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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
"use strict";
module.metadata = {
"stability": "deprecated"
};
const { Cc, Ci } = require("chrome");
const { when: unload } = require("../system/unload");
const { ns } = require("../core/namespace");
const { on, off, emit, once } = require("../system/events");
const { id } = require("../self");
const subscribers = ns();
const cache = [];
/**
* Topics specifically available to Jetpack-generated extensions.
*
* Using these predefined consts instead of the platform strings is good:
* - allows us to scope topics specifically for Jetpacks
* - addons aren't dependent on strings nor behavior of core platform topics
* - the core platform topics are not clearly named
*
*/
exports.topics = {
/**
* A topic indicating that the application is in a state usable
* by add-ons.
*/
APPLICATION_READY: id + "_APPLICATION_READY"
};
function Listener(callback, target) {
return function listener({ subject, data }) {
callback.call(target || callback, subject, data);
}
}
/**
* Register the given callback as an observer of the given topic.
*
* @param topic {String}
* the topic to observe
*
* @param callback {Object}
* the callback; an Object that implements nsIObserver or a Function
* that gets called when the notification occurs
*
* @param target {Object} [optional]
* the object to use as |this| when calling a Function callback
*
* @returns the observer
*/
function add(topic, callback, target) {
let listeners = subscribers(callback);
if (!(topic in listeners)) {
let listener = Listener(callback, target);
listeners[topic] = listener;
// Cache callback unless it's already cached.
if (!~cache.indexOf(callback))
cache.push(callback);
on(topic, listener);
}
};
exports.add = add;
/**
* Unregister the given callback as an observer of the given topic.
*
* @param topic {String}
* the topic being observed
*
* @param callback {Object}
* the callback doing the observing
*
* @param target {Object} [optional]
* the object being used as |this| when calling a Function callback
*/
function remove(topic, callback, target) {
let listeners = subscribers(callback);
if (topic in listeners) {
let listener = listeners[topic];
delete listeners[topic];
// If no more observers are registered and callback is still in cache
// then remove it.
let index = cache.indexOf(callback);
if (~index && !Object.keys(listeners).length)
cache.splice(index, 1)
off(topic, listener);
}
};
exports.remove = remove;
/**
* Notify observers about something.
*
* @param topic {String}
* the topic to notify observers about
*
* @param subject {Object} [optional]
* some information about the topic; can be any JS object or primitive
*
* @param data {String} [optional] [deprecated]
* some more information about the topic; deprecated as the subject
* is sufficient to pass all needed information to the JS observers
* that this module targets; if you have multiple values to pass to
* the observer, wrap them in an object and pass them via the subject
* parameter (i.e.: { foo: 1, bar: "some string", baz: myObject })
*/
function notify(topic, subject, data) {
emit(topic, {
subject: subject === undefined ? null : subject,
data: data === undefined ? null : data
});
}
exports.notify = notify;
unload(function() {
// Make a copy of cache first, since cache will be changing as we
// iterate through it.
cache.slice().forEach(function(callback) {
Object.keys(subscribers(callback)).forEach(function(topic) {
remove(topic, callback);
});
});
})
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