src/redis/presenceClient.ts

import Redis from 'ioredis';
import { CONFIG } from '../config';
import { logger } from '../utils/logger';

/**
 * Redis Bucket 1 — Presence
 *
 * Key schema:
 *   presence:uid:{uid}   → socket_id  (TTL = PRESENCE_TTL_S)
 *   status:uid:{uid}     → "online"   (TTL = PRESENCE_TTL_S)
 *
 * Separate client instance so Bucket 1 errors never affect Bucket 2.
 */
const presenceClient = new Redis(CONFIG.REDIS_PRESENCE_URL, {
  maxRetriesPerRequest: 2,
  connectTimeout: 5000,
  lazyConnect: false,
  enableReadyCheck: true,
  // Keep-alive so the HF container connection stays warm
  keepAlive: 10000,
});

presenceClient.on('connect', () => logger.info('Presence Redis connected'));
presenceClient.on('error', (err: Error) =>
  logger.error('Presence Redis error', { error: err.message })
);
presenceClient.on('reconnecting', () => logger.warn('Presence Redis reconnecting'));

export { presenceClient };

// ── Key builders ─────────────────────────────────────────────────────────────

const presenceKey = (uid: string) => `presence:uid:${uid}`;
const statusKey = (uid: string) => `status:uid:${uid}`;

// ── Operations ───────────────────────────────────────────────────────────────

/** Map uid → socketId, mark user online. Called on WS connect. */
export async function setOnline(uid: string, socketId: string): Promise<void> {
  const ttl = CONFIG.PRESENCE_TTL_S;
  // MULTI/EXEC keeps it atomic
  await presenceClient
    .multi()
    .set(presenceKey(uid), socketId, 'EX', ttl)
    .set(statusKey(uid), 'online', 'EX', ttl)
    .exec();
}

/** Refresh TTL on heartbeat. Does not overwrite the socket id. */
export async function refreshPresence(uid: string): Promise<void> {
  const ttl = CONFIG.PRESENCE_TTL_S;
  await presenceClient
    .multi()
    .expire(presenceKey(uid), ttl)
    .expire(statusKey(uid), ttl)
    .exec();
}

/** Remove user from presence. Called on WS close. */
export async function setOffline(uid: string): Promise<void> {
  await presenceClient
    .multi()
    .del(presenceKey(uid))
    .del(statusKey(uid))
    .exec();
}

/** Returns the socket id for a uid, or null if offline. */
export async function getSocketId(uid: string): Promise<string | null> {
  return presenceClient.get(presenceKey(uid));
}

/** Returns true if the user is online. */
export async function isOnline(uid: string): Promise<boolean> {
  const status = await presenceClient.get(statusKey(uid));
  return status === 'online';
}