using Shadowsocks.Model;
using Shadowsocks.Properties;
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.IO.Compression;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Text.RegularExpressions;

namespace Shadowsocks.Controller
{
    class PACServer
    {
        private static int PORT = 8093;
        private static string PAC_FILE = "pac.txt";
        private static Configuration config;

        Socket _listener;
        FileSystemWatcher watcher;

        GfwListUpdater gfwlistUpdater;

        public event EventHandler PACFileChanged;

        public void Start(Configuration configuration)
        {
            try
            {
                config = configuration;
                // Create a TCP/IP socket.
                _listener = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
                _listener.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true);
                IPEndPoint localEndPoint = null;
                if (configuration.shareOverLan)
                {
                    localEndPoint = new IPEndPoint(IPAddress.Any, PORT);
                }
                else
                {
                    localEndPoint = new IPEndPoint(IPAddress.Loopback, PORT);
                }

                // Bind the socket to the local endpoint and listen for incoming connections.
                _listener.Bind(localEndPoint);
                _listener.Listen(100);
                _listener.BeginAccept(
                    new AsyncCallback(AcceptCallback),
                    _listener);

                WatchPacFile();
                StartGfwListUpdater();
            }
            catch (SocketException)
            {
                _listener.Close();
                throw;
            }
        }

        public void Stop()
        {
            if (gfwlistUpdater != null)
            {
                gfwlistUpdater.Stop();
                gfwlistUpdater = null;
            }
            if (_listener != null)
            {
                _listener.Close();
                _listener = null;
            }
        }

        public string TouchPACFile()
        {
            if (File.Exists(PAC_FILE))
            {
                return PAC_FILE;
            }
            else
            {
                FileManager.UncompressFile(PAC_FILE, Resources.proxy_pac_txt);
                return PAC_FILE;
            }
        }

        // we don't even use it
        static byte[] requestBuf = new byte[2048];

        public void AcceptCallback(IAsyncResult ar)
        {
            Socket listener = (Socket)ar.AsyncState;
            try
            {
                Socket conn = listener.EndAccept(ar);

                object[] state = new object[] {
                    conn,
                    requestBuf
                };

                conn.BeginReceive(requestBuf, 0, requestBuf.Length, 0,
                    new AsyncCallback(ReceiveCallback), state);
            }
            catch (ObjectDisposedException)
            {
            }
            catch (Exception e)
            {
                Console.WriteLine(e);
            }
            finally
            {
                try
                {
                    listener.BeginAccept(
                        new AsyncCallback(AcceptCallback),
                        listener);
                }
                catch (ObjectDisposedException)
                {
                    // do nothing
                }
                catch (Exception e)
                {
                    Logging.LogUsefulException(e);
                }
            }
        }

        private string GetPACContent()
        {
            if (File.Exists(PAC_FILE))
            {
                return File.ReadAllText(PAC_FILE, Encoding.UTF8);
            }
            else
            {
                byte[] pacGZ = Resources.proxy_pac_txt;
                byte[] buffer = new byte[1024];  // builtin pac gzip size: maximum 100K
                MemoryStream sb = new MemoryStream();
                int n;
                using (GZipStream input = new GZipStream(new MemoryStream(pacGZ),
                    CompressionMode.Decompress, false))
                {
                    while((n = input.Read(buffer, 0, buffer.Length)) > 0)
                    {
                        sb.Write(buffer, 0, n);
                    }
                    return System.Text.Encoding.UTF8.GetString(sb.ToArray());
                }
            }
        }

        private void ReceiveCallback(IAsyncResult ar)
        {
            object[] state = (object[])ar.AsyncState;

            Socket conn = (Socket)state[0];
            byte[] requestBuf = (byte[])state[1];
            try
            {
                int bytesRead = conn.EndReceive(ar);

                string pac = GetPACContent();

                IPEndPoint localEndPoint = (IPEndPoint)conn.LocalEndPoint;

                string proxy = GetPACAddress(requestBuf, localEndPoint);

                pac = pac.Replace("__PROXY__", proxy);

                if (bytesRead > 0)
                {
                    string text = String.Format(@"HTTP/1.1 200 OK
Server: Shadowsocks
Content-Type: application/x-ns-proxy-autoconfig
Content-Length: {0}
Connection: Close

", System.Text.Encoding.UTF8.GetBytes(pac).Length) + pac;
                    byte[] response = System.Text.Encoding.UTF8.GetBytes(text);
                    conn.BeginSend(response, 0, response.Length, 0, new AsyncCallback(SendCallback), conn);
                    Util.Util.ReleaseMemory();
                }
                else
                {
                    conn.Close();
                }
            }
            catch (Exception e)
            {
                Console.WriteLine(e);
                conn.Close();
            }
        }

        private void SendCallback(IAsyncResult ar)
        {
            Socket conn = (Socket)ar.AsyncState;
            try
            {
                conn.Shutdown(SocketShutdown.Send);
            }
            catch
            { }
        }

        private void WatchPacFile()
        {
            if (watcher != null)
            {
                watcher.Dispose();
            }
            watcher = new FileSystemWatcher(Directory.GetCurrentDirectory());
            watcher.NotifyFilter = NotifyFilters.LastWrite | NotifyFilters.FileName | NotifyFilters.DirectoryName;
            watcher.Filter = PAC_FILE;
            watcher.Changed += Watcher_Changed;
            watcher.Created += Watcher_Changed;
            watcher.Deleted += Watcher_Changed;
            watcher.Renamed += Watcher_Changed;
            watcher.EnableRaisingEvents = true;
        }

        private void Watcher_Changed(object sender, FileSystemEventArgs e)
        {
            if (PACFileChanged != null)
            {
                PACFileChanged(this, new EventArgs());
            }
        }

        private string GetPACAddress(byte[] requestBuf, IPEndPoint localEndPoint)
        {
            string proxy = "PROXY " + localEndPoint.Address + ":8123;";
            //try
            //{
            //    string requestString = Encoding.UTF8.GetString(requestBuf);
            //    if (requestString.IndexOf("AppleWebKit") >= 0)
            //    {
            //        string address = "" + localEndPoint.Address + ":" + config.GetCurrentServer().local_port;
            //        proxy = "SOCKS5 " + address + "; SOCKS " + address + ";";
            //    }
            //}
            //catch (Exception e)
            //{
            //    Console.WriteLine(e);
            //}
            return proxy;
        }

        private void StartGfwListUpdater()
        {
            if (gfwlistUpdater != null)
            {
                gfwlistUpdater.Stop();
                gfwlistUpdater = null;
            }

            gfwlistUpdater = new GfwListUpdater();
            gfwlistUpdater.GfwListChanged += gfwlistUpdater_GfwListChanged;
            IPEndPoint localEndPoint = (IPEndPoint)_listener.LocalEndPoint;
            gfwlistUpdater.proxy = new WebProxy(localEndPoint.Address.ToString(), 8123);
            gfwlistUpdater.useSystemProxy = false;
            /* Delay 30 seconds, wait proxy start up. */
            gfwlistUpdater.ScheduleUpdateTime(30);
            gfwlistUpdater.Start();

        }

        private void gfwlistUpdater_GfwListChanged(object sender, GfwListUpdater.GfwListChangedArgs e)
        {
            if (e.GfwList == null || e.GfwList.Length == 0) return;
            string pacfile = TouchPACFile();
            string pacContent = File.ReadAllText(pacfile);
            string oldDomains;
            if (ClearPacContent(ref pacContent, out oldDomains))
            {
                StringBuilder sb = new StringBuilder();
                sb.AppendLine("{");
                for (int i = 0; i < e.GfwList.Length; i++)
                {
                    if (i == e.GfwList.Length - 1)
                        sb.AppendFormat("\t\"{0}\": {1}\r\n", e.GfwList[i], 1);
                    else
                        sb.AppendFormat("\t\"{0}\": {1},\r\n", e.GfwList[i], 1);
                }
                sb.Append("}");
                string newDomains = sb.ToString();
                if (!string.Equals(oldDomains, newDomains))
                {
                    pacContent = pacContent.Replace("__LAST_MODIFIED__", DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss"));
                    pacContent = pacContent.Replace("__DOMAINS__", newDomains);
                    File.WriteAllText(pacfile, pacContent);
                    Console.WriteLine("gfwlist updated - " + DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss"));
                }
            }
            else
            {
                Console.WriteLine("Broken pac file.");
            }
        }

        private bool ClearPacContent(ref string pacContent, out string oldDomains)
        {
            Regex regex = new Regex("(/\\*.*?\\*/\\s*)?var\\s+domains\\s*=\\s*(\\{(\\s*\"[^\"]*\"\\s*:\\s*\\d+\\s*,)*\\s*(\\s*\"[^\"]*\"\\s*:\\s*\\d+\\s*)\\})", RegexOptions.Singleline);
            Match m = regex.Match(pacContent);
            if (m.Success)
            {
                oldDomains = m.Result("$2");
                pacContent = regex.Replace(pacContent, "/* Last Modified: __LAST_MODIFIED__ */\r\nvar domains = __DOMAINS__");
                return true;
            }
            oldDomains = null;
            return false;
        }


    }
}