1 files changed, 208 insertions, 0 deletions
diff --git a/remote/Sync.jsm b/remote/Sync.jsm
new file mode 100644
index 0000000000..e7f1057914
--- /dev/null
+++ b/remote/Sync.jsm
@@ -0,0 +1,208 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+var EXPORTED_SYMBOLS = ["EventPromise", "executeSoon", "PollPromise"];
+
+const { Services } = ChromeUtils.import("resource://gre/modules/Services.jsm");
+
+const { TYPE_REPEATING_SLACK } = Ci.nsITimer;
+
+/**
+ * Wait for a single event to be fired on a specific EventListener.
+ *
+ * The returned promise is guaranteed to not be called before the
+ * next event tick after the event listener is called, so that all
+ * other event listeners for the element are executed before the
+ * handler is executed.  For example:
+ *
+ *     const promise = new EventPromise(element, "myEvent");
+ *     // same event tick here
+ *     await promise;
+ *     // next event tick here
+ *
+ * @param {EventListener} listener
+ *     Object which receives a notification (an object that implements
+ *     the Event interface) when an event of the specificed type occurs.
+ * @param {string} type
+ *     Case-sensitive string representing the event type to listen for.
+ * @param {boolean?} [false] options.capture
+ *     Indicates the event will be despatched to this subject,
+ *     before it bubbles down to any EventTarget beneath it in the
+ *     DOM tree.
+ * @param {boolean?} [false] options.wantsUntrusted
+ *     Receive synthetic events despatched by web content.
+ * @param {boolean?} [false] options.mozSystemGroup
+ *     Determines whether to add listener to the system group.
+ *
+ * @return {Promise.<Event>}
+ *
+ * @throws {TypeError}
+ */
+function EventPromise(
+  listener,
+  type,
+  options = {
+    capture: false,
+    wantsUntrusted: false,
+    mozSystemGroup: false,
+  }
+) {
+  if (!listener || !("addEventListener" in listener)) {
+    throw new TypeError();
+  }
+  if (typeof type != "string") {
+    throw new TypeError();
+  }
+  if (
+    ("capture" in options && typeof options.capture != "boolean") ||
+    ("wantsUntrusted" in options &&
+      typeof options.wantsUntrusted != "boolean") ||
+    ("mozSystemGroup" in options && typeof options.mozSystemGroup != "boolean")
+  ) {
+    throw new TypeError();
+  }
+
+  options.once = true;
+
+  return new Promise(resolve => {
+    listener.addEventListener(
+      type,
+      event => {
+        executeSoon(() => resolve(event));
+      },
+      options
+    );
+  });
+}
+
+/**
+ * Wait for the next tick in the event loop to execute a callback.
+ *
+ * @param {function} fn
+ *     Function to be executed.
+ */
+function executeSoon(fn) {
+  if (typeof fn != "function") {
+    throw new TypeError();
+  }
+
+  Services.tm.dispatchToMainThread(fn);
+}
+
+/**
+ * Runs a Promise-like function off the main thread until it is resolved
+ * through ``resolve`` or ``rejected`` callbacks.  The function is
+ * guaranteed to be run at least once, irregardless of the timeout.
+ *
+ * The ``func`` is evaluated every ``interval`` for as long as its
+ * runtime duration does not exceed ``interval``.  Evaluations occur
+ * sequentially, meaning that evaluations of ``func`` are queued if
+ * the runtime evaluation duration of ``func`` is greater than ``interval``.
+ *
+ * ``func`` is given two arguments, ``resolve`` and ``reject``,
+ * of which one must be called for the evaluation to complete.
+ * Calling ``resolve`` with an argument indicates that the expected
+ * wait condition was met and will return the passed value to the
+ * caller.  Conversely, calling ``reject`` will evaluate ``func``
+ * again until the ``timeout`` duration has elapsed or ``func`` throws.
+ * The passed value to ``reject`` will also be returned to the caller
+ * once the wait has expired.
+ *
+ * Usage::
+ *
+ *     let els = new PollPromise((resolve, reject) => {
+ *       let res = document.querySelectorAll("p");
+ *       if (res.length > 0) {
+ *         resolve(Array.from(res));
+ *       } else {
+ *         reject([]);
+ *       }
+ *     }, {timeout: 1000});
+ *
+ * @param {Condition} func
+ *     Function to run off the main thread.
+ * @param {number=} [timeout] timeout
+ *     Desired timeout if wanted.  If 0 or less than the runtime evaluation
+ *     time of ``func``, ``func`` is guaranteed to run at least once.
+ *     Defaults to using no timeout.
+ * @param {number=} [interval=10] interval
+ *     Duration between each poll of ``func`` in milliseconds.
+ *     Defaults to 10 milliseconds.
+ *
+ * @return {Promise.<*>}
+ *     Yields the value passed to ``func``'s
+ *     ``resolve`` or ``reject`` callbacks.
+ *
+ * @throws {*}
+ *     If ``func`` throws, its error is propagated.
+ * @throws {TypeError}
+ *     If `timeout` or `interval`` are not numbers.
+ * @throws {RangeError}
+ *     If `timeout` or `interval` are not unsigned integers.
+ */
+function PollPromise(func, { timeout = null, interval = 10 } = {}) {
+  const timer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
+
+  if (typeof func != "function") {
+    throw new TypeError();
+  }
+  if (timeout != null && typeof timeout != "number") {
+    throw new TypeError();
+  }
+  if (typeof interval != "number") {
+    throw new TypeError();
+  }
+  if (
+    (timeout && (!Number.isInteger(timeout) || timeout < 0)) ||
+    !Number.isInteger(interval) ||
+    interval < 0
+  ) {
+    throw new RangeError();
+  }
+
+  return new Promise((resolve, reject) => {
+    let start, end;
+
+    if (Number.isInteger(timeout)) {
+      start = new Date().getTime();
+      end = start + timeout;
+    }
+
+    let evalFn = () => {
+      new Promise(func)
+        .then(resolve, rejected => {
+          if (typeof rejected != "undefined") {
+            throw rejected;
+          }
+
+          // return if there is a timeout and set to 0,
+          // allowing |func| to be evaluated at least once
+          if (
+            typeof end != "undefined" &&
+            (start == end || new Date().getTime() >= end)
+          ) {
+            resolve(rejected);
+          }
+        })
+        .catch(reject);
+    };
+
+    // the repeating slack timer waits |interval|
+    // before invoking |evalFn|
+    evalFn();
+
+    timer.init(evalFn, interval, TYPE_REPEATING_SLACK);
+  }).then(
+    res => {
+      timer.cancel();
+      return res;
+    },
+    err => {
+      timer.cancel();
+      throw err;
+    }
+  );
+}