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: /**
michael@0:  * EventEmitter.
michael@0:  */
michael@0: 
michael@0: this.EventEmitter = function EventEmitter() {};
michael@0: 
michael@0: if (typeof(require) === "function") {
michael@0:    module.exports = EventEmitter;
michael@0:    var {Cu, components} = require("chrome");
michael@0: } else {
michael@0:   var EXPORTED_SYMBOLS = ["EventEmitter"];
michael@0:   var Cu = this["Components"].utils;
michael@0:   var components = Components;
michael@0: }
michael@0: 
michael@0: const { Promise: promise } = Cu.import("resource://gre/modules/Promise.jsm", {});
michael@0: const { Services } = Cu.import("resource://gre/modules/Services.jsm");
michael@0: 
michael@0: /**
michael@0:  * Decorate an object with event emitter functionality.
michael@0:  *
michael@0:  * @param Object aObjectToDecorate
michael@0:  *        Bind all public methods of EventEmitter to
michael@0:  *        the aObjectToDecorate object.
michael@0:  */
michael@0: EventEmitter.decorate = function EventEmitter_decorate (aObjectToDecorate) {
michael@0:   let emitter = new EventEmitter();
michael@0:   aObjectToDecorate.on = emitter.on.bind(emitter);
michael@0:   aObjectToDecorate.off = emitter.off.bind(emitter);
michael@0:   aObjectToDecorate.once = emitter.once.bind(emitter);
michael@0:   aObjectToDecorate.emit = emitter.emit.bind(emitter);
michael@0: };
michael@0: 
michael@0: EventEmitter.prototype = {
michael@0:   /**
michael@0:    * Connect a listener.
michael@0:    *
michael@0:    * @param string aEvent
michael@0:    *        The event name to which we're connecting.
michael@0:    * @param function aListener
michael@0:    *        Called when the event is fired.
michael@0:    */
michael@0:   on: function EventEmitter_on(aEvent, aListener) {
michael@0:     if (!this._eventEmitterListeners)
michael@0:       this._eventEmitterListeners = new Map();
michael@0:     if (!this._eventEmitterListeners.has(aEvent)) {
michael@0:       this._eventEmitterListeners.set(aEvent, []);
michael@0:     }
michael@0:     this._eventEmitterListeners.get(aEvent).push(aListener);
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Listen for the next time an event is fired.
michael@0:    *
michael@0:    * @param string aEvent
michael@0:    *        The event name to which we're connecting.
michael@0:    * @param function aListener
michael@0:    *        (Optional) Called when the event is fired. Will be called at most
michael@0:    *        one time.
michael@0:    * @return promise
michael@0:    *        A promise which is resolved when the event next happens. The
michael@0:    *        resolution value of the promise is the first event argument. If
michael@0:    *        you need access to second or subsequent event arguments (it's rare
michael@0:    *        that this is needed) then use aListener
michael@0:    */
michael@0:   once: function EventEmitter_once(aEvent, aListener) {
michael@0:     let deferred = promise.defer();
michael@0: 
michael@0:     let handler = function(aEvent, aFirstArg) {
michael@0:       this.off(aEvent, handler);
michael@0:       if (aListener) {
michael@0:         aListener.apply(null, arguments);
michael@0:       }
michael@0:       deferred.resolve(aFirstArg);
michael@0:     }.bind(this);
michael@0: 
michael@0:     handler._originalListener = aListener;
michael@0:     this.on(aEvent, handler);
michael@0: 
michael@0:     return deferred.promise;
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Remove a previously-registered event listener.  Works for events
michael@0:    * registered with either on or once.
michael@0:    *
michael@0:    * @param string aEvent
michael@0:    *        The event name whose listener we're disconnecting.
michael@0:    * @param function aListener
michael@0:    *        The listener to remove.
michael@0:    */
michael@0:   off: function EventEmitter_off(aEvent, aListener) {
michael@0:     if (!this._eventEmitterListeners)
michael@0:       return;
michael@0:     let listeners = this._eventEmitterListeners.get(aEvent);
michael@0:     if (listeners) {
michael@0:       this._eventEmitterListeners.set(aEvent, listeners.filter(l => {
michael@0:         return l !== aListener && l._originalListener !== aListener;
michael@0:       }));
michael@0:     }
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Emit an event.  All arguments to this method will
michael@0:    * be sent to listner functions.
michael@0:    */
michael@0:   emit: function EventEmitter_emit(aEvent) {
michael@0:     this.logEvent(aEvent, arguments);
michael@0: 
michael@0:     if (!this._eventEmitterListeners || !this._eventEmitterListeners.has(aEvent)) {
michael@0:       return;
michael@0:     }
michael@0: 
michael@0:     let originalListeners = this._eventEmitterListeners.get(aEvent);
michael@0:     for (let listener of this._eventEmitterListeners.get(aEvent)) {
michael@0:       // If the object was destroyed during event emission, stop
michael@0:       // emitting.
michael@0:       if (!this._eventEmitterListeners) {
michael@0:         break;
michael@0:       }
michael@0: 
michael@0:       // If listeners were removed during emission, make sure the
michael@0:       // event handler we're going to fire wasn't removed.
michael@0:       if (originalListeners === this._eventEmitterListeners.get(aEvent) ||
michael@0:           this._eventEmitterListeners.get(aEvent).some(function(l) l === listener)) {
michael@0:         try {
michael@0:           listener.apply(null, arguments);
michael@0:         }
michael@0:         catch (ex) {
michael@0:           // Prevent a bad listener from interfering with the others.
michael@0:           let msg = ex + ": " + ex.stack;
michael@0:           Cu.reportError(msg);
michael@0:           dump(msg + "\n");
michael@0:         }
michael@0:       }
michael@0:     }
michael@0:   },
michael@0: 
michael@0:   logEvent: function(aEvent, args) {
michael@0:     let logging = Services.prefs.getBoolPref("devtools.dump.emit");
michael@0: 
michael@0:     if (logging) {
michael@0:       let caller = components.stack.caller.caller;
michael@0:       let func = caller.name;
michael@0:       let path = caller.filename.split(/ -> /)[1] + ":" + caller.lineNumber;
michael@0: 
michael@0:       let argOut = "(";
michael@0:       if (args.length === 1) {
michael@0:         argOut += aEvent;
michael@0:       }
michael@0: 
michael@0:       let out = "EMITTING: ";
michael@0: 
michael@0:       // We need this try / catch to prevent any dead object errors.
michael@0:       try {
michael@0:         for (let i = 1; i < args.length; i++) {
michael@0:           if (i === 1) {
michael@0:             argOut = "(" + aEvent + ", ";
michael@0:           } else {
michael@0:             argOut += ", ";
michael@0:           }
michael@0: 
michael@0:           let arg = args[i];
michael@0:           argOut += arg;
michael@0: 
michael@0:           if (arg && arg.nodeName) {
michael@0:             argOut += " (" + arg.nodeName;
michael@0:             if (arg.id) {
michael@0:               argOut += "#" + arg.id;
michael@0:             }
michael@0:             if (arg.className) {
michael@0:               argOut += "." + arg.className;
michael@0:             }
michael@0:             argOut += ")";
michael@0:           }
michael@0:         }
michael@0:       } catch(e) {
michael@0:         // Object is dead so the toolbox is most likely shutting down,
michael@0:         // do nothing.
michael@0:       }
michael@0: 
michael@0:       argOut += ")";
michael@0:       out += "emit" + argOut + " from " + func + "() -> " + path + "\n";
michael@0: 
michael@0:       dump(out);
michael@0:     }
michael@0:   },
michael@0: };