# A message is what is sent when you invoke a method. Args and stuff are packed up in to a Message
# and the Message is sent to the receiver.

# Part of the housekeeping (see attributes) makes messages a double linked list (next_message and
#  caller) , and maybe surprisingly this means that we can create all messages at runtime
# and link them up and never have to touch that list again.
# All the args and receiver data changes, but the list of messages stays constant.

module Parfait
  class Message < Object
    def initialize next_m
      @next_message = next_m
      @frame = Frame.new()
      @caller = nil
      super()
    end

    attr_reader :next_message , :frame , :caller # aka prev_message
    attr_reader :receiver ,  :return_address , :return_value , :method

    def set_caller caller
      @caller = caller
    end

    def get_type_for(name)
      index = @layout.get_index(name)
      get_at(index)
    end

    def __send
      typ = get_type_for( :receiver )
      # TODO: this will obviously be recoded as case, once that is done :-)
      # depending on value type get method
      if( typ == Integer )
        method = Integer.get_method @method_name
      else
        if( typ != ObjectReference )
          raise "unimplemented case"
        else
          method = @receiver.get_singeton_method @method_name
          # Find the method for the given object (receiver) according to ruby dispatch rules:
            # - see if the receiver object has a (singleton) method by the name
            # - get receivers class and look for instance methods of the name
            # - go up inheritance tree
            # - start over with method_missing instead
            #    -> guaranteed to end at object.method_missing
          unless method
            cl = @receiver.layout.object_class
            method = cl.get_instance_or_super_method @method_name
          end
        end
      end
      unless method
        message = Message.new( @receiver , :method_missing , [@method_name] + @args)
        message.send
      else
        method.call
      end
    end
  end
end