#region Using

using System;
using System.IO;
using System.Web;
using System.Text;
using System.Text.RegularExpressions;

#endregion

/// <summary>
/// Removes whitespace from the webpage.
/// </summary>
public class ViewstateModule : IHttpModule
{

  #region IHttpModule Members

  void IHttpModule.Dispose()
  {
    // Nothing to dispose; 
  }

  void IHttpModule.Init(HttpApplication context)
  {
    context.BeginRequest += new EventHandler(context_BeginRequest);
  }

  #endregion

  void context_BeginRequest(object sender, EventArgs e)
  {
    HttpApplication app = sender as HttpApplication;
    if (app.Request.Url.OriginalString.Contains(".aspx"))
    {
      app.Response.Filter = new ViewstateFilter(app.Response.Filter);
    }
  }

  #region Stream filter

  private class ViewstateFilter : Stream
  {

    public ViewstateFilter(Stream sink)
    {
      _sink = sink;
    }

    private Stream _sink;

    #region Properites

    public override bool CanRead
    {
      get { return true; }
    }

    public override bool CanSeek
    {
      get { return true; }
    }

    public override bool CanWrite
    {
      get { return true; }
    }

    public override void Flush()
    {
      _sink.Flush();
    }

    public override long Length
    {
      get { return 0; }
    }

    private long _position;
    public override long Position
    {
      get { return _position; }
      set { _position = value; }
    }

    #endregion

    #region Methods

    public override int Read(byte[] buffer, int offset, int count)
    {
      return _sink.Read(buffer, offset, count);
    }

    public override long Seek(long offset, SeekOrigin origin)
    {
      return _sink.Seek(offset, origin);
    }

    public override void SetLength(long value)
    {
      _sink.SetLength(value);
    }

    public override void Close()
    {
      _sink.Close();
    }

    public override void Write(byte[] buffer, int offset, int count)
    {
      byte[] data = new byte[count];
      Buffer.BlockCopy(buffer, offset, data, 0, count);
      string html = System.Text.Encoding.Default.GetString(buffer);

      int startPoint = html.IndexOf("<input type=\"hidden\" name=\"__VIEWSTATE\"");
      if (startPoint >= 0)
      {
        int endPoint = html.IndexOf("/>", startPoint) + 2;
        string viewstateInput = html.Substring(startPoint, endPoint - startPoint);
        html = html.Remove(startPoint, endPoint - startPoint);
        int formEndStart = html.IndexOf("</form>") - 1;
        if (formEndStart >= 0)
        {
          html = html.Insert(formEndStart, viewstateInput);
        }
      }

      byte[] outdata = System.Text.Encoding.Default.GetBytes(html);
      _sink.Write(outdata, 0, outdata.GetLength(0));
    }

    #endregion

  }

  #endregion

}