Fast ASP.NET Web page loading by downloading multiple JavaScripts after visible content and in batch

<%@ WebHandler Language="C#" Class="Scripts" %>

using System;
using System.Collections.Generic;
using System.Text;
using System.IO;
using System.Web;
using System.Net;

using Dropthings.Web.Util;

public class Scripts : IHttpHandler {
    
    public void ProcessRequest (HttpContext context) {

        
        string queryString = HttpUtility.UrlDecode(context.Request.QueryString.ToString());

        string[] urlSplit = queryString.Split('&');

        string setInfo = urlSplit[0];
        string urlPrefix = urlSplit[1];

        string[] tokens = setInfo.Split('=');
        string setName = tokens[0];
        string[] urlMaps = tokens[1].Split(',');

        byte[] encodedBytes;

        if (context.Cache[setInfo] == null)
        {
            // Find the set
            UrlMapSet set = CombineScripts.LoadSets().Find(
                new Predicate<UrlMapSet>(delegate(UrlMapSet match)
                    {
                        return match.Name == setName;
                    }));

            // Find the URLs requested to be rendered            
            List<UrlMap> maps = string.IsNullOrEmpty(tokens[1]) ? set.Urls 
                : set.Urls.FindAll(new Predicate<UrlMap>(delegate(UrlMap map)
                    {
                        return Array.BinarySearch<string>(urlMaps, map.Name) >= 0;
                    }));

            string urlScheme = context.Request.Url.GetComponents(UriComponents.SchemeAndServer, UriFormat.Unescaped);

            StringBuilder buffer = new StringBuilder();
            foreach (UrlMap map in maps)
            {
                /*
                 * Urls can be in one of the following formats:
                 * a) Relative url to the page
                 * b) Relative url starting with application path e.g. /Dropthings/....
                 * c) Absolute url with http:// prefix
                 */

                string fullUrl = map.Url;
                if (map.Url.StartsWith("http://")) fullUrl = map.Url;
                else if (map.Url.StartsWith(context.Request.ApplicationPath)) fullUrl = urlScheme + map.Url;
                else fullUrl = urlScheme + urlPrefix + map.Url;

                string mapUrlForJS = HttpUtility.HtmlDecode(map.Url).Replace("'", "\'");
                HttpWebRequest request = this.CreateHttpWebRequest(fullUrl);
                try
                {
                    using (HttpWebResponse response = request.GetResponse() as HttpWebResponse)
                    {
                        if (response.StatusCode == HttpStatusCode.OK)
                        {
                            using (StreamReader reader = new StreamReader(response.GetResponseStream()))
                            {
                                string responseContent = reader.ReadToEnd();
                                buffer.Append(responseContent);
                                buffer.Append(Environment.NewLine);
                                buffer.Append(@"
                            if(typeof(Sys)!=='undefined') Array.add(Sys._ScriptLoader._getLoadedScripts(), '" + mapUrlForJS + @"'); 
                            if( !window._combinedScripts ) { window._combinedScripts = []; } 
                            window._combinedScripts.push('" + mapUrlForJS + @"');");
                                buffer.Append(Environment.NewLine);
                            }
                        }
                        else
                        {
                            buffer.Append("alert(\"Cannot load script from:" + mapUrlForJS + ". Please correct mapping for '" + map.Name + "' in App_Data\\\\FileSets.xml\");");
                            buffer.Append(Environment.NewLine);
                        }
                    }
                }
                catch (Exception x)
                {
                    buffer.Append("alert(\"Cannot load script from:" + mapUrlForJS + ". Please correct mapping for '" + map.Name + "' in App_Data\\\\FileSets.xml\");");
                    buffer.Append(Environment.NewLine);
                }
            }

            buffer.Append(@"
                if(typeof(Sys)!=='undefined')             
                {                
                    if(typeof(Sys._ScriptLoader) !== 'undefined')
                    {                                    
                        Sys._ScriptLoader.isScriptLoaded = function Sys$_ScriptLoader$isScriptLoaded(scriptSrc) 
                        {                                                    
                            var dummyScript = document.createElement('script');
                            dummyScript.src = scriptSrc;
                            var result = Array.contains(Sys._ScriptLoader._getLoadedScripts(), scriptSrc);
                            if( result === true ) return true;
                            result = Array.contains( window._combinedScripts, scriptSrc );
                            if( result === true ) return true;                            
                            var scriptTags = document.getElementsByTagName('script');
                            for(var i = 0; i < scriptTags.length; i ++ ) if( scriptTags[i].src == dummyScript.src ) return true;
                            return false;
                        }
                    }                    
                }");

            string responseString = buffer.ToString();
            encodedBytes = context.Request.ContentEncoding.GetBytes(responseString);
            //context.Cache.Add(setInfo, encodedBytes, null, DateTime.MaxValue,
            //    TimeSpan.FromDays(1), System.Web.Caching.CacheItemPriority.Normal, null);
        }
        else
        {
            encodedBytes = context.Cache[setInfo] as byte[];
        }
        
        context.Response.ContentType = "text/javascript";
        context.Response.ContentEncoding = context.Request.ContentEncoding;
        context.Response.Cache.SetMaxAge(TimeSpan.FromDays(30));
        context.Response.Cache.SetExpires(DateTime.Now.AddDays(30));
        context.Response.Cache.SetCacheability(HttpCacheability.Private);
        context.Response.AppendHeader("Content-Length", encodedBytes.Length.ToString());
        
        context.Response.OutputStream.Write(encodedBytes, 0, encodedBytes.Length);
        context.Response.Flush();
    }
 
    public bool IsReusable {
        get {
            return false;
        }
    }

    private HttpWebRequest CreateHttpWebRequest(string url)
    {
        HttpWebRequest request = WebRequest.Create(url) as HttpWebRequest;
        request.Headers.Add("Accept-Encoding", "gzip");
        request.AutomaticDecompression = DecompressionMethods.GZip;
        request.MaximumAutomaticRedirections = 2;
        request.MaximumResponseHeadersLength = 4 * 1024;
        request.ReadWriteTimeout = 1 * 1000;
        request.Timeout = 5 * 1000;

        return request;
    }
}