using System;
using System.IO;
using System.Web;

public class ScriptReplaceModule : IHttpModule
{
    public void Init(HttpApplication app)
    {
        app.BeginRequest += OnBeginRequest;
    }
    protected void OnBeginRequest(object sender, EventArgs e)
    {
        HttpResponse resp = ((HttpApplication)sender).Response;
        resp.Filter = new ScriptReplace(resp.Filter);
    }
    public void Dispose()
    {
    }
}

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

public class ScriptReplace : Stream
{
    private Stream real;
    private Stream temp;
    public ScriptReplace(Stream real)
    {
        this.real = real;
        this.temp = new MemoryStream();
    }
    public override bool CanRead
    {
        get
        {
            return false;
        }
    }
    public override bool CanSeek
    {
        get
        {
            return false;
        }
    }
    public override bool CanWrite
    {
        get
        {
            return true;
        }
    }
    public override long Length
    {
        get
        {
            return temp.Length;
        }
    }
    public override long Position
    {
        get
        {
            return temp.Position;
        }
        set
        {
            throw new NotSupportedException();
        }
    }
    public override int Read(byte[] buffer, int offset, int count)
    {
        throw new NotSupportedException();
    }
    public override long Seek(long offset, SeekOrigin direction)
    {
        throw new NotSupportedException();
    }
    public override void SetLength(long length)
    {
        throw new NotSupportedException();
    }
    public override void Close()
    {
        temp.Close();
        StreamReader sr = new StreamReader(new MemoryStream(((MemoryStream)temp).ToArray()), Encoding.UTF8);
        StreamWriter sw = new StreamWriter(real, Encoding.UTF8);
        string line;
        while((line = sr.ReadLine()) != null)
        {
            line = Regex.Replace(line, @"(<script src="")([^""]+)("">)", "$1/js/$2$3");
            sw.WriteLine(line);
        }
        sr.Close();
        sw.Close();
    }
    public override void Flush()
    {
        temp.Flush();
    }
    public override void Write(byte[] buffer, int offset, int count)
    {
        temp.Write(buffer, offset, count);
    }
}