module MyFeeds
  module Identify
    extend ActiveSupport::Concern

    included do
      before_save :save_feed_identify
      class_attribute :feed_polymorphic_name
      self.feed_polymorphic_name = self == Feed ? :source : default_feed_polymorphic_name
      delegate :default_feed_polymorphic_name, :polymorphic_identify_column, :polymorphic_id_column, :polymorphic_type_column, to: :"self.class"
    end

    protected
    def save_feed_identify
      instance_eval %Q{self.#{polymorphic_identify_column} = "#\{#{polymorphic_id_column}.to_s\}@#\{#{polymorphic_type_column}.to_s.underscore\}"}
    end

    private
    module ClassMethods
      def default_feed_polymorphic_name
        self.to_s.underscore
      end

      def polymorphic_identify_column
        :"#{feed_polymorphic_name}_identify"
      end

      def polymorphic_id_column
        :"#{feed_polymorphic_name}_id"
      end

      def polymorphic_type_column
        :"#{feed_polymorphic_name}_type"
      end
    end
  end
end