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 file,
michael@0:  * You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: let EXPORTED_SYMBOLS = [
michael@0:   "AsyncRunner",
michael@0: ];
michael@0: 
michael@0: const { interfaces: Ci, classes: Cc } = Components;
michael@0: 
michael@0: function AsyncRunner(callbacks) {
michael@0:   this._callbacks = callbacks;
michael@0:   this._iteratorQueue = [];
michael@0: 
michael@0:   // This catches errors reported to the console, e.g., via Cu.reportError.
michael@0:   Cc["@mozilla.org/consoleservice;1"].
michael@0:     getService(Ci.nsIConsoleService).
michael@0:     registerListener(this);
michael@0: }
michael@0: 
michael@0: AsyncRunner.prototype = {
michael@0: 
michael@0:   appendIterator: function AR_appendIterator(iter) {
michael@0:     this._iteratorQueue.push(iter);
michael@0:   },
michael@0: 
michael@0:   next: function AR_next(/* ... */) {
michael@0:     if (!this._iteratorQueue.length) {
michael@0:       this.destroy();
michael@0:       this._callbacks.done();
michael@0:       return;
michael@0:     }
michael@0: 
michael@0:     // send() discards all arguments after the first, so there's no choice here
michael@0:     // but to send only one argument to the yielder.
michael@0:     let args = [arguments.length <= 1 ? arguments[0] : Array.slice(arguments)];
michael@0:     try {
michael@0:       var val = this._iteratorQueue[0].send.apply(this._iteratorQueue[0], args);
michael@0:     }
michael@0:     catch (err if err instanceof StopIteration) {
michael@0:       this._iteratorQueue.shift();
michael@0:       this.next();
michael@0:       return;
michael@0:     }
michael@0:     catch (err) {
michael@0:       this._callbacks.error(err);
michael@0:     }
michael@0: 
michael@0:     // val is truthy => call next
michael@0:     // val is an iterator => prepend it to the queue and start on it
michael@0:     if (val) {
michael@0:       if (typeof(val) != "boolean")
michael@0:         this._iteratorQueue.unshift(val);
michael@0:       this.next();
michael@0:     }
michael@0:   },
michael@0: 
michael@0:   destroy: function AR_destroy() {
michael@0:     Cc["@mozilla.org/consoleservice;1"].
michael@0:       getService(Ci.nsIConsoleService).
michael@0:       unregisterListener(this);
michael@0:     this.destroy = function AR_alreadyDestroyed() {};
michael@0:   },
michael@0: 
michael@0:   observe: function AR_consoleServiceListener(msg) {
michael@0:     if (msg instanceof Ci.nsIScriptError &&
michael@0:         !(msg.flags & Ci.nsIScriptError.warningFlag))
michael@0:     {
michael@0:       this._callbacks.consoleError(msg);
michael@0:     }
michael@0:   },
michael@0: };