--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/web/lib/tagging/managers.py	Fri Jan 22 18:23:34 2010 +0100
@@ -0,0 +1,68 @@
+"""
+Custom managers for Django models registered with the tagging
+application.
+"""
+from django.contrib.contenttypes.models import ContentType
+from django.db import models
+
+from tagging.models import Tag, TaggedItem
+
+class ModelTagManager(models.Manager):
+    """
+    A manager for retrieving tags for a particular model.
+    """
+    def get_query_set(self):
+        ctype = ContentType.objects.get_for_model(self.model)
+        return Tag.objects.filter(
+            items__content_type__pk=ctype.pk).distinct()
+
+    def cloud(self, *args, **kwargs):
+        return Tag.objects.cloud_for_model(self.model, *args, **kwargs)
+
+    def related(self, tags, *args, **kwargs):
+        return Tag.objects.related_for_model(tags, self.model, *args, **kwargs)
+
+    def usage(self, *args, **kwargs):
+        return Tag.objects.usage_for_model(self.model, *args, **kwargs)
+
+class ModelTaggedItemManager(models.Manager):
+    """
+    A manager for retrieving model instances based on their tags.
+    """
+    def related_to(self, obj, queryset=None, num=None):
+        if queryset is None:
+            return TaggedItem.objects.get_related(obj, self.model, num=num)
+        else:
+            return TaggedItem.objects.get_related(obj, queryset, num=num)
+
+    def with_all(self, tags, queryset=None):
+        if queryset is None:
+            return TaggedItem.objects.get_by_model(self.model, tags)
+        else:
+            return TaggedItem.objects.get_by_model(queryset, tags)
+
+    def with_any(self, tags, queryset=None):
+        if queryset is None:
+            return TaggedItem.objects.get_union_by_model(self.model, tags)
+        else:
+            return TaggedItem.objects.get_union_by_model(queryset, tags)
+
+class TagDescriptor(object):
+    """
+    A descriptor which provides access to a ``ModelTagManager`` for
+    model classes and simple retrieval, updating and deletion of tags
+    for model instances.
+    """
+    def __get__(self, instance, owner):
+        if not instance:
+            tag_manager = ModelTagManager()
+            tag_manager.model = owner
+            return tag_manager
+        else:
+            return Tag.objects.get_for_object(instance)
+
+    def __set__(self, instance, value):
+        Tag.objects.update_tags(instance, value)
+
+    def __delete__(self, instance):
+        Tag.objects.update_tags(instance, None)