var assert = require('assert');
var constants = require('constants');
var crypto = require('crypto');
var events = require('events');
var net = require('net');
var tls = require('tls');
var util = require('util');

var Timer = process.binding('timer_wrap').Timer;
var tls_wrap = process.binding('tls_wrap');

var debug = util.debuglog('tls');

function onhandshakestart() {
  debug('onhandshakestart');

  var self = this;
  var ssl = self.ssl;
  var now = Timer.now();

  assert(now >= ssl.lastHandshakeTime);

  if ((now - ssl.lastHandshakeTime) >= tls.CLIENT_RENEG_WINDOW * 1000) {
    ssl.handshakes = 0;
  }

  var first = (ssl.lastHandshakeTime === 0);
  ssl.lastHandshakeTime = now;
  if (first) return;

  if (++ssl.handshakes > tls.CLIENT_RENEG_LIMIT) {
    // Defer the error event to the next tick. We're being called from OpenSSL's
    // state machine and OpenSSL is not re-entrant. We cannot allow the user's
    // callback to destroy the connection right now, it would crash and burn.
    setImmediate(function() {
      var err = new Error('TLS session renegotiation attack detected.');
      self._tlsError(err);
    });
  }
}


function onhandshakedone() {
  // for future use
  debug('onhandshakedone');
  this._finishInit();
}


function onclienthello(hello) {
  var self = this,
      once = false;

  function callback(err, session) {
    if (once)
      return self.destroy(new Error('TLS session callback was called twice'));
    once = true;

    if (err)
      return self.destroy(err);

    self.ssl.loadSession(session);
  }

  if (hello.sessionId.length <= 0 ||
      this.server &&
      !this.server.emit('resumeSession', hello.sessionId, callback)) {
    callback(null, null);
  }
}


function onnewsession(key, session) {
  if (this.server)
    this.server.emit('newSession', key, session);
}


/**
 * Provides a wrap of socket stream to do encrypted communication.
 */

function TLSSocket(socket, options) {
  net.Socket.call(this, socket && {
    handle: socket._handle,
    allowHalfOpen: socket.allowHalfOpen,
    readable: socket.readable,
    writable: socket.writable
  });

  var self = this;

  this._tlsOptions = options;
  this._secureEstablished = false;
  this._controlReleased = false;
  this.ssl = null;
  this.servername = null;
  this.npnProtocol = null;
  this.authorized = false;
  this.authorizationError = null;

  if (!this._handle)
    this.once('connect', this._init.bind(this));
  else
    this._init();
}
util.inherits(TLSSocket, net.Socket);
exports.TLSSocket = TLSSocket;

TLSSocket.prototype._init = function() {
  assert(this._handle);

  // lib/net.js expect this value to be non-zero if write hasn't been flushed
  // immediately
  // TODO(indutny): rewise this solution, it might be 1 before handshake and
  // repersent real writeQueueSize during regular writes.
  this._handle.writeQueueSize = 1;

  var self = this;
  var options = this._tlsOptions;

  // Wrap socket's handle
  var credentials = options.credentials || crypto.createCredentials();
  this.ssl = tls_wrap.wrap(this._handle, credentials.context, options.isServer);
  this.server = options.server || null;

  // For clients, we will always have either a given ca list or be using
  // default one
  var requestCert = !!options.requestCert || !options.isServer,
      rejectUnauthorized = !!options.rejectUnauthorized;

  if (requestCert || rejectUnauthorized)
    this.ssl.setVerifyMode(requestCert, rejectUnauthorized);

  if (options.isServer) {
    this.ssl.onhandshakestart = onhandshakestart.bind(this);
    this.ssl.onhandshakedone = onhandshakedone.bind(this);
    this.ssl.onclienthello = onclienthello.bind(this);
    this.ssl.onnewsession = onnewsession.bind(this);
    this.ssl.lastHandshakeTime = 0;
    this.ssl.handshakes = 0;

    if (this.server &&
        (this.server.listeners('resumeSession').length > 0 ||
         this.server.listeners('newSession').length > 0)) {
      this.ssl.enableSessionCallbacks();
    }
  } else {
    this.ssl.onhandshakestart = function() {};
    this.ssl.onhandshakedone = this._finishInit.bind(this);
  }

  this.ssl.onerror = function(err) {
    // Destroy socket if error happened before handshake's finish
    if (!this._secureEstablished) {
      self._tlsError(err);
      self.destroy();
    } else if (options.isServer &&
               rejectUnauthorized &&
               /peer did not return a certificate/.test(err.message)) {
      // Ignore server's authorization errors
      self.destroy();
    } else {
      // Throw error
      self._tlsError(err);
    }
  };

  if (process.features.tls_sni &&
      options.isServer &&
      options.server &&
      options.SNICallback &&
      options.server._contexts.length) {
    this.ssl.onsniselect = options.SNICallback;
  }

  if (process.features.tls_npn && options.NPNProtocols)
    this.ssl.setNPNProtocols(options.NPNProtocols);
};

TLSSocket.prototype._tlsError = function(err) {
  this.emit('_tlsError', err);
  if (this._controlReleased)
    this.emit('error', err);
};

TLSSocket.prototype._finishInit = function() {
  if (process.features.tls_npn) {
    this.npnProtocol = this.ssl.getNegotiatedProtocol();
  }

  if (process.features.tls_sni && this._tlsOptions.isServer) {
    this.servername = this.ssl.getServername();
  }

  debug('secure established');
  this._secureEstablished = true;
  this.emit('secure');
};

TLSSocket.prototype._start = function() {
  this.ssl.start();
};

TLSSocket.prototype.setServername = function(name) {
  this.ssl.setServername(name);
};

TLSSocket.prototype.setSession = function(session) {
  if (typeof session === 'string')
    session = new Buffer(session, 'binary');
  this.ssl.setSession(session);
};

TLSSocket.prototype.getPeerCertificate = function() {
  if (this.ssl) {
    var c = this.ssl.getPeerCertificate();

    if (c) {
      if (c.issuer) c.issuer = tls.parseCertString(c.issuer);
      if (c.subject) c.subject = tls.parseCertString(c.subject);
      return c;
    }
  }

  return null;
};

TLSSocket.prototype.getSession = function() {
  if (this.ssl) {
    return this.ssl.getSession();
  }

  return null;
};

TLSSocket.prototype.isSessionReused = function() {
  if (this.ssl) {
    return this.ssl.isSessionReused();
  }

  return null;
};

TLSSocket.prototype.getCipher = function(err) {
  if (this.ssl) {
    return this.ssl.getCurrentCipher();
  } else {
    return null;
  }
};

// TODO: support anonymous (nocert) and PSK


// AUTHENTICATION MODES
//
// There are several levels of authentication that TLS/SSL supports.
// Read more about this in "man SSL_set_verify".
//
// 1. The server sends a certificate to the client but does not request a
// cert from the client. This is common for most HTTPS servers. The browser
// can verify the identity of the server, but the server does not know who
// the client is. Authenticating the client is usually done over HTTP using
// login boxes and cookies and stuff.
//
// 2. The server sends a cert to the client and requests that the client
// also send it a cert. The client knows who the server is and the server is
// requesting the client also identify themselves. There are several
// outcomes:
//
//   A) verifyError returns null meaning the client's certificate is signed
//   by one of the server's CAs. The server know's the client idenity now
//   and the client is authorized.
//
//   B) For some reason the client's certificate is not acceptable -
//   verifyError returns a string indicating the problem. The server can
//   either (i) reject the client or (ii) allow the client to connect as an
//   unauthorized connection.
//
// The mode is controlled by two boolean variables.
//
// requestCert
//   If true the server requests a certificate from client connections. For
//   the common HTTPS case, users will want this to be false, which is what
//   it defaults to.
//
// rejectUnauthorized
//   If true clients whose certificates are invalid for any reason will not
//   be allowed to make connections. If false, they will simply be marked as
//   unauthorized but secure communication will continue. By default this is
//   true.
//
//
//
// Options:
// - requestCert. Send verify request. Default to false.
// - rejectUnauthorized. Boolean, default to true.
// - key. string.
// - cert: string.
// - ca: string or array of strings.
// - sessionTimeout: integer.
//
// emit 'secureConnection'
//   function (tlsSocket) { }
//
//   "UNABLE_TO_GET_ISSUER_CERT", "UNABLE_TO_GET_CRL",
//   "UNABLE_TO_DECRYPT_CERT_SIGNATURE", "UNABLE_TO_DECRYPT_CRL_SIGNATURE",
//   "UNABLE_TO_DECODE_ISSUER_PUBLIC_KEY", "CERT_SIGNATURE_FAILURE",
//   "CRL_SIGNATURE_FAILURE", "CERT_NOT_YET_VALID" "CERT_HAS_EXPIRED",
//   "CRL_NOT_YET_VALID", "CRL_HAS_EXPIRED" "ERROR_IN_CERT_NOT_BEFORE_FIELD",
//   "ERROR_IN_CERT_NOT_AFTER_FIELD", "ERROR_IN_CRL_LAST_UPDATE_FIELD",
//   "ERROR_IN_CRL_NEXT_UPDATE_FIELD", "OUT_OF_MEM",
//   "DEPTH_ZERO_SELF_SIGNED_CERT", "SELF_SIGNED_CERT_IN_CHAIN",
//   "UNABLE_TO_GET_ISSUER_CERT_LOCALLY", "UNABLE_TO_VERIFY_LEAF_SIGNATURE",
//   "CERT_CHAIN_TOO_LONG", "CERT_REVOKED" "INVALID_CA",
//   "PATH_LENGTH_EXCEEDED", "INVALID_PURPOSE" "CERT_UNTRUSTED",
//   "CERT_REJECTED"
//
function Server(/* [options], listener */) {
  var options, listener;
  if (typeof arguments[0] == 'object') {
    options = arguments[0];
    listener = arguments[1];
  } else if (typeof arguments[0] == 'function') {
    options = {};
    listener = arguments[0];
  }

  if (!(this instanceof Server)) return new Server(options, listener);

  this._contexts = [];

  var self = this;

  // Handle option defaults:
  this.setOptions(options);

  if (!self.pfx && (!self.cert || !self.key)) {
    throw new Error('Missing PFX or certificate + private key.');
  }

  var sharedCreds = crypto.createCredentials({
    pfx: self.pfx,
    key: self.key,
    passphrase: self.passphrase,
    cert: self.cert,
    ca: self.ca,
    ciphers: self.ciphers || tls.DEFAULT_CIPHERS,
    secureProtocol: self.secureProtocol,
    secureOptions: self.secureOptions,
    crl: self.crl,
    sessionIdContext: self.sessionIdContext
  });

  var timeout = options.handshakeTimeout || (120 * 1000);

  if (typeof timeout !== 'number') {
    throw new TypeError('handshakeTimeout must be a number');
  }

  if (self.sessionTimeout) {
    sharedCreds.context.setSessionTimeout(self.sessionTimeout);
  }

  // constructor call
  net.Server.call(this, function(raw_socket) {
    var socket = new TLSSocket(raw_socket, {
      credentials: sharedCreds,
      isServer: true,
      server: self,
      requestCert: self.requestCert,
      rejectUnauthorized: self.rejectUnauthorized,
      NPNProtocols: self.NPNProtocols,
      SNICallback: self.SNICallback
    });

    function listener() {
      socket._tlsError(new Error('TLS handshake timeout'));
    }

    if (timeout > 0) {
      socket.setTimeout(timeout, listener);
    }

    socket.once('secure', function() {
      socket.setTimeout(0, listener);

      if (self.requestCert) {
        var verifyError = socket.ssl.verifyError();
        if (verifyError) {
          socket.authorizationError = verifyError.message;

          if (self.rejectUnauthorized)
            socket.destroy();
        } else {
          socket.authorized = true;
        }
      }

      if (!socket.destroyed) {
        socket._controlReleased = true;
        self.emit('secureConnection', socket);
      }
    });

    socket.on('_tlsError', function(err) {
      if (!socket._controlReleased)
        self.emit('clientError', err, socket);
    });
  });

  if (listener) {
    this.on('secureConnection', listener);
  }
}

util.inherits(Server, net.Server);
exports.Server = Server;
exports.createServer = function(options, listener) {
  return new Server(options, listener);
};


Server.prototype.setOptions = function(options) {
  if (typeof options.requestCert == 'boolean') {
    this.requestCert = options.requestCert;
  } else {
    this.requestCert = false;
  }

  if (typeof options.rejectUnauthorized == 'boolean') {
    this.rejectUnauthorized = options.rejectUnauthorized;
  } else {
    this.rejectUnauthorized = false;
  }

  if (options.pfx) this.pfx = options.pfx;
  if (options.key) this.key = options.key;
  if (options.passphrase) this.passphrase = options.passphrase;
  if (options.cert) this.cert = options.cert;
  if (options.ca) this.ca = options.ca;
  if (options.secureProtocol) this.secureProtocol = options.secureProtocol;
  if (options.crl) this.crl = options.crl;
  if (options.ciphers) this.ciphers = options.ciphers;
  if (options.sessionTimeout) this.sessionTimeout = options.sessionTimeout;
  var secureOptions = options.secureOptions || 0;
  if (options.honorCipherOrder) {
    secureOptions |= constants.SSL_OP_CIPHER_SERVER_PREFERENCE;
  }
  if (secureOptions) this.secureOptions = secureOptions;
  if (options.NPNProtocols) tls.convertNPNProtocols(options.NPNProtocols, this);
  if (options.SNICallback) {
    this.SNICallback = options.SNICallback;
  } else {
    this.SNICallback = this.SNICallback.bind(this);
  }
  if (options.sessionIdContext) {
    this.sessionIdContext = options.sessionIdContext;
  } else if (this.requestCert) {
    this.sessionIdContext = crypto.createHash('md5')
                                  .update(process.argv.join(' '))
                                  .digest('hex');
  }
};

// SNI Contexts High-Level API
Server.prototype.addContext = function(servername, credentials) {
  if (!servername) {
    throw 'Servername is required parameter for Server.addContext';
  }

  var re = new RegExp('^' +
                      servername.replace(/([\.^$+?\-\\[\]{}])/g, '\\$1')
                                .replace(/\*/g, '.*') +
                      '$');
  this._contexts.push([re, crypto.createCredentials(credentials).context]);
};

Server.prototype.SNICallback = function(servername) {
  var ctx;

  this._contexts.some(function(elem) {
    if (servername.match(elem[0]) !== null) {
      ctx = elem[1];
      return true;
    }
  });

  return ctx;
};


// Target API:
//
//  var s = tls.connect({port: 8000, host: "google.com"}, function() {
//    if (!s.authorized) {
//      s.destroy();
//      return;
//    }
//
//    // s.socket;
//
//    s.end("hello world\n");
//  });
//
//
function normalizeConnectArgs(listArgs) {
  var args = net._normalizeConnectArgs(listArgs);
  var options = args[0];
  var cb = args[1];

  if (typeof listArgs[1] === 'object') {
    options = util._extend(options, listArgs[1]);
  } else if (typeof listArgs[2] === 'object') {
    options = util._extend(options, listArgs[2]);
  }

  return (cb) ? [options, cb] : [options];
}

exports.connect = function(/* [port, host], options, cb */) {
  var args = normalizeConnectArgs(arguments);
  var options = args[0];
  var cb = args[1];

  var defaults = {
    rejectUnauthorized: '0' !== process.env.NODE_TLS_REJECT_UNAUTHORIZED
  };
  options = util._extend(defaults, options || {});

  var hostname = options.servername || options.host || 'localhost',
      NPN = {};
  tls.convertNPNProtocols(options.NPNProtocols, NPN);

  var socket = new TLSSocket(options.socket, {
    credentials: crypto.createCredentials(options),
    isServer: false,
    requestCert: true,
    rejectUnauthorized: options.rejectUnauthorized,
    NPNProtocols: NPN.NPNProtocols
  });

  function onHandle() {
    socket._controlReleased = true;

    if (options.session)
      socket.setSession(options.session);

    if (options.servername)
      socket.setServername(options.servername);

    socket._start();
    socket.on('secure', function() {
      var verifyError = socket.ssl.verifyError();

      // Verify that server's identity matches it's certificate's names
      if (!verifyError) {
        var validCert = tls.checkServerIdentity(hostname,
                                                socket.getPeerCertificate());
        if (!validCert) {
          verifyError = new Error('Hostname/IP doesn\'t match certificate\'s ' +
                                  'altnames');
        }
      }

      if (verifyError) {
        socket.authorizationError = verifyError.message;

        if (options.rejectUnauthorized) {
          socket.emit('error', verifyError);
          socket.destroy();
          return;
        } else {
          socket.emit('secureConnect');
        }
      } else {
        socket.authorized = true;
        socket.emit('secureConnect');
      }

      // Uncork incoming data
      socket.removeListener('end', onHangUp);
    });

    function onHangUp() {
      // NOTE: This logic is shared with _http_client.js
      if (!socket._hadError) {
        socket._hadError = true;
        var error = new Error('socket hang up');
        error.code = 'ECONNRESET';
        socket.destroy();
        socket.emit('error', error);
      }
    }
    socket.once('end', onHangUp);
  }
  if (socket._handle)
    onHandle();
  else
    socket.once('connect', onHandle);

  if (cb)
    socket.once('secureConnect', cb);

  if (!options.socket) {
    var connect_opt = (options.path && !options.port) ? {path: options.path} : {
      port: options.port,
      host: options.host,
      localAddress: options.localAddress
    };
    socket.connect(connect_opt);
  }

  return socket;
};