import django
from django.contrib.auth.models import Group
from django.db import models
from django.db.models.fields.related_descriptors import ReverseOneToOneDescriptor
from django.db.transaction import atomic
from django.utils.translation import ugettext_lazy as _
from django.conf import settings


class UserSAMLIdentifier(models.Model):
    user = models.ForeignKey(
        verbose_name=_('user'),
        to=settings.AUTH_USER_MODEL,
        related_name='saml_identifiers')
    issuer = models.TextField(
        verbose_name=_('Issuer'))
    name_id = models.TextField(
        verbose_name=_('SAML identifier'))
    created = models.DateTimeField(
        verbose_name=_('created'),
        auto_now_add=True)

    class Meta:
        verbose_name = _('user SAML identifier')
        verbose_name_plural = _('users SAML identifiers')
        unique_together = (('issuer', 'name_id'),)


class AutoSingleRelatedObjectDescriptor(ReverseOneToOneDescriptor):
    """From https://github.com/skorokithakis/django-annoying
    Temporary, we will write a migration after testing"""

    @atomic
    def __get__(self, instance, instance_type=None):
        model = getattr(self.related, 'related_model', self.related.model)

        try:
            return (
                super(AutoSingleRelatedObjectDescriptor, self)
                .__get__(instance, instance_type)
            )
        except model.DoesNotExist:
            # Using get_or_create instead() of save() or create() as it better handles race conditions
            obj, _ = model.objects.get_or_create(**{self.related.field.name: instance})

            # Update Django's cache, otherwise first 2 calls to obj.relobj
            # will return 2 different in-memory objects
            if django.VERSION >= (2, 0):
                self.related.set_cached_value(instance, obj)
                self.related.field.set_cached_value(obj, instance)
            else:
                setattr(instance, self.cache_name, obj)
                setattr(obj, self.related.field.get_cache_name(), instance)
            return obj


class AutoOneToOneField(models.OneToOneField):
    """From https://github.com/skorokithakis/django-annoying"""

    def contribute_to_related_class(self, cls, related):
        setattr(
            cls,
            related.get_accessor_name(),
            AutoSingleRelatedObjectDescriptor(related)
        )


class AuthenticationLevel(models.Model):
    group = AutoOneToOneField(Group, related_name='auth_level')
    # ou plutot laisser blanc pour qu'il y ait une erreur si on
    # a pas recu les niveaux ?
    value = models.PositiveSmallIntegerField(default=1)