CSS parsing

gistfile1.cs

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Text;
using System.IO;
using System.Threading;
using System.Web;
using System.Web.Caching;

namespace Common.CDN
{

    /*
     * 
     * Re parses the CSS to add in the cache key
     * 
     * add this into the web.config
     * 
     * <add name="CssRewriter" verb="*" path="*.css" preCondition="integratedMode" type="Common.CDN.CssRewriteHandler, Common" />
      
     * add it in system.webServer -> handlers
     * 
     * */

    public class CssRewriteHandler : IHttpHandler
    {
        public bool IsReusable { get { return true; } }

        public void ProcessRequest(HttpContext context)
        {

            string filename = context.Request.PhysicalPath;

            
            if (!File.Exists(filename))
            {
                context.Response.StatusCode = 404;
                return;
            }

            string css = File.ReadAllText(filename);
            string suffix = "";
            if (CDNHelper.IsCDNEnabled) //generic on/off switch for the whole CDN thing
            {

                object res = context.Cache["csscache|" + filename];

                if (res != null)
                {
                    css = res.ToString();
                    context.Response.Write("/* Processed by the CDN CSS rewriter from cache */\n");
                }
                else
                {

                    Stopwatch sw = new Stopwatch();
                    sw.Start();
                    //our unique cache id. usually the time, rounded down to 15 mins, eg 0115 or 0245. 
                    // means our cache is wiped out every 15 mins, but thats ok in this case.
                    // goes on the end of the URLs eg foo.jpg?0115
                    suffix = CDNHelper.UniqueId; 

                    css = css.Replace(".jpg", ".jpg" + suffix)
                        .Replace(".png", ".png" + suffix)
                        .Replace(".gif", ".gif" + suffix);

                    sw.Stop();

                    context.Cache.Add("csscache|" + filename, css, new CacheDependency(filename), DateTime.Now.AddMinutes(60), Cache.NoSlidingExpiration, CacheItemPriority.Normal,null);

                    context.Response.Write(string.Format("/* Processed by the CDN CSS rewriter in {0}ms */\n", sw.ElapsedMilliseconds));
                }
            }
            context.Response.Write(css);
            context.Response.ContentType = "text/css";
            context.Response.AddFileDependency(filename);

            HttpCachePolicy cache = context.Response.Cache;
            cache.SetCacheability(HttpCacheability.Public);

            if (CDNHelper.IsCDNEnabled)
            {
                cache.SetETag(suffix);
            }
            cache.SetLastModifiedFromFileDependencies();
            cache.SetMaxAge(TimeSpan.FromMinutes(60));
            cache.SetRevalidation(HttpCacheRevalidation.AllCaches);
            
            
        }
    }

}