43 lines
1.6 KiB
TypeScript
43 lines
1.6 KiB
TypeScript
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/**
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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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* In-memory BY DESIGN: a process restart clears it, so there are no stale
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* flags to clean up — a crashed turn recovers via the write-ahead record +
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* mount continuation on the next visit. The TTL is a leak guard for the
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* 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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const inFlight = new Map<string, number>(); // chatId → startedAt (epoch ms)
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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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