Google Analytics Rack

google_analytics.rb

module Rack
  class GoogleAnalytics    
    def initialize(app,id)
      @app = app
      @id  = id
    end
    
    def call(env)
      status,headers,response = @app.call(env)
      response.each do |part|
        if part =~ /<\/body>/
          # The begin/rescue block is required because this method craps out
          # when the static page is stored in memcached and not the file system
          begin
            part.sub!(/<\/body>/, "#{tracking_code}</body>")
          rescue
          end
        end
      end
      headers['Content-Length'] = response.length.to_s
      [status,headers,response]
    end
    
    private    
    def tracking_code
      code = <<-END_CODE
        <script type="text/javascript">
          var gaJsHost = (("https:" == document.location.protocol) ? "https://ssl." : "http://www.");
          document.write(unescape("%3Cscript src='" + gaJsHost + "google-analytics.com/ga.js' type='text/javascript'%3E%3C/script%3E"));
        </script>
        <script type="text/javascript">
          try {
            var pageTracker = _gat._getTracker(#{@id});
            pageTracker._trackPageview();
          } catch(err) {}
        </script>
      END_CODE
      code
    end
  end
end