/*
 * Copyright (c) Contributors, http://opensimulator.org/
 * See CONTRIBUTORS.TXT for a full list of copyright holders.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name of the OpenSim Project nor the
 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

using System;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Net;
using System.Reflection;
using System.Text.RegularExpressions;
using System.Threading;
using log4net;
using HttpServer;

namespace OpenSim.Framework.Servers
{
    /// <summary>
    /// An OSHttpRequestPump fetches incoming OSHttpRequest objects
    /// from the OSHttpRequestQueue and feeds them to all subscribed
    /// parties. Each OSHttpRequestPump encapsulates one thread to do
    /// the work and there is a fixed number of pumps for each
    /// OSHttpServer object.
    /// </summary>
    public class OSHttpRequestPump
    {
        private static readonly ILog _log = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);

        protected OSHttpServer _server;
        protected OSHttpRequestQueue _queue;
        protected Thread _engine;

        private int _id;
        
        public string EngineID
        {
            get { return String.Format("{0}-{1}", _server.EngineID, _id); }
        }

        
        public OSHttpRequestPump()
        {
            _engine = new Thread(new ThreadStart(Engine));
            _engine.Name = EngineID;
            _engine.IsBackground = true;
            _engine.Start();

            ThreadTracker.Add(_engine);

        }

        public static OSHttpRequestPump[] Pumps(OSHttpServer server, OSHttpRequestQueue queue, int poolSize)
        {
            OSHttpRequestPump[] pumps = new OSHttpRequestPump[poolSize];
            for (int i = 0; i < pumps.Length; i++)
            {
                pumps[i]._server = server;
                pumps[i]._queue = queue;
                pumps[i]._id = i;
            }

            return pumps;
        }

        public void Start()
        {
            _engine = new Thread(new ThreadStart(Engine));
            _engine.Name = EngineID;
            _engine.IsBackground = true;
            _engine.Start();

            ThreadTracker.Add(_engine);
        }

        public void Engine()
        {
            OSHttpRequest req = null;
            
            while (true)
            {
                try {
                    // dequeue an OSHttpRequest from OSHttpServer's
                    // request queue 
                    req = _queue.Dequeue();
                    
                    // get a copy of the list of registered handlers
                    List<OSHttpHandler> handlers = _server.OSHttpHandlers;
                    
                    // prune list and have it sorted from most
                    // specific to least specific
                    handlers = MatchHandlers(req, handlers);
                        
                    // process req: we try each handler in turn until
                    // we are either out of handlers or get back a
                    // Handled or Detached
                    OSHttpHandlerResult rc = OSHttpHandlerResult.Unprocessed;
                    foreach (OSHttpHandler h in handlers)
                    {
                        rc = h.Process(req);
                            
                        // Pass: handler did not process the request,
                        // try next handler
                        if (OSHttpHandlerResult.Pass == rc) continue;
                        // Detached: handler is taking over processing
                        // of request, we are done
                        if (OSHttpHandlerResult.Detached == rc) break;
                            
                        if (OSHttpHandlerResult.Handled != rc)
                        {
                            // something went wrong
                            throw new Exception(String.Format("[{0}] got unexpected OSHttpHandlerResult {1}", EngineID, rc));
                        }
                            
                        // Handled: clean up now
                        req.HttpRequest.AddHeader("keep-alive", "false");

                        break;
                    }
                        
                }
                catch (Exception e)
                {
                    _log.DebugFormat("[{0}] OSHttpHandler problem: {1}", EngineID, e.ToString());
                    _log.ErrorFormat("[{0}] OSHttpHandler problem: {1}", EngineID, e.Message);
                }
            }
        }

        protected List<OSHttpHandler> MatchHandlers(OSHttpRequest req, List<OSHttpHandler> handlers)
        {
            Dictionary<OSHttpHandler, int> scoredHandlers = new Dictionary<OSHttpHandler, int>();

            foreach (OSHttpHandler h in handlers)
            {
                Regex pathRegex = h.Path;
                Dictionary<string, Regex> headerRegexs = h.Headers;
                Regex endPointsRegex = h.IPEndPointWhitelist;


                // first, check whether IPEndPointWhitelist applies
                // and, if it does, whether client is on that white
                // list.
                if (null != endPointsRegex)
                {
                    // TODO: following code requires code changes to
                    // HttpServer.HttpRequest to become functional

                    IPEndPoint remote = req.RemoteIPEndPoint;
                    if (null != remote)
                    {
                        Match epm = endPointsRegex.Match(remote.ToString());
                        if (!epm.Success) continue;
                    }
                }

                // whitelist ok, now check path
                if (null != pathRegex)
                {
                    Match m = pathRegex.Match(req.HttpRequest.Uri.AbsolutePath);
                    if (!m.Success) continue;

                    scoredHandlers[h] = m.ToString().Length;
                }

                // whitelist & path ok, now check headers
                if (null != headerRegexs)
                {
                    int headersMatch = 0;

                    // go through all header Regexs and evaluate
                    // match: 
                    //     if header field not present or does not match: 
                    //         remove handler from scoredHandlers 
                    //         continue
                    //     else: 
                    //         add increment headersMatch
                    NameValueCollection headers = req.HttpRequest.Headers;
                    foreach (string tag in headerRegexs.Keys)
                    {
                        if (null != headers[tag])
                        {
                            Match hm = headerRegexs[tag].Match(headers[tag]);
                            if (hm.Success) {
                                headersMatch++;
                                continue;
                            }
                        }

                        scoredHandlers.Remove(h);
                        break;
                    }
                    // check whether h got kicked out
                    if (!scoredHandlers.ContainsKey(h)) continue;

                    scoredHandlers[h] +=  headersMatch;
                }
            }
            
            List<OSHttpHandler> matchingHandlers = new List<OSHttpHandler>(scoredHandlers.Keys);
            matchingHandlers.Sort(delegate(OSHttpHandler x, OSHttpHandler y)
                                  {
                                      return scoredHandlers[x] - scoredHandlers[y];
                                  });

            return matchingHandlers;
        }
        
    }
}