using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.IO.Compression;
using System.IO;
using System.Text.RegularExpressions;

public class CompressionModule : IHttpModule
{
    private IList<string> acceptedContentTypes;

    public CompressionModule()
    {
        acceptedContentTypes = new List<string> 
        { "text/html", "text/ccs", "text/javascript", "image/gif", "image/jpeg", "image/png" };
    }

    private void OnReleaseRequestState(object sender, EventArgs e)
    {
        HttpContext context = ((HttpApplication)sender).Context;
        string acceptEncoding = context.Request.Headers["Accept-Encoding"];
        string contentType = context.Response.ContentType.ToLower();

        /* Skal denne Content Type komprimeres og accepterer klienten komprimering? */
        if (acceptEncoding != null && acceptedContentTypes.Any
        (x => x.StartsWith(contentType, StringComparison.InvariantCultureIgnoreCase)))
        {
            acceptEncoding = acceptEncoding.ToLower();

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

    public void Init(HttpApplication context)
    {
        context.ReleaseRequestState += new EventHandler(OnReleaseRequestState);
    }

    public void Dispose() { }
}