From 5b9675b0747497bbf648e34e672ac51944f66851 Mon Sep 17 00:00:00 2001
From: Alexander Zinchuk <alx.zinchuk@gmail.com>
Date: Sun, 8 Sep 2024 19:58:32 +0200
Subject: [PATCH] Multitab: Fix global diff sync

---
 src/util/multitab.ts | 36 ++++++++++++++++++++----------------
 1 file changed, 20 insertions(+), 16 deletions(-)

diff --git a/src/util/multitab.ts b/src/util/multitab.ts
index b4cb4d648..1c88b0ff2 100644
--- a/src/util/multitab.ts
+++ b/src/util/multitab.ts
@@ -113,24 +113,26 @@ type BroadcastChannelMessage = (
 
 let resolveGlobalPromise: VoidFunction | undefined;
 let isFirstGlobalResolved = false;
-let prevGlobal: GlobalState | undefined;
+let currentGlobal: GlobalState | undefined;
 let isDisabled = false;
 
 const channel = IS_MULTITAB_SUPPORTED
   ? new BroadcastChannel(DATA_BROADCAST_CHANNEL_NAME) as TypedBroadcastChannel
   : undefined;
 
-let globalToDiffWith: GlobalState | undefined;
+let isBroadcastDiffScheduled = false;
+let lastBroadcastDiffGlobal: GlobalState | undefined;
 
-function broadcastDiffOnIdle(_globalToDiffWith: GlobalState) {
-  globalToDiffWith = _globalToDiffWith;
+function broadcastDiffOnIdle() {
+  if (isBroadcastDiffScheduled) return;
+
+  isBroadcastDiffScheduled = true;
+  lastBroadcastDiffGlobal = currentGlobal;
 
   onFullyIdle(() => {
-    if (!channel || !globalToDiffWith) return;
+    if (!channel) return;
 
-    const diff = deepDiff(globalToDiffWith, prevGlobal);
-
-    globalToDiffWith = undefined;
+    const diff = deepDiff(lastBroadcastDiffGlobal, currentGlobal);
 
     if (typeof diff !== 'symbol') {
       channel.postMessage({
@@ -138,6 +140,8 @@ function broadcastDiffOnIdle(_globalToDiffWith: GlobalState) {
         diff,
       });
     }
+
+    isBroadcastDiffScheduled = false;
   });
 }
 
@@ -181,16 +185,16 @@ export function subscribeToMultitabBroadcastChannel() {
 
   addCallback((global: GlobalState) => {
     if (!isFirstGlobalResolved || isDisabled) {
-      prevGlobal = global;
+      currentGlobal = global;
       return;
     }
 
-    if (prevGlobal === global) {
+    if (currentGlobal === global) {
       return;
     }
 
-    if (!prevGlobal) {
-      prevGlobal = global;
+    if (!currentGlobal) {
+      currentGlobal = global;
       channel.postMessage({
         type: 'globalUpdate',
         global,
@@ -198,9 +202,9 @@ export function subscribeToMultitabBroadcastChannel() {
       return;
     }
 
-    broadcastDiffOnIdle(prevGlobal);
+    broadcastDiffOnIdle();
 
-    prevGlobal = global;
+    currentGlobal = global;
   });
 
   channel.addEventListener('message', handleMessage);
@@ -228,7 +232,7 @@ export function handleMessage({ data }: { data: BroadcastChannelMessage }) {
       // @ts-ignore
       global.DEBUG_capturedId = oldGlobal.DEBUG_capturedId;
 
-      prevGlobal = global;
+      currentGlobal = global;
       setGlobal(global);
       break;
     }
@@ -238,7 +242,7 @@ export function handleMessage({ data }: { data: BroadcastChannelMessage }) {
       const oldGlobal = getGlobal();
       // @ts-ignore
       data.global.DEBUG_capturedId = oldGlobal.DEBUG_capturedId;
-      prevGlobal = data.global;
+      currentGlobal = data.global;
       setGlobal(data.global);
       if (resolveGlobalPromise) {
         resolveGlobalPromise();