require 'zlib'

@@cssPath = '../public/stylesheets/' #relative to where the script is running
@@imagePath = '../public/images/' #relative to where the script is running
@@styleSheets = ['myCssFile1.css', 'AntherCssFile.css']

def crc(fileName)
  fileName = @@imagePath + fileName.slice(10..-1)
  contents = File.read(fileName) ; nil
  Zlib.crc32(contents,0).to_s(16)
end

@@styleSheets.each do |css|
  fileName = @@cssPath + css
  file = File.new(fileName, 'r')
  lines = []
  while line = file.gets
    line.gsub! /\.\.\/images\/.*?\.(gif|jpg|png)(\?[a-z\d]+)?/ do |match|
      queryIndex = match.index("?")
      match = match.slice(0..queryIndex-1) unless queryIndex.nil?
      match + "?" + crc(match)
    end
    lines << line
  end
  file.close

  file = File.new(fileName, File::WRONLY|File::TRUNC)
  lines.each {|line| file.puts line }
  file.close
end