Stats migrations.
[wolnelektury.git] / src / newtagging / managers.py
1 # This file is part of Wolnelektury, licensed under GNU Affero GPLv3 or later.
2 # Copyright © Fundacja Nowoczesna Polska. See NOTICE for more information.
3 #
4 """
5 Custom managers for Django models registered with the tagging
6 application.
7 """
8 from django.contrib.contenttypes.models import ContentType
9 from django.db import models
10
11
12 class ModelTagManager(models.Manager):
13     """
14     A manager for retrieving tags for a particular model.
15     """
16     def __init__(self, tag_model):
17         super(ModelTagManager, self).__init__()
18         self.tag_model = tag_model
19
20     def get_queryset(self):
21         content_type = ContentType.objects.get_for_model(self.model)
22         return self.tag_model.objects.filter(
23             items__content_type__pk=content_type.pk).distinct()
24
25     def related(self, tags, *args, **kwargs):
26         return self.tag_model.objects.related_for_model(tags, self.model, *args, **kwargs)
27
28     def usage(self, *args, **kwargs):
29         return self.tag_model.objects.usage_for_model(self.model, *args, **kwargs)
30
31
32 class ModelTaggedItemManager(models.Manager):
33     """
34     A manager for retrieving model instances based on their tags.
35     """
36     def __init__(self, tag_model):
37         super(ModelTaggedItemManager, self).__init__()
38         self.intermediary_table_model = tag_model.objects.intermediary_table_model
39
40     def related_to(self, obj, queryset=None):
41         if queryset is None:
42             return self.intermediary_table_model.objects.get_related(
43                 obj, self.model)
44         else:
45             return self.intermediary_table_model.objects.get_related(
46                 obj, queryset)
47
48     def with_all(self, tags, queryset=None):
49         if queryset is None:
50             return self.intermediary_table_model.objects.get_by_model(self.model, tags)
51         else:
52             return self.intermediary_table_model.objects.get_by_model(queryset, tags)
53
54     def with_any(self, tags, queryset=None):
55         if queryset is None:
56             return self.intermediary_table_model.objects.get_union_by_model(self.model, tags)
57         else:
58             return self.intermediary_table_model.objects.get_union_by_model(queryset, tags)
59
60
61 class TagDescriptor(object):
62     """
63     A descriptor which provides access to a ``ModelTagManager`` for
64     model classes and simple retrieval, updating and deletion of tags
65     for model instances.
66     """
67     def __init__(self, tag_model):
68         self.tag_model = tag_model
69
70     def __get__(self, instance, owner):
71         if not instance:
72             tag_manager = ModelTagManager(self.tag_model)
73             tag_manager.model = owner
74             return tag_manager
75         else:
76             return self.tag_model.objects.get_for_object(instance)
77
78     def __set__(self, instance, value):
79         self.tag_model.objects.update_tags(instance, value)
80
81     def __del__(self, instance):
82         self.tag_model.objects.update_tags(instance, [])