module Ym4r

  module GmPlugin

    #The module where all the Ruby-to-JavaScript conversion takes place. It is included by all the classes in the YM4R library.

    module MappingObject

      #The name of the variable in JavaScript space.

      attr_reader :variable

      

      #Creates javascript code for missing methods + takes care of listeners

      def method_missing(name,*args)

        str_name = name.to_s

        if str_name =~ /^on_(.*)/

          if args.length != 1

            raise ArgumentError("Only 1 argument is allowed on on_ methods");

          else

            Variable.new("GEvent.addListener(#{to_javascript},\"#{MappingObject.javascriptify_method($1)}\",#{args[0]})")

          end

        else

          args.collect! do |arg|

            MappingObject.javascriptify_variable(arg)

          end

          Variable.new("#{to_javascript}.#{MappingObject.javascriptify_method(str_name)}(#{args.join(",")})")

        end

      end

            

      #Creates javascript code for array or hash indexing

      def [](index) #index could be an integer or string

        return Variable.new("#{to_javascript}[#{MappingObject.javascriptify_variable(index)}]")

      end



      #Transforms a Ruby object into a JavaScript string : MAppingObject, String, Array, Hash and general case (using to_s)

      def self.javascriptify_variable(arg)

        if arg.is_a?(MappingObject)

          arg.to_javascript

        elsif arg.is_a?(String)

          "\"#{MappingObject.escape_javascript(arg)}\""

        elsif arg.is_a?(Array)

          "[" + arg.collect{ |a| MappingObject.javascriptify_variable(a)}.join(",") + "]"

        elsif arg.is_a?(Hash)

          "{" + arg.to_a.collect do |v|

            "#{MappingObject.javascriptify_method(v[0].to_s)} : #{MappingObject.javascriptify_variable(v[1])}"

          end.join(",") + "}"

        elsif arg.nil?

          "undefined"

        else

          arg.to_s

        end

      end

      

      #Escape string to be used in JavaScript. Lifted from rails.

      def self.escape_javascript(javascript)

        javascript.gsub(/\r\n|\n|\r/, "\\n").gsub("\"") { |m| "\\#{m}" }

      end

      

      #Transform a ruby-type method name (like add_overlay) to a JavaScript-style one (like addOverlay).

      def self.javascriptify_method(method_name)

        method_name.gsub(/_(\w)/){|s| $1.upcase}

      end

      

      #Declares a Mapping Object bound to a JavaScript variable of name +variable+.

      def declare(variable)

        @variable = variable

        "var #{@variable} = #{create};"

      end



      #declare with a random variable name

      def declare_random(init,size = 8)

        s = init.clone

        6.times { s << (i = Kernel.rand(62); i += ((i < 10) ? 48 : ((i < 36) ? 55 : 61 ))).chr }

        declare(s)

      end



      #Checks if the MappinObject has been declared

      def declared?

        !@variable.nil?

      end

      

      #Binds a Mapping object to a previously declared JavaScript variable of name +variable+.

      def assign_to(variable)

        @variable = variable

        "#{@variable} = #{create};"

      end



      #Assign the +value+ to the +property+ of the MappingObject

      def set_property(property, value)

        "#{to_javascript}.#{MappingObject.javascriptify_method(property.to_s)} = #{MappingObject.javascriptify_variable(value)}"

      end



      #Returns the code to get a +property+ from the MappingObject

      def get_property(property)

        Variable.new("#{to_javascript}.#{MappingObject.javascriptify_method(property.to_s)}")

      end

      

      #Returns a Javascript code representing the object

      def to_javascript

        unless @variable.nil?

          @variable

        else

          create

        end

      end

      

      #Creates a Mapping Object in JavaScript.

      #To be implemented by subclasses if needed

      def create

      end

    end



    #Used to bind a ruby variable to an already existing JavaScript one. It doesn't have to be a variable in the sense "var variable" but it can be any valid JavaScript expression that has a value.

    class Variable

      include MappingObject

      

      def initialize(variable)

        @variable = variable

      end

      #Returns the javascript expression contained in the object.

      def create

        @variable

      end

      #Returns the expression inside the Variable followed by a ";"

      def to_s

        @variable + ";"

      end



      UNDEFINED = Variable.new("undefined")

    end

  end

end