string_rgb.rb

module StringRGB
  def rgb(r, g=nil, b=nil)
    original = r

    if g.nil?
      # check for 'short' form values like 0x8cf and expand to 0x88ccff
      if r < 4096
        b = r & 0xf | (r << 4 & 0xf0)
        g = (r >> 4 & 0xf) | (r & 0xf0)
        r = (r >> 8 & 0xf) | (r >> 4 & 0xf0)
      else
        b = r & 0xff
        g = (r >> 8) & 255
        r = (r >> 16) & 255
      end
    end

    "\x1b[38;2;#{r};#{g};#{b}m#{self}\x1b[0m"
  end
end

String.include StringRGB

# example
# puts "FAIL".rgb(0xf00)  # short-hand for 0xff0000
# puts "PASS".rgb(0x00ff00)