events.js

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

/* eslint-disable no-underscore-dangle, vars-on-top */

'use strict';

var R = typeof Reflect === 'object' ? Reflect : null;
var ReflectApply = R && typeof R.apply === 'function'
  ? R.apply
  : function ReflectApply(target, receiver, args) {
    return Function.prototype.apply.call(target, receiver, args);
  };

var ReflectOwnKeys;
if (R && typeof R.ownKeys === 'function') {
  ReflectOwnKeys = R.ownKeys;
} else if (Object.getOwnPropertySymbols) {
  ReflectOwnKeys = function (target) {
    return Object.getOwnPropertyNames(target)
      .concat(Object.getOwnPropertySymbols(target));
  };
} else {
  ReflectOwnKeys = function (target) {
    return Object.getOwnPropertyNames(target);
  };
}

function ProcessEmitWarning(warning) {
  if (console && console.warn) console.warn(warning);
}

var NumberIsNaN = Number.isNaN || function NumberIsNaN(value) {
  return value !== value;
};

function EventEmitter() {
  EventEmitter.init.call(this);
}
module.exports = EventEmitter;
module.exports.once = once;

// Backwards-compat with node 0.10.x
EventEmitter.EventEmitter = EventEmitter;

EventEmitter.prototype._events = undefined;
EventEmitter.prototype._eventsCount = 0;
EventEmitter.prototype._maxListeners = undefined;

// By default EventEmitters will print a warning if more than 10 listeners are
// added to it. This is a useful default which helps finding memory leaks.
var defaultMaxListeners = 10;

function checkListener(listener) {
  if (typeof listener !== 'function') {
    throw new TypeError('The "listener" argument must be of type Function. Received type ' + typeof listener);
  }
}

Object.defineProperty(EventEmitter, 'defaultMaxListeners', {
  enumerable: true,
  get: function () {
    return defaultMaxListeners;
  },
  set: function (arg) {
    if (typeof arg !== 'number' || arg < 0 || NumberIsNaN(arg)) {
      throw new RangeError('The value of "defaultMaxListeners" is out of range. It must be a non-negative number. Received ' + arg + '.');
    }
    defaultMaxListeners = arg;
  }
});

EventEmitter.init = function init() {
  if (this._events === undefined
    || this._events === Object.getPrototypeOf(this)._events) {
    this._events = Object.create(null);
    this._eventsCount = 0;
  }

  this._maxListeners = this._maxListeners || undefined;
};

// Obviously not all Emitters should be limited to 10. This function allows
// that to be increased. Set to zero for unlimited.
EventEmitter.prototype.setMaxListeners = function setMaxListeners(n) {
  if (typeof n !== 'number' || n < 0 || NumberIsNaN(n)) {
    throw new RangeError('The value of "n" is out of range. It must be a non-negative number. Received ' + n + '.');
  }
  this._maxListeners = n;
  return this;
};

function _getMaxListeners(that) {
  if (that._maxListeners === undefined) return EventEmitter.defaultMaxListeners;
  return that._maxListeners;
}

EventEmitter.prototype.getMaxListeners = function getMaxListeners() {
  return _getMaxListeners(this);
};

EventEmitter.prototype.emit = function emit(type) {
  var args = [];
  for (var i = 1; i < arguments.length; i++) args.push(arguments[i]);
  var doError = (type === 'error');

  var events = this._events;
  if (events !== undefined) doError = (doError && events.error === undefined);
  else if (!doError) return false;

  // If there is no 'error' event listener then throw.
  if (doError) {
    var er;
    if (args.length > 0) er = args[0];
    if (er instanceof Error) {
      // Note: The comments on the `throw` lines are intentional, they show
      // up in Node's output if this results in an unhandled exception.
      throw er; // Unhandled 'error' event
    }
    // At least give some kind of context to the user
    var err = new Error('Unhandled error.' + (er ? ' (' + er.message + ')' : ''));
    err.context = er;
    throw err; // Unhandled 'error' event
  }

  var handler = events[type];

  if (handler === undefined) return false;

  if (typeof handler === 'function') {
    ReflectApply(handler, this, args);
  } else {
    var len = handler.length;
    var listeners = arrayClone(handler, len);
    for (var i = 0; i < len; ++i) ReflectApply(listeners[i], this, args);
  }

  return true;
};

function _addListener(target, type, listener, prepend) {
  var m;
  var events;
  var existing;

  checkListener(listener);

  events = target._events;
  if (events === undefined) {
    events = target._events = Object.create(null);
    target._eventsCount = 0;
  } else {
    // To avoid recursion in the case that type === "newListener"! Before
    // adding it to the listeners, first emit "newListener".
    if (events.newListener !== undefined) {
      target.emit('newListener', type,
        listener.listener ? listener.listener : listener);

      // Re-assign `events` because a newListener handler could have caused the
      // this._events to be assigned to a new object
      events = target._events;
    }
    existing = events[type];
  }

  if (existing === undefined) {
    // Optimize the case of one listener. Don't need the extra array object.
    existing = events[type] = listener;
    ++target._eventsCount;
  } else {
    if (typeof existing === 'function') {
      // Adding the second element, need to change to array.
      existing = events[type] = prepend ? [listener, existing] : [existing, listener];
      // If we've already got an array, just append.
    } else if (prepend) {
      existing.unshift(listener);
    } else {
      existing.push(listener);
    }

    // Check for listener leak
    m = _getMaxListeners(target);
    if (m > 0 && existing.length > m && !existing.warned) {
      existing.warned = true;
      // No error code for this since it is a Warning
      // eslint-disable-next-line no-restricted-syntax
      var w = new Error('Possible EventEmitter memory leak detected. '
        + existing.length + ' ' + String(type) + ' listeners '
        + 'added. Use emitter.setMaxListeners() to '
        + 'increase limit');
      w.name = 'MaxListenersExceededWarning';
      w.emitter = target;
      w.type = type;
      w.count = existing.length;
      ProcessEmitWarning(w);
    }
  }

  return target;
}

EventEmitter.prototype.addListener = function addListener(type, listener) {
  return _addListener(this, type, listener, false);
};

EventEmitter.prototype.on = EventEmitter.prototype.addListener;

EventEmitter.prototype.prependListener = function prependListener(type, listener) {
  return _addListener(this, type, listener, true);
};

function onceWrapper() {
  if (!this.fired) {
    this.target.removeListener(this.type, this.wrapFn);
    this.fired = true;
    if (arguments.length === 0) return this.listener.call(this.target);
    return this.listener.apply(this.target, arguments);
  }
}

function _onceWrap(target, type, listener) {
  var state = { fired: false, wrapFn: undefined, target: target, type: type, listener: listener };
  var wrapped = onceWrapper.bind(state);
  wrapped.listener = listener;
  state.wrapFn = wrapped;
  return wrapped;
}

EventEmitter.prototype.once = function once(type, listener) {
  checkListener(listener);
  this.on(type, _onceWrap(this, type, listener));
  return this;
};

EventEmitter.prototype.prependOnceListener = function prependOnceListener(type, listener) {
  checkListener(listener);
  this.prependListener(type, _onceWrap(this, type, listener));
  return this;
};

// Emits a 'removeListener' event if and only if the listener was removed.
EventEmitter.prototype.removeListener = function removeListener(type, listener) {
  var list;
  var events;
  var position;
  var i;
  var originalListener;

  checkListener(listener);

  events = this._events;
  if (events === undefined) return this;

  list = events[type];
  if (list === undefined) return this;

  if (list === listener || list.listener === listener) {
    if (--this._eventsCount === 0) this._events = Object.create(null);
    else {
      delete events[type];
      if (events.removeListener) this.emit('removeListener', type, list.listener || listener);
    }
  } else if (typeof list !== 'function') {
    position = -1;

    for (i = list.length - 1; i >= 0; i--) {
      if (list[i] === listener || list[i].listener === listener) {
        originalListener = list[i].listener;
        position = i;
        break;
      }
    }

    if (position < 0) return this;

    if (position === 0) list.shift();
    else {
      spliceOne(list, position);
    }

    if (list.length === 1) events[type] = list[0];

    if (events.removeListener !== undefined) this.emit('removeListener', type, originalListener || listener);
  }

  return this;
};

EventEmitter.prototype.removeAllListeners = function removeAllListeners(type) {
  var listeners;
  var events;
  var i;

  events = this._events;
  if (events === undefined) return this;

  // not listening for removeListener, no need to emit
  if (events.removeListener === undefined) {
    if (arguments.length === 0) {
      this._events = Object.create(null);
      this._eventsCount = 0;
    } else if (events[type] !== undefined) {
      if (--this._eventsCount === 0) this._events = Object.create(null);
      else delete events[type];
    }
    return this;
  }

  // emit removeListener for all listeners on all events
  if (arguments.length === 0) {
    var keys = Object.keys(events);
    var key;
    for (i = 0; i < keys.length; ++i) {
      key = keys[i];
      if (key === 'removeListener') continue;
      this.removeAllListeners(key);
    }
    this.removeAllListeners('removeListener');
    this._events = Object.create(null);
    this._eventsCount = 0;
    return this;
  }

  listeners = events[type];

  if (typeof listeners === 'function') {
    this.removeListener(type, listeners);
  } else if (listeners !== undefined) {
    // LIFO order
    for (i = listeners.length - 1; i >= 0; i--) {
      this.removeListener(type, listeners[i]);
    }
  }

  return this;
};

EventEmitter.prototype.off = EventEmitter.prototype.removeListener;

EventEmitter.prototype.offAll = EventEmitter.prototype.removeAllListeners;

function _listeners(target, type, unwrap) {
  var events = target._events;

  if (events === undefined) return [];

  var evlistener = events[type];
  if (evlistener === undefined) return [];

  if (typeof evlistener === 'function') return unwrap ? [evlistener.listener || evlistener] : [evlistener];

  return unwrap ? unwrapListeners(evlistener) : arrayClone(evlistener, evlistener.length);
}

EventEmitter.prototype.listeners = function listeners(type) {
  return _listeners(this, type, true);
};

EventEmitter.prototype.rawListeners = function rawListeners(type) {
  return _listeners(this, type, false);
};

EventEmitter.listenerCount = function (emitter, type) {
  if (typeof emitter.listenerCount === 'function') {
    return emitter.listenerCount(type);
  }
  return listenerCount.call(emitter, type);
};

EventEmitter.prototype.listenerCount = listenerCount;

function listenerCount(type) {
  var events = this._events;

  if (events !== undefined) {
    var evlistener = events[type];

    if (typeof evlistener === 'function') {
      return 1;
    } if (evlistener !== undefined) {
      return evlistener.length;
    }
  }

  return 0;
}

EventEmitter.prototype.eventNames = function eventNames() {
  return this._eventsCount > 0 ? ReflectOwnKeys(this._events) : [];
};

function arrayClone(arr, n) {
  var copy = new Array(n);
  for (var i = 0; i < n; ++i) copy[i] = arr[i];
  return copy;
}

function spliceOne(list, index) {
  for (; index + 1 < list.length; index++) list[index] = list[index + 1];
  list.pop();
}

function unwrapListeners(arr) {
  var ret = new Array(arr.length);
  for (var i = 0; i < ret.length; ++i) {
    ret[i] = arr[i].listener || arr[i];
  }
  return ret;
}

function once(emitter, name) {
  return new Promise(function oncep(resolve, reject) {
    function eventListener() {
      if (errorListener !== undefined) {
        emitter.removeListener('error', errorListener);
      }
      resolve([].slice.call(arguments));
    }
    var errorListener;

    // Adding an error listener is not optional because
    // if an error is thrown on an event emitter we cannot
    // guarantee that the actual event we are waiting will
    // be fired. The result could be a silent way to create
    // memory or file descriptor leaks, which is something
    // we should avoid.
    if (name !== 'error') {
      errorListener = function errorListener(err) {
        emitter.removeListener(name, eventListener);
        reject(err);
      };

      emitter.once('error', errorListener);
    }

    emitter.once(name, eventListener);
  });
}