import logging

from celery import shared_task

logger = logging.getLogger(__name__)


def _bind_dispatch_tenant(tenant_id, dispatch):
    from infrasynth.tenancy.context import tenant_context
    from infrasynth.tenancy.models import Tenant

    if tenant_id:
        tenant = Tenant.objects.filter(pk=tenant_id).first()
    else:
        tenant = dispatch.tenant
    return tenant_context(tenant)


@shared_task(
    name="infrasynth.notifications.deliver_notification",
    bind=True,
    max_retries=3,
    default_retry_delay=60,
)
def deliver_notification(self, dispatch_id, tenant_id=None):
    from .models import NotificationDispatch
    from .services import NotificationService

    try:
        dispatch = NotificationDispatch.all_objects.select_related("template").get(pk=dispatch_id)
    except NotificationDispatch.DoesNotExist:
        logger.warning("Notification dispatch %s not found", dispatch_id)
        return None

    with _bind_dispatch_tenant(tenant_id, dispatch):
        service = NotificationService()
        try:
            service._execute_send(dispatch)
        except Exception as exc:  # noqa: BLE001
            logger.exception("Dispatch %s failed", dispatch_id)
            raise self.retry(exc=exc, countdown=60) from exc
        return dispatch_id


@shared_task(
    name="infrasynth.notifications.deliver_notification_with_failover",
    bind=True,
    max_retries=3,
    default_retry_delay=60,
)
def deliver_notification_with_failover(self, dispatch_id, channels, tenant_id=None):
    from .models import NotificationDispatch
    from .services import NotificationService

    try:
        dispatch = NotificationDispatch.all_objects.select_related("template").get(pk=dispatch_id)
    except NotificationDispatch.DoesNotExist:
        logger.warning("Notification dispatch %s not found", dispatch_id)
        return None

    with _bind_dispatch_tenant(tenant_id, dispatch):
        service = NotificationService()
        try:
            service._execute_failover(dispatch, channels)
        except Exception as exc:  # noqa: BLE001
            logger.exception("Dispatch %s failover failed", dispatch_id)
            raise self.retry(exc=exc, countdown=60) from exc
        return dispatch_id


@shared_task(name="infrasynth.notifications.retry_pending_dispatches")
def retry_pending_dispatches(batch_size=None):
    """Re-delivers dispatches whose backoff window has elapsed (beat-scheduled)."""
    from django.utils import timezone

    from infrasynth.shared.settings_utils import get_setting

    from .models import NotificationDispatch

    if batch_size is None:
        batch_size = int(get_setting("INFRASYNTH_NOTIFICATIONS", "RETRY_SCAN_BATCH_SIZE", 100))

    due = list(
        NotificationDispatch.all_objects.filter(
            status=NotificationDispatch.Status.RETRYING,
            next_retry_at__lte=timezone.now(),
        )
        .order_by("next_retry_at")
        .values_list("id", "tenant_id")[:batch_size]
    )
    for dispatch_id, tenant_id in due:
        deliver_notification.delay(dispatch_id, str(tenant_id) if tenant_id else None)
    return len(due)


@shared_task(name="infrasynth.notifications.purge_old_dispatches")
def purge_old_dispatches():
    """Deletes finished dispatches older than ``DISPATCH_LOG_RETENTION_DAYS``."""
    from datetime import timedelta

    from django.utils import timezone

    from infrasynth.shared.settings_utils import get_setting

    from .models import NotificationDispatch

    days = int(get_setting("INFRASYNTH_NOTIFICATIONS", "DISPATCH_LOG_RETENTION_DAYS", 90))
    if days <= 0:
        return 0
    cutoff = timezone.now() - timedelta(days=days)
    deleted, _ = NotificationDispatch.all_objects.filter(
        status__in=[NotificationDispatch.Status.SENT, NotificationDispatch.Status.FAILED],
        created_at__lt=cutoff,
    ).delete()
    return deleted