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, [])