from django.conf import settings
from django.db import models
from django.db.models import F, Q
from django.urls import reverse

class Venue(models.Model):
    name = models.CharField(max_length=80)
    code = models.SlugField(unique=True)
    access_note = models.CharField(max_length=160, blank=True, default="")
    def __str__(self):
        return self.name

class WorkshopQuerySet(models.QuerySet):
    def public(self):
        return self.filter(published=True)

class Workshop(models.Model):
    title = models.CharField(max_length=100)
    slug = models.SlugField(unique=True)
    venue = models.ForeignKey(Venue, on_delete=models.PROTECT, related_name="workshops")
    starts_at = models.DateTimeField()
    capacity = models.PositiveIntegerField()
    remaining = models.PositiveIntegerField()
    published = models.BooleanField(default=False)
    objects = WorkshopQuerySet.as_manager()
    class Meta:
        ordering = ["starts_at", "pk"]
        constraints = [
            models.CheckConstraint(condition=Q(capacity__gte=1), name="capacity_positive"),
            models.CheckConstraint(condition=Q(remaining__lte=F("capacity")), name="remaining_within_capacity"),
        ]
    def __str__(self):
        return self.title
    def get_absolute_url(self):
        return reverse("workshops:detail", kwargs={"slug": self.slug})

class Reservation(models.Model):
    workshop = models.ForeignKey(Workshop, on_delete=models.PROTECT, related_name="reservations")
    user = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.PROTECT)
    seats = models.PositiveSmallIntegerField()
    created_at = models.DateTimeField(auto_now_add=True)
    class Meta:
        constraints = [
            models.UniqueConstraint(fields=["workshop", "user"], name="one_reservation_per_user"),
            models.CheckConstraint(condition=Q(seats__gte=1, seats__lte=4), name="seats_one_to_four"),
        ]