from authens.backends import ENSCASBackend, ENSCASError
from authens.utils import parse_entrance_year

from fiches.models import Profile


class BackendFiches(ENSCASBackend):
    """Wrapper around AuthENS's CAS authentication backend.
    Ensures the required field promotion year is non-empty"""

    def create_user(self, username, attributes):
        """create a CAS user
        overwrite to add required promotion"""
        user = super().create_user(username, attributes)
        entrance_year = parse_entrance_year(attributes.get("homeDirectory"))
        if entrance_year is None:
            raise ENSCASError("Entrance year not available")
        Profile.objects.create(user=user, promotion=entrance_year)
        return user