"""
Signals for QI Projects.

- Sends a notification when a task is assigned.
- Keeps `team_members` in sync with the champion + manager of each linked
  department whenever the `departments` M2M changes.
"""

import logging

from django.db.models.signals import m2m_changed, post_save
from django.dispatch import receiver

from apps.projects.models import QIProject

logger = logging.getLogger(__name__)


@receiver(post_save, sender="projects.QIProjectTask")
def notify_task_assignment(sender, instance, created, **kwargs):
    """Send an in-app notification when a QI task is assigned to a staff member."""
    if not instance.assigned_to:
        return

    # Only notify on new assignments (creation with an assignee)
    if not created:
        return

    user = getattr(instance.assigned_to, "user", None)
    if not user:
        return

    try:
        from apps.notifications.services import create_in_app_notification

        create_in_app_notification(
            user=user,
            title=f"New QI Task: {instance.title}",
            message=f"You have been assigned a task in project '{instance.project.name}'.",
            notification_type="qi_task_assigned",
            action_url=f"/projects/{instance.project.id}/",
        )
    except Exception as e:
        logger.warning(f"Failed to send QI task notification: {e}")


@receiver(m2m_changed, sender=QIProject.departments.through)
def sync_team_on_departments_change(sender, instance, action, **kwargs):
    """Rebuild the derived `team_members` set whenever the project's departments change.

    Fires on `post_add` / `post_remove` / `post_clear` so that programmatic,
    admin, and form-driven edits all stay consistent. The sync is idempotent.
    """
    if action not in ("post_add", "post_remove", "post_clear"):
        return
    if not instance.pk:
        return
    try:
        instance.sync_team_members_from_departments()
    except Exception as e:  # defensive: never break an M2M write on sync failure
        logger.warning(f"Failed to sync QI team members for project {instance.pk}: {e}")