Add a Singleton Model class and an AnonymousUserSingleton model to support adding permissions and access to anonymous users

apps/common/models.py

@@ -1,3 +1,43 @@
 from django.db import models
+from django.utils.translation import ugettext_lazy as _
+from django.contrib.auth.models import AnonymousUser
 
-# Create your models here.
+SINGLETON_LOCK_ID = 1
+
+
+class SingletonManager(models.Manager):
+    def get(self, **kwargs):
+        instance, created = self.model.objects.get_or_create(lock_id=SINGLETON_LOCK_ID, **kwargs)
+        return instance
+
+
+class Singleton(models.Model):
+    lock_id = models.CharField(max_length=1, default=SINGLETON_LOCK_ID, editable=False, verbose_name=_(u'lock field'), unique=True)
+
+    objects = SingletonManager()
+
+    def save(self, *args, **kwargs):
+        self.id = 1
+        super(Singleton, self).save(*args, **kwargs)
+
+    def delete(self):
+        pass
+
+    class Meta:
+        abstract = True
+
+
+class AnonymousUserSingletonManager(SingletonManager):
+    def passthru_check(self, user):
+        if isinstance(user, AnonymousUser):
+            return self.model.objects.get()
+        else:
+            return user
+    
+
+class AnonymousUserSingleton(Singleton):
+    objects = AnonymousUserSingletonManager()
+    
+    class Meta:
+        verbose_name = _(u'anonymous user')
+        verbose_name_plural = _(u'anonymous user')