sync.ts

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`a2e2426c` 2026-03-16 Pavel Safronov	1	import { ref, onValue, type Database } from 'firebase/database';
`f32f5e95` 2026-03-16 Pavel Safronov	2	import { decryptJson } from '../../core/crypto';
`a2e2426c` 2026-03-16 Pavel Safronov	3
	4	type ParticipantRecord = {
	5	id?: string;
	6	encryptedState?: string;
	7	encryptedPosition?: string;
	8	[key: string]: unknown;
	9	};
	10
	11	type ParticipantState = Record<string, unknown>;
	12
	13	type SubscribeToParticipantsOptions = {
	14	db: Database;
	15	roomId: string;
	16	roomKey: CryptoKey \| null;
	17	onUpdate: (participants: ParticipantState[]) => void;
	18	};
	19
	20	/**
	21	* Subscribes to the participants node for a room, decrypting each record
	22	* as needed. Calls onUpdate(participants) after every snapshot resolves.
	23	*
	24	* @param {object} opts
	25	* @param {object} opts.db - Firebase Database instance
	26	* @param {string} opts.roomId
	27	* @param {CryptoKey\|null} opts.roomKey - AES-GCM key, or null for unencrypted rooms
	28	* @param {function} opts.onUpdate - (participants: object[]) => void
	29	* @returns {{ participants: object[] }} Shared array reference, mutated in place on each update
	30	*/
	31	export function subscribeToParticipants({ db, roomId, roomKey, onUpdate }: SubscribeToParticipantsOptions): { participants: ParticipantState[] } {
	32	const participantsRef = ref(db, `rooms/${roomId}/participants`);
	33	const participants: ParticipantState[] = [];
	34	let snapshotVersion = 0;
	35
	36	onValue(participantsRef, async (snapshot) => {
	37	const version = ++snapshotVersion;
	38
	39	const participantsData = snapshot.val();
	40	if (participantsData) {
	41	const rawParticipants = Object.values(participantsData as Record<string, ParticipantRecord>);
	42	const decrypted = await Promise.all(rawParticipants.map(async (p) => {
	43	if (p.encryptedState && roomKey) {
	44	try {
	45	return await decryptJson(roomKey, p.encryptedState);
	46	} catch (err) {
	47	console.error('Failed to decrypt participant state', p.id, err);
	48	return null;
	49	}
	50	}
	51	if (p.encryptedPosition && roomKey) {
	52	try {
	53	const position = await decryptJson(roomKey, p.encryptedPosition);
	54	const { encryptedPosition: _stripped, ...rest } = p;
	55	return { ...rest, position };
	56	} catch (err) {
	57	console.error('Failed to decrypt legacy participant position', p.id, err);
	58	return null;
	59	}
	60	}
	61	return p;
	62	}));
	63	if (version !== snapshotVersion) return;
	64	participants.length = 0;
	65	participants.push(...decrypted.filter((value): value is ParticipantState => Boolean(value)));
	66	} else {
	67	if (version !== snapshotVersion) return;
	68	participants.length = 0;
	69	}
	70
	71	onUpdate(participants);
	72	});
	73
	74	return { participants };
	75	}