/**
 * Chat Status Pub/Sub Adapter
 *
 * Broadcasts chat status events across processes using Redis Pub/Sub.
 * Gracefully falls back to process-local EventEmitter when Redis is unavailable.
 *
 * The Redis channel and SSE label retain the legacy `task:status_changed`
 * identifier so live status updates keep flowing across pods during a rolling
 * deploy (old and new pods must publish/subscribe on the same channel).
 */

import { createPubSubChannel, type PubSubChannel } from '@/lib/events/pubsub'

interface ChatStatusEvent {
  workspaceId: string
  chatId: string
  type: 'started' | 'completed' | 'created' | 'deleted' | 'renamed'
  streamId?: string
}

type ChatPubSubGlobal = typeof globalThis & {
  _chatStatusChannel?: PubSubChannel<ChatStatusEvent> | null
}

const g = globalThis as ChatPubSubGlobal

if (!('_chatStatusChannel' in g)) {
  g._chatStatusChannel =
    typeof window !== 'undefined'
      ? null
      : createPubSubChannel<ChatStatusEvent>({ channel: 'task:status_changed', label: 'task' })
}

const channel = g._chatStatusChannel

export const chatPubSub = channel
  ? {
      publishStatusChanged: (event: ChatStatusEvent) => channel.publish(event),
      onStatusChanged: (handler: (event: ChatStatusEvent) => void) => channel.subscribe(handler),
      dispose: () => channel.dispose(),
    }
  : null