require 'yaml'

module LanguageSniffer
  # Language names that are recognizable by GitHub. Defined languages
  # can be highlighted, searched and listed under the Top Languages page.
  #
  # Languages are defined in `lib/language_sniffer/languages.yml`.
  class Language
    @languages       = []
    @overrides       = {}
    @index           = {}
    @name_index      = {}
    @alias_index     = {}
    @extension_index = {}
    @filename_index  = {}

    # Valid Languages types
    TYPES = [:data, :markup, :programming]

    # Internal: Test if extension maps to multiple Languages.
    #
    # Returns true or false.
    def self.ambiguous?(extension)
      @overrides.include?(extension)
    end

    # Include?: Return overridden extensions.
    #
    # Returns extensions Array.
    def self.overridden_extensions
      @overrides.keys
    end

    # Internal: Create a new Language object
    #
    # attributes - A hash of attributes
    #
    # Returns a Language object
    def self.create(attributes = {})
      language = new(attributes)

      @languages << language

      # All Language names should be unique. Warn if there is a duplicate.
      if @name_index.key?(language.name)
        warn "Duplicate language name: #{language.name}"
      end

      # Language name index
      @index[language.name] = @name_index[language.name] = language

      language.aliases.each do |name|
        # All Language aliases should be unique. Warn if there is a duplicate.
        if @alias_index.key?(name)
          warn "Duplicate alias: #{name}"
        end

        @index[name] = @alias_index[name] = language
      end

      language.extensions.each do |extension|
        if extension !~ /^\./
          warn "Extension is missing a '.': #{extension.inspect}"
        end

        unless ambiguous?(extension)
          # Index the extension with a leading ".": ".rb"
          @extension_index[extension] = language

          # Index the extension without a leading ".": "rb"
          @extension_index[extension.sub(/^\./, '')] = language
        end
      end

      language.overrides.each do |extension|
        if extension !~ /^\./
          warn "Extension is missing a '.': #{extension.inspect}"
        end

        @overrides[extension] = language
      end

      language.filenames.each do |filename|
        @filename_index[filename] = language
      end

      language
    end

    # Public: Get all Languages
    #
    # Returns an Array of Languages
    def self.all
      @languages
    end

    # Public: Look up Language by its proper name.
    #
    # name - The String name of the Language
    #
    # Examples
    #
    #   Language.find_by_name('Ruby')
    #   # => #<Language name="Ruby">
    #
    # Returns the Language or nil if none was found.
    def self.find_by_name(name)
      @name_index[name]
    end

    # Public: Look up Language by one of its aliases.
    #
    # name - A String alias of the Language
    #
    # Examples
    #
    #   Language.find_by_alias('cpp')
    #   # => #<Language name="C++">
    #
    # Returns the Language or nil if none was found.
    def self.find_by_alias(name)
      @alias_index[name]
    end

    # Public: Look up Language by extension.
    #
    # extension - The extension String. May include leading "."
    #
    # Examples
    #
    #   Language.find_by_extension('.rb')
    #   # => #<Language name="Ruby">
    #
    # Returns the Language or nil if none was found.
    def self.find_by_extension(extension)
      @extension_index[extension]
    end

    # Public: Look up Language by filename.
    #
    # filename - The path String.
    #
    # Examples
    #
    #   Language.find_by_filename('foo.rb')
    #   # => #<Language name="Ruby">
    #
    # Returns the Language or nil if none was found.
    def self.find_by_filename(filename)
      basename, extname = File.basename(filename), File.extname(filename)
      @filename_index[basename] || @extension_index[extname]
    end

    # Public: Look up Language by its name.
    #
    # name - The String name of the Language
    #
    # Examples
    #
    #   Language['Ruby']
    #   # => #<Language name="Ruby">
    #
    #   Language['ruby']
    #   # => #<Language name="Ruby">
    #
    # Returns the Language or nil if none was found.
    def self.[](name)
      @index[name]
    end

    # Internal: Initialize a new Language
    #
    # attributes - A hash of attributes
    def initialize(attributes = {})
      # @name is required
      @name = attributes[:name] || raise(ArgumentError, "missing name")

      # Set type
      @type = attributes[:type] ? attributes[:type].to_sym : nil

      # Set aliases
      @aliases = [default_alias_name] + (attributes[:aliases] || [])

      # Set pygments lexer
      @lexer = attributes[:lexer] || name

      # Set legacy search term
      @search_term = attributes[:search_term] || default_alias_name

      # Set extensions or default to [].
      @extensions = attributes[:extensions] || []
      @overrides  = attributes[:overrides]  || []
      @filenames  = attributes[:filenames]  || []

      @primary_extension = attributes[:primary_extension] || default_primary_extension || extensions.first

      # Prepend primary extension unless its already included
      if primary_extension && !extensions.include?(primary_extension)
        @extensions = [primary_extension] + extensions
      end

      # If group name is set, save the name so we can lazy load it later
      if attributes[:group_name]
        @group = nil
        @group_name = attributes[:group_name]

      # Otherwise we can set it to self now
      else
        @group = self
      end
    end

    # Public: Get proper name
    #
    # Examples
    #
    #   # => "Ruby"
    #   # => "Python"
    #   # => "Perl"
    #
    # Returns the name String
    attr_reader :name

    # Public: Get type.
    #
    # Returns a type Symbol or nil.
    attr_reader :type

    # Public: Get pygments lexer name.
    #
    # Returns a lexer name or nil.
    attr_reader :lexer

    # Public: Get aliases
    #
    # Examples
    #
    #   Language['C++'].aliases
    #   # => ["cpp"]
    #
    # Returns an Array of String names
    attr_reader :aliases

    # Deprecated: Get code search term
    #
    # Examples
    #
    #   # => "ruby"
    #   # => "python"
    #   # => "perl"
    #
    # Returns the name String
    attr_reader :search_term

    # Public: Get extensions
    #
    # Examples
    #
    #   # => ['.rb', '.rake', ...]
    #
    # Returns the extensions Array
    attr_reader :extensions

    # Deprecated: Get primary extension
    #
    # Defaults to the first extension but can be overriden
    # in the languages.yml.
    #
    # The primary extension can not be nil. Tests should verify this.
    #
    # This attribute is only used by app/helpers/gists_helper.rb for
    # creating the language dropdown. It really should be using `name`
    # instead. Would like to drop primary extension.
    #
    # Returns the extension String.
    attr_reader :primary_extension

    # Internal: Get overridden extensions.
    #
    # Returns the extensions Array.
    attr_reader :overrides

    # Public: Get filenames
    #
    # Examples
    #
    #   # => ['Rakefile', ...]
    #
    # Returns the extensions Array
    attr_reader :filenames

    # Internal: Get default alias name
    #
    # Returns the alias name String
    def default_alias_name
      name.downcase.gsub(/\s/, '-')
    end

    # Internal: Get default primary extension.
    #
    # Returns the extension String.
    def default_primary_extension
      extensions.first
    end

    # Public: Get Language group
    #
    # Returns a Language
    def group
      @group ||= Language.find_by_name(@group_name)
    end

    # Public: Return name as String representation
    def to_s
      name
    end

    def ==(other)
      eql?(other)
    end

    def eql?(other)
      equal?(other)
    end

    def hash
      name.hash
    end
  end

  YAML.load_file(File.expand_path("../languages.yml", __FILE__)).each do |name, options|
    Language.create(
      :name              => name,
      :type              => options['type'],
      :aliases           => options['aliases'],
      :lexer             => options['lexer'],
      :group_name        => options['group'],
      :search_term       => options['search_term'],
      :extensions        => options['extensions'],
      :primary_extension => options['primary_extension'],
      :overrides         => options['overrides'],
      :filenames         => options['filenames']
    )
  end
end