take-five/acts_as_ordered_tree

# coding: utf-8

module ActsAsOrderedTree
  module Relation
    # AR::Relation extension which adds ability to explicitly set records
    #
    # @example
    #   records = MyModel.where(:parent_id => nil).to_a
    #   relation = MyModel.where(:parent_id => nil).
    #      extending(ActsAsOrderedTree::Relation::Preloaded).
    #      records(records)
    #   relation.to_a.should be records
    module Preloaded
      def records(records)
        @loaded = false
        @records = records

        build_where!

        @loaded = true

        self
      end

      # Reverse the existing order of records on the relation.
      def reverse_order
        (respond_to?(:spawn) ? spawn : clone).records(@records.reverse)
      end

      def reverse_order!
        @records = @records.reverse

        self
      end

      # Extending relation is not really intrusive operation, so we can save preloaded records
      def extending(*)
        super.tap { |relation| relation.records(@records) if loaded? }
      end

      private
      def record_ids
        @records.map { |r| r.id if r }.compact
      end

      def build_where!
        self.where_values = build_where(:id => record_ids)
      end
    end # module Preloaded
  end # module Relation
end # module ActsAsOrderedTree