from django.conf import settings
from django.core.validators import MinValueValidator
from django.db import models

from items.models import Item


class Cart(models.Model):
    user = models.OneToOneField(
        settings.AUTH_USER_MODEL,
        on_delete=models.CASCADE,
        related_name="cart",
        verbose_name="Пользователь",
    )
    created_at = models.DateTimeField(auto_now_add=True, verbose_name="Дата создания")
    updated_at = models.DateTimeField(auto_now=True, verbose_name="Дата обновления")

    class Meta:
        verbose_name = "Корзина"
        verbose_name_plural = "Корзины"

    def __str__(self):
        return f"Корзина пользователя {self.user}"


class CartItem(models.Model):
    cart = models.ForeignKey(
        Cart,
        on_delete=models.CASCADE,
        related_name="items",
        verbose_name="Корзина",
    )
    item = models.ForeignKey(
        Item,
        on_delete=models.CASCADE,
        related_name="cart_entries",
        verbose_name="Товар",
    )
    quantity = models.PositiveIntegerField(
        validators=[MinValueValidator(1)],
        verbose_name="Количество",
    )
    created_at = models.DateTimeField(auto_now_add=True, verbose_name="Дата создания")
    updated_at = models.DateTimeField(auto_now=True, verbose_name="Дата обновления")

    class Meta:
        ordering = ("created_at", "id")
        constraints = [
            models.UniqueConstraint(fields=("cart", "item"), name="unique_cart_item_per_cart"),
        ]
        verbose_name = "Позиция корзины"
        verbose_name_plural = "Позиции корзины"

    def __str__(self):
        return f"{self.item} x {self.quantity}"

    @property
    def subtotal(self):
        return self.item.price * self.quantity