module DataMapper
  module Resource
    class PersistenceState
      # a persisted/dirty resource
      class Dirty < Persisted
        def set(subject, value)
          track(subject, value)
          super
          original_attributes.empty? ? Clean.new(resource) : self
        end

        def delete
          reset_resource
          Deleted.new(resource)
        end

        def commit
          remove_from_identity_map
          set_child_keys
          assert_valid_attributes
          update_resource
          reset_original_attributes
          reset_resource_key
          Clean.new(resource)
        ensure
          add_to_identity_map
        end

        def rollback
          reset_resource
          Clean.new(resource)
        end

        def original_attributes
          @original_attributes ||= {}
        end

        private def track(subject, value)
          if original_attributes.key?(subject)
            # stop tracking if the new value is the same as the original
            original_attributes.delete(subject) if original_attributes[subject].eql?(value)
          elsif !value.eql?((original = get(subject)))
            # track the original value
            original_attributes[subject] = original
          end
        end

        private def update_resource
          repository.update(resource.dirty_attributes, collection_for_self)
        end

        private def reset_resource
          reset_resource_properties
          reset_resource_relationships
        end

        private def reset_resource_key
          resource.instance_eval { remove_instance_variable(:@_key) }
        end

        private def reset_resource_properties
          # delete every original attribute after resetting the resource
          original_attributes.delete_if do |property, value|
            property.set!(resource, value)
            true
          end
        end

        private def reset_resource_relationships
          relationships.each do |relationship|
            next unless relationship.loaded?(resource)

            # TODO: consider a method in Relationship that can reset the relationship
            resource.instance_eval { remove_instance_variable(relationship.instance_variable_name) }
          end
        end

        private def reset_original_attributes
          original_attributes.clear
        end

        private def assert_valid_attributes
          properties.each do |property|
            value = property.get! resource
            property.assert_valid_value(value)
          end
        end
      end
    end
  end
end