'use strict';

var domain;

// This constructor is used to store event handlers. Instantiating this is
// faster than explicitly calling `Object.create(null)` to get a "clean" empty
// object (tested with v8 v4.9).

const kRejection = Symbol.for("nodejs.rejection");


function EventHandlers() { }
EventHandlers.prototype = Object.create(null);

function EventEmitter() {
  EventEmitter.init.call(this);
}

const captureRejectionSymbol = EventEmitter.captureRejectionSymbol;
EventEmitter.captureRejectionSymbol = kRejection;

export default EventEmitter;
export { EventEmitter, captureRejectionSymbol };

// nodejs oddity
// require('events') === require('events').EventEmitter
EventEmitter.EventEmitter = EventEmitter

EventEmitter.usingDomains = false;

EventEmitter.prototype.domain = undefined;
EventEmitter.prototype._events = undefined;
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.
EventEmitter.defaultMaxListeners = 10;

EventEmitter.init = function () {
  this.domain = null;
  if (EventEmitter.usingDomains) {
    // if there is an active domain, then attach to it.
    if (domain.active && !(this instanceof domain.Domain)) {
      this.domain = domain.active;
    }
  }

  if (!this._events || this._events === Object.getPrototypeOf(this)._events) {
    this._events = new EventHandlers();
    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 || isNaN(n))
    throw new TypeError('"n" argument must be a positive number');
  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);
};

// These standalone emit* functions are used to optimize calling of event
// handlers for fast cases because emit() itself often has a variable number of
// arguments and can be deoptimized because of that. These functions always have
// the same number of arguments and thus do not get deoptimized, so the code
// inside them can execute faster.
function emitNone(handler, isFn, self) {
  if (isFn)
    handler.call(self);
  else {
    var len = handler.length;
    var listeners = arrayClone(handler, len);
    for (var i = 0; i < len; ++i)
      listeners[i].call(self);
  }
}
function emitOne(handler, isFn, self, arg1) {
  if (isFn)
    handler.call(self, arg1);
  else {
    var len = handler.length;
    var listeners = arrayClone(handler, len);
    for (var i = 0; i < len; ++i)
      listeners[i].call(self, arg1);
  }
}
function emitTwo(handler, isFn, self, arg1, arg2) {
  if (isFn)
    handler.call(self, arg1, arg2);
  else {
    var len = handler.length;
    var listeners = arrayClone(handler, len);
    for (var i = 0; i < len; ++i)
      listeners[i].call(self, arg1, arg2);
  }
}
function emitThree(handler, isFn, self, arg1, arg2, arg3) {
  if (isFn)
    handler.call(self, arg1, arg2, arg3);
  else {
    var len = handler.length;
    var listeners = arrayClone(handler, len);
    for (var i = 0; i < len; ++i)
      listeners[i].call(self, arg1, arg2, arg3);
  }
}

function emitMany(handler, isFn, self, args) {
  if (isFn)
    handler.apply(self, args);
  else {
    var len = handler.length;
    var listeners = arrayClone(handler, len);
    for (var i = 0; i < len; ++i)
      listeners[i].apply(self, args);
  }
}

EventEmitter.prototype.emit = function emit(type) {
  var er, handler, len, args, i, events, domain;
  var needDomainExit = false;
  var doError = (type === 'error');

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

  domain = this.domain;

  // If there is no 'error' event listener then throw.
  if (doError) {
    er = arguments[1];
    if (domain) {
      if (!er)
        er = new Error('Uncaught, unspecified "error" event');
      er.domainEmitter = this;
      er.domain = domain;
      er.domainThrown = false;
      domain.emit('error', er);
    } else if (er instanceof Error) {
      throw er; // Unhandled 'error' event
    } else {
      // At least give some kind of context to the user
      var err = new Error('Uncaught, unspecified "error" event. (' + er + ')');
      err.context = er;
      throw err;
    }
    return false;
  }

  handler = events[type];

  if (!handler)
    return false;

  var isFn = typeof handler === 'function';
  len = arguments.length;
  switch (len) {
    // fast cases
    case 1:
      emitNone(handler, isFn, this);
      break;
    case 2:
      emitOne(handler, isFn, this, arguments[1]);
      break;
    case 3:
      emitTwo(handler, isFn, this, arguments[1], arguments[2]);
      break;
    case 4:
      emitThree(handler, isFn, this, arguments[1], arguments[2], arguments[3]);
      break;
    // slower
    default:
      args = new Array(len - 1);
      for (i = 1; i < len; i++)
        args[i - 1] = arguments[i];
      emitMany(handler, isFn, this, args);
  }

  if (needDomainExit)
    domain.exit();

  return true;
};

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

  if (typeof listener !== 'function')
    throw new TypeError('"listener" argument must be a function');

  events = target._events;
  if (!events) {
    events = target._events = new EventHandlers();
    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) {
      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) {
    // 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];
    } else {
      // If we've already got an array, just append.
      if (prepend) {
        existing.unshift(listener);
      } else {
        existing.push(listener);
      }
    }

    // Check for listener leak
    if (!existing.warned) {
      m = $getMaxListeners(target);
      if (m && m > 0 && existing.length > m) {
        existing.warned = true;
        var w = new Error('Possible EventEmitter memory leak detected. ' +
          existing.length + ' ' + type + ' listeners added. ' +
          'Use emitter.setMaxListeners() to increase limit');
        w.name = 'MaxListenersExceededWarning';
        w.emitter = target;
        w.type = type;
        w.count = existing.length;
        emitWarning(w);
      }
    }
  }

  return target;
}
function emitWarning(e) {
  typeof console.warn === 'function' ? console.warn(e) : console.log(e);
}
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 _onceWrap(target, type, listener) {
  var fired = false;
  function g() {
    target.removeListener(type, g);
    if (!fired) {
      fired = true;
      listener.apply(target, arguments);
    }
  }
  g.listener = listener;
  return g;
}

EventEmitter.prototype.once = function once(type, listener) {
  if (typeof listener !== 'function')
    throw new TypeError('"listener" argument must be a function');
  this.on(type, _onceWrap(this, type, listener));
  return this;
};

EventEmitter.prototype.prependOnceListener =
  function prependOnceListener(type, listener) {
    if (typeof listener !== 'function')
      throw new TypeError('"listener" argument must be a function');
    this.prependListener(type, _onceWrap(this, type, listener));
    return this;
  };

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

    if (typeof listener !== 'function')
      throw new TypeError('"listener" argument must be a function');

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

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

    if (list === listener || (list.listener && list.listener === listener)) {
      if (--this._eventsCount === 0)
        this._events = new EventHandlers();
      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; i-- > 0;) {
        if (list[i] === listener ||
          (list[i].listener && list[i].listener === listener)) {
          originalListener = list[i].listener;
          position = i;
          break;
        }
      }

      if (position < 0)
        return this;

      if (list.length === 1) {
        list[0] = undefined;
        if (--this._eventsCount === 0) {
          this._events = new EventHandlers();
          return this;
        } else {
          delete events[type];
        }
      } else {
        spliceOne(list, position);
      }

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

    return this;
  };

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

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

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

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

    listeners = events[type];

    if (typeof listeners === 'function') {
      this.removeListener(type, listeners);
    } else if (listeners) {
      // LIFO order
      do {
        this.removeListener(type, listeners[listeners.length - 1]);
      } while (listeners[0]);
    }

    return this;
  };

EventEmitter.prototype.listeners = function listeners(type) {
  var evlistener;
  var ret;
  var events = this._events;

  if (!events)
    ret = [];
  else {
    evlistener = events[type];
    if (!evlistener)
      ret = [];
    else if (typeof evlistener === 'function')
      ret = [evlistener.listener || evlistener];
    else
      ret = unwrapListeners(evlistener);
  }

  return ret;
};

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

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

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

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

  return 0;
}

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

// About 1.5x faster than the two-arg version of Array#splice().
function spliceOne(list, index) {
  for (var i = index, k = i + 1, n = list.length; k < n; i += 1, k += 1)
    list[i] = list[k];
  list.pop();
}

function arrayClone(arr, i) {
  var copy = new Array(i);
  while (i--)
    copy[i] = arr[i];
  return copy;
}

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;
}

/**
 * Creates a `Promise` that is fulfilled when the emitter
 * emits the given event.
 * @param {EventEmitter} emitter
 * @param {string} name
 * @param {{ signal: AbortSignal; }} [options]
 * @returns {Promise}
 */
export async function once(emitter, name, options = kEmptyObject) {
  const signal = options?.signal;
  validateAbortSignal(signal, 'options.signal');
  if (signal?.aborted)
    throw new AbortError(undefined, { cause: signal?.reason });
  return new Promise((resolve, reject) => {
    const errorListener = (err) => {
      emitter.removeListener(name, resolver);
      if (signal != null) {
        eventTargetAgnosticRemoveListener(signal, 'abort', abortListener);
      }
      reject(err);
    };
    const resolver = (...args) => {
      if (typeof emitter.removeListener === 'function') {
        emitter.removeListener('error', errorListener);
      }
      if (signal != null) {
        eventTargetAgnosticRemoveListener(signal, 'abort', abortListener);
      }
      resolve(args);
    };
    eventTargetAgnosticAddListener(emitter, name, resolver, { once: true });
    if (name !== 'error' && typeof emitter.once === 'function') {
      // EventTarget does not have `error` event semantics like Node
      // EventEmitters, we listen to `error` events only on EventEmitters.
      emitter.once('error', errorListener);
    }
    function abortListener() {
      eventTargetAgnosticRemoveListener(emitter, name, resolver);
      eventTargetAgnosticRemoveListener(emitter, 'error', errorListener);
      reject(new AbortError(undefined, { cause: signal?.reason }));
    }
    if (signal != null) {
      eventTargetAgnosticAddListener(
        signal, 'abort', abortListener, { once: true });
    }
  });
}