module Vedeu

  module Buffers

    # Store and retrieve {Vedeu::Buffers::VirtualBuffer} objects.
    #
    # Each {Vedeu::Buffers::VirtualBuffer} object is a copy of the
    # current terminal including content but not as String objects but
    # {Vedeu::Views::Char} objects. Using {Vedeu::Views::Char} objects
    # means that we can store the data used to make up the displayed
    # character, complete with its colour, position and style.
    #
    # Once a {Vedeu::Views::Char} has been converted to a String, it
    # is tricky to separate the escape sequences and string data. By
    # deferring this conversion we can display the
    # {Vedeu::Views::Char} in multiple ways (e.g. HTML) or in multiple
    # formats (e.g. JSON), and render/use that in an appropriate way.
    #
    module VirtualBuffers

      extend self

      # Fetch the oldest stored virtual buffer first.
      #
      # @return [Array<Array<Vedeu::Views::Char>>|NilClass]
      def retrieve
        Vedeu.log(type: :drb, message: 'Retrieving output')

        storage.pop
      end

      # Store a new virtual buffer.
      #
      # @return [Array<Array<Vedeu::Views::Char>>]
      def store(data)
        Vedeu.log(type: :drb, message: 'Storing output')

        storage.unshift(data)
      end

      # Return the number of virtual buffers currently stored.
      #
      # @return [Fixnum]
      def size
        storage.size
      end

      # Destroy all virtual buffers currently stored.
      #
      # @return [Array]
      def clear
        @storage = in_memory
      end
      alias_method :reset, :clear

      private

      # Access to the storage for this repository.
      #
      # @return [Array]
      def storage
        @storage ||= in_memory
      end

      # Returns an empty collection ready for the storing of virtual
      # buffers.
      #
      # @return [Array]
      def in_memory
        []
      end

    end # VirtualBuffers

  end # Buffers

end # Vedeu