javascript_and_css_minimization.rb

#This code is MIT licensed.

module ActionView
  module Helpers
    module AssetTagHelper
      require 'jsminlib'  #Google it.  Paste into RAILS_ROOT/libs.  Note: not MIT license (has a "This code should be used for good, not evil" rider -- ask your lawyers if they care).

      def compress_css(source)
        source.gsub!(/\s+/, " ")           # collapse space
        source.gsub!(/\/\*(.*?)\*\/ /, "") # remove comments
        source.gsub!(/\} /, "}\n")         # add line breaks
        source.gsub!(/\n$/, "")            # remove last break
        source.gsub!(/ \{ /, " {")         # trim inside brackets
        source.gsub!(/; \}/, "}")          # trim inside brackets

        source.gsub!("http://", "https://") if request.ssl?   #Causes background images linked in CSS files to automatically go to HTTPS if those CSS files are cached from HTTPS requests.  You should probably use :cache => request.ssl? ? "secure-foo" : "standard-foo" so that the proper cache is used for each kind of request in the future. 
        source
      end

      def get_file_contents(filename)
        contents = File.read(filename)
        if filename =~ /\.js$/
          JSMin.minimize(contents)
        elsif filename =~ /\.css$/
          compress_css(contents)
        end
      end

      def join_asset_file_contents(paths)
        paths.collect { |path|
          get_file_contents(File.join(ASSETS_DIR, path.split("?").first)) }.join("\n\n")
      end

    end
  end
end