/*!
 * Engine.IO v6.4.0
 * (c) 2014-2023 Guillermo Rauch
 * Released under the MIT License.
 */
(function (global, factory) {
  typeof exports === 'object' && typeof module !== 'undefined' ? module.exports = factory() :
  typeof define === 'function' && define.amd ? define(factory) :
  (global = typeof globalThis !== 'undefined' ? globalThis : global || self, global.eio = factory());
})(this, (function () { 'use strict';

  function _typeof(obj) {
    "@babel/helpers - typeof";

    if (typeof Symbol === "function" && typeof Symbol.iterator === "symbol") {
      _typeof = function (obj) {
        return typeof obj;
      };
    } else {
      _typeof = function (obj) {
        return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj;
      };
    }

    return _typeof(obj);
  }

  function _classCallCheck(instance, Constructor) {
    if (!(instance instanceof Constructor)) {
      throw new TypeError("Cannot call a class as a function");
    }
  }

  function _defineProperties(target, props) {
    for (var i = 0; i < props.length; i++) {
      var descriptor = props[i];
      descriptor.enumerable = descriptor.enumerable || false;
      descriptor.configurable = true;
      if ("value" in descriptor) descriptor.writable = true;
      Object.defineProperty(target, descriptor.key, descriptor);
    }
  }

  function _createClass(Constructor, protoProps, staticProps) {
    if (protoProps) _defineProperties(Constructor.prototype, protoProps);
    if (staticProps) _defineProperties(Constructor, staticProps);
    return Constructor;
  }

  function _extends() {
    _extends = Object.assign || function (target) {
      for (var i = 1; i < arguments.length; i++) {
        var source = arguments[i];

        for (var key in source) {
          if (Object.prototype.hasOwnProperty.call(source, key)) {
            target[key] = source[key];
          }
        }
      }

      return target;
    };

    return _extends.apply(this, arguments);
  }

  function _inherits(subClass, superClass) {
    if (typeof superClass !== "function" && superClass !== null) {
      throw new TypeError("Super expression must either be null or a function");
    }

    subClass.prototype = Object.create(superClass && superClass.prototype, {
      constructor: {
        value: subClass,
        writable: true,
        configurable: true
      }
    });
    if (superClass) _setPrototypeOf(subClass, superClass);
  }

  function _getPrototypeOf(o) {
    _getPrototypeOf = Object.setPrototypeOf ? Object.getPrototypeOf : function _getPrototypeOf(o) {
      return o.__proto__ || Object.getPrototypeOf(o);
    };
    return _getPrototypeOf(o);
  }

  function _setPrototypeOf(o, p) {
    _setPrototypeOf = Object.setPrototypeOf || function _setPrototypeOf(o, p) {
      o.__proto__ = p;
      return o;
    };

    return _setPrototypeOf(o, p);
  }

  function _isNativeReflectConstruct() {
    if (typeof Reflect === "undefined" || !Reflect.construct) return false;
    if (Reflect.construct.sham) return false;
    if (typeof Proxy === "function") return true;

    try {
      Date.prototype.toString.call(Reflect.construct(Date, [], function () {}));
      return true;
    } catch (e) {
      return false;
    }
  }

  function _construct(Parent, args, Class) {
    if (_isNativeReflectConstruct()) {
      _construct = Reflect.construct;
    } else {
      _construct = function _construct(Parent, args, Class) {
        var a = [null];
        a.push.apply(a, args);
        var Constructor = Function.bind.apply(Parent, a);
        var instance = new Constructor();
        if (Class) _setPrototypeOf(instance, Class.prototype);
        return instance;
      };
    }

    return _construct.apply(null, arguments);
  }

  function _isNativeFunction(fn) {
    return Function.toString.call(fn).indexOf("[native code]") !== -1;
  }

  function _wrapNativeSuper(Class) {
    var _cache = typeof Map === "function" ? new Map() : undefined;

    _wrapNativeSuper = function _wrapNativeSuper(Class) {
      if (Class === null || !_isNativeFunction(Class)) return Class;

      if (typeof Class !== "function") {
        throw new TypeError("Super expression must either be null or a function");
      }

      if (typeof _cache !== "undefined") {
        if (_cache.has(Class)) return _cache.get(Class);

        _cache.set(Class, Wrapper);
      }

      function Wrapper() {
        return _construct(Class, arguments, _getPrototypeOf(this).constructor);
      }

      Wrapper.prototype = Object.create(Class.prototype, {
        constructor: {
          value: Wrapper,
          enumerable: false,
          writable: true,
          configurable: true
        }
      });
      return _setPrototypeOf(Wrapper, Class);
    };

    return _wrapNativeSuper(Class);
  }

  function _assertThisInitialized(self) {
    if (self === void 0) {
      throw new ReferenceError("this hasn't been initialised - super() hasn't been called");
    }

    return self;
  }

  function _possibleConstructorReturn(self, call) {
    if (call && (typeof call === "object" || typeof call === "function")) {
      return call;
    }

    return _assertThisInitialized(self);
  }

  function _createSuper(Derived) {
    var hasNativeReflectConstruct = _isNativeReflectConstruct();

    return function _createSuperInternal() {
      var Super = _getPrototypeOf(Derived),
          result;

      if (hasNativeReflectConstruct) {
        var NewTarget = _getPrototypeOf(this).constructor;

        result = Reflect.construct(Super, arguments, NewTarget);
      } else {
        result = Super.apply(this, arguments);
      }

      return _possibleConstructorReturn(this, result);
    };
  }

  function _superPropBase(object, property) {
    while (!Object.prototype.hasOwnProperty.call(object, property)) {
      object = _getPrototypeOf(object);
      if (object === null) break;
    }

    return object;
  }

  function _get(target, property, receiver) {
    if (typeof Reflect !== "undefined" && Reflect.get) {
      _get = Reflect.get;
    } else {
      _get = function _get(target, property, receiver) {
        var base = _superPropBase(target, property);

        if (!base) return;
        var desc = Object.getOwnPropertyDescriptor(base, property);

        if (desc.get) {
          return desc.get.call(receiver);
        }

        return desc.value;
      };
    }

    return _get(target, property, receiver || target);
  }

  var PACKET_TYPES = Object.create(null); // no Map = no polyfill

  PACKET_TYPES["open"] = "0";
  PACKET_TYPES["close"] = "1";
  PACKET_TYPES["ping"] = "2";
  PACKET_TYPES["pong"] = "3";
  PACKET_TYPES["message"] = "4";
  PACKET_TYPES["upgrade"] = "5";
  PACKET_TYPES["noop"] = "6";
  var PACKET_TYPES_REVERSE = Object.create(null);
  Object.keys(PACKET_TYPES).forEach(function (key) {
    PACKET_TYPES_REVERSE[PACKET_TYPES[key]] = key;
  });
  var ERROR_PACKET = {
    type: "error",
    data: "parser error"
  };

  var withNativeBlob = typeof Blob === "function" || typeof Blob !== "undefined" && Object.prototype.toString.call(Blob) === "[object BlobConstructor]";
  var withNativeArrayBuffer$1 = typeof ArrayBuffer === "function"; // ArrayBuffer.isView method is not defined in IE10

  var isView = function isView(obj) {
    return typeof ArrayBuffer.isView === "function" ? ArrayBuffer.isView(obj) : obj && obj.buffer instanceof ArrayBuffer;
  };

  var encodePacket = function encodePacket(_ref, supportsBinary, callback) {
    var type = _ref.type,
        data = _ref.data;

    if (withNativeBlob && data instanceof Blob) {
      if (supportsBinary) {
        return callback(data);
      } else {
        return encodeBlobAsBase64(data, callback);
      }
    } else if (withNativeArrayBuffer$1 && (data instanceof ArrayBuffer || isView(data))) {
      if (supportsBinary) {
        return callback(data);
      } else {
        return encodeBlobAsBase64(new Blob([data]), callback);
      }
    } // plain string


    return callback(PACKET_TYPES[type] + (data || ""));
  };

  var encodeBlobAsBase64 = function encodeBlobAsBase64(data, callback) {
    var fileReader = new FileReader();

    fileReader.onload = function () {
      var content = fileReader.result.split(",")[1];
      callback("b" + content);
    };

    return fileReader.readAsDataURL(data);
  };

  /*
   * base64-arraybuffer 1.0.1 <https://github.com/niklasvh/base64-arraybuffer>
   * Copyright (c) 2022 Niklas von Hertzen <https://hertzen.com>
   * Released under MIT License
   */
  var chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'; // Use a lookup table to find the index.

  var lookup = typeof Uint8Array === 'undefined' ? [] : new Uint8Array(256);

  for (var i$1 = 0; i$1 < chars.length; i$1++) {
    lookup[chars.charCodeAt(i$1)] = i$1;
  }

  var decode$1 = function decode(base64) {
    var bufferLength = base64.length * 0.75,
        len = base64.length,
        i,
        p = 0,
        encoded1,
        encoded2,
        encoded3,
        encoded4;

    if (base64[base64.length - 1] === '=') {
      bufferLength--;

      if (base64[base64.length - 2] === '=') {
        bufferLength--;
      }
    }

    var arraybuffer = new ArrayBuffer(bufferLength),
        bytes = new Uint8Array(arraybuffer);

    for (i = 0; i < len; i += 4) {
      encoded1 = lookup[base64.charCodeAt(i)];
      encoded2 = lookup[base64.charCodeAt(i + 1)];
      encoded3 = lookup[base64.charCodeAt(i + 2)];
      encoded4 = lookup[base64.charCodeAt(i + 3)];
      bytes[p++] = encoded1 << 2 | encoded2 >> 4;
      bytes[p++] = (encoded2 & 15) << 4 | encoded3 >> 2;
      bytes[p++] = (encoded3 & 3) << 6 | encoded4 & 63;
    }

    return arraybuffer;
  };

  var withNativeArrayBuffer = typeof ArrayBuffer === "function";

  var decodePacket = function decodePacket(encodedPacket, binaryType) {
    if (typeof encodedPacket !== "string") {
      return {
        type: "message",
        data: mapBinary(encodedPacket, binaryType)
      };
    }

    var type = encodedPacket.charAt(0);

    if (type === "b") {
      return {
        type: "message",
        data: decodeBase64Packet(encodedPacket.substring(1), binaryType)
      };
    }

    var packetType = PACKET_TYPES_REVERSE[type];

    if (!packetType) {
      return ERROR_PACKET;
    }

    return encodedPacket.length > 1 ? {
      type: PACKET_TYPES_REVERSE[type],
      data: encodedPacket.substring(1)
    } : {
      type: PACKET_TYPES_REVERSE[type]
    };
  };

  var decodeBase64Packet = function decodeBase64Packet(data, binaryType) {
    if (withNativeArrayBuffer) {
      var decoded = decode$1(data);
      return mapBinary(decoded, binaryType);
    } else {
      return {
        base64: true,
        data: data
      }; // fallback for old browsers
    }
  };

  var mapBinary = function mapBinary(data, binaryType) {
    switch (binaryType) {
      case "blob":
        return data instanceof ArrayBuffer ? new Blob([data]) : data;

      case "arraybuffer":
      default:
        return data;
      // assuming the data is already an ArrayBuffer
    }
  };

  var SEPARATOR = String.fromCharCode(30); // see https://en.wikipedia.org/wiki/Delimiter#ASCII_delimited_text

  var encodePayload = function encodePayload(packets, callback) {
    // some packets may be added to the array while encoding, so the initial length must be saved
    var length = packets.length;
    var encodedPackets = new Array(length);
    var count = 0;
    packets.forEach(function (packet, i) {
      // force base64 encoding for binary packets
      encodePacket(packet, false, function (encodedPacket) {
        encodedPackets[i] = encodedPacket;

        if (++count === length) {
          callback(encodedPackets.join(SEPARATOR));
        }
      });
    });
  };

  var decodePayload = function decodePayload(encodedPayload, binaryType) {
    var encodedPackets = encodedPayload.split(SEPARATOR);
    var packets = [];

    for (var i = 0; i < encodedPackets.length; i++) {
      var decodedPacket = decodePacket(encodedPackets[i], binaryType);
      packets.push(decodedPacket);

      if (decodedPacket.type === "error") {
        break;
      }
    }

    return packets;
  };

  var protocol = 4;

  /**
   * Initialize a new `Emitter`.
   *
   * @api public
   */
  function Emitter(obj) {
    if (obj) return mixin(obj);
  }
  /**
   * Mixin the emitter properties.
   *
   * @param {Object} obj
   * @return {Object}
   * @api private
   */

  function mixin(obj) {
    for (var key in Emitter.prototype) {
      obj[key] = Emitter.prototype[key];
    }

    return obj;
  }
  /**
   * Listen on the given `event` with `fn`.
   *
   * @param {String} event
   * @param {Function} fn
   * @return {Emitter}
   * @api public
   */


  Emitter.prototype.on = Emitter.prototype.addEventListener = function (event, fn) {
    this._callbacks = this._callbacks || {};
    (this._callbacks['$' + event] = this._callbacks['$' + event] || []).push(fn);
    return this;
  };
  /**
   * Adds an `event` listener that will be invoked a single
   * time then automatically removed.
   *
   * @param {String} event
   * @param {Function} fn
   * @return {Emitter}
   * @api public
   */


  Emitter.prototype.once = function (event, fn) {
    function on() {
      this.off(event, on);
      fn.apply(this, arguments);
    }

    on.fn = fn;
    this.on(event, on);
    return this;
  };
  /**
   * Remove the given callback for `event` or all
   * registered callbacks.
   *
   * @param {String} event
   * @param {Function} fn
   * @return {Emitter}
   * @api public
   */


  Emitter.prototype.off = Emitter.prototype.removeListener = Emitter.prototype.removeAllListeners = Emitter.prototype.removeEventListener = function (event, fn) {
    this._callbacks = this._callbacks || {}; // all

    if (0 == arguments.length) {
      this._callbacks = {};
      return this;
    } // specific event


    var callbacks = this._callbacks['$' + event];
    if (!callbacks) return this; // remove all handlers

    if (1 == arguments.length) {
      delete this._callbacks['$' + event];
      return this;
    } // remove specific handler


    var cb;

    for (var i = 0; i < callbacks.length; i++) {
      cb = callbacks[i];

      if (cb === fn || cb.fn === fn) {
        callbacks.splice(i, 1);
        break;
      }
    } // Remove event specific arrays for event types that no
    // one is subscribed for to avoid memory leak.


    if (callbacks.length === 0) {
      delete this._callbacks['$' + event];
    }

    return this;
  };
  /**
   * Emit `event` with the given args.
   *
   * @param {String} event
   * @param {Mixed} ...
   * @return {Emitter}
   */


  Emitter.prototype.emit = function (event) {
    this._callbacks = this._callbacks || {};
    var args = new Array(arguments.length - 1),
        callbacks = this._callbacks['$' + event];

    for (var i = 1; i < arguments.length; i++) {
      args[i - 1] = arguments[i];
    }

    if (callbacks) {
      callbacks = callbacks.slice(0);

      for (var i = 0, len = callbacks.length; i < len; ++i) {
        callbacks[i].apply(this, args);
      }
    }

    return this;
  }; // alias used for reserved events (protected method)


  Emitter.prototype.emitReserved = Emitter.prototype.emit;
  /**
   * Return array of callbacks for `event`.
   *
   * @param {String} event
   * @return {Array}
   * @api public
   */

  Emitter.prototype.listeners = function (event) {
    this._callbacks = this._callbacks || {};
    return this._callbacks['$' + event] || [];
  };
  /**
   * Check if this emitter has `event` handlers.
   *
   * @param {String} event
   * @return {Boolean}
   * @api public
   */


  Emitter.prototype.hasListeners = function (event) {
    return !!this.listeners(event).length;
  };

  var globalThisShim = function () {
    if (typeof self !== "undefined") {
      return self;
    } else if (typeof window !== "undefined") {
      return window;
    } else {
      return Function("return this")();
    }
  }();

  function pick(obj) {
    for (var _len = arguments.length, attr = new Array(_len > 1 ? _len - 1 : 0), _key = 1; _key < _len; _key++) {
      attr[_key - 1] = arguments[_key];
    }

    return attr.reduce(function (acc, k) {
      if (obj.hasOwnProperty(k)) {
        acc[k] = obj[k];
      }

      return acc;
    }, {});
  } // Keep a reference to the real timeout functions so they can be used when overridden

  var NATIVE_SET_TIMEOUT = globalThisShim.setTimeout;
  var NATIVE_CLEAR_TIMEOUT = globalThisShim.clearTimeout;
  function installTimerFunctions(obj, opts) {
    if (opts.useNativeTimers) {
      obj.setTimeoutFn = NATIVE_SET_TIMEOUT.bind(globalThisShim);
      obj.clearTimeoutFn = NATIVE_CLEAR_TIMEOUT.bind(globalThisShim);
    } else {
      obj.setTimeoutFn = globalThisShim.setTimeout.bind(globalThisShim);
      obj.clearTimeoutFn = globalThisShim.clearTimeout.bind(globalThisShim);
    }
  } // base64 encoded buffers are about 33% bigger (https://en.wikipedia.org/wiki/Base64)

  var BASE64_OVERHEAD = 1.33; // we could also have used `new Blob([obj]).size`, but it isn't supported in IE9

  function byteLength(obj) {
    if (typeof obj === "string") {
      return utf8Length(obj);
    } // arraybuffer or blob


    return Math.ceil((obj.byteLength || obj.size) * BASE64_OVERHEAD);
  }

  function utf8Length(str) {
    var c = 0,
        length = 0;

    for (var i = 0, l = str.length; i < l; i++) {
      c = str.charCodeAt(i);

      if (c < 0x80) {
        length += 1;
      } else if (c < 0x800) {
        length += 2;
      } else if (c < 0xd800 || c >= 0xe000) {
        length += 3;
      } else {
        i++;
        length += 4;
      }
    }

    return length;
  }

  var TransportError = /*#__PURE__*/function (_Error) {
    _inherits(TransportError, _Error);

    var _super = _createSuper(TransportError);

    function TransportError(reason, description, context) {
      var _this;

      _classCallCheck(this, TransportError);

      _this = _super.call(this, reason);
      _this.description = description;
      _this.context = context;
      _this.type = "TransportError";
      return _this;
    }

    return TransportError;
  }( /*#__PURE__*/_wrapNativeSuper(Error));

  var Transport = /*#__PURE__*/function (_Emitter) {
    _inherits(Transport, _Emitter);

    var _super2 = _createSuper(Transport);

    /**
     * Transport abstract constructor.
     *
     * @param {Object} opts - options
     * @protected
     */
    function Transport(opts) {
      var _this2;

      _classCallCheck(this, Transport);

      _this2 = _super2.call(this);
      _this2.writable = false;
      installTimerFunctions(_assertThisInitialized(_this2), opts);
      _this2.opts = opts;
      _this2.query = opts.query;
      _this2.socket = opts.socket;
      return _this2;
    }
    /**
     * Emits an error.
     *
     * @param {String} reason
     * @param description
     * @param context - the error context
     * @return {Transport} for chaining
     * @protected
     */


    _createClass(Transport, [{
      key: "onError",
      value: function onError(reason, description, context) {
        _get(_getPrototypeOf(Transport.prototype), "emitReserved", this).call(this, "error", new TransportError(reason, description, context));

        return this;
      }
      /**
       * Opens the transport.
       */

    }, {
      key: "open",
      value: function open() {
        this.readyState = "opening";
        this.doOpen();
        return this;
      }
      /**
       * Closes the transport.
       */

    }, {
      key: "close",
      value: function close() {
        if (this.readyState === "opening" || this.readyState === "open") {
          this.doClose();
          this.onClose();
        }

        return this;
      }
      /**
       * Sends multiple packets.
       *
       * @param {Array} packets
       */

    }, {
      key: "send",
      value: function send(packets) {
        if (this.readyState === "open") {
          this.write(packets);
        }
      }
      /**
       * Called upon open
       *
       * @protected
       */

    }, {
      key: "onOpen",
      value: function onOpen() {
        this.readyState = "open";
        this.writable = true;

        _get(_getPrototypeOf(Transport.prototype), "emitReserved", this).call(this, "open");
      }
      /**
       * Called with data.
       *
       * @param {String} data
       * @protected
       */

    }, {
      key: "onData",
      value: function onData(data) {
        var packet = decodePacket(data, this.socket.binaryType);
        this.onPacket(packet);
      }
      /**
       * Called with a decoded packet.
       *
       * @protected
       */

    }, {
      key: "onPacket",
      value: function onPacket(packet) {
        _get(_getPrototypeOf(Transport.prototype), "emitReserved", this).call(this, "packet", packet);
      }
      /**
       * Called upon close.
       *
       * @protected
       */

    }, {
      key: "onClose",
      value: function onClose(details) {
        this.readyState = "closed";

        _get(_getPrototypeOf(Transport.prototype), "emitReserved", this).call(this, "close", details);
      }
      /**
       * Pauses the transport, in order not to lose packets during an upgrade.
       *
       * @param onPause
       */

    }, {
      key: "pause",
      value: function pause(onPause) {}
    }]);

    return Transport;
  }(Emitter);

  // imported from https://github.com/unshiftio/yeast

  var alphabet = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz-_'.split(''),
      length = 64,
      map = {};
  var seed = 0,
      i = 0,
      prev;
  /**
   * Return a string representing the specified number.
   *
   * @param {Number} num The number to convert.
   * @returns {String} The string representation of the number.
   * @api public
   */

  function encode$1(num) {
    var encoded = '';

    do {
      encoded = alphabet[num % length] + encoded;
      num = Math.floor(num / length);
    } while (num > 0);

    return encoded;
  }
  /**
   * Yeast: A tiny growing id generator.
   *
   * @returns {String} A unique id.
   * @api public
   */

  function yeast() {
    var now = encode$1(+new Date());
    if (now !== prev) return seed = 0, prev = now;
    return now + '.' + encode$1(seed++);
  } //
  // Map each character to its index.
  //

  for (; i < length; i++) {
    map[alphabet[i]] = i;
  }

  // imported from https://github.com/galkn/querystring

  /**
   * Compiles a querystring
   * Returns string representation of the object
   *
   * @param {Object}
   * @api private
   */
  function encode(obj) {
    var str = '';

    for (var i in obj) {
      if (obj.hasOwnProperty(i)) {
        if (str.length) str += '&';
        str += encodeURIComponent(i) + '=' + encodeURIComponent(obj[i]);
      }
    }

    return str;
  }
  /**
   * Parses a simple querystring into an object
   *
   * @param {String} qs
   * @api private
   */

  function decode(qs) {
    var qry = {};
    var pairs = qs.split('&');

    for (var i = 0, l = pairs.length; i < l; i++) {
      var pair = pairs[i].split('=');
      qry[decodeURIComponent(pair[0])] = decodeURIComponent(pair[1]);
    }

    return qry;
  }

  // imported from https://github.com/component/has-cors
  var value = false;

  try {
    value = typeof XMLHttpRequest !== 'undefined' && 'withCredentials' in new XMLHttpRequest();
  } catch (err) {// if XMLHttp support is disabled in IE then it will throw
    // when trying to create
  }

  var hasCORS = value;

  // browser shim for xmlhttprequest module
  function XHR(opts) {
    var xdomain = opts.xdomain; // XMLHttpRequest can be disabled on IE

    try {
      if ("undefined" !== typeof XMLHttpRequest && (!xdomain || hasCORS)) {
        return new XMLHttpRequest();
      }
    } catch (e) {}

    if (!xdomain) {
      try {
        return new globalThisShim[["Active"].concat("Object").join("X")]("Microsoft.XMLHTTP");
      } catch (e) {}
    }
  }

  function empty() {}

  var hasXHR2 = function () {
    var xhr = new XHR({
      xdomain: false
    });
    return null != xhr.responseType;
  }();

  var Polling = /*#__PURE__*/function (_Transport) {
    _inherits(Polling, _Transport);

    var _super = _createSuper(Polling);

    /**
     * XHR Polling constructor.
     *
     * @param {Object} opts
     * @package
     */
    function Polling(opts) {
      var _this;

      _classCallCheck(this, Polling);

      _this = _super.call(this, opts);
      _this.polling = false;

      if (typeof location !== "undefined") {
        var isSSL = "https:" === location.protocol;
        var port = location.port; // some user agents have empty `location.port`

        if (!port) {
          port = isSSL ? "443" : "80";
        }

        _this.xd = typeof location !== "undefined" && opts.hostname !== location.hostname || port !== opts.port;
        _this.xs = opts.secure !== isSSL;
      }
      /**
       * XHR supports binary
       */


      var forceBase64 = opts && opts.forceBase64;
      _this.supportsBinary = hasXHR2 && !forceBase64;
      return _this;
    }

    _createClass(Polling, [{
      key: "doOpen",

      /**
       * Opens the socket (triggers polling). We write a PING message to determine
       * when the transport is open.
       *
       * @protected
       */
      value: function doOpen() {
        this.poll();
      }
      /**
       * Pauses polling.
       *
       * @param {Function} onPause - callback upon buffers are flushed and transport is paused
       * @package
       */

    }, {
      key: "pause",
      value: function pause(onPause) {
        var _this2 = this;

        this.readyState = "pausing";

        var pause = function pause() {
          _this2.readyState = "paused";
          onPause();
        };

        if (this.polling || !this.writable) {
          var total = 0;

          if (this.polling) {
            total++;
            this.once("pollComplete", function () {
              --total || pause();
            });
          }

          if (!this.writable) {
            total++;
            this.once("drain", function () {
              --total || pause();
            });
          }
        } else {
          pause();
        }
      }
      /**
       * Starts polling cycle.
       *
       * @private
       */

    }, {
      key: "poll",
      value: function poll() {
        this.polling = true;
        this.doPoll();
        this.emitReserved("poll");
      }
      /**
       * Overloads onData to detect payloads.
       *
       * @protected
       */

    }, {
      key: "onData",
      value: function onData(data) {
        var _this3 = this;

        var callback = function callback(packet) {
          // if its the first message we consider the transport open
          if ("opening" === _this3.readyState && packet.type === "open") {
            _this3.onOpen();
          } // if its a close packet, we close the ongoing requests


          if ("close" === packet.type) {
            _this3.onClose({
              description: "transport closed by the server"
            });

            return false;
          } // otherwise bypass onData and handle the message


          _this3.onPacket(packet);
        }; // decode payload


        decodePayload(data, this.socket.binaryType).forEach(callback); // if an event did not trigger closing

        if ("closed" !== this.readyState) {
          // if we got data we're not polling
          this.polling = false;
          this.emitReserved("pollComplete");

          if ("open" === this.readyState) {
            this.poll();
          }
        }
      }
      /**
       * For polling, send a close packet.
       *
       * @protected
       */

    }, {
      key: "doClose",
      value: function doClose() {
        var _this4 = this;

        var close = function close() {
          _this4.write([{
            type: "close"
          }]);
        };

        if ("open" === this.readyState) {
          close();
        } else {
          // in case we're trying to close while
          // handshaking is in progress (GH-164)
          this.once("open", close);
        }
      }
      /**
       * Writes a packets payload.
       *
       * @param {Array} packets - data packets
       * @protected
       */

    }, {
      key: "write",
      value: function write(packets) {
        var _this5 = this;

        this.writable = false;
        encodePayload(packets, function (data) {
          _this5.doWrite(data, function () {
            _this5.writable = true;

            _this5.emitReserved("drain");
          });
        });
      }
      /**
       * Generates uri for connection.
       *
       * @private
       */

    }, {
      key: "uri",
      value: function uri() {
        var query = this.query || {};
        var schema = this.opts.secure ? "https" : "http";
        var port = ""; // cache busting is forced

        if (false !== this.opts.timestampRequests) {
          query[this.opts.timestampParam] = yeast();
        }

        if (!this.supportsBinary && !query.sid) {
          query.b64 = 1;
        } // avoid port if default for schema


        if (this.opts.port && ("https" === schema && Number(this.opts.port) !== 443 || "http" === schema && Number(this.opts.port) !== 80)) {
          port = ":" + this.opts.port;
        }

        var encodedQuery = encode(query);
        var ipv6 = this.opts.hostname.indexOf(":") !== -1;
        return schema + "://" + (ipv6 ? "[" + this.opts.hostname + "]" : this.opts.hostname) + port + this.opts.path + (encodedQuery.length ? "?" + encodedQuery : "");
      }
      /**
       * Creates a request.
       *
       * @param {String} method
       * @private
       */

    }, {
      key: "request",
      value: function request() {
        var opts = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : {};

        _extends(opts, {
          xd: this.xd,
          xs: this.xs
        }, this.opts);

        return new Request(this.uri(), opts);
      }
      /**
       * Sends data.
       *
       * @param {String} data to send.
       * @param {Function} called upon flush.
       * @private
       */

    }, {
      key: "doWrite",
      value: function doWrite(data, fn) {
        var _this6 = this;

        var req = this.request({
          method: "POST",
          data: data
        });
        req.on("success", fn);
        req.on("error", function (xhrStatus, context) {
          _this6.onError("xhr post error", xhrStatus, context);
        });
      }
      /**
       * Starts a poll cycle.
       *
       * @private
       */

    }, {
      key: "doPoll",
      value: function doPoll() {
        var _this7 = this;

        var req = this.request();
        req.on("data", this.onData.bind(this));
        req.on("error", function (xhrStatus, context) {
          _this7.onError("xhr poll error", xhrStatus, context);
        });
        this.pollXhr = req;
      }
    }, {
      key: "name",
      get: function get() {
        return "polling";
      }
    }]);

    return Polling;
  }(Transport);
  var Request = /*#__PURE__*/function (_Emitter) {
    _inherits(Request, _Emitter);

    var _super2 = _createSuper(Request);

    /**
     * Request constructor
     *
     * @param {Object} options
     * @package
     */
    function Request(uri, opts) {
      var _this8;

      _classCallCheck(this, Request);

      _this8 = _super2.call(this);
      installTimerFunctions(_assertThisInitialized(_this8), opts);
      _this8.opts = opts;
      _this8.method = opts.method || "GET";
      _this8.uri = uri;
      _this8.async = false !== opts.async;
      _this8.data = undefined !== opts.data ? opts.data : null;

      _this8.create();

      return _this8;
    }
    /**
     * Creates the XHR object and sends the request.
     *
     * @private
     */


    _createClass(Request, [{
      key: "create",
      value: function create() {
        var _this9 = this;

        var opts = pick(this.opts, "agent", "pfx", "key", "passphrase", "cert", "ca", "ciphers", "rejectUnauthorized", "autoUnref");
        opts.xdomain = !!this.opts.xd;
        opts.xscheme = !!this.opts.xs;
        var xhr = this.xhr = new XHR(opts);

        try {
          xhr.open(this.method, this.uri, this.async);

          try {
            if (this.opts.extraHeaders) {
              xhr.setDisableHeaderCheck && xhr.setDisableHeaderCheck(true);

              for (var i in this.opts.extraHeaders) {
                if (this.opts.extraHeaders.hasOwnProperty(i)) {
                  xhr.setRequestHeader(i, this.opts.extraHeaders[i]);
                }
              }
            }
          } catch (e) {}

          if ("POST" === this.method) {
            try {
              xhr.setRequestHeader("Content-type", "text/plain;charset=UTF-8");
            } catch (e) {}
          }

          try {
            xhr.setRequestHeader("Accept", "*/*");
          } catch (e) {} // ie6 check


          if ("withCredentials" in xhr) {
            xhr.withCredentials = this.opts.withCredentials;
          }

          if (this.opts.requestTimeout) {
            xhr.timeout = this.opts.requestTimeout;
          }

          xhr.onreadystatechange = function () {
            if (4 !== xhr.readyState) return;

            if (200 === xhr.status || 1223 === xhr.status) {
              _this9.onLoad();
            } else {
              // make sure the `error` event handler that's user-set
              // does not throw in the same tick and gets caught here
              _this9.setTimeoutFn(function () {
                _this9.onError(typeof xhr.status === "number" ? xhr.status : 0);
              }, 0);
            }
          };

          xhr.send(this.data);
        } catch (e) {
          // Need to defer since .create() is called directly from the constructor
          // and thus the 'error' event can only be only bound *after* this exception
          // occurs.  Therefore, also, we cannot throw here at all.
          this.setTimeoutFn(function () {
            _this9.onError(e);
          }, 0);
          return;
        }

        if (typeof document !== "undefined") {
          this.index = Request.requestsCount++;
          Request.requests[this.index] = this;
        }
      }
      /**
       * Called upon error.
       *
       * @private
       */

    }, {
      key: "onError",
      value: function onError(err) {
        this.emitReserved("error", err, this.xhr);
        this.cleanup(true);
      }
      /**
       * Cleans up house.
       *
       * @private
       */

    }, {
      key: "cleanup",
      value: function cleanup(fromError) {
        if ("undefined" === typeof this.xhr || null === this.xhr) {
          return;
        }

        this.xhr.onreadystatechange = empty;

        if (fromError) {
          try {
            this.xhr.abort();
          } catch (e) {}
        }

        if (typeof document !== "undefined") {
          delete Request.requests[this.index];
        }

        this.xhr = null;
      }
      /**
       * Called upon load.
       *
       * @private
       */

    }, {
      key: "onLoad",
      value: function onLoad() {
        var data = this.xhr.responseText;

        if (data !== null) {
          this.emitReserved("data", data);
          this.emitReserved("success");
          this.cleanup();
        }
      }
      /**
       * Aborts the request.
       *
       * @package
       */

    }, {
      key: "abort",
      value: function abort() {
        this.cleanup();
      }
    }]);

    return Request;
  }(Emitter);
  Request.requestsCount = 0;
  Request.requests = {};
  /**
   * Aborts pending requests when unloading the window. This is needed to prevent
   * memory leaks (e.g. when using IE) and to ensure that no spurious error is
   * emitted.
   */

  if (typeof document !== "undefined") {
    // @ts-ignore
    if (typeof attachEvent === "function") {
      // @ts-ignore
      attachEvent("onunload", unloadHandler);
    } else if (typeof addEventListener === "function") {
      var terminationEvent = "onpagehide" in globalThisShim ? "pagehide" : "unload";
      addEventListener(terminationEvent, unloadHandler, false);
    }
  }

  function unloadHandler() {
    for (var i in Request.requests) {
      if (Request.requests.hasOwnProperty(i)) {
        Request.requests[i].abort();
      }
    }
  }

  var nextTick = function () {
    var isPromiseAvailable = typeof Promise === "function" && typeof Promise.resolve === "function";

    if (isPromiseAvailable) {
      return function (cb) {
        return Promise.resolve().then(cb);
      };
    } else {
      return function (cb, setTimeoutFn) {
        return setTimeoutFn(cb, 0);
      };
    }
  }();
  var WebSocket = globalThisShim.WebSocket || globalThisShim.MozWebSocket;
  var usingBrowserWebSocket = true;
  var defaultBinaryType = "arraybuffer";

  var isReactNative = typeof navigator !== "undefined" && typeof navigator.product === "string" && navigator.product.toLowerCase() === "reactnative";
  var WS = /*#__PURE__*/function (_Transport) {
    _inherits(WS, _Transport);

    var _super = _createSuper(WS);

    /**
     * WebSocket transport constructor.
     *
     * @param {Object} opts - connection options
     * @protected
     */
    function WS(opts) {
      var _this;

      _classCallCheck(this, WS);

      _this = _super.call(this, opts);
      _this.supportsBinary = !opts.forceBase64;
      return _this;
    }

    _createClass(WS, [{
      key: "doOpen",
      value: function doOpen() {
        if (!this.check()) {
          // let probe timeout
          return;
        }

        var uri = this.uri();
        var protocols = this.opts.protocols; // React Native only supports the 'headers' option, and will print a warning if anything else is passed

        var opts = isReactNative ? {} : pick(this.opts, "agent", "perMessageDeflate", "pfx", "key", "passphrase", "cert", "ca", "ciphers", "rejectUnauthorized", "localAddress", "protocolVersion", "origin", "maxPayload", "family", "checkServerIdentity");

        if (this.opts.extraHeaders) {
          opts.headers = this.opts.extraHeaders;
        }

        try {
          this.ws = usingBrowserWebSocket && !isReactNative ? protocols ? new WebSocket(uri, protocols) : new WebSocket(uri) : new WebSocket(uri, protocols, opts);
        } catch (err) {
          return this.emitReserved("error", err);
        }

        this.ws.binaryType = this.socket.binaryType || defaultBinaryType;
        this.addEventListeners();
      }
      /**
       * Adds event listeners to the socket
       *
       * @private
       */

    }, {
      key: "addEventListeners",
      value: function addEventListeners() {
        var _this2 = this;

        this.ws.onopen = function () {
          if (_this2.opts.autoUnref) {
            _this2.ws._socket.unref();
          }

          _this2.onOpen();
        };

        this.ws.onclose = function (closeEvent) {
          return _this2.onClose({
            description: "websocket connection closed",
            context: closeEvent
          });
        };

        this.ws.onmessage = function (ev) {
          return _this2.onData(ev.data);
        };

        this.ws.onerror = function (e) {
          return _this2.onError("websocket error", e);
        };
      }
    }, {
      key: "write",
      value: function write(packets) {
        var _this3 = this;

        this.writable = false; // encodePacket efficient as it uses WS framing
        // no need for encodePayload

        var _loop = function _loop(i) {
          var packet = packets[i];
          var lastPacket = i === packets.length - 1;
          encodePacket(packet, _this3.supportsBinary, function (data) {
            // always create a new object (GH-437)
            var opts = {};
            // have a chance of informing us about it yet, in that case send will
            // throw an error


            try {
              if (usingBrowserWebSocket) {
                // TypeError is thrown when passing the second argument on Safari
                _this3.ws.send(data);
              }
            } catch (e) {}

            if (lastPacket) {
              // fake drain
              // defer to next tick to allow Socket to clear writeBuffer
              nextTick(function () {
                _this3.writable = true;

                _this3.emitReserved("drain");
              }, _this3.setTimeoutFn);
            }
          });
        };

        for (var i = 0; i < packets.length; i++) {
          _loop(i);
        }
      }
    }, {
      key: "doClose",
      value: function doClose() {
        if (typeof this.ws !== "undefined") {
          this.ws.close();
          this.ws = null;
        }
      }
      /**
       * Generates uri for connection.
       *
       * @private
       */

    }, {
      key: "uri",
      value: function uri() {
        var query = this.query || {};
        var schema = this.opts.secure ? "wss" : "ws";
        var port = ""; // avoid port if default for schema

        if (this.opts.port && ("wss" === schema && Number(this.opts.port) !== 443 || "ws" === schema && Number(this.opts.port) !== 80)) {
          port = ":" + this.opts.port;
        } // append timestamp to URI


        if (this.opts.timestampRequests) {
          query[this.opts.timestampParam] = yeast();
        } // communicate binary support capabilities


        if (!this.supportsBinary) {
          query.b64 = 1;
        }

        var encodedQuery = encode(query);
        var ipv6 = this.opts.hostname.indexOf(":") !== -1;
        return schema + "://" + (ipv6 ? "[" + this.opts.hostname + "]" : this.opts.hostname) + port + this.opts.path + (encodedQuery.length ? "?" + encodedQuery : "");
      }
      /**
       * Feature detection for WebSocket.
       *
       * @return {Boolean} whether this transport is available.
       * @private
       */

    }, {
      key: "check",
      value: function check() {
        return !!WebSocket;
      }
    }, {
      key: "name",
      get: function get() {
        return "websocket";
      }
    }]);

    return WS;
  }(Transport);

  var transports = {
    websocket: WS,
    polling: Polling
  };

  // imported from https://github.com/galkn/parseuri

  /**
   * Parses a URI
   *
   * Note: we could also have used the built-in URL object, but it isn't supported on all platforms.
   *
   * See:
   * - https://developer.mozilla.org/en-US/docs/Web/API/URL
   * - https://caniuse.com/url
   * - https://www.rfc-editor.org/rfc/rfc3986#appendix-B
   *
   * History of the parse() method:
   * - first commit: https://github.com/socketio/socket.io-client/commit/4ee1d5d94b3906a9c052b459f1a818b15f38f91c
   * - export into its own module: https://github.com/socketio/engine.io-client/commit/de2c561e4564efeb78f1bdb1ba39ef81b2822cb3
   * - reimport: https://github.com/socketio/engine.io-client/commit/df32277c3f6d622eec5ed09f493cae3f3391d242
   *
   * @author Steven Levithan <stevenlevithan.com> (MIT license)
   * @api private
   */
  var re = /^(?:(?![^:@\/?#]+:[^:@\/]*@)(http|https|ws|wss):\/\/)?((?:(([^:@\/?#]*)(?::([^:@\/?#]*))?)?@)?((?:[a-f0-9]{0,4}:){2,7}[a-f0-9]{0,4}|[^:\/?#]*)(?::(\d*))?)(((\/(?:[^?#](?![^?#\/]*\.[^?#\/.]+(?:[?#]|$)))*\/?)?([^?#\/]*))(?:\?([^#]*))?(?:#(.*))?)/;
  var parts = ['source', 'protocol', 'authority', 'userInfo', 'user', 'password', 'host', 'port', 'relative', 'path', 'directory', 'file', 'query', 'anchor'];
  function parse(str) {
    var src = str,
        b = str.indexOf('['),
        e = str.indexOf(']');

    if (b != -1 && e != -1) {
      str = str.substring(0, b) + str.substring(b, e).replace(/:/g, ';') + str.substring(e, str.length);
    }

    var m = re.exec(str || ''),
        uri = {},
        i = 14;

    while (i--) {
      uri[parts[i]] = m[i] || '';
    }

    if (b != -1 && e != -1) {
      uri.source = src;
      uri.host = uri.host.substring(1, uri.host.length - 1).replace(/;/g, ':');
      uri.authority = uri.authority.replace('[', '').replace(']', '').replace(/;/g, ':');
      uri.ipv6uri = true;
    }

    uri.pathNames = pathNames(uri, uri['path']);
    uri.queryKey = queryKey(uri, uri['query']);
    return uri;
  }

  function pathNames(obj, path) {
    var regx = /\/{2,9}/g,
        names = path.replace(regx, "/").split("/");

    if (path.slice(0, 1) == '/' || path.length === 0) {
      names.splice(0, 1);
    }

    if (path.slice(-1) == '/') {
      names.splice(names.length - 1, 1);
    }

    return names;
  }

  function queryKey(uri, query) {
    var data = {};
    query.replace(/(?:^|&)([^&=]*)=?([^&]*)/g, function ($0, $1, $2) {
      if ($1) {
        data[$1] = $2;
      }
    });
    return data;
  }

  var Socket = /*#__PURE__*/function (_Emitter) {
    _inherits(Socket, _Emitter);

    var _super = _createSuper(Socket);

    /**
     * Socket constructor.
     *
     * @param {String|Object} uri - uri or options
     * @param {Object} opts - options
     */
    function Socket(uri) {
      var _this;

      var opts = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : {};

      _classCallCheck(this, Socket);

      _this = _super.call(this);
      _this.writeBuffer = [];

      if (uri && "object" === _typeof(uri)) {
        opts = uri;
        uri = null;
      }

      if (uri) {
        uri = parse(uri);
        opts.hostname = uri.host;
        opts.secure = uri.protocol === "https" || uri.protocol === "wss";
        opts.port = uri.port;
        if (uri.query) opts.query = uri.query;
      } else if (opts.host) {
        opts.hostname = parse(opts.host).host;
      }

      installTimerFunctions(_assertThisInitialized(_this), opts);
      _this.secure = null != opts.secure ? opts.secure : typeof location !== "undefined" && "https:" === location.protocol;

      if (opts.hostname && !opts.port) {
        // if no port is specified manually, use the protocol default
        opts.port = _this.secure ? "443" : "80";
      }

      _this.hostname = opts.hostname || (typeof location !== "undefined" ? location.hostname : "localhost");
      _this.port = opts.port || (typeof location !== "undefined" && location.port ? location.port : _this.secure ? "443" : "80");
      _this.transports = opts.transports || ["polling", "websocket"];
      _this.writeBuffer = [];
      _this.prevBufferLen = 0;
      _this.opts = _extends({
        path: "/engine.io",
        agent: false,
        withCredentials: false,
        upgrade: true,
        timestampParam: "t",
        rememberUpgrade: false,
        addTrailingSlash: true,
        rejectUnauthorized: true,
        perMessageDeflate: {
          threshold: 1024
        },
        transportOptions: {},
        closeOnBeforeunload: true
      }, opts);
      _this.opts.path = _this.opts.path.replace(/\/$/, "") + (_this.opts.addTrailingSlash ? "/" : "");

      if (typeof _this.opts.query === "string") {
        _this.opts.query = decode(_this.opts.query);
      } // set on handshake


      _this.id = null;
      _this.upgrades = null;
      _this.pingInterval = null;
      _this.pingTimeout = null; // set on heartbeat

      _this.pingTimeoutTimer = null;

      if (typeof addEventListener === "function") {
        if (_this.opts.closeOnBeforeunload) {
          // Firefox closes the connection when the "beforeunload" event is emitted but not Chrome. This event listener
          // ensures every browser behaves the same (no "disconnect" event at the Socket.IO level when the page is
          // closed/reloaded)
          _this.beforeunloadEventListener = function () {
            if (_this.transport) {
              // silently close the transport
              _this.transport.removeAllListeners();

              _this.transport.close();
            }
          };

          addEventListener("beforeunload", _this.beforeunloadEventListener, false);
        }

        if (_this.hostname !== "localhost") {
          _this.offlineEventListener = function () {
            _this.onClose("transport close", {
              description: "network connection lost"
            });
          };

          addEventListener("offline", _this.offlineEventListener, false);
        }
      }

      _this.open();

      return _this;
    }
    /**
     * Creates transport of the given type.
     *
     * @param {String} name - transport name
     * @return {Transport}
     * @private
     */


    _createClass(Socket, [{
      key: "createTransport",
      value: function createTransport(name) {
        var query = _extends({}, this.opts.query); // append engine.io protocol identifier


        query.EIO = protocol; // transport name

        query.transport = name; // session id if we already have one

        if (this.id) query.sid = this.id;

        var opts = _extends({}, this.opts.transportOptions[name], this.opts, {
          query: query,
          socket: this,
          hostname: this.hostname,
          secure: this.secure,
          port: this.port
        });

        return new transports[name](opts);
      }
      /**
       * Initializes transport to use and starts probe.
       *
       * @private
       */

    }, {
      key: "open",
      value: function open() {
        var _this2 = this;

        var transport;

        if (this.opts.rememberUpgrade && Socket.priorWebsocketSuccess && this.transports.indexOf("websocket") !== -1) {
          transport = "websocket";
        } else if (0 === this.transports.length) {
          // Emit error on next tick so it can be listened to
          this.setTimeoutFn(function () {
            _this2.emitReserved("error", "No transports available");
          }, 0);
          return;
        } else {
          transport = this.transports[0];
        }

        this.readyState = "opening"; // Retry with the next transport if the transport is disabled (jsonp: false)

        try {
          transport = this.createTransport(transport);
        } catch (e) {
          this.transports.shift();
          this.open();
          return;
        }

        transport.open();
        this.setTransport(transport);
      }
      /**
       * Sets the current transport. Disables the existing one (if any).
       *
       * @private
       */

    }, {
      key: "setTransport",
      value: function setTransport(transport) {
        var _this3 = this;

        if (this.transport) {
          this.transport.removeAllListeners();
        } // set up transport


        this.transport = transport; // set up transport listeners

        transport.on("drain", this.onDrain.bind(this)).on("packet", this.onPacket.bind(this)).on("error", this.onError.bind(this)).on("close", function (reason) {
          return _this3.onClose("transport close", reason);
        });
      }
      /**
       * Probes a transport.
       *
       * @param {String} name - transport name
       * @private
       */

    }, {
      key: "probe",
      value: function probe(name) {
        var _this4 = this;

        var transport = this.createTransport(name);
        var failed = false;
        Socket.priorWebsocketSuccess = false;

        var onTransportOpen = function onTransportOpen() {
          if (failed) return;
          transport.send([{
            type: "ping",
            data: "probe"
          }]);
          transport.once("packet", function (msg) {
            if (failed) return;

            if ("pong" === msg.type && "probe" === msg.data) {
              _this4.upgrading = true;

              _this4.emitReserved("upgrading", transport);

              if (!transport) return;
              Socket.priorWebsocketSuccess = "websocket" === transport.name;

              _this4.transport.pause(function () {
                if (failed) return;
                if ("closed" === _this4.readyState) return;
                cleanup();

                _this4.setTransport(transport);

                transport.send([{
                  type: "upgrade"
                }]);

                _this4.emitReserved("upgrade", transport);

                transport = null;
                _this4.upgrading = false;

                _this4.flush();
              });
            } else {
              var err = new Error("probe error"); // @ts-ignore

              err.transport = transport.name;

              _this4.emitReserved("upgradeError", err);
            }
          });
        };

        function freezeTransport() {
          if (failed) return; // Any callback called by transport should be ignored since now

          failed = true;
          cleanup();
          transport.close();
          transport = null;
        } // Handle any error that happens while probing


        var onerror = function onerror(err) {
          var error = new Error("probe error: " + err); // @ts-ignore

          error.transport = transport.name;
          freezeTransport();

          _this4.emitReserved("upgradeError", error);
        };

        function onTransportClose() {
          onerror("transport closed");
        } // When the socket is closed while we're probing


        function onclose() {
          onerror("socket closed");
        } // When the socket is upgraded while we're probing


        function onupgrade(to) {
          if (transport && to.name !== transport.name) {
            freezeTransport();
          }
        } // Remove all listeners on the transport and on self


        var cleanup = function cleanup() {
          transport.removeListener("open", onTransportOpen);
          transport.removeListener("error", onerror);
          transport.removeListener("close", onTransportClose);

          _this4.off("close", onclose);

          _this4.off("upgrading", onupgrade);
        };

        transport.once("open", onTransportOpen);
        transport.once("error", onerror);
        transport.once("close", onTransportClose);
        this.once("close", onclose);
        this.once("upgrading", onupgrade);
        transport.open();
      }
      /**
       * Called when connection is deemed open.
       *
       * @private
       */

    }, {
      key: "onOpen",
      value: function onOpen() {
        this.readyState = "open";
        Socket.priorWebsocketSuccess = "websocket" === this.transport.name;
        this.emitReserved("open");
        this.flush(); // we check for `readyState` in case an `open`
        // listener already closed the socket

        if ("open" === this.readyState && this.opts.upgrade) {
          var i = 0;
          var l = this.upgrades.length;

          for (; i < l; i++) {
            this.probe(this.upgrades[i]);
          }
        }
      }
      /**
       * Handles a packet.
       *
       * @private
       */

    }, {
      key: "onPacket",
      value: function onPacket(packet) {
        if ("opening" === this.readyState || "open" === this.readyState || "closing" === this.readyState) {
          this.emitReserved("packet", packet); // Socket is live - any packet counts

          this.emitReserved("heartbeat");

          switch (packet.type) {
            case "open":
              this.onHandshake(JSON.parse(packet.data));
              break;

            case "ping":
              this.resetPingTimeout();
              this.sendPacket("pong");
              this.emitReserved("ping");
              this.emitReserved("pong");
              break;

            case "error":
              var err = new Error("server error"); // @ts-ignore

              err.code = packet.data;
              this.onError(err);
              break;

            case "message":
              this.emitReserved("data", packet.data);
              this.emitReserved("message", packet.data);
              break;
          }
        }
      }
      /**
       * Called upon handshake completion.
       *
       * @param {Object} data - handshake obj
       * @private
       */

    }, {
      key: "onHandshake",
      value: function onHandshake(data) {
        this.emitReserved("handshake", data);
        this.id = data.sid;
        this.transport.query.sid = data.sid;
        this.upgrades = this.filterUpgrades(data.upgrades);
        this.pingInterval = data.pingInterval;
        this.pingTimeout = data.pingTimeout;
        this.maxPayload = data.maxPayload;
        this.onOpen(); // In case open handler closes socket

        if ("closed" === this.readyState) return;
        this.resetPingTimeout();
      }
      /**
       * Sets and resets ping timeout timer based on server pings.
       *
       * @private
       */

    }, {
      key: "resetPingTimeout",
      value: function resetPingTimeout() {
        var _this5 = this;

        this.clearTimeoutFn(this.pingTimeoutTimer);
        this.pingTimeoutTimer = this.setTimeoutFn(function () {
          _this5.onClose("ping timeout");
        }, this.pingInterval + this.pingTimeout);

        if (this.opts.autoUnref) {
          this.pingTimeoutTimer.unref();
        }
      }
      /**
       * Called on `drain` event
       *
       * @private
       */

    }, {
      key: "onDrain",
      value: function onDrain() {
        this.writeBuffer.splice(0, this.prevBufferLen); // setting prevBufferLen = 0 is very important
        // for example, when upgrading, upgrade packet is sent over,
        // and a nonzero prevBufferLen could cause problems on `drain`

        this.prevBufferLen = 0;

        if (0 === this.writeBuffer.length) {
          this.emitReserved("drain");
        } else {
          this.flush();
        }
      }
      /**
       * Flush write buffers.
       *
       * @private
       */

    }, {
      key: "flush",
      value: function flush() {
        if ("closed" !== this.readyState && this.transport.writable && !this.upgrading && this.writeBuffer.length) {
          var packets = this.getWritablePackets();
          this.transport.send(packets); // keep track of current length of writeBuffer
          // splice writeBuffer and callbackBuffer on `drain`

          this.prevBufferLen = packets.length;
          this.emitReserved("flush");
        }
      }
      /**
       * Ensure the encoded size of the writeBuffer is below the maxPayload value sent by the server (only for HTTP
       * long-polling)
       *
       * @private
       */

    }, {
      key: "getWritablePackets",
      value: function getWritablePackets() {
        var shouldCheckPayloadSize = this.maxPayload && this.transport.name === "polling" && this.writeBuffer.length > 1;

        if (!shouldCheckPayloadSize) {
          return this.writeBuffer;
        }

        var payloadSize = 1; // first packet type

        for (var i = 0; i < this.writeBuffer.length; i++) {
          var data = this.writeBuffer[i].data;

          if (data) {
            payloadSize += byteLength(data);
          }

          if (i > 0 && payloadSize > this.maxPayload) {
            return this.writeBuffer.slice(0, i);
          }

          payloadSize += 2; // separator + packet type
        }

        return this.writeBuffer;
      }
      /**
       * Sends a message.
       *
       * @param {String} msg - message.
       * @param {Object} options.
       * @param {Function} callback function.
       * @return {Socket} for chaining.
       */

    }, {
      key: "write",
      value: function write(msg, options, fn) {
        this.sendPacket("message", msg, options, fn);
        return this;
      }
    }, {
      key: "send",
      value: function send(msg, options, fn) {
        this.sendPacket("message", msg, options, fn);
        return this;
      }
      /**
       * Sends a packet.
       *
       * @param {String} type: packet type.
       * @param {String} data.
       * @param {Object} options.
       * @param {Function} fn - callback function.
       * @private
       */

    }, {
      key: "sendPacket",
      value: function sendPacket(type, data, options, fn) {
        if ("function" === typeof data) {
          fn = data;
          data = undefined;
        }

        if ("function" === typeof options) {
          fn = options;
          options = null;
        }

        if ("closing" === this.readyState || "closed" === this.readyState) {
          return;
        }

        options = options || {};
        options.compress = false !== options.compress;
        var packet = {
          type: type,
          data: data,
          options: options
        };
        this.emitReserved("packetCreate", packet);
        this.writeBuffer.push(packet);
        if (fn) this.once("flush", fn);
        this.flush();
      }
      /**
       * Closes the connection.
       */

    }, {
      key: "close",
      value: function close() {
        var _this6 = this;

        var close = function close() {
          _this6.onClose("forced close");

          _this6.transport.close();
        };

        var cleanupAndClose = function cleanupAndClose() {
          _this6.off("upgrade", cleanupAndClose);

          _this6.off("upgradeError", cleanupAndClose);

          close();
        };

        var waitForUpgrade = function waitForUpgrade() {
          // wait for upgrade to finish since we can't send packets while pausing a transport
          _this6.once("upgrade", cleanupAndClose);

          _this6.once("upgradeError", cleanupAndClose);
        };

        if ("opening" === this.readyState || "open" === this.readyState) {
          this.readyState = "closing";

          if (this.writeBuffer.length) {
            this.once("drain", function () {
              if (_this6.upgrading) {
                waitForUpgrade();
              } else {
                close();
              }
            });
          } else if (this.upgrading) {
            waitForUpgrade();
          } else {
            close();
          }
        }

        return this;
      }
      /**
       * Called upon transport error
       *
       * @private
       */

    }, {
      key: "onError",
      value: function onError(err) {
        Socket.priorWebsocketSuccess = false;
        this.emitReserved("error", err);
        this.onClose("transport error", err);
      }
      /**
       * Called upon transport close.
       *
       * @private
       */

    }, {
      key: "onClose",
      value: function onClose(reason, description) {
        if ("opening" === this.readyState || "open" === this.readyState || "closing" === this.readyState) {
          // clear timers
          this.clearTimeoutFn(this.pingTimeoutTimer); // stop event from firing again for transport

          this.transport.removeAllListeners("close"); // ensure transport won't stay open

          this.transport.close(); // ignore further transport communication

          this.transport.removeAllListeners();

          if (typeof removeEventListener === "function") {
            removeEventListener("beforeunload", this.beforeunloadEventListener, false);
            removeEventListener("offline", this.offlineEventListener, false);
          } // set ready state


          this.readyState = "closed"; // clear session id

          this.id = null; // emit close event

          this.emitReserved("close", reason, description); // clean buffers after, so users can still
          // grab the buffers on `close` event

          this.writeBuffer = [];
          this.prevBufferLen = 0;
        }
      }
      /**
       * Filters upgrades, returning only those matching client transports.
       *
       * @param {Array} upgrades - server upgrades
       * @private
       */

    }, {
      key: "filterUpgrades",
      value: function filterUpgrades(upgrades) {
        var filteredUpgrades = [];
        var i = 0;
        var j = upgrades.length;

        for (; i < j; i++) {
          if (~this.transports.indexOf(upgrades[i])) filteredUpgrades.push(upgrades[i]);
        }

        return filteredUpgrades;
      }
    }]);

    return Socket;
  }(Emitter);
  Socket.protocol = protocol;

  var browserEntrypoint = (function (uri, opts) {
    return new Socket(uri, opts);
  });

  return browserEntrypoint;

}));
//# sourceMappingURL=engine.io.js.map
