module Uuids
  module Base

    # Defines custom methods to be defined by `has_uuids` method.
    module HasUuids
      extend ActiveSupport::Concern

      # Model scopes.
      module ClassMethods

        # Selects distinct records by uuids (relation scope).
        #
        # @example
        #
        #     class MyRecord < ActiveRecord::Base
        #       include Uuids::Base
        #       has_uuids
        #     end
        #
        #     MyRecord.by_uuid(
        #       "23423fe3-28d8-a1e5-bde3-2e08074aa92d",
        #       "9223238d-a7e3-2d36-a93d-1e50fea02de2"
        #     )
        #     # => #<ActiveRecord::Relation ...>
        #
        # Params:
        # <tt>*values</tt>:: a list of uuids to select records by.
        #
        # Returns the <tt>ActiveRecord::Relation</tt> object.
        #
        def by_uuid(*values)
          first_value = values.first
          list = first_value.is_a?(Array) ? first_value : values
          joins(:uuids).where(uuids_uuids: { value: list }).uniq
        end
      end

      # Returns the first UUID (sorted as a string) for the record.
      #
      # @example
      #     record.uuids.new value: "23423fe3-28d8-a1e5-bde3-2e08074aa92d"
      #     record.uuids.new value: "9223238d-a7e3-2d36-a93d-1e50fea02de2"
      #     record.uuid # => "23423fe3-28d8-a1e5-bde3-2e08074aa92d"
      #
      def uuid
        uuids.map(&:value).sort.first
      end

      # Assigns a new uuid to the record.
      #
      # @example
      #     record.uuid = "23423fe3-28d8-a1e5-bde3-2e08074aa92d"
      #     record.uuid # => "23423fe3-28d8-a1e5-bde3-2e08074aa92d"
      #
      # Params:
      # <tt>value</tt>:: a string value of uuid to assign.
      #
      def uuid=(value)
        uuids.new value: value
      end

      # Assigns a list of new uuids to the record.
      #
      # @example
      #     record.uuids = [
      #       "23423fe3-28d8-a1e5-bde3-2e08074aa92d",
      #       "9223238d-a7e3-2d36-a93d-1e50fea02de2"
      #     ]
      #     record.uuids.map(&:value)
      #     # => [
      #       "23423fe3-28d8-a1e5-bde3-2e08074aa92d",
      #       "9223238d-a7e3-2d36-a93d-1e50fea02de2"
      #     ]
      #
      # Params:
      # <tt>values</tt>:: an array of uuids string values to assign.
      #
      def uuids=(*values)
        first = values.first
        list  = first.is_a?(Array) ? first : values
        list.each { |value| self.uuid = value }
      end

      private

      # Creates the uuids by default preventing a record from being ureferrable.
      def add_default_uuid
        uuids.present? || uuids.new
      end

      # Prevents destruction of a record before its uuids reassigned to
      # other records.
      def prevent_destruction
        return true if uuids.blank?
        errors.add :base, :uuids_present
        false
      end
    end
  end
end