import contextvars

from django.core.exceptions import ImproperlyConfigured
from django.db import models

current_event = contextvars.ContextVar("current_event", default=None)


class EventScopedQuerySet(models.QuerySet):
    def for_current_event(self):
        event = current_event.get()
        if event is None:
            raise ImproperlyConfigured(
                f"{self.model.__name__}.for_event was used outside an event-scoped request"
            )
        return self.filter(event=event)


class EventScopedManager(models.Manager.from_queryset(EventScopedQuerySet)):
    def get_queryset(self):
        return super().get_queryset().for_current_event()