module ActiveRecord
  class Base
  	module ThreadIdentityMap
	  class ClassIdMap
		def initialize(klass)
		  @objects = {}
		  @object = klass.allocate
		  @object.instance_variable_set(:@attributes, {:id=>nil})
		  @object.instance_variable_set(:@attributes_cache, {})
		end
		
		def [](id)
		  @object.id = id
		  @objects[@object.id]
		end
		
		def []=(id, v)
		  @object.id = id
		  @objects[@object.id] = v
		end
		
		def delete(id)
		  @object.id = id
		  @objects.delete(id)
		end
	  end
	  
	  class IdMap
	  
		def initialize
		  @objects = {}
		end
	  
		def for_class(klass)
		  @objects[ klass.base_class ] ||= ClassIdMap.new(klass)
		end
		
	  end
	  
	  module ClassMethods
	  	def create_identity_map
	  	  set_thread_id_map IdMap.new
	  	end
	  	
	  	def drop_identity_map
	  	  set_thread_id_map nil
	  	end
	  	
		def with_id_map( fresh = true)
		  old = thread_id_map
		  create_identity_map if fresh || old.nil?
		  yield
		ensure
		  set_thread_id_map old
		end
		
		def without_id_map
		  old = thread_id_map
		  drop_identity_map
		  yield
		ensure
		  set_thread_id_map old
		end
		
#		def uncached_with_identity_map( &block )
#		  without_id_map do
#		  	uncached_without_identity_map &block
#		  end
#		end
		
		protected
		
		  def thread_id_map
			Thread.current[:ar_identity_map]
		  end
		  
		  def thread_id_map=(v)
			Thread.current[:ar_identity_map] = v
		  end
		  
		  alias set_thread_id_map thread_id_map=
		
	  end
    end
	
	extend ThreadIdentityMap::ClassMethods
#	self.class.send :alias_method_chain, :uncached, :identity_map
  end
end