#region License
/*
 * HttpServer.cs
 *
 * The MIT License
 *
 * Copyright (c) 2012-2013 sta.blockhead
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
#endregion

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Security.Cryptography.X509Certificates;
using System.Threading;
using WebSocketSharp.Net;

namespace WebSocketSharp.Server
{
  /// <summary>
  /// Provides a simple HTTP server that allows to accept the WebSocket connection requests.
  /// </summary>
  /// <remarks>
  /// The HttpServer instance can provide the multi WebSocket services.
  /// </remarks>
  public class HttpServer
  {
    #region Private Fields

    private HttpListener                _listener;
    private volatile bool               _listening;
    private Logger                      _logger;
    private int                         _port;
    private Thread                      _receiveRequestThread;
    private string                      _rootPath;
    private bool                        _secure;
    private WebSocketServiceHostManager _serviceHosts;
    private volatile ServerState        _state;
    private object                      _sync;
    private bool                        _windows;

    #endregion

    #region Public Constructors

    /// <summary>
    /// Initializes a new instance of the <see cref="HttpServer"/> class that listens for incoming requests
    /// on port 80.
    /// </summary>
    public HttpServer ()
      : this (80)
    {
    }

    /// <summary>
    /// Initializes a new instance of the <see cref="HttpServer"/> class that listens for incoming requests
    /// on the specified <paramref name="port"/>.
    /// </summary>
    /// <param name="port">
    /// An <see cref="int"/> that contains a port number. 
    /// </param>
    /// <exception cref="ArgumentOutOfRangeException">
    /// <paramref name="port"/> is 0 or less, or 65536 or greater.
    /// </exception>
    public HttpServer (int port)
      : this (port, port == 443 ? true : false)
    {
    }

    /// <summary>
    /// Initializes a new instance of the <see cref="HttpServer"/> class that listens for incoming requests
    /// on the specified <paramref name="port"/> and <paramref name="secure"/>.
    /// </summary>
    /// <param name="port">
    /// An <see cref="int"/> that contains a port number. 
    /// </param>
    /// <param name="secure">
    /// A <see cref="bool"/> that indicates providing a secure connection or not.
    /// (<c>true</c> indicates providing a secure connection.)
    /// </param>
    /// <exception cref="ArgumentOutOfRangeException">
    /// <paramref name="port"/> is 0 or less, or 65536 or greater.
    /// </exception>
    /// <exception cref="ArgumentException">
    /// Pair of <paramref name="port"/> and <paramref name="secure"/> is invalid.
    /// </exception>
    public HttpServer (int port, bool secure)
    {
      if (!port.IsPortNumber ())
        throw new ArgumentOutOfRangeException ("port", "Invalid port number: " + port);

      if ((port == 80 && secure) || (port == 443 && !secure))
        throw new ArgumentException (String.Format (
          "Invalid pair of 'port' and 'secure': {0}, {1}", port, secure));

      _port = port;
      _secure = secure;

      init ();
    }

    #endregion

    #region Public Properties

    /// <summary>
    /// Gets or sets the certificate used to authenticate the server on the secure connection.
    /// </summary>
    /// <value>
    /// A <see cref="X509Certificate2"/> used to authenticate the server.
    /// </value>
    public X509Certificate2 Certificate {
      get {
        return _listener.DefaultCertificate;
      }

      set {
        if (_listening)
        {
          _logger.Error (
            "The value of Certificate property cannot be changed because the server has already been started.");
          return;
        }

        if (EndPointListener.CertificateExists (_port, _listener.CertificateFolderPath))
          _logger.Warn ("Server certificate associated with the port number already exists.");

        _listener.DefaultCertificate = value;
      }
    }

    /// <summary>
    /// Gets a value indicating whether the server has been started.
    /// </summary>
    /// <value>
    /// <c>true</c> if the server has been started; otherwise, <c>false</c>.
    /// </value>
    public bool IsListening {
      get {
        return _listening;
      }
    }

    /// <summary>
    /// Gets a value indicating whether the server provides secure connection.
    /// </summary>
    /// <value>
    /// <c>true</c> if the server provides secure connection; otherwise, <c>false</c>.
    /// </value>
    public bool IsSecure {
      get {
        return _secure;
      }
    }

    /// <summary>
    /// Gets or sets a value indicating whether the server cleans up the inactive WebSocket sessions
    /// periodically.
    /// </summary>
    /// <value>
    /// <c>true</c> if the server cleans up the inactive WebSocket sessions every 60 seconds;
    /// otherwise, <c>false</c>. The default value is <c>true</c>.
    /// </value>
    public bool KeepClean {
      get {
        return _serviceHosts.KeepClean;
      }

      set {
        _serviceHosts.KeepClean = value;
      }
    }

    /// <summary>
    /// Gets the logging functions.
    /// </summary>
    /// <remarks>
    /// The default logging level is the <see cref="LogLevel.ERROR"/>.
    /// If you want to change the current logging level, you set the <c>Log.Level</c> property
    /// to one of the <see cref="LogLevel"/> values which you want.
    /// </remarks>
    /// <value>
    /// A <see cref="Logger"/> that provides the logging functions.
    /// </value>
    public Logger Log {
      get {
        return _logger;
      }
    }

    /// <summary>
    /// Gets the port on which to listen for incoming requests.
    /// </summary>
    /// <value>
    /// An <see cref="int"/> that contains a port number.
    /// </value>
    public int Port {
      get {
        return _port;
      }
    }

    /// <summary>
    /// Gets or sets the document root path of server.
    /// </summary>
    /// <value>
    /// A <see cref="string"/> that contains the document root path of server.
    /// The default value is <c>./Public</c>.
    /// </value>
    public string RootPath {
      get {
        return _rootPath.IsNullOrEmpty ()
               ? (_rootPath = "./Public")
               : _rootPath;
      }

      set {
        if (_listening)
        {
          _logger.Error (
            "The value of RootPath property cannot be changed because the server has already been started.");
          return;
        }

        _rootPath = value;
      }
    }

    /// <summary>
    /// Gets the functions for the WebSocket services that the server provides.
    /// </summary>
    /// <value>
    /// A <see cref="WebSocketServiceHostManager"/> that manages the WebSocket services.
    /// </value>
    public WebSocketServiceHostManager WebSocketServices {
      get {
        return _serviceHosts;
      }
    }

    #endregion

    #region Public Events

    /// <summary>
    /// Occurs when the server receives an HTTP CONNECT request.
    /// </summary>
    public event EventHandler<HttpRequestEventArgs> OnConnect;

    /// <summary>
    /// Occurs when the server receives an HTTP DELETE request.
    /// </summary>
    public event EventHandler<HttpRequestEventArgs> OnDelete;

    /// <summary>
    /// Occurs when the server receives an HTTP GET request.
    /// </summary>
    public event EventHandler<HttpRequestEventArgs> OnGet;

    /// <summary>
    /// Occurs when the server receives an HTTP HEAD request.
    /// </summary>
    public event EventHandler<HttpRequestEventArgs> OnHead;

    /// <summary>
    /// Occurs when the server receives an HTTP OPTIONS request.
    /// </summary>
    public event EventHandler<HttpRequestEventArgs> OnOptions;

    /// <summary>
    /// Occurs when the server receives an HTTP PATCH request.
    /// </summary>
    public event EventHandler<HttpRequestEventArgs> OnPatch;

    /// <summary>
    /// Occurs when the server receives an HTTP POST request.
    /// </summary>
    public event EventHandler<HttpRequestEventArgs> OnPost;

    /// <summary>
    /// Occurs when the server receives an HTTP PUT request.
    /// </summary>
    public event EventHandler<HttpRequestEventArgs> OnPut;

    /// <summary>
    /// Occurs when the server receives an HTTP TRACE request.
    /// </summary>
    public event EventHandler<HttpRequestEventArgs> OnTrace;

    #endregion

    #region Private Methods

    private void abort ()
    {
      lock (_sync)
      {
        if (_state != ServerState.START)
          return;

        _state = ServerState.SHUTDOWN;
      }

      _listening = false;
      _serviceHosts.Stop (((ushort) CloseStatusCode.SERVER_ERROR).ToByteArray (ByteOrder.BIG));
      _listener.Abort ();

      _state = ServerState.STOP;
    }

    private string checkIfCertExists ()
    {
      return _secure &&
             !EndPointListener.CertificateExists (_port, _listener.CertificateFolderPath) &&
             Certificate == null
             ? "The secure connection requires a server certificate."
             : null;
    }

    private void init ()
    {
      _listener = new HttpListener ();
      _listening = false;
      _logger = new Logger ();
      _serviceHosts = new WebSocketServiceHostManager (_logger);
      _state = ServerState.READY;
      _sync = new object ();

      _windows = false;
      var os = Environment.OSVersion;
      if (os.Platform != PlatformID.Unix && os.Platform != PlatformID.MacOSX)
        _windows = true;

      var prefix = String.Format ("http{0}://*:{1}/", _secure ? "s" : "", _port);
      _listener.Prefixes.Add (prefix);
    }

    private void processHttpRequest (HttpListenerContext context)
    {
      var eventArgs = new HttpRequestEventArgs (context);
      var method = context.Request.HttpMethod;
      if (method == "GET" && OnGet != null)
      {
        OnGet (this, eventArgs);
        return;
      }

      if (method == "HEAD" && OnHead != null)
      {
        OnHead (this, eventArgs);
        return;
      }

      if (method == "POST" && OnPost != null)
      {
        OnPost (this, eventArgs);
        return;
      }

      if (method == "PUT" && OnPut != null)
      {
        OnPut (this, eventArgs);
        return;
      }

      if (method == "DELETE" && OnDelete != null)
      {
        OnDelete (this, eventArgs);
        return;
      }

      if (method == "OPTIONS" && OnOptions != null)
      {
        OnOptions (this, eventArgs);
        return;
      }

      if (method == "TRACE" && OnTrace != null)
      {
        OnTrace (this, eventArgs);
        return;
      }

      if (method == "CONNECT" && OnConnect != null)
      {
        OnConnect (this, eventArgs);
        return;
      }

      if (method == "PATCH" && OnPatch != null)
      {
        OnPatch (this, eventArgs);
        return;
      }

      context.Response.StatusCode = (int) HttpStatusCode.NotImplemented;
    }

    private bool processWebSocketRequest (HttpListenerContext context)
    {
      var wsContext = context.AcceptWebSocket ();

      IWebSocketServiceHost host;
      if (!_serviceHosts.TryGetServiceHostInternally (wsContext.Path, out host))
      {
        context.Response.StatusCode = (int) HttpStatusCode.NotImplemented;
        return false;
      }

      wsContext.WebSocket.Log = _logger;
      host.BindWebSocket (wsContext);

      return true;
    }

    private void processRequestAsync (HttpListenerContext context)
    {
      WaitCallback callback = state =>
      {
        try {
          if (context.Request.IsUpgradeTo ("websocket"))
          {
            if (processWebSocketRequest (context))
              return;
          }
          else
          {
            processHttpRequest (context);
          }

          context.Response.Close ();
        }
        catch (Exception ex) {
          _logger.Fatal (ex.ToString ());
          context.Connection.Close (true);
        }
      };

      ThreadPool.QueueUserWorkItem (callback);
    }

    private void receiveRequest ()
    {
      while (true)
      {
        try {
          processRequestAsync (_listener.GetContext ());
        }
        catch (HttpListenerException ex) {
          _logger.Warn (String.Format ("Receiving has been stopped.\nreason: {0}.", ex.Message));
          break;
        }
        catch (Exception ex) {
          _logger.Fatal (ex.ToString ());
          break;
        }
      }

      if (_listening)
        abort ();
    }

    private void startReceiveRequestThread ()
    {
      _receiveRequestThread = new Thread (new ThreadStart (receiveRequest)); 
      _receiveRequestThread.IsBackground = true;
      _receiveRequestThread.Start ();
    }

    private void stopListener ()
    {
      if (!_listening)
        return;

      _listening = false;
      _listener.Close ();
      _receiveRequestThread.Join (5 * 1000);
    }

    #endregion

    #region Public Methods

    /// <summary>
    /// Adds the specified typed WebSocket service with the specified <paramref name="servicePath"/>.
    /// </summary>
    /// <remarks>
    /// This method converts <paramref name="servicePath"/> to URL-decoded string and
    /// removes <c>'/'</c> from tail end of <paramref name="servicePath"/>.
    /// </remarks>
    /// <param name="servicePath">
    /// A <see cref="string"/> that contains an absolute path to the WebSocket service.
    /// </param>
    /// <typeparam name="T">
    /// The type of the WebSocket service. The T must inherit the <see cref="WebSocketService"/> class.
    /// </typeparam>
    public void AddWebSocketService<T> (string servicePath)
      where T : WebSocketService, new ()
    {
      var msg = servicePath.CheckIfValidServicePath ();
      if (msg != null)
      {
        _logger.Error (String.Format ("{0}\nservice path: {1}", msg, servicePath ?? ""));
        return;
      }

      var host = new WebSocketServiceHost<T> (_logger);
      host.Uri = servicePath.ToUri ();
      if (!KeepClean)
        host.KeepClean = false;

      _serviceHosts.Add (servicePath, host);
    }

    /// <summary>
    /// Gets the contents of the file with the specified <paramref name="path"/>.
    /// </summary>
    /// <returns>
    /// An array of <see cref="byte"/> that contains the contents of the file if exists;
    /// otherwise, <see langword="null"/>.
    /// </returns>
    /// <param name="path">
    /// A <see cref="string"/> that contains a virtual path to the file to get.
    /// </param>
    public byte[] GetFile (string path)
    {
      var filePath = RootPath + path;
      if (_windows)
        filePath = filePath.Replace ("/", "\\");

      return File.Exists (filePath)
             ? File.ReadAllBytes (filePath)
             : null;
    }

    /// <summary>
    /// Removes the WebSocket service with the specified <paramref name="servicePath"/>.
    /// </summary>
    /// <remarks>
    /// This method converts <paramref name="servicePath"/> to URL-decoded string and
    /// removes <c>'/'</c> from tail end of <paramref name="servicePath"/>.
    /// </remarks>
    /// <returns>
    /// <c>true</c> if the WebSocket service is successfully found and removed; otherwise, <c>false</c>.
    /// </returns>
    /// <param name="servicePath">
    /// A <see cref="string"/> that contains an absolute path to the WebSocket service to find.
    /// </param>
    public bool RemoveWebSocketService (string servicePath)
    {
      var msg = servicePath.CheckIfValidServicePath ();
      if (msg != null)
      {
        _logger.Error (String.Format ("{0}\nservice path: {1}", msg, servicePath ?? ""));
        return false;
      }

      return _serviceHosts.Remove (servicePath);
    }

    /// <summary>
    /// Starts to receive the HTTP requests.
    /// </summary>
    public void Start ()
    {
      lock (_sync)
      {
        var msg = _state.CheckIfStopped () ?? checkIfCertExists ();
        if (msg != null)
        {
          _logger.Error (String.Format ("{0}\nstate: {1}\nsecure: {2}", msg, _state, _secure));
          return;
        }

        _serviceHosts.Start ();
        _listener.Start ();
        startReceiveRequestThread ();
        _listening = true;

        _state = ServerState.START;
      }
    }

    /// <summary>
    /// Stops receiving the HTTP requests.
    /// </summary>
    public void Stop ()
    {
      lock (_sync)
      {
        var msg = _state.CheckIfStarted ();
        if (msg != null)
        {
          _logger.Error (String.Format ("{0}\nstate: {1}", msg, _state));
          return;
        }

        _state = ServerState.SHUTDOWN;
      }

      _serviceHosts.Stop ();
      stopListener ();

      _state = ServerState.STOP;
    }

    /// <summary>
    /// Stops receiving the HTTP requests with the specified <see cref="ushort"/> and
    /// <see cref="string"/> used to stop the WebSocket services.
    /// </summary>
    /// <param name="code">
    /// A <see cref="ushort"/> that contains a status code indicating the reason for stop.
    /// </param>
    /// <param name="reason">
    /// A <see cref="string"/> that contains the reason for stop.
    /// </param>
    public void Stop (ushort code, string reason)
    {
      byte [] data = null;
      lock (_sync)
      {
        var msg = _state.CheckIfStarted () ??
                  code.CheckIfValidCloseStatusCode () ??
                  (data = code.Append (reason)).CheckIfValidCloseData ();

        if (msg != null)
        {
          _logger.Error (String.Format ("{0}\nstate: {1}\ncode: {2}\nreason: {3}", msg, _state, code, reason));
          return;
        }

        _state = ServerState.SHUTDOWN;
      }

      _serviceHosts.Stop (data);
      stopListener ();

      _state = ServerState.STOP;
    }

    /// <summary>
    /// Stops receiving the HTTP requests with the specified <see cref="CloseStatusCode"/>
    /// and <see cref="string"/> used to stop the WebSocket services.
    /// </summary>
    /// <param name="code">
    /// One of the <see cref="CloseStatusCode"/> values that represent the status codes indicating
    /// the reasons for stop.
    /// </param>
    /// <param name="reason">
    /// A <see cref="string"/> that contains the reason for stop.
    /// </param>
    public void Stop (CloseStatusCode code, string reason)
    {
      byte [] data = null;
      lock (_sync)
      {
        var msg = _state.CheckIfStarted () ??
                  (data = ((ushort) code).Append (reason)).CheckIfValidCloseData ();

        if (msg != null)
        {
          _logger.Error (String.Format ("{0}\nstate: {1}\nreason: {2}", msg, _state, reason));
          return;
        }

        _state = ServerState.SHUTDOWN;
      }

      _serviceHosts.Stop (data);
      stopListener ();

      _state = ServerState.STOP;
    }

    #endregion
  }
}