Amos
7ab444ead3
In Next dev (Turbopack), each route compiles as its own entry — a module-level Map in turn-liveness.ts was a DIFFERENT instance in the page render, GET /api/chats/[id], and POST /api/chat. The chat route held the live turn (hence the 409), but the page render read an empty registry: initiallyInFlight=false → mount continuation fired a send → 409 → the 'Something went wrong' banner on returning mid-turn. The registry now lives on globalThis (the standard Next singleton channel) — one Map per process regardless of module instances. Semantics unchanged (TTL leak guard, begin/end round trip). Browser-verified end-to-end (headless tester): answer quiz → navigate away → return mid-turn → graded card (no re-prompt), 'Thinking…' shimmer, composer gated, no error banner; teacher response auto-delivered when the background turn finished. Polling GET /api/chats/[id] observed working.
60 lines
2.3 KiB
TypeScript
60 lines
2.3 KiB
TypeScript
/**
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* Server-side turn liveness: which chats currently have a teacher turn in
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* flight. The missing half of "sessions keep running in the background" —
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* together with the write-ahead persist in chat-handler, a returning client
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* can tell "the teacher is mid-turn — don't resurrect, don't start anything"
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* apart from "the record IS current".
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*
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* Lives on globalThis, NOT a module-level Map: Next dev compiles each route
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* as its own entry, so a module-level singleton is a DIFFERENT instance in
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* the page render, GET /api/chats/[id], and POST /api/chat — the page would
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* read an empty registry while the chat route holds the live turn (the bug:
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* returning mid-turn showed the 409 banner instead of the busy state).
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* globalThis spans module instances within the process; it is the standard
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* Next.js singleton channel (same reason Prisma clients live there).
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*
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* Still ephemeral BY DESIGN: a process restart clears it, so there are no
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* stale flags to clean up — a crashed turn recovers via the write-ahead
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* record + mount continuation on the next visit. The TTL is a leak guard for
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* the pathological case where onFinish never fires (it runs even on aborts);
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* chat turns are minutes at most, so 30 minutes is far on the safe side.
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*/
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interface LhGlobal {
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__lhTurnRegistry?: Map<string, number>;
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}
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function registry(): Map<string, number> {
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const g = globalThis as typeof globalThis & LhGlobal;
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return (g.__lhTurnRegistry ??= new Map<string, number>());
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}
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const inFlight = registry();
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const MAX_TURN_MS = 30 * 60_000;
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/**
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* Mark a turn as starting. Returns false if one is already running for the
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* chat — the caller rejects the request (only one turn may own a chat).
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*/
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export function beginTurn(chatId: string): boolean {
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if (isTurnRunning(chatId)) return false;
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inFlight.set(chatId, Date.now());
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return true;
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}
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/** Mark the chat's turn as finished (runs in onFinish, aborted or not). */
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export function endTurn(chatId: string): void {
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inFlight.delete(chatId);
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}
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/** True while the chat's turn is in flight; lazily evicts stale entries. */
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export function isTurnRunning(chatId: string): boolean {
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const since = inFlight.get(chatId);
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if (since === undefined) return false;
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if (Date.now() - since > MAX_TURN_MS) {
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inFlight.delete(chatId);
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return false;
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}
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return true;
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}
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