/**
 * Copyright (c) 2015, Facebook, Inc.  All rights reserved.
 *
 * Facebook, Inc. ("Facebook") owns all right, title and interest, including
 * all intellectual property and other proprietary rights, in and to the React
 * Native CustomComponents software (the "Software").  Subject to your
 * compliance with these terms, you are hereby granted a non-exclusive,
 * worldwide, royalty-free copyright license to (1) use and copy the Software;
 * and (2) reproduce and distribute the Software as part of your own software
 * ("Your Software").  Facebook reserves all rights not expressly granted to
 * you in this license agreement.
 *
 * THE SOFTWARE AND DOCUMENTATION, IF ANY, ARE PROVIDED "AS IS" AND ANY EXPRESS
 * OR IMPLIED WARRANTIES (INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE) ARE DISCLAIMED.
 * IN NO EVENT SHALL FACEBOOK OR ITS AFFILIATES, OFFICERS, DIRECTORS OR
 * EMPLOYEES BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THE SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * @flow
 */
'use strict';

const invariant = require('fbjs/lib/invariant');

import type EventSubscription from './EventSubscription';

/**
 * EventSubscriptionVendor stores a set of EventSubscriptions that are
 * subscribed to a particular event type.
 */
class EventSubscriptionVendor {

  _subscriptionsForType: Object;
  _currentSubscription: ?EventSubscription;

  constructor() {
    this._subscriptionsForType = {};
    this._currentSubscription = null;
  }

  /**
   * Adds a subscription keyed by an event type.
   *
   * @param {string} eventType
   * @param {EventSubscription} subscription
   */
  addSubscription(
    eventType: string, subscription: EventSubscription): EventSubscription {
    invariant(
      subscription.subscriber === this,
      'The subscriber of the subscription is incorrectly set.');
    if (!this._subscriptionsForType[eventType]) {
      this._subscriptionsForType[eventType] = [];
    }
    const key = this._subscriptionsForType[eventType].length;
    this._subscriptionsForType[eventType].push(subscription);
    subscription.eventType = eventType;
    subscription.key = key;
    return subscription;
  }

  /**
   * Removes a bulk set of the subscriptions.
   *
   * @param {?string} eventType - Optional name of the event type whose
   *   registered supscriptions to remove, if null remove all subscriptions.
   */
  removeAllSubscriptions(eventType: ?string) {
    if (eventType === undefined) {
      this._subscriptionsForType = {};
    } else {
      delete this._subscriptionsForType[eventType];
    }
  }

  /**
   * Removes a specific subscription. Instead of calling this function, call
   * `subscription.remove()` directly.
   *
   * @param {object} subscription
   */
  removeSubscription(subscription: Object) {
    const eventType = subscription.eventType;
    const key = subscription.key;

    const subscriptionsForType = this._subscriptionsForType[eventType];
    if (subscriptionsForType) {
      delete subscriptionsForType[key];
    }
  }

  /**
   * Returns the array of subscriptions that are currently registered for the
   * given event type.
   *
   * Note: This array can be potentially sparse as subscriptions are deleted
   * from it when they are removed.
   *
   * TODO: This returns a nullable array. wat?
   *
   * @param {string} eventType
   * @returns {?array}
   */
  getSubscriptionsForType(eventType: string): ?[EventSubscription] {
   return this._subscriptionsForType[eventType];
  }
}

module.exports = EventSubscriptionVendor;