import {
  cancelScheduledDisconnectRoomChat,
  scheduleDisconnectRoomChat,
} from '@/lib/chzzk/chat-session';
import {
  addRoomViewer,
  getRoom,
  removeRoomViewer,
  subscribeRoom,
  toPublicRoom,
  type PublicRoomState,
} from '@/lib/rooms/store';

export const runtime = 'nodejs';
export const dynamic = 'force-dynamic';

type Params = { params: Promise<{ roomId: string }> };

export async function GET(request: Request, { params }: Params) {
  const { roomId } = await params;
  const room = getRoom(roomId);
  if (!room) {
    return new Response(JSON.stringify({ error: '방을 찾을 수 없습니다.' }), {
      status: 404,
      headers: { 'Content-Type': 'application/json' },
    });
  }

  const clientId =
    new URL(request.url).searchParams.get('clientId')?.trim() ||
    crypto.randomUUID();

  const encoder = new TextEncoder();
  let unsubscribe: (() => void) | null = null;
  let heartbeat: ReturnType<typeof setInterval> | null = null;
  let presenceHeld = false;

  const release = () => {
    if (!presenceHeld) return;
    presenceHeld = false;
    const { emptied } = removeRoomViewer(roomId, clientId);
    if (emptied) {
      // 즉시 끊지 않음 — 빠른 재입장과 경쟁하지 않도록 유예
      scheduleDisconnectRoomChat(roomId);
    }
  };

  const stream = new ReadableStream({
    start(controller) {
      // 재입장 시 예약된 disconnect 취소
      cancelScheduledDisconnectRoomChat(roomId);
      addRoomViewer(roomId, clientId);
      presenceHeld = true;

      const send = (event: string, data: unknown) => {
        controller.enqueue(
          encoder.encode(`event: ${event}\ndata: ${JSON.stringify(data)}\n\n`),
        );
      };

      send('room', toPublicRoom(room));
      unsubscribe = subscribeRoom(roomId, (state: PublicRoomState) => {
        send('room', state);
      });
      heartbeat = setInterval(() => {
        controller.enqueue(encoder.encode(`: ping\n\n`));
      }, 15000);
    },
    cancel() {
      if (unsubscribe) unsubscribe();
      if (heartbeat) clearInterval(heartbeat);
      release();
    },
  });

  return new Response(stream, {
    headers: {
      'Content-Type': 'text/event-stream; charset=utf-8',
      'Cache-Control': 'no-cache, no-transform',
      Connection: 'keep-alive',
    },
  });
}