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 } = require("chrome");
michael@0: const { Input, start, stop, receive, outputs } = require("../event/utils");
michael@0: const { id: addonID } = require("../self");
michael@0: const { setImmediate } = require("../timers");
michael@0: const { notifyObservers } = Cc['@mozilla.org/observer-service;1'].
michael@0:                              getService(Ci.nsIObserverService);
michael@0: 
michael@0: const NOT_AN_INPUT = "OutputPort can be used only for sending messages";
michael@0: 
michael@0: // `OutputPort` creates a port to which messages can be send. Those
michael@0: // messages are actually disptached as `subject`'s of the observer
michael@0: // notifications. This is handy for communicating between different
michael@0: // components of the SDK. By default messages are dispatched
michael@0: // asynchronously, although `options.sync` can be used to make them
michael@0: // synchronous. If `options.id` is given `topic` for observer
michael@0: // notifications is generated by namespacing it, to avoid spamming
michael@0: // other SDK add-ons. It's also possible to provide `options.topic`
michael@0: // to use excat `topic` without namespacing it.
michael@0: //
michael@0: // Note: Symmetric `new InputPort({ id: "x" })` instances can be used to
michael@0: // receive messages send to the instances of `new OutputPort({ id: "x" })`.
michael@0: const OutputPort = function({id, topic, sync}) {
michael@0:   this.id = id || topic;
michael@0:   this.sync = !!sync;
michael@0:   this.topic = topic || "sdk:" + addonID + ":" + id;
michael@0: };
michael@0: // OutputPort extends base signal type to implement same message
michael@0: // receiving interface.
michael@0: OutputPort.prototype = new Input();
michael@0: OutputPort.constructor = OutputPort;
michael@0: 
michael@0: // OutputPort can not be consumed there for starting or stopping it
michael@0: // is not supported.
michael@0: OutputPort.prototype[start] = _ => { throw TypeError(NOT_AN_INPUT); };
michael@0: OutputPort.prototype[stop] = _ => { throw TypeError(NOT_AN_INPUT); };
michael@0: 
michael@0: // Port reecives message send to it, which will be dispatched via
michael@0: // observer notification service.
michael@0: OutputPort.receive = ({topic, sync}, message) => {
michael@0:   const type = typeof(message);
michael@0:   const supported = message === null ||
michael@0:                     type === "object" ||
michael@0:                     type === "function";
michael@0: 
michael@0:   // There is no sensible way to wrap JS primitives that would make sense
michael@0:   // for general observer notification users. It's also probably not very
michael@0:   // useful to dispatch JS primitives as subject of observer service, there
michael@0:   // for we do not support those use cases.
michael@0:   if (!supported)
michael@0:     throw new TypeError("Unsupproted message type: `" + type + "`");
michael@0: 
michael@0:   // Normalize `message` to create a valid observer notification `subject`.
michael@0:   // If `message` is `null`, implements `nsISupports` interface or already
michael@0:   // represents wrapped JS object use it as is. Otherwise create a wrapped
michael@0:   // object so that observers could receive it.
michael@0:   const subject = message === null ? null :
michael@0:                   message instanceof Ci.nsISupports ? message :
michael@0:                   message.wrappedJSObject ? message :
michael@0:                   {wrappedJSObject: message};
michael@0:   if (sync)
michael@0:     notifyObservers(subject, topic, null);
michael@0:   else
michael@0:     setImmediate(notifyObservers, subject, topic, null);
michael@0: };
michael@0: OutputPort.prototype[receive] = OutputPort.receive;
michael@0: exports.OutputPort = OutputPort;