from decimal import Decimal
from typing import Any

from django.core.exceptions import ValidationError
from django.utils import formats

from items.models import Item
from orders.models import Cart, CartItem


def format_currency(value: Decimal) -> str:
    return f"{formats.number_format(value, 2)} руб."


def get_or_create_cart(user: Any) -> Cart:
    cart, _ = Cart.objects.get_or_create(user=user)
    return cart


def get_user_cart_item_ids(user: Any) -> set[int]:
    if not getattr(user, "is_authenticated", False):
        return set()

    return set(
        CartItem.objects.filter(cart__user=user).values_list("item_id", flat=True)
    )


def get_user_cart(user: Any) -> Cart | None:
    if not getattr(user, "is_authenticated", False):
        return None

    return (
        Cart.objects.filter(user=user)
        .prefetch_related("items__item__images")
        .select_related("user")
        .first()
    )


def add_item_to_cart(user: Any, item: Item, quantity: int = 1) -> tuple[CartItem, bool]:
    if quantity < 1:
        raise ValidationError("Количество товара должно быть не меньше 1.")

    if not item.is_available:
        raise ValidationError("Недоступный товар нельзя добавить в корзину.")

    cart = get_or_create_cart(user)
    cart_item, created = CartItem.objects.get_or_create(
        cart=cart,
        item=item,
        defaults={"quantity": quantity},
    )
    return cart_item, created


def remove_item_from_cart(user: Any, item_id: int) -> bool:
    deleted, _ = CartItem.objects.filter(cart__user=user, item_id=item_id).delete()
    return bool(deleted)


def update_cart_item_quantity(user: Any, item_id: int, quantity: int) -> CartItem:
    if quantity < 1:
        raise ValidationError("Количество товара должно быть не меньше 1.")

    cart_item = CartItem.objects.select_related("item").get(cart__user=user, item_id=item_id)
    cart_item.quantity = quantity
    cart_item.save(update_fields=["quantity", "updated_at"])
    return cart_item