1 files changed, 315 insertions, 0 deletions
diff --git a/cli/js/web/timers.ts b/cli/js/web/timers.ts
new file mode 100644
index 000000000..806b7c160
--- /dev/null
+++ b/cli/js/web/timers.ts
@@ -0,0 +1,315 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+import { assert } from "../util.ts";
+import { startGlobalTimer, stopGlobalTimer } from "../ops/timers.ts";
+import { RBTree } from "../rbtree.ts";
+
+const { console } = globalThis;
+
+interface Timer {
+  id: number;
+  callback: () => void;
+  delay: number;
+  due: number;
+  repeat: boolean;
+  scheduled: boolean;
+}
+
+// Timeout values > TIMEOUT_MAX are set to 1.
+const TIMEOUT_MAX = 2 ** 31 - 1;
+
+let globalTimeoutDue: number | null = null;
+
+let nextTimerId = 1;
+const idMap = new Map<number, Timer>();
+type DueNode = { due: number; timers: Timer[] };
+const dueTree = new RBTree<DueNode>((a, b) => a.due - b.due);
+
+function clearGlobalTimeout(): void {
+  globalTimeoutDue = null;
+  stopGlobalTimer();
+}
+
+let pendingEvents = 0;
+const pendingFireTimers: Timer[] = [];
+let hasPendingFireTimers = false;
+let pendingScheduleTimers: Timer[] = [];
+
+async function setGlobalTimeout(due: number, now: number): Promise<void> {
+  // Since JS and Rust don't use the same clock, pass the time to rust as a
+  // relative time value. On the Rust side we'll turn that into an absolute
+  // value again.
+  const timeout = due - now;
+  assert(timeout >= 0);
+  // Send message to the backend.
+  globalTimeoutDue = due;
+  pendingEvents++;
+  // FIXME(bartlomieju): this is problematic, because `clearGlobalTimeout`
+  // is synchronous. That means that timer is cancelled, but this promise is still pending
+  // until next turn of event loop. This leads to "leaking of async ops" in tests;
+  // because `clearTimeout/clearInterval` might be the last statement in test function
+  // `opSanitizer` will immediately complain that there is pending op going on, unless
+  // some timeout/defer is put in place to allow promise resolution.
+  // Ideally `clearGlobalTimeout` doesn't return until this op is resolved, but
+  // I'm not if that's possible.
+  await startGlobalTimer(timeout);
+  pendingEvents--;
+  // eslint-disable-next-line @typescript-eslint/no-use-before-define
+  fireTimers();
+}
+
+function setOrClearGlobalTimeout(due: number | null, now: number): void {
+  if (due == null) {
+    clearGlobalTimeout();
+  } else {
+    setGlobalTimeout(due, now);
+  }
+}
+
+function schedule(timer: Timer, now: number): void {
+  assert(!timer.scheduled);
+  assert(now <= timer.due);
+  // There are more timers pending firing.
+  // We must ensure new timer scheduled after them.
+  // Push them to a queue that would be depleted after last pending fire
+  // timer is fired.
+  // (This also implies behavior of setInterval)
+  if (hasPendingFireTimers) {
+    pendingScheduleTimers.push(timer);
+    return;
+  }
+  // Find or create the list of timers that will fire at point-in-time `due`.
+  const maybeNewDueNode = { due: timer.due, timers: [] };
+  let dueNode = dueTree.find(maybeNewDueNode);
+  if (dueNode === null) {
+    dueTree.insert(maybeNewDueNode);
+    dueNode = maybeNewDueNode;
+  }
+  // Append the newly scheduled timer to the list and mark it as scheduled.
+  dueNode!.timers.push(timer);
+  timer.scheduled = true;
+  // If the new timer is scheduled to fire before any timer that existed before,
+  // update the global timeout to reflect this.
+  if (globalTimeoutDue === null || globalTimeoutDue > timer.due) {
+    setOrClearGlobalTimeout(timer.due, now);
+  }
+}
+
+function unschedule(timer: Timer): void {
+  // Check if our timer is pending scheduling or pending firing.
+  // If either is true, they are not in tree, and their idMap entry
+  // will be deleted soon. Remove it from queue.
+  let index = -1;
+  if ((index = pendingScheduleTimers.indexOf(timer)) >= 0) {
+    pendingScheduleTimers.splice(index);
+    return;
+  }
+  if ((index = pendingFireTimers.indexOf(timer)) >= 0) {
+    pendingFireTimers.splice(index);
+    return;
+  }
+  // If timer is not in the 2 pending queues and is unscheduled,
+  // it is not in the tree.
+  if (!timer.scheduled) {
+    return;
+  }
+  const searchKey = { due: timer.due, timers: [] };
+  // Find the list of timers that will fire at point-in-time `due`.
+  const list = dueTree.find(searchKey)!.timers;
+  if (list.length === 1) {
+    // Time timer is the only one in the list. Remove the entire list.
+    assert(list[0] === timer);
+    dueTree.remove(searchKey);
+    // If the unscheduled timer was 'next up', find when the next timer that
+    // still exists is due, and update the global alarm accordingly.
+    if (timer.due === globalTimeoutDue) {
+      const nextDueNode: DueNode | null = dueTree.min();
+      setOrClearGlobalTimeout(nextDueNode && nextDueNode.due, Date.now());
+    }
+  } else {
+    // Multiple timers that are due at the same point in time.
+    // Remove this timer from the list.
+    const index = list.indexOf(timer);
+    assert(index > -1);
+    list.splice(index, 1);
+  }
+}
+
+function fire(timer: Timer): void {
+  // If the timer isn't found in the ID map, that means it has been cancelled
+  // between the timer firing and the promise callback (this function).
+  if (!idMap.has(timer.id)) {
+    return;
+  }
+  // Reschedule the timer if it is a repeating one, otherwise drop it.
+  if (!timer.repeat) {
+    // One-shot timer: remove the timer from this id-to-timer map.
+    idMap.delete(timer.id);
+  } else {
+    // Interval timer: compute when timer was supposed to fire next.
+    // However make sure to never schedule the next interval in the past.
+    const now = Date.now();
+    timer.due = Math.max(now, timer.due + timer.delay);
+    schedule(timer, now);
+  }
+  // Call the user callback. Intermediate assignment is to avoid leaking `this`
+  // to it, while also keeping the stack trace neat when it shows up in there.
+  const callback = timer.callback;
+  callback();
+}
+
+function fireTimers(): void {
+  const now = Date.now();
+  // Bail out if we're not expecting the global timer to fire.
+  if (globalTimeoutDue === null || pendingEvents > 0) {
+    return;
+  }
+  // After firing the timers that are due now, this will hold the first timer
+  // list that hasn't fired yet.
+  let nextDueNode: DueNode | null;
+  while ((nextDueNode = dueTree.min()) !== null && nextDueNode.due <= now) {
+    dueTree.remove(nextDueNode);
+    // Fire all the timers in the list.
+    for (const timer of nextDueNode.timers) {
+      // With the list dropped, the timer is no longer scheduled.
+      timer.scheduled = false;
+      // Place the callback to pending timers to fire.
+      pendingFireTimers.push(timer);
+    }
+  }
+  if (pendingFireTimers.length > 0) {
+    hasPendingFireTimers = true;
+    // Fire the list of pending timers as a chain of microtasks.
+    globalThis.queueMicrotask(firePendingTimers);
+  } else {
+    setOrClearGlobalTimeout(nextDueNode && nextDueNode.due, now);
+  }
+}
+
+function firePendingTimers(): void {
+  if (pendingFireTimers.length === 0) {
+    // All timer tasks are done.
+    hasPendingFireTimers = false;
+    // Schedule all new timers pushed during previous timer executions
+    const now = Date.now();
+    for (const newTimer of pendingScheduleTimers) {
+      newTimer.due = Math.max(newTimer.due, now);
+      schedule(newTimer, now);
+    }
+    pendingScheduleTimers = [];
+    // Reschedule for next round of timeout.
+    const nextDueNode = dueTree.min();
+    const due = nextDueNode && Math.max(nextDueNode.due, now);
+    setOrClearGlobalTimeout(due, now);
+  } else {
+    // Fire a single timer and allow its children microtasks scheduled first.
+    fire(pendingFireTimers.shift()!);
+    // ...and we schedule next timer after this.
+    globalThis.queueMicrotask(firePendingTimers);
+  }
+}
+
+export type Args = unknown[];
+
+function checkThis(thisArg: unknown): void {
+  if (thisArg !== null && thisArg !== undefined && thisArg !== globalThis) {
+    throw new TypeError("Illegal invocation");
+  }
+}
+
+function checkBigInt(n: unknown): void {
+  if (typeof n === "bigint") {
+    throw new TypeError("Cannot convert a BigInt value to a number");
+  }
+}
+
+function setTimer(
+  cb: (...args: Args) => void,
+  delay: number,
+  args: Args,
+  repeat: boolean
+): number {
+  // Bind `args` to the callback and bind `this` to globalThis(global).
+  const callback: () => void = cb.bind(globalThis, ...args);
+  // In the browser, the delay value must be coercible to an integer between 0
+  // and INT32_MAX. Any other value will cause the timer to fire immediately.
+  // We emulate this behavior.
+  const now = Date.now();
+  if (delay > TIMEOUT_MAX) {
+    console.warn(
+      `${delay} does not fit into` +
+        " a 32-bit signed integer." +
+        "\nTimeout duration was set to 1."
+    );
+    delay = 1;
+  }
+  delay = Math.max(0, delay | 0);
+
+  // Create a new, unscheduled timer object.
+  const timer = {
+    id: nextTimerId++,
+    callback,
+    args,
+    delay,
+    due: now + delay,
+    repeat,
+    scheduled: false
+  };
+  // Register the timer's existence in the id-to-timer map.
+  idMap.set(timer.id, timer);
+  // Schedule the timer in the due table.
+  schedule(timer, now);
+  return timer.id;
+}
+
+/** Sets a timer which executes a function once after the timer expires. */
+export function setTimeout(
+  cb: (...args: Args) => void,
+  delay = 0,
+  ...args: Args
+): number {
+  checkBigInt(delay);
+  // @ts-ignore
+  checkThis(this);
+  return setTimer(cb, delay, args, false);
+}
+
+/** Repeatedly calls a function, with a fixed time delay between each call. */
+export function setInterval(
+  cb: (...args: Args) => void,
+  delay = 0,
+  ...args: Args
+): number {
+  checkBigInt(delay);
+  // @ts-ignore
+  checkThis(this);
+  return setTimer(cb, delay, args, true);
+}
+
+/** Clears a previously set timer by id. AKA clearTimeout and clearInterval. */
+function clearTimer(id: number): void {
+  id = Number(id);
+  const timer = idMap.get(id);
+  if (timer === undefined) {
+    // Timer doesn't exist any more or never existed. This is not an error.
+    return;
+  }
+  // Unschedule the timer if it is currently scheduled, and forget about it.
+  unschedule(timer);
+  idMap.delete(timer.id);
+}
+
+export function clearTimeout(id = 0): void {
+  checkBigInt(id);
+  if (id === 0) {
+    return;
+  }
+  clearTimer(id);
+}
+
+export function clearInterval(id = 0): void {
+  checkBigInt(id);
+  if (id === 0) {
+    return;
+  }
+  clearTimer(id);
+}