From 515174fe2134d7bbe9992a1bb7be4a9e4ef1bdbf Mon Sep 17 00:00:00 2001
From: Brian Broll <brian.broll@gmail.com>
Date: Thu, 1 Oct 2020 10:34:59 -0500
Subject: [PATCH] Add PromiseEvents. Closes #1939

---
 src/common/EventEmitter.js                |  4 +++
 src/common/PromiseEvents.js               | 33 +++++++++++++++++++++++
 src/common/compute/interactive/session.js | 29 +++-----------------
 src/common/utils.js                       |  5 ++++
 test/unit/common/PromiseEvents.spec.js    | 26 ++++++++++++++++++
 5 files changed, 72 insertions(+), 25 deletions(-)
 create mode 100644 src/common/PromiseEvents.js
 create mode 100644 test/unit/common/PromiseEvents.spec.js

diff --git a/src/common/EventEmitter.js b/src/common/EventEmitter.js
index 29d48460e..f2ff1b698 100644
--- a/src/common/EventEmitter.js
+++ b/src/common/EventEmitter.js
@@ -4,6 +4,10 @@ define([
 ) {
     class EventEmitter {
         constructor() {
+            this.init();
+        }
+
+        init() {
             this._handlers = {};
         }
 
diff --git a/src/common/PromiseEvents.js b/src/common/PromiseEvents.js
new file mode 100644
index 000000000..90c7ba611
--- /dev/null
+++ b/src/common/PromiseEvents.js
@@ -0,0 +1,33 @@
+/*globals define*/
+define([
+    'deepforge/EventEmitter',
+    'deepforge/utils',
+], function(
+    EventEmitter,
+    utils,
+) {
+    class PromiseEvents extends Promise {
+        constructor(fn) {
+            super(fn);
+            this.init();
+        }
+
+        static new(fn) {
+            let promise;
+            promise = new PromiseEvents(async function(resolve, reject) {
+                await utils.yield();
+                return fn.call(promise, resolve, reject);
+            });
+            return promise;
+        }
+    }
+
+    const methods = Object.getOwnPropertyNames(EventEmitter.prototype)
+        .filter(fn => !PromiseEvents.prototype[fn]);
+
+    methods.forEach(fn => {
+        PromiseEvents.prototype[fn] = EventEmitter.prototype[fn];
+    });
+
+    return PromiseEvents;
+});
diff --git a/src/common/compute/interactive/session.js b/src/common/compute/interactive/session.js
index 1f8580efc..d1042c98e 100644
--- a/src/common/compute/interactive/session.js
+++ b/src/common/compute/interactive/session.js
@@ -1,12 +1,14 @@
 /* globals define */
 define([
     'deepforge/utils',
+    'deepforge/PromiseEvents',
     'deepforge/compute/interactive/task',
     'deepforge/compute/interactive/message',
     'deepforge/compute/interactive/errors',
     'deepforge/gmeConfig',
 ], function(
     utils,
+    PromiseEvents,
     Task,
     Message,
     Errors,
@@ -167,8 +169,7 @@ define([
             const address = gmeConfig.extensions.InteractiveComputeHost ||
                 getDefaultServerURL();
 
-            let createSession;
-            createSession = new PromiseEvents(function(resolve, reject) {
+            return PromiseEvents.new(function(resolve, reject) {
                 const ws = new WebSocket(address);
                 ws.onopen = () => {
                     ws.send(JSON.stringify([computeID, config, getGMEToken()]));
@@ -189,33 +190,11 @@ define([
                             const err = msg.data;
                             reject(err);
                         } else if (msg.type === Message.STATUS) {
-                            createSession.emit('update', msg.data);
+                            this.emit('update', msg.data);
                         }
                     };
                 };
             });
-
-            return createSession;
-        }
-    }
-
-    class PromiseEvents extends Promise {
-        constructor(fn) {
-            super(fn);
-            this._handlers = {};
-        }
-
-        on(event, fn) {
-            if (!this._handlers[event]) {
-                this._handlers[event] = [];
-            }
-            this._handlers[event].push(fn);
-        }
-
-        emit(event) {
-            const handlers = this._handlers[event] || [];
-            const args = Array.prototype.slice.call(arguments, 1);
-            handlers.forEach(fn => fn.apply(null, args));
         }
     }
 
diff --git a/src/common/utils.js b/src/common/utils.js
index 47f4f31a5..87c5eec1e 100644
--- a/src/common/utils.js
+++ b/src/common/utils.js
@@ -141,6 +141,10 @@
         return deferred.promise;
     }
 
+    function yield() {
+        return sleep(0);
+    }
+
     async function waitUntil(fn, interval=50) {
         while (!await fn()) {
             await sleep(interval);
@@ -167,6 +171,7 @@
         withTimeout,
         defer,
         sleep,
+        yield,
         waitUntil,
         partition,
     };
diff --git a/test/unit/common/PromiseEvents.spec.js b/test/unit/common/PromiseEvents.spec.js
new file mode 100644
index 000000000..4b8a6bada
--- /dev/null
+++ b/test/unit/common/PromiseEvents.spec.js
@@ -0,0 +1,26 @@
+describe('PromiseEvents', function() {
+    const assert = require('assert');
+    const testFixture = require('../../globals');
+    const PromiseEvents = testFixture.requirejs('deepforge/PromiseEvents');
+
+    it('should resolve as a promise', async function() {
+        const five = await PromiseEvents.new(
+            resolve => setTimeout(() => resolve(5), 5)
+        );
+        assert.equal(five, 5);
+    });
+
+    it('should support updates', async function() {
+        const promise = PromiseEvents.new(function(resolve) {
+            for (let i = 1; i < 6; i++) {
+                this.emit('update', i);
+            }
+            resolve(6);
+        });
+        const events = [];
+        promise.on('update', status => events.push(status));
+        const six = await promise;
+        assert.equal(events.length, 5);
+        assert.equal(six, 6);
+    });
+});