from django.db import models
from model_utils.models import TimeStampedModel

from users.models import CustomUser


class Event(models.Model):
    start_year = models.IntegerField(default=2020)

    def __str__(self):
        return f"{self.start_year}-{self.start_year + 1}"

    def count_registrations(self):
        return self.eventregistration_set.count()
    
    def count_registrations_accepted(self):
        return self.eventregistration_set.filter(accepted=True).count()

    def registration_of(self, user):
        if not user.is_authenticated:
            return None

        registrations = self.eventregistration_set.filter(user=user).all()
        if not registrations:
            return None
        assert (
            len(registrations) == 1
        ), "Registrations should be unique per user and event"
        return registrations[0]


class EventRegistration(TimeStampedModel):
    event = models.ForeignKey(Event, on_delete=models.CASCADE)
    user = models.ForeignKey(CustomUser, on_delete=models.CASCADE)
    # A user is by default valid.
    # The board can then check if a user has indeed been active in any way and they can invalidate the membership
    accepted = models.BooleanField(default=True)

    class Meta:
        constraints = [
            models.UniqueConstraint(
                fields=["event", "user"], name="register_only_once_per_event"
            ),
        ]

    def __str__(self):
        return f"Reservation[{self.user.username}:{self.event.start_year}]"