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fix(cart): add WebSocket heartbeat pings, exponential reconnect, and eliminate 5s GET polling #31

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fix(cart): add WebSocket heartbeat pings, exponential reconnect, and eliminate 5s GET polling #31

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124 changes: 92 additions & 32 deletions frontend/src/hooks/useCart.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -92,52 +92,112 @@ export function useCart(sessionId: string, recentCartStorageKey?: string) {

useEffect(() => {
let isActive = true;
let interval: ReturnType<typeof setInterval> | null = null;
const initialFetch = window.setTimeout(() => void fetchCart(), 0);
let reconnectTimeout: ReturnType<typeof setTimeout> | null = null;
let pingInterval: ReturnType<typeof setInterval> | null = null;
let reconnectAttempts = 0;

// Initial fetch on session load
void fetchCart();

const wsUrl = createWsUrl(sessionId);
if (!wsUrl) {
interval = setInterval(fetchCart, 5000);
} else {
const ws = new WebSocket(wsUrl);
wsRef.current = ws;

ws.onopen = () => {
if (isActive && sessionIdRef.current === sessionId) setReconnectingSessionId(null);
// If WebSocket is disabled, revalidate on tab focus (no continuous 5s polling spam)
if (!wsUrl) {
const handleFocus = () => {
if (isActive) void fetchCart();
};
window.addEventListener("focus", handleFocus);
return () => {
isActive = false;
window.removeEventListener("focus", handleFocus);
};
}

const connectWebSocket = () => {
if (!isActive || sessionIdRef.current !== sessionId) return;

ws.onmessage = (e) => {
if (!isActive || sessionIdRef.current !== sessionId) return;
try {
const data = JSON.parse(e.data);
if ((data.type === "cart_updated" || data.type === "cart_initialized") && data.cart) {
applyCart(data.cart, undefined, data.type === "cart_updated" ? "Cart updated." : undefined);
try {
const ws = new WebSocket(wsUrl);
wsRef.current = ws;

ws.onopen = () => {
if (!isActive || sessionIdRef.current !== sessionId) return;
reconnectAttempts = 0;
setReconnectingSessionId(null);

// Setup 25-second heartbeat ping to keep socket alive through proxies/routers
if (pingInterval) clearInterval(pingInterval);
pingInterval = setInterval(() => {
if (ws.readyState === WebSocket.OPEN) {
ws.send(JSON.stringify({ type: "ping" }));
}
}, 25000);
};

ws.onmessage = (e) => {
if (!isActive || sessionIdRef.current !== sessionId) return;
try {
const data = JSON.parse(e.data);
if ((data.type === "cart_updated" || data.type === "cart_initialized") && data.cart) {
applyCart(data.cart, undefined, data.type === "cart_updated" ? "Cart updated." : undefined);
}
} catch {
// ignore
}
} catch {
// ignore
}
};
};

const handleDisconnect = () => {
if (pingInterval) clearInterval(pingInterval);
if (!isActive || sessionIdRef.current !== sessionId) return;

setReconnectingSessionId(sessionId);

// Exponential backoff reconnect: 1.5s, 3s, 6s, max 10s
const delay = Math.min(10000, 1500 * Math.pow(1.5, reconnectAttempts));
reconnectAttempts += 1;

ws.onerror = () => {
if (isActive) setReconnectingSessionId(sessionId);
if (!interval) {
interval = setInterval(fetchCart, 5000);
if (reconnectTimeout) clearTimeout(reconnectTimeout);
reconnectTimeout = setTimeout(() => {
if (isActive && sessionIdRef.current === sessionId) {
void fetchCart();
connectWebSocket();
}
}, delay);
};

ws.onerror = handleDisconnect;
ws.onclose = handleDisconnect;
} catch {
if (isActive && sessionIdRef.current === sessionId) {
if (reconnectTimeout) clearTimeout(reconnectTimeout);
reconnectTimeout = setTimeout(connectWebSocket, 3000);
}
};
}
};

connectWebSocket();

ws.onclose = () => {
if (isActive) setReconnectingSessionId(sessionId);
if (!interval) {
interval = setInterval(fetchCart, 5000);
// Re-verify cart state when user tabs back into the window
const handleFocus = () => {
if (isActive && sessionIdRef.current === sessionId) {
if (!wsRef.current || wsRef.current.readyState !== WebSocket.OPEN) {
connectWebSocket();
}
void fetchCart();
}
}
};
window.addEventListener("focus", handleFocus);

return () => {
isActive = false;
window.clearTimeout(initialFetch);
if (interval) clearInterval(interval);
wsRef.current?.close();
if (reconnectTimeout) clearTimeout(reconnectTimeout);
if (pingInterval) clearInterval(pingInterval);
window.removeEventListener("focus", handleFocus);
if (wsRef.current) {
wsRef.current.onclose = null;
wsRef.current.onerror = null;
wsRef.current.close();
}
};
}, [applyCart, sessionId, fetchCart]);

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