from django.db import models

from users.models import CustomUser


class Event(models.Model):
    date = models.DateField()
    capacity = models.IntegerField(default=6)
    note = models.TextField(max_length=1024, default="")
    responsible_person = models.ForeignKey(CustomUser, null=True, on_delete=models.SET_NULL)

    def __str__(self):
        return f"{self.date}"


class TimeSlot(models.Model):
    MORNING, AFTERNOON, EVENING = range(3)
    TIME_SLOTS = {
        MORNING:   "voormiddag",
        AFTERNOON: "namiddag",
        EVENING:   "avond",
    }
    time = models.IntegerField(choices=TIME_SLOTS.items(), default=MORNING)
    event = models.ForeignKey(Event, on_delete=models.CASCADE)

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

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

    def time_str(self):
        return TimeSlot.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 timeslot"
        return registrations[0]


class EventRegistration(models.Model):
    INTERESTED = "I"
    ADMITTED = "A"
    REGISTRATION_STATE = {
        INTERESTED: "op wachtlijst",
        ADMITTED:   "bevestigd",
    }
    time_slot = models.ForeignKey(TimeSlot, 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=["time_slot", "user"], name="register_only_once_per_timeslot"
            ),
        ]

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

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