Use SASS functions to lighten/ darken a (hex) color Rails

color_util.rb

class ColorUtil
  class << self
    def lighten hex_color, percent
      adjust :lightness, hex_color, percent
    end

    def darken hex_color, percent
      adjust :lightness, hex_color, percent * -1
    end

    private
    def adjust action, hex_color, percent
      color = get_color hex_color
      color.with(action =>  Sass::Util.restrict(color.send(action).send(:+, percent * 100) , 0..100)).inspect
    end

    def get_color hex_color
      Sass::Script::Color.new hex_color.gsub('#','').scan(/../).map(&:hex)
    end
  end
end