function _createForOfIteratorHelperLoose(o, allowArrayLike) { var it = typeof Symbol !== "undefined" && o[Symbol.iterator] || o["@@iterator"]; if (it) return (it = it.call(o)).next.bind(it); if (Array.isArray(o) || (it = _unsupportedIterableToArray(o)) || allowArrayLike && o && typeof o.length === "number") { if (it) o = it; var i = 0; return function () { if (i >= o.length) return { done: true }; return { done: false, value: o[i++] }; }; } throw new TypeError("Invalid attempt to iterate non-iterable instance.\nIn order to be iterable, non-array objects must have a [Symbol.iterator]() method."); }

function _unsupportedIterableToArray(o, minLen) { if (!o) return; if (typeof o === "string") return _arrayLikeToArray(o, minLen); var n = Object.prototype.toString.call(o).slice(8, -1); if (n === "Object" && o.constructor) n = o.constructor.name; if (n === "Map" || n === "Set") return Array.from(o); if (n === "Arguments" || /^(?:Ui|I)nt(?:8|16|32)(?:Clamped)?Array$/.test(n)) return _arrayLikeToArray(o, minLen); }

function _arrayLikeToArray(arr, len) { if (len == null || len > arr.length) len = arr.length; for (var i = 0, arr2 = new Array(len); i < len; i++) { arr2[i] = arr[i]; } return arr2; }

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); Object.defineProperty(Constructor, "prototype", { writable: false }); return Constructor; }

// === Symbol Support ===
var hasSymbols = function () {
  return typeof Symbol === 'function';
};

var hasSymbol = function (name) {
  return hasSymbols() && Boolean(Symbol[name]);
};

var getSymbol = function (name) {
  return hasSymbol(name) ? Symbol[name] : '@@' + name;
};

if (hasSymbols() && !hasSymbol('observable')) {
  Symbol.observable = Symbol('observable');
}

var SymbolIterator = getSymbol('iterator');
var SymbolObservable = getSymbol('observable');
var SymbolSpecies = getSymbol('species'); // === Abstract Operations ===

function getMethod(obj, key) {
  var value = obj[key];
  if (value == null) return undefined;
  if (typeof value !== 'function') throw new TypeError(value + ' is not a function');
  return value;
}

function getSpecies(obj) {
  var ctor = obj.constructor;

  if (ctor !== undefined) {
    ctor = ctor[SymbolSpecies];

    if (ctor === null) {
      ctor = undefined;
    }
  }

  return ctor !== undefined ? ctor : Observable;
}

function isObservable(x) {
  return x instanceof Observable; // SPEC: Brand check
}

function hostReportError(e) {
  if (hostReportError.log) {
    hostReportError.log(e);
  } else {
    setTimeout(function () {
      throw e;
    });
  }
}

function enqueue(fn) {
  Promise.resolve().then(function () {
    try {
      fn();
    } catch (e) {
      hostReportError(e);
    }
  });
}

function cleanupSubscription(subscription) {
  var cleanup = subscription._cleanup;
  if (cleanup === undefined) return;
  subscription._cleanup = undefined;

  if (!cleanup) {
    return;
  }

  try {
    if (typeof cleanup === 'function') {
      cleanup();
    } else {
      var unsubscribe = getMethod(cleanup, 'unsubscribe');

      if (unsubscribe) {
        unsubscribe.call(cleanup);
      }
    }
  } catch (e) {
    hostReportError(e);
  }
}

function closeSubscription(subscription) {
  subscription._observer = undefined;
  subscription._queue = undefined;
  subscription._state = 'closed';
}

function flushSubscription(subscription) {
  var queue = subscription._queue;

  if (!queue) {
    return;
  }

  subscription._queue = undefined;
  subscription._state = 'ready';

  for (var i = 0; i < queue.length; ++i) {
    notifySubscription(subscription, queue[i].type, queue[i].value);
    if (subscription._state === 'closed') break;
  }
}

function notifySubscription(subscription, type, value) {
  subscription._state = 'running';
  var observer = subscription._observer;

  try {
    var m = getMethod(observer, type);

    switch (type) {
      case 'next':
        if (m) m.call(observer, value);
        break;

      case 'error':
        closeSubscription(subscription);
        if (m) m.call(observer, value);else throw value;
        break;

      case 'complete':
        closeSubscription(subscription);
        if (m) m.call(observer);
        break;
    }
  } catch (e) {
    hostReportError(e);
  }

  if (subscription._state === 'closed') cleanupSubscription(subscription);else if (subscription._state === 'running') subscription._state = 'ready';
}

function onNotify(subscription, type, value) {
  if (subscription._state === 'closed') return;

  if (subscription._state === 'buffering') {
    subscription._queue.push({
      type: type,
      value: value
    });

    return;
  }

  if (subscription._state !== 'ready') {
    subscription._state = 'buffering';
    subscription._queue = [{
      type: type,
      value: value
    }];
    enqueue(function () {
      return flushSubscription(subscription);
    });
    return;
  }

  notifySubscription(subscription, type, value);
}

var Subscription = /*#__PURE__*/function () {
  function Subscription(observer, subscriber) {
    // ASSERT: observer is an object
    // ASSERT: subscriber is callable
    this._cleanup = undefined;
    this._observer = observer;
    this._queue = undefined;
    this._state = 'initializing';
    var subscriptionObserver = new SubscriptionObserver(this);

    try {
      this._cleanup = subscriber.call(undefined, subscriptionObserver);
    } catch (e) {
      subscriptionObserver.error(e);
    }

    if (this._state === 'initializing') this._state = 'ready';
  }

  var _proto = Subscription.prototype;

  _proto.unsubscribe = function unsubscribe() {
    if (this._state !== 'closed') {
      closeSubscription(this);
      cleanupSubscription(this);
    }
  };

  _createClass(Subscription, [{
    key: "closed",
    get: function () {
      return this._state === 'closed';
    }
  }]);

  return Subscription;
}();

var SubscriptionObserver = /*#__PURE__*/function () {
  function SubscriptionObserver(subscription) {
    this._subscription = subscription;
  }

  var _proto2 = SubscriptionObserver.prototype;

  _proto2.next = function next(value) {
    onNotify(this._subscription, 'next', value);
  };

  _proto2.error = function error(value) {
    onNotify(this._subscription, 'error', value);
  };

  _proto2.complete = function complete() {
    onNotify(this._subscription, 'complete');
  };

  _createClass(SubscriptionObserver, [{
    key: "closed",
    get: function () {
      return this._subscription._state === 'closed';
    }
  }]);

  return SubscriptionObserver;
}();

var Observable = /*#__PURE__*/function () {
  function Observable(subscriber) {
    if (!(this instanceof Observable)) throw new TypeError('Observable cannot be called as a function');
    if (typeof subscriber !== 'function') throw new TypeError('Observable initializer must be a function');
    this._subscriber = subscriber;
  }

  var _proto3 = Observable.prototype;

  _proto3.subscribe = function subscribe(observer) {
    if (typeof observer !== 'object' || observer === null) {
      observer = {
        next: observer,
        error: arguments[1],
        complete: arguments[2]
      };
    }

    return new Subscription(observer, this._subscriber);
  };

  _proto3.forEach = function forEach(fn) {
    var _this = this;

    return new Promise(function (resolve, reject) {
      if (typeof fn !== 'function') {
        reject(new TypeError(fn + ' is not a function'));
        return;
      }

      function done() {
        subscription.unsubscribe();
        resolve();
      }

      var subscription = _this.subscribe({
        next: function (value) {
          try {
            fn(value, done);
          } catch (e) {
            reject(e);
            subscription.unsubscribe();
          }
        },
        error: reject,
        complete: resolve
      });
    });
  };

  _proto3.map = function map(fn) {
    var _this2 = this;

    if (typeof fn !== 'function') throw new TypeError(fn + ' is not a function');
    var C = getSpecies(this);
    return new C(function (observer) {
      return _this2.subscribe({
        next: function (value) {
          try {
            value = fn(value);
          } catch (e) {
            return observer.error(e);
          }

          observer.next(value);
        },
        error: function (e) {
          observer.error(e);
        },
        complete: function () {
          observer.complete();
        }
      });
    });
  };

  _proto3.filter = function filter(fn) {
    var _this3 = this;

    if (typeof fn !== 'function') throw new TypeError(fn + ' is not a function');
    var C = getSpecies(this);
    return new C(function (observer) {
      return _this3.subscribe({
        next: function (value) {
          try {
            if (!fn(value)) return;
          } catch (e) {
            return observer.error(e);
          }

          observer.next(value);
        },
        error: function (e) {
          observer.error(e);
        },
        complete: function () {
          observer.complete();
        }
      });
    });
  };

  _proto3.reduce = function reduce(fn) {
    var _this4 = this;

    if (typeof fn !== 'function') throw new TypeError(fn + ' is not a function');
    var C = getSpecies(this);
    var hasSeed = arguments.length > 1;
    var hasValue = false;
    var seed = arguments[1];
    var acc = seed;
    return new C(function (observer) {
      return _this4.subscribe({
        next: function (value) {
          var first = !hasValue;
          hasValue = true;

          if (!first || hasSeed) {
            try {
              acc = fn(acc, value);
            } catch (e) {
              return observer.error(e);
            }
          } else {
            acc = value;
          }
        },
        error: function (e) {
          observer.error(e);
        },
        complete: function () {
          if (!hasValue && !hasSeed) return observer.error(new TypeError('Cannot reduce an empty sequence'));
          observer.next(acc);
          observer.complete();
        }
      });
    });
  };

  _proto3.concat = function concat() {
    var _this5 = this;

    for (var _len = arguments.length, sources = new Array(_len), _key = 0; _key < _len; _key++) {
      sources[_key] = arguments[_key];
    }

    var C = getSpecies(this);
    return new C(function (observer) {
      var subscription;
      var index = 0;

      function startNext(next) {
        subscription = next.subscribe({
          next: function (v) {
            observer.next(v);
          },
          error: function (e) {
            observer.error(e);
          },
          complete: function () {
            if (index === sources.length) {
              subscription = undefined;
              observer.complete();
            } else {
              startNext(C.from(sources[index++]));
            }
          }
        });
      }

      startNext(_this5);
      return function () {
        if (subscription) {
          subscription.unsubscribe();
          subscription = undefined;
        }
      };
    });
  };

  _proto3.flatMap = function flatMap(fn) {
    var _this6 = this;

    if (typeof fn !== 'function') throw new TypeError(fn + ' is not a function');
    var C = getSpecies(this);
    return new C(function (observer) {
      var subscriptions = [];

      var outer = _this6.subscribe({
        next: function (value) {
          if (fn) {
            try {
              value = fn(value);
            } catch (e) {
              return observer.error(e);
            }
          }

          var inner = C.from(value).subscribe({
            next: function (value) {
              observer.next(value);
            },
            error: function (e) {
              observer.error(e);
            },
            complete: function () {
              var i = subscriptions.indexOf(inner);
              if (i >= 0) subscriptions.splice(i, 1);
              completeIfDone();
            }
          });
          subscriptions.push(inner);
        },
        error: function (e) {
          observer.error(e);
        },
        complete: function () {
          completeIfDone();
        }
      });

      function completeIfDone() {
        if (outer.closed && subscriptions.length === 0) observer.complete();
      }

      return function () {
        subscriptions.forEach(function (s) {
          return s.unsubscribe();
        });
        outer.unsubscribe();
      };
    });
  };

  _proto3[SymbolObservable] = function () {
    return this;
  };

  Observable.from = function from(x) {
    var C = typeof this === 'function' ? this : Observable;
    if (x == null) throw new TypeError(x + ' is not an object');
    var method = getMethod(x, SymbolObservable);

    if (method) {
      var observable = method.call(x);
      if (Object(observable) !== observable) throw new TypeError(observable + ' is not an object');
      if (isObservable(observable) && observable.constructor === C) return observable;
      return new C(function (observer) {
        return observable.subscribe(observer);
      });
    }

    if (hasSymbol('iterator')) {
      method = getMethod(x, SymbolIterator);

      if (method) {
        return new C(function (observer) {
          enqueue(function () {
            if (observer.closed) return;

            for (var _iterator = _createForOfIteratorHelperLoose(method.call(x)), _step; !(_step = _iterator()).done;) {
              var item = _step.value;
              observer.next(item);
              if (observer.closed) return;
            }

            observer.complete();
          });
        });
      }
    }

    if (Array.isArray(x)) {
      return new C(function (observer) {
        enqueue(function () {
          if (observer.closed) return;

          for (var i = 0; i < x.length; ++i) {
            observer.next(x[i]);
            if (observer.closed) return;
          }

          observer.complete();
        });
      });
    }

    throw new TypeError(x + ' is not observable');
  };

  Observable.of = function of() {
    for (var _len2 = arguments.length, items = new Array(_len2), _key2 = 0; _key2 < _len2; _key2++) {
      items[_key2] = arguments[_key2];
    }

    var C = typeof this === 'function' ? this : Observable;
    return new C(function (observer) {
      enqueue(function () {
        if (observer.closed) return;

        for (var i = 0; i < items.length; ++i) {
          observer.next(items[i]);
          if (observer.closed) return;
        }

        observer.complete();
      });
    });
  };

  _createClass(Observable, null, [{
    key: SymbolSpecies,
    get: function () {
      return this;
    }
  }]);

  return Observable;
}();

if (hasSymbols()) {
  Object.defineProperty(Observable, Symbol('extensions'), {
    value: {
      symbol: SymbolObservable,
      hostReportError: hostReportError
    },
    configurable: true
  });
}

export { Observable };