From f958230a664425e812348719e02b2b1a55f44ec9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Carl-Gerhard=20Lindesva=CC=88rd?= <lindesvard@gmail.com>
Date: Mon, 20 Oct 2025 10:29:38 +0200
Subject: [PATCH] fix: improve cookie store

---
 apps/start/src/components/theme-provider.tsx | 18 +++-------
 apps/start/src/hooks/use-cookie-store.tsx    | 37 +++++++++++++++++---
 2 files changed, 36 insertions(+), 19 deletions(-)

diff --git a/apps/start/src/components/theme-provider.tsx b/apps/start/src/components/theme-provider.tsx
index 1a4b2388..792b57f8 100644
--- a/apps/start/src/components/theme-provider.tsx
+++ b/apps/start/src/components/theme-provider.tsx
@@ -18,18 +18,6 @@ export type AppTheme = z.infer<typeof AppThemeSchema>;
 
 const themeStorageKey = 'ui-theme';
 
-const getStoredUserTheme = createIsomorphicFn()
-  .server((): UserTheme => 'system')
-  .client((): UserTheme => {
-    const stored = localStorage.getItem(themeStorageKey);
-    return UserThemeSchema.parse(stored);
-  });
-
-const setStoredTheme = clientOnly((theme: UserTheme) => {
-  const validatedTheme = UserThemeSchema.parse(theme);
-  localStorage.setItem(themeStorageKey, validatedTheme);
-});
-
 const getSystemTheme = createIsomorphicFn()
   .server((): AppTheme => 'light')
   .client((): AppTheme => {
@@ -73,7 +61,10 @@ const themes = mapKeys(themeConfig).map((key) => ({
 const themeScript = (() => {
   function themeFn() {
     try {
-      const storedTheme = localStorage.getItem('ui-theme') || 'system';
+      // Read theme from cookie
+      const cookies = document.cookie.split('; ');
+      const themeCookie = cookies.find((c) => c.startsWith('ui-theme='));
+      const storedTheme = themeCookie ? themeCookie.split('=')[1] : 'system';
       const validTheme = ['light', 'dark', 'system'].includes(storedTheme)
         ? storedTheme
         : 'system';
@@ -131,7 +122,6 @@ export function ThemeProvider({ children }: ThemeProviderProps) {
   const setTheme = (newUserTheme: UserTheme) => {
     const validatedTheme = UserThemeSchema.parse(newUserTheme);
     setUserTheme(validatedTheme);
-    setStoredTheme(validatedTheme);
     handleThemeChange(validatedTheme);
   };
 
diff --git a/apps/start/src/hooks/use-cookie-store.tsx b/apps/start/src/hooks/use-cookie-store.tsx
index 360bc3a8..ec775a1b 100644
--- a/apps/start/src/hooks/use-cookie-store.tsx
+++ b/apps/start/src/hooks/use-cookie-store.tsx
@@ -2,10 +2,11 @@ import { useRouteContext } from '@tanstack/react-router';
 import { createServerFn, createServerOnlyFn } from '@tanstack/react-start';
 import { getCookies, setCookie } from '@tanstack/react-start/server';
 import { pick } from 'ramda';
-import { useMemo, useState } from 'react';
+import { useEffect, useMemo, useRef, useState } from 'react';
 import { z } from 'zod';
 
 const VALID_COOKIES = ['ui-theme', 'chartType', 'range'] as const;
+const COOKIE_EVENT_NAME = '__cookie-change';
 
 const setCookieFn = createServerFn({ method: 'POST' })
   .inputValidator(z.object({ key: z.enum(VALID_COOKIES), value: z.string() }))
@@ -25,15 +26,41 @@ export function useCookieStore<T>(
 ) {
   const { cookies } = useRouteContext({ strict: false });
   const [value, setValue] = useState<T>((cookies?.[key] ?? defaultValue) as T);
+  const ref = useRef(Math.random().toString(36).substring(7));
+
+  useEffect(() => {
+    const handleCookieChange = (
+      event: CustomEvent<{ key: string; value: T; from: string }>,
+    ) => {
+      if (event.detail.key === key && event.detail.from !== ref.current) {
+        setValue(event.detail.value);
+      }
+    };
+
+    window.addEventListener(
+      COOKIE_EVENT_NAME,
+      handleCookieChange as EventListener,
+    );
+    return () => {
+      window.removeEventListener(
+        COOKIE_EVENT_NAME,
+        handleCookieChange as EventListener,
+      );
+    };
+  }, [key]);
 
   return useMemo(
     () =>
       [
         value,
-        (value: T) => {
-          console.log('setting cookie', key, value);
-          setValue(value);
-          setCookieFn({ data: { key, value: String(value) } });
+        (newValue: T) => {
+          setValue(newValue);
+          setCookieFn({ data: { key, value: String(newValue) } });
+          window.dispatchEvent(
+            new CustomEvent(COOKIE_EVENT_NAME, {
+              detail: { key, value: newValue, from: ref.current },
+            }),
+          );
         },
       ] as const,
     [value, key],