from django.db import models
from .carrier import Carrier
from .aircraft import Equipment
from .aerodrome import Aerodrome
from django.core.validators import MinValueValidator, MaxValueValidator
from simulator.utils import haversine_nm
from datetime import timedelta
from django.core.exceptions import ValidationError
from django.utils import timezone


class Flight(models.Model):
    carrier = models.ForeignKey(
        Carrier, on_delete=models.CASCADE, related_name="flights"
    )
    equipment = models.ForeignKey(
        Equipment, on_delete=models.CASCADE, related_name="flights"
    )
    origin = models.ForeignKey(
        Aerodrome, on_delete=models.CASCADE, related_name="departures"
    )
    destination = models.ForeignKey(
        Aerodrome, on_delete=models.CASCADE, related_name="arrivals"
    )

    flight_number = models.PositiveIntegerField(
        validators=[MinValueValidator(1), MaxValueValidator(9999)]
    )
    departure_time = models.DateTimeField()

    class Meta:
        constraints = [
            models.UniqueConstraint(
                fields=["carrier", "flight_number"], name="unique_flight_per_carrier"
            )
        ]

    def __str__(self):
        return f"{self.carrier.icao}{self.flight_number} {self.origin.icao} > {self.destination.icao}"

    @property
    def distance_nm(self) -> float:
        return haversine_nm(
            self.origin.latitude,
            self.origin.longitude,
            self.destination.latitude,
            self.destination.longitude,
        )

    @property
    def duration(self) -> timedelta:
        speed = self.equipment.model.cruise_speed_kt  # knots = nm/hr
        hours = self.distance_nm / speed
        return timedelta(hours=hours)

    @property
    def arrival_time(self):
        return self.departure_time + self.duration

    def clean(self):
        overlapping = Flight.objects.filter(
            equipment=self.equipment,
            departure_time__lt=self.arrival_time,
            arrival_time__gt=self.departure_time,
        ).exclude(pk=self.pk)

        if overlapping.exists():
            raise ValidationError(
                f"{self.equipment} is already assigned to another flight in this timeframe."
            )

    @property
    def status(self):
        now = timezone.now()
        if now < self.departure_time:
            return "Scheduled"
        elif self.departure_time <= now < self.arrival_time:
            return "In-Flight"
        else:
            return "Arrived"