Rake task to format url() calls in stylesheets to the Rails 3.1+ image-url sass helper as well as clean up the url in the process

format_stylesheets_for_asset_pipeline.rb

desc "Replaces and reformats url() calls in .scss files with image-url()"
task :format_stylesheets_for_asset_pipeline do
  regex = /(url)\(('?|"?)(\/images\/)([^"']*)('?|"?)\)/
  
  Dir.glob("app/assets/stylesheets/**/*.scss") do |filename| 
    unless File.directory?(filename)
      output = "" 
      lines = []

      file = File.open(filename, "r")

      file.each_line do |line|
        if m = regex.match(line)
          replaced_line = line.sub(regex,'image-url("' + m[4] + '")')
          lines << replaced_line
          output += "found match: #{m[4]}\noriginal line: #{line}replaced line: #{replaced_line}\n"
        else
          lines << line
        end
      end

      file.close

      file = File.open(filename, "w")
      lines.each {|line| file.write line}
      file.close

      puts "In #{filename}:\n\n" + output + "\n\n" if output.present?
    end
  end
end