8 files changed, 500 insertions, 33 deletions

diff --git a/js/dom_types.ts b/js/dom_types.ts
index 4bfb3e041..549b0057c 100644
--- a/js/dom_types.ts
+++ b/js/dom_types.ts
@@ -53,14 +53,6 @@ export interface DomIterable<K, V> {
   ): void;
 }
 
-interface Element {
-  // TODO
-}
-
-export interface HTMLFormElement {
-  // TODO
-}
-
 type EndingType = "transparent" | "native";
 
 export interface BlobPropertyBag {
@@ -72,7 +64,7 @@ interface AbortSignalEventMap {
   abort: ProgressEvent;
 }
 
-interface EventTarget {
+export interface EventTarget {
   addEventListener(
     type: string,
     listener: EventListenerOrEventListenerObject | null,
@@ -140,39 +132,52 @@ export interface URLSearchParams {
   ): void;
 }
 
-interface EventListener {
+export interface EventListener {
   (evt: Event): void;
 }
 
-interface EventInit {
+export interface EventInit {
   bubbles?: boolean;
   cancelable?: boolean;
   composed?: boolean;
 }
 
-interface Event {
+export enum EventPhase {
+  NONE = 0,
+  CAPTURING_PHASE = 1,
+  AT_TARGET = 2,
+  BUBBLING_PHASE = 3
+}
+
+export interface EventPath {
+  item: EventTarget;
+  itemInShadowTree: boolean;
+  relatedTarget: EventTarget | null;
+  rootOfClosedTree: boolean;
+  slotInClosedTree: boolean;
+  target: EventTarget | null;
+  touchTargetList: EventTarget[];
+}
+
+export interface Event {
+  readonly type: string;
+  readonly target: EventTarget | null;
+  readonly currentTarget: EventTarget | null;
+  composedPath(): EventPath[];
+
+  readonly eventPhase: number;
+
+  stopPropagation(): void;
+  stopImmediatePropagation(): void;
+
   readonly bubbles: boolean;
-  cancelBubble: boolean;
   readonly cancelable: boolean;
-  readonly composed: boolean;
-  readonly currentTarget: EventTarget | null;
+  preventDefault(): void;
   readonly defaultPrevented: boolean;
-  readonly eventPhase: number;
+  readonly composed: boolean;
+
   readonly isTrusted: boolean;
-  returnValue: boolean;
-  readonly srcElement: Element | null;
-  readonly target: EventTarget | null;
-  readonly timeStamp: number;
-  readonly type: string;
-  deepPath(): EventTarget[];
-  initEvent(type: string, bubbles?: boolean, cancelable?: boolean): void;
-  preventDefault(): void;
-  stopImmediatePropagation(): void;
-  stopPropagation(): void;
-  readonly AT_TARGET: number;
-  readonly BUBBLING_PHASE: number;
-  readonly CAPTURING_PHASE: number;
-  readonly NONE: number;
+  readonly timeStamp: Date;
 }
 
 /* TODO(ry) Re-expose this interface. There is currently some interference
@@ -193,11 +198,11 @@ interface ProgressEvent extends Event {
   readonly total: number;
 }
 
-interface EventListenerOptions {
+export interface EventListenerOptions {
   capture?: boolean;
 }
 
-interface AddEventListenerOptions extends EventListenerOptions {
+export interface AddEventListenerOptions extends EventListenerOptions {
   once?: boolean;
   passive?: boolean;
 }
@@ -236,7 +241,7 @@ export interface ReadableStream {
   getReader(): ReadableStreamReader;
 }
 
-interface EventListenerObject {
+export interface EventListenerObject {
   handleEvent(evt: Event): void;
 }
 
diff --git a/js/event.ts b/js/event.ts
new file mode 100644
index 000000000..29fd8177b
--- /dev/null
+++ b/js/event.ts
@@ -0,0 +1,252 @@
+// Copyright 2018 the Deno authors. All rights reserved. MIT license.
+import * as domTypes from "./dom_types";
+import { getPrivateValue } from "./util";
+
+// WeakMaps are recommended for private attributes (see MDN link below)
+// tslint:disable-next-line:max-line-length
+// https://developer.mozilla.org/en-US/docs/Archive/Add-ons/Add-on_SDK/Guides/Contributor_s_Guide/Private_Properties#Using_WeakMaps
+export const eventAttributes = new WeakMap();
+
+export class EventInit implements domTypes.EventInit {
+  bubbles = false;
+  cancelable = false;
+  composed = false;
+
+  constructor({ bubbles = false, cancelable = false, composed = false } = {}) {
+    this.bubbles = bubbles;
+    this.cancelable = cancelable;
+    this.composed = composed;
+  }
+}
+
+export class Event implements domTypes.Event {
+  // Each event has the following associated flags
+  private _canceledFlag = false;
+  private _inPassiveListenerFlag = false;
+  private _stopImmediatePropagationFlag = false;
+  private _stopPropagationFlag = false;
+
+  // Property for objects on which listeners will be invoked
+  private _path: domTypes.EventPath[] = [];
+
+  constructor(type: string, eventInitDict: domTypes.EventInit = {}) {
+    eventAttributes.set(this, {
+      type,
+      bubbles: eventInitDict.bubbles || false,
+      cancelable: eventInitDict.cancelable || false,
+      composed: eventInitDict.composed || false,
+      currentTarget: null,
+      eventPhase: domTypes.EventPhase.NONE,
+      isTrusted: false,
+      target: null,
+      timeStamp: Date.now()
+    });
+  }
+
+  get bubbles(): boolean {
+    return getPrivateValue(this, eventAttributes, "bubbles");
+  }
+
+  get cancelBubble(): boolean {
+    return this._stopPropagationFlag;
+  }
+
+  get cancelBubbleImmediately(): boolean {
+    return this._stopImmediatePropagationFlag;
+  }
+
+  get cancelable(): boolean {
+    return getPrivateValue(this, eventAttributes, "cancelable");
+  }
+
+  get composed(): boolean {
+    return getPrivateValue(this, eventAttributes, "composed");
+  }
+
+  get currentTarget(): domTypes.EventTarget {
+    return getPrivateValue(this, eventAttributes, "currentTarget");
+  }
+
+  get defaultPrevented(): boolean {
+    return this._canceledFlag;
+  }
+
+  get eventPhase(): number {
+    return getPrivateValue(this, eventAttributes, "eventPhase");
+  }
+
+  get isTrusted(): boolean {
+    return getPrivateValue(this, eventAttributes, "isTrusted");
+  }
+
+  get target(): domTypes.EventTarget {
+    return getPrivateValue(this, eventAttributes, "target");
+  }
+
+  get timeStamp(): Date {
+    return getPrivateValue(this, eventAttributes, "timeStamp");
+  }
+
+  get type(): string {
+    return getPrivateValue(this, eventAttributes, "type");
+  }
+
+  /** Returns the event’s path (objects on which listeners will be
+   * invoked). This does not include nodes in shadow trees if the
+   * shadow root was created with its ShadowRoot.mode closed.
+   *
+   *      event.composedPath();
+   */
+  composedPath(): domTypes.EventPath[] {
+    if (this._path.length === 0) {
+      return [];
+    }
+
+    const composedPath: domTypes.EventPath[] = [
+      {
+        item: this.currentTarget,
+        itemInShadowTree: false,
+        relatedTarget: null,
+        rootOfClosedTree: false,
+        slotInClosedTree: false,
+        target: null,
+        touchTargetList: []
+      }
+    ];
+
+    let currentTargetIndex = 0;
+    let currentTargetHiddenSubtreeLevel = 0;
+
+    for (let index = this._path.length - 1; index >= 0; index--) {
+      const { item, rootOfClosedTree, slotInClosedTree } = this._path[index];
+
+      if (rootOfClosedTree) {
+        currentTargetHiddenSubtreeLevel++;
+      }
+
+      if (item === this.currentTarget) {
+        currentTargetIndex = index;
+        break;
+      }
+
+      if (slotInClosedTree) {
+        currentTargetHiddenSubtreeLevel--;
+      }
+    }
+
+    let currentHiddenLevel = currentTargetHiddenSubtreeLevel;
+    let maxHiddenLevel = currentTargetHiddenSubtreeLevel;
+
+    for (let i = currentTargetIndex - 1; i >= 0; i--) {
+      const { item, rootOfClosedTree, slotInClosedTree } = this._path[i];
+
+      if (rootOfClosedTree) {
+        currentHiddenLevel++;
+      }
+
+      if (currentHiddenLevel <= maxHiddenLevel) {
+        composedPath.unshift({
+          item,
+          itemInShadowTree: false,
+          relatedTarget: null,
+          rootOfClosedTree: false,
+          slotInClosedTree: false,
+          target: null,
+          touchTargetList: []
+        });
+      }
+
+      if (slotInClosedTree) {
+        currentHiddenLevel--;
+
+        if (currentHiddenLevel < maxHiddenLevel) {
+          maxHiddenLevel = currentHiddenLevel;
+        }
+      }
+    }
+
+    currentHiddenLevel = currentTargetHiddenSubtreeLevel;
+    maxHiddenLevel = currentTargetHiddenSubtreeLevel;
+
+    for (
+      let index = currentTargetIndex + 1;
+      index < this._path.length;
+      index++
+    ) {
+      const { item, rootOfClosedTree, slotInClosedTree } = this._path[index];
+
+      if (slotInClosedTree) {
+        currentHiddenLevel++;
+      }
+
+      if (currentHiddenLevel <= maxHiddenLevel) {
+        composedPath.push({
+          item,
+          itemInShadowTree: false,
+          relatedTarget: null,
+          rootOfClosedTree: false,
+          slotInClosedTree: false,
+          target: null,
+          touchTargetList: []
+        });
+      }
+
+      if (rootOfClosedTree) {
+        currentHiddenLevel--;
+
+        if (currentHiddenLevel < maxHiddenLevel) {
+          maxHiddenLevel = currentHiddenLevel;
+        }
+      }
+    }
+
+    return composedPath;
+  }
+
+  /** Cancels the event (if it is cancelable).
+   * See https://dom.spec.whatwg.org/#set-the-canceled-flag
+   *
+   *      event.preventDefault();
+   */
+  preventDefault(): void {
+    if (this.cancelable && !this._inPassiveListenerFlag) {
+      this._canceledFlag = true;
+    }
+  }
+
+  /** Stops the propagation of events further along in the DOM.
+   *
+   *      event.stopPropagation();
+   */
+  stopPropagation(): void {
+    this._stopPropagationFlag = true;
+  }
+
+  /** For this particular event, no other listener will be called.
+   * Neither those attached on the same element, nor those attached
+   * on elements which will be traversed later (in capture phase,
+   * for instance).
+   *
+   *      event.stopImmediatePropagation();
+   */
+  stopImmediatePropagation(): void {
+    this._stopPropagationFlag = true;
+    this._stopImmediatePropagationFlag = true;
+  }
+}
+
+/** Built-in objects providing `get` methods for our
+ * interceptable JavaScript operations.
+ */
+Reflect.defineProperty(Event.prototype, "bubbles", { enumerable: true });
+Reflect.defineProperty(Event.prototype, "cancelable", { enumerable: true });
+Reflect.defineProperty(Event.prototype, "composed", { enumerable: true });
+Reflect.defineProperty(Event.prototype, "currentTarget", { enumerable: true });
+Reflect.defineProperty(Event.prototype, "defaultPrevented", {
+  enumerable: true
+});
+Reflect.defineProperty(Event.prototype, "eventPhase", { enumerable: true });
+Reflect.defineProperty(Event.prototype, "isTrusted", { enumerable: true });
+Reflect.defineProperty(Event.prototype, "target", { enumerable: true });
+Reflect.defineProperty(Event.prototype, "timeStamp", { enumerable: true });
+Reflect.defineProperty(Event.prototype, "type", { enumerable: true });
diff --git a/js/event_target.ts b/js/event_target.ts
new file mode 100644
index 000000000..3226fde96
--- /dev/null
+++ b/js/event_target.ts
@@ -0,0 +1,52 @@
+// Copyright 2018 the Deno authors. All rights reserved. MIT license.
+import * as domTypes from "./dom_types";
+
+/* TODO: This is an incomplete implementation to provide functionality
+ * for Event. A proper spec is still required for a proper Web API.
+ */
+export class EventTarget implements domTypes.EventTarget {
+  public listeners: {
+    [type in string]: domTypes.EventListenerOrEventListenerObject[]
+  } = {};
+
+  public addEventListener(
+    type: string,
+    listener: domTypes.EventListenerOrEventListenerObject | null,
+    options?: boolean | domTypes.AddEventListenerOptions
+  ): void {
+    if (!(type in this.listeners)) {
+      this.listeners[type] = [];
+    }
+    if (listener !== null) {
+      this.listeners[type].push(listener);
+    }
+  }
+
+  public removeEventListener(
+    type: string,
+    callback: domTypes.EventListenerOrEventListenerObject | null,
+    options?: domTypes.EventListenerOptions | boolean
+  ): void {
+    if (type in this.listeners && callback !== null) {
+      this.listeners[type] = this.listeners[type].filter(
+        listener => listener !== callback
+      );
+    }
+  }
+
+  public dispatchEvent(event: domTypes.Event): boolean {
+    if (!(event.type in this.listeners)) {
+      return true;
+    }
+    const stack = this.listeners[event.type].slice();
+
+    for (const stackElement of stack) {
+      if ((stackElement as domTypes.EventListenerObject).handleEvent) {
+        (stackElement as domTypes.EventListenerObject).handleEvent(event);
+      } else {
+        (stackElement as domTypes.EventListener).call(this, event);
+      }
+    }
+    return !event.defaultPrevented;
+  }
+}
diff --git a/js/event_target_test.ts b/js/event_target_test.ts
new file mode 100644
index 000000000..ebb92c7f0
--- /dev/null
+++ b/js/event_target_test.ts
@@ -0,0 +1,66 @@
+// Copyright 2018 the Deno authors. All rights reserved. MIT license.
+import { test, assert, assertEqual } from "./test_util.ts";
+
+test(function addEventListenerTest() {
+  const document = new EventTarget();
+
+  assertEqual(document.addEventListener("x", null, false), undefined);
+  assertEqual(document.addEventListener("x", null, true), undefined);
+  assertEqual(document.addEventListener("x", null), undefined);
+});
+
+test(function constructedEventTargetCanBeUsedAsExpected() {
+  const target = new EventTarget();
+  const event = new Event("foo", { bubbles: true, cancelable: false });
+  let callCount = 0;
+
+  function listener(e) {
+    assertEqual(e, event);
+    ++callCount;
+  }
+
+  target.addEventListener("foo", listener);
+
+  target.dispatchEvent(event);
+  assertEqual(callCount, 1);
+
+  target.dispatchEvent(event);
+  assertEqual(callCount, 2);
+
+  target.removeEventListener("foo", listener);
+  target.dispatchEvent(event);
+  assertEqual(callCount, 2);
+});
+
+test(function anEventTargetCanBeSubclassed() {
+  class NicerEventTarget extends EventTarget {
+    on(type, listener?, options?) {
+      this.addEventListener(type, listener, options);
+    }
+
+    off(type, callback?, options?) {
+      this.removeEventListener(type, callback, options);
+    }
+  }
+
+  const target = new NicerEventTarget();
+  const event = new Event("foo", { bubbles: true, cancelable: false });
+  let callCount = 0;
+
+  function listener() {
+    ++callCount;
+  }
+
+  target.on("foo", listener);
+  assertEqual(callCount, 0);
+
+  target.off("foo", listener);
+  assertEqual(callCount, 0);
+});
+
+test(function removingNullEventListenerShouldSucceed() {
+  const document = new EventTarget();
+  assertEqual(document.removeEventListener("x", null, false), undefined);
+  assertEqual(document.removeEventListener("x", null, true), undefined);
+  assertEqual(document.removeEventListener("x", null), undefined);
+});
diff --git a/js/event_test.ts b/js/event_test.ts
new file mode 100644
index 000000000..3a1254956
--- /dev/null
+++ b/js/event_test.ts
@@ -0,0 +1,70 @@
+// Copyright 2018 the Deno authors. All rights reserved. MIT license.
+import { test, assertEqual } from "./test_util.ts";
+
+test(function eventInitializedWithType() {
+  const type = "click";
+  const event = new Event(type);
+
+  assertEqual(event.isTrusted, false);
+  assertEqual(event.target, null);
+  assertEqual(event.currentTarget, null);
+  assertEqual(event.type, "click");
+  assertEqual(event.bubbles, false);
+  assertEqual(event.cancelable, false);
+});
+
+test(function eventInitializedWithTypeAndDict() {
+  const init = "submit";
+  const eventInitDict = new EventInit({ bubbles: true, cancelable: true });
+  const event = new Event(init, eventInitDict);
+
+  assertEqual(event.isTrusted, false);
+  assertEqual(event.target, null);
+  assertEqual(event.currentTarget, null);
+  assertEqual(event.type, "submit");
+  assertEqual(event.bubbles, true);
+  assertEqual(event.cancelable, true);
+});
+
+test(function eventComposedPathSuccess() {
+  const type = "click";
+  const event = new Event(type);
+  const composedPath = event.composedPath();
+
+  assertEqual(composedPath, []);
+});
+
+test(function eventStopPropagationSuccess() {
+  const type = "click";
+  const event = new Event(type);
+
+  assertEqual(event.cancelBubble, false);
+  event.stopPropagation();
+  assertEqual(event.cancelBubble, true);
+});
+
+test(function eventStopImmediatePropagationSuccess() {
+  const type = "click";
+  const event = new Event(type);
+
+  assertEqual(event.cancelBubble, false);
+  assertEqual(event.cancelBubbleImmediately, false);
+  event.stopImmediatePropagation();
+  assertEqual(event.cancelBubble, true);
+  assertEqual(event.cancelBubbleImmediately, true);
+});
+
+test(function eventPreventDefaultSuccess() {
+  const type = "click";
+  const event = new Event(type);
+
+  assertEqual(event.defaultPrevented, false);
+  event.preventDefault();
+  assertEqual(event.defaultPrevented, false);
+
+  const eventInitDict = new EventInit({ bubbles: true, cancelable: true });
+  const cancelableEvent = new Event(type, eventInitDict);
+  assertEqual(cancelableEvent.defaultPrevented, false);
+  cancelableEvent.preventDefault();
+  assertEqual(cancelableEvent.defaultPrevented, true);
+});
diff --git a/js/globals.ts b/js/globals.ts
index efa377e9b..663215341 100644
--- a/js/globals.ts
+++ b/js/globals.ts
@@ -10,6 +10,8 @@
 import * as blob from "./blob";
 import * as consoleTypes from "./console";
 import * as domTypes from "./dom_types";
+import * as event from "./event";
+import * as eventTarget from "./event_target";
 import * as formData from "./form_data";
 import * as fetchTypes from "./fetch";
 import * as headers from "./headers";
@@ -61,6 +63,12 @@ export type Blob = blob.DenoBlob;
 // window.File = file.DenoFile;
 // export type File = file.DenoFile;
 
+window.EventInit = event.EventInit;
+export type EventInit = event.EventInit;
+window.Event = event.Event;
+export type Event = event.Event;
+window.EventTarget = eventTarget.EventTarget;
+export type EventTarget = eventTarget.EventTarget;
 window.URL = url.URL;
 export type URL = url.URL;
 window.URLSearchParams = urlSearchParams.URLSearchParams;
diff --git a/js/unit_tests.ts b/js/unit_tests.ts
index b24a156d5..73298297b 100644
--- a/js/unit_tests.ts
+++ b/js/unit_tests.ts
@@ -10,6 +10,8 @@ import "./compiler_test.ts";
 import "./console_test.ts";
 import "./copy_file_test.ts";
 import "./dir_test.ts";
+import "./event_test.ts";
+import "./event_target_test.ts";
 import "./fetch_test.ts";
 // TODO The global "File" has been temporarily disabled. See the note in
 // js/globals.ts
diff --git a/js/util.ts b/js/util.ts
index 58e865337..ec24ec5bd 100644
--- a/js/util.ts
+++ b/js/util.ts
@@ -151,3 +151,15 @@ export function requiredArguments(
     throw new TypeError(errMsg);
   }
 }
+
+// Returns values from a WeakMap to emulate private properties in JavaScript
+export function getPrivateValue<
+  K extends object,
+  V extends object,
+  W extends keyof V
+>(instance: K, weakMap: WeakMap<K, V>, key: W): V[W] {
+  if (weakMap.has(instance)) {
+    return weakMap.get(instance)![key];
+  }
+  throw new TypeError("Illegal invocation");
+}