.net http proxy hack to allow javascript in the browser to authenticate against IIS and have the server call out to antother server

APIProxyHandler.cs

/*

This allows a javascript app to hit a relative url such as 

/Proxy/myapp.com/api/rest/2/issues

and then have the server make a call to

http://myapp.com/api/rest/2/issues

the IIS container injects the User obj based on our Active Directory and I turn that into an API token using an encryption scheme.


we do some hacking on a localhost url such as 
/Proxy/localhost/api/rest/2/issues

so that calls back to 
http://localhost/api/rest/2/issues and is always a GET - this facilitates having local text files that mock server data for dev and UI testing.



/*
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Net.Http.Formatting;
using System.Net.Http.Headers;
using System.Text;
using System.Web;
using System.Web.Routing;
using System.Web.Script.Serialization;
using Newtonsoft.Json;

namespace Proxy.Net
{
    public class APIProxyHandler : IHttpHandler, IRouteHandler
    {
        public const string SCHEME_DELIM = "://";
        public const string PROXY_IDENTIFIER = "proxy";

        public bool IsReusable
        {
            get { return true; }
        }

        public void ProcessRequest(HttpContext context)
        {
            bool isLocal      = false;
            string url        = context.Request.Url.OriginalString.ToLower();
            int eOfSchemeIndx = url.IndexOf(SCHEME_DELIM) + SCHEME_DELIM.Length;
            int eOfProxyIndx  = url.IndexOf(PROXY_IDENTIFIER) + PROXY_IDENTIFIER.Length + 1;

            url = url.Remove(eOfSchemeIndx, eOfProxyIndx - eOfSchemeIndx);

            if (url.Contains(SCHEME_DELIM + "localhost"))
            {
                url     = url.Replace(SCHEME_DELIM + "localhost", SCHEME_DELIM + "localhost:" + context.Request.Url.Port);
                isLocal = true;
            }

            var handler    = new HttpClientHandler { UseDefaultCredentials = true };
            var httpClient = new HttpClient(handler);            
            string method  = (isLocal) ? "GET" : context.Request.HttpMethod;

            httpClient.DefaultRequestHeaders.Add("ep-ad-user-name", generateApiToken(context.Request.LogonUserIdentity.Name));            

            HttpResponseMessage response = new HttpResponseMessage();
            if (method != "GET")
            {
                using (Stream stream = context.Request.GetBufferedInputStream())
                {
                    byte[] data = new byte[context.Request.ContentLength];

                    stream.Read(data, 0, context.Request.ContentLength);

                    StringContent content = new StringContent(ASCIIEncoding.ASCII.GetString(data), Encoding.UTF8, "application/json");
                    
                    if (method == "POST")
                        response = httpClient.PostAsync(url, content).Result;
                    else if (method == "PUT")
                        response = httpClient.PutAsync(url, content).Result;
                }
            }
            else
            {
                response = httpClient.GetAsync(url).Result;
            }

            // read data from response
            string serverResponse = response.Content.ReadAsStringAsync().Result;

            serverResponse = serverResponse.Replace("http://", "/proxy/");

            HttpResponse httpResponse = context.Response;
            httpResponse.ContentType  = "application/json; charcode=utf8";
            httpResponse.StatusCode   = (int)response.StatusCode;

            httpResponse.Write(serverResponse);
        }

        public IHttpHandler GetHttpHandler(RequestContext requestContext)
        {
            return this;
        }

    }
}