middleman--middleman/lib/middleman/rack/minify_css.rb

begin
  require "yui/compressor"
rescue LoadError
  puts "YUI-Compressor not available. Install it with: gem install yui-compressor"
end

class Middleman::Rack::MinifyCSS
  def initialize(app, options={})
    @app = app
  end

  def call(env)
    if Middleman::Base.enabled?(:minify_css) &&
       env["DOWNSTREAM"] && env["PATH_INFO"].match(/\.css$/)

      compressor = ::YUI::CssCompressor.new

      source = env["DOWNSTREAM"][2].is_a?(::Rack::File) ?
                 File.read(env["DOWNSTREAM"][2].path) :
                 env["DOWNSTREAM"][2]

      env["DOWNSTREAM"][2] = compressor.compress(source)
      env["DOWNSTREAM"][1]["Content-Length"] = ::Rack::Utils.bytesize(env["DOWNSTREAM"][2]).to_s
    end

    @app.call(env)
  end
end