"""Celery Beat periodic tasks."""
from __future__ import annotations

import json
import logging

from celery import shared_task

logger = logging.getLogger(__name__)


@shared_task(name="app.tasks.beat_tasks.broadcast_queue_status", queue="step_processing")
def broadcast_queue_status() -> None:
    """Broadcast current queue depths to all WebSocket clients every 10s.

    Publishes to the Redis '__broadcast__' channel which the WebSocket
    subscriber in the FastAPI process forwards to all connected clients.
    """
    try:
        import redis as sync_redis
        from app.config import settings

        r = sync_redis.from_url(settings.redis_url, decode_responses=True)
        depths = {
            "step_processing": r.llen("step_processing"),
            "thumbnail_rendering": r.llen("thumbnail_rendering"),
        }
        event = {"type": "queue_update", "depths": depths}
        r.publish("__broadcast__", json.dumps(event))
        r.close()
        logger.debug("Broadcast queue_update: %s", depths)
    except Exception as exc:
        logger.warning("broadcast_queue_status failed: %s", exc)