sync.ts

1	import { ref, onValue } from 'firebase/database';
2	import type { Database } from 'firebase/database';
3	import { decryptJson } from '../../core/crypto';
4
5	type FriendRecord = {
6	id?: string;
7	name?: string;
8	color?: string;
9	position?: { lat: number; lon: number };
10	timestamp?: number;
11	lastSeen?: number;
12	encryptedState?: string;
13	encryptedPosition?: string;
14	[key: string]: unknown;
15	};
16
17	/**
18	* Subscribes to the friends node for a room, decrypting each record
19	* as needed. Calls onUpdate(friends) after every snapshot resolves.
20	*
21	* @param {object} opts
22	* @param {object} opts.db - Firebase Database instance
23	* @param {string} opts.roomId
24	* @param {CryptoKey\|null} opts.roomKey - AES-GCM key, or null for unencrypted rooms
25	* @param {function} opts.onUpdate - (friends: object[]) => void
26	* @returns {{ friends: object[] }} Shared array reference, mutated in place on each update
27	*/
28	export function subscribeToFriends({
29	db,
30	roomId,
31	roomKey,
32	onUpdate
33	}: {
34	db: Database;
35	roomId: string;
36	roomKey: CryptoKey \| null;
37	onUpdate: (friends: FriendRecord[]) => void;
38	}) {
39	const friendsRef = ref(db, `rooms/${roomId}/friends`);
40	const friends: FriendRecord[] = [];
41	let snapshotVersion = 0;
42
43	onValue(friendsRef, async (snapshot) => {
44	const version = ++snapshotVersion;
45
46	const friendsData = snapshot.val();
47	if (friendsData) {
48	const rawFriends = Object.values(friendsData as Record<string, FriendRecord>);
49	const decrypted = await Promise.all(rawFriends.map(async (p): Promise<FriendRecord \| null> => {
50	if (p.encryptedState && roomKey) {
51	try {
52	const decryptedState = await decryptJson(roomKey, p.encryptedState) as Record<string, unknown>;
53	return { ...decryptedState, lastSeen: p.lastSeen };
54	} catch (err) {
55	console.error('Failed to decrypt friend state', p.id, err);
56	return null;
57	}
58	}
59	if (p.encryptedPosition && roomKey) {
60	try {
61	const position = await decryptJson(roomKey, p.encryptedPosition) as { lat: number; lon: number };
62	const { encryptedPosition: _stripped, ...rest } = p;
63	return { ...rest, position };
64	} catch (err) {
65	console.error('Failed to decrypt legacy friend position', p.id, err);
66	return null;
67	}
68	}
69	return p;
70	}));
71	if (version !== snapshotVersion) return;
72	friends.length = 0;
73	friends.push(...decrypted.filter((item): item is FriendRecord => item !== null));
74	} else {
75	if (version !== snapshotVersion) return;
76	friends.length = 0;
77	}
78
79	onUpdate(friends);
80	});
81
82	return { friends };
83	}