module Backend

  module File

    # Index files dumped in the JSON format.
    #
    class JSON < Basic

      # Uses the extension "json".
      #
      def extension
        :json
      end
      # Loads the index hash from json format.
      #
      def load
        Yajl::Parser.parse ::File.open(cache_path, 'r'), symbolize_keys: true
      end
      # Dumps the index hash in json format.
      #
      def dump hash
        hash.dump_json cache_path
      end
      # A json file does not provide retrieve functionality.
      #
      def retrieve
        raise "Can't retrieve from JSON file. Use text file."
      end

    end

  end

end