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: /**
michael@0:  * Implementation of a CommonJS module loader for workers.
michael@0:  *
michael@0:  * Use:
michael@0:  * // in the .js file loaded by the constructor of the worker
michael@0:  * importScripts("resource://gre/modules/workers/require.js");
michael@0:  * let module = require("resource://gre/modules/worker/myModule.js");
michael@0:  *
michael@0:  * // in myModule.js
michael@0:  * // Load dependencies
michael@0:  * let SimpleTest = require("resource://gre/modules/workers/SimpleTest.js");
michael@0:  * let Logger = require("resource://gre/modules/workers/Logger.js");
michael@0:  *
michael@0:  * // Define things that will not be exported
michael@0:  * let someValue = // ...
michael@0:  *
michael@0:  * // Export symbols
michael@0:  * exports.foo = // ...
michael@0:  * exports.bar = // ...
michael@0:  *
michael@0:  *
michael@0:  * Note #1:
michael@0:  * Properties |fileName| and |stack| of errors triggered from a module
michael@0:  * contain file names that do not correspond to human-readable module paths.
michael@0:  * Human readers should rather use properties |moduleName| and |moduleStack|.
michael@0:  *
michael@0:  * Note #2:
michael@0:  * The current version of |require()| only accepts absolute URIs.
michael@0:  *
michael@0:  * Note #3:
michael@0:  * By opposition to some other module loader implementations, this module
michael@0:  * loader does not enforce separation of global objects. Consequently, if
michael@0:  * a module modifies a global object (e.g. |String.prototype|), all other
michael@0:  * modules in the same worker may be affected.
michael@0:  */
michael@0: 
michael@0: 
michael@0: (function(exports) {
michael@0:   "use strict";
michael@0: 
michael@0:   if (exports.require) {
michael@0:     // Avoid double-imports
michael@0:     return;
michael@0:   }
michael@0: 
michael@0:   // Simple implementation of |require|
michael@0:   let require = (function() {
michael@0: 
michael@0:     /**
michael@0:      * Mapping from module paths to module exports.
michael@0:      *
michael@0:      * @keys {string} The absolute path to a module.
michael@0:      * @values {object} The |exports| objects for that module.
michael@0:      */
michael@0:     let modules = new Map();
michael@0: 
michael@0:     /**
michael@0:      * Mapping from object urls to module paths.
michael@0:      */
michael@0:     let paths = {
michael@0:       /**
michael@0:        * @keys {string} The object url holding a module.
michael@0:        * @values {string} The absolute path to that module.
michael@0:        */
michael@0:       _map: new Map(),
michael@0:       /**
michael@0:        * A regexp that may be used to search for all mapped paths.
michael@0:        */
michael@0:       get regexp() {
michael@0:         if (this._regexp) {
michael@0:           return this._regexp;
michael@0:         }
michael@0:         let objectURLs = [];
michael@0:         for (let [objectURL, _] of this._map) {
michael@0:           objectURLs.push(objectURL);
michael@0:         }
michael@0:         return this._regexp = new RegExp(objectURLs.join("|"), "g");
michael@0:       },
michael@0:       _regexp: null,
michael@0:       /**
michael@0:        * Add a mapping from an object url to a path.
michael@0:        */
michael@0:       set: function(url, path) {
michael@0:         this._regexp = null; // invalidate regexp
michael@0:         this._map.set(url, path);
michael@0:       },
michael@0:       /**
michael@0:        * Get a mapping from an object url to a path.
michael@0:        */
michael@0:       get: function(url) {
michael@0:         return this._map.get(url);
michael@0:       },
michael@0:       /**
michael@0:        * Transform a string by replacing all the instances of objectURLs
michael@0:        * appearing in that string with the corresponding module path.
michael@0:        *
michael@0:        * This is used typically to translate exception stacks.
michael@0:        *
michael@0:        * @param {string} source A source string.
michael@0:        * @return {string} The same string as |source|, in which every occurrence
michael@0:        * of an objectURL registered in this object has been replaced with the
michael@0:        * corresponding module path.
michael@0:        */
michael@0:       substitute: function(source) {
michael@0:         let map = this._map;
michael@0:         return source.replace(this.regexp, function(url) {
michael@0:           return map.get(url) || url;
michael@0:         }, "g");
michael@0:       }
michael@0:     };
michael@0: 
michael@0:     /**
michael@0:      * A human-readable version of |stack|.
michael@0:      *
michael@0:      * @type {string}
michael@0:      */
michael@0:     Object.defineProperty(Error.prototype, "moduleStack",
michael@0:     {
michael@0:       get: function() {
michael@0:         return paths.substitute(this.stack);
michael@0:       }
michael@0:     });
michael@0:     /**
michael@0:      * A human-readable version of |fileName|.
michael@0:      *
michael@0:      * @type {string}
michael@0:      */
michael@0:     Object.defineProperty(Error.prototype, "moduleName",
michael@0:     {
michael@0:       get: function() {
michael@0:         return paths.substitute(this.fileName);
michael@0:       }
michael@0:     });
michael@0: 
michael@0:     /**
michael@0:      * Import a module
michael@0:      *
michael@0:      * @param {string} path The path to the module.
michael@0:      * @return {*} An object containing the properties exported by the module.
michael@0:      */
michael@0:     return function require(path) {
michael@0:       if (typeof path != "string" || path.indexOf("://") == -1) {
michael@0:         throw new TypeError("The argument to require() must be a string uri, got " + path);
michael@0:       }
michael@0:       // Automatically add ".js" if there is no extension
michael@0:       let uri;
michael@0:       if (path.lastIndexOf(".") <= path.lastIndexOf("/")) {
michael@0:         uri = path + ".js";
michael@0:       } else {
michael@0:         uri = path;
michael@0:       }
michael@0: 
michael@0:       // Exports provided by the module
michael@0:       let exports = Object.create(null);
michael@0: 
michael@0:       // Identification of the module
michael@0:       let module = {
michael@0:         id: path,
michael@0:         uri: uri,
michael@0:         exports: exports
michael@0:       };
michael@0: 
michael@0:       // Make module available immediately
michael@0:       // (necessary in case of circular dependencies)
michael@0:       if (modules.has(path)) {
michael@0:         return modules.get(path).exports;
michael@0:       }
michael@0:       modules.set(path, module);
michael@0: 
michael@0:       let name = ":" + path;
michael@0:       let objectURL;
michael@0:       try {
michael@0:         // Load source of module, synchronously
michael@0:         let xhr = new XMLHttpRequest();
michael@0:         xhr.open("GET", uri, false);
michael@0:         xhr.responseType = "text";
michael@0:         xhr.send();
michael@0: 
michael@0: 
michael@0:         let source = xhr.responseText;
michael@0:         if (source == "") {
michael@0:           // There doesn't seem to be a better way to detect that the file couldn't be found
michael@0:           throw new Error("Could not find module " + path);
michael@0:         }
michael@0:         // From the source, build a function and an object URL. We
michael@0:         // avoid any newline at the start of the file to ensure that
michael@0:         // we do not mess up with line numbers. However, using object URLs
michael@0:         // messes up with stack traces in instances of Error().
michael@0:         source = "require._tmpModules[\"" + name + "\"] = " +
michael@0:           "function(exports, require, module) {" +
michael@0:           source +
michael@0:         "\n}\n";
michael@0:         let blob = new Blob(
michael@0:           [
michael@0:             (new TextEncoder()).encode(source)
michael@0:           ], {
michael@0:             type: "application/javascript"
michael@0:           });
michael@0:         objectURL = URL.createObjectURL(blob);
michael@0:         paths.set(objectURL, path);
michael@0:         importScripts(objectURL);
michael@0:         require._tmpModules[name].call(null, exports, require, module);
michael@0: 
michael@0:       } catch (ex) {
michael@0:         // Module loading has failed, exports should not be made available
michael@0:         // after all.
michael@0:         modules.delete(path);
michael@0:         throw ex;
michael@0:       } finally {
michael@0:         if (objectURL) {
michael@0:           // Clean up the object url as soon as possible. It will not be needed.
michael@0:           URL.revokeObjectURL(objectURL);
michael@0:         }
michael@0:         delete require._tmpModules[name];
michael@0:       }
michael@0: 
michael@0:       Object.freeze(module.exports);
michael@0:       Object.freeze(module);
michael@0:       return module.exports;
michael@0:     };
michael@0:   })();
michael@0: 
michael@0:   /**
michael@0:    * An object used to hold temporarily the module constructors
michael@0:    * while they are being loaded.
michael@0:    *
michael@0:    * @keys {string} The path to the module, prefixed with ":".
michael@0:    * @values {function} A function wrapping the module.
michael@0:    */
michael@0:   require._tmpModules = Object.create(null);
michael@0:   Object.freeze(require);
michael@0: 
michael@0:   Object.defineProperty(exports, "require", {
michael@0:     value: require,
michael@0:     enumerable: true,
michael@0:     configurable: false
michael@0:   });
michael@0: })(this);