using System;
using System.IO.Compression;
using System.Web;
using System.Web.UI;

namespace GZipTest
{
    public class Global : HttpApplication
    {
        void Application_PreRequestHandlerExecute(object sender, EventArgs e)
        {
            var app = sender as HttpApplication;
            if (app == null) return;

            var acceptEncoding = app.Request.Headers["Accept-Encoding"];
            var prevUncompressedStream = app.Response.Filter;

            if (!(app.Context.CurrentHandler is Page ||
              app.Context.CurrentHandler.GetType().Name == "SyncSessionlessHandler") ||
            app.Request["HTTP_X_MICROSOFTAJAX"] != null)
                return;

            if (string.IsNullOrEmpty(acceptEncoding))
                return;

            acceptEncoding = acceptEncoding.ToLower();

            if (acceptEncoding.Contains("deflate") || acceptEncoding == "*")
            {
                // defalte
                app.Response.Filter = new DeflateStream(prevUncompressedStream, CompressionMode.Compress);
                app.Response.AppendHeader("Content-Encoding", "deflate");
            }
            else if (acceptEncoding.Contains("gzip"))
            {
                // gzip
                app.Response.Filter = new GZipStream(prevUncompressedStream, CompressionMode.Compress);
                app.Response.AppendHeader("Content-Encoding", "gzip");
            }
        }
    }
}