from datetime import date

from django.db import models
from django.db.models import Q


class MonthlyTrip(models.Model):
    MONTH_CHOICES = [
        (1, 'January'), (2, 'February'), (3, 'March'), (4, 'April'),
        (5, 'May'), (6, 'June'), (7, 'July'), (8, 'August'),
        (9, 'September'), (10, 'October'), (11, 'November'), (12, 'December'),
    ]

    year = models.PositiveIntegerField(verbose_name="Year")
    month = models.PositiveSmallIntegerField(choices=MONTH_CHOICES, verbose_name="Month")
    kilometers = models.PositiveIntegerField(default=0, verbose_name="Kilometers")

    class Meta:
        constraints = [
            models.UniqueConstraint(fields=['year', 'month'], name='unique_monthly_trip')
        ]
        verbose_name = "Monthly Trip"
        verbose_name_plural = "Monthly Trips"

    def __str__(self):
        return f"{self.month:02d}.{self.year} : {self.kilometers} km"


class FuelPurchase(models.Model):
    GAS_STATION_CHOICES = [
        (0, 'Unknown'),
        (1, 'Neste'),
        (2, 'Teboil'),
        (3, 'ABC'),
        (4, 'Shell'),
        (5, 'St1'),
        (6, 'SEO'),
        (7, 'Ysi5'),
    ]

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

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

    purchase_date = models.DateField(default=date.today, verbose_name="Purchase Date")
    total_cost = models.DecimalField(max_digits=10, decimal_places=2, verbose_name="Total Cost (€)")
    price_per_litre = models.DecimalField(max_digits=6, decimal_places=3, verbose_name="Price per Litre (€)")
    amount_litres = models.DecimalField(max_digits=7, decimal_places=2, verbose_name="Amount (litres)")
    octane = models.PositiveSmallIntegerField(choices=OCTANE_CHOICES, default=95, verbose_name="Octane")
    gas_station = models.PositiveSmallIntegerField(choices=GAS_STATION_CHOICES, default=0, verbose_name="Gas Station")
    car = models.PositiveSmallIntegerField(choices=CAR_CHOICES, default=0, verbose_name="Car")
    monthly_trip = models.ForeignKey(MonthlyTrip, on_delete=models.CASCADE, related_name='fuel_purchases', verbose_name="Monthly Trip")

    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=1000), 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

        if not self.monthly_trip_id:
            month = self.purchase_date.month
            year = self.purchase_date.year
            monthly_trip, created = MonthlyTrip.objects.get_or_create(
                year=year,
                month=month,
                defaults={'kilometers': 0}
            )
            self.monthly_trip = monthly_trip

        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"