require 'pygments'
 require 'fileutils'
 require 'digest/md5'
 
 PYGMENTS_CACHE_DIR = File.expand_path('../../_code_cache', __FILE__)
 FileUtils.mkdir_p(PYGMENTS_CACHE_DIR)
 
 module HighlightCode
   def highlight(str, lang)

     str = pygments(str, lang).match(/<pre>(.+)<\/pre>/m)[1].to_s.gsub(/ *$/, '') #strip out divs <div class="highlight">

     table = '<div class="highlight"><table cellpadding="0" cellspacing="0"><tr><td class="gutter"><pre class="line-numbers">'
     code = ''
     str.lines.each_with_index do |line,index|
       table += "<span class='line'>#{index+1}</span>\n"
       code  += "<div class='line'>#{line}</div>"
     end
     table += "</pre></td><td class='code' width='100%'><pre><code class='#{lang}'>#{code}</code></pre></td></tr></table></div>"
   end
 
   def pygments(code, lang)
     if defined?(PYGMENTS_CACHE_DIR)
       path = File.join(PYGMENTS_CACHE_DIR, "#{lang}-#{Digest::MD5.hexdigest(code)}.html")
       if File.exist?(path)
         highlighted_code = File.read(path)
       else
         highlighted_code = Pygments.highlight(code, :lexer => lang, :formatter => 'html')
         File.open(path, 'w') {|f| f.print(highlighted_code) }
       end
     else
       highlighted_code = Pygments.highlight(code, :lexer => lang, :formatter => 'html')
     end
     highlighted_code
   end
 end