source: branches/HeuristicLab.Problems.GrammaticalOptimization/SharpVectorCore/Utils/Net/ExtendedHttpWebRequest.cs @ 13825

using System;
using System.Diagnostics;
using System.Net;
using System.Xml;
using System.IO;
using System.IO.Compression;

namespace SharpVectors.Net
{
  public class ExtendedHttpWebRequestCreator : IWebRequestCreate
  {
    public ExtendedHttpWebRequestCreator(){}
    public WebRequest Create(Uri uri){return new ExtendedHttpWebRequest(uri);}
  }

  public class ExtendedHttpWebRequest : WebRequest
  {
    #region CacheManager
    private static ICacheManager cacheManager = new NoCacheManager();
    public static ICacheManager CacheManager
    {
      get{return cacheManager;}
      set{cacheManager = value;}
    }
    #endregion

    #region Registration
    public static bool Register()
    {
      return WebRequest.RegisterPrefix("http://", new ExtendedHttpWebRequestCreator());
    }
    #endregion

    #region Constructors
    internal ExtendedHttpWebRequest(Uri uri)
    {
      requestUri = uri;
    }
    #endregion

    #region RequestUri
    private Uri requestUri;
    public override Uri RequestUri
    {
      get
      {
        return requestUri;
      }
    }
    #endregion

    private WebRequest getRequest(CacheInfo cacheInfo)
    {
      WebRequest request;
      if(cacheInfo != null && 
        cacheInfo.CachedUri != null && 
        cacheInfo.Expires > DateTime.Now)
      {
        request = WebRequest.Create(cacheInfo.CachedUri);
      }
      else
      {
        request = WebRequest.CreateDefault(RequestUri);
      }

      HttpWebRequest hRequest = request as HttpWebRequest;
      if(hRequest != null && cacheInfo != null && cacheInfo.CachedUri != null)
      {
        if(cacheInfo.ETag != null)
        {
          hRequest.Headers["If-None-Match"] = cacheInfo.ETag;
        }
        if(cacheInfo.LastModified != DateTime.MinValue)
        {
          hRequest.IfModifiedSince = cacheInfo.LastModified;
        }

        hRequest.Headers["Accept-Encoding"] = "deflate, gzip" ;
      }

      return request;
    }

    private WebResponse getResponse(WebRequest request, CacheInfo cacheInfo)
    {
      WebResponse response = null;
      try
      {
        response = request.GetResponse();
      }
      catch(WebException webEx)
      {
        HttpWebResponse hresp2 = webEx.Response as HttpWebResponse;
        if(hresp2 != null)
        {
          if(hresp2.StatusCode == HttpStatusCode.NotModified)
          {
            
            if(cacheInfo != null && cacheInfo.CachedUri != null)
            {
              request = WebRequest.Create(cacheInfo.CachedUri);
            }
            else
            {
              request = WebRequest.Create(RequestUri);
            }
            response = request.GetResponse();
          }
        }
      }

      return response;
    }

    private CacheInfo processResponse(WebResponse response)
    {
      HttpWebResponse hResponse = response as HttpWebResponse;
      CacheInfo cacheInfo = null;

      if(hResponse != null)
      {
        DateTime expires;
        if(hResponse.Headers["Expires"] != null)
        {
          expires = DateTime.Parse(hResponse.Headers["Expires"]);
        }
        else
        {
          expires = DateTime.MinValue;
        }
      
        cacheInfo = new CacheInfo(expires, hResponse.Headers["Etag"], hResponse.LastModified, null, hResponse.ContentType);
      }

      return cacheInfo;
    }

    private Stream processResponseStream(WebResponse response)
    {
      Stream respStream = response.GetResponseStream();

      string contentEnc = response.Headers["Content-Encoding"];
      if ( contentEnc != null) 
      {
        contentEnc = contentEnc.ToLower() ;
        if ( contentEnc == "gzip" ) 
        {
          respStream = new GZipStream(respStream, CompressionMode.Decompress) ;
        }
        else if ( contentEnc == "deflate" ) 
        {
                    respStream = new DeflateStream(respStream, CompressionMode.Decompress);
        }
      }
      else if(requestUri.ToString().EndsWith(".svgz"))
      {
        // TODO: this is an ugly hack for .svgz files. Fix later!
                respStream = new GZipStream(respStream, CompressionMode.Decompress);
      }
        
      Stream stream = new MemoryStream();
      int count = 0;
      byte[] buffer = new byte[4096];
      while((count = respStream.Read(buffer, 0, 4096)) > 0) stream.Write(buffer, 0, count);

      stream.Position = 0;
      
      ((IDisposable)respStream).Dispose();

      return stream;
    }

    public override WebResponse GetResponse()
    {
      CacheInfo cacheInfo = CacheManager.GetCacheInfo(RequestUri);

      WebRequest request = getRequest(cacheInfo);
      WebResponse response = getResponse(request, cacheInfo);

      Stream stream = processResponseStream(response);

      if(response is HttpWebResponse)
      {
        CacheInfo respCacheInfo = processResponse(response);

        CacheManager.SetCacheInfo(RequestUri, respCacheInfo, stream);
      }

      return new ExtendedHttpWebResponse(RequestUri, response, stream, cacheInfo);
    }
  }
}