from django.db import models
from django.utils.translation import ugettext_lazy as _
from django.contrib.auth.models import AnonymousUser

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')