from django.db import models
from django.utils import timezone

from apps.core.models import TimeStampedModel, UUIDModel


class Facility(UUIDModel, TimeStampedModel):
    name = models.CharField(max_length=200)

    def __str__(self) -> str:
        return self.name


class ProcessingLine(UUIDModel, TimeStampedModel):
    facility = models.ForeignKey(Facility, on_delete=models.CASCADE, related_name="lines")
    name = models.CharField(max_length=200)

    def __str__(self) -> str:
        return f"{self.facility.name} / {self.name}"


class Holiday(UUIDModel):
    date = models.DateField(unique=True)


class FacilitySchedule(UUIDModel, TimeStampedModel):
    """Per-facility, per-date availability: capacity for the day and days off.

    If a schedule row exists for a date and ``is_open`` is False, no slots are
    generated for that day. ``capacity``/``start_time``/``end_time`` override the
    global Reservation settings for that date.
    """

    facility = models.ForeignKey(Facility, on_delete=models.CASCADE, related_name="schedules")
    date = models.DateField(db_index=True)
    is_open = models.BooleanField(default=True)
    capacity = models.PositiveIntegerField(default=2)
    start_time = models.TimeField(null=True, blank=True)
    end_time = models.TimeField(null=True, blank=True)
    note = models.CharField(max_length=200, blank=True)

    class Meta:
        ordering = ["-date"]
        constraints = [
            models.UniqueConstraint(fields=["facility", "date"], name="uniq_facility_schedule_date")
        ]

    def __str__(self) -> str:
        return f"{self.facility.name} {self.date}"


class Slot(UUIDModel):
    facility = models.ForeignKey(Facility, on_delete=models.CASCADE, related_name="slots")
    line = models.ForeignKey(
        ProcessingLine, on_delete=models.CASCADE, related_name="slots", null=True, blank=True
    )
    date = models.DateField(db_index=True)
    start_time = models.TimeField()
    end_time = models.TimeField()
    capacity = models.PositiveIntegerField(default=1)
    max_weight_kg = models.DecimalField(max_digits=12, decimal_places=2, null=True, blank=True)
    booked_count = models.PositiveIntegerField(default=0)
    blocked = models.BooleanField(default=False)

    class Meta:
        constraints = [
            models.UniqueConstraint(fields=["facility", "line", "date", "start_time"], name="uniq_slot_time")
        ]

    def is_available(self) -> bool:
        return (
            not self.blocked
            and self.booked_count < self.capacity
            and self.date >= timezone.localdate()
        )


class Reservation(UUIDModel, TimeStampedModel):
    class Status(models.TextChoices):
        PENDING = "pending", "Pending approval"
        CONFIRMED = "confirmed", "Confirmed"
        REJECTED = "rejected", "Rejected"
        ARRIVED = "arrived", "Arrived"
        WEIGHED = "weighed", "Weighed"
        CANCELLED = "cancelled", "Cancelled"
        EXPIRED = "expired", "Expired"

    title = models.CharField(max_length=200, blank=True)
    customer = models.ForeignKey("accounts.Customer", on_delete=models.CASCADE, related_name="reservations")
    slot = models.ForeignKey(Slot, on_delete=models.PROTECT, related_name="reservations")
    status = models.CharField(max_length=16, choices=Status.choices, default=Status.PENDING)
    notes = models.TextField(blank=True)
    approved_by = models.ForeignKey(
        "accounts.User", null=True, blank=True, on_delete=models.SET_NULL, related_name="approved_reservations"
    )
    approved_at = models.DateTimeField(null=True, blank=True)

    class Meta:
        ordering = ["-created_at"]

    def __str__(self) -> str:
        return self.title or f"Reservation {self.id}"