From 7c13ea2f2b9aa11859c44f01dfeef29d402b276c Mon Sep 17 00:00:00 2001
From: Sophie Alpert <sophiebits@humu.com>
Date: Wed, 10 Apr 2019 16:31:11 -0700
Subject: [PATCH] Improve bridge batching logic

Fixes #132.
---
 src/bridge.js | 50 +++++++++++++++++++++++++++-----------------------
 1 file changed, 27 insertions(+), 23 deletions(-)

diff --git a/src/bridge.js b/src/bridge.js
index 454c4b9cde..9b3c3dd318 100644
--- a/src/bridge.js
+++ b/src/bridge.js
@@ -13,7 +13,6 @@ type Message = {|
 
 export default class Bridge extends EventEmitter {
   _messageQueue: Array<any> = [];
-  _time: number | null = null;
   _timeoutID: TimeoutID | null = null;
   _wall: Wall;
 
@@ -28,34 +27,39 @@ export default class Bridge extends EventEmitter {
   }
 
   send(event: string, payload: any, transferable?: Array<any>) {
-    const time = this._time;
+    // When we receive a message:
+    // - we add it to our queue of messages to be sent
+    // - if there hasn't been a message recently, we set a timer for 0 ms in
+    //   the future, allowing all messages created in the same tick to be sent
+    //   together
+    // - if there *has* been a message flushed in the last BATCH_DURATION ms
+    //   (or we're waiting for our setTimeout-0 to fire), then _timeoutID will
+    //   be set, and we'll simply add to the queue and wait for that
 
-    if (time === null) {
-      this._wall.send(event, payload, transferable);
-      this._time = Date.now();
-    } else {
-      this._messageQueue.push(event, payload, transferable);
-
-      const now = Date.now();
-      if (now - time > BATCH_DURATION) {
-        this._flush();
-      } else {
-        this._timeoutID = setTimeout(this._flush, BATCH_DURATION);
-      }
+    this._messageQueue.push(event, payload, transferable);
+    if (!this._timeoutID) {
+      this._timeoutID = setTimeout(this._flush, 0);
     }
   }
 
   _flush = () => {
-    while (this._messageQueue.length) {
-      this._wall.send.apply(this._wall, this._messageQueue.splice(0, 3));
-    }
+    clearTimeout(this._timeoutID);
+    this._timeoutID = null;
 
-    if (this._timeoutID !== null) {
-      clearTimeout(this._timeoutID);
-      this._timeoutID = null;
-    }
+    if (this._messageQueue.length) {
+      for (let i = 0; i < this._messageQueue.length; i += 3) {
+        this._wall.send(
+          this._messageQueue[i],
+          this._messageQueue[i + 1],
+          this._messageQueue[i + 2],
+        );
+      }
+      this._messageQueue.length = 0;
 
-    this._messageQueue = [];
-    this._time = null;
+      // Check again for queued messages in BATCH_DURATION ms. This will keep
+      // flushing in a loop as long as messages continue to be added. Once no
+      // more are, the timer expires.
+      this._timeoutID = setTimeout(this._flush, BATCH_DURATION);
+    }
   };
 }