from typing import Any, Dict

from django.contrib.contenttypes.fields import GenericRelation
from django.db import models

from ..agenda.models import Item
from ..core.models import Projector
from ..mediafiles.models import Mediafile
from ..utils.models import RESTModelMixin
from .access_permissions import TopicAccessPermissions


class TopicManager(models.Manager):
    """
    Customized model manager to support our get_full_queryset method.
    """
    def get_full_queryset(self):
        """
        Returns the normal queryset with all topics. In the background all
        attachments and the related agenda item are prefetched from the
        database.
        """
        return self.get_queryset().prefetch_related('attachments', 'agenda_items')


class Topic(RESTModelMixin, models.Model):
    """
    Model for slides with custom content. Used to be called custom slide.
    """
    access_permissions = TopicAccessPermissions()

    objects = TopicManager()

    title = models.CharField(max_length=256)
    text = models.TextField(blank=True)
    attachments = models.ManyToManyField(Mediafile, blank=True)

    # In theory there could be one then more agenda_item. But we support only
    # one. See the property agenda_item.
    agenda_items = GenericRelation(Item, related_name='topics')

    class Meta:
        default_permissions = ()

    def __str__(self):
        return self.title

    def delete(self, skip_autoupdate=False, *args, **kwargs):
        """
        Customized method to delete a topic. Ensures that a respective
        topic projector element is disabled.
        """
        Projector.remove_any(
            skip_autoupdate=skip_autoupdate,
            name='topics/topic',
            id=self.pk)
        return super().delete(skip_autoupdate=skip_autoupdate, *args, **kwargs)  # type: ignore

    """
    Container for runtime information for agenda app (on create or update of this instance).
    """
    agenda_item_update_information: Dict[str, Any] = {}

    @property
    def agenda_item(self):
        """
        Returns the related agenda item.
        """
        # We support only one agenda item so just return the first element of
        # the queryset.
        return self.agenda_items.all()[0]

    @property
    def agenda_item_id(self):
        """
        Returns the id of the agenda item object related to this object.
        """
        return self.agenda_item.pk

    def get_agenda_title(self):
        """
        Returns the title for the agenda.
        """
        return self.title

    def get_agenda_title_with_type(self):
        """
        Returns the agenda title. Topicy should not get a type postfix.
        """
        return self.get_agenda_title()