module Vedeu

  module Cursors

    # Handle the refreshing (redrawing) of a cursor, without redrawing
    # the whole interface; unless the cursor's offset has caused the
    # view to change.
    #
    class Refresh

      extend Forwardable

      def_delegators :border,
                     :height,
                     :width

      # @param (see #initialize)
      def self.by_name(name = nil)
        new(name).by_name
      end

      # Returns a new instance of Vedeu::Cursors::Refresh.
      #
      # @param name [String] The name of the cursor.
      # @return [Vedeu::Cursors::Refresh]
      def initialize(name = nil)
        @name = name || Vedeu.focus
      end

      # Renders the cursor in the terminal. If the cursor's x or y
      # offsets are greater or equal to the interface's width or
      # height respectively, then the view is also refreshed, causing
      # the content to be offset also.
      #
      # @return [Array]
      def by_name
        Vedeu.log(type: :info, message: "Refreshing cursor: '#{name}'")

        Vedeu.trigger(:_refresh_view_, name) if refresh_view?

        cursor.render
      end

      protected

      # @!attribute [r] name
      # @return [String]
      attr_reader :name

      private

      # Returns true when the view should be refreshed. This is
      # determined by checking that the offsets for x and y are
      # outside the width and height of the named interface.
      #
      # @return [Boolean]
      def refresh_view?
        cursor.ox >= width || cursor.oy >= height
      end

      # @return [Vedeu::Cursors::Cursor]
      # @see Vedeu::Cursors::Repository#by_name
      def cursor
        @cursor ||= Vedeu.cursors.by_name(name)
      end

      # Fetch the border by name.
      #
      # @note
      #   {Vedeu::Borders::Border} is used in this way because when
      #   there is not a border defined, it will fallback to a
      #   {Vedeu::Borders::Null} which uses
      #   {Vedeu::Geometry::Geometry} to determine it's dimensions
      #   based on the name also. When a {Vedeu::Geometry::Geometry}
      #   cannot be found, this falls back to a
      #   {Vedeu::Geometry::Null} which uses the dimensions of the
      #   current terminal.
      #
      # @return (see Vedeu::Borders::Repository#by_name)
      def border
        @border ||= Vedeu.borders.by_name(name)
      end

    end # Refresh

  end # Cursors

end # Vedeu