      if node.args.empty?
        ""
      else
        '(' + node.args.map do |v, d|
          if d
            "#{v.to_sass(@options)}: #{d.to_sass(@options)}"
          else
            v.to_sass(@options)
          end
        end.join(", ") + ')'
      end
          
    "#{tab_str}#{@format == :sass ? '=' : '@mixin '}#{dasherize(node.name)}#{args}#{yield}"
  end

  def visit_mixin(node)
    unless node.args.empty? && node.keywords.empty?
      args = node.args.map {|a| a.to_sass(@options)}.join(", ")
      keywords = node.keywords.map {|k, v| "$#{dasherize(k)}: #{v.to_sass(@options)}"}.join(', ')
      arglist = "(#{args}#{', ' unless args.empty? || keywords.empty?}#{keywords})"
    end
    "#{tab_str}#{@format == :sass ? '+' : '@include '}#{dasherize(node.name)}#{arglist}#{semi}\n"
  end

  def visit_prop(node)
    res = tab_str + node.declaration(@options, @format)
    return res + semi + "\n" if node.children.empty?
    res + yield.rstrip + semi + "\n"
  end

  def visit_return(node)
    "#{tab_str}@return #{node.expr.to_sass(@options)}#{semi}\n"
  end

  def visit_rule(node)
    if @format == :sass
      name = selector_to_sass(node.rule)
      name = "\\" + name if name[0] == ?:
      name.gsub(/^/, tab_str) + yield
    elsif @format == :scss
      name = selector_to_scss(node.rule)
      res = name + yield
      if node.children.last.is_a?(Sass::Tree::CommentNode) && node.children.last.silent
        res.slice!(-3..-1)
        res << "\n" << tab_str << "}\n"
      end
      res
    end
  end

  def visit_variable(node)
    "#{tab_str}$#{dasherize(node.name)}: #{node.expr.to_sass(@options)}#{' !default' if node.guarded}#{semi}\n"
  end

  def visit_warn(node)
    "#{tab_str}@warn #{node.expr.to_sass(@options)}#{semi}\n"
  end

  def visit_while(node)
    "#{tab_str}@while #{node.expr.to_sass(@options)}#{yield}"
  end

  private

  def selector_to_src(sel)
    @format == :sass ? selector_to_sass(sel) : selector_to_scss(sel)
  end

  def selector_to_sass(sel)
    sel.map do |r|
      if r.is_a?(String)
        r.gsub(/(,[ \t]*)?\n\s*/) {$1 ? $1 + "\n" : " "}
      else
        "\#{#{r.to_sass(@options)}}"
      end
    end.join
  end

  def selector_to_scss(sel)
    sel.map {|r| r.is_a?(String) ? r : "\#{#{r.to_sass(@options)}}"}.
      join.gsub(/^[ \t]*/, tab_str)
  end

  def semi
    @format == :sass ? "" : ";"
  end

  def tab_str
    '  ' * @tabs
  end

  def dasherize(s)
    if @options[:dasherize]
      s.gsub('_', '-')
    else
      s
    end
  end
end
# A visitor for converting a Sass tree into CSS.
class Sass::Tree::Visitors::ToCss < Sass::Tree::Visitors::Base
  protected

  def initialize
    @tabs = 0
  end

  def visit(node)
    super
  rescue Sass::SyntaxError => e
    e.modify_backtrace(:filename => node.filename, :line => node.line)
    raise e
  end

  def with_tabs(tabs)
    old_tabs, @tabs = @tabs, tabs
    yield
  ensure
    @tabs = old_tabs
  end

  def visit_root(node)
    result = String.new
    node.children.each do |child|
      next if child.invisible?
      child_str = visit(child)
      result << child_str + (node.style == :compressed ? '' : "\n")
    end
    result.rstrip!
    return "" if result.empty?
    result << "\n"
    unless Sass::Util.ruby1_8? || result.ascii_only?
      if node.children.first.is_a?(Sass::Tree::CharsetNode)
        begin
          encoding = node.children.first.name
          # Default to big-endian encoding, because we have to decide somehow
          encoding << 'BE' if encoding =~ /\Autf-(16|32)\Z/i
          result = result.encode(Encoding.find(encoding))
        rescue EncodingError
        end
      end

      result = "@charset \"#{result.encoding.name}\";#{
        node.style == :compressed ? '' : "\n"
      }".encode(result.encoding) + result
    end
    result
  rescue Sass::SyntaxError => e
    e.sass_template ||= node.template
    raise e
  end

  def visit_charset(node)
    "@charset \"#{node.name}\";"
  end 

  def visit_comment(node)
    return if node.invisible?
    spaces = ('  ' * [@tabs - node.value[/^ */].size, 0].max)

    content = node.value.gsub(/^/, spaces).gsub(%r{^(\s*)//(.*)$}) do |md|
      "#{$1}/*#{$2} */"
    end
    if content =~ /[^\\]\#\{.*\}/
      Sass::Util.sass_warn <<MESSAGE
WARNING:
On line #{node.line}#{" of '#{node.filename}'" if node.filename}
Comments will evaluate the contents of interpolations (\#{ ... }) in Sass 3.2.
Please escape the interpolation by adding a backslash before the hash sign.
MESSAGE
    elsif content =~ /\\\#\{.*\}/
      content.gsub!(/\\(\#\{.*\})/, '\1')
    end
    content.gsub!(/\n +(\* *(?!\/))?/, ' ') if (node.style == :compact || node.style == :compressed) && !node.loud
    content
  end

  def visit_directive(node)
    return node.value + ";" unless node.has_children
    return node.value + " {}" if node.children.empty?
    result = if node.style == :compressed
               "#{node.value}{"
             else
               "#{'  ' * @tabs}#{node.value} {" + (node.style == :compact ? ' ' : "\n")
             end
    was_prop = false
    first = true
    node.children.each do |child|
      next if child.invisible?
      if node.style == :compact
        if child.is_a?(Sass::Tree::PropNode)
          with_tabs(first || was_prop ? 0 : @tabs + 1) {result << visit(child) << ' '}
        else
          result[-1] = "\n" if was_prop
          rendered = with_tabs(@tabs + 1) {visit(child).dup}
          rendered = rendered.lstrip if first
          result << rendered.rstrip + "\n"
        end
        was_prop = child.is_a?(Sass::Tree::PropNode)
        first = false
      elsif node.style == :compressed
        result << (was_prop ? ";" : "") << with_tabs(0) {visit(child)}
        was_prop = child.is_a?(Sass::Tree::PropNode)
      else
        result << with_tabs(@tabs + 1) {visit(child)} + "\n"
      end
    end
    result.rstrip + if node.style == :compressed
                      "}"
                    else
                      (node.style == :expanded ? "\n" : " ") + "}\n"
                    end
  end

  def visit_media(node)
    str = with_tabs(@tabs + node.tabs) {visit_directive(node)}
    str.gsub!(/\n\Z/, '') unless node.style == :compressed || node.group_end
    str
  end

  def visit_prop(node)
    tab_str = '  ' * (@tabs + node.tabs)
    if node.style == :compressed
      "#{tab_str}#{node.resolved_name}:#{node.resolved_value}"
    else
      "#{tab_str}#{node.resolved_name}: #{node.resolved_value};"
    end
  end

  def visit_rule(node)
    with_tabs(@tabs + node.tabs) do
      rule_separator = node.style == :compressed ? ',' : ', '
      line_separator =
        case node.style
          when :nested, :expanded; "\n"
          when :compressed; ""
          else; " "
        end
      rule_indent = '  ' * @tabs
      per_rule_indent, total_indent = [:nested, :expanded].include?(node.style) ? [rule_indent, ''] : ['', rule_indent]

      joined_rules = node.resolved_rules.members.map do |seq|
        rule_part = seq.to_a.join
        rule_part.gsub!(/\s*([^,])\s*\n\s*/m, '\1 ') if node.style == :compressed
        rule_part
      end.join(rule_separator)

      joined_rules.sub!(/\A\s*/, per_rule_indent)
      joined_rules.gsub!(/\s*\n\s*/, "#{line_separator}#{per_rule_indent}")
      total_rule = total_indent << joined_rules

      to_return = ''
      old_spaces = '  ' * @tabs
      spaces = '  ' * (@tabs + 1)
      if node.style != :compressed
        if node.options[:debug_info]
          to_return << visit(debug_info_rule(node.debug_info, node.options)) << "\n"
        elsif node.options[:line_comments]
          to_return << "#{old_spaces}/* line #{node.line}"

          if node.filename
            relative_filename = if node.options[:css_filename]
              begin
                Pathname.new(node.filename).relative_path_from(
                  Pathname.new(File.dirname(node.options[:css_filename]))).to_s
              rescue ArgumentError
                nil
              end
            end
            relative_filename ||= node.filename
            to_return << ", #{relative_filename}"
          end

          to_return << " */\n"
        end
      end

      if node.style == :compact
        properties = with_tabs(0) {node.children.map {|a| visit(a)}.join(' ')}
        to_return << "#{total_rule} { #{properties} }#{"\n" if node.group_end}"
      elsif node.style == :compressed
        properties = with_tabs(0) {node.children.map {|a| visit(a)}.join(';')}
        to_return << "#{total_rule}{#{properties}}"
      else
        properties = with_tabs(@tabs + 1) {node.children.map {|a| visit(a)}.join("\n")}
        end_props = (node.style == :expanded ? "\n" + old_spaces : ' ')
        to_return << "#{total_rule} {\n#{properties}#{end_props}}#{"\n" if node.group_end}"
      end

      to_return
    end
  end

  private

  def debug_info_rule(debug_info, options)
    node = Sass::Tree::DirectiveNode.new("@media -sass-debug-info")
    debug_info.map {|k, v| [k.to_s, v.to_s]}.sort.each do |k, v|
      rule = Sass::Tree::RuleNode.new([""])
      rule.resolved_rules = Sass::Selector::CommaSequence.new(
        [Sass::Selector::Sequence.new(
            [Sass::Selector::SimpleSequence.new(
                [Sass::Selector::Element.new(k.to_s.gsub(/[^\w-]/, "\\\\\\0"), nil)])
            ])
        ])
      prop = Sass::Tree::PropNode.new([""], "", :new)
      prop.resolved_name = "font-family"
      prop.resolved_value = Sass::SCSS::RX.escape_ident(v.to_s)
      rule << prop
      node << rule
    end
    node.options = options.merge(:debug_info => false, :line_comments => false, :style => :compressed)
    node
  end
end
# A visitor for checking that all nodes are properly nested.
class Sass::Tree::Visitors::CheckNesting < Sass::Tree::Visitors::Base
  protected

  def visit(node)
    if error = (@parent && (
          try_send("invalid_#{node_name @parent}_child?", @parent, node) ||
          try_send("invalid_#{node_name node}_parent?", @parent, node))) ||
        (@real_parent && (
          try_send("invalid_#{node_name @real_parent}_real_child?", @real_parent, node) ||
          try_send("invalid_#{node_name node}_real_parent?", @real_parent, node)))
      raise Sass::SyntaxError.new(error)
    end
    super
  rescue Sass::SyntaxError => e
    e.modify_backtrace(:filename => node.filename, :line => node.line)
    raise e
  end

  PARENT_CLASSES = [ Sass::Tree::EachNode,   Sass::Tree::ForNode,   Sass::Tree::IfNode,
                     Sass::Tree::ImportNode, Sass::Tree::MixinNode, Sass::Tree::WhileNode]
  def visit_children(parent)
    old_parent = @parent
    @parent = parent unless is_any_of?(parent, PARENT_CLASSES)
    old_real_parent, @real_parent = @real_parent, parent
    super
  ensure
    @parent = old_parent
    @real_parent = old_real_parent
  end

  def visit_root(node)
    yield
  rescue Sass::SyntaxError => e
    e.sass_template ||= node.template
    raise e
  end

  def visit_import(node)
    yield
  rescue Sass::SyntaxError => e
    e.modify_backtrace(:filename => node.children.first.filename)
    e.add_backtrace(:filename => node.filename, :line => node.line)
    raise e
  end

  def invalid_charset_parent?(parent, child)
    "@charset may only be used at the root of a document." unless parent.is_a?(Sass::Tree::RootNode)
  end

  INVALID_EXTEND_PARENTS = [Sass::Tree::RuleNode, Sass::Tree::MixinDefNode]
  def invalid_extend_parent?(parent, child)
    unless is_any_of?(parent, INVALID_EXTEND_PARENTS)
      "Extend directives may only be used within rules."
    end
  end

  def invalid_function_parent?(parent, child)
    "Functions may only be defined at the root of a document." unless parent.is_a?(Sass::Tree::RootNode)
  end

  INVALID_FUNCTION_CHILDREN = [
    Sass::Tree::CommentNode,  Sass::Tree::DebugNode, Sass::Tree::EachNode,
    Sass::Tree::ForNode,      Sass::Tree::IfNode,    Sass::Tree::ReturnNode,
    Sass::Tree::VariableNode, Sass::Tree::WarnNode,  Sass::Tree::WhileNode
  ]
  def invalid_function_child?(parent, child)
    unless is_any_of?(child, INVALID_FUNCTION_CHILDREN)
      "Functions can only contain variable declarations and control directives."
    end
  end

  INVALID_IMPORT_PARENTS = [
    Sass::Tree::IfNode,   Sass::Tree::ForNode, Sass::Tree::WhileNode,
    Sass::Tree::EachNode, Sass::Tree::MixinDefNode
  ]
  def invalid_import_parent?(parent, child)
    if is_any_of?(@real_parent, INVALID_IMPORT_PARENTS)
      return "Import directives may not be used within control directives or mixins."
    end
    return if parent.is_a?(Sass::Tree::RootNode)
    return "CSS import directives may only be used at the root of a document." if child.css_import?
    # If this is a nested @import, we need to make sure it doesn't have anything
    # that's legal at top-level but not in the current context (e.g. mixin defs).
    child.imported_file.to_tree.children.each {|c| visit(c)}
    nil
  rescue Sass::SyntaxError => e
    e.modify_backtrace(:filename => child.imported_file.options[:filename])
    e.add_backtrace(:filename => child.filename, :line => child.line)
    raise e
  end

  def invalid_import_real_parent?(parent, child)
    
  end

  def invalid_mixindef_parent?(parent, child)
    "Mixins may only be defined at the root of a document." unless parent.is_a?(Sass::Tree::RootNode)
  end

  INVALID_PROP_CHILDREN = [Sass::Tree::CommentNode, Sass::Tree::PropNode]
  def invalid_prop_child?(parent, child)
    unless is_any_of?(child, INVALID_PROP_CHILDREN)
      "Illegal nesting: Only properties may be nested beneath properties."
    end
  end

  INVALID_PROP_PARENTS = [Sass::Tree::RuleNode, Sass::Tree::PropNode,
                          Sass::Tree::MixinDefNode, Sass::Tree::DirectiveNode]
  def invalid_prop_parent?(parent, child)
    unless is_any_of?(parent, INVALID_PROP_PARENTS)
      "Properties are only allowed within rules, directives, or other properties." + child.pseudo_class_selector_message
    end
  end

  def invalid_return_parent?(parent, child)
    "@return may only be used within a function." unless parent.is_a?(Sass::Tree::FunctionNode)
  end

  private

  def is_any_of?(val, classes)
    for c in classes
      return true if val.is_a?(c)
    end
    return false
  end

  def try_send(method, *args, &block)
    return unless respond_to?(method)
    send(method, *args, &block)
  end
end

module Sass
  module Selector
    # The abstract superclass for simple selectors
    # (that is, those that don't compose multiple selectors).
    class Simple
      # The line of the Sass template on which this selector was declared.
      #
      # @return [Fixnum]
      attr_accessor :line

      # The name of the file in which this selector was declared,
      # or `nil` if it was not declared in a file (e.g. on stdin).
      #
      # @return [String, nil]
      attr_accessor :filename

      # Returns a representation of the node
      # as an array of strings and potentially {Sass::Script::Node}s
      # (if there's interpolation in the selector).
      # When the interpolation is resolved and the strings are joined together,
      # this will be the string representation of this node.
      #
      # @return [Array<String, Sass::Script::Node>]
      def to_a
        Sass::Util.abstract(self)
      end

      # Returns a string representation of the node.
      # This is basically the selector string.
      #
      # @return [String]
      def inspect
        to_a.map {|e| e.is_a?(Sass::Script::Node) ? "\#{#{e.to_sass}}" : e}.join
      end

      # Returns a hash code for this selector object.
      #
      # By default, this is based on the value of \{#to\_a},
      # so if that contains information irrelevant to the identity of the selector,
      # this should be overridden.
      #
      # @return [Fixnum]
      def hash
        @_hash ||= to_a.hash
      end

      # Checks equality between this and another object.
      #
      # By default, this is based on the value of \{#to\_a},
      # so if that contains information irrelevant to the identity of the selector,
      # this should be overridden.
      #
      # @param other [Object] The object to test equality against
      # @return [Boolean] Whether or not this is equal to `other`
      def eql?(other)
        other.class == self.class && other.hash == self.hash && other.to_a.eql?(to_a)
      end
      alias_method :==, :eql?

      # Unifies this selector with a {SimpleSequence}'s {SimpleSequence#members members array},
      # returning another `SimpleSequence` members array
      # that matches both this selector and the input selector.
      #
      # By default, this just appends this selector to the end of the array
      # (or returns the original array if this selector already exists in it).
      #
      # @param sels [Array<Simple>] A {SimpleSequence}'s {SimpleSequence#members members array}
      # @return [Array<Simple>, nil] A {SimpleSequence} {SimpleSequence#members members array}
      #   matching both `sels` and this selector,
      #   or `nil` if this is impossible (e.g. unifying `#foo` and `#bar`)
      # @raise [Sass::SyntaxError] If this selector cannot be unified.
      #   This will only ever occur when a dynamic selector,
      #   such as {Parent} or {Interpolation}, is used in unification.
      #   Since these selectors should be resolved
      #   by the time extension and unification happen,
      #   this exception will only ever be raised as a result of programmer error
      def unify(sels)
        return sels if sels.any? {|sel2| eql?(sel2)}
        sels_with_ix = Sass::Util.enum_with_index(sels)
        _, i =
          if self.is_a?(Pseudo) || self.is_a?(SelectorPseudoClass)
            sels_with_ix.find {|sel, _| sel.is_a?(Pseudo) && sels.last.type == :element}
          else
            sels_with_ix.find {|sel, _| sel.is_a?(Pseudo) || sel.is_a?(SelectorPseudoClass)}
          end
        return sels + [self] unless i
        return sels[0...i] + [self] + sels[i..-1]
      end

      protected

      # Unifies two namespaces,
      # returning a namespace that works for both of them if possible.
      #
      # @param ns1 [String, nil] The first namespace.
      #   `nil` means none specified, e.g. `foo`.
      #   The empty string means no namespace specified, e.g. `|foo`.
      #   `"*"` means any namespace is allowed, e.g. `*|foo`.
      # @param ns2 [String, nil] The second namespace. See `ns1`.
      # @return [Array(String or nil, Boolean)]
      #   The first value is the unified namespace, or `nil` for no namespace.
      #   The second value is whether or not a namespace that works for both inputs
      #   could be found at all.
      #   If the second value is `false`, the first should be ignored.
      def unify_namespaces(ns1, ns2)
        return nil, false unless ns1 == ns2 || ns1.nil? || ns1 == ['*'] || ns2.nil? || ns2 == ['*']
        return ns2, true if ns1 == ['*']
        return ns1, true if ns2 == ['*']
        return ns1 || ns2, true
      end
    end
  end
end
module Sass
  module Selector
    # The abstract parent class of the various selector sequence classes.
    #
    # All subclasses should implement a `members` method
    # that returns an array of object that respond to `#line=` and `#filename=`.
    class AbstractSequence
      # The line of the Sass template on which this selector was declared.
      #
      # @return [Fixnum]
      attr_reader :line

      # The name of the file in which this selector was declared.
      #
      # @return [String, nil]
      attr_reader :filename

      # Sets the line of the Sass template on which this selector was declared.
      # This also sets the line for all child selectors.
      #
      # @param line [Fixnum]
      # @return [Fixnum]
      def line=(line)
        members.each {|m| m.line = line}
        @line = line
      end

      # Sets the name of the file in which this selector was declared,
      # or `nil` if it was not declared in a file (e.g. on stdin).
      # This also sets the filename for all child selectors.
      #
      # @param filename [String, nil]
      # @return [String, nil]
      def filename=(filename)
        members.each {|m| m.filename = filename}
        @filename = filename
      end

      # Returns a hash code for this sequence.
      #
      # Subclasses should define `#_hash` rather than overriding this method,
      # which automatically handles memoizing the result.
      #
      # @return [Fixnum]
      def hash
        @_hash ||= _hash
      end

      # Checks equality between this and another object.
      #
      # Subclasses should define `#_eql?` rather than overriding this method,
      # which handles checking class equality and hash equality.
      #
      # @param other [Object] The object to test equality against
      # @return [Boolean] Whether or not this is equal to `other`
      def eql?(other)
        other.class == self.class && other.hash == self.hash && _eql?(other)
      end
      alias_method :==, :eql?
    end
  end
end
module Sass
  module Selector
    # A comma-separated sequence of selectors.
    class CommaSequence < AbstractSequence
      # The comma-separated selector sequences
      # represented by this class.
      #
      # @return [Array<Sequence>]
      attr_reader :members

      # @param seqs [Array<Sequence>] See \{#members}
      def initialize(seqs)
        @members = seqs
      end

      # Resolves the {Parent} selectors within this selector
      # by replacing them with the given parent selector,
      # handling commas appropriately.
      #
      # @param super_cseq [CommaSequence] The parent selector
      # @return [CommaSequence] This selector, with parent references resolved
      # @raise [Sass::SyntaxError] If a parent selector is invalid
      def resolve_parent_refs(super_cseq)
        if super_cseq.nil?
          if @members.any? do |sel|
              sel.members.any? do |sel_or_op|
                sel_or_op.is_a?(SimpleSequence) && sel_or_op.members.any? {|ssel| ssel.is_a?(Parent)}
              end
            end
            raise Sass::SyntaxError.new("Base-level rules cannot contain the parent-selector-referencing character '&'.")
          end
          return self
        end

        CommaSequence.new(
          super_cseq.members.map do |super_seq|
            @members.map {|seq| seq.resolve_parent_refs(super_seq)}
          end.flatten)
      end

      # Non-destrucively extends this selector with the extensions specified in a hash
      # (which should come from {Sass::Tree::Visitors::Cssize}).
      #
      # @todo Link this to the reference documentation on `@extend`
      #   when such a thing exists.
      #
      # @param extends [Sass::Util::SubsetMap{Selector::Simple => Selector::Sequence}]
      #   The extensions to perform on this selector
      # @return [CommaSequence] A copy of this selector,
      #   with extensions made according to `extends`
      def do_extend(extends)
        CommaSequence.new(members.map {|seq| seq.do_extend(extends)}.flatten)
      end

      # Returns a string representation of the sequence.
      # This is basically the selector string.
      #
      # @return [String]
      def inspect
        members.map {|m| m.inspect}.join(", ")
      end

      # @see Simple#to_a
      def to_a
        arr = Sass::Util.intersperse(@members.map {|m| m.to_a}, ", ").flatten
        arr.delete("\n")
        arr
      end

      private

      def _hash
        members.hash
      end

      def _eql?(other)
        other.class == self.class && other.members.eql?(self.members)
      end
    end
  end
end
module Sass
  module Selector
    # An operator-separated sequence of
    # {SimpleSequence simple selector sequences}.
    class Sequence < AbstractSequence
      # Sets the line of the Sass template on which this selector was declared.
      # This also sets the line for all child selectors.
      #
      # @param line [Fixnum]
      # @return [Fixnum]
      def line=(line)
        members.each {|m| m.line = line if m.is_a?(SimpleSequence)}
        line
      end

      # Sets the name of the file in which this selector was declared,
      # or `nil` if it was not declared in a file (e.g. on stdin).
      # This also sets the filename for all child selectors.
      #
      # @param filename [String, nil]
      # @return [String, nil]
      def filename=(filename)
        members.each {|m| m.filename = filename if m.is_a?(SimpleSequence)}
        filename
      end

      # The array of {SimpleSequence simple selector sequences}, operators, and newlines.
      # The operators are strings such as `"+"` and `">"`
      # representing the corresponding CSS operators.
      # Newlines are also newline strings;
      # these aren't semantically relevant,
      # but they do affect formatting.
      #
      # @return [Array<SimpleSequence, String>]
      attr_reader :members

      # @param seqs_and_ops [Array<SimpleSequence, String>] See \{#members}
      def initialize(seqs_and_ops)
        @members = seqs_and_ops
      end

      # Resolves the {Parent} selectors within this selector
      # by replacing them with the given parent selector,
      # handling commas appropriately.
      #
      # @param super_seq [Sequence] The parent selector sequence
      # @return [Sequence] This selector, with parent references resolved
      # @raise [Sass::SyntaxError] If a parent selector is invalid
      def resolve_parent_refs(super_seq)
        members = @members
        nl = (members.first == "\n" && members.shift)
        unless members.any? do |seq_or_op|
            seq_or_op.is_a?(SimpleSequence) && seq_or_op.members.first.is_a?(Parent)
          end
          members = []
          members << nl if nl
          members << SimpleSequence.new([Parent.new])
          members += @members
        end

        Sequence.new(
          members.map do |seq_or_op|
            next seq_or_op unless seq_or_op.is_a?(SimpleSequence)
            seq_or_op.resolve_parent_refs(super_seq)
          end.flatten)
      end

      # Non-destructively extends this selector with the extensions specified in a hash
      # (which should come from {Sass::Tree::Visitors::Cssize}).
      #
      # @overload def do_extend(extends)
      # @param extends [Sass::Util::SubsetMap{Selector::Simple => Selector::Sequence}]
      #   The extensions to perform on this selector
      # @return [Array<Sequence>] A list of selectors generated
      #   by extending this selector with `extends`.
      #   These correspond to a {CommaSequence}'s {CommaSequence#members members array}.
      # @see CommaSequence#do_extend
      def do_extend(extends, seen = Set.new)
        paths = Sass::Util.paths(members.map do |sseq_or_op|
            next [[sseq_or_op]] unless sseq_or_op.is_a?(SimpleSequence)
            extended = sseq_or_op.do_extend(extends, seen)
            choices = extended.map {|seq| seq.members}
            choices.unshift([sseq_or_op]) unless extended.any? {|seq| seq.superselector?(sseq_or_op)}
            choices
          end)
        Sass::Util.flatten(paths.map {|path| weave(path)}, 1).map {|p| Sequence.new(p)}
      end

      # Returns whether or not this selector matches all elements
      # that the given selector matches (as well as possibly more).
      #
      # @example
      #   (.foo).superselector?(.foo.bar) #=> true
      #   (.foo).superselector?(.bar) #=> false
      #   (.bar .foo).superselector?(.foo) #=> false
      # @param sseq [SimpleSequence]
      # @return [Boolean]
      def superselector?(sseq)
        return false unless members.size == 1
        members.last.superselector?(sseq)
      end

      # @see Simple#to_a
      def to_a
        ary = @members.map {|seq_or_op| seq_or_op.is_a?(SimpleSequence) ? seq_or_op.to_a : seq_or_op}
        Sass::Util.intersperse(ary, " ").flatten.compact
      end

      # Returns a string representation of the sequence.
      # This is basically the selector string.
      #
      # @return [String]
      def inspect
        members.map {|m| m.inspect}.join(" ")
      end

      private

      # Conceptually, this expands "parenthesized selectors".
      # That is, if we have `.A .B {@extend .C}` and `.D .C {...}`,
      # this conceptually expands into `.D .C, .D (.A .B)`,
      # and this function translates `.D (.A .B)` into `.D .A .B, .A.D .B, .D .A .B`.
      #
      # @param path [Array<Array<SimpleSequence or String>>] A list of parenthesized selector groups.
      # @return [Array<Array<SimpleSequence or String>>] A list of fully-expanded selectors.
      def weave(path)
        befores = [[]]
        afters = path.dup

        until afters.empty?
          current = afters.shift.dup
          last_current = [current.pop]
          while !current.empty? && last_current.first.is_a?(String) || current.last.is_a?(String)
            last_current.unshift(current.pop)
          end
          befores = Sass::Util.flatten(befores.map do |before|
              subweave(before, current).map {|seqs| seqs + last_current}
            end, 1)
          return befores if afters.empty?
        end
      end

      # This interweaves two lists of selectors,
      # returning all possible orderings of them (including using unification)
      # that maintain the relative ordering of the input arrays.
      #
      # For example, given `.foo .bar` and `.baz .bang`,
      # this would return `.foo .bar .baz .bang`, `.foo .bar.baz .bang`,
      # `.foo .baz .bar .bang`, `.foo .baz .bar.bang`, `.foo .baz .bang .bar`,
      # and so on until `.baz .bang .foo .bar`.
      #
      # @overload def subweave(seq1, seq2)
      # @param seq1 [Array<SimpleSequence or String>]
      # @param seq2 [Array<SimpleSequence or String>]
      # @return [Array<Array<SimpleSequence or String>>]
      def subweave(seq1, seq2, cache = {})
        return [seq2] if seq1.empty?
        return [seq1] if seq2.empty?

        seq1 = group_selectors(seq1)
        seq2 = group_selectors(seq2)
        lcs = Sass::Util.lcs(seq2, seq1) do |s1, s2|
          next s1 if s1 == s2
          next unless s1.first.is_a?(SimpleSequence) && s2.first.is_a?(SimpleSequence)
          next s2 if subweave_superselector?(s1, s2)
          next s1 if subweave_superselector?(s2, s1)
        end

        diff = []
        until lcs.empty?
          diff << chunks(seq1, seq2) {|s| subweave_superselector?(s.first, lcs.first)} << [lcs.shift]
          seq1.shift
          seq2.shift
        end
        diff << chunks(seq1, seq2) {|s| s.empty?}
        diff.reject! {|c| c.empty?}

        Sass::Util.paths(diff).map {|p| p.flatten}
      end

      def chunks(seq1, seq2)
        chunk1 = []
        chunk1 << seq1.shift until yield seq1
        chunk2 = []
        chunk2 << seq2.shift until yield seq2
        return [] if chunk1.empty? && chunk2.empty?
        return [chunk2] if chunk1.empty?
        return [chunk1] if chunk2.empty?
        [chunk1 + chunk2, chunk2 + chunk1]
      end

      def group_selectors(seq)
        newseq = []
        tail = seq.dup
        until tail.empty?
          head = []
          begin
            head << tail.shift
          end while !tail.empty? && head.last.is_a?(String) || tail.first.is_a?(String)
          newseq << head
        end
        return newseq
      end

      def subweave_superselector?(sseq1, sseq2)
        if sseq1.size > 1
          # More complex selectors are never superselectors of less complex ones
          return unless sseq2.size > 1
          # .foo ~ .bar is a superselector of .foo + .bar
          return unless sseq1[1] == "~" ? sseq2[1] != ">" : sseq2[1] == sseq1[1]
          return unless sseq1.first.superselector?(sseq2.first)
          return true if sseq1.size == 2
          return false if sseq2.size == 2
          return subweave_superselector?(sseq1[2..-1], sseq2[2..-1])
        elsif sseq2.size > 1
          return true if sseq2[1] == ">" && sseq1.first.superselector?(sseq2.first)
          return false if sseq2.size == 2
          return subweave_superselector?(sseq1, sseq2[2..-1])
        else
          sseq1.first.superselector?(sseq2.first)
        end
      end

      def _hash
        members.reject {|m| m == "\n"}.hash
      end

      def _eql?(other)
        other.members.reject {|m| m == "\n"}.eql?(self.members.reject {|m| m == "\n"})
      end
    end
  end
end
module Sass
  module Selector
    # A unseparated sequence of selectors
    # that all apply to a single element.
    # For example, `.foo#bar[attr=baz]` is a simple sequence
    # of the selectors `.foo`, `#bar`, and `[attr=baz]`.
    class SimpleSequence < AbstractSequence
      # The array of individual selectors.
      #
      # @return [Array<Simple>]
      attr_reader :members

      # Returns the element or universal selector in this sequence,
      # if it exists.
      #
      # @return [Element, Universal, nil]
      def base
        @base ||= (members.first if members.first.is_a?(Element) || members.first.is_a?(Universal))
      end

      # Returns the non-base selectors in this sequence.
      #
      # @return [Set<Simple>]
      def rest
        @rest ||= Set.new(base ? members[1..-1] : members)
      end

      # @param selectors [Array<Simple>] See \{#members}
      def initialize(selectors)
        @members = selectors
      end

      # Resolves the {Parent} selectors within this selector
      # by replacing them with the given parent selector,
      # handling commas appropriately.
      #
      # @param super_seq [Sequence] The parent selector sequence
      # @return [Array<SimpleSequence>] This selector, with parent references resolved.
      #   This is an array because the parent selector is itself a {Sequence}
      # @raise [Sass::SyntaxError] If a parent selector is invalid
      def resolve_parent_refs(super_seq)
        # Parent selector only appears as the first selector in the sequence
        return [self] unless @members.first.is_a?(Parent)

        return super_seq.members if @members.size == 1
        unless super_seq.members.last.is_a?(SimpleSequence)
          raise Sass::SyntaxError.new("Invalid parent selector: " + super_seq.to_a.join)
        end

        super_seq.members[0...-1] +
          [SimpleSequence.new(super_seq.members.last.members + @members[1..-1])]
      end

      # Non-destrucively extends this selector with the extensions specified in a hash
      # (which should come from {Sass::Tree::Visitors::Cssize}).
      #
      # @overload def do_extend(extends)
      # @param extends [{Selector::Simple => Selector::Sequence}]
      #   The extensions to perform on this selector
      # @return [Array<Sequence>] A list of selectors generated
      #   by extending this selector with `extends`.
      # @see CommaSequence#do_extend
      def do_extend(extends, seen = Set.new)
        extends.get(members.to_set).map do |seq, sels|
          # If A {@extend B} and C {...},
          # seq is A, sels is B, and self is C

          self_without_sel = self.members - sels
          next unless unified = seq.members.last.unify(self_without_sel)
          [sels, seq.members[0...-1] + [unified]]
        end.compact.map do |sels, seq|
          seq = Sequence.new(seq)
          seen.include?(sels) ? [] : seq.do_extend(extends, seen + [sels])
        end.flatten.uniq
      end

      # Unifies this selector with another {SimpleSequence}'s {SimpleSequence#members members array},
      # returning another `SimpleSequence`
      # that matches both this selector and the input selector.
      #
      # @param sels [Array<Simple>] A {SimpleSequence}'s {SimpleSequence#members members array}
      # @return [SimpleSequence, nil] A {SimpleSequence} matching both `sels` and this selector,
      #   or `nil` if this is impossible (e.g. unifying `#foo` and `#bar`)
      # @raise [Sass::SyntaxError] If this selector cannot be unified.
      #   This will only ever occur when a dynamic selector,
      #   such as {Parent} or {Interpolation}, is used in unification.
      #   Since these selectors should be resolved
      #   by the time extension and unification happen,
      #   this exception will only ever be raised as a result of programmer error
      def unify(sels)
        return unless sseq = members.inject(sels) do |sseq, sel|
          return unless sseq
          sel.unify(sseq)
        end
        SimpleSequence.new(sseq)
      end

      # Returns whether or not this selector matches all elements
      # that the given selector matches (as well as possibly more).
      #
      # @example
      #   (.foo).superselector?(.foo.bar) #=> true
      #   (.foo).superselector?(.bar) #=> false
      # @param sseq [SimpleSequence]
      # @return [Boolean]
      def superselector?(sseq)
        (base.nil? || base.eql?(sseq.base)) && rest.subset?(sseq.rest)
      end

      # @see Simple#to_a
      def to_a
        @members.map {|sel| sel.to_a}.flatten
      end

      # Returns a string representation of the sequence.
      # This is basically the selector string.
      #
      # @return [String]
      def inspect
        members.map {|m| m.inspect}.join
      end

      private

      def _hash
        [base, Sass::Util.set_hash(rest)].hash
      end

      def _eql?(other)
        other.base.eql?(self.base) && Sass::Util.set_eql?(other.rest, self.rest)
      end
    end
  end
end

module Sass
  # A namespace for nodes in the parse tree for selectors.
  #
  # {CommaSequence} is the toplevel seelctor,
  # representing a comma-separated sequence of {Sequence}s,
  # such as `foo bar, baz bang`.
  # {Sequence} is the next level,
  # representing {SimpleSequence}s separated by combinators (e.g. descendant or child),
  # such as `foo bar` or `foo > bar baz`.
  # {SimpleSequence} is a sequence of selectors that all apply to a single element,
  # such as `foo.bar[attr=val]`.
  # Finally, {Simple} is the superclass of the simplest selectors,
  # such as `.foo` or `#bar`.
  module Selector
    # A parent-referencing selector (`&` in Sass).
    # The function of this is to be replaced by the parent selector
    # in the nested hierarchy.
    class Parent < Simple
      # @see Selector#to_a
      def to_a
        ["&"]
      end

      # Always raises an exception.
      #
      # @raise [Sass::SyntaxError] Parent selectors should be resolved before unification
      # @see Selector#unify
      def unify(sels)
        raise Sass::SyntaxError.new("[BUG] Cannot unify parent selectors.")
      end
    end

    # A class selector (e.g. `.foo`).
    class Class < Simple
      # The class name.
      #
      # @return [Array<String, Sass::Script::Node>]
      attr_reader :name

      # @param name [Array<String, Sass::Script::Node>] The class name
      def initialize(name)
        @name = name
      end

      # @see Selector#to_a
      def to_a
        [".", *@name]
      end
    end

    # An id selector (e.g. `#foo`).
    class Id < Simple
      # The id name.
      #
      # @return [Array<String, Sass::Script::Node>]
      attr_reader :name

      # @param name [Array<String, Sass::Script::Node>] The id name
      def initialize(name)
        @name = name
      end

      # @see Selector#to_a
      def to_a
        ["#", *@name]
      end

      # Returns `nil` if `sels` contains an {Id} selector
      # with a different name than this one.
      #
      # @see Selector#unify
      def unify(sels)
        return if sels.any? {|sel2| sel2.is_a?(Id) && self.name != sel2.name}
        super
      end
    end

    # A universal selector (`*` in CSS).
    class Universal < Simple
      # The selector namespace.
      # `nil` means the default namespace,
      # `[""]` means no namespace,
      # `["*"]` means any namespace.
      #
      # @return [Array<String, Sass::Script::Node>, nil]
      attr_reader :namespace

      # @param namespace [Array<String, Sass::Script::Node>, nil] See \{#namespace}
      def initialize(namespace)
        @namespace = namespace
      end

      # @see Selector#to_a
      def to_a
        @namespace ? @namespace + ["|*"] : ["*"]
      end

      # Unification of a universal selector is somewhat complicated,
      # especially when a namespace is specified.
      # If there is no namespace specified
      # or any namespace is specified (namespace `"*"`),
      # then `sel` is returned without change
      # (unless it's empty, in which case `"*"` is required).
      #
      # If a namespace is specified
      # but `sel` does not specify a namespace,
      # then the given namespace is applied to `sel`,
      # either by adding this {Universal} selector
      # or applying this namespace to an existing {Element} selector.
      #
      # If both this selector *and* `sel` specify namespaces,
      # those namespaces are unified via {Simple#unify_namespaces}
      # and the unified namespace is used, if possible.
      #
      # @todo There are lots of cases that this documentation specifies;
      #   make sure we thoroughly test **all of them**.
      # @todo Keep track of whether a default namespace has been declared
      #   and handle namespace-unspecified selectors accordingly.
      # @todo If any branch of a CommaSequence ends up being just `"*"`,
      #   then all other branches should be eliminated
      #
      # @see Selector#unify
      def unify(sels)
        name =
          case sels.first
          when Universal; :universal
          when Element; sels.first.name
          else
            return [self] + sels unless namespace.nil? || namespace == ['*']
            return sels unless sels.empty?
            return [self]
          end

        ns, accept = unify_namespaces(namespace, sels.first.namespace)
        return unless accept
        [name == :universal ? Universal.new(ns) : Element.new(name, ns)] + sels[1..-1]
      end
    end

    # An element selector (e.g. `h1`).
    class Element < Simple
      # The element name.
      #
      # @return [Array<String, Sass::Script::Node>]
      attr_reader :name

      # The selector namespace.
      # `nil` means the default namespace,
      # `[""]` means no namespace,
      # `["*"]` means any namespace.
      #
      # @return [Array<String, Sass::Script::Node>, nil]
      attr_reader :namespace

      # @param name [Array<String, Sass::Script::Node>] The element name
      # @param namespace [Array<String, Sass::Script::Node>, nil] See \{#namespace}
      def initialize(name, namespace)
        @name = name
        @namespace = namespace
      end

      # @see Selector#to_a
      def to_a
        @namespace ? @namespace + ["|"] + @name : @name
      end

      # Unification of an element selector is somewhat complicated,
      # especially when a namespace is specified.
      # First, if `sel` contains another {Element} with a different \{#name},
      # then the selectors can't be unified and `nil` is returned.
      #
      # Otherwise, if `sel` doesn't specify a namespace,
      # or it specifies any namespace (via `"*"`),
      # then it's returned with this element selector
      # (e.g. `.foo` becomes `a.foo` or `svg|a.foo`).
      # Similarly, if this selector doesn't specify a namespace,
      # the namespace from `sel` is used.
      #
      # If both this selector *and* `sel` specify namespaces,
      # those namespaces are unified via {Simple#unify_namespaces}
      # and the unified namespace is used, if possible.
      #
      # @todo There are lots of cases that this documentation specifies;
      #   make sure we thoroughly test **all of them**.
      # @todo Keep track of whether a default namespace has been declared
      #   and handle namespace-unspecified selectors accordingly.
      #
      # @see Selector#unify
      def unify(sels)
        case sels.first
        when Universal;
        when Element; return unless name == sels.first.name
        else return [self] + sels
        end

        ns, accept = unify_namespaces(namespace, sels.first.namespace)
        return unless accept
        [Element.new(name, ns)] + sels[1..-1]
      end
    end

    # Selector interpolation (`#{}` in Sass).
    class Interpolation < Simple
      # The script to run.
      #
      # @return [Sass::Script::Node]
      attr_reader :script

      # @param script [Sass::Script::Node] The script to run
      def initialize(script)
        @script = script
      end

      # @see Selector#to_a
      def to_a
        [@script]
      end

      # Always raises an exception.
      #
      # @raise [Sass::SyntaxError] Interpolation selectors should be resolved before unification
      # @see Selector#unify
      def unify(sels)
        raise Sass::SyntaxError.new("[BUG] Cannot unify interpolation selectors.")
      end
    end

    # An attribute selector (e.g. `[href^="http://"]`).
    class Attribute < Simple
      # The attribute name.
      #
      # @return [Array<String, Sass::Script::Node>]
      attr_reader :name

      # The attribute namespace.
      # `nil` means the default namespace,
      # `[""]` means no namespace,
      # `["*"]` means any namespace.
      #
      # @return [Array<String, Sass::Script::Node>, nil]
      attr_reader :namespace

      # The matching operator, e.g. `"="` or `"^="`.
      #
      # @return [String]
      attr_reader :operator

      # The right-hand side of the operator.
      #
      # @return [Array<String, Sass::Script::Node>]
      attr_reader :value

      # @param name [Array<String, Sass::Script::Node>] The attribute name
      # @param namespace [Array<String, Sass::Script::Node>, nil] See \{#namespace}
      # @param operator [String] The matching operator, e.g. `"="` or `"^="`
      # @param value [Array<String, Sass::Script::Node>] See \{#value}
      def initialize(name, namespace, operator, value)
        @name = name
        @namespace = namespace
        @operator = operator
        @value = value
      end

      # @see Selector#to_a
      def to_a
        res = ["["]
        res.concat(@namespace) << "|" if @namespace
        res.concat @name
        (res << @operator).concat @value if @value
        res << "]"
      end
    end

    # A pseudoclass (e.g. `:visited`) or pseudoelement (e.g. `::first-line`) selector.
    # It can have arguments (e.g. `:nth-child(2n+1)`).
    class Pseudo < Simple
      # The type of the selector.
      # `:class` if this is a pseudoclass selector,
      # `:element` if it's a pseudoelement.
      #
      # @return [Symbol]
      attr_reader :type

      # The name of the selector.
      #
      # @return [Array<String, Sass::Script::Node>]
      attr_reader :name

      # The argument to the selector,
      # or `nil` if no argument was given.
      #
      # This may include SassScript nodes that will be run during resolution.
      # Note that this should not include SassScript nodes
      # after resolution has taken place.
      #
      # @return [Array<String, Sass::Script::Node>, nil]
      attr_reader :arg

      # @param type [Symbol] See \{#type}
      # @param name [Array<String, Sass::Script::Node>] The name of the selector
      # @param arg [nil, Array<String, Sass::Script::Node>] The argument to the selector,
      #   or nil if no argument was given
      def initialize(type, name, arg)
        @type = type
        @name = name
        @arg = arg
      end

      # @see Selector#to_a
      def to_a
        res = [@type == :class ? ":" : "::"] + @name
        (res << "(").concat(Sass::Util.strip_string_array(@arg)) << ")" if @arg
        res
      end

      # Returns `nil` if this is a pseudoclass selector
      # and `sels` contains a pseudoclass selector different than this one.
      #
      # @see Selector#unify
      def unify(sels)
        return if type == :element && sels.any? do |sel|
          sel.is_a?(Pseudo) && sel.type == :element &&
            (sel.name != self.name || sel.arg != self.arg)
        end
        super
      end
    end

    # A pseudoclass selector whose argument is itself a selector
    # (e.g. `:not(.foo)` or `:-moz-all(.foo, .bar)`).
    class SelectorPseudoClass < Simple
      # The name of the pseudoclass.
      #
      # @return [String]
      attr_reader :name

      # The selector argument.
      #
      # @return [Selector::Sequence]
      attr_reader :selector

      # @param [String] The name of the pseudoclass
      # @param [Selector::Sequence] The selector argument
      def initialize(name, selector)
        @name = name
        @selector = selector
      end

      # @see Selector#to_a
      def to_a
        [":", @name, "("] + @selector.to_a + [")"]
      end
    end
  end
end
require 'set'

module Sass
  # The lexical environment for SassScript.
  # This keeps track of variable, mixin, and function definitions.
  #
  # A new environment is created for each level of Sass nesting.
  # This allows variables to be lexically scoped.
  # The new environment refers to the environment in the upper scope,
  # so it has access to variables defined in enclosing scopes,
  # but new variables are defined locally.
  #
  # Environment also keeps track of the {Engine} options
  # so that they can be made available to {Sass::Script::Functions}.
  class Environment
    # The enclosing environment,
    # or nil if this is the global environment.
    #
    # @return [Environment]
    attr_reader :parent
    attr_writer :options

    # @param parent [Environment] See \{#parent}
    def initialize(parent = nil)
      @parent = parent
      unless parent
        @stack = []
        @mixins_in_use = Set.new
        set_var("important", Script::String.new("!important"))
      end
    end

    # The options hash.
    # See {file:SASS_REFERENCE.md#sass_options the Sass options documentation}.
    #
    # @return [{Symbol => Object}]
    def options
      @options || parent_options || {}
    end

    # Push a new stack frame onto the mixin/include stack.
    #
    # @param frame_info [{Symbol => Object}]
    #   Frame information has the following keys:
    #
    #   `:filename`
    #   : The name of the file in which the lexical scope changed.
    #
    #   `:mixin`
    #   : The name of the mixin in which the lexical scope changed,
    #     or `nil` if it wasn't within in a mixin.
    #
    #   `:line`
    #   : The line of the file on which the lexical scope changed. Never nil.
    def push_frame(frame_info)
      top_of_stack = stack.last
      if top_of_stack && top_of_stack.delete(:prepared)
        top_of_stack.merge!(frame_info)
      else
        stack.push(top_of_stack = frame_info)
      end
      mixins_in_use << top_of_stack[:mixin] if top_of_stack[:mixin] && !top_of_stack[:prepared]
    end

    # Like \{#push\_frame}, but next time a stack frame is pushed,
    # it will be merged with this frame.
    #
    # @param frame_info [{Symbol => Object}] Same as for \{#push\_frame}.
    def prepare_frame(frame_info)
      push_frame(frame_info.merge(:prepared => true))
    end

    # Pop a stack frame from the mixin/include stack.
    def pop_frame
      stack.pop if stack.last && stack.last[:prepared]
      popped = stack.pop
      mixins_in_use.delete(popped[:mixin]) if popped && popped[:mixin]
    end

    # A list of stack frames in the mixin/include stack.
    # The last element in the list is the most deeply-nested frame.
    #
    # @return [Array<{Symbol => Object}>] The stack frames,
    #   of the form passed to \{#push\_frame}.
    def stack
      @stack ||= @parent.stack
    end

    # A set of names of mixins currently present in the stack.
    #
    # @return [Set<String>] The mixin names.
    def mixins_in_use
      @mixins_in_use ||= @parent.mixins_in_use
    end

    private

    def parent_options
      @parent_options ||= @parent && @parent.options
    end

    class << self
      private
      UNDERSCORE, DASH = '_', '-'

      # Note: when updating this,
      # update sass/yard/inherited_hash.rb as well.
      def inherited_hash(name)
        class_eval <<RUBY, __FILE__, __LINE__ + 1
          def #{name}(name)
            _#{name}(name.tr(UNDERSCORE, DASH))
          end

          def _#{name}(name)
            (@#{name}s && @#{name}s[name]) || @parent && @parent._#{name}(name)
          end
          protected :_#{name}

          def set_#{name}(name, value)
            name = name.tr(UNDERSCORE, DASH)
            @#{name}s[name] = value unless try_set_#{name}(name, value)
          end

          def try_set_#{name}(name, value)
            @#{name}s ||= {}
            if @#{name}s.include?(name)
              @#{name}s[name] = value
              true
            elsif @parent
              @parent.try_set_#{name}(name, value)
            else
              false
            end
          end
          protected :try_set_#{name}

          def set_local_#{name}(name, value)
            @#{name}s ||= {}
            @#{name}s[name.tr(UNDERSCORE, DASH)] = value
          end
RUBY
      end
    end

    # variable
    # Script::Literal
    inherited_hash :var
    # mixin
    # Sass::Callable
    inherited_hash :mixin
    # function
    # Sass::Callable
    inherited_hash :function
  end
end
require 'strscan'
module Sass::Script
  # The abstract superclass for SassScript parse tree nodes.
  #
  # Use \{#perform} to evaluate a parse tree.
  class Node
    # The options hash for this node.
    #
    # @return [{Symbol => Object}]
    attr_reader :options

    # The line of the document on which this node appeared.
    #
    # @return [Fixnum]
    attr_accessor :line

    # Sets the options hash for this node,
    # as well as for all child nodes.
    # See {file:SASS_REFERENCE.md#sass_options the Sass options documentation}.
    #
    # @param options [{Symbol => Object}] The options
    def options=(options)
      @options = options
      children.each do |c|
        if c.is_a? Hash
          c.values.each {|v| v.options = options }
        else
          c.options = options
        end
      end
    end

    # Evaluates the node.
    #
    # \{#perform} shouldn't be overridden directly;
    # instead, override \{#\_perform}.
    #
    # @param environment [Sass::Environment] The environment in which to evaluate the SassScript
    # @return [Literal] The SassScript object that is the value of the SassScript
    def perform(environment)
      _perform(environment)
    rescue Sass::SyntaxError => e
      e.modify_backtrace(:line => line)
      raise e
    end

    # Returns all child nodes of this node.
    #
    # @return [Array<Node>]
    def children
      Sass::Util.abstract(self)
    end

    # Returns the text of this SassScript expression.
    #
    # @return [String]
    def to_sass(opts = {})
      Sass::Util.abstract(self)
    end

    protected

    # Converts underscores to dashes if the :dasherize option is set.
    def dasherize(s, opts)
      if opts[:dasherize]
        s.gsub(/_/,'-')
      else
        s
      end
    end

    # Evaluates this node.
    # Note that all {Literal} objects created within this method
    # should have their \{#options} attribute set, probably via \{#opts}.
    #
    # @param environment [Sass::Environment] The environment in which to evaluate the SassScript
    # @return [Literal] The SassScript object that is the value of the SassScript
    # @see #perform
    def _perform(environment)
      Sass::Util.abstract(self)
    end

    # Sets the \{#options} field on the given literal and returns it
    #
    # @param literal [Literal]
    # @return [Literal]
    def opts(literal)
      literal.options = options
      literal
    end
  end
end
module Sass
  module Script
    # A SassScript parse node representing a variable.
    class Variable < Node
      # The name of the variable.
      #
      # @return [String]
      attr_reader :name

      # The underscored name of the variable.
      #
      # @return [String]
      attr_reader :underscored_name

      # @param name [String] See \{#name}
      def initialize(name)
        @name = name
        @underscored_name = name.gsub(/-/,"_")
        super()
      end

      # @return [String] A string representation of the variable
      def inspect(opts = {})
        return "!important" if name == "important"
        "$#{dasherize(name, opts)}"
      end
      alias_method :to_sass, :inspect

      # Returns an empty array.
      #
      # @return [Array<Node>] empty
      # @see Node#children
      def children
        []
      end

      protected

      # Evaluates the variable.
      #
      # @param environment [Sass::Environment] The environment in which to evaluate the SassScript
      # @return [Literal] The SassScript object that is the value of the variable
      # @raise [Sass::SyntaxError] if the variable is undefined
      def _perform(environment)
        raise SyntaxError.new("Undefined variable: \"$#{name}\".") unless val = environment.var(name)
        if val.is_a?(Number)
          val = val.dup
          val.original = nil
        end
        return val
      end
    end
  end
end
module Sass::Script
  # Methods in this module are accessible from the SassScript context.
  # For example, you can write
  #
  #     $color = hsl(120deg, 100%, 50%)
  #
  # and it will call {Sass::Script::Functions#hsl}.
  #
  # The following functions are provided:
  #
  # *Note: These functions are described in more detail below.*
  #
  # ## RGB Functions
  #
  # \{#rgb rgb($red, $green, $blue)}
  # : Converts an `rgb(red, green, blue)` triplet into a color.
  #
  # \{#rgba rgba($red, $green, $blue, $alpha)}
  # : Converts an `rgba(red, green, blue, alpha)` quadruplet into a color.
  #
  # \{#rgba rgba($color, $alpha)}
  # : Adds an alpha layer to any color value.
  #
  # \{#red red($color)}
  # : Gets the red component of a color.
  #
  # \{#green green($color)}
  # : Gets the green component of a color.
  #
  # \{#blue blue($color)}
  # : Gets the blue component of a color.
  #
  # \{#mix mix($color-1, $color-2, \[$weight\])}
  # : Mixes two colors together.
  #
  # ## HSL Functions
  #
  # \{#hsl hsl($hue, $saturation, $lightness)}
  # : Converts an `hsl(hue, saturation, lightness)` triplet into a color.
  #
  # \{#hsla hsla($hue, $saturation, $lightness, $alpha)}
  # : Converts an `hsla(hue, saturation, lightness, alpha)` quadruplet into a color.
  #
  # \{#hue hue($color)}
  # : Gets the hue component of a color.
  #
  # \{#saturation saturation($color)}
  # : Gets the saturation component of a color.
  #
  # \{#lightness lightness($color)}
  # : Gets the lightness component of a color.
  #
  # \{#adjust_hue adjust-hue($color, $degrees)}
  # : Changes the hue of a color.
  #
  # \{#lighten lighten($color, $amount)}
  # : Makes a color lighter.
  #
  # \{#darken darken($color, $amount)}
  # : Makes a color darker.
  #
  # \{#saturate saturate($color, $amount)}
  # : Makes a color more saturated.
  #
  # \{#desaturate desaturate($color, $amount)}
  # : Makes a color less saturated.
  #
  # \{#grayscale grayscale($color)}
  # : Converts a color to grayscale.
  #
  # \{#complement complement($color)}
  # : Returns the complement of a color.
  #
  # \{#invert invert($color)}
  # : Returns the inverse of a color.
  #
  # ## Opacity Functions
  #
  # \{#alpha alpha($color)} / \{#opacity opacity($color)}
  # : Gets the alpha component (opacity) of a color.
  #
  # \{#rgba rgba($color, $alpha)}
  # : Add or change an alpha layer for any color value.
  #
  # \{#opacify opacify($color, $amount)} / \{#fade_in fade-in($color, $amount)}
  # : Makes a color more opaque.
  #
  # \{#transparentize transparentize($color, $amount)} / \{#fade_out fade-out($color, $amount)}
  # : Makes a color more transparent.
  #
  # ## Other Color Functions
  #
  # \{#adjust_color adjust-color($color, \[$red\], \[$green\], \[$blue\], \[$hue\], \[$saturation\], \[$lightness\], \[$alpha\]}
  # : Increase or decrease any of the components of a color.
  #
  # \{#scale_color scale-color($color, \[$red\], \[$green\], \[$blue\], \[$hue\], \[$saturation\], \[$lightness\], \[$alpha\]}
  # : Fluidly scale one or more components of a color.
  #
  # \{#change_color change-color($color, \[$red\], \[$green\], \[$blue\], \[$hue\], \[$saturation\], \[$lightness\], \[$alpha\]}
  # : Changes one or more properties of a color.
  #
  # ## String Functions
  #
  # \{#unquote unquote($string)}
  # : Removes the quotes from a string.
  #
  # \{#quote quote($string)}
  # : Adds quotes to a string.
  #
  # ## Number Functions
  #
  # \{#percentage percentage($value)}
  # : Converts a unitless number to a percentage.
  #
  # \{#round round($value)}
  # : Rounds a number to the nearest whole number.
  #
  # \{#ceil ceil($value)}
  # : Rounds a number up to the nearest whole number.
  #
  # \{#floor floor($value)}
  # : Rounds a number down to the nearest whole number.
  #
  # \{#abs abs($value)}
  # : Returns the absolute value of a number.
  #
  # ## List Functions {#list-functions}
  #
  # \{#length length($list)}
  # : Returns the length of a list.
  #
  # \{#nth nth($list, $n)}
  # : Returns a specific item in a list.
  #
  # \{#join join($list1, $list2, \[$separator\])}
  # : Joins together two lists into one.
  #
  # ## Introspection Functions
  #
  # \{#type_of type-of($value)}
  # : Returns the type of a value.
  #
  # \{#unit unit($number)}
  # : Returns the units associated with a number.
  #
  # \{#unitless unitless($number)}
  # : Returns whether a number has units or not.
  #
  # \{#comparable comparable($number-1, $number-2)}
  # : Returns whether two numbers can be added or compared.
  #
  # ## Miscellaneous Functions
  #
  # \{#if if($condition, $if-true, $if-false)}
  # : Returns one of two values, depending on whether or not a condition is true.
  #
  # ## Adding Custom Functions
  #
  # New Sass functions can be added by adding Ruby methods to this module.
  # For example:
  #
  #     module Sass::Script::Functions
  #       def reverse(string)
  #         assert_type string, :String
  #         Sass::Script::String.new(string.value.reverse)
  #       end
  #       declare :reverse, :args => [:string]
  #     end
  #
  # Calling {declare} tells Sass the argument names for your function.
  # If omitted, the function will still work, but will not be able to accept keyword arguments.
  # {declare} can also allow your function to take arbitrary keyword arguments.
  #
  # There are a few things to keep in mind when modifying this module.
  # First of all, the arguments passed are {Sass::Script::Literal} objects.
  # Literal objects are also expected to be returned.
  # This means that Ruby values must be unwrapped and wrapped.
  #
  # Most Literal objects support the {Sass::Script::Literal#value value} accessor
  # for getting their Ruby values.
  # Color objects, though, must be accessed using {Sass::Script::Color#rgb rgb},
  # {Sass::Script::Color#red red}, {Sass::Script::Color#blue green}, or {Sass::Script::Color#blue blue}.
  #
  # Second, making Ruby functions accessible from Sass introduces the temptation
  # to do things like database access within stylesheets.
  # This is generally a bad idea;
  # since Sass files are by default only compiled once,
  # dynamic code is not a great fit.
  #
  # If you really, really need to compile Sass on each request,
  # first make sure you have adequate caching set up.
  # Then you can use {Sass::Engine} to render the code,
  # using the {file:SASS_REFERENCE.md#custom-option `options` parameter}
  # to pass in data that {EvaluationContext#options can be accessed}
  # from your Sass functions.
  #
  # Within one of the functions in this module,
  # methods of {EvaluationContext} can be used.
  #
  # ### Caveats
  #
  # When creating new {Literal} objects within functions,
  # be aware that it's not safe to call {Literal#to_s #to_s}
  # (or other methods that use the string representation)
  # on those objects without first setting {Node#options= the #options attribute}.
  module Functions
    @signatures = {}

    # A class representing a Sass function signature.
    #
    # @attr args [Array<Symbol>] The names of the arguments to the function.
    # @attr var_args [Boolean] Whether the function takes a variable number of arguments.
    # @attr var_kwargs [Boolean] Whether the function takes an arbitrary set of keyword arguments.
    Signature = Struct.new(:args, :var_args, :var_kwargs)

    # Declare a Sass signature for a Ruby-defined function.
    # This includes the names of the arguments,
    # whether the function takes a variable number of arguments,
    # and whether the function takes an arbitrary set of keyword arguments.
    #
    # It's not necessary to declare a signature for a function.
    # However, without a signature it won't support keyword arguments.
    #
    # A single function can have multiple signatures declared
    # as long as each one takes a different number of arguments.
    # It's also possible to declare multiple signatures
    # that all take the same number of arguments,
    # but none of them but the first will be used
    # unless the user uses keyword arguments.
    #
    # @param method_name [Symbol] The name of the method
    #   whose signature is being declared.
    # @param args [Array<Symbol>] The names of the arguments for the function signature.
    # @option options :var_args [Boolean] (false)
    #   Whether the function accepts a variable number of (unnamed) arguments
    #   in addition to the named arguments.
    # @option options :var_kwargs [Boolean] (false)
    #   Whether the function accepts other keyword arguments
    #   in addition to those in `:args`.
    #   If this is true, the Ruby function will be passed a hash from strings
    #   to {Sass::Script::Literal}s as the last argument.
    #   In addition, if this is true and `:var_args` is not,
    #   Sass will ensure that the last argument passed is a hash.
    # 
    # @example
    #   declare :rgba, [:hex, :alpha]
    #   declare :rgba, [:red, :green, :blue, :alpha]
    #   declare :accepts_anything, [], :var_args => true, :var_kwargs => true
    #   declare :some_func, [:foo, :bar, :baz], :var_kwargs => true
    def self.declare(method_name, args, options = {})
      @signatures[method_name] ||= []
      @signatures[method_name] << Signature.new(
        args.map {|s| s.to_s},
        options[:var_args],
        options[:var_kwargs])
    end

    # Determine the correct signature for the number of arguments
    # passed in for a given function.
    # If no signatures match, the first signature is returned for error messaging.
    #
    # @param method_name [Symbol] The name of the Ruby function to be called.
    # @param arg_arity [Number] The number of unnamed arguments the function was passed.
    # @param kwarg_arity [Number] The number of keyword arguments the function was passed.
    #
    # @return [{Symbol => Object}, nil]
    #   The signature options for the matching signature,
    #   or nil if no signatures are declared for this function. See {declare}.
    def self.signature(method_name, arg_arity, kwarg_arity)
      return unless @signatures[method_name]
      @signatures[method_name].each do |signature|
        return signature if signature.args.size == arg_arity + kwarg_arity
        next unless signature.args.size < arg_arity + kwarg_arity

        # We have enough args.
        # Now we need to figure out which args are varargs
        # and if the signature allows them.
        t_arg_arity, t_kwarg_arity = arg_arity, kwarg_arity
        if signature.args.size > t_arg_arity
          # we transfer some kwargs arity to args arity
          # if it does not have enough args -- assuming the names will work out.
          t_kwarg_arity -= (signature.args.size - t_arg_arity)
          t_arg_arity = signature.args.size
        end

        if (  t_arg_arity == signature.args.size ||   t_arg_arity > signature.args.size && signature.var_args  ) &&
           (t_kwarg_arity == 0                   || t_kwarg_arity > 0                   && signature.var_kwargs)
          return signature
        end
      end
      @signatures[method_name].first
    end

    # The context in which methods in {Script::Functions} are evaluated.
    # That means that all instance methods of {EvaluationContext}
    # are available to use in functions.
    class EvaluationContext
      include Functions

      # The options hash for the {Sass::Engine} that is processing the function call
      #
      # @return [{Symbol => Object}]
      attr_reader :options

      # @param options [{Symbol => Object}] See \{#options}
      def initialize(options)
        @options = options
      end

      # Asserts that the type of a given SassScript value
      # is the expected type (designated by a symbol).
      #
      # Valid types are `:Bool`, `:Color`, `:Number`, and `:String`.
      # Note that `:String` will match both double-quoted strings
      # and unquoted identifiers.
      #
      # @example
      #   assert_type value, :String
      #   assert_type value, :Number
      # @param value [Sass::Script::Literal] A SassScript value
      # @param type [Symbol] The name of the type the value is expected to be
      # @param name [String, nil] The name of the argument.
      def assert_type(value, type, name = nil)
        return if value.is_a?(Sass::Script.const_get(type))
        err = "#{value.inspect} is not a #{type.to_s.downcase}"
        err = "$#{name}: " + err if name
        raise ArgumentError.new(err)
      end
    end

    class << self
      # Returns whether user function with a given name exists.
      #
      # @param function_name [String]
      # @return [Boolean]
      alias_method :callable?, :public_method_defined?

      private
      def include(*args)
        r = super
        # We have to re-include ourselves into EvaluationContext to work around
        # an icky Ruby restriction.
        EvaluationContext.send :include, self
        r
      end
    end

    # Creates a {Color} object from red, green, and blue values.
    #
    # @param red [Number]
    #   A number between 0 and 255 inclusive,
    #   or between 0% and 100% inclusive
    # @param green [Number]
    #   A number between 0 and 255 inclusive,
    #   or between 0% and 100% inclusive
    # @param blue [Number]
    #   A number between 0 and 255 inclusive,
    #   or between 0% and 100% inclusive
    # @see #rgba
    # @return [Color]
    def rgb(red, green, blue)
      assert_type red, :Number
      assert_type green, :Number
      assert_type blue, :Number

      Color.new([red, green, blue].map do |c|
          v = c.value
          if c.numerator_units == ["%"] && c.denominator_units.empty?
            next v * 255 / 100.0 if (0..100).include?(v)
            raise ArgumentError.new("Color value #{c} must be between 0% and 100% inclusive")
          else
            next v if (0..255).include?(v)
            raise ArgumentError.new("Color value #{v} must be between 0 and 255 inclusive")
          end
        end)
    end
    declare :rgb, [:red, :green, :blue]

    # @see #rgb
    # @overload rgba(red, green, blue, alpha)
    #   Creates a {Color} object from red, green, and blue values,
    #   as well as an alpha channel indicating opacity.
    #
    #   @param red [Number]
    #     A number between 0 and 255 inclusive
    #   @param green [Number]
    #     A number between 0 and 255 inclusive
    #   @param blue [Number]
    #     A number between 0 and 255 inclusive
    #   @param alpha [Number]
    #     A number between 0 and 1
    #   @return [Color]
    #
    # @overload rgba(color, alpha)
    #   Sets the opacity of a color.
    #
    #   @example
    #     rgba(#102030, 0.5) => rgba(16, 32, 48, 0.5)
    #     rgba(blue, 0.2)    => rgba(0, 0, 255, 0.2)
    #
    #   @param color [Color]
    #   @param alpha [Number]
    #     A number between 0 and 1
    #   @return [Color]
    def rgba(*args)
      case args.size
      when 2
        color, alpha = args

        assert_type color, :Color
        assert_type alpha, :Number

        unless (0..1).include?(alpha.value)
          raise ArgumentError.new("Alpha channel #{alpha.value} must be between 0 and 1 inclusive")
        end

        color.with(:alpha => alpha.value)
      when 4
        red, green, blue, alpha = args
        rgba(rgb(red, green, blue), alpha)
      else
        raise ArgumentError.new("wrong number of arguments (#{args.size} for 4)")
      end
    end
    declare :rgba, [:red, :green, :blue, :alpha]
    declare :rgba, [:color, :alpha]

    # Creates a {Color} object from hue, saturation, and lightness.
    # Uses the algorithm from the [CSS3 spec](http://www.w3.org/TR/css3-color/#hsl-color).
    #
    # @param hue [Number] The hue of the color.
    #   Should be between 0 and 360 degrees, inclusive
    # @param saturation [Number] The saturation of the color.
    #   Must be between `0%` and `100%`, inclusive
    # @param lightness [Number] The lightness of the color.
    #   Must be between `0%` and `100%`, inclusive
    # @return [Color] The resulting color
    # @see #hsla
    # @raise [ArgumentError] if `saturation` or `lightness` are out of bounds
    def hsl(hue, saturation, lightness)
      hsla(hue, saturation, lightness, Number.new(1))
    end
    declare :hsl, [:hue, :saturation, :lightness]

    # Creates a {Color} object from hue, saturation, and lightness,
    # as well as an alpha channel indicating opacity.
    # Uses the algorithm from the [CSS3 spec](http://www.w3.org/TR/css3-color/#hsl-color).
    #
    # @param hue [Number] The hue of the color.
    #   Should be between 0 and 360 degrees, inclusive
    # @param saturation [Number] The saturation of the color.
    #   Must be between `0%` and `100%`, inclusive
    # @param lightness [Number] The lightness of the color.
    #   Must be between `0%` and `100%`, inclusive
    # @param alpha [Number] The opacity of the color.
    #   Must be between 0 and 1, inclusive
    # @return [Color] The resulting color
    # @see #hsl
    # @raise [ArgumentError] if `saturation`, `lightness`, or `alpha` are out of bounds
    def hsla(hue, saturation, lightness, alpha)
      assert_type hue, :Number
      assert_type saturation, :Number
      assert_type lightness, :Number
      assert_type alpha, :Number

      unless (0..1).include?(alpha.value)
        raise ArgumentError.new("Alpha channel #{alpha.value} must be between 0 and 1")
      end

      original_s = saturation
      original_l = lightness
      # This algorithm is from http://www.w3.org/TR/css3-color#hsl-color
      h, s, l = [hue, saturation, lightness].map { |a| a.value }
      raise ArgumentError.new("Saturation #{s} must be between 0% and 100%") unless (0..100).include?(s)
      raise ArgumentError.new("Lightness #{l} must be between 0% and 100%") unless (0..100).include?(l)

      Color.new(:hue => h, :saturation => s, :lightness => l, :alpha => alpha.value)
    end
    declare :hsla, [:hue, :saturation, :lightness, :alpha]

    # Returns the red component of a color.
    #
    # @param color [Color]
    # @return [Number]
    # @raise [ArgumentError] If `color` isn't a color
    def red(color)
      assert_type color, :Color
      Sass::Script::Number.new(color.red)
    end
    declare :red, [:color]

    # Returns the green component of a color.
    #
    # @param color [Color]
    # @return [Number]
    # @raise [ArgumentError] If `color` isn't a color
    def green(color)
      assert_type color, :Color
      Sass::Script::Number.new(color.green)
    end
    declare :green, [:color]

    # Returns the blue component of a color.
    #
    # @param color [Color]
    # @return [Number]
    # @raise [ArgumentError] If `color` isn't a color
    def blue(color)
      assert_type color, :Color
      Sass::Script::Number.new(color.blue)
    end
    declare :blue, [:color]

    # Returns the hue component of a color.
    #
    # See [the CSS3 HSL specification](http://en.wikipedia.org/wiki/HSL_and_HSV#Conversion_from_RGB_to_HSL_or_HSV).
    #
    # Calculated from RGB where necessary via [this algorithm](http://en.wikipedia.org/wiki/HSL_and_HSV#Conversion_from_RGB_to_HSL_or_HSV).
    #
    # @param color [Color]
    # @return [Number] between 0deg and 360deg
    # @see #adjust_hue
    # @raise [ArgumentError] if `color` isn't a color
    def hue(color)
      assert_type color, :Color
      Sass::Script::Number.new(color.hue, ["deg"])
    end
    declare :hue, [:color]

    # Returns the saturation component of a color.
    #
    # See [the CSS3 HSL specification](http://en.wikipedia.org/wiki/HSL_and_HSV#Conversion_from_RGB_to_HSL_or_HSV).
    #
    # Calculated from RGB where necessary via [this algorithm](http://en.wikipedia.org/wiki/HSL_and_HSV#Conversion_from_RGB_to_HSL_or_HSV).
    #
    # @param color [Color]
    # @return [Number] between 0% and 100%
    # @see #saturate
    # @see #desaturate
    # @raise [ArgumentError] if `color` isn't a color
    def saturation(color)
      assert_type color, :Color
      Sass::Script::Number.new(color.saturation, ["%"])
    end
    declare :saturation, [:color]

    # Returns the hue component of a color.
    #
    # See [the CSS3 HSL specification](http://en.wikipedia.org/wiki/HSL_and_HSV#Conversion_from_RGB_to_HSL_or_HSV).
    #
    # Calculated from RGB where necessary via [this algorithm](http://en.wikipedia.org/wiki/HSL_and_HSV#Conversion_from_RGB_to_HSL_or_HSV).
    #
    # @param color [Color]
    # @return [Number] between 0% and 100%
    # @see #lighten
    # @see #darken
    # @raise [ArgumentError] if `color` isn't a color
    def lightness(color)
      assert_type color, :Color
      Sass::Script::Number.new(color.lightness, ["%"])
    end
    declare :lightness, [:color]

    # Returns the alpha component (opacity) of a color.
    # This is 1 unless otherwise specified.
    #
    # This function also supports the proprietary Microsoft
    # `alpha(opacity=20)` syntax.
    #
    # @overload def alpha(color)
    # @param color [Color]
    # @return [Number]
    # @see #opacify
    # @see #transparentize
    # @raise [ArgumentError] If `color` isn't a color
    def alpha(*args)
      if args.all? do |a|
          a.is_a?(Sass::Script::String) && a.type == :identifier &&
            a.value =~ /^[a-zA-Z]+\s*=/
        end
        # Support the proprietary MS alpha() function
        return Sass::Script::String.new("alpha(#{args.map {|a| a.to_s}.join(", ")})")
      end

      opacity(*args)
    end
    declare :alpha, [:color]

    # Returns the alpha component (opacity) of a color.
    # This is 1 unless otherwise specified.
    #
    # @param color [Color]
    # @return [Number]
    # @see #opacify
    # @see #transparentize
    # @raise [ArgumentError] If `color` isn't a color
    def opacity(color)
      assert_type color, :Color
      Sass::Script::Number.new(color.alpha)
    end
    declare :opacity, [:color]

    # Makes a color more opaque.
    # Takes a color and an amount between 0 and 1,
    # and returns a color with the opacity increased by that value.
    #
    # @example
    #   opacify(rgba(0, 0, 0, 0.5), 0.1) => rgba(0, 0, 0, 0.6)
    #   opacify(rgba(0, 0, 17, 0.8), 0.2) => #001
    # @param color [Color]
    # @param amount [Number]
    # @return [Color]
    # @see #transparentize
    # @raise [ArgumentError] If `color` isn't a color,
    #   or `number` isn't a number between 0 and 1
    def opacify(color, amount)
      _adjust(color, amount, :alpha, 0..1, :+)
    end
    declare :opacify, [:color, :amount]

    alias_method :fade_in, :opacify
    declare :fade_in, [:color, :amount]

    # Makes a color more transparent.
    # Takes a color and an amount between 0 and 1,
    # and returns a color with the opacity decreased by that value.
    #
    # @example
    #   transparentize(rgba(0, 0, 0, 0.5), 0.1) => rgba(0, 0, 0, 0.4)
    #   transparentize(rgba(0, 0, 0, 0.8), 0.2) => rgba(0, 0, 0, 0.6)
    # @param color [Color]
    # @param amount [Number]
    # @return [Color]
    # @see #opacify
    # @raise [ArgumentError] If `color` isn't a color,
    #   or `number` isn't a number between 0 and 1
    def transparentize(color, amount)
      _adjust(color, amount, :alpha, 0..1, :-)
    end
    declare :transparentize, [:color, :amount]

    alias_method :fade_out, :transparentize
    declare :fade_out, [:color, :amount]

    # Makes a color lighter.
    # Takes a color and an amount between 0% and 100%,
    # and returns a color with the lightness increased by that value.
    #
    # @example
    #   lighten(hsl(0, 0%, 0%), 30%) => hsl(0, 0, 30)
    #   lighten(#800, 20%) => #e00
    # @param color [Color]
    # @param amount [Number]
    # @return [Color]
    # @see #darken
    # @raise [ArgumentError] If `color` isn't a color,
    #   or `number` isn't a number between 0% and 100%
    def lighten(color, amount)
      _adjust(color, amount, :lightness, 0..100, :+, "%")
    end
    declare :lighten, [:color, :amount]

    # Makes a color darker.
    # Takes a color and an amount between 0% and 100%,
    # and returns a color with the lightness decreased by that value.
    #
    # @example
    #   darken(hsl(25, 100%, 80%), 30%) => hsl(25, 100%, 50%)
    #   darken(#800, 20%) => #200
    # @param color [Color]
    # @param amount [Number]
    # @return [Color]
    # @see #lighten
    # @raise [ArgumentError] If `color` isn't a color,
    #   or `number` isn't a number between 0% and 100%
    def darken(color, amount)
      _adjust(color, amount, :lightness, 0..100, :-, "%")
    end
    declare :darken, [:color, :amount]

    # Makes a color more saturated.
    # Takes a color and an amount between 0% and 100%,
    # and returns a color with the saturation increased by that value.
    #
    # @example
    #   saturate(hsl(120, 30%, 90%), 20%) => hsl(120, 50%, 90%)
    #   saturate(#855, 20%) => #9e3f3f
    # @param color [Color]
    # @param amount [Number]
    # @return [Color]
    # @see #desaturate
    # @raise [ArgumentError] If `color` isn't a color,
    #   or `number` isn't a number between 0% and 100%
    def saturate(color, amount)
      _adjust(color, amount, :saturation, 0..100, :+, "%")
    end
    declare :saturate, [:color, :amount]

    # Makes a color less saturated.
    # Takes a color and an amount between 0% and 100%,
    # and returns a color with the saturation decreased by that value.
    #
    # @example
    #   desaturate(hsl(120, 30%, 90%), 20%) => hsl(120, 10%, 90%)
    #   desaturate(#855, 20%) => #726b6b
    # @param color [Color]
    # @param amount [Number]
    # @return [Color]
    # @see #saturate
    # @raise [ArgumentError] If `color` isn't a color,
    #   or `number` isn't a number between 0% and 100%
    def desaturate(color, amount)
      _adjust(color, amount, :saturation, 0..100, :-, "%")
    end
    declare :desaturate, [:color, :amount]

    # Changes the hue of a color while retaining the lightness and saturation.
    # Takes a color and a number of degrees (usually between -360deg and 360deg),
    # and returns a color with the hue rotated by that value.
    #
    # @example
    #   adjust-hue(hsl(120, 30%, 90%), 60deg) => hsl(180, 30%, 90%)
    #   adjust-hue(hsl(120, 30%, 90%), 060deg) => hsl(60, 30%, 90%)
    #   adjust-hue(#811, 45deg) => #886a11
    # @param color [Color]
    # @param amount [Number]
    # @return [Color]
    # @raise [ArgumentError] If `color` isn't a color, or `number` isn't a number
    def adjust_hue(color, degrees)
      assert_type color, :Color
      assert_type degrees, :Number
      color.with(:hue => color.hue + degrees.value)
    end
    declare :adjust_hue, [:color, :degrees]

    # Adjusts one or more properties of a color.
    # This can change the red, green, blue, hue, saturation, value, and alpha properties.
    # The properties are specified as keyword arguments,
    # and are added to or subtracted from the color's current value for that property.
    #
    # `$red`, `$green`, and `$blue` properties should be between 0 and 255.
    # `$saturation` and `$lightness` should be between 0% and 100%.
    # `$alpha` should be between 0 and 1.
    #
    # All properties are optional.
    # You can't specify both RGB properties (`$red`, `$green`, `$blue`)
    # and HSL properties (`$hue`, `$saturation`, `$value`) at the same time.
    #
    # @example
    #   adjust-color(#102030, $blue: 5) => #102035
    #   adjust-color(#102030, $red: -5, $blue: 5) => #0b2035
    #   adjust-color(hsl(25, 100%, 80%), $lightness: -30%, $alpha: -0.4) => hsla(25, 100%, 50%, 0.6)
    # @param color [Color]
    # @param red [Number]
    # @param green [Number]
    # @param blue [Number]
    # @param hue [Number]
    # @param saturation [Number]
    # @param lightness [Number]
    # @param alpha [Number]
    # @return [Color]
    # @raise [ArgumentError] if `color` is not a color,
    #   if any keyword argument is not a number,
    #   if any keyword argument is not in the legal range,
    #   if an unexpected keyword argument is given,
    #   or if both HSL and RGB properties are given.
    def adjust_color(color, kwargs)
      assert_type color, :Color
      with = Sass::Util.map_hash({
          "red" => [-255..255, ""],
          "green" => [-255..255, ""],
          "blue" => [-255..255, ""],
          "hue" => nil,
          "saturation" => [-100..100, "%"],
          "lightness" => [-100..100, "%"],
          "alpha" => [-1..1, ""]
        }) do |name, (range, units)|

        next unless val = kwargs.delete(name)
        assert_type val, :Number, name
        if range && !range.include?(val.value)
          raise ArgumentError.new("$#{name}: Amount #{val} must be between #{range.first}#{units} and #{range.last}#{units}")
        end
        adjusted = color.send(name) + val.value
        adjusted = [0, Sass::Util.restrict(adjusted, range)].max if range
        [name.to_sym, adjusted]
      end

      unless kwargs.empty?
        name, val = kwargs.to_a.first
        raise ArgumentError.new("Unknown argument $#{name} (#{val})")
      end

      color.with(with)
    end
    declare :adjust_color, [:color], :var_kwargs => true

    # Scales one or more properties of a color by a percentage value.
    # Unlike \{#adjust_color adjust-color}, which changes a color's properties by fixed amounts,
    # \{#scale_color scale-color} fluidly changes them based on how high or low they already are.
    # That means that lightening an already-light color with \{#scale_color scale-color}
    # won't change the lightness much,
    # but lightening a dark color by the same amount will change it more dramatically.
    # This has the benefit of making `scale-color($color, ...)` have a similar effect
    # regardless of what `$color` is.
    #
    # For example, the lightness of a color can be anywhere between 0 and 100.
    # If `scale-color($color, $lightness: 40%)` is called, the resulting color's lightness
    # will be 40% of the way between its original lightness and 100.
    # If `scale-color($color, $lightness: -40%)` is called instead,
    # the lightness will be 40% of the way between the original and 0.
    #
    # This can change the red, green, blue, saturation, value, and alpha properties.
    # The properties are specified as keyword arguments.
    # All arguments should be percentages between 0% and 100%.
    #
    # All properties are optional.
    # You can't specify both RGB properties (`$red`, `$green`, `$blue`)
    # and HSL properties (`$saturation`, `$value`) at the same time.
    #
    # @example
    #   scale-color(hsl(120, 70, 80), $lightness: 50%) => hsl(120, 70, 90)
    #   scale-color(rgb(200, 150, 170), $green: -40%, $blue: 70%) => rgb(200, 90, 229)
    #   scale-color(hsl(200, 70, 80), $saturation: -90%, $alpha: -30%) => hsla(200, 7, 80, 0.7)
    # @param color [Color]
    # @param red [Number]
    # @param green [Number]
    # @param blue [Number]
    # @param saturation [Number]
    # @param lightness [Number]
    # @param alpha [Number]
    # @return [Color]
    # @raise [ArgumentError] if `color` is not a color,
    #   if any keyword argument is not a percentage between 0% and 100%,
    #   if an unexpected keyword argument is given,
    #   or if both HSL and RGB properties are given.
    def scale_color(color, kwargs)
      assert_type color, :Color
      with = Sass::Util.map_hash({
          "red" => 255,
          "green" => 255,
          "blue" => 255,
          "saturation" => 100,
          "lightness" => 100,
          "alpha" => 1
        }) do |name, max|

        next unless val = kwargs.delete(name)
        assert_type val, :Number, name
        if !(val.numerator_units == ['%'] && val.denominator_units.empty?)
          raise ArgumentError.new("$#{name}: Amount #{val} must be a % (e.g. #{val.value}%)")
        elsif !(-100..100).include?(val.value)
          raise ArgumentError.new("$#{name}: Amount #{val} must be between -100% and 100%")
        end

        current = color.send(name)
        scale = val.value/100.0
        diff = scale > 0 ? max - current : current
        [name.to_sym, current + diff*scale]
      end

      unless kwargs.empty?
        name, val = kwargs.to_a.first
        raise ArgumentError.new("Unknown argument $#{name} (#{val})")
      end

      color.with(with)
    end
    declare :scale_color, [:color], :var_kwargs => true

    # Changes one or more properties of a color.
    # This can change the red, green, blue, hue, saturation, value, and alpha properties.
    # The properties are specified as keyword arguments,
    # and replace the color's current value for that property.
    #
    # `$red`, `$green`, and `$blue` properties should be between 0 and 255.
    # `$saturation` and `$lightness` should be between 0% and 100%.
    # `$alpha` should be between 0 and 1.
    #
    # All properties are optional.
    # You can't specify both RGB properties (`$red`, `$green`, `$blue`)
    # and HSL properties (`$hue`, `$saturation`, `$value`) at the same time.
    #
    # @example
    #   change-color(#102030, $blue: 5) => #102005
    #   change-color(#102030, $red: 120, $blue: 5) => #782005
    #   change-color(hsl(25, 100%, 80%), $lightness: 40%, $alpha: 0.8) => hsla(25, 100%, 40%, 0.8)
    # @param color [Color]
    # @param red [Number]
    # @param green [Number]
    # @param blue [Number]
    # @param hue [Number]
    # @param saturation [Number]
    # @param lightness [Number]
    # @param alpha [Number]
    # @return [Color]
    # @raise [ArgumentError] if `color` is not a color,
    #   if any keyword argument is not a number,
    #   if any keyword argument is not in the legal range,
    #   if an unexpected keyword argument is given,
    #   or if both HSL and RGB properties are given.
    def change_color(color, kwargs)
      assert_type color, :Color
      with = Sass::Util.map_hash(%w[red green blue hue saturation lightness alpha]) do |name, max|
        next unless val = kwargs.delete(name)
        assert_type val, :Number, name
        [name.to_sym, val.value]
      end

      unless kwargs.empty?
        name, val = kwargs.to_a.first
        raise ArgumentError.new("Unknown argument $#{name} (#{val})")
      end

      color.with(with)
    end
    declare :change_color, [:color], :var_kwargs => true

    # Mixes together two colors.
    # Specifically, takes the average of each of the RGB components,
    # optionally weighted by the given percentage.
    # The opacity of the colors is also considered when weighting the components.
    #
    # The weight specifies the amount of the first color that should be included
    # in the returned color.
    # The default, 50%, means that half the first color
    # and half the second color should be used.
    # 25% means that a quarter of the first color
    # and three quarters of the second color should be used.
    #
    # @example
    #   mix(#f00, #00f) => #7f007f
    #   mix(#f00, #00f, 25%) => #3f00bf
    #   mix(rgba(255, 0, 0, 0.5), #00f) => rgba(63, 0, 191, 0.75)
    # @overload mix(color1, color2, weight: 50%)
    #   @param color1 [Color]
    #   @param color2 [Color]
    #   @param weight [Number] between 0% and 100%
    #   @return [Color]
    #   @raise [ArgumentError] if `color1` or `color2` aren't colors,
    #     or `weight` isn't a number between 0% and 100%
    def mix(color1, color2, weight = Number.new(50))
      assert_type color1, :Color
      assert_type color2, :Color
      assert_type weight, :Number

      unless (0..100).include?(weight.value)
        raise ArgumentError.new("Weight #{weight} must be between 0% and 100%")
      end

      # This algorithm factors in both the user-provided weight
      # and the difference between the alpha values of the two colors
      # to decide how to perform the weighted average of the two RGB values.
      #
      # It works by first normalizing both parameters to be within [-1, 1],
      # where 1 indicates "only use color1", -1 indicates "only use color 0",
      # and all values in between indicated a proportionately weighted average.
      #
      # Once we have the normalized variables w and a,
      # we apply the formula (w + a)/(1 + w*a)
      # to get the combined weight (in [-1, 1]) of color1.
      # This formula has two especially nice properties:
      #
      #   * When either w or a are -1 or 1, the combined weight is also that number
      #     (cases where w * a == -1 are undefined, and handled as a special case).
      #
      #   * When a is 0, the combined weight is w, and vice versa
      #
      # Finally, the weight of color1 is renormalized to be within [0, 1]
      # and the weight of color2 is given by 1 minus the weight of color1.
      p = weight.value/100.0
      w = p*2 - 1
      a = color1.alpha - color2.alpha

      w1 = (((w * a == -1) ? w : (w + a)/(1 + w*a)) + 1)/2.0
      w2 = 1 - w1

      rgb = color1.rgb.zip(color2.rgb).map {|v1, v2| v1*w1 + v2*w2}
      alpha = color1.alpha*p + color2.alpha*(1-p)
      Color.new(rgb + [alpha])
    end
    declare :mix, [:color_1, :color_2]
    declare :mix, [:color_1, :color_2, :weight]

    # Converts a color to grayscale.
    # This is identical to `desaturate(color, 100%)`.
    #
    # @param color [Color]
    # @return [Color]
    # @raise [ArgumentError] if `color` isn't a color
    # @see #desaturate
    def grayscale(color)
      desaturate color, Number.new(100)
    end
    declare :grayscale, [:color]

    # Returns the complement of a color.
    # This is identical to `adjust-hue(color, 180deg)`.
    #
    # @param color [Color]
    # @return [Color]
    # @raise [ArgumentError] if `color` isn't a color
    # @see #adjust_hue #adjust-hue
    def complement(color)
      adjust_hue color, Number.new(180)
    end
    declare :complement, [:color]

    # Returns the inverse (negative) of a color.
    # The red, green, and blue values are inverted, while the opacity is left alone.
    #
    # @param color [Color]
    # @return [Color]
    # @raise [ArgumentError] if `color` isn't a color
    def invert(color)
      assert_type color, :Color
      color.with(
        :red => (255 - color.red),
        :green => (255 - color.green),
        :blue => (255 - color.blue))
    end

    # Removes quotes from a string if the string is quoted,
    # or returns the same string if it's not.
    #
    # @param string [String]
    # @return [String]
    # @raise [ArgumentError] if `string` isn't a string
    # @see #quote
    # @example
    #   unquote("foo") => foo
    #   unquote(foo) => foo
    def unquote(string)
      if string.is_a?(Sass::Script::String)
        Sass::Script::String.new(string.value, :identifier)
      else
        string
      end
    end
    declare :unquote, [:string]

    # Add quotes to a string if the string isn't quoted,
    # or returns the same string if it is.
    #
    # @param string [String]
    # @return [String]
    # @raise [ArgumentError] if `string` isn't a string
    # @see #unquote
    # @example
    #   quote("foo") => "foo"
    #   quote(foo) => "foo"
    def quote(string)
      assert_type string, :String
      Sass::Script::String.new(string.value, :string)
    end
    declare :quote, [:string]

    # Inspects the type of the argument, returning it as an unquoted string.
    #
    # @example
    #   type-of(100px)  => number
    #   type-of(asdf)   => string
    #   type-of("asdf") => string
    #   type-of(true)   => bool
    #   type-of(#fff)   => color
    #   type-of(blue)   => color
    # @param value [Literal] The object to inspect
    # @return [String] The unquoted string name of the literal's type
    def type_of(value)
      Sass::Script::String.new(value.class.name.gsub(/Sass::Script::/,'').downcase)
    end
    declare :type_of, [:value]

    # Inspects the unit of the number, returning it as a quoted string.
    # Complex units are sorted in alphabetical order by numerator and denominator.
    #
    # @example
    #   unit(100) => ""
    #   unit(100px) => "px"
    #   unit(3em) => "em"
    #   unit(10px * 5em) => "em*px"
    #   unit(10px * 5em / 30cm / 1rem) => "em*px/cm*rem"
    # @param number [Literal] The number to inspect
    # @return [String] The unit(s) of the number
    # @raise [ArgumentError] if `number` isn't a number
    def unit(number)
      assert_type number, :Number
      Sass::Script::String.new(number.unit_str, :string)
    end
    declare :unit, [:number]

    # Inspects the unit of the number, returning a boolean indicating if it is unitless.
    #
    # @example
    #   unitless(100) => true
    #   unitless(100px) => false
    # @param number [Literal] The number to inspect
    # @return [Bool] Whether or not the number is unitless
    # @raise [ArgumentError] if `number` isn't a number
    def unitless(number)
      assert_type number, :Number
      Sass::Script::Bool.new(number.unitless?)
    end
    declare :unitless, [:number]

    # Returns true if two numbers are similar enough to be added, subtracted, or compared.
    #
    # @example
    #   comparable(2px, 1px) => true
    #   comparable(100px, 3em) => false
    #   comparable(10cm, 3mm) => true
    # @param number_1 [Number]
    # @param number_2 [Number]
    # @return [Bool] indicating if the numbers can be compared.
    # @raise [ArgumentError] if `number_1` or `number_2` aren't numbers
    def comparable(number_1, number_2)
      assert_type number_1, :Number
      assert_type number_2, :Number
      Sass::Script::Bool.new(number_1.comparable_to?(number_2))
    end
    declare :comparable, [:number_1, :number_2]

    # Converts a decimal number to a percentage.
    #
    # @example
    #   percentage(100px / 50px) => 200%
    # @param value [Number] The decimal number to convert to a percentage
    # @return [Number] The percentage
    # @raise [ArgumentError] If `value` isn't a unitless number
    def percentage(value)
      unless value.is_a?(Sass::Script::Number) && value.unitless?
        raise ArgumentError.new("#{value.inspect} is not a unitless number")
      end
      Sass::Script::Number.new(value.value * 100, ['%'])
    end
    declare :percentage, [:value]

    # Rounds a number to the nearest whole number.
    #
    # @example
    #   round(10.4px) => 10px
    #   round(10.6px) => 11px
    # @param value [Number] The number
    # @return [Number] The rounded number
    # @raise [ArgumentError] if `value` isn't a number
    def round(value)
      numeric_transformation(value) {|n| n.round}
    end
    declare :round, [:value]

    # Rounds a number up to the nearest whole number.
    #
    # @example
    #   ciel(10.4px) => 11px
    #   ciel(10.6px) => 11px
    # @param value [Number] The number
    # @return [Number] The rounded number
    # @raise [ArgumentError] if `value` isn't a number
    def ceil(value)
      numeric_transformation(value) {|n| n.ceil}
    end
    declare :ceil, [:value]

    # Rounds down to the nearest whole number.
    #
    # @example
    #   floor(10.4px) => 10px
    #   floor(10.6px) => 10px
    # @param value [Number] The number
    # @return [Number] The rounded number
    # @raise [ArgumentError] if `value` isn't a number
    def floor(value)
      numeric_transformation(value) {|n| n.floor}
    end
    declare :floor, [:value]

    # Finds the absolute value of a number.
    #
    # @example
    #   abs(10px) => 10px
    #   abs(-10px) => 10px
    # @param value [Number] The number
    # @return [Number] The absolute value
    # @raise [ArgumentError] if `value` isn't a number
    def abs(value)
      numeric_transformation(value) {|n| n.abs}
    end
    declare :abs, [:value]

    # Return the length of a list.
    #
    # @example
    #   length(10px) => 1
    #   length(10px 20px 30px) => 3
    # @param list [Literal] The list
    # @return [Number] The length
    def length(list)
      Sass::Script::Number.new(list.to_a.size)
    end
    declare :length, [:list]

    # Gets the nth item in a list.
    #
    # Note that unlike some languages, the first item in a Sass list is number 1,
    # the second number 2, and so forth.
    #
    # @example
    #   nth(10px 20px 30px, 1) => 10px
    #   nth((Helvetica, Arial, sans-serif), 3) => sans-serif
    # @param list [Literal] The list
    # @param n [Number] The index into the list
    # @return [Literal] The nth item in the list
    # @raise [ArgumentError] If `n` isn't an integer between 1 and the list's length.
    def nth(list, n)
      assert_type n, :Number
      if !n.int?
        raise ArgumentError.new("List index #{n} must be an integer")
      elsif n.to_i < 1
        raise ArgumentError.new("List index #{n} must be greater than or equal to 1")
      elsif list.to_a.size == 0
        raise ArgumentError.new("List index is #{n} but list has no items")
      elsif n.to_i > (size = list.to_a.size)
        raise ArgumentError.new("List index is #{n} but list is only #{size} item#{'s' if size != 1} long")
      end

      list.to_a[n.to_i - 1]
    end
    declare :nth, [:list, :n]

    # Joins together two lists into a new list.
    #
    # Unless the `$separator` argument is passed,
    # if one list is comma-separated and one is space-separated,
    # the first parameter's separator is used for the resulting list.
    # If the lists have only one item each, spaces are used for the resulting list.
    #
    # @example
    #   join(10px 20px, 30px 40px) => 10px 20px 30px 40px
    #   join((blue, red), (#abc, #def)) => blue, red, #abc, #def
    #   join(10px, 20px) => 10px 20px
    #   join(10px, 20px, comma) => 10px, 20px
    #   join((blue, red), (#abc, #def), space) => blue red #abc #def
    # @overload join(list1, list2, separator: auto)
    #   @param list1 [Literal] The first list to join
    #   @param list2 [Literal] The second list to join
    #   @param separator [String] How the list separator (comma or space) should be determined.
    #     If this is `comma` or `space`, that is always the separator;
    #     if this is `auto` (the default), the separator is determined as explained above.
    def join(list1, list2, separator = Sass::Script::String.new("auto"))
      assert_type separator, :String
      unless %w[auto space comma].include?(separator.value)
        raise ArgumentError.new("Separator name must be space, comma, or auto")
      end
      sep1 = list1.separator if list1.is_a?(Sass::Script::List) && !list1.value.empty?
      sep2 = list2.separator if list2.is_a?(Sass::Script::List) && !list2.value.empty?
      Sass::Script::List.new(
        list1.to_a + list2.to_a,
        if separator.value == 'auto'
          sep1 || sep2 || :space
        else
          separator.value.to_sym
        end)
    end
    declare :join, [:list1, :list2]
    declare :join, [:list1, :list2, :separator]

    # Appends a single value onto the end of a list.
    #
    # Unless the `$separator` argument is passed,
    # if the list has only one item,
    # the resulting list will be space-separated.
    #
    # @example
    #   append(10px 20px, 30px) => 10px 20px 30px
    #   append((blue, red), green) => blue, red, green
    #   append(10px 20px, 30px 40px) => 10px 20px (30px 40px)
    #   join(10px, 20px, comma) => 10px, 20px
    #   join((blue, red), green, space) => blue red green
    # @overload join(list, val, separator: auto)
    #   @param list1 [Literal] The first list to join
    #   @param list2 [Literal] The second list to join
    #   @param separator [String] How the list separator (comma or space) should be determined.
    #     If this is `comma` or `space`, that is always the separator;
    #     if this is `auto` (the default), the separator is determined as explained above.
    def append(list, val, separator = Sass::Script::String.new("auto"))
      assert_type separator, :String
      unless %w[auto space comma].include?(separator.value)
        raise ArgumentError.new("Separator name must be space, comma, or auto")
      end
      sep = list.separator if list.is_a?(Sass::Script::List)
      Sass::Script::List.new(
        list.to_a + [val],
        if separator.value == 'auto'
          sep || :space
        else
          separator.value.to_sym
        end)
    end
    declare :append, [:list, :val]
    declare :append, [:list, :val, :separator]

    # Returns one of two values based on the truth value of the first argument.
    #
    # @example
    #   if(true, 1px, 2px) => 1px
    #   if(false, 1px, 2px) => 2px
    # @param condition [Bool] Whether the first or second value will be returned.
    # @param if_true [Literal] The value that will be returned if `$condition` is true.
    # @param if_false [Literal] The value that will be returned if `$condition` is false.
    def if(condition, if_true, if_false)
      if condition.to_bool
        if_true
      else
        if_false
      end
    end
    declare :if, [:condition, :if_true, :if_false]

    private

    # This method implements the pattern of transforming a numeric value into
    # another numeric value with the same units.
    # It yields a number to a block to perform the operation and return a number
    def numeric_transformation(value)
      assert_type value, :Number
      Sass::Script::Number.new(yield(value.value), value.numerator_units, value.denominator_units)
    end

    def _adjust(color, amount, attr, range, op, units = "")
      assert_type color, :Color
      assert_type amount, :Number
      unless range.include?(amount.value)
        raise ArgumentError.new("Amount #{amount} must be between #{range.first}#{units} and #{range.last}#{units}")
      end

      # TODO: is it worth restricting here,
      # or should we do so in the Color constructor itself,
      # and allow clipping in rgb() et al?
      color.with(attr => Sass::Util.restrict(
          color.send(attr).send(op, amount.value), range))
    end
  end
end

module Sass
  module Script
    # A SassScript parse node representing a function call.
    #
    # A function call either calls one of the functions in {Script::Functions},
    # or if no function with the given name exists
    # it returns a string representation of the function call.
    class Funcall < Node
      # The name of the function.
      #
      # @return [String]
      attr_reader :name

      # The arguments to the function.
      #
      # @return [Array<Script::Node>]
      attr_reader :args

      # The keyword arguments to the function.
      #
      # @return [{String => Script::Node}]
      attr_reader :keywords

      # @param name [String] See \{#name}
      # @param args [Array<Script::Node>] See \{#args}
      # @param keywords [{String => Script::Node}] See \{#keywords}
      def initialize(name, args, keywords)
        @name = name
        @args = args
        @keywords = keywords
        super()
      end

      # @return [String] A string representation of the function call
      def inspect
        args = @args.map {|a| a.inspect}.join(', ')
        keywords = @keywords.sort_by {|k, v| k}.
            map {|k, v| "$#{k}: #{v.inspect}"}.join(', ')
        "#{name}(#{args}#{', ' unless args.empty? || keywords.empty?}#{keywords})"
      end

      # @see Node#to_sass
      def to_sass(opts = {})
        args = @args.map {|a| a.to_sass(opts)}.join(', ')
        keywords = @keywords.sort_by {|k, v| k}.
          map {|k, v| "$#{dasherize(k, opts)}: #{v.to_sass(opts)}"}.join(', ')
        "#{dasherize(name, opts)}(#{args}#{', ' unless args.empty? || keywords.empty?}#{keywords})"
      end

      # Returns the arguments to the function.
      #
      # @return [Array<Node>]
      # @see Node#children
      def children
        @args + @keywords.values
      end

      protected

      # Evaluates the function call.
      #
      # @param environment [Sass::Environment] The environment in which to evaluate the SassScript
      # @return [Literal] The SassScript object that is the value of the function call
      # @raise [Sass::SyntaxError] if the function call raises an ArgumentError
      def _perform(environment)
        args = @args.map {|a| a.perform(environment)}
        if fn = environment.function(@name)
          keywords = Sass::Util.map_hash(@keywords) {|k, v| [k, v.perform(environment)]}
          return perform_sass_fn(fn, args, keywords)
        end

        ruby_name = @name.tr('-', '_')
        args = construct_ruby_args(ruby_name, args, environment)

        unless Functions.callable?(ruby_name)
          opts(to_literal(args))
        else
          opts(Functions::EvaluationContext.new(environment.options).send(ruby_name, *args))
        end
      rescue ArgumentError => e
        raise e unless e.backtrace.any? {|t| t =~ /:in `(block in )?(#{name}|perform)'$/}
        raise Sass::SyntaxError.new("#{e.message} for `#{name}'")
      end

      # This method is factored out from `_perform` so that compass can override
      # it with a cross-browser implementation for functions that require vendor prefixes
      # in the generated css.
      def to_literal(args)
        Script::String.new("#{name}(#{args.join(', ')})")
      end

      private

      def construct_ruby_args(name, args, environment)
        unless signature = Functions.signature(name.to_sym, args.size, @keywords.size)
          return args if keywords.empty?
          raise Sass::SyntaxError.new("Function #{name} doesn't support keyword arguments")
        end
        keywords = Sass::Util.map_hash(@keywords) {|k, v| [k, v.perform(environment)]}

        # If the user passes more non-keyword args than the function expects,
        # but it does expect keyword args, Ruby's arg handling won't raise an error.
        # Since we don't want to make functions think about this,
        # we'll handle it for them here.
        if signature.var_kwargs && !signature.var_args && args.size > signature.args.size
          raise Sass::SyntaxError.new(
            "#{args[signature.args.size].inspect} is not a keyword argument for `#{name}'")
        elsif keywords.empty?
          return args 
        end

        args = args + signature.args[args.size..-1].map do |argname|
          if keywords.has_key?(argname)
            keywords.delete(argname)
          else
            raise Sass::SyntaxError.new("Function #{name} requires an argument named $#{argname}")
          end
        end

        if keywords.size > 0
          if signature.var_kwargs
            args << keywords
          else
            raise Sass::SyntaxError.new("Function #{name} doesn't take an argument named $#{keywords.keys.sort.first}")
          end
        end

        args
      end

      def perform_sass_fn(function, args, keywords)
        # TODO: merge with mixin arg evaluation?
        keywords.each do |name, value|
          # TODO: Make this fast
          unless function.args.find {|(var, default)| var.underscored_name == name}
            raise Sass::SyntaxError.new("Function #{@name} doesn't have an argument named $#{name}")
          end
        end

        if args.size > function.args.size
          raise ArgumentError.new("Wrong number of arguments (#{args.size} for #{function.args.size})")
        end

        environment = function.args.zip(args).
          inject(Sass::Environment.new(function.environment)) do |env, ((var, default), value)|
          env.set_local_var(var.name,
            value || keywords[var.underscored_name] || (default && default.perform(env)))
          raise Sass::SyntaxError.new("Function #{@name} is missing parameter #{var.inspect}.") unless env.var(var.name)
          env
        end

        val = catch :_sass_return do
          function.tree.each {|c| Sass::Tree::Visitors::Perform.visit(c, environment)}
          raise Sass::SyntaxError.new("Function #{@name} finished without @return")
        end
        val
      end
    end
  end
end
require 'set'
module Sass::Script
  # The abstract superclass for SassScript objects.
  #
  # Many of these methods, especially the ones that correspond to SassScript operations,
  # are designed to be overridden by subclasses which may change the semantics somewhat.
  # The operations listed here are just the defaults.
  class Literal < Node

module Sass::Script
  # A SassScript object representing a number.
  # SassScript numbers can have decimal values,
  # and can also have units.
  # For example, `12`, `1px`, and `10.45em`
  # are all valid values.
  #
  # Numbers can also have more complex units, such as `1px*em/in`.
  # These cannot be inputted directly in Sass code at the moment.
  class Number < Literal
    # The Ruby value of the number.
    #
    # @return [Numeric]
    attr_reader :value

    # A list of units in the numerator of the number.
    # For example, `1px*em/in*cm` would return `["px", "em"]`
    # @return [Array<String>] 
    attr_reader :numerator_units

    # A list of units in the denominator of the number.
    # For example, `1px*em/in*cm` would return `["in", "cm"]`
    # @return [Array<String>]
    attr_reader :denominator_units

    # The original representation of this number.
    # For example, although the result of `1px/2px` is `0.5`,
    # the value of `#original` is `"1px/2px"`.
    #
    # This is only non-nil when the original value should be used as the CSS value,
    # as in `font: 1px/2px`.
    #
    # @return [Boolean, nil]
    attr_accessor :original

    # The precision with which numbers will be printed to CSS files.
    # For example, if this is `1000.0`,
    # `3.1415926` will be printed as `3.142`.
    # @api public
    PRECISION = 1000.0

    # Used so we don't allocate two new arrays for each new number.
    NO_UNITS  = []

    # @param value [Numeric] The value of the number
    # @param numerator_units [Array<String>] See \{#numerator\_units}
    # @param denominator_units [Array<String>] See \{#denominator\_units}
    def initialize(value, numerator_units = NO_UNITS, denominator_units = NO_UNITS)
      super(value)
      @numerator_units = numerator_units
      @denominator_units = denominator_units
      normalize!
    end

    # The SassScript `+` operation.
    # Its functionality depends on the type of its argument:
    #
    # {Number}
    # : Adds the two numbers together, converting units if possible.
    #
    # {Color}
    # : Adds this number to each of the RGB color channels.
    #
    # {Literal}
    # : See {Literal#plus}.
    #
    # @param other [Literal] The right-hand side of the operator
    # @return [Literal] The result of the operation
    # @raise [Sass::UnitConversionError] if `other` is a number with incompatible units
    def plus(other)
      if other.is_a? Number
        operate(other, :+)
      elsif other.is_a?(Color)
        other.plus(self)
      else
        super
      end
    end

    # The SassScript binary `-` operation (e.g. `$a - $b`).
    # Its functionality depends on the type of its argument:
    #
    # {Number}
    # : Subtracts this number from the other, converting units if possible.
    #
    # {Literal}
    # : See {Literal#minus}.
    #
    # @param other [Literal] The right-hand side of the operator
    # @return [Literal] The result of the operation
    # @raise [Sass::UnitConversionError] if `other` is a number with incompatible units
    def minus(other)
      if other.is_a? Number
        operate(other, :-)
      else
        super
      end
    end

    # The SassScript unary `+` operation (e.g. `+$a`).
    #
    # @return [Number] The value of this number
    def unary_plus
      self
    end

    # The SassScript unary `-` operation (e.g. `-$a`).
    #
    # @return [Number] The negative value of this number
    def unary_minus
      Number.new(-value, @numerator_units, @denominator_units)
    end

    # The SassScript `*` operation.
    # Its functionality depends on the type of its argument:
    #
    # {Number}
    # : Multiplies the two numbers together, converting units appropriately.
    #
    # {Color}
    # : Multiplies each of the RGB color channels by this number.
    #
    # @param other [Number, Color] The right-hand side of the operator
    # @return [Number, Color] The result of the operation
    # @raise [NoMethodError] if `other` is an invalid type
    def times(other)
      if other.is_a? Number
        operate(other, :*)
      elsif other.is_a? Color
        other.times(self)
      else
        raise NoMethodError.new(nil, :times)
      end
    end

    # The SassScript `/` operation.
    # Its functionality depends on the type of its argument:
    #
    # {Number}
    # : Divides this number by the other, converting units appropriately.
    #
    # {Literal}
    # : See {Literal#div}.
    #
    # @param other [Literal] The right-hand side of the operator
    # @return [Literal] The result of the operation
    def div(other)
      if other.is_a? Number
        res = operate(other, :/)
        if self.original && other.original
          res.original = "#{self.original}/#{other.original}"
        end
        res
      else
        super
      end
    end

    # The SassScript `%` operation.
    #
    # @param other [Number] The right-hand side of the operator
    # @return [Number] This number modulo the other
    # @raise [NoMethodError] if `other` is an invalid type
    # @raise [Sass::UnitConversionError] if `other` has any units
    def mod(other)
      if other.is_a?(Number)
        unless other.unitless?
          raise Sass::UnitConversionError.new("Cannot modulo by a number with units: #{other.inspect}.")
        end
        operate(other, :%)
      else
        raise NoMethodError.new(nil, :mod)
      end
    end

    # The SassScript `==` operation.
    #
    # @param other [Literal] The right-hand side of the operator
    # @return [Boolean] Whether this number is equal to the other object
    def eq(other)
      return Sass::Script::Bool.new(false) unless other.is_a?(Sass::Script::Number)
      this = self
      begin
        if unitless?
          this = this.coerce(other.numerator_units, other.denominator_units)
        else
          other = other.coerce(@numerator_units, @denominator_units)
        end
      rescue Sass::UnitConversionError
        return Sass::Script::Bool.new(false)
      end

      Sass::Script::Bool.new(this.value == other.value)
    end

    # The SassScript `>` operation.
    #
    # @param other [Number] The right-hand side of the operator
    # @return [Boolean] Whether this number is greater than the other
    # @raise [NoMethodError] if `other` is an invalid type
    def gt(other)
      raise NoMethodError.new(nil, :gt) unless other.is_a?(Number)
      operate(other, :>)
    end

    # The SassScript `>=` operation.
    #
    # @param other [Number] The right-hand side of the operator
    # @return [Boolean] Whether this number is greater than or equal to the other
    # @raise [NoMethodError] if `other` is an invalid type
    def gte(other)
      raise NoMethodError.new(nil, :gte) unless other.is_a?(Number)
      operate(other, :>=)
    end

    # The SassScript `<` operation.
    #
    # @param other [Number] The right-hand side of the operator
    # @return [Boolean] Whether this number is less than the other
    # @raise [NoMethodError] if `other` is an invalid type
    def lt(other)
      raise NoMethodError.new(nil, :lt) unless other.is_a?(Number)
      operate(other, :<)
    end

    # The SassScript `<=` operation.
    #
    # @param other [Number] The right-hand side of the operator
    # @return [Boolean] Whether this number is less than or equal to the other
    # @raise [NoMethodError] if `other` is an invalid type
    def lte(other)
      raise NoMethodError.new(nil, :lte) unless other.is_a?(Number)
      operate(other, :<=)
    end

    # @return [String] The CSS representation of this number
    # @raise [Sass::SyntaxError] if this number has units that can't be used in CSS
    #   (e.g. `px*in`)
    def to_s(opts = {})
      return original if original
      raise Sass::SyntaxError.new("#{inspect} isn't a valid CSS value.") unless legal_units?
      inspect
    end

    # Returns a readable representation of this number.
    #
    # This representation is valid CSS (and valid SassScript)
    # as long as there is only one unit.
    #
    # @return [String] The representation
    def inspect(opts = {})
      value = self.class.round(self.value)
      unitless? ? value.to_s : "#{value}#{unit_str}"
    end
    alias_method :to_sass, :inspect

    # @return [Fixnum] The integer value of the number
    # @raise [Sass::SyntaxError] if the number isn't an integer
    def to_i
      super unless int?
      return value
    end

    # @return [Boolean] Whether or not this number is an integer.
    def int?
      value % 1 == 0.0
    end

    # @return [Boolean] Whether or not this number has no units.
    def unitless?
      @numerator_units.empty? && @denominator_units.empty?
    end

    # @return [Boolean] Whether or not this number has units that can be represented in CSS
    #   (that is, zero or one \{#numerator\_units}).
    def legal_units?
      (@numerator_units.empty? || @numerator_units.size == 1) && @denominator_units.empty?
    end

    # Returns this number converted to other units.
    # The conversion takes into account the relationship between e.g. mm and cm,
    # as well as between e.g. in and cm.
    #
    # If this number has no units, it will simply return itself
    # with the given units.
    #
    # An incompatible coercion, e.g. between px and cm, will raise an error.
    #
    # @param num_units [Array<String>] The numerator units to coerce this number into.
    #   See {\#numerator\_units}
    # @param den_units [Array<String>] The denominator units to coerce this number into.
    #   See {\#denominator\_units}
    # @return [Number] The number with the new units
    # @raise [Sass::UnitConversionError] if the given units are incompatible with the number's
    #   current units
    def coerce(num_units, den_units)
      Number.new(if unitless?
                   self.value
                 else
                   self.value * coercion_factor(@numerator_units, num_units) /
                     coercion_factor(@denominator_units, den_units)
                 end, num_units, den_units)
    end

    # @param other [Number] A number to decide if it can be compared with this number.
    # @return [Boolean] Whether or not this number can be compared with the other.
    def comparable_to?(other)
      begin
        operate(other, :+)
        true
      rescue Sass::UnitConversionError
        false
      end
    end

    # Returns a human readable representation of the units in this number.
    # For complex units this takes the form of:
    # numerator_unit1 * numerator_unit2 / denominator_unit1 * denominator_unit2
    # @return [String] a string that represents the units in this number
    def unit_str
      rv = @numerator_units.sort.join("*")
      if @denominator_units.any?
        rv << "/"
        rv << @denominator_units.sort.join("*")
      end
      rv
    end

    private

    # @private
    def self.round(num)
      if num.is_a?(Float) && (num.infinite? || num.nan?)
        num
      elsif num % 1 == 0.0
        num.to_i
      else
        (num * PRECISION).round / PRECISION
      end
    end

    OPERATIONS = [:+, :-, :<=, :<, :>, :>=]

    def operate(other, operation)
      this = self
      if OPERATIONS.include?(operation)
        if unitless?
          this = this.coerce(other.numerator_units, other.denominator_units)
        else
          other = other.coerce(@numerator_units, @denominator_units)
        end
      end
      # avoid integer division
      value = (:/ == operation) ? this.value.to_f : this.value
      result = value.send(operation, other.value)

      if result.is_a?(Numeric)
        Number.new(result, *compute_units(this, other, operation))
      else # Boolean op
        Bool.new(result)
      end
    end

    def coercion_factor(from_units, to_units)
      # get a list of unmatched units
      from_units, to_units = sans_common_units(from_units, to_units)

      if from_units.size != to_units.size || !convertable?(from_units | to_units)
        raise Sass::UnitConversionError.new("Incompatible units: '#{from_units.join('*')}' and '#{to_units.join('*')}'.")
      end

      from_units.zip(to_units).inject(1) {|m,p| m * conversion_factor(p[0], p[1]) }
    end

    def compute_units(this, other, operation)
      case operation
      when :*
        [this.numerator_units + other.numerator_units, this.denominator_units + other.denominator_units]
      when :/
        [this.numerator_units + other.denominator_units, this.denominator_units + other.numerator_units]
      else  
        [this.numerator_units, this.denominator_units]
      end
    end

    def normalize!
      return if unitless?
      @numerator_units, @denominator_units = sans_common_units(@numerator_units, @denominator_units)

      @denominator_units.each_with_index do |d, i|
        if convertable?(d) && (u = @numerator_units.detect(&method(:convertable?)))
          @value /= conversion_factor(d, u)
          @denominator_units.delete_at(i)
          @numerator_units.delete_at(@numerator_units.index(u))
        end
      end
    end

    # A hash of unit names to their index in the conversion table
    CONVERTABLE_UNITS = {"in" => 0,        "cm" => 1,    "pc" => 2,    "mm" => 3,   "pt" => 4}
    CONVERSION_TABLE = [[ 1,                2.54,         6,            25.4,        72        ], # in
                        [ nil,              1,            2.36220473,   10,          28.3464567], # cm
                        [ nil,              nil,          1,            4.23333333,  12        ], # pc
                        [ nil,              nil,          nil,          1,           2.83464567], # mm
                        [ nil,              nil,          nil,          nil,         1         ]] # pt

    def conversion_factor(from_unit, to_unit)
      res = CONVERSION_TABLE[CONVERTABLE_UNITS[from_unit]][CONVERTABLE_UNITS[to_unit]]
      return 1.0 / conversion_factor(to_unit, from_unit) if res.nil?
      res
    end

    def convertable?(units)
      Array(units).all? {|u| CONVERTABLE_UNITS.include?(u)}
    end

    def sans_common_units(units1, units2)
      units2 = units2.dup
      # Can't just use -, because we want px*px to coerce properly to px*mm
      return units1.map do |u|
        next u unless j = units2.index(u)
        units2.delete_at(j)
        nil
      end.compact, units2
    end
  end
end

module Sass::Script
  # A SassScript object representing a CSS color.
  #
  # A color may be represented internally as RGBA, HSLA, or both.
  # It's originally represented as whatever its input is;
  # if it's created with RGB values, it's represented as RGBA,
  # and if it's created with HSL values, it's represented as HSLA.
  # Once a property is accessed that requires the other representation --
  # for example, \{#red} for an HSL color --
  # that component is calculated and cached.
  #
  # The alpha channel of a color is independent of its RGB or HSL representation.
  # It's always stored, as 1 if nothing else is specified.
  # If only the alpha channel is modified using \{#with},
  # the cached RGB and HSL values are retained.
  class Color < Literal
    class << self; include Sass::Util; end

    # A hash from color names to `[red, green, blue]` value arrays.
    HTML4_COLORS = map_vals({
        'black'   => 0x000000,
        'silver'  => 0xc0c0c0,
        'gray'    => 0x808080,
        'white'   => 0xffffff,
        'maroon'  => 0x800000,
        'red'     => 0xff0000,
        'purple'  => 0x800080,
        'fuchsia' => 0xff00ff,
        'green'   => 0x008000,
        'lime'    => 0x00ff00,
        'olive'   => 0x808000,
        'yellow'  => 0xffff00,
        'navy'    => 0x000080,
        'blue'    => 0x0000ff,
        'teal'    => 0x008080,
        'aqua'    => 0x00ffff
      }) {|color| (0..2).map {|n| color >> (n << 3) & 0xff}.reverse}
    # A hash from `[red, green, blue]` value arrays to color names.
    HTML4_COLORS_REVERSE = map_hash(HTML4_COLORS) {|k, v| [v, k]}

    # Constructs an RGB or HSL color object,
    # optionally with an alpha channel.
    # 
    # The RGB values must be between 0 and 255.
    # The saturation and lightness values must be between 0 and 100.
    # The alpha value must be between 0 and 1.
    #
    # @raise [Sass::SyntaxError] if any color value isn't in the specified range
    #
    # @overload initialize(attrs)
    #   The attributes are specified as a hash.
    #   This hash must contain either `:hue`, `:saturation`, and `:value` keys,
    #   or `:red`, `:green`, and `:blue` keys.
    #   It cannot contain both HSL and RGB keys.
    #   It may also optionally contain an `:alpha` key.
    #
    #   @param attrs [{Symbol => Numeric}] A hash of color attributes to values
    #   @raise [ArgumentError] if not enough attributes are specified,
    #     or both RGB and HSL attributes are specified
    #
    # @overload initialize(rgba)
    #   The attributes are specified as an array.
    #   This overload only supports RGB or RGBA colors.
    #
    #   @param rgba [Array<Numeric>] A three- or four-element array
    #     of the red, green, blue, and optionally alpha values (respectively)
    #     of the color
    #   @raise [ArgumentError] if not enough attributes are specified
    def initialize(attrs, allow_both_rgb_and_hsl = false)
      super(nil)

      if attrs.is_a?(Array)
        unless (3..4).include?(attrs.size)
          raise ArgumentError.new("Color.new(array) expects a three- or four-element array")
        end

        red, green, blue = attrs[0...3].map {|c| c.to_i}
        @attrs = {:red => red, :green => green, :blue => blue}
        @attrs[:alpha] = attrs[3] ? attrs[3].to_f : 1
      else
        attrs = attrs.reject {|k, v| v.nil?}
        hsl = [:hue, :saturation, :lightness] & attrs.keys
        rgb = [:red, :green, :blue] & attrs.keys
        if !allow_both_rgb_and_hsl && !hsl.empty? && !rgb.empty?
          raise ArgumentError.new("Color.new(hash) may not have both HSL and RGB keys specified")
        elsif hsl.empty? && rgb.empty?
          raise ArgumentError.new("Color.new(hash) must have either HSL or RGB keys specified")
        elsif !hsl.empty? && hsl.size != 3
          raise ArgumentError.new("Color.new(hash) must have all three HSL values specified")
        elsif !rgb.empty? && rgb.size != 3
          raise ArgumentError.new("Color.new(hash) must have all three RGB values specified")
        end

        @attrs = attrs
        @attrs[:hue] %= 360 if @attrs[:hue]
        @attrs[:alpha] ||= 1
      end

      [:red, :green, :blue].each do |k|
        next if @attrs[k].nil?
        @attrs[k] = @attrs[k].to_i
        next if (0..255).include?(@attrs[k])
        raise ArgumentError.new("#{k.to_s.capitalize} value must be between 0 and 255")
      end

      [:saturation, :lightness].each do |k|
        next if @attrs[k].nil?
        @attrs[k] = 0 if @attrs[k] < 0.00001 && @attrs[k] > -0.00001
        @attrs[k] = 100 if @attrs[k] - 100 < 0.00001 && @attrs[k] - 100 > -0.00001
        next if (0..100).include?(@attrs[k])
        raise ArgumentError.new("#{k.to_s.capitalize} must be between 0 and 100")
      end

      unless (0..1).include?(@attrs[:alpha])
        raise ArgumentError.new("Alpha channel must be between 0 and 1")
      end
    end

    # The red component of the color.
    #
    # @return [Fixnum]
    def red
      hsl_to_rgb!
      @attrs[:red]
    end

    # The green component of the color.
    #
    # @return [Fixnum]
    def green
      hsl_to_rgb!
      @attrs[:green]
    end

    # The blue component of the color.
    #
    # @return [Fixnum]
    def blue
      hsl_to_rgb!
      @attrs[:blue]
    end

    # The hue component of the color.
    #
    # @return [Numeric]
    def hue
      rgb_to_hsl!
      @attrs[:hue]
    end

    # The saturation component of the color.
    #
    # @return [Numeric]
    def saturation
      rgb_to_hsl!
      @attrs[:saturation]
    end

    # The lightness component of the color.
    #
    # @return [Numeric]
    def lightness
      rgb_to_hsl!
      @attrs[:lightness]
    end

    # The alpha channel (opacity) of the color.
    # This is 1 unless otherwise defined.
    #
    # @return [Fixnum]
    def alpha
      @attrs[:alpha]
    end

    # Returns whether this color object is translucent;
    # that is, whether the alpha channel is non-1.
    #
    # @return [Boolean]
    def alpha?
      alpha < 1
    end

    # Returns the red, green, and blue components of the color.
    #
    # @return [Array<Fixnum>] A frozen three-element array of the red, green, and blue
    #   values (respectively) of the color
    def rgb
      [red, green, blue].freeze
    end

    # Returns the hue, saturation, and lightness components of the color.
    #
    # @return [Array<Fixnum>] A frozen three-element array of the
    #   hue, saturation, and lightness values (respectively) of the color
    def hsl
      [hue, saturation, lightness].freeze
    end

    # The SassScript `==` operation.
    # **Note that this returns a {Sass::Script::Bool} object,
    # not a Ruby boolean**.
    #
    # @param other [Literal] The right-hand side of the operator
    # @return [Bool] True if this literal is the same as the other,
    #   false otherwise
    def eq(other)
      Sass::Script::Bool.new(
        other.is_a?(Color) && rgb == other.rgb && alpha == other.alpha)
    end

    # Returns a copy of this color with one or more channels changed.
    # RGB or HSL colors may be changed, but not both at once.
    #
    # For example:
    #
    #     Color.new([10, 20, 30]).with(:blue => 40)
    #       #=> rgb(10, 40, 30)
    #     Color.new([126, 126, 126]).with(:red => 0, :green => 255)
    #       #=> rgb(0, 255, 126)
    #     Color.new([255, 0, 127]).with(:saturation => 60)
    #       #=> rgb(204, 51, 127)
    #     Color.new([1, 2, 3]).with(:alpha => 0.4)
    #       #=> rgba(1, 2, 3, 0.4)
    #
    # @param attrs [{Symbol => Numeric}]
    #   A map of channel names (`:red`, `:green`, `:blue`,
    #   `:hue`, `:saturation`, `:lightness`, or `:alpha`) to values
    # @return [Color] The new Color object
    # @raise [ArgumentError] if both RGB and HSL keys are specified
    def with(attrs)
      attrs = attrs.reject {|k, v| v.nil?}
      hsl = !([:hue, :saturation, :lightness] & attrs.keys).empty?
      rgb = !([:red, :green, :blue] & attrs.keys).empty?
      if hsl && rgb
        raise ArgumentError.new("Cannot specify HSL and RGB values for a color at the same time")
      end

      if hsl
        [:hue, :saturation, :lightness].each {|k| attrs[k] ||= send(k)}
      elsif rgb
        [:red, :green, :blue].each {|k| attrs[k] ||= send(k)}
      else
        # If we're just changing the alpha channel,
        # keep all the HSL/RGB stuff we've calculated
        attrs = @attrs.merge(attrs)
      end
      attrs[:alpha] ||= alpha

      Color.new(attrs, :allow_both_rgb_and_hsl)
    end

    # The SassScript `+` operation.
    # Its functionality depends on the type of its argument:
    #
    # {Number}
    # : Adds the number to each of the RGB color channels.
    #
    # {Color}
    # : Adds each of the RGB color channels together.
    #
    # {Literal}
    # : See {Literal#plus}.
    #
    # @param other [Literal] The right-hand side of the operator
    # @return [Color] The resulting color
    # @raise [Sass::SyntaxError] if `other` is a number with units
    def plus(other)
      if other.is_a?(Sass::Script::Number) || other.is_a?(Sass::Script::Color)
        piecewise(other, :+)
      else
        super
      end
    end

    # The SassScript `-` operation.
    # Its functionality depends on the type of its argument:
    #
    # {Number}
    # : Subtracts the number from each of the RGB color channels.
    #
    # {Color}
    # : Subtracts each of the other color's RGB color channels from this color's.
    #
    # {Literal}
    # : See {Literal#minus}.
    #
    # @param other [Literal] The right-hand side of the operator
    # @return [Color] The resulting color
    # @raise [Sass::SyntaxError] if `other` is a number with units
    def minus(other)
      if other.is_a?(Sass::Script::Number) || other.is_a?(Sass::Script::Color)
        piecewise(other, :-)
      else
        super
      end
    end

    # The SassScript `*` operation.
    # Its functionality depends on the type of its argument:
    #
    # {Number}
    # : Multiplies the number by each of the RGB color channels.
    #
    # {Color}
    # : Multiplies each of the RGB color channels together.
    #
    # @param other [Number, Color] The right-hand side of the operator
    # @return [Color] The resulting color
    # @raise [Sass::SyntaxError] if `other` is a number with units
    def times(other)
      if other.is_a?(Sass::Script::Number) || other.is_a?(Sass::Script::Color)
        piecewise(other, :*)
      else
        raise NoMethodError.new(nil, :times)
      end
    end

    # The SassScript `/` operation.
    # Its functionality depends on the type of its argument:
    #
    # {Number}
    # : Divides each of the RGB color channels by the number.
    #
    # {Color}
    # : Divides each of this color's RGB color channels by the other color's.
    #
    # {Literal}
    # : See {Literal#div}.
    #
    # @param other [Literal] The right-hand side of the operator
    # @return [Color] The resulting color
    # @raise [Sass::SyntaxError] if `other` is a number with units
    def div(other)
      if other.is_a?(Sass::Script::Number) || other.is_a?(Sass::Script::Color)
        piecewise(other, :/)
      else
        super
      end
    end

    # The SassScript `%` operation.
    # Its functionality depends on the type of its argument:
    #
    # {Number}
    # : Takes each of the RGB color channels module the number.
    #
    # {Color}
    # : Takes each of this color's RGB color channels modulo the other color's.
    #
    # @param other [Number, Color] The right-hand side of the operator
    # @return [Color] The resulting color
    # @raise [Sass::SyntaxError] if `other` is a number with units
    def mod(other)
      if other.is_a?(Sass::Script::Number) || other.is_a?(Sass::Script::Color)
        piecewise(other, :%)
      else
        raise NoMethodError.new(nil, :mod)
      end
    end

    # Returns a string representation of the color.
    # This is usually the color's hex value,
    # but if the color has a name that's used instead.
    #
    # @return [String] The string representation
    def to_s(opts = {})
      return rgba_str if alpha?
      return smallest if options[:style] == :compressed
      return HTML4_COLORS_REVERSE[rgb] if HTML4_COLORS_REVERSE[rgb]
      hex_str
    end
    alias_method :to_sass, :to_s

    # Returns a string representation of the color.
    #
    # @return [String] The hex value
    def inspect
      alpha? ? rgba_str : hex_str
    end

    private

    def smallest
      small_hex_str = hex_str.gsub(/^#(.)\1(.)\2(.)\3$/, '#\1\2\3')
      return small_hex_str unless (color = HTML4_COLORS_REVERSE[rgb]) &&
        color.size <= small_hex_str.size
      return color
    end

    def rgba_str
      split = options[:style] == :compressed ? ',' : ', '
      "rgba(#{rgb.join(split)}#{split}#{Number.round(alpha)})"
    end

    def hex_str
      red, green, blue = rgb.map { |num| num.to_s(16).rjust(2, '0') }
      "##{red}#{green}#{blue}"
    end

    def piecewise(other, operation)
      other_num = other.is_a? Number
      if other_num && !other.unitless?
        raise Sass::SyntaxError.new("Cannot add a number with units (#{other}) to a color (#{self}).") 
      end

      result = []
      for i in (0...3)
        res = rgb[i].send(operation, other_num ? other.value : other.rgb[i])
        result[i] = [ [res, 255].min, 0 ].max
      end

      if !other_num && other.alpha != alpha
        raise Sass::SyntaxError.new("Alpha channels must be equal: #{self} #{operation} #{other}")
      end

      with(:red => result[0], :green => result[1], :blue => result[2])
    end

    def hsl_to_rgb!
      return if @attrs[:red] && @attrs[:blue] && @attrs[:green]

      h = @attrs[:hue] / 360.0
      s = @attrs[:saturation] / 100.0
      l = @attrs[:lightness] / 100.0

      # Algorithm from the CSS3 spec: http://www.w3.org/TR/css3-color/#hsl-color.
      m2 = l <= 0.5 ? l * (s + 1) : l + s - l * s
      m1 = l * 2 - m2
      @attrs[:red], @attrs[:green], @attrs[:blue] = [
        hue_to_rgb(m1, m2, h + 1.0/3),
        hue_to_rgb(m1, m2, h),
        hue_to_rgb(m1, m2, h - 1.0/3)
      ].map {|c| (c * 0xff).round}
    end

    def hue_to_rgb(m1, m2, h)
      h += 1 if h < 0
      h -= 1 if h > 1
      return m1 + (m2 - m1) * h * 6 if h * 6 < 1
      return m2 if h * 2 < 1
      return m1 + (m2 - m1) * (2.0/3 - h) * 6 if h * 3 < 2
      return m1
    end

    def rgb_to_hsl!
      return if @attrs[:hue] && @attrs[:saturation] && @attrs[:lightness]
      r, g, b = [:red, :green, :blue].map {|k| @attrs[k] / 255.0}

      # Algorithm from http://en.wikipedia.org/wiki/HSL_and_HSV#Conversion_from_RGB_to_HSL_or_HSV
      max = [r, g, b].max
      min = [r, g, b].min
      d = max - min

      h =
        case max
        when min; 0
        when r; 60 * (g-b)/d
        when g; 60 * (b-r)/d + 120
        when b; 60 * (r-g)/d + 240
        end

      l = (max + min)/2.0

      s =
        if max == min
          0
        elsif l < 0.5
          d/(2*l)
        else
          d/(2 - 2*l)
        end

      @attrs[:hue] = h % 360
      @attrs[:saturation] = s * 100
      @attrs[:lightness] = l * 100
    end
  end
end

module Sass::Script
  # A SassScript object representing a boolean (true or false) value.
  class Bool < Literal
    # The Ruby value of the boolean.
    #
    # @return [Boolean]
    attr_reader :value
    alias_method :to_bool, :value

    # @return [String] "true" or "false"
    def to_s(opts = {})
      @value.to_s
    end
    alias_method :to_sass, :to_s
  end
end
module Sass::Script
  # A SassScript object representing a CSS list.
  # This includes both comma-separated lists and space-separated lists.
  class List < Literal
    # The Ruby array containing the contents of the list.
    #
    # @return [Array<Literal>]
    attr_reader :value
    alias_method :children, :value
    alias_method :to_a, :value

    # The operator separating the values of the list.
    # Either `:comma` or `:space`.
    #
    # @return [Symbol]
    attr_reader :separator

    # Creates a new list.
    #
    # @param value [Array<Literal>] See \{#value}
    # @param separator [String] See \{#separator}
    def initialize(value, separator)
      super(value)
      @separator = separator
    end

    # @see Node#eq
    def eq(other)
      Sass::Script::Bool.new(
        self.class == other.class && self.value == other.value &&
        self.separator == other.separator)
    end

    # @see Node#to_s
    def to_s(opts = {})
      raise Sass::SyntaxError.new("() isn't a valid CSS value.") if value.empty?
      return value.reject {|e| e.is_a?(List) && e.value.empty?}.map {|e| e.to_s(opts)}.join(sep_str)
    end

    # @see Node#to_sass
    def to_sass(opts = {})
      precedence = Sass::Script::Parser.precedence_of(separator)
      value.map do |v|
        if v.is_a?(List) && Sass::Script::Parser.precedence_of(v.separator) <= precedence
          "(#{v.to_sass(opts)})"
        else
          v.to_sass(opts)
        end
      end.join(sep_str(nil))
    end

    # @see Node#inspect
    def inspect
      "(#{to_sass})"
    end

    protected

    # @see Node#_perform
    def _perform(environment)
      list = Sass::Script::List.new(
        value.map {|e| e.perform(environment)},
        separator)
      list.options = self.options
      list
    end

    private

    def sep_str(opts = self.options)
      return ' ' if separator == :space
      return ',' if opts && opts[:style] == :compressed
      return ', '
    end
  end
end

    # Returns the Ruby value of the literal.
    # The type of this value varies based on the subclass.
    #
    # @return [Object]
    attr_reader :value

    # Creates a new literal.
    #
    # @param value [Object] The object for \{#value}
    def initialize(value = nil)
      @value = value
      super()
    end

    # Returns an empty array.
    #
    # @return [Array<Node>] empty
    # @see Node#children
    def children
      []
    end

    # Returns the options hash for this node.
    #
    # @return [{Symbol => Object}]
    # @raise [Sass::SyntaxError] if the options hash hasn't been set.
    #   This should only happen when the literal was created
    #   outside of the parser and \{#to\_s} was called on it
    def options
      opts = super
      return opts if opts
      raise Sass::SyntaxError.new(<<MSG)
The #options attribute is not set on this #{self.class}.
  This error is probably occurring because #to_s was called
  on this literal within a custom Sass function without first
  setting the #option attribute.
MSG
    end

    # The SassScript `and` operation.
    #
    # @param other [Literal] The right-hand side of the operator
    # @return [Literal] The result of a logical and:
    #   `other` if this literal isn't a false {Bool},
    #   and this literal otherwise
    def and(other)
      to_bool ? other : self
    end

    # The SassScript `or` operation.
    #
    # @param other [Literal] The right-hand side of the operator
    # @return [Literal] The result of the logical or:
    #   this literal if it isn't a false {Bool},
    #   and `other` otherwise
    def or(other)
      to_bool ? self : other
    end

    # The SassScript `==` operation.
    # **Note that this returns a {Sass::Script::Bool} object,
    # not a Ruby boolean**.
    #
    # @param other [Literal] The right-hand side of the operator
    # @return [Bool] True if this literal is the same as the other,
    #   false otherwise
    def eq(other)
      Sass::Script::Bool.new(self.class == other.class && self.value == other.value)
    end

    # The SassScript `!=` operation.
    # **Note that this returns a {Sass::Script::Bool} object,
    # not a Ruby boolean**.
    #
    # @param other [Literal] The right-hand side of the operator
    # @return [Bool] False if this literal is the same as the other,
    #   true otherwise
    def neq(other)
      Sass::Script::Bool.new(!eq(other).to_bool)
    end

    # The SassScript `==` operation.
    # **Note that this returns a {Sass::Script::Bool} object,
    # not a Ruby boolean**.
    #
    # @param other [Literal] The right-hand side of the operator
    # @return [Bool] True if this literal is the same as the other,
    #   false otherwise
    def unary_not
      Sass::Script::Bool.new(!to_bool)
    end

    # The SassScript default operation (e.g. `$a $b`, `"foo" "bar"`).
    #
    # @param other [Literal] The right-hand side of the operator
    # @return [Script::String] A string containing both literals
    #   separated by a space
    def space(other)
      Sass::Script::String.new("#{self.to_s} #{other.to_s}")
    end

    # The SassScript `,` operation (e.g. `$a, $b`, `"foo", "bar"`).
    #
    # @param other [Literal] The right-hand side of the operator
    # @return [Script::String] A string containing both literals
    #   separated by `", "`
    def comma(other)
      Sass::Script::String.new("#{self.to_s},#{' ' unless options[:style] == :compressed}#{other.to_s}")
    end

    # The SassScript `=` operation
    # (used for proprietary MS syntax like `alpha(opacity=20)`).
    #
    # @param other [Literal] The right-hand side of the operator
    # @return [Script::String] A string containing both literals
    #   separated by `"="`
    def single_eq(other)
      Sass::Script::String.new("#{self.to_s}=#{other.to_s}")
    end

    # The SassScript `+` operation.
    #
    # @param other [Literal] The right-hand side of the operator
    # @return [Script::String] A string containing both literals
    #   without any separation
    def plus(other)
      if other.is_a?(Sass::Script::String)
        return Sass::Script::String.new(self.to_s + other.value, other.type)
      end
      Sass::Script::String.new(self.to_s + other.to_s)
    end

    # The SassScript `-` operation.
    #
    # @param other [Literal] The right-hand side of the operator
    # @return [Script::String] A string containing both literals
    #   separated by `"-"`
    def minus(other)
      Sass::Script::String.new("#{self.to_s}-#{other.to_s}")
    end

    # The SassScript `/` operation.
    #
    # @param other [Literal] The right-hand side of the operator
    # @return [Script::String] A string containing both literals
    #   separated by `"/"`
    def div(other)
      Sass::Script::String.new("#{self.to_s}/#{other.to_s}")
    end

    # The SassScript unary `+` operation (e.g. `+$a`).
    #
    # @param other [Literal] The right-hand side of the operator
    # @return [Script::String] A string containing the literal
    #   preceded by `"+"`
    def unary_plus
      Sass::Script::String.new("+#{self.to_s}")
    end

    # The SassScript unary `-` operation (e.g. `-$a`).
    #
    # @param other [Literal] The right-hand side of the operator
    # @return [Script::String] A string containing the literal
    #   preceded by `"-"`
    def unary_minus
      Sass::Script::String.new("-#{self.to_s}")
    end

    # The SassScript unary `/` operation (e.g. `/$a`).
    #
    # @param other [Literal] The right-hand side of the operator
    # @return [Script::String] A string containing the literal
    #   preceded by `"/"`
    def unary_div
      Sass::Script::String.new("/#{self.to_s}")
    end

    # @return [String] A readable representation of the literal
    def inspect
      value.inspect
    end

    # @return [Boolean] `true` (the Ruby boolean value)
    def to_bool
      true
    end

    # Compares this object with another.
    #
    # @param other [Object] The object to compare with
    # @return [Boolean] Whether or not this literal is equivalent to `other`
    def ==(other)
      eq(other).to_bool
    end

    # @return [Fixnum] The integer value of this literal
    # @raise [Sass::SyntaxError] if this literal isn't an integer
    def to_i
      raise Sass::SyntaxError.new("#{self.inspect} is not an integer.")
    end

    # @raise [Sass::SyntaxError] if this literal isn't an integer
    def assert_int!; to_i; end

    # Returns the value of this literal as a list.
    # Single literals are considered the same as single-element lists.
    #
    # @return [Array<Literal>] The of this literal as a list
    def to_a
      [self]
    end

    # Returns the string representation of this literal
    # as it would be output to the CSS document.
    #
    # @return [String]
    def to_s(opts = {})
      raise Sass::SyntaxError.new("[BUG] All subclasses of Sass::Literal must implement #to_s.")
    end
    alias_method :to_sass, :to_s

    protected

    # Evaluates the literal.
    #
    # @param environment [Sass::Environment] The environment in which to evaluate the SassScript
    # @return [Literal] This literal
    def _perform(environment)
      self
    end
  end
end

module Sass::Script
  # A SassScript object representing a CSS string *or* a CSS identifier.
  class String < Literal
    # The Ruby value of the string.
    #
    # @return [String]
    attr_reader :value

    # Whether this is a CSS string or a CSS identifier.
    # The difference is that strings are written with double-quotes,
    # while identifiers aren't.
    #
    # @return [Symbol] `:string` or `:identifier`
    attr_reader :type

    # Creates a new string.
    #
    # @param value [String] See \{#value}
    # @param type [Symbol] See \{#type}
    def initialize(value, type = :identifier)
      super(value)
      @type = type
    end

    # @see Literal#plus
    def plus(other)
      other_str = other.is_a?(Sass::Script::String) ? other.value : other.to_s
      Sass::Script::String.new(self.value + other_str, self.type)
    end

    # @see Node#to_s
    def to_s(opts = {})
      if @type == :identifier
        return @value.tr("\n", " ")
      end

      return "\"#{value.gsub('"', "\\\"")}\"" if opts[:quote] == %q{"}
      return "'#{value.gsub("'", "\\'")}'" if opts[:quote] == %q{'}
      return "\"#{value}\"" unless value.include?('"')
      return "'#{value}'" unless value.include?("'")
      "\"#{value.gsub('"', "\\\"")}\"" #'
    end

    # @see Node#to_sass
    def to_sass(opts = {})
      to_s
    end
  end
end
module Sass::Script
  # A SassScript parse node representing a unary operation,
  # such as `-$b` or `not true`.
  #
  # Currently only `-`, `/`, and `not` are unary operators.
  class UnaryOperation < Node
    # @param operand [Script::Node] The parse-tree node
    #   for the object of the operator
    # @param operator [Symbol] The operator to perform
    def initialize(operand, operator)
      @operand = operand
      @operator = operator
      super()
    end

    # @return [String] A human-readable s-expression representation of the operation
    def inspect
      "(#{@operator.inspect} #{@operand.inspect})"
    end

    # @see Node#to_sass
    def to_sass(opts = {})
      operand = @operand.to_sass(opts)
      if @operand.is_a?(Operation) ||
          (@operator == :minus &&
           (operand =~ Sass::SCSS::RX::IDENT) == 0)
        operand = "(#{@operand.to_sass(opts)})"
      end
      op = Lexer::OPERATORS_REVERSE[@operator]
      op + (op =~ /[a-z]/ ? " " : "") + operand
    end

    # Returns the operand of the operation.
    #
    # @return [Array<Node>]
    # @see Node#children
    def children
      [@operand]
    end

    protected

    # Evaluates the operation.
    #
    # @param environment [Sass::Environment] The environment in which to evaluate the SassScript
    # @return [Literal] The SassScript object that is the value of the operation
    # @raise [Sass::SyntaxError] if the operation is undefined for the operand
    def _perform(environment)
      operator = "unary_#{@operator}"
      literal = @operand.perform(environment)
      literal.send(operator)
    rescue NoMethodError => e
      raise e unless e.name.to_s == operator.to_s
      raise Sass::SyntaxError.new("Undefined unary operation: \"#{@operator} #{literal}\".")
    end
  end
end
module Sass::Script
  # A SassScript object representing `#{}` interpolation outside a string.
  #
  # @see StringInterpolation
  class Interpolation < Node
    # Interpolation in a property is of the form `before #{mid} after`.
    #
    # @param before [Node] The SassScript before the interpolation
    # @param mid [Node] The SassScript within the interpolation
    # @param after [Node] The SassScript after the interpolation
    # @param wb [Boolean] Whether there was whitespace between `before` and `#{`
    # @param wa [Boolean] Whether there was whitespace between `}` and `after`
    # @param originally_text [Boolean]
    #   Whether the original format of the interpolation was plain text,
    #   not an interpolation.
    #   This is used when converting back to SassScript.
    def initialize(before, mid, after, wb, wa, originally_text = false)
      @before = before
      @mid = mid
      @after = after
      @whitespace_before = wb
      @whitespace_after = wa
      @originally_text = originally_text
    end

    # @return [String] A human-readable s-expression representation of the interpolation
    def inspect
      "(interpolation #{@before.inspect} #{@mid.inspect} #{@after.inspect})"
    end

    # @see Node#to_sass
    def to_sass(opts = {})
      res = ""
      res << @before.to_sass(opts) if @before
      res << ' ' if @before && @whitespace_before
      res << '#{' unless @originally_text
      res << @mid.to_sass(opts)
      res << '}' unless @originally_text
      res << ' ' if @after && @whitespace_after
      res << @after.to_sass(opts) if @after
      res
    end

    # Returns the three components of the interpolation, `before`, `mid`, and `after`.
    #
    # @return [Array<Node>]
    # @see #initialize
    # @see Node#children
    def children
      [@before, @mid, @after].compact
    end

    protected

    # Evaluates the interpolation.
    #
    # @param environment [Sass::Environment] The environment in which to evaluate the SassScript
    # @return [Sass::Script::String] The SassScript string that is the value of the interpolation
    def _perform(environment)
      res = ""
      res << @before.perform(environment).to_s if @before
      res << " " if @before && @whitespace_before
      val = @mid.perform(environment)
      res << (val.is_a?(Sass::Script::String) ? val.value : val.to_s)
      res << " " if @after && @whitespace_after
      res << @after.perform(environment).to_s if @after
      opts(Sass::Script::String.new(res))
    end
  end
end
module Sass::Script
  # A SassScript object representing `#{}` interpolation within a string.
  #
  # @see Interpolation
  class StringInterpolation < Node
    # Interpolation in a string is of the form `"before #{mid} after"`,
    # where `before` and `after` may include more interpolation.
    #
    # @param before [Node] The string before the interpolation
    # @param mid [Node] The SassScript within the interpolation
    # @param after [Node] The string after the interpolation
    def initialize(before, mid, after)
      @before = before
      @mid = mid
      @after = after
    end

    # @return [String] A human-readable s-expression representation of the interpolation
    def inspect
      "(string_interpolation #{@before.inspect} #{@mid.inspect} #{@after.inspect})"
    end

    # @see Node#to_sass
    def to_sass(opts = {})
      # We can get rid of all of this when we remove the deprecated :equals context
      # XXX CE: It's gone now but I'm not sure what can be removed now.
      before_unquote, before_quote_char, before_str = parse_str(@before.to_sass(opts))
      after_unquote, after_quote_char, after_str = parse_str(@after.to_sass(opts))
      unquote = before_unquote || after_unquote ||
        (before_quote_char && !after_quote_char && !after_str.empty?) ||
        (!before_quote_char && after_quote_char && !before_str.empty?)
      quote_char =
        if before_quote_char && after_quote_char && before_quote_char != after_quote_char
          before_str.gsub!("\\'", "'")
          before_str.gsub!('"', "\\\"")
          after_str.gsub!("\\'", "'")
          after_str.gsub!('"', "\\\"")
          '"'
        else
          before_quote_char || after_quote_char
        end

      res = ""
      res << 'unquote(' if unquote
      res << quote_char if quote_char
      res << before_str
      res << '#{' << @mid.to_sass(opts) << '}'
      res << after_str
      res << quote_char if quote_char
      res << ')' if unquote
      res
    end

    # Returns the three components of the interpolation, `before`, `mid`, and `after`.
    #
    # @return [Array<Node>]
    # @see #initialize
    # @see Node#children
    def children
      [@before, @mid, @after].compact
    end

    protected

    # Evaluates the interpolation.
    #
    # @param environment [Sass::Environment] The environment in which to evaluate the SassScript
    # @return [Sass::Script::String] The SassScript string that is the value of the interpolation
    def _perform(environment)
      res = ""
      before = @before.perform(environment)
      res << before.value
      mid = @mid.perform(environment)
      res << (mid.is_a?(Sass::Script::String) ? mid.value : mid.to_s)
      res << @after.perform(environment).value
      opts(Sass::Script::String.new(res, before.type))
    end

    private

    def parse_str(str)
      case str
      when /^unquote\((["'])(.*)\1\)$/
        return true, $1, $2
      when '""'
        return false, nil, ""
      when /^(["'])(.*)\1$/
        return false, $1, $2
      else
        return false, nil, str
      end
    end
  end
end

module Sass::Script
  # A SassScript parse node representing a binary operation,
  # such as `$a + $b` or `"foo" + 1`.
  class Operation < Node
    attr_reader :operand1
    attr_reader :operand2
    attr_reader :operator

    # @param operand1 [Script::Node] The parse-tree node
    #   for the right-hand side of the operator
    # @param operand2 [Script::Node] The parse-tree node
    #   for the left-hand side of the operator
    # @param operator [Symbol] The operator to perform.
    #   This should be one of the binary operator names in {Lexer::OPERATORS}
    def initialize(operand1, operand2, operator)
      @operand1 = operand1
      @operand2 = operand2
      @operator = operator
      super()
    end

    # @return [String] A human-readable s-expression representation of the operation
    def inspect
      "(#{@operator.inspect} #{@operand1.inspect} #{@operand2.inspect})"
    end

    # @see Node#to_sass
    def to_sass(opts = {})
      pred = Sass::Script::Parser.precedence_of(@operator)
      o1 = operand_to_sass @operand1, :left, opts
      o2 = operand_to_sass @operand2, :right, opts
      sep =
        case @operator
        when :comma; ", "
        when :space; " "
        else; " #{Lexer::OPERATORS_REVERSE[@operator]} "
        end
      "#{o1}#{sep}#{o2}"
    end

    # Returns the operands for this operation.
    #
    # @return [Array<Node>]
    # @see Node#children
    def children
      [@operand1, @operand2]
    end

    protected

    # Evaluates the operation.
    #
    # @param environment [Sass::Environment] The environment in which to evaluate the SassScript
    # @return [Literal] The SassScript object that is the value of the operation
    # @raise [Sass::SyntaxError] if the operation is undefined for the operands
    def _perform(environment)
      literal1 = @operand1.perform(environment)
      literal2 = @operand2.perform(environment)

      begin
        opts(literal1.send(@operator, literal2))
      rescue NoMethodError => e
        raise e unless e.name.to_s == @operator.to_s
        raise Sass::SyntaxError.new("Undefined operation: \"#{literal1} #{@operator} #{literal2}\".")
      end
    end

    private

    def operand_to_sass(op, side, opts)
      return "(#{op.to_sass(opts)})" if op.is_a?(List)
      return op.to_sass(opts) unless op.is_a?(Operation)

      pred = Sass::Script::Parser.precedence_of(@operator)
      sub_pred = Sass::Script::Parser.precedence_of(op.operator)
      assoc = Sass::Script::Parser.associative?(@operator)
      return "(#{op.to_sass(opts)})" if sub_pred < pred ||
        (side == :right && sub_pred == pred && !assoc)
      op.to_sass(opts)
    end
  end
end
module Sass
  module SCSS
    # A module containing regular expressions used
    # for lexing tokens in an SCSS document.
    # Most of these are taken from [the CSS3 spec](http://www.w3.org/TR/css3-syntax/#lexical),
    # although some have been modified for various reasons.
    module RX
      # Takes a string and returns a CSS identifier
      # that will have the value of the given string.
      #
      # @param str [String] The string to escape
      # @return [String] The escaped string
      def self.escape_ident(str)
        return "" if str.empty?
        return "\\#{str}" if str == '-' || str == '_'
        out = ""
        value = str.dup
        out << value.slice!(0...1) if value =~ /^[-_]/
        if value[0...1] =~ NMSTART
          out << value.slice!(0...1)
        else
          out << escape_char(value.slice!(0...1))
        end
        out << value.gsub(/[^a-zA-Z0-9_-]/) {|c| escape_char c}
        return out
      end

      # Escapes a single character for a CSS identifier.
      #
      # @param c [String] The character to escape. Should have length 1
      # @return [String] The escaped character
      # @private
      def self.escape_char(c)
        return "\\%06x" % Sass::Util.ord(c) unless c =~ /[ -\/:-~]/
        return "\\#{c}"
      end

      # Creates a Regexp from a plain text string,
      # escaping all significant characters.
      #
      # @param str [String] The text of the regexp
      # @param flags [Fixnum] Flags for the created regular expression
      # @return [Regexp]
      # @private
      def self.quote(str, flags = 0)
        Regexp.new(Regexp.quote(str), flags)
      end

      H        = /[0-9a-fA-F]/
      NL       = /\n|\r\n|\r|\f/
      UNICODE  = /\\#{H}{1,6}[ \t\r\n\f]?/
      s = if Sass::Util.ruby1_8?
            '\200-\377'
          else
            '\u{80}-\u{D7FF}\u{E000}-\u{FFFD}\u{10000}-\u{10FFFF}'
          end
      NONASCII = /[#{s}]/
      ESCAPE   = /#{UNICODE}|\\[ -~#{s}]/
      NMSTART  = /[_a-zA-Z]|#{NONASCII}|#{ESCAPE}/
      NMCHAR   = /[a-zA-Z0-9_-]|#{NONASCII}|#{ESCAPE}/
      STRING1  = /\"((?:[^\n\r\f\\"]|\\#{NL}|#{ESCAPE})*)\"/
      STRING2  = /\'((?:[^\n\r\f\\']|\\#{NL}|#{ESCAPE})*)\'/

      IDENT    = /-?#{NMSTART}#{NMCHAR}*/
      NAME     = /#{NMCHAR}+/
      NUM      = /[0-9]+|[0-9]*\.[0-9]+/
      STRING   = /#{STRING1}|#{STRING2}/
      URLCHAR  = /[#%&*-~]|#{NONASCII}|#{ESCAPE}/
      URL      = /(#{URLCHAR}*)/
      W        = /[ \t\r\n\f]*/
      VARIABLE = /(\$)(#{Sass::SCSS::RX::IDENT})/

      # This is more liberal than the spec's definition,
      # but that definition didn't work well with the greediness rules
      RANGE    = /(?:#{H}|\?){1,6}/

      ##

      S = /[ \t\r\n\f]+/

      COMMENT = /\/\*[^*]*\*+(?:[^\/][^*]*\*+)*\//
      SINGLE_LINE_COMMENT = /\/\/.*(\n[ \t]*\/\/.*)*/

      CDO            = quote("<!--")
      CDC            = quote("-->")
      INCLUDES       = quote("~=")
      DASHMATCH      = quote("|=")
      PREFIXMATCH    = quote("^=")
      SUFFIXMATCH    = quote("$=")
      SUBSTRINGMATCH = quote("*=")

      HASH = /##{NAME}/

      IMPORTANT = /!#{W}important/i
      DEFAULT = /!#{W}default/i

      NUMBER = /#{NUM}(?:#{IDENT}|%)?/

      URI = /url\(#{W}(?:#{STRING}|#{URL})#{W}\)/i
      FUNCTION = /#{IDENT}\(/

      UNICODERANGE = /u\+(?:#{H}{1,6}-#{H}{1,6}|#{RANGE})/i

      # Defined in http://www.w3.org/TR/css3-selectors/#lex
      PLUS = /#{W}\+/
      GREATER = /#{W}>/
      TILDE = /#{W}~/
      NOT = quote(":not(", Regexp::IGNORECASE)

      # Custom
      HEXCOLOR = /\#[0-9a-fA-F]+/
      INTERP_START = /#\{/
      MOZ_ANY = quote(":-moz-any(", Regexp::IGNORECASE)

      STRING1_NOINTERP = /\"((?:[^\n\r\f\\"#]|#(?!\{)|\\#{NL}|#{ESCAPE})*)\"/
      STRING2_NOINTERP = /\'((?:[^\n\r\f\\'#]|#(?!\{)|\\#{NL}|#{ESCAPE})*)\'/
      STRING_NOINTERP = /#{STRING1_NOINTERP}|#{STRING2_NOINTERP}/
      # Can't use IDENT here, because it seems to take exponential time on 1.8.
      # We could use it for 1.9 only, but I don't want to introduce a cross-version
      # behavior difference.
      # In any case, almost all CSS idents will be matched by this.
      STATIC_VALUE = /(-?#{NMSTART}|#{STRING_NOINTERP}|\s(?!%)|#[a-f0-9]|[,%]|#{NUM}|\!important)+(?=[;}])/i

      STATIC_SELECTOR = /(#{NMCHAR}|\s|[,>+*]|[:#.]#{NMSTART})+(?=[{])/i
    end
  end
end

require 'strscan'

module Sass
  module Script
    # The lexical analyzer for SassScript.
    # It takes a raw string and converts it to individual tokens
    # that are easier to parse.
    class Lexer
      include Sass::SCSS::RX

      # A struct containing information about an individual token.
      #
      # `type`: \[`Symbol`\]
      # : The type of token.
      #
      # `value`: \[`Object`\]
      # : The Ruby object corresponding to the value of the token.
      #
      # `line`: \[`Fixnum`\]
      # : The line of the source file on which the token appears.
      #
      # `offset`: \[`Fixnum`\]
      # : The number of bytes into the line the SassScript token appeared.
      #
      # `pos`: \[`Fixnum`\]
      # : The scanner position at which the SassScript token appeared.
      Token = Struct.new(:type, :value, :line, :offset, :pos)

      # The line number of the lexer's current position.
      #
      # @return [Fixnum]
      attr_reader :line

      # The number of bytes into the current line
      # of the lexer's current position.
      #
      # @return [Fixnum]
      attr_reader :offset

      # A hash from operator strings to the corresponding token types.
      OPERATORS = {
        '+' => :plus,
        '-' => :minus,
        '*' => :times,
        '/' => :div,
        '%' => :mod,
        '=' => :single_eq,
        ':' => :colon,
        '(' => :lparen,
        ')' => :rparen,
        ',' => :comma,
        'and' => :and,
        'or' => :or,
        'not' => :not,
        '==' => :eq,
        '!=' => :neq,
        '>=' => :gte,
        '<=' => :lte,
        '>' => :gt,
        '<' => :lt,
        '#{' => :begin_interpolation,
        '}' => :end_interpolation,
        ';' => :semicolon,
        '{' => :lcurly,
      }

      OPERATORS_REVERSE = Sass::Util.map_hash(OPERATORS) {|k, v| [v, k]}

      TOKEN_NAMES = Sass::Util.map_hash(OPERATORS_REVERSE) {|k, v| [k, v.inspect]}.merge({
          :const => "variable (e.g. $foo)",
          :ident => "identifier (e.g. middle)",
          :bool => "boolean (e.g. true, false)",
        })

      # A list of operator strings ordered with longer names first
      # so that `>` and `<` don't clobber `>=` and `<=`.
      OP_NAMES = OPERATORS.keys.sort_by {|o| -o.size}

      # A sub-list of {OP_NAMES} that only includes operators
      # with identifier names.
      IDENT_OP_NAMES = OP_NAMES.select {|k, v| k =~ /^\w+/}

      # A hash of regular expressions that are used for tokenizing.
      REGULAR_EXPRESSIONS = {
        :whitespace => /\s+/,
        :comment => COMMENT,
        :single_line_comment => SINGLE_LINE_COMMENT,
        :variable => /(\$)(#{IDENT})/,
        :ident => /(#{IDENT})(\()?/,
        :number => /(-)?(?:(\d*\.\d+)|(\d+))([a-zA-Z%]+)?/,
        :color => HEXCOLOR,
        :bool => /(true|false)\b/,
        :ident_op => %r{(#{Regexp.union(*IDENT_OP_NAMES.map{|s| Regexp.new(Regexp.escape(s) + "(?!#{NMCHAR}|\Z)")})})},
        :op => %r{(#{Regexp.union(*OP_NAMES)})},
      }

      class << self
        private
        def string_re(open, close)
          /#{open}((?:\\.|\#(?!\{)|[^#{close}\\#])*)(#{close}|#\{)/
        end
      end

      # A hash of regular expressions that are used for tokenizing strings.
      #
      # The key is a `[Symbol, Boolean]` pair.
      # The symbol represents which style of quotation to use,
      # while the boolean represents whether or not the string
      # is following an interpolated segment.
      STRING_REGULAR_EXPRESSIONS = {
        [:double, false] => string_re('"', '"'),
        [:single, false] => string_re("'", "'"),
        [:double, true] => string_re('', '"'),
        [:single, true] => string_re('', "'"),
        [:uri, false] => /url\(#{W}(#{URLCHAR}*?)(#{W}\)|#\{)/,
        [:uri, true] => /(#{URLCHAR}*?)(#{W}\)|#\{)/,
      }

      # @param str [String, StringScanner] The source text to lex
      # @param line [Fixnum] The line on which the SassScript appears.
      #   Used for error reporting
      # @param offset [Fixnum] The number of characters in on which the SassScript appears.
      #   Used for error reporting
      # @param options [{Symbol => Object}] An options hash;
      #   see {file:SASS_REFERENCE.md#sass_options the Sass options documentation}
      def initialize(str, line, offset, options)
        @scanner = str.is_a?(StringScanner) ? str : StringScanner.new(str)
        @line = line
        @offset = offset
        @options = options
        @interpolation_stack = []
        @prev = nil
      end

      # Moves the lexer forward one token.
      #
      # @return [Token] The token that was moved past
      def next
        @tok ||= read_token
        @tok, tok = nil, @tok
        @prev = tok
        return tok
      end

      # Returns whether or not there's whitespace before the next token.
      #
      # @return [Boolean]
      def whitespace?(tok = @tok)
        if tok
          @scanner.string[0...tok.pos] =~ /\s\Z/
        else
          @scanner.string[@scanner.pos, 1] =~ /^\s/ ||
            @scanner.string[@scanner.pos - 1, 1] =~ /\s\Z/
        end
      end

      # Returns the next token without moving the lexer forward.
      #
      # @return [Token] The next token
      def peek
        @tok ||= read_token
      end

      # Rewinds the underlying StringScanner
      # to before the token returned by \{#peek}.
      def unpeek!
        @scanner.pos = @tok.pos if @tok
      end

      # @return [Boolean] Whether or not there's more source text to lex.
      def done?
        whitespace unless after_interpolation? && @interpolation_stack.last
        @scanner.eos? && @tok.nil?
      end

      # @return [Boolean] Whether or not the last token lexed was `:end_interpolation`.
      def after_interpolation?
        @prev && @prev.type == :end_interpolation
      end

      # Raise an error to the effect that `name` was expected in the input stream
      # and wasn't found.
      #
      # This calls \{#unpeek!} to rewind the scanner to immediately after
      # the last returned token.
      #
      # @param name [String] The name of the entity that was expected but not found
      # @raise [Sass::SyntaxError]
      def expected!(name)
        unpeek!
        Sass::SCSS::Parser.expected(@scanner, name, @line)
      end

      # Records all non-comment text the lexer consumes within the block
      # and returns it as a string.
      #
      # @yield A block in which text is recorded
      # @return [String]
      def str
        old_pos = @tok ? @tok.pos : @scanner.pos
        yield
        new_pos = @tok ? @tok.pos : @scanner.pos
        @scanner.string[old_pos...new_pos]
      end

      private

      def read_token
        return if done?
        return unless value = token
        type, val, size = value
        size ||= @scanner.matched_size

        val.line = @line if val.is_a?(Script::Node)
        Token.new(type, val, @line,
          current_position - size, @scanner.pos - size)
      end

      def whitespace
        nil while scan(REGULAR_EXPRESSIONS[:whitespace]) ||
          scan(REGULAR_EXPRESSIONS[:comment]) ||
          scan(REGULAR_EXPRESSIONS[:single_line_comment])
      end

      def token
        if after_interpolation? && (interp_type = @interpolation_stack.pop)
          return string(interp_type, true)
        end

        variable || string(:double, false) || string(:single, false) || number ||
          color || bool || string(:uri, false) || raw(UNICODERANGE) ||
          special_fun || special_val || ident_op || ident || op
      end

      def variable
        _variable(REGULAR_EXPRESSIONS[:variable])
      end

      def _variable(rx)
        line = @line
        offset = @offset
        return unless scan(rx)

        [:const, @scanner[2]]
      end

      def ident
        return unless scan(REGULAR_EXPRESSIONS[:ident])
        [@scanner[2] ? :funcall : :ident, @scanner[1]]
      end

      def string(re, open)
        return unless scan(STRING_REGULAR_EXPRESSIONS[[re, open]])
        if @scanner[2] == '#{' #'
          @scanner.pos -= 2 # Don't actually consume the #{
          @interpolation_stack << re
        end
        str =
          if re == :uri
            Script::String.new("#{'url(' unless open}#{@scanner[1]}#{')' unless @scanner[2] == '#{'}")
          else
            Script::String.new(@scanner[1].gsub(/\\(['"]|\#\{)/, '\1'), :string)
          end
        [:string, str]
      end

      def number
        return unless scan(REGULAR_EXPRESSIONS[:number])
        value = @scanner[2] ? @scanner[2].to_f : @scanner[3].to_i
        value = -value if @scanner[1]
        [:number, Script::Number.new(value, Array(@scanner[4]))]
      end

      def color
        return unless s = scan(REGULAR_EXPRESSIONS[:color])
        raise Sass::SyntaxError.new(<<MESSAGE.rstrip) unless s.size == 4 || s.size == 7
Colors must have either three or six digits: '#{s}'
MESSAGE
        value = s.scan(/^#(..?)(..?)(..?)$/).first.
          map {|num| num.ljust(2, num).to_i(16)}
        [:color, Script::Color.new(value)]
      end

      def bool
        return unless s = scan(REGULAR_EXPRESSIONS[:bool])
        [:bool, Script::Bool.new(s == 'true')]
      end

      def special_fun
        return unless str1 = scan(/((-[\w-]+-)?calc|expression|progid:[a-z\.]*)\(/i)
        str2, _ = Sass::Shared.balance(@scanner, ?(, ?), 1)
        c = str2.count("\n")
        old_line = @line
        old_offset = @offset
        @line += c
        @offset = (c == 0 ? @offset + str2.size : str2[/\n(.*)/, 1].size)
        [:special_fun,
          Sass::Util.merge_adjacent_strings(
            [str1] + Sass::Engine.parse_interp(str2, old_line, old_offset, @options)),
          str1.size + str2.size]
      end

      def special_val
        return unless scan(/!important/i)
        [:string, Script::String.new("!important")]
      end

      def ident_op
        return unless op = scan(REGULAR_EXPRESSIONS[:ident_op])
        [OPERATORS[op]]
      end

      def op
        return unless op = scan(REGULAR_EXPRESSIONS[:op])
        @interpolation_stack << nil if op == :begin_interpolation
        [OPERATORS[op]]
      end

      def raw(rx)
        return unless val = scan(rx)
        [:raw, val]
      end

      def scan(re)
        return unless str = @scanner.scan(re)
        c = str.count("\n")
        @line += c
        @offset = (c == 0 ? @offset + str.size : str[/\n(.*)/, 1].size)
        str
      end

      def current_position
        @offset + 1
      end
    end
  end
end

module Sass
  module Script
    # The parser for SassScript.
    # It parses a string of code into a tree of {Script::Node}s.
    class Parser
      # The line number of the parser's current position.
      #
      # @return [Fixnum]
      def line
        @lexer.line
      end

      # @param str [String, StringScanner] The source text to parse
      # @param line [Fixnum] The line on which the SassScript appears.
      #   Used for error reporting
      # @param offset [Fixnum] The number of characters in on which the SassScript appears.
      #   Used for error reporting
      # @param options [{Symbol => Object}] An options hash;
      #   see {file:SASS_REFERENCE.md#sass_options the Sass options documentation}
      def initialize(str, line, offset, options = {})
        @options = options
        @lexer = lexer_class.new(str, line, offset, options)
      end

      # Parses a SassScript expression within an interpolated segment (`#{}`).
      # This means that it stops when it comes across an unmatched `}`,
      # which signals the end of an interpolated segment,
      # it returns rather than throwing an error.
      #
      # @return [Script::Node] The root node of the parse tree
      # @raise [Sass::SyntaxError] if the expression isn't valid SassScript
      def parse_interpolated
        expr = assert_expr :expr
        assert_tok :end_interpolation
        expr.options = @options
        expr
      rescue Sass::SyntaxError => e
        e.modify_backtrace :line => @lexer.line, :filename => @options[:filename]
        raise e
      end

      # Parses a SassScript expression.
      #
      # @return [Script::Node] The root node of the parse tree
      # @raise [Sass::SyntaxError] if the expression isn't valid SassScript
      def parse
        expr = assert_expr :expr
        assert_done
        expr.options = @options
        expr
      rescue Sass::SyntaxError => e
        e.modify_backtrace :line => @lexer.line, :filename => @options[:filename]
        raise e
      end

      # Parses a SassScript expression,
      # ending it when it encounters one of the given identifier tokens.
      #
      # @param [#include?(String)] A set of strings that delimit the expression.
      # @return [Script::Node] The root node of the parse tree
      # @raise [Sass::SyntaxError] if the expression isn't valid SassScript
      def parse_until(tokens)
        @stop_at = tokens
        expr = assert_expr :expr
        assert_done
        expr.options = @options
        expr
      rescue Sass::SyntaxError => e
        e.modify_backtrace :line => @lexer.line, :filename => @options[:filename]
        raise e
      end

      # Parses the argument list for a mixin include.
      #
      # @return [(Array<Script::Node>, {String => Script::Note})]
      #   The root nodes of the arguments.
      #   Keyword arguments are in a hash from names to values.
      # @raise [Sass::SyntaxError] if the argument list isn't valid SassScript
      def parse_mixin_include_arglist
        args, keywords = [], {}
        if try_tok(:lparen)
          args, keywords = mixin_arglist || [[], {}]
          assert_tok(:rparen)
        end
        assert_done

        args.each {|a| a.options = @options}
        keywords.each {|k, v| v.options = @options}
        return args, keywords
      rescue Sass::SyntaxError => e
        e.modify_backtrace :line => @lexer.line, :filename => @options[:filename]
        raise e
      end

      # Parses the argument list for a mixin definition.
      #
      # @return [Array<Script::Node>] The root nodes of the arguments.
      # @raise [Sass::SyntaxError] if the argument list isn't valid SassScript
      def parse_mixin_definition_arglist
        args = defn_arglist!(false)
        assert_done

        args.each do |k, v|
          k.options = @options
          v.options = @options if v
        end
        args
      rescue Sass::SyntaxError => e
        e.modify_backtrace :line => @lexer.line, :filename => @options[:filename]
        raise e
      end

      # Parses the argument list for a function definition.
      #
      # @return [Array<Script::Node>] The root nodes of the arguments.
      # @raise [Sass::SyntaxError] if the argument list isn't valid SassScript
      def parse_function_definition_arglist
        args = defn_arglist!(true)
        assert_done

        args.each do |k, v|
          k.options = @options
          v.options = @options if v
        end
        args
      rescue Sass::SyntaxError => e
        e.modify_backtrace :line => @lexer.line, :filename => @options[:filename]
        raise e
      end

      # Parses a SassScript expression.
      #
      # @overload parse(str, line, offset, filename = nil)
      # @return [Script::Node] The root node of the parse tree
      # @see Parser#initialize
      # @see Parser#parse
      def self.parse(*args)
        new(*args).parse
      end

      PRECEDENCE = [
        :comma, :single_eq, :space, :or, :and,
        [:eq, :neq],
        [:gt, :gte, :lt, :lte],
        [:plus, :minus],
        [:times, :div, :mod],
      ]

      ASSOCIATIVE = [:plus, :times]

      class << self
        # Returns an integer representing the precedence
        # of the given operator.
        # A lower integer indicates a looser binding.
        #
        # @private
        def precedence_of(op)
          PRECEDENCE.each_with_index do |e, i|
            return i if Array(e).include?(op)
          end
          raise "[BUG] Unknown operator #{op}"
        end

        # Returns whether or not the given operation is associative.
        #
        # @private
        def associative?(op)
          ASSOCIATIVE.include?(op)
        end

        private

        # Defines a simple left-associative production.
        # name is the name of the production,
        # sub is the name of the production beneath it,
        # and ops is a list of operators for this precedence level
        def production(name, sub, *ops)
          class_eval <<RUBY
            def #{name}
              interp = try_ops_after_interp(#{ops.inspect}, #{name.inspect}) and return interp
              return unless e = #{sub}
              while tok = try_tok(#{ops.map {|o| o.inspect}.join(', ')})
                interp = try_op_before_interp(tok, e) and return interp
                line = @lexer.line
                e = Operation.new(e, assert_expr(#{sub.inspect}), tok.type)
                e.line = line
              end
              e
            end
RUBY
        end

        def unary(op, sub)
          class_eval <<RUBY
            def unary_#{op}
              return #{sub} unless tok = try_tok(:#{op})
              interp = try_op_before_interp(tok) and return interp
              line = @lexer.line 
              op = UnaryOperation.new(assert_expr(:unary_#{op}), :#{op})
              op.line = line
              op
            end
RUBY
        end
      end

      private

      # @private
      def lexer_class; Lexer; end

      def expr
        interp = try_ops_after_interp([:comma], :expr) and return interp
        line = @lexer.line
        return unless e = interpolation
        arr = [e]
        while tok = try_tok(:comma)
          interp = try_op_before_interp(tok, e) and return interp
          arr << assert_expr(:interpolation)
        end
        arr.size == 1 ? arr.first : node(List.new(arr, :comma), line)
      end

      production :equals, :interpolation, :single_eq

      def try_op_before_interp(op, prev = nil)
        return unless @lexer.peek && @lexer.peek.type == :begin_interpolation
        wb = @lexer.whitespace?(op)
        str = Script::String.new(Lexer::OPERATORS_REVERSE[op.type])
        str.line = @lexer.line
        interp = Script::Interpolation.new(prev, str, nil, wb, !:wa, :originally_text)
        interp.line = @lexer.line
        interpolation(interp)
      end

      def try_ops_after_interp(ops, name)
        return unless @lexer.after_interpolation?
        return unless op = try_tok(*ops)
        interp = try_op_before_interp(op) and return interp

        wa = @lexer.whitespace?
        str = Script::String.new(Lexer::OPERATORS_REVERSE[op.type])
        str.line = @lexer.line
        interp = Script::Interpolation.new(nil, str, assert_expr(name), !:wb, wa, :originally_text)
        interp.line = @lexer.line
        return interp
      end

      def interpolation(first = space)
        e = first
        while interp = try_tok(:begin_interpolation)
          wb = @lexer.whitespace?(interp)
          line = @lexer.line
          mid = parse_interpolated
          wa = @lexer.whitespace?
          e = Script::Interpolation.new(e, mid, space, wb, wa)
          e.line = line
        end
        e
      end

      def space
        line = @lexer.line
        return unless e = or_expr
        arr = [e]
        while e = or_expr
          arr << e
        end
        arr.size == 1 ? arr.first : node(List.new(arr, :space), line)
      end

      production :or_expr, :and_expr, :or
      production :and_expr, :eq_or_neq, :and
      production :eq_or_neq, :relational, :eq, :neq
      production :relational, :plus_or_minus, :gt, :gte, :lt, :lte
      production :plus_or_minus, :times_div_or_mod, :plus, :minus
      production :times_div_or_mod, :unary_plus, :times, :div, :mod

      unary :plus, :unary_minus
      unary :minus, :unary_div
      unary :div, :unary_not # For strings, so /foo/bar works
      unary :not, :ident

      def ident
        return funcall unless @lexer.peek && @lexer.peek.type == :ident
        return if @stop_at && @stop_at.include?(@lexer.peek.value)

        name = @lexer.next
        if color = Color::HTML4_COLORS[name.value.downcase]
          return node(Color.new(color))
        end
        node(Script::String.new(name.value, :identifier))
      end

      def funcall
        return raw unless tok = try_tok(:funcall)
        args, keywords = fn_arglist || [[], {}]
        assert_tok(:rparen)
        node(Script::Funcall.new(tok.value, args, keywords))
      end

      def defn_arglist!(must_have_parens)
        if must_have_parens
          assert_tok(:lparen)
        else
          return [] unless try_tok(:lparen)
        end
        return [] if try_tok(:rparen)

        res = []
        must_have_default = false
        loop do
          line = @lexer.line
          offset = @lexer.offset + 1
          c = assert_tok(:const)
          var = Script::Variable.new(c.value)
          if tok = try_tok(:colon)
            val = assert_expr(:space)
            must_have_default = true
          elsif must_have_default
            raise SyntaxError.new("Required argument #{var.inspect} must come before any optional arguments.")
          end
          res << [var, val]
          break unless try_tok(:comma)
        end
        assert_tok(:rparen)
        res
      end

      def fn_arglist
        arglist(:fn_arglist, :equals)
      end

      def mixin_arglist
        arglist(:mixin_arglist, :interpolation)
      end

      def arglist(type, subexpr)
        return unless e = send(subexpr)
        if @lexer.peek && @lexer.peek.type == :colon
          name = e
          @lexer.expected!("comma") unless name.is_a?(Variable)
          assert_tok(:colon)
          keywords = {name.underscored_name => assert_expr(subexpr, EXPR_NAMES[type])}
        end

        unless try_tok(:comma)
          return [], keywords if keywords
          return [e], {}
        end

        other_args, other_keywords = assert_expr(type)
        if keywords
          if other_keywords[name.underscored_name]
            raise SyntaxError.new("Keyword argument \"#{name.to_sass}\" passed more than once")
          end
          return other_args, keywords.merge(other_keywords)
        else
          return [e, *other_args], other_keywords
        end
      end

      def keyword_arglist
        return unless var = try_tok(:const)
        unless try_tok(:colon)
          return_tok!
          return
        end
        name = var[1]
        value = interpolation
        return {name => value} unless try_tok(:comma)
        {name => value}.merge(assert_expr(:keyword_arglist))
      end

      def raw
        return special_fun unless tok = try_tok(:raw)
        node(Script::String.new(tok.value))
      end

      def special_fun
        return paren unless tok = try_tok(:special_fun)
        first = node(Script::String.new(tok.value.first))
        Sass::Util.enum_slice(tok.value[1..-1], 2).inject(first) do |l, (i, r)|
          Script::Interpolation.new(
            l, i, r && node(Script::String.new(r)),
            false, false)
        end
      end

      def paren
        return variable unless try_tok(:lparen)
        was_in_parens = @in_parens
        @in_parens = true
        line = @lexer.line
        e = expr
        assert_tok(:rparen)
        return e || node(List.new([], :space), line)
      ensure
        @in_parens = was_in_parens
      end

      def variable
        return string unless c = try_tok(:const)
        node(Variable.new(*c.value))
      end

      def string
        return number unless first = try_tok(:string)
        return first.value unless try_tok(:begin_interpolation)
        line = @lexer.line
        mid = parse_interpolated
        last = assert_expr(:string)
        interp = StringInterpolation.new(first.value, mid, last)
        interp.line = line
        interp
      end

      def number
        return literal unless tok = try_tok(:number)
        num = tok.value
        num.original = num.to_s unless @in_parens
        num
      end

      def literal
        (t = try_tok(:color, :bool)) && (return t.value)
      end

      # It would be possible to have unified #assert and #try methods,
      # but detecting the method/token difference turns out to be quite expensive.

      EXPR_NAMES = {
        :string => "string",
        :default => "expression (e.g. 1px, bold)",
        :mixin_arglist => "mixin argument",
        :fn_arglist => "function argument",
      }

      def assert_expr(name, expected = nil)
        (e = send(name)) && (return e)
        @lexer.expected!(expected || EXPR_NAMES[name] || EXPR_NAMES[:default])
      end

      def assert_tok(*names)
        (t = try_tok(*names)) && (return t)
        @lexer.expected!(names.map {|tok| Lexer::TOKEN_NAMES[tok] || tok}.join(" or "))
      end

      def try_tok(*names)
        peeked =  @lexer.peek
        peeked && names.include?(peeked.type) && @lexer.next
      end

      def assert_done
        return if @lexer.done?
        @lexer.expected!(EXPR_NAMES[:default])
      end

      def node(node, line = @lexer.line)
        node.line = line
        node
      end
    end
  end
end

module Sass
  # SassScript is code that's embedded in Sass documents
  # to allow for property values to be computed from variables.
  #
  # This module contains code that handles the parsing and evaluation of SassScript.
  module Script
    # The regular expression used to parse variables.
    MATCH = /^\$(#{Sass::SCSS::RX::IDENT})\s*:\s*(.+?)(!(?i:default))?$/

    # The regular expression used to validate variables without matching.
    VALIDATE = /^\$#{Sass::SCSS::RX::IDENT}$/

    # Parses a string of SassScript
    #
    # @param value [String] The SassScript
    # @param line [Fixnum] The number of the line on which the SassScript appeared.
    #   Used for error reporting
    # @param offset [Fixnum] The number of characters in on `line` that the SassScript started.
    #   Used for error reporting
    # @param options [{Symbol => Object}] An options hash;
    #   see {file:SASS_REFERENCE.md#sass_options the Sass options documentation}
    # @return [Script::Node] The root node of the parse tree
    def self.parse(value, line, offset, options = {})
      Parser.parse(value, line, offset, options)
    rescue Sass::SyntaxError => e
      e.message << ": #{value.inspect}." if e.message == "SassScript error"
      e.modify_backtrace(:line => line, :filename => options[:filename])
      raise e
    end

  end
end
module Sass
  module SCSS
    # A mixin for subclasses of {Sass::Script::Lexer}
    # that makes them usable by {SCSS::Parser} to parse SassScript.
    # In particular, the lexer doesn't support `!` for a variable prefix.
    module ScriptLexer
      private

      def variable
        return [:raw, "!important"] if scan(Sass::SCSS::RX::IMPORTANT)
        _variable(Sass::SCSS::RX::VARIABLE)
      end
    end
  end
end
module Sass
  module SCSS
    # A mixin for subclasses of {Sass::Script::Parser}
    # that makes them usable by {SCSS::Parser} to parse SassScript.
    # In particular, the parser won't raise an error
    # when there's more content in the lexer once lexing is done.
    # In addition, the parser doesn't support `!` for a variable prefix.
    module ScriptParser
      private

      # @private
      def lexer_class
        klass = Class.new(super)
        klass.send(:include, ScriptLexer)
        klass
      end

      # Instead of raising an error when the parser is done,
      # rewind the StringScanner so that it hasn't consumed the final token.
      def assert_done
        @lexer.unpeek!
      end
    end
  end
end
require 'strscan'
require 'set'

module Sass
  module SCSS
    # The parser for SCSS.
    # It parses a string of code into a tree of {Sass::Tree::Node}s.
    class Parser
      # @param str [String, StringScanner] The source document to parse.
      #   Note that `Parser` *won't* raise a nice error message if this isn't properly parsed;
      #   for that, you should use the higher-level {Sass::Engine} or {Sass::CSS}.
      # @param line [Fixnum] The line on which the source string appeared,
      #   if it's part of another document
      def initialize(str, line = 1)
        @template = str
        @line = line
        @strs = []
      end

      # Parses an SCSS document.
      #
      # @return [Sass::Tree::RootNode] The root node of the document tree
      # @raise [Sass::SyntaxError] if there's a syntax error in the document
      def parse
        init_scanner!
        root = stylesheet
        expected("selector or at-rule") unless @scanner.eos?
        root
      end

      # Parses an identifier with interpolation.
      # Note that this won't assert that the identifier takes up the entire input string;
      # it's meant to be used with `StringScanner`s as part of other parsers.
      #
      # @return [Array<String, Sass::Script::Node>, nil]
      #   The interpolated identifier, or nil if none could be parsed
      def parse_interp_ident
        init_scanner!
        interp_ident
      end

      private

      include Sass::SCSS::RX

      def init_scanner!
        @scanner =
          if @template.is_a?(StringScanner)
            @template
          else
            StringScanner.new(@template.gsub("\r", ""))
          end
      end

      def stylesheet
        node = node(Sass::Tree::RootNode.new(@scanner.string))
        block_contents(node, :stylesheet) {s(node)}
      end

      def s(node)
        while tok(S) || tok(CDC) || tok(CDO) || (c = tok(SINGLE_LINE_COMMENT)) || (c = tok(COMMENT))
          next unless c
          process_comment c, node
          c = nil
        end
        true
      end

      def ss
        nil while tok(S) || tok(SINGLE_LINE_COMMENT) || tok(COMMENT)
        true
      end

      def ss_comments(node)
        while tok(S) || (c = tok(SINGLE_LINE_COMMENT)) || (c = tok(COMMENT))
          next unless c
          process_comment c, node
          c = nil
        end

        true
      end

      def whitespace
        return unless tok(S) || tok(SINGLE_LINE_COMMENT) || tok(COMMENT)
        ss
      end

      def process_comment(text, node)
        single_line = text =~ /^\/\//
        pre_str = single_line ? "" : @scanner.
          string[0...@scanner.pos].
          reverse[/.*?\*\/(.*?)($|\Z)/, 1].
          reverse.gsub(/[^\s]/, ' ')
        text = text.sub(/^\s*\/\//, '/*').gsub(/^\s*\/\//, ' *') + ' */' if single_line
        comment = Sass::Tree::CommentNode.new(pre_str + text, single_line)
        comment.line = @line - text.count("\n")
        node << comment
      end

      DIRECTIVES = Set[:mixin, :include, :function, :return, :debug, :warn, :for,
        :each, :while, :if, :else, :extend, :import, :media, :charset]

      def directive
        return unless tok(/@/)
        name = tok!(IDENT)
        ss

        if dir = special_directive(name)
          return dir
        end

        # Most at-rules take expressions (e.g. @import),
        # but some (e.g. @page) take selector-like arguments
        val = str {break unless expr}
        val ||= CssParser.new(@scanner, @line).parse_selector_string
        node = node(Sass::Tree::DirectiveNode.new("@#{name} #{val}".strip))

        if tok(/\{/)
          node.has_children = true
          block_contents(node, :directive)
          tok!(/\}/)
        end

        node
      end

      def special_directive(name)
        sym = name.gsub('-', '_').to_sym
        DIRECTIVES.include?(sym) && send("#{sym}_directive")
      end

      def mixin_directive
        name = tok! IDENT
        args = sass_script(:parse_mixin_definition_arglist)
        ss
        block(node(Sass::Tree::MixinDefNode.new(name, args)), :directive)
      end

      def include_directive
        name = tok! IDENT
        args, keywords = sass_script(:parse_mixin_include_arglist)
        ss
        node(Sass::Tree::MixinNode.new(name, args, keywords))
      end

      def function_directive
        name = tok! IDENT
        args = sass_script(:parse_function_definition_arglist)
        ss
        block(node(Sass::Tree::FunctionNode.new(name, args)), :function)
      end

      def return_directive
        node(Sass::Tree::ReturnNode.new(sass_script(:parse)))
      end

      def debug_directive
        node(Sass::Tree::DebugNode.new(sass_script(:parse)))
      end

      def warn_directive
        node(Sass::Tree::WarnNode.new(sass_script(:parse)))
      end

      def for_directive
        tok!(/\$/)
        var = tok! IDENT
        ss

        tok!(/from/)
        from = sass_script(:parse_until, Set["to", "through"])
        ss

        @expected = '"to" or "through"'
        exclusive = (tok(/to/) || tok!(/through/)) == 'to'
        to = sass_script(:parse)
        ss

        block(node(Sass::Tree::ForNode.new(var, from, to, exclusive)), :directive)
      end

      def each_directive
        tok!(/\$/)
        var = tok! IDENT
        ss

        tok!(/in/)
        list = sass_script(:parse)
        ss

        block(node(Sass::Tree::EachNode.new(var, list)), :directive)
      end

      def while_directive
        expr = sass_script(:parse)
        ss
        block(node(Sass::Tree::WhileNode.new(expr)), :directive)
      end

      def if_directive
        expr = sass_script(:parse)
        ss
        node = block(node(Sass::Tree::IfNode.new(expr)), :directive)
        pos = @scanner.pos
        line = @line
        ss

        else_block(node) ||
          begin
            # Backtrack in case there are any comments we want to parse
            @scanner.pos = pos
            @line = line
            node
          end
      end

      def else_block(node)
        return unless tok(/@else/)
        ss
        else_node = block(
          Sass::Tree::IfNode.new((sass_script(:parse) if tok(/if/))),
          :directive)
        node.add_else(else_node)
        pos = @scanner.pos
        line = @line
        ss

        else_block(node) ||
          begin
            # Backtrack in case there are any comments we want to parse
            @scanner.pos = pos
            @line = line
            node
          end
      end

      def else_directive
        err("Invalid CSS: @else must come after @if")
      end

      def extend_directive
        node(Sass::Tree::ExtendNode.new(expr!(:selector)))
      end

      def import_directive
        values = []

        loop do
          values << expr!(:import_arg)
          break if use_css_import? || !tok(/,\s*/)
        end

        return values
      end

      def import_arg
        return unless arg = tok(STRING) || (uri = tok!(URI))
        path = @scanner[1] || @scanner[2] || @scanner[3]
        ss

        media = str {media_query_list}.strip

        if uri || path =~ /^http:\/\// || !media.strip.empty? || use_css_import?
          return node(Sass::Tree::DirectiveNode.new("@import #{arg} #{media}".strip))
        end

        node(Sass::Tree::ImportNode.new(path.strip))
      end

      def use_css_import?; false; end

      def media_directive
        val = str {media_query_list}.strip
        block(node(Sass::Tree::MediaNode.new(val)), :directive)
      end

      # http://www.w3.org/TR/css3-mediaqueries/#syntax
      def media_query_list
        return unless media_query

        ss
        while tok(/,/)
          ss; expr!(:media_query); ss
        end

        true
      end

      def media_query
        if tok(/only|not/i)
          ss
          @expected = "media type (e.g. print, screen)"
          tok!(IDENT)
          ss
        elsif !tok(IDENT) && !media_expr
          return
        end

        ss
        while tok(/and/i)
          ss; expr!(:media_expr); ss
        end

        true
      end

      def media_expr
        return unless tok(/\(/)
        ss
        @expected = "media feature (e.g. min-device-width, color)"
        tok!(IDENT)
        ss

        if tok(/:/)
          ss; expr!(:expr)
        end
        tok!(/\)/)
        ss

        true
      end

      def charset_directive
        tok! STRING
        name = @scanner[1] || @scanner[2]
        ss
        node(Sass::Tree::CharsetNode.new(name))
      end

      def variable
        return unless tok(/\$/)
        name = tok!(IDENT)
        ss; tok!(/:/); ss

        expr = sass_script(:parse)
        guarded = tok(DEFAULT)
        node(Sass::Tree::VariableNode.new(name, expr, guarded))
      end

      def operator
        # Many of these operators (all except / and ,)
        # are disallowed by the CSS spec,
        # but they're included here for compatibility
        # with some proprietary MS properties
        str {ss if tok(/[\/,:.=]/)}
      end

      def unary_operator
        tok(/[+-]/)
      end

      def ruleset
        return unless rules = selector_sequence
        block(node(Sass::Tree::RuleNode.new(rules.flatten.compact)), :ruleset)
      end

      def block(node, context)
        node.has_children = true
        tok!(/\{/)
        block_contents(node, context)
        tok!(/\}/)
        node
      end

      # A block may contain declarations and/or rulesets
      def block_contents(node, context)
        block_given? ? yield : ss_comments(node)
        node << (child = block_child(context))
        while tok(/;/) || has_children?(child)
          block_given? ? yield : ss_comments(node)
          node << (child = block_child(context))
        end
        node
      end

      def block_child(context)
        return variable || directive if context == :function
        return variable || directive || ruleset if context == :stylesheet
        variable || directive || declaration_or_ruleset
      end

      def has_children?(child_or_array)
        return false unless child_or_array
        return child_or_array.last.has_children if child_or_array.is_a?(Array)
        return child_or_array.has_children
      end

      # This is a nasty hack, and the only place in the parser
      # that requires backtracking.
      # The reason is that we can't figure out if certain strings
      # are declarations or rulesets with fixed finite lookahead.
      # For example, "foo:bar baz baz baz..." could be either a property
      # or a selector.
      #
      # To handle this, we simply check if it works as a property
      # (which is the most common case)
      # and, if it doesn't, try it as a ruleset.
      #
      # We could eke some more efficiency out of this
      # by handling some easy cases (first token isn't an identifier,
      # no colon after the identifier, whitespace after the colon),
      # but I'm not sure the gains would be worth the added complexity.
      def declaration_or_ruleset
        old_use_property_exception, @use_property_exception =
          @use_property_exception, false
        decl_err = catch_error do
          decl = declaration
          unless decl && decl.has_children
            # We want an exception if it's not there,
            # but we don't want to consume if it is
            tok!(/[;}]/) unless tok?(/[;}]/)
          end
          return decl
        end

        ruleset_err = catch_error {return ruleset}
        rethrow(@use_property_exception ? decl_err : ruleset_err)
      ensure
        @use_property_exception = old_use_property_exception
      end

      def selector_sequence
        if sel = tok(STATIC_SELECTOR)
          return [sel]
        end

        rules = []
        return unless v = selector
        rules.concat v

        ws = ''
        while tok(/,/)
          ws << str {ss}
          if v = selector
            rules << ',' << ws
            rules.concat v
            ws = ''
          end
        end
        rules
      end

      def selector
        return unless sel = _selector
        sel.to_a
      end

      def selector_comma_sequence
        return unless sel = _selector
        selectors = [sel]
        ws = ''
        while tok(/,/)
          ws << str{ss}
          if sel = _selector
            selectors << sel
            selectors[-1] = Selector::Sequence.new(["\n"] + selectors.last.members) if ws.include?("\n")
            ws = ''
          end
        end
        Selector::CommaSequence.new(selectors)
      end

      def _selector
        # The combinator here allows the "> E" hack
        return unless val = combinator || simple_selector_sequence
        nl = str{ss}.include?("\n")
        res = []
        res << val
        res << "\n" if nl

        while val = combinator || simple_selector_sequence
          res << val
          res << "\n" if str{ss}.include?("\n")
        end
        Selector::Sequence.new(res.compact)
      end

      def combinator
        tok(PLUS) || tok(GREATER) || tok(TILDE)
      end

      def simple_selector_sequence
        # This allows for stuff like http://www.w3.org/TR/css3-animations/#keyframes-
        return expr unless e = element_name || id_selector || class_selector ||
          attrib || negation || pseudo || parent_selector || interpolation_selector
        res = [e]

        # The tok(/\*/) allows the "E*" hack
        while v = element_name || id_selector || class_selector ||
            attrib || negation || pseudo || interpolation_selector ||
            (tok(/\*/) && Selector::Universal.new(nil))
          res << v
        end

        if tok?(/&/)
          begin
            expected('"{"')
          rescue Sass::SyntaxError => e
            e.message << "\n\n" << <<MESSAGE
In Sass 3, the parent selector & can only be used where element names are valid,
since it could potentially be replaced by an element name.
MESSAGE
            raise e
          end
        end

        Selector::SimpleSequence.new(res)
      end

      def parent_selector
        return unless tok(/&/)
        Selector::Parent.new
      end

      def class_selector
        return unless tok(/\./)
        @expected = "class name"
        Selector::Class.new(merge(expr!(:interp_ident)))
      end

      def id_selector
        return unless tok(/#(?!\{)/)
        @expected = "id name"
        Selector::Id.new(merge(expr!(:interp_name)))
      end

      def element_name
        return unless name = interp_ident || tok(/\*/) || (tok?(/\|/) && "")
        if tok(/\|/)
          @expected = "element name or *"
          ns = name
          name = interp_ident || tok!(/\*/)
        end

        if name == '*'
          Selector::Universal.new(merge(ns))
        else
          Selector::Element.new(merge(name), merge(ns))
        end
      end

      def interpolation_selector
        return unless script = interpolation
        Selector::Interpolation.new(script)
      end

      def attrib
        return unless tok(/\[/)
        ss
        ns, name = attrib_name!
        ss

        if op = tok(/=/) ||
            tok(INCLUDES) ||
            tok(DASHMATCH) ||
            tok(PREFIXMATCH) ||
            tok(SUFFIXMATCH) ||
            tok(SUBSTRINGMATCH)
          @expected = "identifier or string"
          ss
          if val = tok(IDENT)
            val = [val]
          else
            val = expr!(:interp_string)
          end
          ss
        end
        tok(/\]/)

        Selector::Attribute.new(merge(name), merge(ns), op, merge(val))
      end

      def attrib_name!
        if name_or_ns = interp_ident
          # E, E|E
          if tok(/\|(?!=)/)
            ns = name_or_ns
            name = interp_ident
          else
            name = name_or_ns
          end
        else
          # *|E or |E
          ns = [tok(/\*/) || ""]
          tok!(/\|/)
          name = expr!(:interp_ident)
        end
        return ns, name
      end

      def pseudo
        return unless s = tok(/::?/)
        @expected = "pseudoclass or pseudoelement"
        name = expr!(:interp_ident)
        if tok(/\(/)
          ss
          arg = expr!(:pseudo_expr)
          tok!(/\)/)
        end
        Selector::Pseudo.new(s == ':' ? :class : :element, merge(name), merge(arg))
      end

      def pseudo_expr
        return unless e = tok(PLUS) || tok(/-/) || tok(NUMBER) ||
          interp_string || tok(IDENT) || interpolation
        res = [e, str{ss}]
        while e = tok(PLUS) || tok(/-/) || tok(NUMBER) ||
            interp_string || tok(IDENT) || interpolation
          res << e << str{ss}
        end
        res
      end

      def negation
        return unless name = tok(NOT) || tok(MOZ_ANY)
        ss
        @expected = "selector"
        sel = selector_comma_sequence
        tok!(/\)/)
        Selector::SelectorPseudoClass.new(name[1...-1], sel)
      end

      def declaration
        # This allows the "*prop: val", ":prop: val", and ".prop: val" hacks
        if s = tok(/[:\*\.]|\#(?!\{)/)
          @use_property_exception = s !~ /[\.\#]/
          name = [s, str{ss}, *expr!(:interp_ident)]
        else
          return unless name = interp_ident
          name = [name] if name.is_a?(String)
        end
        if comment = tok(COMMENT)
          name << comment
        end
        ss

        tok!(/:/)
        space, value = value!
        ss
        require_block = tok?(/\{/)

        node = node(Sass::Tree::PropNode.new(name.flatten.compact, value, :new))

        return node unless require_block
        nested_properties! node, space
      end

      def value!
        space = !str {ss}.empty?
        @use_property_exception ||= space || !tok?(IDENT)

        return true, Sass::Script::String.new("") if tok?(/\{/)
        # This is a bit of a dirty trick:
        # if the value is completely static,
        # we don't parse it at all, and instead return a plain old string
        # containing the value.
        # This results in a dramatic speed increase.
        if val = tok(STATIC_VALUE)
          return space, Sass::Script::String.new(val.strip)
        end
        return space, sass_script(:parse)
      end

      def plain_value
        return unless tok(/:/)
        space = !str {ss}.empty?
        @use_property_exception ||= space || !tok?(IDENT)

        expression = expr
        expression << tok(IMPORTANT) if expression
        # expression, space, value
        return expression, space, expression || [""]
      end

      def nested_properties!(node, space)
        err(<<MESSAGE) unless space
Invalid CSS: a space is required between a property and its definition
when it has other properties nested beneath it.
MESSAGE

        @use_property_exception = true
        @expected = 'expression (e.g. 1px, bold) or "{"'
        block(node, :property)
      end

      def expr
        return unless t = term
        res = [t, str{ss}]

        while (o = operator) && (t = term)
          res << o << t << str{ss}
        end

        res
      end

      def term
        unless e = tok(NUMBER) ||
            tok(URI) ||
            function ||
            tok(STRING) ||
            tok(UNICODERANGE) ||
            tok(IDENT) ||
            tok(HEXCOLOR)

          return unless op = unary_operator
          @expected = "number or function"
          return [op, tok(NUMBER) || expr!(:function)]
        end
        e
      end

      def function
        return unless name = tok(FUNCTION)
        if name == "expression(" || name == "calc("
          str, _ = Sass::Shared.balance(@scanner, ?(, ?), 1)
          [name, str]
        else
          [name, str{ss}, expr, tok!(/\)/)]
        end
      end

      def interpolation
        return unless tok(INTERP_START)
        sass_script(:parse_interpolated)
      end

      def interp_string
        _interp_string(:double) || _interp_string(:single)
      end

      def _interp_string(type)
        return unless start = tok(Sass::Script::Lexer::STRING_REGULAR_EXPRESSIONS[[type, false]])
        res = [start]

        mid_re = Sass::Script::Lexer::STRING_REGULAR_EXPRESSIONS[[type, true]]
        # @scanner[2].empty? means we've started an interpolated section
        while @scanner[2] == '#{'
          @scanner.pos -= 2 # Don't consume the #{
          res.last.slice!(-2..-1)
          res << expr!(:interpolation) << tok(mid_re)
        end
        res
      end

      def interp_ident(start = IDENT)
        return unless val = tok(start) || interpolation
        res = [val]
        while val = tok(NAME) || interpolation
          res << val
        end
        res
      end

      def interp_name
        interp_ident NAME
      end

      def str
        @strs.push ""
        yield
        @strs.last
      ensure
        @strs.pop
      end

      def str?
        @strs.push ""
        yield && @strs.last
      ensure
        @strs.pop
      end

      def node(node)
        node.line = @line
        node
      end

      @sass_script_parser = Class.new(Sass::Script::Parser)
      @sass_script_parser.send(:include, ScriptParser)
      # @private
      def self.sass_script_parser; @sass_script_parser; end

      def sass_script(*args)
        parser = self.class.sass_script_parser.new(@scanner, @line,
          @scanner.pos - (@scanner.string[0...@scanner.pos].rindex("\n") || 0))
        result = parser.send(*args)
        @line = parser.line
        result
      rescue Sass::SyntaxError => e
        throw(:_sass_parser_error, true) if @throw_error
        raise e
      end

      def merge(arr)
        arr && Sass::Util.merge_adjacent_strings([arr].flatten)
      end

      EXPR_NAMES = {
        :media_query => "media query (e.g. print, screen, print and screen)",
        :media_expr => "media expression (e.g. (min-device-width: 800px)))",
        :pseudo_expr => "expression (e.g. fr, 2n+1)",
        :interp_ident => "identifier",
        :interp_name => "identifier",
        :expr => "expression (e.g. 1px, bold)",
        :_selector => "selector",
        :selector_comma_sequence => "selector",
        :simple_selector_sequence => "selector",
        :import_arg => "file to import (string or url())",
      }

      TOK_NAMES = Sass::Util.to_hash(
        Sass::SCSS::RX.constants.map {|c| [Sass::SCSS::RX.const_get(c), c.downcase]}).
        merge(IDENT => "identifier", /[;}]/ => '";"')

      def tok?(rx)
        @scanner.match?(rx)
      end

      def expr!(name)
        (e = send(name)) && (return e)
        expected(EXPR_NAMES[name] || name.to_s)
      end

      def tok!(rx)
        (t = tok(rx)) && (return t)
        name = TOK_NAMES[rx]

        unless name
          # Display basic regexps as plain old strings
          string = rx.source.gsub(/\\(.)/, '\1')
          name = rx.source == Regexp.escape(string) ? string.inspect : rx.inspect
        end

        expected(name)
      end

      def expected(name)
        throw(:_sass_parser_error, true) if @throw_error
        self.class.expected(@scanner, @expected || name, @line)
      end

      def err(msg)
        throw(:_sass_parser_error, true) if @throw_error
        raise Sass::SyntaxError.new(msg, :line => @line)
      end

      def catch_error(&block)
        old_throw_error, @throw_error = @throw_error, true
        pos = @scanner.pos
        line = @line
        expected = @expected
        if catch(:_sass_parser_error, &block)
          @scanner.pos = pos
          @line = line
          @expected = expected
          {:pos => pos, :line => line, :expected => @expected, :block => block}
        end
      ensure
        @throw_error = old_throw_error
      end

      def rethrow(err)
        if @throw_err
          throw :_sass_parser_error, err
        else
          @scanner = StringScanner.new(@scanner.string)
          @scanner.pos = err[:pos]
          @line = err[:line]
          @expected = err[:expected]
          err[:block].call
        end
      end

      # @private
      def self.expected(scanner, expected, line)
        pos = scanner.pos

        after = scanner.string[0...pos]
        # Get rid of whitespace between pos and the last token,
        # but only if there's a newline in there
        after.gsub!(/\s*\n\s*$/, '')
        # Also get rid of stuff before the last newline
        after.gsub!(/.*\n/, '')
        after = "..." + after[-15..-1] if after.size > 18

        was = scanner.rest.dup
        # Get rid of whitespace between pos and the next token,
        # but only if there's a newline in there
        was.gsub!(/^\s*\n\s*/, '')
        # Also get rid of stuff after the next newline
        was.gsub!(/\n.*/, '')
        was = was[0...15] + "..." if was.size > 18

        raise Sass::SyntaxError.new(
          "Invalid CSS after \"#{after}\": expected #{expected}, was \"#{was}\"",
          :line => line)
      end

      # Avoid allocating lots of new strings for `#tok`.
      # This is important because `#tok` is called all the time.
      NEWLINE = "\n"

      def tok(rx)
        res = @scanner.scan(rx)
        if res
          @line += res.count(NEWLINE)
          @expected = nil
          if !@strs.empty? && rx != COMMENT && rx != SINGLE_LINE_COMMENT
            @strs.each {|s| s << res}
          end
          res
        end
      end
    end
  end
end
module Sass
  module SCSS
    # A subclass of {Parser} that parses code in Sass documents
    # using some SCSS constructs.
    # This is necessary because SassScript in Sass supports `!`-style variables,
    # whereas in SCSS it doesn't.
    class SassParser < Parser
      @sass_script_parser = Sass::Script::Parser
    end
  end
end
module Sass
  module SCSS
    # A parser for a static SCSS tree.
    # Parses with SCSS extensions, like nested rules and parent selectors,
    # but without dynamic SassScript.
    # This is useful for e.g. \{#parse\_selector parsing selectors}
    # after resolving the interpolation.
    class StaticParser < Parser
      # Parses the text as a selector.
      #
      # @param filename [String, nil] The file in which the selector appears,
      #   or nil if there is no such file.
      #   Used for error reporting.
      # @return [Selector::CommaSequence] The parsed selector
      # @raise [Sass::SyntaxError] if there's a syntax error in the selector
      def parse_selector(filename)
        init_scanner!
        seq = expr!(:selector_comma_sequence)
        expected("selector") unless @scanner.eos?
        seq.line = @line
        seq.filename = filename
        seq
      end

      private

      def variable; nil; end
      def script_value; nil; end
      def interpolation; nil; end
      def interp_string; s = tok(STRING) and [s]; end
      def interp_ident(ident = IDENT); s = tok(ident) and [s]; end
      def use_css_import?; true; end

      def special_directive(name)
        return unless  %w[media import charset].include?(name)
        super
      end
    end
  end
end
module Sass
  module Script
    # This is a subclass of {Lexer} for use in parsing plain CSS properties.
    #
    # @see Sass::SCSS::CssParser
    class CssLexer < Lexer
      private

      def token
        important || super
      end

      def string(re, *args)
        if re == :uri
          return unless uri = scan(URI)
          return [:string, Script::String.new(uri)]
        end

        return unless scan(STRING)
        [:string, Script::String.new((@scanner[1] || @scanner[2]).gsub(/\\(['"])/, '\1'), :string)]
      end

      def important
        return unless s = scan(IMPORTANT)
        [:raw, s]
      end
    end
  end
end

module Sass
  module Script
    # This is a subclass of {Parser} for use in parsing plain CSS properties.
    #
    # @see Sass::SCSS::CssParser
    class CssParser < Parser
      private

      # @private
      def lexer_class; CssLexer; end

      # We need a production that only does /,
      # since * and % aren't allowed in plain CSS
      production :div, :unary_plus, :div

      def string
        return number unless tok = try_tok(:string)
        return tok.value unless @lexer.peek && @lexer.peek.type == :begin_interpolation
      end

      # Short-circuit all the SassScript-only productions
      alias_method :interpolation, :space
      alias_method :or_expr, :div
      alias_method :unary_div, :ident
      alias_method :paren, :string
    end
  end
end

module Sass
  module SCSS
    # This is a subclass of {Parser} which only parses plain CSS.
    # It doesn't support any Sass extensions, such as interpolation,
    # parent references, nested selectors, and so forth.
    # It does support all the same CSS hacks as the SCSS parser, though.
    class CssParser < StaticParser
      # Parse a selector, and return its value as a string.
      #
      # @return [String, nil] The parsed selector, or nil if no selector was parsed
      # @raise [Sass::SyntaxError] if there's a syntax error in the selector
      def parse_selector_string
        init_scanner!
        str {return unless selector}
      end

      private

      def parent_selector; nil; end
      def interpolation; nil; end
      def interp_string; tok(STRING); end
      def interp_ident(ident = IDENT); tok(ident); end
      def use_css_import?; true; end

      def block_child(context)
        case context
        when :ruleset
          declaration
        when :stylesheet
          directive || ruleset
        when :directive
          directive || declaration_or_ruleset
        end
      end

      def nested_properties!(node, space)
        expected('expression (e.g. 1px, bold)');
      end

      @sass_script_parser = Class.new(Sass::Script::CssParser)
      @sass_script_parser.send(:include, ScriptParser)
    end
  end
end

module Sass
  # SCSS is the CSS syntax for Sass.
  # It parses into the same syntax tree as Sass,
  # and generates the same sort of output CSS.
  #
  # This module contains code for the parsing of SCSS.
  # The evaluation is handled by the broader {Sass} module.
  module SCSS; end
end
module Sass
  # An exception class that keeps track of
  # the line of the Sass template it was raised on
  # and the Sass file that was being parsed (if applicable).
  #
  # All Sass errors are raised as {Sass::SyntaxError}s.
  #
  # When dealing with SyntaxErrors,
  # it's important to provide filename and line number information.
  # This will be used in various error reports to users, including backtraces;
  # see \{#sass\_backtrace} for details.
  #
  # Some of this information is usually provided as part of the constructor.
  # New backtrace entries can be added with \{#add\_backtrace},
  # which is called when an exception is raised between files (e.g. with `@import`).
  #
  # Often, a chunk of code will all have similar backtrace information -
  # the same filename or even line.
  # It may also be useful to have a default line number set.
  # In those situations, the default values can be used
  # by omitting the information on the original exception,
  # and then calling \{#modify\_backtrace} in a wrapper `rescue`.
  # When doing this, be sure that all exceptions ultimately end up
  # with the information filled in.
  class SyntaxError < StandardError
    # The backtrace of the error within Sass files.
    # This is an array of hashes containing information for a single entry.
    # The hashes have the following keys:
    #
    # `:filename`
    # : The name of the file in which the exception was raised,
    #   or `nil` if no filename is available.
    #
    # `:mixin`
    # : The name of the mixin in which the exception was raised,
    #   or `nil` if it wasn't raised in a mixin.
    #
    # `:line`
    # : The line of the file on which the error occurred. Never nil.
    #
    # This information is also included in standard backtrace format
    # in the output of \{#backtrace}.
    #
    # @return [Aray<{Symbol => Object>}]
    attr_accessor :sass_backtrace

    # The text of the template where this error was raised.
    #
    # @return [String]
    attr_accessor :sass_template

    # @param msg [String] The error message
    # @param attrs [{Symbol => Object}] The information in the backtrace entry.
    #   See \{#sass\_backtrace}
    def initialize(msg, attrs = {})
      @message = msg
      @sass_backtrace = []
      add_backtrace(attrs)
    end

    # The name of the file in which the exception was raised.
    # This could be `nil` if no filename is available.
    #
    # @return [String, nil]
    def sass_filename
      sass_backtrace.first[:filename]
    end

    # The name of the mixin in which the error occurred.
    # This could be `nil` if the error occurred outside a mixin.
    #
    # @return [Fixnum]
    def sass_mixin
      sass_backtrace.first[:mixin]
    end

    # The line of the Sass template on which the error occurred.
    #
    # @return [Fixnum]
    def sass_line
      sass_backtrace.first[:line]
    end

    # Adds an entry to the exception's Sass backtrace.
    #
    # @param attrs [{Symbol => Object}] The information in the backtrace entry.
    #   See \{#sass\_backtrace}
    def add_backtrace(attrs)
      sass_backtrace << attrs.reject {|k, v| v.nil?}
    end

    # Modify the top Sass backtrace entries
    # (that is, the most deeply nested ones)
    # to have the given attributes.
    #
    # Specifically, this goes through the backtrace entries
    # from most deeply nested to least,
    # setting the given attributes for each entry.
    # If an entry already has one of the given attributes set,
    # the pre-existing attribute takes precedence
    # and is not used for less deeply-nested entries
    # (even if they don't have that attribute set).
    #
    # @param attrs [{Symbol => Object}] The information to add to the backtrace entry.
    #   See \{#sass\_backtrace}
    def modify_backtrace(attrs)
      attrs = attrs.reject {|k, v| v.nil?}
      # Move backwards through the backtrace
      (0...sass_backtrace.size).to_a.reverse.each do |i|
        entry = sass_backtrace[i]
        sass_backtrace[i] = attrs.merge(entry)
        attrs.reject! {|k, v| entry.include?(k)}
        break if attrs.empty?
      end
    end

    # @return [String] The error message
    def to_s
      @message
    end

    # Returns the standard exception backtrace,
    # including the Sass backtrace.
    #
    # @return [Array<String>]
    def backtrace
      return nil if super.nil?
      return super if sass_backtrace.all? {|h| h.empty?}
      sass_backtrace.map do |h|
        "#{h[:filename] || "(sass)"}:#{h[:line]}" +
          (h[:mixin] ? ":in `#{h[:mixin]}'" : "")
      end + super
    end

    # Returns a string representation of the Sass backtrace.
    #
    # @param default_filename [String] The filename to use for unknown files
    # @see #sass_backtrace
    # @return [String]
    def sass_backtrace_str(default_filename = "an unknown file")
      lines = self.message.split("\n")
      msg = lines[0] + lines[1..-1].
        map {|l| "\n" + (" " * "Syntax error: ".size) + l}.join
      "Syntax error: #{msg}" +
        Sass::Util.enum_with_index(sass_backtrace).map do |entry, i|
        "\n        #{i == 0 ? "on" : "from"} line #{entry[:line]}" +
          " of #{entry[:filename] || default_filename}" +
          (entry[:mixin] ? ", in `#{entry[:mixin]}'" : "")
      end.join
    end

    class << self
      # Returns an error report for an exception in CSS format.
      #
      # @param e [Exception]
      # @param options [{Symbol => Object}] The options passed to {Sass::Engine#initialize}
      # @return [String] The error report
      # @raise [Exception] `e`, if the
      #   {file:SASS_REFERENCE.md#full_exception-option `:full_exception`} option
      #   is set to false.
      def exception_to_css(e, options)
        raise e unless options[:full_exception]

        header = header_string(e, options)

        <<END
/*
#{header}

Backtrace:\n#{e.backtrace.join("\n")}
*/
body:before {
  white-space: pre;
  font-family: monospace;
  content: "#{header.gsub('"', '\"').gsub("\n", '\\A ')}"; }
END
      end

      private

      def header_string(e, options)
        unless e.is_a?(Sass::SyntaxError) && e.sass_line && e.sass_template
          return "#{e.class}: #{e.message}"
        end

        line_offset = options[:line] || 1
        line_num = e.sass_line + 1 - line_offset
        min = [line_num - 6, 0].max
        section = e.sass_template.rstrip.split("\n")[min ... line_num + 5]
        return e.sass_backtrace_str if section.nil? || section.empty?

        e.sass_backtrace_str + "\n\n" + Sass::Util.enum_with_index(section).
          map {|line, i| "#{line_offset + min + i}: #{line}"}.join("\n")
      end
    end
  end

  # The class for Sass errors that are raised due to invalid unit conversions
  # in SassScript.
  class UnitConversionError < SyntaxError; end
end
module Sass
  # Sass importers are in charge of taking paths passed to `@import`
  # and finding the appropriate Sass code for those paths.
  # By default, this code is always loaded from the filesystem,
  # but importers could be added to load from a database or over HTTP.
  #
  # Each importer is in charge of a single load path
  # (or whatever the corresponding notion is for the backend).
  # Importers can be placed in the {file:SASS_REFERENCE.md#load_paths-option `:load_paths` array}
  # alongside normal filesystem paths.
  #
  # When resolving an `@import`, Sass will go through the load paths
  # looking for an importer that successfully imports the path.
  # Once one is found, the imported file is used.
  #
  # User-created importers must inherit from {Importers::Base}.
  module Importers
  end
end

module Sass
  module Importers
    # The abstract base class for Sass importers.
    # All importers should inherit from this.
    #
    # At the most basic level, an importer is given a string
    # and must return a {Sass::Engine} containing some Sass code.
    # This string can be interpreted however the importer wants;
    # however, subclasses are encouraged to use the URI format
    # for pathnames.
    #
    # Importers that have some notion of "relative imports"
    # should take a single load path in their constructor,
    # and interpret paths as relative to that.
    # They should also implement the \{#find\_relative} method.
    #
    # Importers should be serializable via `Marshal.dump`.
    # In addition to the standard `_dump` and `_load` methods,
    # importers can define `_before_dump`, `_after_dump`, `_around_dump`,
    # and `_after_load` methods as per {Sass::Util#dump} and {Sass::Util#load}.
    #
    # @abstract
    class Base

      # Find a Sass file relative to another file.
      # Importers without a notion of "relative paths"
      # should just return nil here.
      #
      # If the importer does have a notion of "relative paths",
      # it should ignore its load path during this method.
      #
      # See \{#find} for important information on how this method should behave.
      #
      # The `:filename` option passed to the returned {Sass::Engine}
      # should be of a format that could be passed to \{#find}.
      #
      # @param uri [String] The URI to import. This is not necessarily relative,
      #   but this method should only return true if it is.
      # @param base [String] The base filename. If `uri` is relative,
      #   it should be interpreted as relative to `base`.
      #   `base` is guaranteed to be in a format importable by this importer.
      # @param options [{Symbol => Object}] Options for the Sass file
      #   containing the `@import` that's currently being resolved.
      # @return [Sass::Engine, nil] An Engine containing the imported file,
      #   or nil if it couldn't be found or was in the wrong format.
      def find_relative(uri, base, options)
        Sass::Util.abstract(self)
      end

      # Find a Sass file, if it exists.
      #
      # This is the primary entry point of the Importer.
      # It corresponds directly to an `@import` statement in Sass.
      # It should do three basic things:
      #
      # * Determine if the URI is in this importer's format.
      #   If not, return nil.
      # * Determine if the file indicated by the URI actually exists and is readable.
      #   If not, return nil.
      # * Read the file and place the contents in a {Sass::Engine}.
      #   Return that engine.
      #
      # If this importer's format allows for file extensions,
      # it should treat them the same way as the default {Filesystem} importer.
      # If the URI explicitly has a `.sass` or `.scss` filename,
      # the importer should look for that exact file
      # and import it as the syntax indicated.
      # If it doesn't exist, the importer should return nil.
      #
      # If the URI doesn't have either of these extensions,
      # the importer should look for files with the extensions.
      # If no such files exist, it should return nil.
      #
      # The {Sass::Engine} to be returned should be passed `options`,
      # with a few modifications. `:filename` and `:syntax` should be set appropriately,
      # and `:importer` should be set to this importer.
      #
      # @param uri [String] The URI to import.
      # @param options [{Symbol => Object}] Options for the Sass file
      #   containing the `@import` that's currently being resolved.
      #   This is safe for subclasses to modify destructively.
      #   Callers should only pass in a value they don't mind being destructively modified.
      # @return [Sass::Engine, nil] An Engine containing the imported file,
      #   or nil if it couldn't be found or was in the wrong format.
      def find(uri, options)
        Sass::Util.abstract(self)
      end

      # Returns the time the given Sass file was last modified.
      #
      # If the given file has been deleted or the time can't be accessed
      # for some other reason, this should return nil.
      #
      # @param uri [String] The URI of the file to check.
      #   Comes from a `:filename` option set on an engine returned by this importer.
      # @param options [{Symbol => Objet}] Options for the Sass file
      #   containing the `@import` currently being checked.
      # @return [Time, nil]
      def mtime(uri, options)
        Sass::Util.abstract(self)
      end

      # Get the cache key pair for the given Sass URI.
      # The URI need not be checked for validity.
      #
      # The only strict requirement is that the returned pair of strings
      # uniquely identify the file at the given URI.
      # However, the first component generally corresponds roughly to the directory,
      # and the second to the basename, of the URI.
      #
      # Note that keys must be unique *across importers*.
      # Thus it's probably a good idea to include the importer name
      # at the beginning of the first component.
      #
      # @param uri [String] A URI known to be valid for this importer.
      # @param options [{Symbol => Object}] Options for the Sass file
      #   containing the `@import` currently being checked.
      # @return [(String, String)] The key pair which uniquely identifies
      #   the file at the given URI.
      def key(uri, options)
        Sass::Util.abstract(self)
      end

      # A string representation of the importer.
      # Should be overridden by subclasses.
      #
      # This is used to help debugging,
      # and should usually just show the load path encapsulated by this importer.
      #
      # @return [String]
      def to_s
        Sass::Util.abstract(self)
      end
    end
  end
end

      
require 'pathname'

module Sass
  module Importers
    # The default importer, used for any strings found in the load path.
    # Simply loads Sass files from the filesystem using the default logic.
    class Filesystem < Base

      attr_accessor :root

      # Creates a new filesystem importer that imports files relative to a given path.
      #
      # @param root [String] The root path.
      #   This importer will import files relative to this path.
      def initialize(root)
        @root = root
      end

      # @see Base#find_relative
      def find_relative(name, base, options)
        _find(File.dirname(base), name, options)
      end

      # @see Base#find
      def find(name, options)
        _find(@root, name, options)
      end

      # @see Base#mtime
      def mtime(name, options)
        file, s = find_real_file(@root, name)
        File.mtime(file) if file
      rescue Errno::ENOENT
        nil
      end

      # @see Base#key
      def key(name, options)
        [self.class.name + ":" + File.dirname(File.expand_path(name)),
          File.basename(name)]
      end

      # @see Base#to_s
      def to_s
        @root
      end

      protected

      # If a full uri is passed, this removes the root from it
      # otherwise returns the name unchanged
      def remove_root(name)
        root = @root.end_with?('/') ? @root : @root + '/'
        if name.index(root) == 0
          name[root.length..-1]
        else
          name
        end
      end

      # A hash from file extensions to the syntaxes for those extensions.
      # The syntaxes must be `:sass` or `:scss`.
      #
      # This can be overridden by subclasses that want normal filesystem importing
      # with unusual extensions.
      #
      # @return [{String => Symbol}]
      def extensions
        {'sass' => :sass, 'scss' => :scss}
      end

      # Given an `@import`ed path, returns an array of possible
      # on-disk filenames and their corresponding syntaxes for that path.
      #
      # @param name [String] The filename.
      # @return [Array(String, Symbol)] An array of pairs.
      #   The first element of each pair is a filename to look for;
      #   the second element is the syntax that file would be in (`:sass` or `:scss`).
      def possible_files(name)
        dirname, basename, extname = split(name)
        sorted_exts = extensions.sort
        syntax = extensions[extname]

        return [["#{dirname}/{_,}#{basename}.#{extensions.invert[syntax]}", syntax]] if syntax
        sorted_exts.map {|ext, syn| ["#{dirname}/{_,}#{basename}.#{ext}", syn]}
      end


      REDUNDANT_DIRECTORY = %r{#{Regexp.escape(File::SEPARATOR)}\.#{Regexp.escape(File::SEPARATOR)}}
      # Given a base directory and an `@import`ed name,
      # finds an existant file that matches the name.
      #
      # @param dir [String] The directory relative to which to search.
      # @param name [String] The filename to search for.
      # @return [(String, Symbol)] A filename-syntax pair.
      def find_real_file(dir, name)
        for (f,s) in possible_files(remove_root(name))
          path = (dir == ".") ? f : "#{dir}/#{f}"
          if full_path = Dir[path].first
            full_path.gsub!(REDUNDANT_DIRECTORY,File::SEPARATOR)
            return full_path, s
          end
        end
        nil
      end

      # Splits a filename into three parts, a directory part, a basename, and an extension
      # Only the known extensions returned from the extensions method will be recognized as such.
      def split(name)
        extension = nil
        dirname, basename = File.dirname(name), File.basename(name)
        if basename =~ /^(.*)\.(#{extensions.keys.map{|e| Regexp.escape(e)}.join('|')})$/
          basename = $1
          extension = $2
        end
        [dirname, basename, extension]
      end

      def hash
        @root.hash
      end

      def eql?(other)
        root.eql?(other.root)
      end

      private

      def _find(dir, name, options)
        full_filename, syntax = find_real_file(dir, name)
        return unless full_filename && File.readable?(full_filename)

        options[:syntax] = syntax
        options[:filename] = full_filename
        options[:importer] = self
        Sass::Engine.new(File.read(full_filename), options)
      end

      def join(base, path)
        Pathname.new(base).join(path).to_s
      end
    end
  end
end
require 'strscan'

module Sass
  # This module contains functionality that's shared between Haml and Sass.
  module Shared
    extend self

    # Scans through a string looking for the interoplation-opening `#{`
    # and, when it's found, yields the scanner to the calling code
    # so it can handle it properly.
    #
    # The scanner will have any backslashes immediately in front of the `#{`
    # as the second capture group (`scan[2]`),
    # and the text prior to that as the first (`scan[1]`).
    #
    # @yieldparam scan [StringScanner] The scanner scanning through the string
    # @return [String] The text remaining in the scanner after all `#{`s have been processed
    def handle_interpolation(str)
      scan = StringScanner.new(str)
      yield scan while scan.scan(/(.*?)(\\*)\#\{/)
      scan.rest
    end

    # Moves a scanner through a balanced pair of characters.
    # For example:
    #
    #     Foo (Bar (Baz bang) bop) (Bang (bop bip))
    #     ^                       ^
    #     from                    to
    #
    # @param scanner [StringScanner] The string scanner to move
    # @param start [Character] The character opening the balanced pair.
    #   A `Fixnum` in 1.8, a `String` in 1.9
    # @param finish [Character] The character closing the balanced pair.
    #   A `Fixnum` in 1.8, a `String` in 1.9
    # @param count [Fixnum] The number of opening characters matched
    #   before calling this method
    # @return [(String, String)] The string matched within the balanced pair
    #   and the rest of the string.
    #   `["Foo (Bar (Baz bang) bop)", " (Bang (bop bip))"]` in the example above.
    def balance(scanner, start, finish, count = 0)
      str = ''
      scanner = StringScanner.new(scanner) unless scanner.is_a? StringScanner
      regexp = Regexp.new("(.*?)[\\#{start.chr}\\#{finish.chr}]", Regexp::MULTILINE)
      while scanner.scan(regexp)
        str << scanner.matched
        count += 1 if scanner.matched[-1] == start
        count -= 1 if scanner.matched[-1] == finish
        return [str.strip, scanner.rest] if count == 0
      end
    end

    # Formats a string for use in error messages about indentation.
    #
    # @param indentation [String] The string used for indentation
    # @param was [Boolean] Whether or not to add `"was"` or `"were"`
    #   (depending on how many characters were in `indentation`)
    # @return [String] The name of the indentation (e.g. `"12 spaces"`, `"1 tab"`)
    def human_indentation(indentation, was = false)
      if !indentation.include?(?\t)
        noun = 'space'
      elsif !indentation.include?(?\s)
        noun = 'tab'
      else
        return indentation.inspect + (was ? ' was' : '')
      end

      singular = indentation.length == 1
      if was
        was = singular ? ' was' : ' were'
      else
        was = ''
      end

      "#{indentation.length} #{noun}#{'s' unless singular}#{was}"
    end
  end
end

module Sass

  # A Sass mixin or function.
  #
  # `name`: `String`
  # : The name of the mixin/function.
  #
  # `args`: `Array<(String, Script::Node)>`
  # : The arguments for the mixin/function.
  #   Each element is a tuple containing the name of the argument
  #   and the parse tree for the default value of the argument.
  #
  # `environment`: {Sass::Environment}
  # : The environment in which the mixin/function was defined.
  #   This is captured so that the mixin/function can have access
  #   to local variables defined in its scope.
  #
  # `tree`: `Array<Tree::Node>`
  # : The parse tree for the mixin/function.
  Callable = Struct.new(:name, :args, :environment, :tree)

  # This class handles the parsing and compilation of the Sass template.
  # Example usage:
  #
  #     template = File.load('stylesheets/sassy.sass')
  #     sass_engine = Sass::Engine.new(template)
  #     output = sass_engine.render
  #     puts output
  class Engine
    include Sass::Util

    # A line of Sass code.
    #
    # `text`: `String`
    # : The text in the line, without any whitespace at the beginning or end.
    #
    # `tabs`: `Fixnum`
    # : The level of indentation of the line.
    #
    # `index`: `Fixnum`
    # : The line number in the original document.
    #
    # `offset`: `Fixnum`
    # : The number of bytes in on the line that the text begins.
    #   This ends up being the number of bytes of leading whitespace.
    #
    # `filename`: `String`
    # : The name of the file in which this line appeared.
    #
    # `children`: `Array<Line>`
    # : The lines nested below this one.
    class Line < Struct.new(:text, :tabs, :index, :offset, :filename, :children)
      def comment?
        text[0] == COMMENT_CHAR && (text[1] == SASS_COMMENT_CHAR || text[1] == CSS_COMMENT_CHAR)
      end
    end

    # The character that begins a CSS property.
    PROPERTY_CHAR  = ?:

    # The character that designates the beginning of a comment,
    # either Sass or CSS.
    COMMENT_CHAR = ?/

    # The character that follows the general COMMENT_CHAR and designates a Sass comment,
    # which is not output as a CSS comment.
    SASS_COMMENT_CHAR = ?/

    # The character that follows the general COMMENT_CHAR and designates a CSS comment,
    # which is embedded in the CSS document.
    CSS_COMMENT_CHAR = ?*

    # The character used to denote a compiler directive.
    DIRECTIVE_CHAR = ?@

    # Designates a non-parsed rule.
    ESCAPE_CHAR    = ?\\

    # Designates block as mixin definition rather than CSS rules to output
    MIXIN_DEFINITION_CHAR = ?=

    # Includes named mixin declared using MIXIN_DEFINITION_CHAR
    MIXIN_INCLUDE_CHAR    = ?+

    # The regex that matches and extracts data from
    # properties of the form `:name prop`.
    PROPERTY_OLD = /^:([^\s=:"]+)\s*(?:\s+|$)(.*)/

    # The default options for Sass::Engine.
    # @api public
    DEFAULT_OPTIONS = {
      :style => :nested,
      :load_paths => ['.'],
      :cache => true,
      :cache_location => './.sass-cache',
      :syntax => :sass,
      :filesystem_importer => Sass::Importers::Filesystem
    }.freeze

    # Converts a Sass options hash into a standard form, filling in
    # default values and resolving aliases.
    #
    # @param options [{Symbol => Object}] The options hash;
    #   see {file:SASS_REFERENCE.md#sass_options the Sass options documentation}
    # @return [{Symbol => Object}] The normalized options hash.
    # @private
    def self.normalize_options(options)
      options = DEFAULT_OPTIONS.merge(options.reject {|k, v| v.nil?})

      # If the `:filename` option is passed in without an importer,
      # assume it's using the default filesystem importer.
      options[:importer] ||= options[:filesystem_importer].new(".") if options[:filename]

      # Tracks the original filename of the top-level Sass file
      options[:original_filename] ||= options[:filename]

      options[:cache_store] ||= Sass::CacheStores::Chain.new(
        Sass::CacheStores::Memory.new, Sass::CacheStores::Filesystem.new(options[:cache_location]))
      # Support both, because the docs said one and the other actually worked
      # for quite a long time.
      options[:line_comments] ||= options[:line_numbers]

      options[:load_paths] = options[:load_paths].map do |p|
        next p unless p.is_a?(String) || (defined?(Pathname) && p.is_a?(Pathname))
        options[:filesystem_importer].new(p.to_s)
      end

      # Backwards compatibility
      options[:property_syntax] ||= options[:attribute_syntax]
      case options[:property_syntax]
      when :alternate; options[:property_syntax] = :new
      when :normal; options[:property_syntax] = :old
      end

      options
    end

    # Returns the {Sass::Engine} for the given file.
    # This is preferable to Sass::Engine.new when reading from a file
    # because it properly sets up the Engine's metadata,
    # enables parse-tree caching,
    # and infers the syntax from the filename.
    #
    # @param filename [String] The path to the Sass or SCSS file
    # @param options [{Symbol => Object}] The options hash;
    #   See {file:SASS_REFERENCE.md#sass_options the Sass options documentation}.
    # @return [Sass::Engine] The Engine for the given Sass or SCSS file.
    # @raise [Sass::SyntaxError] if there's an error in the document.
    def self.for_file(filename, options)
      had_syntax = options[:syntax]

      if had_syntax
        # Use what was explicitly specificed
      elsif filename =~ /\.scss$/
        options.merge!(:syntax => :scss)
      elsif filename =~ /\.sass$/
        options.merge!(:syntax => :sass)
      end

      Sass::Engine.new(File.read(filename), options.merge(:filename => filename))
    end

    # The options for the Sass engine.
    # See {file:SASS_REFERENCE.md#sass_options the Sass options documentation}.
    #
    # @return [{Symbol => Object}]
    attr_reader :options

    # Creates a new Engine. Note that Engine should only be used directly
    # when compiling in-memory Sass code.
    # If you're compiling a single Sass file from the filesystem,
    # use \{Sass::Engine.for\_file}.
    # If you're compiling multiple files from the filesystem,
    # use {Sass::Plugin.
    #
    # @param template [String] The Sass template.
    #   This template can be encoded using any encoding
    #   that can be converted to Unicode.
    #   If the template contains an `@charset` declaration,
    #   that overrides the Ruby encoding
    #   (see {file:SASS_REFERENCE.md#encodings the encoding documentation})
    # @param options [{Symbol => Object}] An options hash.
    #   See {file:SASS_REFERENCE.md#sass_options the Sass options documentation}.
    # @see {Sass::Engine.for_file}
    # @see {Sass::Plugin}
    def initialize(template, options={})
      @options = self.class.normalize_options(options)
      @template = template
    end

    # Render the template to CSS.
    #
    # @return [String] The CSS
    # @raise [Sass::SyntaxError] if there's an error in the document
    # @raise [Encoding::UndefinedConversionError] if the source encoding
    #   cannot be converted to UTF-8
    # @raise [ArgumentError] if the document uses an unknown encoding with `@charset`
    def render
      return _render unless @options[:quiet]
      Sass::Util.silence_sass_warnings {_render}
    end
    alias_method :to_css, :render

    # Parses the document into its parse tree. Memoized.
    #
    # @return [Sass::Tree::Node] The root of the parse tree.
    # @raise [Sass::SyntaxError] if there's an error in the document
    def to_tree
      @tree ||= @options[:quiet] ?
        Sass::Util.silence_sass_warnings {_to_tree} :
        _to_tree
    end

    # Returns the original encoding of the document,
    # or `nil` under Ruby 1.8.
    #
    # @return [Encoding, nil]
    # @raise [Encoding::UndefinedConversionError] if the source encoding
    #   cannot be converted to UTF-8
    # @raise [ArgumentError] if the document uses an unknown encoding with `@charset`
    def source_encoding
      check_encoding!
      @original_encoding
    end

    # Gets a set of all the documents
    # that are (transitive) dependencies of this document,
    # not including the document itself.
    #
    # @return [[Sass::Engine]] The dependency documents.
    def dependencies
      _dependencies(Set.new, engines = Set.new)
      engines - [self]
    end

    # Helper for \{#dependencies}.
    #
    # @private
    def _dependencies(seen, engines)
      return if seen.include?(key = [@options[:filename], @options[:importer]])
      seen << key
      engines << self
      to_tree.grep(Tree::ImportNode) do |n|
        next if n.css_import?
        n.imported_file._dependencies(seen, engines)
      end
    end

    private

    def _render
      rendered = _to_tree.render
      return rendered if ruby1_8?
      begin
        # Try to convert the result to the original encoding,
        # but if that doesn't work fall back on UTF-8
        rendered = rendered.encode(source_encoding)
      rescue EncodingError
      end
      rendered.gsub(Regexp.new('\A@charset "(.*?)"'.encode(source_encoding)),
        "@charset \"#{source_encoding.name}\"".encode(source_encoding))
    end

    def _to_tree
      if (@options[:cache] || @options[:read_cache]) &&
          @options[:filename] && @options[:importer]
        key = sassc_key
        sha = Digest::SHA1.hexdigest(@template)

        if root = @options[:cache_store].retrieve(key, sha)
          @options = root.options.merge(@options)
          root.options = @options
          return root
        end
      end

      check_encoding!

      if @options[:syntax] == :scss
        root = Sass::SCSS::Parser.new(@template).parse
      else
        root = Tree::RootNode.new(@template)
        append_children(root, tree(tabulate(@template)).first, true)
      end

      root.options = @options
      if @options[:cache] && key && sha
        begin
          old_options = root.options
          root.options = {:importer => root.options[:importer]}
          @options[:cache_store].store(key, sha, root)
        ensure
          root.options = old_options
        end
      end
      root
    rescue SyntaxError => e
      e.modify_backtrace(:filename => @options[:filename], :line => @line)
      e.sass_template = @template
      raise e
    end

    def sassc_key
      @options[:cache_store].key(*@options[:importer].key(@options[:filename], @options))
    end

    def check_encoding!
      return if @checked_encoding
      @checked_encoding = true
      @template, @original_encoding = check_sass_encoding(@template) do |msg, line|
        raise Sass::SyntaxError.new(msg, :line => line)
      end
    end

    def tabulate(string)
      tab_str = nil
      comment_tab_str = nil
      first = true
      lines = []
      string.gsub(/\r|\n|\r\n|\r\n/, "\n").scan(/^[^\n]*?$/).each_with_index do |line, index|
        index += (@options[:line] || 1)
        if line.strip.empty?
          lines.last.text << "\n" if lines.last && lines.last.comment?
          next
        end

        line_tab_str = line[/^\s*/]
        unless line_tab_str.empty?
          if tab_str.nil?
            comment_tab_str ||= line_tab_str
            next if try_comment(line, lines.last, "", comment_tab_str, index)
            comment_tab_str = nil
          end

          tab_str ||= line_tab_str

          raise SyntaxError.new("Indenting at the beginning of the document is illegal.",
            :line => index) if first

          raise SyntaxError.new("Indentation can't use both tabs and spaces.",
            :line => index) if tab_str.include?(?\s) && tab_str.include?(?\t)
        end
        first &&= !tab_str.nil?
        if tab_str.nil?
          lines << Line.new(line.strip, 0, index, 0, @options[:filename], [])
          next
        end

        comment_tab_str ||= line_tab_str
        if try_comment(line, lines.last, tab_str * lines.last.tabs, comment_tab_str, index)
          next
        else
          comment_tab_str = nil
        end

        line_tabs = line_tab_str.scan(tab_str).size
        if tab_str * line_tabs != line_tab_str
          message = <<END.strip.gsub("\n", ' ')
Inconsistent indentation: #{Sass::Shared.human_indentation line_tab_str, true} used for indentation,
but the rest of the document was indented using #{Sass::Shared.human_indentation tab_str}.
END
          raise SyntaxError.new(message, :line => index)
        end

        lines << Line.new(line.strip, line_tabs, index, tab_str.size, @options[:filename], [])
      end
      lines
    end

    def try_comment(line, last, tab_str, comment_tab_str, index)
      return unless last && last.comment?
      # Nested comment stuff must be at least one whitespace char deeper
      # than the normal indentation
      return unless line =~ /^#{tab_str}\s/
      unless line =~ /^(?:#{comment_tab_str})(.*)$/
        raise SyntaxError.new(<<MSG.strip.gsub("\n", " "), :line => index)
Inconsistent indentation:
previous line was indented by #{Sass::Shared.human_indentation comment_tab_str},
but this line was indented by #{Sass::Shared.human_indentation line[/^\s*/]}.
MSG
      end

      last.text << "\n" << $1
      true
    end

    def tree(arr, i = 0)
      return [], i if arr[i].nil?

      base = arr[i].tabs
      nodes = []
      while (line = arr[i]) && line.tabs >= base
        if line.tabs > base
          raise SyntaxError.new("The line was indented #{line.tabs - base} levels deeper than the previous line.",
            :line => line.index) if line.tabs > base + 1

          nodes.last.children, i = tree(arr, i)
        else
          nodes << line
          i += 1
        end
      end
      return nodes, i
    end

    def build_tree(parent, line, root = false)
      @line = line.index
      node_or_nodes = parse_line(parent, line, root)

      Array(node_or_nodes).each do |node|
        # Node is a symbol if it's non-outputting, like a variable assignment
        next unless node.is_a? Tree::Node

        node.line = line.index
        node.filename = line.filename

        append_children(node, line.children, false)
      end

      node_or_nodes
    end

    def append_children(parent, children, root)
      continued_rule = nil
      continued_comment = nil
      children.each do |line|
        child = build_tree(parent, line, root)

        if child.is_a?(Tree::RuleNode)
          if child.continued? && child.children.empty?
            if continued_rule
              continued_rule.add_rules child
            else
              continued_rule = child
            end
            next
          elsif continued_rule
            continued_rule.add_rules child
            continued_rule.children = child.children
            continued_rule, child = nil, continued_rule
          end
        elsif continued_rule
          continued_rule = nil
        end

        if child.is_a?(Tree::CommentNode) && child.silent
          if continued_comment &&
              child.line == continued_comment.line +
              continued_comment.value.count("\n") + 1
            continued_comment.value << "\n" << child.value
            next
          end

          continued_comment = child
        end

        check_for_no_children(child)
        validate_and_append_child(parent, child, line, root)
      end

      parent
    end

    def validate_and_append_child(parent, child, line, root)
      case child
      when Array
        child.each {|c| validate_and_append_child(parent, c, line, root)}
      when Tree::Node
        parent << child
      end
    end

    def check_for_no_children(node)
      return unless node.is_a?(Tree::RuleNode) && node.children.empty?
      Sass::Util.sass_warn(<<WARNING.strip)
WARNING on line #{node.line}#{" of #{node.filename}" if node.filename}:
This selector doesn't have any properties and will not be rendered.
WARNING
    end

    def parse_line(parent, line, root)
      case line.text[0]
      when PROPERTY_CHAR
        if line.text[1] == PROPERTY_CHAR ||
            (@options[:property_syntax] == :new &&
             line.text =~ PROPERTY_OLD && $2.empty?)
          # Support CSS3-style pseudo-elements,
          # which begin with ::,
          # as well as pseudo-classes
          # if we're using the new property syntax
          Tree::RuleNode.new(parse_interp(line.text))
        else
          name, value = line.text.scan(PROPERTY_OLD)[0]
          raise SyntaxError.new("Invalid property: \"#{line.text}\".",
            :line => @line) if name.nil? || value.nil?
          parse_property(name, parse_interp(name), value, :old, line)
        end
      when ?$
        parse_variable(line)
      when COMMENT_CHAR
        parse_comment(line.text)
      when DIRECTIVE_CHAR
        parse_directive(parent, line, root)
      when ESCAPE_CHAR
        Tree::RuleNode.new(parse_interp(line.text[1..-1]))
      when MIXIN_DEFINITION_CHAR
        parse_mixin_definition(line)
      when MIXIN_INCLUDE_CHAR
        if line.text[1].nil? || line.text[1] == ?\s
          Tree::RuleNode.new(parse_interp(line.text))
        else
          parse_mixin_include(line, root)
        end
      else
        parse_property_or_rule(line)
      end
    end

    def parse_property_or_rule(line)
      scanner = StringScanner.new(line.text)
      hack_char = scanner.scan(/[:\*\.]|\#(?!\{)/)
      parser = Sass::SCSS::SassParser.new(scanner, @line)

      unless res = parser.parse_interp_ident
        return Tree::RuleNode.new(parse_interp(line.text))
      end
      res.unshift(hack_char) if hack_char
      if comment = scanner.scan(Sass::SCSS::RX::COMMENT)
        res << comment
      end

      name = line.text[0...scanner.pos]
      if scanner.scan(/\s*:(?:\s|$)/)
        parse_property(name, res, scanner.rest, :new, line)
      else
        res.pop if comment
        Tree::RuleNode.new(res + parse_interp(scanner.rest))
      end
    end

    def parse_property(name, parsed_name, value, prop, line)
      if value.strip.empty?
        expr = Sass::Script::String.new("")
      else
        expr = parse_script(value, :offset => line.offset + line.text.index(value))
      end
      Tree::PropNode.new(parse_interp(name), expr, prop)
    end

    def parse_variable(line)
      name, value, default = line.text.scan(Script::MATCH)[0]
      raise SyntaxError.new("Illegal nesting: Nothing may be nested beneath variable declarations.",
        :line => @line + 1) unless line.children.empty?
      raise SyntaxError.new("Invalid variable: \"#{line.text}\".",
        :line => @line) unless name && value

      expr = parse_script(value, :offset => line.offset + line.text.index(value))

      Tree::VariableNode.new(name, expr, default)
    end

    def parse_comment(line)
      if line[1] == CSS_COMMENT_CHAR || line[1] == SASS_COMMENT_CHAR
        silent = line[1] == SASS_COMMENT_CHAR
        Tree::CommentNode.new(
          format_comment_text(line[2..-1], silent),
          silent)
      else
        Tree::RuleNode.new(parse_interp(line))
      end
    end

    def parse_directive(parent, line, root)
      directive, whitespace, value = line.text[1..-1].split(/(\s+)/, 2)
      offset = directive.size + whitespace.size + 1 if whitespace

      # If value begins with url( or ",
      # it's a CSS @import rule and we don't want to touch it.
      if directive == "import"
        parse_import(line, value)
      elsif directive == "mixin"
        parse_mixin_definition(line)
      elsif directive == "include"
        parse_mixin_include(line, root)
      elsif directive == "function"
        parse_function(line, root)
      elsif directive == "for"
        parse_for(line, root, value)
      elsif directive == "each"
        parse_each(line, root, value)
      elsif directive == "else"
        parse_else(parent, line, value)
      elsif directive == "while"
        raise SyntaxError.new("Invalid while directive '@while': expected expression.") unless value
        Tree::WhileNode.new(parse_script(value, :offset => offset))
      elsif directive == "if"
        raise SyntaxError.new("Invalid if directive '@if': expected expression.") unless value
        Tree::IfNode.new(parse_script(value, :offset => offset))
      elsif directive == "debug"
        raise SyntaxError.new("Invalid debug directive '@debug': expected expression.") unless value
        raise SyntaxError.new("Illegal nesting: Nothing may be nested beneath debug directives.",
          :line => @line + 1) unless line.children.empty?
        offset = line.offset + line.text.index(value).to_i
        Tree::DebugNode.new(parse_script(value, :offset => offset))
      elsif directive == "extend"
        raise SyntaxError.new("Invalid extend directive '@extend': expected expression.") unless value
        raise SyntaxError.new("Illegal nesting: Nothing may be nested beneath extend directives.",
          :line => @line + 1) unless line.children.empty?
        offset = line.offset + line.text.index(value).to_i
        Tree::ExtendNode.new(parse_interp(value, offset))
      elsif directive == "warn"
        raise SyntaxError.new("Invalid warn directive '@warn': expected expression.") unless value
        raise SyntaxError.new("Illegal nesting: Nothing may be nested beneath warn directives.",
          :line => @line + 1) unless line.children.empty?
        offset = line.offset + line.text.index(value).to_i
        Tree::WarnNode.new(parse_script(value, :offset => offset))
      elsif directive == "return"
        raise SyntaxError.new("Invalid @return: expected expression.") unless value
        raise SyntaxError.new("Illegal nesting: Nothing may be nested beneath return directives.",
          :line => @line + 1) unless line.children.empty?
        offset = line.offset + line.text.index(value).to_i
        Tree::ReturnNode.new(parse_script(value, :offset => offset))
      elsif directive == "charset"
        name = value && value[/\A(["'])(.*)\1\Z/, 2] #"
        raise SyntaxError.new("Invalid charset directive '@charset': expected string.") unless name
        raise SyntaxError.new("Illegal nesting: Nothing may be nested beneath charset directives.",
          :line => @line + 1) unless line.children.empty?
        Tree::CharsetNode.new(name)
      elsif directive == "media"
        Tree::MediaNode.new(value)
      else
        Tree::DirectiveNode.new(line.text)
      end
    end

    def parse_for(line, root, text)
      var, from_expr, to_name, to_expr = text.scan(/^([^\s]+)\s+from\s+(.+)\s+(to|through)\s+(.+)$/).first

      if var.nil? # scan failed, try to figure out why for error message
        if text !~ /^[^\s]+/
          expected = "variable name"
        elsif text !~ /^[^\s]+\s+from\s+.+/
          expected = "'from <expr>'"
        else
          expected = "'to <expr>' or 'through <expr>'"
        end
        raise SyntaxError.new("Invalid for directive '@for #{text}': expected #{expected}.")
      end
      raise SyntaxError.new("Invalid variable \"#{var}\".") unless var =~ Script::VALIDATE

      var = var[1..-1]
      parsed_from = parse_script(from_expr, :offset => line.offset + line.text.index(from_expr))
      parsed_to = parse_script(to_expr, :offset => line.offset + line.text.index(to_expr))
      Tree::ForNode.new(var, parsed_from, parsed_to, to_name == 'to')
    end

    def parse_each(line, root, text)
      var, list_expr = text.scan(/^([^\s]+)\s+in\s+(.+)$/).first

      if var.nil? # scan failed, try to figure out why for error message
        if text !~ /^[^\s]+/
          expected = "variable name"
        elsif text !~ /^[^\s]+\s+from\s+.+/
          expected = "'in <expr>'"
        end
        raise SyntaxError.new("Invalid for directive '@each #{text}': expected #{expected}.")
      end
      raise SyntaxError.new("Invalid variable \"#{var}\".") unless var =~ Script::VALIDATE

      var = var[1..-1]
      parsed_list = parse_script(list_expr, :offset => line.offset + line.text.index(list_expr))
      Tree::EachNode.new(var, parsed_list)
    end

    def parse_else(parent, line, text)
      previous = parent.children.last
      raise SyntaxError.new("@else must come after @if.") unless previous.is_a?(Tree::IfNode)

      if text
        if text !~ /^if\s+(.+)/
          raise SyntaxError.new("Invalid else directive '@else #{text}': expected 'if <expr>'.")
        end
        expr = parse_script($1, :offset => line.offset + line.text.index($1))
      end

      node = Tree::IfNode.new(expr)
      append_children(node, line.children, false)
      previous.add_else node
      nil
    end

    def parse_import(line, value)
      raise SyntaxError.new("Illegal nesting: Nothing may be nested beneath import directives.",
        :line => @line + 1) unless line.children.empty?

      scanner = StringScanner.new(value)
      values = []

      loop do
        unless node = parse_import_arg(scanner)
          raise SyntaxError.new("Invalid @import: expected file to import, was #{scanner.rest.inspect}",
            :line => @line)
        end
        values << node
        break unless scanner.scan(/,\s*/)
      end

      return values
    end

    def parse_import_arg(scanner)
      return if scanner.eos?
      unless (str = scanner.scan(Sass::SCSS::RX::STRING)) ||
          (uri = scanner.scan(Sass::SCSS::RX::URI))
        return Tree::ImportNode.new(scanner.scan(/[^,]+/))
      end

      val = scanner[1] || scanner[2]
      scanner.scan(/\s*/)
      if media = scanner.scan(/[^,].*/)
        Tree::DirectiveNode.new("@import #{str || uri} #{media}")
      elsif uri
        Tree::DirectiveNode.new("@import #{uri}")
      elsif val =~ /^http:\/\//
        Tree::DirectiveNode.new("@import url(#{val})")
      else
        Tree::ImportNode.new(val)
      end
    end

    MIXIN_DEF_RE = /^(?:=|@mixin)\s*(#{Sass::SCSS::RX::IDENT})(.*)$/
    def parse_mixin_definition(line)
      name, arg_string = line.text.scan(MIXIN_DEF_RE).first
      raise SyntaxError.new("Invalid mixin \"#{line.text[1..-1]}\".") if name.nil?

      offset = line.offset + line.text.size - arg_string.size
      args = Script::Parser.new(arg_string.strip, @line, offset, @options).
        parse_mixin_definition_arglist
      Tree::MixinDefNode.new(name, args)
    end

    MIXIN_INCLUDE_RE = /^(?:\+|@include)\s*(#{Sass::SCSS::RX::IDENT})(.*)$/
    def parse_mixin_include(line, root)
      name, arg_string = line.text.scan(MIXIN_INCLUDE_RE).first
      raise SyntaxError.new("Invalid mixin include \"#{line.text}\".") if name.nil?

      offset = line.offset + line.text.size - arg_string.size
      args, keywords = Script::Parser.new(arg_string.strip, @line, offset, @options).
        parse_mixin_include_arglist
      raise SyntaxError.new("Illegal nesting: Nothing may be nested beneath mixin directives.",
        :line => @line + 1) unless line.children.empty?
      Tree::MixinNode.new(name, args, keywords)
    end

    FUNCTION_RE = /^@function\s*(#{Sass::SCSS::RX::IDENT})(.*)$/
    def parse_function(line, root)
      name, arg_string = line.text.scan(FUNCTION_RE).first
      raise SyntaxError.new("Invalid function definition \"#{line.text}\".") if name.nil?

      offset = line.offset + line.text.size - arg_string.size
      args = Script::Parser.new(arg_string.strip, @line, offset, @options).
        parse_function_definition_arglist
      Tree::FunctionNode.new(name, args)
    end

    def parse_script(script, options = {})
      line = options[:line] || @line
      offset = options[:offset] || 0
      Script.parse(script, line, offset, @options)
    end

    def format_comment_text(text, silent)
      content = text.split("\n")

      if content.first && content.first.strip.empty?
        removed_first = true
        content.shift
      end

      return silent ? "//" : "/* */" if content.empty?
      content.last.gsub!(%r{ ?\*/ *$}, '')
      content.map! {|l| l.gsub!(/^\*( ?)/, '\1') || (l.empty? ? "" : " ") + l}
      content.first.gsub!(/^ /, '') unless removed_first
      if silent
        "//" + content.join("\n//")
      else
        # The #gsub fixes the case of a trailing */
        "/*" + content.join("\n *").gsub(/ \*\Z/, '') + " */"
      end
    end

    def parse_interp(text, offset = 0)
      self.class.parse_interp(text, @line, offset, :filename => @filename)
    end

    # It's important that this have strings (at least)
    # at the beginning, the end, and between each Script::Node.
    #
    # @private
    def self.parse_interp(text, line, offset, options)
      res = []
      rest = Sass::Shared.handle_interpolation text do |scan|
        escapes = scan[2].size
        res << scan.matched[0...-2 - escapes]
        if escapes % 2 == 1
          res << "\\" * (escapes - 1) << '#{'
        else
          res << "\\" * [0, escapes - 1].max
          res << Script::Parser.new(
            scan, line, offset + scan.pos - scan.matched_size, options).
            parse_interpolated
        end
      end
      res << rest
    end
  end
end
require 'fileutils'

require 'fileutils'

# XXX CE: is this still necessary now that we have the compiler class?
module Sass
  # A lightweight infrastructure for defining and running callbacks.
  # Callbacks are defined using \{#define\_callback\} at the class level,
  # and called using `run_#{name}` at the instance level.
  #
  # Clients can add callbacks by calling the generated `on_#{name}` method,
  # and passing in a block that's run when the callback is activated.
  #
  # @example Define a callback
  #   class Munger
  #     extend Sass::Callbacks
  #     define_callback :string_munged
  #
  #     def munge(str)
  #       res = str.gsub(/[a-z]/, '\1\1')
  #       run_string_munged str, res
  #       res
  #     end
  #   end
  #
  # @example Use a callback
  #   m = Munger.new
  #   m.on_string_munged {|str, res| puts "#{str} was munged into #{res}!"}
  #   m.munge "bar" #=> bar was munged into bbaarr!
  module Callbacks
    # Automatically includes {InstanceMethods}
    # when something extends this module.
    #
    # @param base [Module]
    def self.extended(base)
      base.send(:include, InstanceMethods)
    end
    protected

    module InstanceMethods
      # Removes all callbacks registered against this object.
      def clear_callbacks!
        @_sass_callbacks = {}
      end
    end

    # Define a callback with the given name.
    # This will define an `on_#{name}` method
    # that registers a block,
    # and a `run_#{name}` method that runs that block
    # (optionall with some arguments).
    #
    # @param name [Symbol] The name of the callback
    # @return [void]
    def define_callback(name)
      class_eval <<RUBY
def on_#{name}(&block)
  @_sass_callbacks ||= {}
  (@_sass_callbacks[#{name.inspect}] ||= []) << block
end

def run_#{name}(*args)
  return unless @_sass_callbacks
  return unless @_sass_callbacks[#{name.inspect}]
  @_sass_callbacks[#{name.inspect}].each {|c| c[*args]}
end
private :run_#{name}
RUBY
    end
  end
end
# We keep configuration in its own self-contained file
# so that we can load it independently in Rails 3,
# where the full plugin stuff is lazy-loaded.

module Sass
  module Plugin
    module Configuration

      # Returns the default options for a {Sass::Plugin::Compiler}.
      #
      # @return [{Symbol => Object}]
      def default_options
        @default_options ||= {
          :css_location       => './public/stylesheets',
          :always_update      => false,
          :always_check       => true,
          :full_exception     => true,
          :cache_location     => ".sass-cache"
        }.freeze
      end

      # Resets the options and {Sass::Callbacks::InstanceMethods#clear_callbacks! clears all callbacks}.
      def reset!
        @options = nil
        clear_callbacks!
      end

      # An options hash.
      # See {file:SASS_REFERENCE.md#sass_options the Sass options documentation}.
      #
      # @return [{Symbol => Object}]
      def options
        @options ||= default_options.dup
        @options[:cache_store] ||= Sass::CacheStores::Filesystem.new(@options[:cache_location])
        @options
      end

      # Sets the options hash.
      # See {file:SASS_REFERENCE.md#sass_options the Sass options documentation}.
      # See {Sass::Plugin::Configuration#reset!}
      # @deprecated Instead, modify the options hash in-place.
      # @param value [{Symbol => Object}] The options hash
      def options=(value)
        Sass::Util.sass_warn("Setting Sass::Plugin.options is deprecated " +
                             "and will be removed in a future release.")
        options.merge!(value)
      end

      # Adds a new template-location/css-location mapping.
      # This means that Sass/SCSS files in `template_location`
      # will be compiled to CSS files in `css_location`.
      #
      # This is preferred over manually manipulating the {file:SASS_REFERENCE.md#template_location-option `:template_location` option}
      # since the option can be in multiple formats.
      #
      # Note that this method will change `options[:template_location]`
      # to be in the Array format.
      # This means that even if `options[:template_location]`
      # had previously been a Hash or a String,
      # it will now be an Array.
      #
      # @param template_location [String] The location where Sass/SCSS files will be.
      # @param css_location [String] The location where compiled CSS files will go.
      def add_template_location(template_location, css_location = options[:css_location])
        normalize_template_location!
        template_location_array << [template_location, css_location]
      end

      # Removes a template-location/css-location mapping.
      # This means that Sass/SCSS files in `template_location`
      # will no longer be compiled to CSS files in `css_location`.
      #
      # This is preferred over manually manipulating the {file:SASS_REFERENCE.md#template_location-option `:template_location` option}
      # since the option can be in multiple formats.
      #
      # Note that this method will change `options[:template_location]`
      # to be in the Array format.
      # This means that even if `options[:template_location]`
      # had previously been a Hash or a String,
      # it will now be an Array.
      #
      # @param template_location [String]
      #   The location where Sass/SCSS files were,
      #   which is now going to be ignored.
      # @param css_location [String]
      #   The location where compiled CSS files went, but will no longer go.
      # @return [Boolean]
      #   Non-`nil` if the given mapping already existed and was removed,
      #   or `nil` if nothing was changed.
      def remove_template_location(template_location, css_location = options[:css_location])
        normalize_template_location!
        template_location_array.delete([template_location, css_location])
      end

      # Returns the template locations configured for Sass
      # as an array of `[template_location, css_location]` pairs.
      # See the {file:SASS_REFERENCE.md#template_location-option `:template_location` option}
      # for details.
      #
      # @return [Array<(String, String)>]
      #   An array of `[template_location, css_location]` pairs.
      def template_location_array
        old_template_location = options[:template_location]
        normalize_template_location!
        options[:template_location]
      ensure
        options[:template_location] = old_template_location
      end

      private

      def normalize_template_location!
        return if options[:template_location].is_a?(Array)
        options[:template_location] =
          case options[:template_location]
          when nil
            options[:css_location] ?
              [[File.join(options[:css_location], 'sass'), options[:css_location]]] : []
          when String; [[options[:template_location], options[:css_location]]]
          else; options[:template_location].to_a
          end
      end
    end
  end
end
module Sass
  module Plugin
    # The class handles `.s[ca]ss` file staleness checks via their mtime timestamps.
    #
    # To speed things up two level of caches are employed:
    #
    # * A class-level dependency cache which stores @import paths for each file.
    #   This is a long-lived cache that is reused by every StalenessChecker instance.
    # * Three short-lived instance-level caches, one for file mtimes,
    #   one for whether a file is stale during this particular run.
    #   and one for the parse tree for a file.
    #   These are only used by a single StalenessChecker instance.
    #
    # Usage:
    #
    # * For a one-off staleness check of a single `.s[ca]ss` file,
    #   the class-level {stylesheet_needs_update?} method
    #   should be used.
    # * For a series of staleness checks (e.g. checking all files for staleness)
    #   a StalenessChecker instance should be created,
    #   and the instance-level \{#stylesheet\_needs\_update?} method should be used.
    #   the caches should make the whole process significantly faster.
    #   *WARNING*: It is important not to retain the instance for too long,
    #   as its instance-level caches are never explicitly expired.
    class StalenessChecker
      @dependencies_cache = {}

      class << self
        # TODO: attach this to a compiler instance.
        # @private
        attr_accessor :dependencies_cache
      end

      # Creates a new StalenessChecker
      # for checking the staleness of several stylesheets at once.
      #
      # @param options [{Symbol => Object}]
      #   See {file:SASS_REFERENCE.md#sass_options the Sass options documentation}.
      def initialize(options)
        @dependencies = self.class.dependencies_cache

        # Entries in the following instance-level caches are never explicitly expired.
        # Instead they are supposed to automaticaly go out of scope when a series of staleness checks
        # (this instance of StalenessChecker was created for) is finished.
        @mtimes, @dependencies_stale, @parse_trees = {}, {}, {}
        @options = Sass::Engine.normalize_options(options)
      end

      # Returns whether or not a given CSS file is out of date
      # and needs to be regenerated.
      #
      # @param css_file [String] The location of the CSS file to check.
      # @param template_file [String] The location of the Sass or SCSS template
      #   that is compiled to `css_file`.
      # @return [Boolean] Whether the stylesheet needs to be updated.
      def stylesheet_needs_update?(css_file, template_file, importer = nil)
        template_file = File.expand_path(template_file)
        begin
          css_mtime = File.mtime(css_file)
        rescue Errno::ENOENT
          return true
        end
        stylesheet_modified_since?(template_file, css_mtime, importer)
      end

      # Returns whether a Sass or SCSS stylesheet has been modified since a given time.
      #
      # @param template_file [String] The location of the Sass or SCSS template.
      # @param mtime [Fixnum] The modification time to check against.
      # @param importer [Sass::Importers::Base] The importer used to locate the stylesheet.
      #   Defaults to the filesystem importer.
      # @return [Boolean] Whether the stylesheet has been modified.
      def stylesheet_modified_since?(template_file, mtime, importer = nil)
        importer ||= @options[:filesystem_importer].new(".")
        dependency_updated?(mtime).call(template_file, importer)
      end

      # Returns whether or not a given CSS file is out of date
      # and needs to be regenerated.
      #
      # The distinction between this method and the instance-level \{#stylesheet\_needs\_update?}
      # is that the instance method preserves mtime and stale-dependency caches,
      # so it's better to use when checking multiple stylesheets at once.
      #
      # @param css_file [String] The location of the CSS file to check.
      # @param template_file [String] The location of the Sass or SCSS template
      #   that is compiled to `css_file`.
      # @return [Boolean] Whether the stylesheet needs to be updated.
      def self.stylesheet_needs_update?(css_file, template_file, importer = nil)
        new(Plugin.engine_options).stylesheet_needs_update?(css_file, template_file, importer)
      end

      # Returns whether a Sass or SCSS stylesheet has been modified since a given time.
      #
      # The distinction between this method and the instance-level \{#stylesheet\_modified\_since?}
      # is that the instance method preserves mtime and stale-dependency caches,
      # so it's better to use when checking multiple stylesheets at once.
      #
      # @param template_file [String] The location of the Sass or SCSS template.
      # @param mtime [Fixnum] The modification time to check against.
      # @param importer [Sass::Importers::Base] The importer used to locate the stylesheet.
      #   Defaults to the filesystem importer.
      # @return [Boolean] Whether the stylesheet has been modified.
      def self.stylesheet_modified_since?(template_file, mtime, importer = nil)
        new(Plugin.engine_options).stylesheet_modified_since?(template_file, mtime, importer)
      end

      private

      def dependencies_stale?(uri, importer, css_mtime)
        timestamps = @dependencies_stale[[uri, importer]] ||= {}
        timestamps.each_pair do |checked_css_mtime, is_stale|
          if checked_css_mtime <= css_mtime && !is_stale
            return false
          elsif checked_css_mtime > css_mtime && is_stale
            return true
          end
        end
        timestamps[css_mtime] = dependencies(uri, importer).any?(&dependency_updated?(css_mtime))
      rescue Sass::SyntaxError
        # If there's an error finding dependencies, default to recompiling.
        true
      end

      def mtime(uri, importer)
        @mtimes[[uri, importer]] ||=
          begin
            mtime = importer.mtime(uri, @options)
            if mtime.nil?
              @dependencies.delete([uri, importer])
              nil
            else
              mtime
            end
          end
      end

      def dependencies(uri, importer)
        stored_mtime, dependencies = @dependencies[[uri, importer]]

        if !stored_mtime || stored_mtime < mtime(uri, importer)
          dependencies = compute_dependencies(uri, importer)
          @dependencies[[uri, importer]] = [mtime(uri, importer), dependencies]
        end

        dependencies
      end

      def dependency_updated?(css_mtime)
        Proc.new do |uri, importer|
          sass_mtime = mtime(uri, importer)
          !sass_mtime ||
            sass_mtime > css_mtime ||
            dependencies_stale?(uri, importer, css_mtime)
        end
      end

      def compute_dependencies(uri, importer)
        tree(uri, importer).grep(Tree::ImportNode) do |n|
          next if n.css_import?
          file = n.imported_file
          key = [file.options[:filename], file.options[:importer]]
          @parse_trees[key] = file.to_tree
          key
        end.compact
      end

      def tree(uri, importer)
        @parse_trees[[uri, importer]] ||= importer.find(uri, @options).to_tree
      end
    end
  end
end

module Sass::Plugin

  # The Compiler class handles compilation of multiple files and/or directories,
  # including checking which CSS files are out-of-date and need to be updated
  # and calling Sass to perform the compilation on those files.
  #
  # {Sass::Plugin} uses this class to update stylesheets for a single application.
  # Unlike {Sass::Plugin}, though, the Compiler class has no global state,
  # and so multiple instances may be created and used independently.
  #
  # If you need to compile a Sass string into CSS,
  # please see the {Sass::Engine} class.
  #
  # Unlike {Sass::Plugin}, this class doesn't keep track of
  # whether or how many times a stylesheet should be updated.
  # Therefore, the following `Sass::Plugin` options are ignored by the Compiler:
  #
  # * `:never_update`
  # * `:always_check`
  class Compiler
    include Sass::Util
    include Configuration
    extend Sass::Callbacks

    # Creates a new compiler.
    #
    # @param options [{Symbol => Object}]
    #   See {file:SASS_REFERENCE.md#sass_options the Sass options documentation}.
    def initialize(options = {})
      self.options.merge!(options)
    end

    # Register a callback to be run before stylesheets are mass-updated.
    # This is run whenever \{#update\_stylesheets} is called,
    # unless the \{file:SASS_REFERENCE.md#never_update-option `:never_update` option}
    # is enabled.
    #
    # @yield [individual_files]
    # @yieldparam individual_files [<(String, String)>]
    #   Individual files to be updated, in addition to the directories
    #   specified in the options.
    #   The first element of each pair is the source file,
    #   the second is the target CSS file.
    define_callback :updating_stylesheets

    # Register a callback to be run before a single stylesheet is updated.
    # The callback is only run if the stylesheet is guaranteed to be updated;
    # if the CSS file is fresh, this won't be run.
    #
    # Even if the \{file:SASS_REFERENCE.md#full_exception-option `:full_exception` option}
    # is enabled, this callback won't be run
    # when an exception CSS file is being written.
    # To run an action for those files, use \{#on\_compilation\_error}.
    #
    # @yield [template, css]
    # @yieldparam template [String]
    #   The location of the Sass/SCSS file being updated.
    # @yieldparam css [String]
    #   The location of the CSS file being generated.
    define_callback :updating_stylesheet

    # Register a callback to be run when Sass decides not to update a stylesheet.
    # In particular, the callback is run when Sass finds that
    # the template file and none of its dependencies
    # have been modified since the last compilation.
    #
    # Note that this is **not** run when the
    # \{file:SASS_REFERENCE.md#never-update_option `:never_update` option} is set,
    # nor when Sass decides not to compile a partial.
    #
    # @yield [template, css]
    # @yieldparam template [String]
    #   The location of the Sass/SCSS file not being updated.
    # @yieldparam css [String]
    #   The location of the CSS file not being generated.
    define_callback :not_updating_stylesheet

    # Register a callback to be run when there's an error
    # compiling a Sass file.
    # This could include not only errors in the Sass document,
    # but also errors accessing the file at all.
    #
    # @yield [error, template, css]
    # @yieldparam error [Exception] The exception that was raised.
    # @yieldparam template [String]
    #   The location of the Sass/SCSS file being updated.
    # @yieldparam css [String]
    #   The location of the CSS file being generated.
    define_callback :compilation_error

    # Register a callback to be run when Sass creates a directory
    # into which to put CSS files.
    #
    # Note that even if multiple levels of directories need to be created,
    # the callback may only be run once.
    # For example, if "foo/" exists and "foo/bar/baz/" needs to be created,
    # this may only be run for "foo/bar/baz/".
    # This is not a guarantee, however;
    # it may also be run for "foo/bar/".
    #
    # @yield [dirname]
    # @yieldparam dirname [String]
    #   The location of the directory that was created.
    define_callback :creating_directory

    # Register a callback to be run when Sass detects
    # that a template has been modified.
    # This is only run when using \{#watch}.
    #
    # @yield [template]
    # @yieldparam template [String]
    #   The location of the template that was modified.
    define_callback :template_modified

    # Register a callback to be run when Sass detects
    # that a new template has been created.
    # This is only run when using \{#watch}.
    #
    # @yield [template]
    # @yieldparam template [String]
    #   The location of the template that was created.
    define_callback :template_created

    # Register a callback to be run when Sass detects
    # that a template has been deleted.
    # This is only run when using \{#watch}.
    #
    # @yield [template]
    # @yieldparam template [String]
    #   The location of the template that was deleted.
    define_callback :template_deleted

    # Register a callback to be run when Sass deletes a CSS file.
    # This happens when the corresponding Sass/SCSS file has been deleted.
    #
    # @yield [filename]
    # @yieldparam filename [String]
    #   The location of the CSS file that was deleted.
    define_callback :deleting_css

    # Updates out-of-date stylesheets.
    #
    # Checks each Sass/SCSS file in {file:SASS_REFERENCE.md#template_location-option `:template_location`}
    # to see if it's been modified more recently than the corresponding CSS file
    # in {file:SASS_REFERENCE.md#css_location-option `:css_location`}.
    # If it has, it updates the CSS file.
    #
    # @param individual_files [Array<(String, String)>]
    #   A list of files to check for updates
    #   **in addition to those specified by the
    #   {file:SASS_REFERENCE.md#template_location-option `:template_location` option}.**
    #   The first string in each pair is the location of the Sass/SCSS file,
    #   the second is the location of the CSS file that it should be compiled to.
    def update_stylesheets(individual_files = [])
      run_updating_stylesheets individual_files
      Sass::Plugin.checked_for_updates = true
      staleness_checker = StalenessChecker.new(engine_options)

      individual_files.each do |t, c|
        if options[:always_update] || staleness_checker.stylesheet_needs_update?(c, t)
          update_stylesheet(t, c)
        end
      end

      template_location_array.each do |template_location, css_location|

        Dir.glob(File.join(template_location, "**", "[^_]*.s[ca]ss")).sort.each do |file|
          # Get the relative path to the file
          name = file.sub(template_location.to_s.sub(/\/*$/, '/'), "")
          css = css_filename(name, css_location)

          if options[:always_update] || staleness_checker.stylesheet_needs_update?(css, file)
            update_stylesheet file, css
          else
            run_not_updating_stylesheet file, css
          end
        end
      end
    end

    # Watches the template directory (or directories)
    # and updates the CSS files whenever the related Sass/SCSS files change.
    # `watch` never returns.
    #
    # Whenever a change is detected to a Sass/SCSS file in
    # {file:SASS_REFERENCE.md#template_location-option `:template_location`},
    # the corresponding CSS file in {file:SASS_REFERENCE.md#css_location-option `:css_location`}
    # will be recompiled.
    # The CSS files of any Sass/SCSS files that import the changed file will also be recompiled.
    #
    # Before the watching starts in earnest, `watch` calls \{#update\_stylesheets}.
    #
    # Note that `watch` uses the [FSSM](http://github.com/ttilley/fssm) library
    # to monitor the filesystem for changes.
    # FSSM isn't loaded until `watch` is run.
    # The version of FSSM distributed with Sass is loaded by default,
    # but if another version has already been loaded that will be used instead.
    #
    # @param individual_files [Array<(String, String)>]
    #   A list of files to watch for updates
    #   **in addition to those specified by the
    #   {file:SASS_REFERENCE.md#template_location-option `:template_location` option}.**
    #   The first string in each pair is the location of the Sass/SCSS file,
    #   the second is the location of the CSS file that it should be compiled to.
    def watch(individual_files = [])
      update_stylesheets(individual_files)

      begin
        require 'fssm'
      rescue LoadError => e
        dir = Sass::Util.scope("vendor/fssm/lib")
        if $LOAD_PATH.include?(dir)
          e.message << "\n" <<
            if File.exists?(scope(".git"))
              'Run "git submodule update --init" to get the recommended version.'
            else
              'Run "gem install fssm" to get it.'
            end
          raise e
        else
          $LOAD_PATH.unshift dir
          retry
        end
      end

      unless individual_files.empty? && FSSM::Backends::Default.name == "FSSM::Backends::FSEvents"
        # As of FSSM 0.1.4, it doesn't support FSevents on individual files,
        # but it also isn't smart enough to switch to polling itself.
        require 'fssm/backends/polling'
        Sass::Util.silence_warnings do
          FSSM::Backends.const_set(:Default, FSSM::Backends::Polling)
        end
      end

      # TODO: Keep better track of what depends on what
      # so we don't have to run a global update every time anything changes.
      FSSM.monitor do |mon|
        template_location_array.each do |template_location, css_location|
          mon.path template_location do |path|
            path.glob '**/*.s[ac]ss'

            path.update do |base, relative|
              run_template_modified File.join(base, relative)
              update_stylesheets(individual_files)
            end

            path.create do |base, relative|
              run_template_created File.join(base, relative)
              update_stylesheets(individual_files)
            end

            path.delete do |base, relative|
              run_template_deleted File.join(base, relative)
              css = File.join(css_location, relative.gsub(/\.s[ac]ss$/, '.css'))
              try_delete_css css
              update_stylesheets(individual_files)
            end
          end
        end

        individual_files.each do |template, css|
          mon.file template do |path|
            path.update do
              run_template_modified template
              update_stylesheets(individual_files)
            end

            path.create do
              run_template_created template
              update_stylesheets(individual_files)
            end

            path.delete do
              run_template_deleted template
              try_delete_css css
              update_stylesheets(individual_files)
            end
          end
        end
      end
    end

    # Non-destructively modifies \{#options} so that default values are properly set,
    # and returns the result.
    #
    # @param additional_options [{Symbol => Object}] An options hash with which to merge \{#options}
    # @return [{Symbol => Object}] The modified options hash
    def engine_options(additional_options = {})
      opts = options.merge(additional_options)
      opts[:load_paths] = load_paths(opts)
      opts
    end

    # Compass expects this to exist
    def stylesheet_needs_update?(css_file, template_file)
      StalenessChecker.stylesheet_needs_update?(css_file, template_file)
    end

    private

    def update_stylesheet(filename, css)
      dir = File.dirname(css)
      unless File.exists?(dir)
        run_creating_directory dir
        FileUtils.mkdir_p dir
      end

      begin
        File.read(filename) unless File.readable?(filename) # triggers an error for handling
        engine_opts = engine_options(:css_filename => css, :filename => filename)
        result = Sass::Engine.for_file(filename, engine_opts).render
      rescue Exception => e
        run_compilation_error e, filename, css
        result = Sass::SyntaxError.exception_to_css(e, options)
      else
        run_updating_stylesheet filename, css
      end

      # Finally, write the file
      flag = 'w'
      flag = 'wb' if Sass::Util.windows? && options[:unix_newlines]
      File.open(css, flag) do |file|
        file.set_encoding(result.encoding) unless Sass::Util.ruby1_8?
        file.print(result)
      end
    end

    def try_delete_css(css)
      return unless File.exists?(css)
      run_deleting_css css
      File.delete css
    end

    def load_paths(opts = options)
      (opts[:load_paths] || []) + template_locations
    end

    def template_locations
      template_location_array.to_a.map {|l| l.first}
    end

    def css_locations
      template_location_array.to_a.map {|l| l.last}
    end

    def css_filename(name, path)
      "#{path}/#{name}".gsub(/\.s[ac]ss$/, '.css')
    end
  end
end

module Sass
  # This module provides a single interface to the compilation of Sass/SCSS files
  # for an application. It provides global options and checks whether CSS files
  # need to be updated.
  #
  # This module is used as the primary interface with Sass
  # when it's used as a plugin for various frameworks.
  # All Rack-enabled frameworks are supported out of the box.
  # The plugin is {file:SASS_REFERENCE.md#rails_merb_plugin automatically activated for Rails and Merb}.
  # Other frameworks must enable it explicitly; see {Sass::Plugin::Rack}.
  #
  # This module has a large set of callbacks available
  # to allow users to run code (such as logging) when certain things happen.
  # All callback methods are of the form `on_#{name}`,
  # and they all take a block that's called when the given action occurs.
  #
  # Note that this class proxies almost all methods to its {Sass::Plugin::Compiler} instance.
  # See \{#compiler}.
  #
  # @example Using a callback
  #   Sass::Plugin.on_updating_stylesheet do |template, css|
  #     puts "Compiling #{template} to #{css}"
  #   end
  #   Sass::Plugin.update_stylesheets
  #     #=> Compiling app/sass/screen.scss to public/stylesheets/screen.css
  #     #=> Compiling app/sass/print.scss to public/stylesheets/print.css
  #     #=> Compiling app/sass/ie.scss to public/stylesheets/ie.css
  # @see Sass::Plugin::Compiler
  module Plugin
    include Sass::Util
    extend self

    @checked_for_updates = false

    # Whether or not Sass has **ever** checked if the stylesheets need to be updated
    # (in this Ruby instance).
    #
    # @return [Boolean]
    attr_accessor :checked_for_updates

    # Same as \{#update\_stylesheets}, but respects \{#checked\_for\_updates}
    # and the {file:SASS_REFERENCE.md#always_update-option `:always_update`}
    # and {file:SASS_REFERENCE.md#always_check-option `:always_check`} options.
    #
    # @see #update_stylesheets
    def check_for_updates
      return unless !Sass::Plugin.checked_for_updates ||
          Sass::Plugin.options[:always_update] || Sass::Plugin.options[:always_check]
      update_stylesheets
    end

    # Returns the singleton compiler instance.
    # This compiler has been pre-configured according
    # to the plugin configuration.
    #
    # @return [Sass::Plugin::Compiler]
    def compiler
      @compiler ||= Compiler.new
    end

    # Updates out-of-date stylesheets.
    #
    # Checks each Sass/SCSS file in {file:SASS_REFERENCE.md#template_location-option `:template_location`}
    # to see if it's been modified more recently than the corresponding CSS file
    # in {file:SASS_REFERENCE.md#css_location-option `:css_location`}.
    # If it has, it updates the CSS file.
    #
    # @param individual_files [Array<(String, String)>]
    #   A list of files to check for updates
    #   **in addition to those specified by the
    #   {file:SASS_REFERENCE.md#template_location-option `:template_location` option}.**
    #   The first string in each pair is the location of the Sass/SCSS file,
    #   the second is the location of the CSS file that it should be compiled to.
    def update_stylesheets(individual_files = [])
      return if options[:never_update]
      compiler.update_stylesheets(individual_files)
    end

    # Updates all stylesheets, even those that aren't out-of-date.
    # Ignores the cache.
    #
    # @param individual_files [Array<(String, String)>]
    #   A list of files to check for updates
    #   **in addition to those specified by the
    #   {file:SASS_REFERENCE.md#template_location-option `:template_location` option}.**
    #   The first string in each pair is the location of the Sass/SCSS file,
    #   the second is the location of the CSS file that it should be compiled to.
    # @see #update_stylesheets
    def force_update_stylesheets(individual_files = [])
      old_options = options
      self.options = options.dup
      options[:never_update] = false
      options[:always_update] = true
      options[:cache] = false
      update_stylesheets(individual_files)
    ensure
      self.options = old_options
    end

    # All other method invocations are proxied to the \{#compiler}.
    #
    # @see #compiler
    # @see Sass::Plugin::Compiler
    def method_missing(method, *args, &block)
      if compiler.respond_to?(method)
        compiler.send(method, *args, &block)
      else
        super
      end
    end

    # For parity with method_missing
    def respond_to?(method)
      super || compiler.respond_to?(method)
    end

    # There's a small speedup by not using method missing for frequently delegated methods.
    def options
      compiler.options
    end

  end
end

if defined?(ActionController)
unless defined?(Sass::RAILS_LOADED)
  Sass::RAILS_LOADED = true

  module Sass::Plugin::Configuration
    # Different default options in a rails envirionment.
    def default_options
      return @default_options if @default_options
      opts = {
        :quiet             => Sass::Util.rails_env != "production",
        :full_exception    => Sass::Util.rails_env != "production",
        :cache_location    => Sass::Util.rails_root + '/tmp/sass-cache'
      }

      opts.merge!(
        :always_update     => false,
        :template_location => Sass::Util.rails_root + '/public/stylesheets/sass',
        :css_location      => Sass::Util.rails_root + '/public/stylesheets',
        :always_check      => Sass::Util.rails_env == "development")

      @default_options = opts.freeze
    end
  end

  Sass::Plugin.options.reverse_merge!(Sass::Plugin.default_options)

  # Rails 3.1 loads and handles Sass all on its own
  if defined?(ActionController::Metal)
    # 3.1 > Rails >= 3.0
module Sass
  module Plugin
    # Rack middleware for compiling Sass code.
    #
    # ## Activate
    #
    #     use Sass::Plugin::Rack
    #
    # ## Customize
    #
    #     Sass::Plugin.options.merge(
    #       :cache_location => './tmp/sass-cache',
    #       :never_update => environment != :production,
    #       :full_exception => environment != :production)
    #
    # {file:SASS_REFERENCE.md#options See the Reference for more options}.
    #
    # ## Use
    #
    # Put your Sass files in `public/stylesheets/sass`.
    # Your CSS will be generated in `public/stylesheets`,
    # and regenerated every request if necessary.
    # The locations and frequency {file:SASS_REFERENCE.md#options can be customized}.
    # That's all there is to it!
    class Rack
      # The delay, in seconds, between update checks.
      # Useful when many resources are requested for a single page.
      # `nil` means no delay at all.
      #
      # @return [Float]
      attr_accessor :dwell

      # Initialize the middleware.
      #
      # @param app [#call] The Rack application
      # @param dwell [Float] See \{#dwell}
      def initialize(app, dwell = 1.0)
        @app = app
        @dwell = dwell
        @check_after = Time.now.to_f
      end

      # Process a request, checking the Sass stylesheets for changes
      # and updating them if necessary.
      #
      # @param env The Rack request environment
      # @return [(#to_i, {String => String}, Object)] The Rack response
      def call(env)
        if @dwell.nil? || Time.now.to_f > @check_after
          Sass::Plugin.check_for_updates
          @check_after = Time.now.to_f + @dwell if @dwell
        end
        @app.call(env)
      end
    end
  end
end

    Rails.configuration.middleware.use(Sass::Plugin::Rack)
  elsif defined?(ActionController::Dispatcher) &&
      defined?(ActionController::Dispatcher.middleware)
    # Rails >= 2.3
    ActionController::Dispatcher.middleware.use(Sass::Plugin::Rack)
  else
    module ActionController
      class Base
        alias_method :sass_old_process, :process
        def process(*args)
          Sass::Plugin.check_for_updates
          sass_old_process(*args)
        end
      end
    end
  end
end
elsif defined?(Merb::Plugins)
unless defined?(Sass::MERB_LOADED)
  Sass::MERB_LOADED = true

  module Sass::Plugin::Configuration
    # Different default options in a m envirionment.
    def default_options
      @default_options ||= begin
        version = Merb::VERSION.split('.').map { |n| n.to_i }
        if version[0] <= 0 && version[1] < 5
          root = MERB_ROOT
          env  = MERB_ENV
        else
          root = Merb.root.to_s
          env  = Merb.environment
        end

        {
          :always_update      => false,
          :template_location => root + '/public/stylesheets/sass',
          :css_location      => root + '/public/stylesheets',
          :cache_location    => root + '/tmp/sass-cache',
          :always_check      => env != "production",
          :quiet             => env != "production",
          :full_exception    => env != "production"
        }.freeze
      end
    end
  end

  config = Merb::Plugins.config[:sass] || Merb::Plugins.config["sass"] || {}

  if defined? config.symbolize_keys!
    config.symbolize_keys!
  end

  Sass::Plugin.options.merge!(config)

  class Sass::Plugin::MerbBootLoader < Merb::BootLoader
    after Merb::BootLoader::RackUpApplication

    def self.run
      # Apparently there's no better way than this to add Sass
      # to Merb's Rack stack.
      Merb::Config[:app] = Sass::Plugin::Rack.new(Merb::Config[:app])
    end
  end
end
else
# The reason some options are declared here rather than in sass/plugin/configuration.rb
# is that otherwise they'd clobber the Rails-specific options.
# Since Rails' options are lazy-loaded in Rails 3,
# they're reverse-merged with the default options
# so that user configuration is preserved.
# This means that defaults that differ from Rails'
# must be declared here.

unless defined?(Sass::GENERIC_LOADED)
  Sass::GENERIC_LOADED = true

  Sass::Plugin.options.merge!(:css_location   => './public/stylesheets',
                              :always_update  => false,
                              :always_check   => true)
end
end
# Rails 3.0.0.beta.2+, < 3.1
if defined?(ActiveSupport) && Sass::Util.has?(:public_method, ActiveSupport, :on_load) &&
    !Sass::Util.ap_geq?('3.1.0.beta')
  ActiveSupport.on_load(:before_configuration) do
    require 'sass'
  end
end