from authens.backends import ENSCASBackend

from django.contrib.auth import get_user_model
from django.contrib.auth.backends import ModelBackend
from django.core.exceptions import PermissionDenied

User = get_user_model()


class CASBackend(ENSCASBackend):
    """ENS CAS authentication backend, customized to get the full name at connection."""

    def clean_cas_login(self, cas_login):
        return f"cas__{cas_login.strip().lower()}"

    def create_user(self, username, attributes):
        email = attributes.get("email")
        name = attributes.get("name")

        return User.objects.create_user(username=username, email=email, full_name=name)

    def _get_or_create(self, cas_login, attributes):
        try:
            return super()._get_or_create(cas_login, attributes)
        except ValueError:
            raise PermissionDenied


class PwdBackend(ModelBackend):
    """Password authentication"""

    def authenticate(self, request, username=None, password=None):
        if username is None or password is None:
            return None

        return super().authenticate(
            request, username=f"pwd__{username}", password=password
        )


class ElectionBackend(ModelBackend):
    """Authentication for a specific election.

    Given a login and an election, we check if the user `{election.id}__{login}`
    exists, and then if the password matches.
    """

    def authenticate(self, request, login=None, password=None, election_id=None):
        if login is None or password is None or election_id is None:
            return None

        try:
            user = User.objects.get(
                username=f"{election_id}__{login}", election=election_id
            )
        except User.DoesNotExist:
            return None

        if user.check_password(password):
            return user