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 = Vedeu.focus)
        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)
        @name = name
      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_, name) if refresh_view?

        Vedeu::Terminal.output(cursor.to_s)
      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