import logging
from django.conf import settings
from django.core.cache import cache
from django.db import models
from django.contrib.auth.models import User
logger = logging.getLogger(__name__)
class NotificationQuerySet(models.QuerySet):
"""Custom QuerySet for Notification model"""
def update(self, *args, **kwargs):
"""Override update to ensure cache is invalidated on very call."""
super().update(*args, **kwargs)
user_pks = set(self.select_related("user").values_list('user__pk', flat=True))
for user_pk in user_pks:
NotificationManager.invalidate_user_notification_cache(user_pk)
[docs]
class NotificationManager(models.Manager):
USER_NOTIFICATION_COUNT_PREFIX = 'USER_NOTIFICATION_COUNT'
USER_NOTIFICATION_COUNT_CACHE_DURATION = 86_400
def get_queryset(self):
return NotificationQuerySet(self.model, using=self._db)
[docs]
def notify_user(
self, user: object, title: str, message: str = None, level: str = 'info'
) -> object:
"""Sends a new notification to user. Returns newly created notification object.
"""
max_notifications = self._max_notifications_per_user()
if self.filter(user=user).count() >= max_notifications:
to_be_deleted_qs = self.filter(user=user).order_by(
"-timestamp"
)[max_notifications - 1:]
for notification in to_be_deleted_qs:
notification.delete()
if not message:
message = title
if level not in self.model.Level:
level = self.model.Level.INFO
obj = self.create(user=user, title=title, message=message, level=level)
logger.info("Created notification %s", obj)
return obj
def _max_notifications_per_user(self) -> int:
"""Maximum number of notifications allowed per user."""
max_notifications = getattr(
settings,
"NOTIFICATIONS_MAX_PER_USER",
self.model.NOTIFICATIONS_MAX_PER_USER_DEFAULT
)
try:
max_notifications = int(max_notifications)
except ValueError:
max_notifications = None
if max_notifications is None or max_notifications < 0:
logger.warning(
"NOTIFICATIONS_MAX_PER_USER setting is invalid. Using default."
)
max_notifications = self.model.NOTIFICATIONS_MAX_PER_USER_DEFAULT
return max_notifications
[docs]
def user_unread_count(self, user_pk: int) -> int:
"""returns the cached unread count for a user given by user PK
Will return -1 if user can not be found
"""
cache_key = self._user_notification_cache_key(user_pk)
unread_count = cache.get(key=cache_key)
if not unread_count:
try:
user = User.objects.get(pk=user_pk)
except User.DoesNotExist:
unread_count = -1
else:
logger.debug(
'Updating notification cache for user with pk %s', user_pk
)
unread_count = user.notification_set.filter(viewed=False).count()
cache.set(
key=cache_key,
value=unread_count,
timeout=self.USER_NOTIFICATION_COUNT_CACHE_DURATION
)
else:
logger.debug(
'Returning notification count from cache for user with pk %s', user_pk
)
return unread_count
@classmethod
def invalidate_user_notification_cache(cls, user_pk: int) -> None:
cache.delete(key=cls._user_notification_cache_key(user_pk))
logger.debug('Invalided notification cache for user with pk %s', user_pk)
@classmethod
def _user_notification_cache_key(cls, user_pk: int) -> str:
return f'{cls.USER_NOTIFICATION_COUNT_PREFIX}_{user_pk}'