service_worker.ts

// This API proposal depends on:
//  DOM: http://www.w3.org/TR/domcore/
//  URLs: http://url.spec.whatwg.org/
//  Promises: https://github.com/slightlyoff/DOMPromise/
//  Shared Workers:
//    http://www.whatwg.org/specs/web-apps/current-work/multipage/workers.html#shared-workers

////////////////////////////////////////////////////////////////////////////////
// Document APIs
////////////////////////////////////////////////////////////////////////////////

interface RegistrationOptions {
  scope: string;
}
// Semi-private to work around TS. Not for impl.
class _RegistrationOptions implements RegistrationOptions {
  scope = "/*";
}

interface ServiceWorkerContainer extends EventTarget {
  controller?: ServiceWorker; // the worker handling resource requests for this page

  // This atribute returns a Promise that resolves when this document
  // has a controller
  ready: Promise; // Promise<ServiceWorkerRegistration>

  // Returns a Promise<ServiceWorkerRegistration>
  register(url: string, options?: _RegistrationOptions): Promise;

  // Returns a Promise<ServiceWorkerRegistration>
  getRegistration(docURL?:string): Promise;
    // docURL defaults to location.href
    // Resolves with the ServiceWorkerRegistration that controls docURL or undefined if none is found
    // Rejects with DOMError SecurityError if docURL is cross origin

  // Returns a Promise<Array<ServiceWorkerRegistration>>
  getRegistrations(): Promise;
    // Resolves with an array of all ServiceWorkerRegistrations for the origin.
    // Resolves with an empty array if none exist.

  oncontrollerchange: (ev: Event) => any;
    // Fires when .controller changes

  onerror: (ev: ErrorEvent) => any;
    // Called for any error from the active or installing SW's
    // FIXME: allow differentiation between active and installing SW's
    //        here, perhaps via .worker?
}

// extensions to window.navigator and self.navigator
interface NavigatorServiceWorker {
  // null if page has no activated worker
  serviceWorker: ServiceWorkerContainer;
}

interface Navigator extends
  NavigatorServiceWorker,
  EventTarget,
  // the rest is just stuff from the default ts definition
  NavigatorID,
  NavigatorOnLine,
  // NavigatorDoNotTrack,
  // NavigatorAbilities,
  NavigatorGeolocation
  // MSNavigatorAbilities
{ }

interface ServiceWorkerRegistration extends EventTarget {
  installing?: ServiceWorker; // worker undergoing the install process
  waiting?: ServiceWorker; // installed worker, waiting to become active
  active?: ServiceWorker; // the activating/activated worker, can be used as a controller

  // The registration pattern that matched this SW instance. E.g., if the
  // following registrations are made:
  //    navigator.serviceWorker.register("serviceworker.js", "/foo/");
  //    navigator.serviceWorker.register("serviceworker.js", "/bar/");
  // And the user navigates to http://example.com/foo/index.html,
  //    self.scope == "/foo/"
  // SW's can use this to disambiguate which context they were started from.
  scope: string;

  // Ping the server for an updated version of this registration, without
  // consulting caches. Conceptually the same operation that SW's do max once
  // every 24 hours.
  update: () => void;

  unregister(): Promise;
    // Unregisters this registration.
    // Resolves with boolean value.

  onupdatefound: (ev: Event) => any;
    // Fires when .installing becomes a new worker
}

interface ServiceWorker extends Worker, AbstractWorker {
  // Provides onerror, postMessage, etc.
  scriptURL: string;
  state: string; // "installing" -> "installed" -> "activating" -> "activated" -> "redundant"
  onstatechange: (ev: Event) => any;
}

declare var ServiceWorker: {
  prototype: ServiceWorker;
}

///////////////////////////////////////////////////////////////////////////////
// The Service Worker
///////////////////////////////////////////////////////////////////////////////
class ExtendableEvent extends _Event {
  // Delay treating the installing worker until the passed Promise resolves
  // successfully. This is primarily used to ensure that an ServiceWorker is not
  // active until all of the "core" Caches it depends on are populated.
  waitUntil(f: Promise): void {}
}

class InstallEvent extends ExtendableEvent {
  activeWorker: ServiceWorker = null;
}

interface InstallEventHandler { (e:InstallEvent); }
interface ActivateEventHandler { (e:ExtendableEvent); }
interface FetchEventHandler { (e:FetchEvent); }

// FIXME: need custom event types!
interface BeforeCacheEvictionEventHandler { (e:_Event); }
interface CacheEvictionEventHandler { (e:_Event); }

interface OnlineEventHandler { (e:_Event); }
interface OfflineEventHandler { (e:_Event); }

class ServiceWorkerClients {
  getAll(options?: ServiceWorkerClientQueryOptions): Promise { // Promise for Array<ServiceWorkerClient>
    return new Promise(function() {
      // the objects returned will be new instances every time
    });
  }
}

interface ServiceWorkerClientQueryOptions {
  includeUncontrolled: boolean;
}

class ServiceWorkerClient {
  constructor(url: string) {
    // attempt to open a new tab/window to url
  }

  // fulfills with no value if window/tab opens and can receive messages
  // rejects if the above fails (with error)
  // read-only
  ready: Promise;

  // http://www.w3.org/TR/page-visibility/#dom-document-visibilitystate
  // this value does not change after object creation, it's a snapshot
  // read-only
  visibilityState: string; // { "hidden", "visible", "prerender", "unloaded" }

  // http://www.whatwg.org/specs/web-apps/current-work/multipage/interaction.html#dom-document-hasfocus
  // this value does not change after object creation, it's a snapshot
  // read-only
  focused: boolean;

  // this value does not change after object creation, it's a snapshot
  // read-only
  url: string;

  // http://fetch.spec.whatwg.org/#concept-request-context-frame-type
  // so we can tell the difference between page, iframe & worker
  // read-only
  frameType: string;

  postMessage: (message: any, targetOrigin: string, ports?: any) => void;

  // rejects if client is gone, not yet ready, or cannot be focused for some other reason
  // fulfills when client gains focus, or is already focused
  focus: () => Promise;
}

// The scope in which worker code is executed
class ServiceWorkerGlobalScope extends WorkerGlobalScope {

  self: ServiceWorkerGlobalScope;
  caches: CacheStorage;
  scriptCache: Cache;

  // A container for a list of ServiceWorkerClient objects that correspond to
  // browsing contexts (or shared workers) that are on the origin of this SW
  clients: ServiceWorkerClients;
  registration: ServiceWorkerRegistration;

  skipWaiting: () => Promise;

  //
  // Events
  //

  // "online" and "offline" events are deliveredy via the WorkerGlobalScope
  // contract:
  //    http://www.whatwg.org/specs/web-apps/current-work/multipage/workers.html#workerglobalscope

  // New Events

  // Called when a worker is downloaded and being setup to handle
  // events (navigations, alerts, etc.)
  oninstall: InstallEventHandler;

  // Called when a worker becomes the active event worker for a mapping
  onactivate: ActivateEventHandler;

  // Called whenever this worker is meant to decide the disposition of a
  // request.
  onfetch: FetchEventHandler;

  onbeforeevicted: BeforeCacheEvictionEventHandler;
  onevicted: CacheEvictionEventHandler;

  // ServiceWorkerGlobalScope objects act as if they had an implicit MessagePort
  // associated with them. This port is part of a channel that is set up when
  // the worker is created, but it is not exposed. This object must never be
  // garbage collected before the ServiceWorkerGlobalScope object.
  // All messages received by that port must immediately be retargeted at the
  // ServiceWorkerGlobalScope object.
  // The ev.source of these MessageEvents are instances of ServiceWorkerClient
  onmessage: (ev: MessageEvent) => any;

  // FIXME(slightlyoff): Need to add flags for:
  //  - custom "accept/reject" handling, perhaps with global config
  //  - flag to consult the HTTP cache first?
  fetch(request:Request);
  fetch(request:string); // a URL

  fetch(request:any) : Promise {
    // Notes:
    //  Promise resolves as soon as headers are available
    //  The Response object contains a toBlob() method that returns a
    //  Promise for the body content.
    //  The toBlob() promise will reject if the response is a OpaqueResponse.
    return new Promise(function(r) {
      r.resolve(_defaultToBrowserHTTP(request));
    });
  }
}

///////////////////////////////////////////////////////////////////////////////
// Event Worker APIs
///////////////////////////////////////////////////////////////////////////////

// http://fetch.spec.whatwg.org/#requests
class Request {
  constructor(params?) {
    if (params) {
      if (typeof params.timeout != "undefined") {
        this.timeout = params.timeout;
      }
      if (typeof params.url != "undefined") {
        this.url = params.url;
      }
      if (typeof params.synchronous != "undefined") {
        this.synchronous = params.synchronous;
      }
      if (typeof params.forcePreflight != "undefined") {
        this.forcePreflight = params.forcePreflight;
      }
      if (typeof params.omitCredentials != "undefined") {
        this.omitCredentials = params.omitCredentials;
      }
      if (typeof params.method != "undefined") {
        this.method = params.method;
      }
      if (typeof params.headers != "undefined") {
        this.headers = params.headers;
      }
      if (typeof params.body != "undefined") {
        this.body = params.body;
      }
    }
  }

  // see: http://www.w3.org/TR/XMLHttpRequest/#the-timeout-attribute
  timeout: Number = 0;
  url: string;
  method: string = "GET";
  origin: string;
  // FIXME: mode doesn't seem useful here.
  mode: string; // Can be one of "same origin", "tainted cross-origin", "CORS", "CORS-with-forced-preflight"
  // FIXME: we only provide async!
  synchronous: boolean = false;
  forcePreflight: boolean = false;
  omitCredentials: boolean = false;
  referrer: URL;
  headers: Map<string, string>; // Needs filtering!
  body: any; /*TypedArray? String?*/
}

// http://fetch.spec.whatwg.org/#responses
class AbstractResponse {
  constructor() {}
}

class OpaqueResponse extends AbstractResponse {
  // This class represents the result of cross-origin fetched resources that are
  // tainted, e.g. <img src="http://cross-origin.example/test.png">

  get url(): string { return ""; } // Read-only for x-origin
}

class Response extends AbstractResponse {
  constructor(params?) {
    if (params) {
      if (typeof params.status != "undefined") {
        this.status = params.status;
      }
      if (typeof params.statusText != "undefined") {
        this.statusText = params.statusText;
      }
      if (typeof params.headers != "undefined") {
        this.headers = params.headers;
      }
      /*
      // FIXME: What do we want to do about passing in the body?
      if (typeof params.body != "undefined") {
        this.body = params.body;
      }
      */
    }
    super();
  }

  // This class represents the result of all other fetched resources, including
  // cross-origin fetched resources using the CORS fetching mode.
  status: Number;
  statusText: string;
  // Explicitly omitting httpVersion

  // NOTE: the internal "_headers" is not meant to be exposed. Only here for
  //       pseudo-impl purposes.
  _headers: Map<string, string>; // FIXME: Needs filtering!
  get headers() {
    // TODO: outline the whitelist of readable headers
    return this._headers;
  }
  set headers(items) {
    if (items instanceof Map) {
      items.forEach((value, key, map) => this._headers.set(key, value))
    } else {
      // Enumerate own properties and treat them as key/value pairs
      for (var x in items) {
        (function(x) {
          if (items.hasOwnProperty(x)) { this._headers.set(x, items[x]); }
        }).call(this, x);
      }
    }
  }
  url: string;
  toBlob(): Promise { return accepted(new Blob()); }

  // http://fetch.spec.whatwg.org/#dom-response-redirect
  static redirect(url, status) {
    return new Response();
  }
}

class CORSResponse extends Response {
  // TODO: slightlyoff: make CORS headers readable but not setable?
  // TODO: outline the whitelist of readable headers
}

class FetchEvent extends _Event {
  // The body of the request.
  request: Request;

  // The window issuing the request.
  client: ServiceWorkerClient;

  // Has the user provided intent for the page to be reloaded fresher than
  // their current view? Eg: pressing the refresh button
  // Clicking a link & hitting back shouldn't be considered a reload.
  // Ctrl+l enter: Left to the UA to decide
  isReload: boolean = false;

  // * If a Promise is provided, it must resolve with a Response, else a
  //   Network Error is thrown.
  // * If the request isTopLevel navigation and the return value
  //   is a CrossOriginResponse (an opaque response body), a Network Error is
  //   thrown.
  // * The final URL of all successful (non network-error) responses is
  //   the *requested* URL.
  // * Renderer-side security checks about tainting for
  //   x-origin content are tied to the transparency (or opacity) of
  //   the Response body, not URLs.
  //
  //  respondWith(r: Promise) : void;
  //  respondWith(r: Response) : void;
  respondWith(r: any) : void { // "any" to make the TS compiler happy:
    if (!(r instanceof Response) || !(r instanceof Promise)) {
      throw new Error("Faux NetworkError because DOM is currently b0rken");
    }

    this.stopImmediatePropagation();

    if (r instanceof Response) {
      r = new Promise(function(resolver) { resolver.resolve(r); });
    }
    r.then(_useWorkerResponse,
           _defaultToBrowserHTTP);
  }

  forwardTo(url: string) : Promise; // treated as url
  // "any" to make the TS compiler happy:
  forwardTo(url: any) : Promise {
    if (!(url instanceof _URL) || typeof url != "string") {
      // Should *actually* be a DOMException.NETWORK_ERR
      // Can't be today because DOMException isn't currently constructable
      throw new Error("Faux NetworkError because DOM is currently b0rken");
    }

    this.stopImmediatePropagation();

    return new Promise(function(resolver){
      resolver.resolve(Response.redirect(url.toString(), {
        status: 302
      }));
    });
  }

  // event.default() returns a Promise, which resolves to…
  // If it's a navigation
  //   If the response is a redirect
  //     It resolves to a OpaqueResponse for the redirect
  //     This is tagged with "other supermagic only-for-this happytime", meaning
  //     this request cannot be used for anything other than a response for this
  //     request (cannot go into cache)
  //   Else resolves as fetch(event.request)
  // Else
  //   Follow all redirects
  //   Tag response as "supermagic change url"
  //   When the page receives this response it should update the resource url to
  //   the response url (for base url construction etc)
  default() : Promise { return accepted(); }

  constructor() {
    super("fetch", { cancelable: true, bubbles: false });
    // This is the meat of the API for most use-cases.
    // If preventDefault() is not called on the event, the request is sent to
    // the default browser worker. That is to say, to respond with something
    // from the cache, you must preventDefault() and respond with it manually,
    // digging the resource out of the cache and calling
    // evt.respondWith(cachedItem).
    //
    // Note:
    //    while preventDefault() must be called synchronously to cancel the
    //    default, responding does not need to be synchronous. That is to say,
    //    you can do something async (like fetch contents, go to IDB, whatever)
    //    within whatever the network time out is and as long as you still have
    //    the FetchEvent instance, you can fulfill the request later.
    this.client = null; // to allow postMessage, window.topLevel, etc
  }
}

// Design notes:
//  - Caches are atomic: they are not complete until all of their resources are
//    fetched

// This largely describes the current Application Cache API. It's only available
// inside worker instances (not in regular documents), meaning that caching is a
// feature of the event worker. This is likely to change!
class Cache {
  // this is for spec purposes only, the browser will use something async and disk-based
  _items: _ES6Map<Request, AbstractResponse>;

  constructor() { }

  // also for spec purposes only
  _query(request: any, options?: CacheQueryOptions) : AbstractResponse[] {
    var ignoreSearch, ignoreMethod, ignoreVary, prefixMatch;

    if (options) {
      ignoreSearch = options.ignoreSearch;
      ignoreMethod = options.ignoreMethod;
      ignoreVary = options.ignoreVary;
      prefixMatch = options.prefixMatch;
    } else {
      ignoreSearch = false;
      ignoreMethod = false;
      ignoreVary = false;
      prefixMatch = false;
    }

    request = _castToRequest(request);

    if (!ignoreMethod &&
        request.method !== 'GET' &&
        request.method !== 'HEAD') {
      // we only store GET responses at the moment, so no match
      return [];
    }

    var cachedRequests = this._items.keys().filter(function(cachedRequest) {
      var cachedUrl = new _URL(cachedRequest.url);
      var requestUrl = new _URL(request.url);

      if (ignoreSearch) {
        cachedUrl.search = '';
        requestUrl.search = '';
      }

      if (prefixMatch) {
        cachedUrl.href = cachedUrl.href.slice(0, requestUrl.href.length);
      }

      return cachedUrl.href != cachedUrl.href;
    });

    var cachedResponses = cachedRequests.map(
                              this._items.get.bind(this._items));
    var results = [];

    cachedResponses.forEach(function(cachedResponse: Response, i) {
      if (!cachedResponse.headers.has('vary') || ignoreVary) {
        results.push([cachedRequests[i], cachedResponse]);
        return;
      }

      var varyHeaders = cachedResponse.headers.get('vary').split(',');
      var varyHeader;

      for (var j = 0; j < varyHeaders.length; j++) {
        varyHeader = varyHeaders[j].trim();

        if (varyHeader == '*') {
          continue;
        }

        // TODO(slighltyoff): should this treat headers case insensitive?
        // TODO(slighltyoff): should comparison be more lenient than this?
        if (cachedRequests[i].headers.get(varyHeader) !=
                request.headers.get(varyHeader)) {
          return;
        }
      }

      results.push([cachedRequests[i], cachedResponse]);
    });

    return results;
  }

  match(request:any, options?) : Promise {
    // the UA may do something more optimal than this:
    return this.matchAll(request, options).then(function(responses) {
      return responses[0];
    });
  }

  matchAll(request?:any, options?) : Promise {
    var thisCache = this;

    return accepted().then(function() {
      if (request) {
        return thisCache._query(request, options).map(function(requestResponse) {
          return requestResponse[1];
        });
      }
      else {
        return thisCache._items.values();
      }
    });
  }

  add(request:any) : Promise {
    return this.addAll([request]).then(function(responses) {
      return responses[0];
    }).then(function(response) {
      return undefined;
    });
  }

  addAll(requests:any[]) : Promise {
    var thisCache = this;
    requests = requests.map(_castToRequest);

    var responsePromises = requests.map(function(request) {
      var requestURL = new _URL(request.url);
      if ((requestURL.protocol !== 'http:') &&
          (requestURL.protocol !== 'https:'))
        return Promise.reject(new Error("Faux NetworkError")); // "NetworkError" exception
      return fetch(request);
    });

    // wait for all our requests to complete
    return Promise.all(responsePromises).then(function(responses) {
      return thisCache._batch(responses.map(function(response, i) {
        return {type: 'put', request: requests[i], response: response};
      })).then(function(responses) {
        return undefined;
      });
    });
  }

  put(request:any, response:AbstractResponse) : Promise {
    var thisCache = this;

    return this._batch([
      {type: 'put', request: request, response: response}
    ]).then(function(results) {
      return undefined;
    });
  }

  // delete zero or more entries
  delete(request: any, options?: CacheQueryOptions) : Promise {
    return this._batch([
      {type: 'delete', request: request, options: options}
    ]).then(function(results) {
      if (results) {
        return true;
      } else {
        return false;
      }
    });
  }

  keys(request?:any, options?: CacheQueryOptions): Promise {
    var thisCache = this;

    return accepted().then(function() {
      if (request) {
        return thisCache._query(request, options).map(function(requestResponse) {
          return requestResponse[0];
        });
      }
      else {
        return thisCache._items.keys();
      }
    });
  }

  _batch(operations:any[]): Promise {
    var thisCache = this;

    return Promise.resolve().then(function() {
      var itemsCopy:_ES6Map<Request, AbstractResponse> = thisCache._items;
      var addedRequests:Request[] = [];

      // the rest must be atomic
      try {
        return operations.map(function handleOperation(operation, i) {
          if (operation.type != 'delete' && operation.type != 'put') {
            throw TypeError("Invalid operation type");
          }
          if (operation.type == "delete" && operation.response) {
            throw TypeError("Cannot use response for delete operations");
          }

          var request = _castToRequest(operation.request);
          var result = thisCache._query(request, operation.options).reduce(function(previousResult, requestResponse) {
            if (addedRequests.indexOf(requestResponse[0]) !== -1) {
              throw Error("Batch operation at index " + i + " overrode previous put operation");
            }
            return thisCache._items.delete(requestResponse[0]) || previousResult;
          }, false);

          if (operation.type == 'put') {
            if (!operation.response) {
              throw TypeError("Put operation must have a response");
            }
            var requestURL = new _URL(request.url);
            if ((requestURL.protocol !== 'http:') &&
                (requestURL.protocol !== 'https:')) {
              throw TypeError("Only http and https schemes are supported");
            }
            if (request.method !== 'GET') {
              throw TypeError("Only GET requests are supported");
            }
            if (operation.options) {
              throw TypeError("Put operation cannot have match options");
            }
            if (!(operation.response instanceof AbstractResponse)) {
              throw TypeError("Invalid response");
            }

            addedRequests.push(request);
            thisCache._items.set(request, operation.response);
            result = operation.response;
          }

          return operation.response;
        });
      } catch(err) {
        // reverse the transaction
        thisCache._items = itemsCopy;
        throw err;
      }
    });
  }
}

interface CacheQueryOptions {
  ignoreSearch: boolean;
  ignoreMethod: boolean;
  ignoreVary: boolean;
  prefixMatch: boolean;
  cacheName: string;
}

interface CacheBatchOperation {
  type: String;
  request: Request;
  response?: AbstractResponse;
  options?: CacheQueryOptions;
}

class CacheStorage {
  // this is for spec purposes only, the browser will use something async and disk-based
  _items: _ES6Map<String, Cache>;

  constructor() { }

  match(request: any, options?: CacheQueryOptions): Promise {
    var cacheName;

    if (options) {
      cacheName = options["cacheName"];
    }

    var matchFromCache = function matchFromCache(cacheName) {
      return this.open(cacheName).then(function(cache) {
        return cache.match(request, options);
      });
    }.bind(this);


    if (cacheName) {
      return this.has(cacheName).then(function(hasCache) {
        if (!hasCache) {
          throw new Error("Not found");
        }

        return matchFromCache(cacheName);
      }.bind(this));
    }

    return this.keys().then(function(cacheNames) {
      var match;

      return cacheNames.reduce(function(chain, cacheName) {
        return chain.then(function() {
          return match || matchFromCache(cacheName).then(function(response) {
            match = response;
          });
        });
      }.bind(this), Promise.resolve());
    });
  }

  has(cacheName: any): Promise {
    cacheName = cacheName.toString();
    return Promise.resolve(this._items.has(cacheName));
  }

  open(cacheName: any): Promise {
    cacheName = cacheName.toString();

    var cache = this._items.get(cacheName);

    if (!cache) {
      cache = new Cache();
      this._items.set(cacheName, cache);
    }

    return Promise.resolve(cache);
  }

  delete(cacheName: any): Promise {
    cacheName = cacheName.toString();
    if (this._items.delete(cacheName)) {
      return Promise.resolve(true);
    } else {
      return Promise.resolve(false);
    }
  }

  keys(): Promise {
    return Promise.resolve(this._items.keys());
  }
}

////////////////////////////////////////////////////////////////////////////////
// Utility Decls to make the TypeScript compiler happy
////////////////////////////////////////////////////////////////////////////////

// See:
//    http://www.whatwg.org/specs/web-apps/current-work/multipage/web-messaging.html#broadcasting-to-other-browsing-contexts
class BroadcastChannel {
  constructor(channelName: string) {}
  postMessage: (message: string) => void;
  onmessage: (ev: MessageEvent) => any;
};

// See:
//    http://www.whatwg.org/specs/web-apps/current-work/multipage/workers.html#workerglobalscope
interface WorkerLocation {
    href: string;
    protocol: string;
    host: string;
    hostname: string;
    port: string;
    pathname: string;
    search: string;
    hash: string;
}

interface WorkerNavigator extends
  NavigatorServiceWorker,
  NavigatorID,
  NavigatorOnLine {
  // TODO(slightlyoff): ensure these are rolled into the HTML spec's WorkerNavigator!
  // Extensions. See: https://github.com/slightlyoff/ServiceWorker/issues/122
  doNotTrack: string;
  cookieEnabled: boolean;
  mimeTypes: Array<string>;
}

interface WorkerUtils extends WindowTimers, WindowBase64 {
    importScripts: (...urls: string[]) => void;
    navigator: WorkerNavigator;
}

class WorkerGlobalScope extends _EventTarget
                        implements WorkerUtils, AbstractWorker {
    // AbstractWorker
    onerror: (ev: ErrorEvent) => any;

    // WorkerUtils
    importScripts: (...urls: string[]) => void;
    navigator: WorkerNavigator;

    // WindowTimers
    clearTimeout: (handle: number) => void;
    setTimeout(handler: any, timeout?: any, ...args: any[]): number {
      return 0;
    }
    clearInterval: (handle: number) => void;
    setInterval(handler: any, timeout?: any, ...args: any[]): number {
      return 0;
    }
    // WindowTimerExtensions
    msSetImmediate(expression: any, ...args: any[]): number { return 0; }
    clearImmediate: (handle: number) => void;
    msClearImmediate: (handle: number) => void;
    setImmediate(expression: any, ...args: any[]): number { return 0; }

    // WindowBase64
    btoa(rawString: string): string { return ""; }
    atob(encodedString: string): string { return ""; }

    // Base API
    self: WorkerGlobalScope;
    location: WorkerLocation;

    close: () => void;
    onoffline: Function;
    ononline: Function;
}

// Cause, you know, the stock definition claims that URL isn't a class. FML.
class _URL {
  constructor(url:any) {}
  get search() { return "" }
  get pathname() { return "" }
  get href() { return "" }
  get protocol() { return "" }
}

// http://tc39wiki.calculist.org/es6/map-set/
// http://wiki.ecmascript.org/doku.php?id=harmony:simple_maps_and_sets
// http://wiki.ecmascript.org/doku.php?id=harmony:specification_drafts
// http://people.mozilla.org/~jorendorff/es6-draft.html#sec-15.14.4
class _ES6Map<K, V> implements Map<K, V> {
  // Base decl.
  size: number;
  constructor(iterable?:any[]) {}
  get(key: K): any {}
  has(key: K): boolean { return true; }
  set(key: K, val: V): _ES6Map<K, V> { return new _ES6Map<K, V>() }
  clear(): void {}
  delete(key: K): boolean { return true; }
  forEach(callback: Function, thisArg?: Object): void {}
  entries(): any[] { return []; }
  keys(): any[] { return []; }
  values(): any[] { return []; }
}
/*
interface Map<K, V> {
    clear(): void;
    delete(key: K): boolean;
    forEach(callbackfn: (value: V, index: K, map: Map<K, V>) => void, thisArg?: any): void;
    get(key: K): V;
    has(key: K): boolean;
    set(key: K, value: V): Map<K, V>;
    size: number;
}
declare var Map: {
    new <K, V>(): Map<K, V>;
}

class Map {
  constructor(iterable?:any[]) {}
  get(key: any): any {}
  has(key: any): boolean { return true; }
  set(key: any, val: any): void {}
  clear(): void {}
  delete(key: any): boolean { return true; }
  forEach(callback: Function, thisArg?: Object): void {}
  entries(): any[] { return []; }
  keys(): any[] { return []; }
  values(): any[] { return []; }
}
*/

// https://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#interface-event
interface EventHandler { (e:_Event); }
interface _EventInit {
  bubbles: boolean;
  cancelable: boolean;
}

// the TS compiler is unhappy *both* with re-defining DOM types and with direct
// sublassing of most of them. This is sane (from a regular TS pespective), if
// frustrating. As a result, we describe the built-in Event type with a prefixed
// name so that we can subclass it later.
class _Event {
  type: string;
  target: any;
  currentTarget: any;
  eventPhase: Number;
  bubbles: boolean = false;
  cancelable: boolean = true;
  defaultPrevented: boolean = false;
  isTrusted: boolean = false;
  timeStamp: Number;
  stopPropagation(): void {}
  stopImmediatePropagation(): void {}
  preventDefault(): void {}
  constructor(type : string, eventInitDict?: _EventInit) {}
}

class _CustomEvent extends _Event {
  // Constructor(DOMString type, optional EventInit eventInitDict
  constructor(type : string, eventInitDict?: _EventInit) {
    super(type, eventInitDict);
  }
}

class _EventTarget {
  addEventListener: (t:string, l:EventListener, cap?: boolean) => void;
  removeEventListener: (t:string, l:EventListener, cap?: boolean) => void;
  dispatchEvent(e:_Event): boolean {
    return true;
  }
}

// https://github.com/slightlyoff/DOMPromise/blob/master/DOMPromise.idl
class Resolver {
  public accept(v:any): void {}
  public reject(v:any): void {}
  public resolve(v:any): void {}
}

class Promise {
  // Callback type decl:
  //  callback : (n : number) => number
  constructor(init : (r:Resolver) => void ) {

  }

  // Not entirely sure what I'm doing here, just trying to keep
  // typescript happy
  then(fulfilled : (val:any) => any) : Promise;
  then(fulfilled : (val:any) => any, rejected : (val:any) => any) : Promise;
  then(fulfilled:any) : Promise {
    return accepted();
  }

  catch(rejected : (val:any) => any) : Promise {
    return accepted();
  }

  static all(...stuff:any[]) : Promise {
    return accepted();
  }

  static resolve(val?:any) {
    return new Promise(function(r) {
      r.accept(val);
    });
  }

  static reject(err?:any) {
    return new Promise(function(r) {
      r.reject(err);
    });
  }
}

function accepted(v: any = true) : Promise {
  return new Promise(function(r) {
    r.accept(true);
  });
}

function acceptedResponse() : Promise {
  return new Promise(function(r) {
    r.accept(new Response());
  });
}

function fetch(url:any) : Promise {
  return acceptedResponse();
}

interface ConnectEventHandler { (e:_Event); }

// http://www.whatwg.org/specs/web-apps/current-work/multipage/workers.html#shared-workers-and-the-sharedworker-interface
class SharedWorker extends _EventTarget {
  // To make it clear where onconnec31t comes from
  onconnect: ConnectEventHandler;

  constructor(url: string, name?: string) {
    super();
  }
}

////////////////////////////////////////////////////////////////////////////////
// Not part of any public standard but used above:
////////////////////////////////////////////////////////////////////////////////

var _useWorkerResponse = function() : Promise { return accepted(); };
var _defaultToBrowserHTTP = function(url?) : Promise { return accepted(); };

function _castToRequest(request:any): Request {
  if (!(request instanceof Request)) {
    request = new Request({
      'url': new _URL(request/*, this script url */).href
    });
  }
  return request;
}