'use strict';
// https://github.com/tc39/proposal-observable
var $ = require('../internals/export');
var call = require('../internals/function-call');
var DESCRIPTORS = require('../internals/descriptors');
var setSpecies = require('../internals/set-species');
var aCallable = require('../internals/a-callable');
var isCallable = require('../internals/is-callable');
var anObject = require('../internals/an-object');
var isObject = require('../internals/is-object');
var anInstance = require('../internals/an-instance');
var getMethod = require('../internals/get-method');
var defineProperty = require('../internals/object-define-property').f;
var redefine = require('../internals/redefine');
var redefineAll = require('../internals/redefine-all');
var hostReportErrors = require('../internals/host-report-errors');
var wellKnownSymbol = require('../internals/well-known-symbol');
var InternalStateModule = require('../internals/internal-state');
var OBSERVABLE_FORCED = require('../internals/observable-forced');

var $$OBSERVABLE = wellKnownSymbol('observable');
var OBSERVABLE = 'Observable';
var SUBSCRIPTION = 'Subscription';
var SUBSCRIPTION_OBSERVER = 'SubscriptionObserver';
var getterFor = InternalStateModule.getterFor;
var setInternalState = InternalStateModule.set;
var getObservableInternalState = getterFor(OBSERVABLE);
var getSubscriptionInternalState = getterFor(SUBSCRIPTION);
var getSubscriptionObserverInternalState = getterFor(SUBSCRIPTION_OBSERVER);

var SubscriptionState = function (observer) {
  this.observer = anObject(observer);
  this.cleanup = undefined;
  this.subscriptionObserver = undefined;
};

SubscriptionState.prototype = {
  type: SUBSCRIPTION,
  clean: function () {
    var cleanup = this.cleanup;
    if (cleanup) {
      this.cleanup = undefined;
      try {
        cleanup();
      } catch (error) {
        hostReportErrors(error);
      }
    }
  },
  close: function () {
    if (!DESCRIPTORS) {
      var subscription = this.facade;
      var subscriptionObserver = this.subscriptionObserver;
      subscription.closed = true;
      if (subscriptionObserver) subscriptionObserver.closed = true;
    } this.observer = undefined;
  },
  isClosed: function () {
    return this.observer === undefined;
  }
};

var Subscription = function (observer, subscriber) {
  var subscriptionState = setInternalState(this, new SubscriptionState(observer));
  var start;
  if (!DESCRIPTORS) this.closed = false;
  try {
    if (start = getMethod(observer, 'start')) call(start, observer, this);
  } catch (error) {
    hostReportErrors(error);
  }
  if (subscriptionState.isClosed()) return;
  var subscriptionObserver = subscriptionState.subscriptionObserver = new SubscriptionObserver(subscriptionState);
  try {
    var cleanup = subscriber(subscriptionObserver);
    var subscription = cleanup;
    if (cleanup != null) subscriptionState.cleanup = isCallable(cleanup.unsubscribe)
      ? function () { subscription.unsubscribe(); }
      : aCallable(cleanup);
  } catch (error) {
    subscriptionObserver.error(error);
    return;
  } if (subscriptionState.isClosed()) subscriptionState.clean();
};

Subscription.prototype = redefineAll({}, {
  unsubscribe: function unsubscribe() {
    var subscriptionState = getSubscriptionInternalState(this);
    if (!subscriptionState.isClosed()) {
      subscriptionState.close();
      subscriptionState.clean();
    }
  }
});

if (DESCRIPTORS) defineProperty(Subscription.prototype, 'closed', {
  configurable: true,
  get: function () {
    return getSubscriptionInternalState(this).isClosed();
  }
});

var SubscriptionObserver = function (subscriptionState) {
  setInternalState(this, {
    type: SUBSCRIPTION_OBSERVER,
    subscriptionState: subscriptionState
  });
  if (!DESCRIPTORS) this.closed = false;
};

SubscriptionObserver.prototype = redefineAll({}, {
  next: function next(value) {
    var subscriptionState = getSubscriptionObserverInternalState(this).subscriptionState;
    if (!subscriptionState.isClosed()) {
      var observer = subscriptionState.observer;
      try {
        var nextMethod = getMethod(observer, 'next');
        if (nextMethod) call(nextMethod, observer, value);
      } catch (error) {
        hostReportErrors(error);
      }
    }
  },
  error: function error(value) {
    var subscriptionState = getSubscriptionObserverInternalState(this).subscriptionState;
    if (!subscriptionState.isClosed()) {
      var observer = subscriptionState.observer;
      subscriptionState.close();
      try {
        var errorMethod = getMethod(observer, 'error');
        if (errorMethod) call(errorMethod, observer, value);
        else hostReportErrors(value);
      } catch (err) {
        hostReportErrors(err);
      } subscriptionState.clean();
    }
  },
  complete: function complete() {
    var subscriptionState = getSubscriptionObserverInternalState(this).subscriptionState;
    if (!subscriptionState.isClosed()) {
      var observer = subscriptionState.observer;
      subscriptionState.close();
      try {
        var completeMethod = getMethod(observer, 'complete');
        if (completeMethod) call(completeMethod, observer);
      } catch (error) {
        hostReportErrors(error);
      } subscriptionState.clean();
    }
  }
});

if (DESCRIPTORS) defineProperty(SubscriptionObserver.prototype, 'closed', {
  configurable: true,
  get: function () {
    return getSubscriptionObserverInternalState(this).subscriptionState.isClosed();
  }
});

var $Observable = function Observable(subscriber) {
  anInstance(this, ObservablePrototype);
  setInternalState(this, {
    type: OBSERVABLE,
    subscriber: aCallable(subscriber)
  });
};

var ObservablePrototype = $Observable.prototype;

redefineAll(ObservablePrototype, {
  subscribe: function subscribe(observer) {
    var length = arguments.length;
    return new Subscription(isCallable(observer) ? {
      next: observer,
      error: length > 1 ? arguments[1] : undefined,
      complete: length > 2 ? arguments[2] : undefined
    } : isObject(observer) ? observer : {}, getObservableInternalState(this).subscriber);
  }
});

redefine(ObservablePrototype, $$OBSERVABLE, function () { return this; });

$({ global: true, forced: OBSERVABLE_FORCED }, {
  Observable: $Observable
});

setSpecies(OBSERVABLE);