from django.contrib.auth.backends import ModelBackend
from django.contrib.auth import get_user_model


class EmailAuthBackend(ModelBackend):
    def authenticate(self, request, username=None, password=None, **kwargs):
        User = get_user_model()
        try:
            user = User.objects.get(email__iexact=username)
        except (User.DoesNotExist, User.MultipleObjectsReturned):
            return None
        if user.check_password(password) and self.user_can_authenticate(user):
            return user
        return None