from django.db import models
from django.db.models import F, Q, Sum


class TimeStampedModel(models.Model):
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

    class Meta:
        abstract = True


class Show(TimeStampedModel):
    title = models.CharField(max_length=200)
    slug = models.SlugField(max_length=220, unique=True)
    summary = models.TextField(blank=True)
    description = models.TextField(blank=True)
    poster_image = models.URLField(blank=True)
    uploaded_image = models.ImageField(upload_to="shows/", blank=True)
    is_published = models.BooleanField(default=False, db_index=True)

    class Meta:
        ordering = ["title"]
        indexes = [
            models.Index(fields=["slug"]),
            models.Index(fields=["is_published"]),
        ]

    def __str__(self):
        return self.title

    def image_url(self, request=None):
        if self.uploaded_image:
            image_url = self.uploaded_image.url
            if request is not None:
                return request.build_absolute_uri(image_url)
            return image_url
        return self.poster_image


class Venue(TimeStampedModel):
    name = models.CharField(max_length=200)
    slug = models.SlugField(max_length=220, unique=True)
    address = models.CharField(max_length=255)
    city = models.CharField(max_length=120)
    notes = models.TextField(blank=True)

    class Meta:
        ordering = ["name"]
        indexes = [
            models.Index(fields=["slug"]),
            models.Index(fields=["city"]),
        ]

    def __str__(self):
        return self.name


class Performance(TimeStampedModel):
    show = models.ForeignKey(Show, on_delete=models.PROTECT, related_name="performances")
    venue = models.ForeignKey(Venue, on_delete=models.PROTECT, related_name="performances")
    starts_at = models.DateTimeField(db_index=True)
    room_capacity = models.PositiveIntegerField()
    manually_occupied_seats = models.PositiveIntegerField(default=0)
    additional_seats = models.PositiveIntegerField(default=0)
    is_booking_enabled = models.BooleanField(default=True, db_index=True)

    class Meta:
        ordering = ["starts_at"]
        indexes = [
            models.Index(fields=["show", "starts_at"]),
            models.Index(fields=["venue", "starts_at"]),
            models.Index(fields=["is_booking_enabled", "starts_at"]),
        ]
        constraints = [
            models.CheckConstraint(
                condition=Q(manually_occupied_seats__lte=F("room_capacity") + F("additional_seats")),
                name="performance_manual_seats_within_capacity",
            ),
        ]

    def __str__(self):
        return f"{self.show} at {self.starts_at:%Y-%m-%d %H:%M}"

    @property
    def configured_capacity(self):
        return self.room_capacity + self.additional_seats - self.manually_occupied_seats

    def confirmed_seats(self):
        result = self.reservations.filter(status="confirmed").aggregate(total=Sum("party_size"))
        return result["total"] or 0

    def available_seats(self):
        return self.configured_capacity - self.confirmed_seats()