# various classes would derive from array in ruby, ie have indexed variables
#
# But for our memory layout we need the variable part of an object to be after
# the fixed, ie the instance variables
#
# Just using ruby derivation will not allow us to offset the index, so instead the
# function will be generated and included to the classes that need them.
#
# Using ruby include does not work for similar reasons, so Indexed.at is the main
# function that generates the methods

module Indexed

  def self.at( offset , clazz )

    clazz.send :define_method , :get_length do
      internal_object_length - 1
    end

    # index of item, remeber first item has index 1
    # return  nil if no such item
    clazz.send :define_method , :index_of do |item|
      max = self.get_length
      counter = 1
      while( counter <= max )
        if( get(counter) == item)
          return counter
        end
        counter = counter + 1
      end
      return nil
    end

    # include? means non nil index
    clazz.send :define_method , :include? do |item|
      return index_of(item) != nil
    end

    # push means add to the end
    # this automatically grows the List
    clazz.send :define_method , :push do |value|
      set( self.get_length + 1 , value)
    end

    clazz.send :define_method , :delete do |value|
      index = index_of value
      return false unless index
      delete_at index
    end

    clazz.send :define_method , :delete_at do |index|
      # TODO bounds check
      while(index < self.get_length)
        set( index , get(index + 1))
        index = index + 1
      end
      set_length( self.get_length - 1)
      true
    end


    clazz.send :define_method , :first do
      return nil if empty?
      get(1)
    end

    clazz.send :define_method , :last do
      return nil if empty?
      get(get_length())
    end

    # set the value at index.
    # Lists start from index 1
    clazz.send :define_method , :set do | index , value|
      raise "Only positive indexes #{index}" if index <= 0
      if index > self.get_length
        grow_to(index)
      end
      # internally 1 is reserved for the layout
      internal_object_set( index + 1, value)
    end

    # set the value at index.
    # Lists start from index 1
    clazz.send :define_method , :get do | index|
      raise "Only positive indexes, #{index}" if index <= 0
      if index > self.get_length
        return nil
      else
        return internal_object_get(index + 1)
      end
    end

    clazz.send :define_method , :empty? do
      self.get_length == 0
    end

    clazz.send :define_method , :set_length do | len|
      was = self.get_length
      return if was == len
      if(was < len)
        grow_to len
      else
        shrink_to len
      end
    end

    clazz.send :define_method , :grow_to do | len|
      raise "Only positive lenths, #{len}" if len < 0
      old_length = self.get_length
      return if old_length >= len
      internal_object_grow(len + 1)
    end

    clazz.send :define_method , :shrink_to do | len|
      raise "Only positive lenths, #{len}" if len < 0
      old_length = self.get_length
      return if old_length <= len
      internal_object_shrink(len + 1)
    end

    clazz.send :define_method , :equal? do | other|
      # this should call parfait get_class, alas that is not implemented yet
      return false if other.class != self.class
      return false if other.get_length != self.get_length
      index = self.get_length
      while(index > 0)
        return false if other.get(index) != self.get(index)
        index = index - 1
      end
      return true
    end

    # above, correct, implementation causes problems in the machine object space
    # because when a second empty (newly created) list is added, it is not actually
    # added as it exists already. TODO, but hack with below identity function
    clazz.send :define_method , :== do | other|
      self.object_id == other.object_id
    end

    # word length (padded) is the amount of space taken by the object
    # For your basic object this means the number of instance variables as determined by layout
    # This is off course 0 for a list, unless someone squeezed an instance variable in
    # but additionally, the amount of data comes on top.
    # unfortuntely we can't just use super because of the Padding
    clazz.send :define_method , :word_length do
      padded_words( get_layout().get_length() +  get_length() )
    end

    clazz.send :define_method , :inspect do
      inspect_from 1
    end

    clazz.send :define_method , :inspect_from do |index|
      ret = ""
      while index <= self.get_length
        item = get(index)
        ret += item.inspect
        ret += "," unless index == self.get_length
        index = index + 1
      end
      ret
    end

  end
end