From b95ea4d6ce3e586d5d56aae3e5351cba6d79fd67 Mon Sep 17 00:00:00 2001
From: Valentin Deniaud <vdeniaud@entrouvert.com>
Date: Fri, 29 Mar 2019 16:30:39 +0100
Subject: [PATCH] wip add auth_levels

---
 mellon/models.py | 44 +++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 43 insertions(+), 1 deletion(-)

diff --git a/mellon/models.py b/mellon/models.py
index 20aba33..b89e7f4 100644
--- a/mellon/models.py
+++ b/mellon/models.py
@@ -1,5 +1,8 @@
+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
 
@@ -23,8 +26,47 @@ class UserSAMLIdentifier(models.Model):
         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 = models.OneToOneField(Group, related_name='auth_level')
+    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)