from django.db.models import Sum
from apps.authorization.models import Role, UserRelations
from django.db.models.signals import post_save, post_delete
from django.dispatch import receiver


@receiver([post_save], sender=UserRelations)
def sync_role_permissions(sender, instance, **kwargs):
    """ add role permissions to user relation permissions in is null """

    # if _from_signal=True prevent from maximum recursion loop
    if getattr(instance, '_from_signal', False):
        return

    if instance.role:
        permissions = instance.role.permissions.all()
    if not instance.permissions.exists():
        instance.permissions.add(*permissions)  # noqa

    instance._from_signal = True
    instance.save()