module Vedeu

  # Provides escape sequence strings.
  #
  module EscapeSequences

    # Provides colour related escape sequences.
    #
    module Colours

      extend self

      # Produces the background named colour escape sequence hash from the
      # foreground escape sequence hash.
      #
      # @return [Hash<Symbol => Fixnum>]
      def background_codes
        hash = {}
        foreground_codes.inject(hash) do |h, (k, v)|
          h.merge!(k => v + 10)
        end
      end

      # Produces the foreground named colour escape sequence hash. The
      # background escape sequences are also generated from this by adding 10 to
      # the values.
      # This hash gives rise to methods you can call directly on `Esc` to
      # produce the desired colours:
      #
      # @example
      #   Esc.red                     # => "\e[31m"
      #
      #   Esc.red { 'some text' }     # => "\e[31msome text\e[39m"
      #
      #   Esc.on_blue                 # => "\e[44m"
      #
      #   Esc.on_blue { 'some text' } # => "\e[44msome text\e[49m"
      #
      #   # Valid names:
      #   :black, :red, :green, :yellow, :blue, :magenta, :cyan, :light_grey,
      #   :default, :dark_grey, :light_red, :light_green, :light_yellow,
      #   :light_blue, :light_magenta, :light_cyan, :white
      #
      # @return [Hash<Symbol => Fixnum>]
      def foreground_codes
        {
          black:         30,
          red:           31,
          green:         32,
          yellow:        33,
          blue:          34,
          magenta:       35,
          cyan:          36,
          light_grey:    37,
          default:       39,
          dark_grey:     90,
          light_red:     91,
          light_green:   92,
          light_yellow:  93,
          light_blue:    94,
          light_magenta: 95,
          light_cyan:    96,
          white:         97,
        }
      end
      alias_method :codes, :foreground_codes

      # @return [void]
      def setup!
        define_backgrounds!
        define_foregrounds!
      end

      private

      # @return [void]
      def define_backgrounds!
        background_codes.each do |key, code|
          define_method('on_' + key.to_s) do |&blk|
            "\e[#{code}m" + (blk ? blk.call + "\e[49m" : '')
          end
        end
      end

      # Dynamically creates methods for each terminal named colour. When a block
      # is given, then the colour is reset to 'default' once the block is
      # called.
      #
      # @return [void]
      def define_foregrounds!
        foreground_codes.each do |key, code|
          define_method(key) do |&blk|
            "\e[#{code}m" + (blk ? blk.call + "\e[39m" : '')
          end
        end
      end

    end # Colours

  end # EscapeSequences

  Vedeu::EscapeSequences::Colours.setup!

end # Vedeu