module ActiveRecord
  # = Active Record Has Many Association
  module Associations
    # This is the proxy that handles a has many association.
    #
    # If the association has a <tt>:through</tt> option further specialization
    # is provided by its child HasManyThroughAssociation.
    class HasManyAssociation < CollectionAssociation #:nodoc:
      include ForeignAssociation

      def handle_dependency
        case options[:dependent]
        when :restrict_with_exception
          raise ActiveRecord::DeleteRestrictionError.new(reflection.name) unless empty?

        when :restrict_with_error
          unless empty?
            record = owner.class.human_attribute_name(reflection.name).downcase
            owner.errors.add(:base, :'restrict_dependent_destroy.has_many', record: record)
            throw(:abort)
          end

        when :destroy
          # No point in executing the counter update since we're going to destroy the parent anyway
          load_target.each { |t| t.destroyed_by_association = reflection }
          destroy_all
        else
          delete_all
        end
      end

      def insert_record(record, validate = true, raise = false)
        set_owner_attributes(record)
        super
      end

      def empty?
        if reflection.has_cached_counter?
          size.zero?
        else
          super
        end
      end

      private

        # Returns the number of records in this collection.
        #
        # If the association has a counter cache it gets that value. Otherwise
        # it will attempt to do a count via SQL, bounded to <tt>:limit</tt> if
        # there's one. Some configuration options like :group make it impossible
        # to do an SQL count, in those cases the array count will be used.
        #
        # That does not depend on whether the collection has already been loaded
        # or not. The +size+ method is the one that takes the loaded flag into
        # account and delegates to +count_records+ if needed.
        #
        # If the collection is empty the target is set to an empty array and
        # the loaded flag is set to true as well.
        def count_records
          count = if reflection.has_cached_counter?
            owner._read_attribute(reflection.counter_cache_column).to_i
          else
            scope.count(:all)
          end

          # If there's nothing in the database and @target has no new records
          # we are certain the current target is an empty array. This is a
          # documented side-effect of the method that may avoid an extra SELECT.
          (@target ||= []) && loaded! if count == 0

          [association_scope.limit_value, count].compact.min
        end

        def update_counter(difference, reflection = reflection())
          if reflection.has_cached_counter?
            owner.increment!(reflection.counter_cache_column, difference)
          end
        end

        def update_counter_in_memory(difference, reflection = reflection())
          if reflection.counter_must_be_updated_by_has_many?
            counter = reflection.counter_cache_column
            owner.increment(counter, difference)
            owner.send(:clear_attribute_change, counter) # eww
          end
        end

        def delete_count(method, scope)
          if method == :delete_all
            scope.delete_all
          else
            scope.update_all(reflection.foreign_key => nil)
          end
        end

        def delete_or_nullify_all_records(method)
          count = delete_count(method, scope)
          update_counter(-count)
        end

        # Deletes the records according to the <tt>:dependent</tt> option.
        def delete_records(records, method)
          if method == :destroy
            records.each(&:destroy!)
            update_counter(-records.length) unless reflection.inverse_updates_counter_cache?
          else
            scope = self.scope.where(reflection.klass.primary_key => records)
            update_counter(-delete_count(method, scope))
          end
        end

        def concat_records(records, *)
          update_counter_if_success(super, records.length)
        end

        def _create_record(attributes, *)
          if attributes.is_a?(Array)
            super
          else
            update_counter_if_success(super, 1)
          end
        end

        def update_counter_if_success(saved_successfully, difference)
          if saved_successfully
            update_counter_in_memory(difference)
          end
          saved_successfully
        end
    end
  end
end