from django.db import models
from django.db.models import Q

from users.models import CustomUser


class Event(models.Model):
    MORNING, AFTERNOON, EVENING = range(3)
    TIME_SLOTS = {
        MORNING:   "voormiddag",
        AFTERNOON: "namiddag",
        EVENING:   "avond",
    }
    date = models.DateField()
    time = models.IntegerField(choices=TIME_SLOTS.items(), default=MORNING)
    capacity = models.IntegerField(default=6)


    def __str__(self):
        return f"{self.date} {self.TIME_SLOTS[self.time]}"


    def time_str(self):
        return Event.TIME_SLOTS[self.time]


    def count_with_status(self, status):
        return self.eventregistration_set.filter(state=status).count()


    def count_interested(self):
        return self.count_with_status(EventRegistration.INTERESTED)


    def count_admitted(self):
        return self.count_with_status(EventRegistration.ADMITTED)


    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(models.Model):
    INTERESTED = "I"
    ADMITTED   = "A"
    REGISTRATION_STATE = {
        INTERESTED: "op wachtlijst",
        ADMITTED:   "bevestigd",
    }
    event = models.ForeignKey(Event, on_delete=models.CASCADE)
    user = models.ForeignKey(CustomUser, on_delete=models.CASCADE)
    state = models.CharField(max_length=1, choices=REGISTRATION_STATE.items())


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


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


    def state_str(self):
        return EventRegistration.REGISTRATION_STATE[self.state]