import logging
from celery import shared_task

logger = logging.getLogger(__name__)


@shared_task(queue="default")
def notify_challenge_expiring(challenge_id: str):
    """
    Send an FCM notification to all participants of a challenge that is
    expiring soon. Scheduled by celery-beat.
    """
    from apps.challenges.models import Challenge, ChallengeParticipant
    from apps.utils.fcm import send_notification

    try:
        challenge = Challenge.objects.get(pk=challenge_id, status=Challenge.Status.ACTIVE)
    except Challenge.DoesNotExist:
        return

    participants = ChallengeParticipant.objects.filter(
        challenge=challenge,
        submitted_splat__isnull=True,  # only those who haven't submitted yet
    ).select_related("user")

    for participant in participants:
        send_notification(
            participant.user.fcm_token,
            title="Challenge expiring soon!",
            body=f'"{challenge.title}" is closing soon. Don\'t miss your chance!',
            data={"challenge_id": str(challenge.id), "type": "challenge_expiring"},
        )

    logger.info("Sent expiry notifications for challenge %s to %d participants", challenge_id, participants.count())