module Picky

  module Backends

    class Memory

      # Memory-based index files dumped in the JSON format.
      #
      class JSON < Basic

        # Uses the extension "json".
        #
        def extension
          :json
        end

        # The initial content before loading.
        #
        def default
          {}
        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

end