+from django.db import models
+from django.contrib.contenttypes.models import ContentType
+from django.core.paginator import Paginator, EmptyPage
+from django.template import Context
+from django.template.loader_tags import ExtendsNode, ConstantIncludeNode
+
+
+class ContentTypeLimiter(object):
+ def q_object(self):
+ return models.Q(pk__in=[])
+
+ def add_to_query(self, query, *args, **kwargs):
+ query.add_q(self.q_object(), *args, **kwargs)
+
+
+class ContentTypeRegistryLimiter(ContentTypeLimiter):
+ def __init__(self):
+ self.classes = []
+
+ def register_class(self, cls):
+ self.classes.append(cls)
+
+ def unregister_class(self, cls):
+ self.classes.remove(cls)
+
+ def q_object(self):
+ contenttype_pks = []
+ for cls in self.classes:
+ try:
+ if issubclass(cls, models.Model):
+ if not cls._meta.abstract:
+ contenttype = ContentType.objects.get_for_model(cls)
+ contenttype_pks.append(contenttype.pk)
+ except:
+ pass
+ return models.Q(pk__in=contenttype_pks)
+
+
+class ContentTypeSubclassLimiter(ContentTypeLimiter):
+ def __init__(self, cls, inclusive=False):
+ self.cls = cls
+ self.inclusive = inclusive
+
+ def q_object(self):
+ contenttype_pks = []
+ def handle_subclasses(cls):
+ for subclass in cls.__subclasses__():
+ try:
+ if issubclass(subclass, models.Model):
+ if not subclass._meta.abstract:
+ if not self.inclusive and subclass is self.cls:
+ continue
+ contenttype = ContentType.objects.get_for_model(subclass)
+ contenttype_pks.append(contenttype.pk)
+ handle_subclasses(subclass)
+ except:
+ pass
+ handle_subclasses(self.cls)
+ return models.Q(pk__in=contenttype_pks)
+
+