"""

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)