fix: add generation guard to refresh, preserve image on transient failure, document env vars

Co-authored-by: Cursor <cursoragent@cursor.com>

README.md

@@ -137,6 +137,8 @@ The database will be automatically initialized and populated with games from `ga
    DB_PATH=./data/jackbox.db
    JWT_SECRET=your-secret-jwt-key
    ADMIN_KEY=admin123
+   VOTE_APP_URL=https://vote-app.example.com
+   VOTE_APP_API_KEY=your-vote-app-api-key
    ```
 
 4. **Start the backend server**
@@ -184,6 +186,13 @@ If `admins.json` is not found, the app falls back to the `ADMIN_KEY` environment
 
 To use a custom path for the admins file, set `ADMIN_CONFIG_PATH` in your environment.
 
+### Sticker Wall Preview
+
+The backend proxies sticker wall images from the vote-app. Set these in `backend/.env`:
+
+- `VOTE_APP_URL` — base URL of the vote-app (e.g. `https://vote-app.example.com`)
+- `VOTE_APP_API_KEY` — API key for the sticker wall render endpoint
+
 For Docker, uncomment the volume mount in `docker-compose.yml`:
 ```yaml
 - ./backend/config/admins.json:/app/config/admins.json:ro

frontend/src/hooks/useStickerWall.js

@@ -6,6 +6,7 @@ export function useStickerWall(sessionId) {
   const [loading, setLoading] = useState(false);
   const [error, setError] = useState(false);
   const urlRef = useRef(null);
+  const generationRef = useRef(0);
 
   const revokeUrl = useCallback(() => {
     if (urlRef.current) {
@@ -23,20 +24,28 @@ export function useStickerWall(sessionId) {
 
   const refresh = useCallback(async () => {
     if (!sessionId) return;
+    const generation = generationRef.current;
     setLoading(true);
     setError(false);
     try {
       const res = await api.post(`/stickerwalls/${sessionId}/render`, null, { responseType: 'blob' });
+      if (generation !== generationRef.current) return;
       setBlobUrl(res.data);
     } catch {
-      setError(true);
+      if (generation !== generationRef.current) return;
+      if (!urlRef.current) {
+        setError(true);
+      }
     } finally {
-      setLoading(false);
+      if (generation === generationRef.current) {
+        setLoading(false);
+      }
     }
   }, [sessionId, setBlobUrl]);
 
   useEffect(() => {
-    let stale = false;
+    generationRef.current += 1;
+    const generation = generationRef.current;
 
     if (!sessionId) {
       revokeUrl();
@@ -50,17 +59,17 @@ export function useStickerWall(sessionId) {
       setError(false);
       try {
         const res = await api.get(`/stickerwalls/${id}`, { responseType: 'blob' });
-        if (stale) return;
+        if (generation !== generationRef.current) return;
         setBlobUrl(res.data);
       } catch (err) {
-        if (stale) return;
+        if (generation !== generationRef.current) return;
         if (err.response?.status === 404) {
           try {
             const renderRes = await api.post(`/stickerwalls/${id}/render`, null, { responseType: 'blob' });
-            if (stale) return;
+            if (generation !== generationRef.current) return;
             setBlobUrl(renderRes.data);
           } catch {
-            if (stale) return;
+            if (generation !== generationRef.current) return;
             revokeUrl();
             setImageUrl(null);
             setError(true);
@@ -71,7 +80,7 @@ export function useStickerWall(sessionId) {
           setError(true);
         }
       } finally {
-        if (!stale) {
+        if (generation === generationRef.current) {
           setLoading(false);
         }
       }
@@ -80,7 +89,6 @@ export function useStickerWall(sessionId) {
     fetchWall(sessionId);
 
     return () => {
-      stale = true;
       revokeUrl();
     };
   }, [sessionId, setBlobUrl, revokeUrl]);