var WebSocketServer = require('ws').Server;

/*!
 * ws: a node.js websocket client
 * Copyright(c) 2011 Einar Otto Stangvik <einaros@gmail.com>
 * MIT Licensed
 */

var http = require('http');
var crypto = require('crypto');
var WebSocket = require('./ws/WebSocket');
var Extensions = require('./ws/Extensions');
var PerMessageDeflate = require('./ws/PerMessageDeflate');
var url = require('url');

/**
 * Handle a HTTP Upgrade request.
 *
 * @api public
 */

WebSocketServer.prototype.handleUpgrade = function(req, socket, upgradeHead, cb) {
  // check for wrong path
  if (this.options.path) {
    var u = url.parse(req.url);
    if (u && u.pathname !== this.options.path) return;
  }

  if (typeof req.headers.upgrade === 'undefined' || req.headers.upgrade.toLowerCase() !== 'websocket') {
    abortConnection(socket, 400, 'Bad Request');
    return;
  }

  if (req.headers['sec-websocket-key1']) handleHixieUpgrade.apply(this, arguments);
  else handleHybiUpgrade.apply(this, arguments);
};

/**
 * Entirely private apis,
 * which may or may not be bound to a sepcific WebSocket instance.
 */

function handleHybiUpgrade(req, socket, upgradeHead, cb) {
  // handle premature socket errors
  var errorHandler = function() {
    try { socket.destroy(); } catch (e) {}
  };
  socket.on('error', errorHandler);

  // verify key presence
  if (!req.headers['sec-websocket-key']) {
    abortConnection(socket, 400, 'Bad Request');
    return;
  }

  // verify version
  var version = parseInt(req.headers['sec-websocket-version']);
  if ([8, 13].indexOf(version) === -1) {
    abortConnection(socket, 400, 'Bad Request');
    return;
  }

  // verify protocol
  var protocols = req.headers['sec-websocket-protocol'];

  // verify client
  var origin = version < 13 ?
    req.headers['sec-websocket-origin'] :
    req.headers['origin'];

  // handle extensions offer
  var extensionsOffer = Extensions.parse(req.headers['sec-websocket-extensions']);

  // handler to call when the connection sequence completes
  var self = this;
  var completeHybiUpgrade2 = function(protocol) {

    // calc key
    var key = req.headers['sec-websocket-key'];
    var shasum = crypto.createHash('sha1');
    shasum.update(key + '258EAFA5-E914-47DA-95CA-C5AB0DC85B11');
    key = shasum.digest('base64');

    var headers = [
      'HTTP/1.1 101 Switching Protocols'
      , 'Upgrade: websocket'
      , 'Connection: Upgrade'
      , 'Sec-WebSocket-Accept: ' + key
    ];

    if (typeof protocol != 'undefined') {
      headers.push('Sec-WebSocket-Protocol: ' + protocol);
    }

    var extensions = {};
    try {
      extensions = acceptExtensions.call(self, extensionsOffer);
    } catch (err) {
      abortConnection(socket, 400, 'Bad Request');
      return;
    }

    if (Object.keys(extensions).length) {
      var serverExtensions = {};
      Object.keys(extensions).forEach(function(token) {
        serverExtensions[token] = [extensions[token].params];
      });
      headers.push('Sec-WebSocket-Extensions: ' + Extensions.format(serverExtensions));
    }

    // allows external modification/inspection of handshake headers
    self.emit('headers', headers);

    socket.setTimeout(0);
    socket.setNoDelay(true);
    try {
      socket.write(headers.concat('', '').join('\r\n'));
    }
    catch (e) {
      // if the upgrade write fails, shut the connection down hard
      try { socket.destroy(); } catch (e) {}
      return;
    }

    var client = new WebSocket([req, socket, upgradeHead], {
      protocolVersion: version,
      protocol: protocol,
      extensions: extensions,
      maxPayload: self.options.maxPayload
    });

    if (self.options.clientTracking) {
      self.clients.push(client);
      client.on('close', function() {
        var index = self.clients.indexOf(client);
        if (index != -1) {
          self.clients.splice(index, 1);
        }
      });
    }

    // signal upgrade complete
    socket.removeListener('error', errorHandler);
    cb(client);
  };

  // optionally call external protocol selection handler before
  // calling completeHybiUpgrade2
  var completeHybiUpgrade1 = function() {
    // choose from the sub-protocols
    if (typeof self.options.handleProtocols == 'function') {
      var protList = (protocols || '').split(/, */);
      var callbackCalled = false;
      self.options.handleProtocols(protList, function(result, protocol) {
        callbackCalled = true;
        if (!result) abortConnection(socket, 401, 'Unauthorized');
        else completeHybiUpgrade2(protocol);
      });
      if (!callbackCalled) {
            // the handleProtocols handler never called our callback
        abortConnection(socket, 501, 'Could not process protocols');
      }
      return;
    } else {
      if (typeof protocols !== 'undefined') {
        completeHybiUpgrade2(protocols.split(/, */)[0]);
      }
      else {
        completeHybiUpgrade2();
      }
    }
  };

  // optionally call external client verification handler
  if (typeof this.options.verifyClient == 'function') {
    var info = {
      origin: origin,
      secure: typeof req.connection.authorized !== 'undefined' || typeof req.connection.encrypted !== 'undefined',
      req: req
    };
    if (this.options.verifyClient.length == 2) {
      this.options.verifyClient(info, function(result, code, name) {
        if (typeof code === 'undefined') code = 401;
        if (typeof name === 'undefined') name = http.STATUS_CODES[code];

        if (!result) abortConnection(socket, code, name);
        else completeHybiUpgrade1();
      });
      return;
    }
    else if (!this.options.verifyClient(info)) {
      abortConnection(socket, 401, 'Unauthorized');
      return;
    }
  }

  completeHybiUpgrade1();
}

function handleHixieUpgrade(req, socket, upgradeHead, cb) {
  // handle premature socket errors
  var errorHandler = function() {
    try { socket.destroy(); } catch (e) {}
  };
  socket.on('error', errorHandler);

  // bail if options prevent hixie
  if (this.options.disableHixie) {
    abortConnection(socket, 401, 'Hixie support disabled');
    return;
  }

  // verify key presence
  if (!req.headers['sec-websocket-key2']) {
    abortConnection(socket, 400, 'Bad Request');
    return;
  }

  var origin = req.headers['origin']
    , self = this;

  // setup handshake completion to run after client has been verified
  var onClientVerified = function() {
    var wshost;
    if (!req.headers['x-forwarded-host'])
      wshost = req.headers.host;
    else
        wshost = req.headers['x-forwarded-host'];
    var location = ((req.headers['x-forwarded-proto'] === 'https' || socket.encrypted) ? 'wss' : 'ws') + '://' + wshost + req.url
      , protocol = req.headers['sec-websocket-protocol'];

    // build the response header and return a Buffer
    var buildResponseHeader = function() {
      var headers = [
        'HTTP/1.1 101 Switching Protocols'
        , 'Upgrade: WebSocket'
        , 'Connection: Upgrade'
        , 'Sec-WebSocket-Location: ' + location
      ];
      if (typeof protocol != 'undefined') headers.push('Sec-WebSocket-Protocol: ' + protocol);
      if (typeof origin != 'undefined') headers.push('Sec-WebSocket-Origin: ' + origin);

      return new Buffer(headers.concat('', '').join('\r\n'));
    };

    // send handshake response before receiving the nonce
    var handshakeResponse = function() {

      socket.setTimeout(0);
      socket.setNoDelay(true);

      var headerBuffer = buildResponseHeader();

      try {
        socket.write(headerBuffer, 'binary', function(err) {
          // remove listener if there was an error
          if (err) socket.removeListener('data', handler);
          return;
        });
      } catch (e) {
        try { socket.destroy(); } catch (e) {}
        return;
      }
    };

    // handshake completion code to run once nonce has been successfully retrieved
    var completeHandshake = function(nonce, rest, headerBuffer) {
      // calculate key
      var k1 = req.headers['sec-websocket-key1']
        , k2 = req.headers['sec-websocket-key2']
        , md5 = crypto.createHash('md5');

      [k1, k2].forEach(function (k) {
        var n = parseInt(k.replace(/[^\d]/g, ''))
          , spaces = k.replace(/[^ ]/g, '').length;
        if (spaces === 0 || n % spaces !== 0){
          abortConnection(socket, 400, 'Bad Request');
          return;
        }
        n /= spaces;
        md5.update(String.fromCharCode(
          n >> 24 & 0xFF,
          n >> 16 & 0xFF,
          n >> 8  & 0xFF,
          n       & 0xFF));
      });
      md5.update(nonce.toString('binary'));

      socket.setTimeout(0);
      socket.setNoDelay(true);

      try {
        var hashBuffer = new Buffer(md5.digest('binary'), 'binary');
        var handshakeBuffer = new Buffer(headerBuffer.length + hashBuffer.length);
        headerBuffer.copy(handshakeBuffer, 0);
        hashBuffer.copy(handshakeBuffer, headerBuffer.length);

        // do a single write, which - upon success - causes a new client websocket to be setup
        socket.write(handshakeBuffer, 'binary', function(err) {
          if (err) return; // do not create client if an error happens
          var client = new WebSocket([req, socket, rest], {
            protocolVersion: 'hixie-76',
            protocol: protocol
          });
          if (self.options.clientTracking) {
            self.clients.push(client);
            client.on('close', function() {
              var index = self.clients.indexOf(client);
              if (index != -1) {
                self.clients.splice(index, 1);
              }
            });
          }

          // signal upgrade complete
          socket.removeListener('error', errorHandler);
          cb(client);
        });
      }
      catch (e) {
        try { socket.destroy(); } catch (e) {}
        return;
      }
    };

    // retrieve nonce
    var nonce;
    var rest = null;
    var nonceLength = 8;
    if (upgradeHead && upgradeHead.length >= nonceLength) {
      nonce = upgradeHead.slice(0, nonceLength);
      rest = upgradeHead.length > nonceLength ? upgradeHead.slice(nonceLength) : null;
      completeHandshake.call(self, nonce, rest, buildResponseHeader());
    } else {
      // nonce not present in upgradeHead
      nonce = new Buffer(nonceLength);
      upgradeHead.copy(nonce, 0);
      var received = upgradeHead.length;
      var handler = function (data) {
        var toRead = Math.min(data.length, nonceLength - received);
        if (toRead === 0) return;
        data.copy(nonce, received, 0, toRead);
        received += toRead;
        if (received == nonceLength) {
          socket.removeListener('data', handler);
          if (toRead < data.length) rest = data.slice(toRead);

          // complete the handshake but send empty buffer for headers since they have already been sent
          completeHandshake.call(self, nonce, rest, new Buffer(0));
        }
      };

      // handle additional data as we receive it
      socket.on('data', handler);

      // send header response before we have the nonce to fix haproxy buffering
      handshakeResponse();
    }
  };

  // verify client
  if (typeof this.options.verifyClient == 'function') {
    var info = {
      origin: origin,
      secure: typeof req.connection.authorized !== 'undefined' || typeof req.connection.encrypted !== 'undefined',
      req: req
    };
    if (this.options.verifyClient.length == 2) {
      this.options.verifyClient(info, function(result, code, name) {
        if (typeof code === 'undefined') code = 401;
        if (typeof name === 'undefined') name = http.STATUS_CODES[code];

        if (!result) abortConnection(socket, code, name);
        else onClientVerified.apply(self);
      });
      return;
    } else if (!this.options.verifyClient(info)) {
      abortConnection(socket, 401, 'Unauthorized');
      return;
    }
  }

  // no client verification required
  onClientVerified();
}

function acceptExtensions(offer) {
  var extensions = {};
  var options = this.options.perMessageDeflate;
  var maxPayload = this.options.maxPayload;
  if (options && offer[PerMessageDeflate.extensionName]) {
    var perMessageDeflate = new PerMessageDeflate(options !== true ? options : {}, true, maxPayload);
    perMessageDeflate.accept(offer[PerMessageDeflate.extensionName]);
    extensions[PerMessageDeflate.extensionName] = perMessageDeflate;
  }
  return extensions;
}

function abortConnection(socket, code, name) {
  try {
    var response = [
      'HTTP/1.1 ' + code + ' ' + name,
      'Content-type: text/html'
    ];
    socket.write(response.concat('', '').join('\r\n'));
  }
  catch (e) { /* ignore errors - we've aborted this connection */ }
  finally {
    // ensure that an early aborted connection is shut down completely
    try { socket.destroy(); } catch (e) {}
  }
}

module.exports = WebSocketServer;