/**
 * Build the cross-process realtime bus from config. When realtime scaling is
 * enabled, room broadcasts are bridged over Redis pub/sub so they reach clients
 * on every app process/instance (multiple runs, or multiple apps behind the
 * gateway). Returns undefined when scaling is off (single-process realtime).
 */

import type { RealtimeBus } from "@wrnexus/core";
import { createPubSub } from "@wrnexus/pubsub";
import { redisDriver } from "@wrnexus/pubsub/redis";

export function realtimeBusFromConfig(cfg?: {
  scale?: boolean;
  redisUrl?: string;
}): RealtimeBus | undefined {
  if (!cfg?.scale && !cfg?.redisUrl) return undefined;
  return createPubSub(redisDriver(cfg.redisUrl));
}