From 16d581f0ed49be6f3eb2b894ad6c030938e82459 Mon Sep 17 00:00:00 2001
From: Carson Full <carson_full@tsco.org>
Date: Sat, 12 Oct 2024 11:19:53 -0500
Subject: [PATCH] Broadcast cache writes to all tabs/windows

This allows fresh data from one tab to be applied to all tabs.
Each tab still has its own cache, changes are just synced.
So refreshing the page will still initialize empty, so if some data point
became stale (now in all tabs), the user can refresh one page,
and the fresh data will refresh all tabs.
---
 src/api/client/createCache.ts | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/src/api/client/createCache.ts b/src/api/client/createCache.ts
index e9d21a039f..c7a231f0a0 100644
--- a/src/api/client/createCache.ts
+++ b/src/api/client/createCache.ts
@@ -1,4 +1,5 @@
 import { InMemoryCache, PossibleTypesMap, TypePolicies } from '@apollo/client';
+import { Cache } from '@apollo/client/cache';
 import { possibleTypes } from '../schema/fragmentMatcher';
 import { typePolicies } from '../schema/typePolicies';
 
@@ -26,5 +27,16 @@ export const createCache = () => {
     }
   }
 
+  if (typeof BroadcastChannel !== 'undefined') {
+    const writeChannel = new BroadcastChannel('apollo::write');
+    const orig = cache.write.bind(cache);
+    const ourWrite = (options: Cache.WriteOptions, sendToOthers = true) => {
+      sendToOthers && writeChannel.postMessage(options);
+      return orig(options);
+    };
+    writeChannel.onmessage = (event) => ourWrite(event.data, false);
+    cache.write = ourWrite;
+  }
+
   return cache;
 };