michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: 'use strict';
michael@0: 
michael@0: module.metadata = {
michael@0:   "stability": "stable"
michael@0: };
michael@0: 
michael@0: const { on, once, off, setListeners } = require('./core');
michael@0: const { method, chainable } = require('../lang/functional');
michael@0: const { Class } = require('../core/heritage');
michael@0: 
michael@0: /**
michael@0:  * `EventTarget` is an exemplar for creating an objects that can be used to
michael@0:  * add / remove event listeners on them. Events on these objects may be emitted
michael@0:  * via `emit` function exported by 'event/core' module.
michael@0:  */
michael@0: const EventTarget = Class({
michael@0:   /**
michael@0:    * Method initializes `this` event source. It goes through properties of a
michael@0:    * given `options` and registers listeners for the ones that look like an
michael@0:    * event listeners.
michael@0:    */
michael@0:   /**
michael@0:    * Method initializes `this` event source. It goes through properties of a
michael@0:    * given `options` and registers listeners for the ones that look like an
michael@0:    * event listeners.
michael@0:    */
michael@0:   initialize: function initialize(options) {
michael@0:     setListeners(this, options);
michael@0:   },
michael@0:   /**
michael@0:    * Registers an event `listener` that is called every time events of
michael@0:    * specified `type` are emitted.
michael@0:    * @param {String} type
michael@0:    *    The type of event.
michael@0:    * @param {Function} listener
michael@0:    *    The listener function that processes the event.
michael@0:    * @example
michael@0:    *      worker.on('message', function (data) {
michael@0:    *        console.log('data received: ' + data)
michael@0:    *      })
michael@0:    */
michael@0:   on: chainable(method(on)),
michael@0:   /**
michael@0:    * Registers an event `listener` that is called once the next time an event
michael@0:    * of the specified `type` is emitted.
michael@0:    * @param {String} type
michael@0:    *    The type of the event.
michael@0:    * @param {Function} listener
michael@0:    *    The listener function that processes the event.
michael@0:    */
michael@0:   once: chainable(method(once)),
michael@0:   /**
michael@0:    * Removes an event `listener` for the given event `type`.
michael@0:    * @param {String} type
michael@0:    *    The type of event.
michael@0:    * @param {Function} listener
michael@0:    *    The listener function that processes the event.
michael@0:    */
michael@0:   removeListener: function removeListener(type, listener) {
michael@0:     // Note: We can't just wrap `off` in `method` as we do it for other methods
michael@0:     // cause skipping a second or third argument will behave very differently
michael@0:     // than intended. This way we make sure all arguments are passed and only
michael@0:     // one listener is removed at most.
michael@0:     off(this, type, listener);
michael@0:     return this;
michael@0:   },
michael@0:   off: function(type, listener) {
michael@0:     off(this, type, listener);
michael@0:     return this;
michael@0:   }
michael@0: });
michael@0: exports.EventTarget = EventTarget;