imd.js

/**
 * @license
 * Copyright (c) 2015 The Polymer Project Authors. All rights reserved.
 * This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
 * The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
 * The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
 * Code distributed by Google as part of the polymer project is also
 * subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
 */
(function(scope) {
  'use strict';

  /** @type {Object<key, *>} A mapping of ids to modules. */
  var _modules = Object.create(null);

  // `define`

  /**
   * An AMD-compliant implementation of `define` that does not perform loading.
   *
   * @see https://github.com/amdjs/amdjs-api/wiki/AMD
   *
   * Dependencies must be loaded prior to calling `define`, or you will receive
   * an error.
   *
   * @param {string=} id The id of the module being defined. If not provided,
   *     one will be given to the module based on the document it was called in.
   * @param {Array<string>=} dependencies A list of module ids that should be
   *     exposed as dependencies of the module being defined.
   * @param {function(...*)|*} factory A function that is given the exported
   *     values for `dependencies`, in the same order. Alternatively, you can
   *     pass the exported value directly.
   */
  function define(id, dependencies, factory) {
    factory = factory || dependencies || id;
    if (!Array.isArray(dependencies)) {
      // TODO(nevir): Default dependencies should be require, exports, module.
      dependencies = Array.isArray(id) ? id : [];
    }
    var inferredId = _inferModuleId();
    if (typeof id !== 'string') {
      id = inferredId;
    }
    // TODO(nevir): Just support \ as path separators too. Yay Windows!
    if (id.indexOf('\\') !== -1) {
      throw new TypeError('Please use / as module path delimiters');
    }
    if (id in _modules) {
      throw new Error('The module "' + id + '" has already been defined');
    }
    // Extract the entire module path up to the file name. Aka `dirname()`.
    //
    // TODO(nevir): This is naive; doesn't support the vulcanize case.
    var base = inferredId.match(/^(.*?)[^\/]*$/)[1];
    _modules[id] = _runFactory(id, base, dependencies, factory);
    return _modules[id];
  }

  // Semi-private. We expose this for tests & introspection.
  define._modules = _modules;

  /**
   * Let other implementations know that this is an AMD implementation.
   * @see https://github.com/amdjs/amdjs-api/wiki/AMD#defineamd-property-
   */
  define.amd = {};

  // Utility

  /** @return {string} A module id inferred from the current document/import. */
  function _inferModuleId() {
    var script = document.currentScript;
    if (script.hasAttribute('as')) {
      return script.getAttribute('as');
    }

    var doc = script && script.ownerDocument || document;
    if (!doc.baseURI) {
      throw new Error('Unable to determine a module id: No baseURI for the document');
    }

    if (script.hasAttribute('src')) {
      return new URL(script.getAttribute('src'), doc.baseURI).toString();
    }

    return doc.baseURI;
  }

  /**
   * Calls `factory` with the exported values of `dependencies`.
   *
   * @param {string} id The id of the module defined by the factory.
   * @param {string} base The base path that modules should be relative to.
   * @param {Array<string>} dependencies
   * @param {function(...*)|*} factory
   */
  function _runFactory(moduleId, base, dependencies, factory) {
    if (typeof factory !== 'function') return factory;

    var exports, module;
    var modules = dependencies.map(function(id) {
      if (id === 'exports') {
        return exports = {};
      }
      if (id === 'require') {
        return _require;
      }
      if (id === 'module') {
        return module = {id: moduleId};
      }
      id = _resolveRelativeId(base, id);
      return _require(id);
    });
    var result = factory.apply(null, modules);
    return (module && module.exports) || exports || result;
  }

  /**
   * @param {string} base The module path/URI that acts as the relative base.
   * @param {string} id The module ID that should be relatively resolved.
   * @return {string} The expanded module ID.
   */
  function _resolveRelativeId(base, id) {
    if (id[0] !== '.') return id;
    // We need to be careful to only process the path of URLs. This regex
    // strips off the URL protocol and domain, leaving us with just the URL's
    // path.
    var match  = base.match(/^([^\/]*\/\/[^\/]+\/)?(.*?)\/?$/);
    var prefix = match[1] || '';
    // We start with the base, and then mutate it into the final path.
    var terms   = match[2] ? match[2].split('/') : [];
    // Split the terms, ignoring any leading or trailing path separators.
    var idTerms = id.match(/^\/?(.*?)\/?$/)[1].split('/');
    for (var i = 0; i < idTerms.length; i++) {
      var idTerm = idTerms[i];
      if (idTerm === '.') {
        continue;
      } else if (idTerm === '..') {
        terms.pop();
      } else {
        terms.push(idTerm);
      }
    }
    return prefix + terms.join('/');
  }

  function _require(id) {
    if (!(id in _modules)) {
      throw new ReferenceError('The module "' + id + '" has not been loaded');
    }
    return _modules[id];
  }

  // Exports
  scope.define = define;

})(this);