from datetime import date

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


class FuelPurchase(models.Model):

    GAS_STATION_CHOICES = [
        (0, '-'),
        (1, 'Neste'),
        (2, 'Teboil'),
        (3, 'ABC'),
        (4, 'Shell'),
        (5, 'St1'),
        (6, 'SEO'),
        (7, 'ysi5'),
    ]

    OCTANE_CHOICES = [
        (95, '95'),
        (98, '98'),
    ]

    CAR_CHOICES = [
        (0, '_'),
        (1, 'Renault'),
        (2, 'Nissan'),
        (3, 'Smart'),
    ]

    purchase_date = models.DateField(null=False, blank=False, default=date.today, verbose_name="Purchase Date")
    total_cost = models.DecimalField(null=False, blank=False, max_digits=10, decimal_places=2, verbose_name="Total Cost (€)")
    price_per_litre = models.DecimalField(null=False, blank=False, max_digits=6, decimal_places=3, verbose_name="Price per Litre (€)")
    amount_litres = models.DecimalField(null=False, blank=False, max_digits=7, decimal_places=2, verbose_name="Amount (litres)")
    octane = models.IntegerField(choices=OCTANE_CHOICES, default=95, verbose_name="Octane")
    gas_station = models.IntegerField(choices=GAS_STATION_CHOICES, default=1, verbose_name="Gas Station")
    car = models.IntegerField(choices=CAR_CHOICES, default=3, verbose_name="Car")

    class Meta:
        constraints = [
            models.UniqueConstraint(
                fields=[
                    'purchase_date',
                    'total_cost',
                    'price_per_litre',
                    'amount_litres',
                    'octane',
                    'gas_station',
                    'car',
                ],
                name='unique_fuel_purchase'
            ),
            models.CheckConstraint(
                check=Q(total_cost__gt=0) & Q(total_cost__lt=100),
                name="total_cost_range"
            ),
            models.CheckConstraint(
                check=Q(price_per_litre__gt=0) & Q(price_per_litre__lt=5),
                name="price_per_litre_range"
            ),
            models.CheckConstraint(
                check=Q(amount_litres__gt=0) & Q(amount_litres__lt=100),
                name="amount_litres_range"
            ),
        ]
        verbose_name = "Fuel Purchase"
        verbose_name_plural = "Fuel Purchases"

    def save(self, *args, **kwargs):
        if not self.amount_litres and self.price_per_litre:
            self.amount_litres = self.total_cost / self.price_per_litre
        super().save(*args, **kwargs)

    def __str__(self):
        date_str = self.purchase_date.strftime("%d.%m.%Y")
        return f"{date_str} : {self.total_cost} € - {self.price_per_litre} €/L"