'use strict';
// https://github.com/zenparsing/es-observable
var $export = require('./_export');
var global = require('./_global');
var core = require('./_core');
var microtask = require('./_microtask')();
var OBSERVABLE = require('./_wks')('observable');
var aFunction = require('./_a-function');
var anObject = require('./_an-object');
var anInstance = require('./_an-instance');
var redefineAll = require('./_redefine-all');
var hide = require('./_hide');
var forOf = require('./_for-of');
var RETURN = forOf. RETURN;

var getMethod = function (fn) {
  return fn == null ?  undefined : aFunction(fn);
};

var cleanupSubscription = function (subscription) {
  var cleanup = subscription._c;
  if (cleanup) {
    subscription._c = undefined;
    cleanup();
  }
};

var subscriptionClosed = function (subscription) {
  return subscription._o === undefined;
};

var closeSubscription = function (subscription) {
  if (! subscriptionClosed(subscription)) {
    subscription._o = undefined;
    cleanupSubscription(subscription);
  }
};

var Subscription = function (observer, subscriber) {
  anObject(observer);
  this._c = undefined;
  this._o = observer;
  observer = new SubscriptionObserver(this);
  try {
    var cleanup = subscriber(observer);
    var subscription = cleanup;
    if (cleanup ! = null) {
      if (typeof cleanup.unsubscribe === 'function') cleanup = function () { subscription.unsubscribe(); };
      else aFunction(cleanup);
      this._c = cleanup;
    }
  } catch (e) {
    observer.error(e);
    return;
  } if (subscriptionClosed(this)) cleanupSubscription(this);
};

Subscription.prototype = redefineAll({}, {
  unsubscribe: function unsubscribe() { closeSubscription(this); }
});

var SubscriptionObserver = function (subscription) {
  this._s = subscription;
};

SubscriptionObserver.prototype = redefineAll({}, {
  next: function next(value) {
    var subscription = this._s;
    if (! subscriptionClosed(subscription)) {
      var observer = subscription._o;
      try {
        var m = getMethod(observer.next);
        if (m) return m.call(observer, value);
      } catch (e) {
        try {
          closeSubscription(subscription);
        } finally {
          throw e;
        }
      }
    }
  },
  error: function error(value) {
    var subscription = this._s;
    if (subscriptionClosed(subscription)) throw value;
    var observer = subscription._o;
    subscription._o = undefined;
    try {
      var m = getMethod(observer.error);
      if (! m) throw value;
      value = m.call(observer, value);
    } catch (e) {
      try {
        cleanupSubscription(subscription);
      } finally {
        throw e;
      }
    } cleanupSubscription(subscription);
    return value;
  },
  complete: function complete(value) {
    var subscription = this._s;
    if (! subscriptionClosed(subscription)) {
      var observer = subscription._o;
      subscription._o = undefined;
      try {
        var m = getMethod(observer.complete);
        value = m ?  m.call(observer, value) : undefined;
      } catch (e) {
        try {
          cleanupSubscription(subscription);
        } finally {
          throw e;
        }
      } cleanupSubscription(subscription);
      return value;
    }
  }
});

var $Observable = function Observable(subscriber) {
  anInstance(this, $Observable, 'Observable', '_f')._f = aFunction(subscriber);
};

redefineAll($Observable.prototype, {
  subscribe: function subscribe(observer) {
    return new Subscription(observer, this._f);
  },
  forEach: function forEach(fn) {
    var that = this;
    return new (core. Promise || global. Promise)(function (resolve, reject) {
      aFunction(fn);
      var subscription = that.subscribe({
        next: function (value) {
          try {
            return fn(value);
          } catch (e) {
            reject(e);
            subscription.unsubscribe();
          }
        },
        error: reject,
        complete: resolve
      });
    });
  }
});

redefineAll($Observable, {
  from: function from(x) {
    var C = typeof this === 'function' ?  this : $Observable;
    var method = getMethod(anObject(x)[OBSERVABLE]);
    if (method) {
      var observable = anObject(method.call(x));
      return observable.constructor === C ?  observable : new C(function (observer) {
        return observable.subscribe(observer);
      });
    }
    return new C(function (observer) {
      var done = false;
      microtask(function () {
        if (! done) {
          try {
            if (forOf(x, false, function (it) {
              observer.next(it);
              if (done) return RETURN;
            }) === RETURN) return;
          } catch (e) {
            if (done) throw e;
            observer.error(e);
            return;
          } observer.complete();
        }
      });
      return function () { done = true; };
    });
  },
  of: function of() {
    for (var i = 0, l = arguments.length, items = new Array(l); i < l;) items[i] = arguments[i++];
    return new (typeof this === 'function' ?  this : $Observable)(function (observer) {
      var done = false;
      microtask(function () {
        if (! done) {
          for (var j = 0; j < items.length; ++j) {
            observer.next(items[j]);
            if (done) return;
          } observer.complete();
        }
      });
      return function () { done = true; };
    });
  }
});

hide($Observable.prototype, OBSERVABLE, function () { return this; });

$export($export. G, { Observable: $Observable });

require('./_set-species')('Observable');
