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: "use strict";
michael@0: 
michael@0: const { Cc, Ci, Cr, Cu } = require("chrome");
michael@0: const { Input, start, stop, end, receive, outputs } = require("../event/utils");
michael@0: const { once, off } = require("../event/core");
michael@0: const { id: addonID } = require("../self");
michael@0: 
michael@0: const unloadMessage = require("@loader/unload");
michael@0: const { addObserver, removeObserver } = Cc['@mozilla.org/observer-service;1'].
michael@0:                                           getService(Ci.nsIObserverService);
michael@0: 
michael@0: const addonUnloadTopic = "sdk:loader:destroy";
michael@0: 
michael@0: const isXrayWrapper = Cu.isXrayWrapper;
michael@0: // In the past SDK used to double-wrap notifications dispatched, which
michael@0: // made them awkward to use outside of SDK. At present they no longer
michael@0: // do that, although we still supported for legacy reasons.
michael@0: const isLegacyWrapper = x =>
michael@0:     x && x.wrappedJSObject &&
michael@0:     "observersModuleSubjectWrapper" in x.wrappedJSObject;
michael@0: 
michael@0: const unwrapLegacy = x => x.wrappedJSObject.object;
michael@0: 
michael@0: // `InputPort` provides a way to create a signal out of the observer
michael@0: // notification subject's for the given `topic`. If `options.initial`
michael@0: // is provided it is used as initial value otherwise `null` is used.
michael@0: // Constructor can be given `options.id` that will be used to create
michael@0: // a `topic` which is namespaced to an add-on (this avoids conflicts
michael@0: // when multiple add-on are used, although in a future host probably
michael@0: // should just be shared across add-ons). It is also possible to
michael@0: // specify a specific `topic` via `options.topic` which is used as
michael@0: // without namespacing. Created signal ends whenever add-on is
michael@0: // unloaded.
michael@0: const InputPort = function InputPort({id, topic, initial}) {
michael@0:   this.id = id || topic;
michael@0:   this.topic = topic || "sdk:" + addonID + ":" + id;
michael@0:   this.value = initial === void(0) ? null : initial;
michael@0:   this.observing = false;
michael@0:   this[outputs] = [];
michael@0: };
michael@0: 
michael@0: // InputPort type implements `Input` signal interface.
michael@0: InputPort.prototype = new Input();
michael@0: InputPort.prototype.constructor = InputPort;
michael@0: 
michael@0: // When port is started (which is when it's subgraph get's
michael@0: // first subscriber) actual observer is registered.
michael@0: InputPort.start = input => {
michael@0:   input.addListener(input);
michael@0:   // Also register add-on unload observer to end this signal
michael@0:   // when that happens.
michael@0:   addObserver(input, addonUnloadTopic, false);
michael@0: };
michael@0: InputPort.prototype[start] = InputPort.start;
michael@0: 
michael@0: InputPort.addListener = input => addObserver(input, input.topic, false);
michael@0: InputPort.prototype.addListener = InputPort.addListener;
michael@0: 
michael@0: // When port is stopped (which is when it's subgraph has no
michael@0: // no subcribers left) an actual observer unregistered.
michael@0: // Note that port stopped once it ends as well (which is when
michael@0: // add-on is unloaded).
michael@0: InputPort.stop = input => {
michael@0:   input.removeListener(input);
michael@0:   removeObserver(input, addonUnloadTopic);
michael@0: };
michael@0: InputPort.prototype[stop] = InputPort.stop;
michael@0: 
michael@0: InputPort.removeListener = input => removeObserver(input, input.topic);
michael@0: InputPort.prototype.removeListener = InputPort.removeListener;
michael@0: 
michael@0: // `InputPort` also implements `nsIObserver` interface and
michael@0: // `nsISupportsWeakReference` interfaces as it's going to be used as such.
michael@0: InputPort.prototype.QueryInterface = function(iid) {
michael@0:   if (!iid.equals(Ci.nsIObserver) && !iid.equals(Ci.nsISupportsWeakReference))
michael@0:     throw Cr.NS_ERROR_NO_INTERFACE;
michael@0: 
michael@0:   return this;
michael@0: };
michael@0: 
michael@0: // `InputPort` instances implement `observe` method, which is invoked when
michael@0: // observer notifications are dispatched. The `subject` of that notification
michael@0: // are received on this signal.
michael@0: InputPort.prototype.observe = function(subject, topic, data) {
michael@0:   // Unwrap message from the subject. SDK used to have it's own version of
michael@0:   // wrappedJSObjects which take precedence, if subject has `wrappedJSObject`
michael@0:   // and it's not an XrayWrapper use it as message. Otherwise use subject as
michael@0:   // is.
michael@0:   const message = subject === null ? null :
michael@0:         isLegacyWrapper(subject) ? unwrapLegacy(subject) :
michael@0:         isXrayWrapper(subject) ? subject :
michael@0:         subject.wrappedJSObject ? subject.wrappedJSObject :
michael@0:         subject;
michael@0: 
michael@0:   // If observer topic matches topic of the input port receive a message.
michael@0:   if (topic === this.topic) {
michael@0:     receive(this, message);
michael@0:   }
michael@0: 
michael@0:   // If observe topic is add-on unload topic we create an end message.
michael@0:   if (topic === addonUnloadTopic && message === unloadMessage) {
michael@0:     end(this);
michael@0:   }
michael@0: };
michael@0: 
michael@0: exports.InputPort = InputPort;