from decimal import Decimal

from django.contrib import messages
from django.contrib.auth.decorators import login_required
from django.core.exceptions import ValidationError
from django.http import Http404, HttpRequest, HttpResponse
from django.shortcuts import get_object_or_404, redirect, render
from django.urls import reverse
from django.utils.http import url_has_allowed_host_and_scheme
from django.views.decorators.http import require_POST

from items.models import Item
from orders.models import CartItem
from orders.services import (
    add_item_to_cart,
    format_currency,
    get_user_cart,
    remove_item_from_cart,
    update_cart_item_quantity,
)


def resolve_next_url(request: HttpRequest, fallback: str) -> str:
    next_url = request.POST.get("next") or fallback
    if not url_has_allowed_host_and_scheme(
        next_url,
        allowed_hosts={request.get_host()},
        require_https=request.is_secure(),
    ):
        return fallback
    return next_url


@login_required
def cart(request: HttpRequest) -> HttpResponse:
    cart_items: list[CartItem] = []
    total_quantity = 0
    total_amount = "0,00 руб."

    cart_obj = get_user_cart(request.user)
    if cart_obj:
        cart_items = list(
            cart_obj.items.select_related("item__category", "item__subcategory").prefetch_related("item__images")
        )
        total_quantity = sum(cart_item.quantity for cart_item in cart_items)
        total_amount_value = sum(
            (cart_item.item.price * cart_item.quantity for cart_item in cart_items),
            start=Decimal("0.00"),
        )
        total_amount = format_currency(total_amount_value)

    return render(request, "orders/cart.html", {
        "cart_items": cart_items,
        "total_quantity": total_quantity,
        "total_amount": total_amount,
    })


@login_required
@require_POST
def add(request: HttpRequest) -> HttpResponse:
    item = get_object_or_404(Item, pk=request.POST.get("item_id"))

    try:
        _, created = add_item_to_cart(request.user, item)
        if created:
            messages.success(request, f"Товар «{item.name}» добавлен в корзину.")
        else:
            messages.info(request, f"Товар «{item.name}» уже есть в корзине.")
    except ValidationError as error:
        messages.error(request, error.message)

    return redirect(resolve_next_url(request, reverse("orders:cart")))


@login_required
@require_POST
def remove(request: HttpRequest) -> HttpResponse:
    item = get_object_or_404(Item, pk=request.POST.get("item_id"))
    removed = remove_item_from_cart(request.user, item.id)

    if removed:
        messages.success(request, f"Товар «{item.name}» удалён из корзины.")
    else:
        messages.info(request, f"Товар «{item.name}» уже отсутствует в корзине.")

    return redirect(resolve_next_url(request, reverse("orders:cart")))


@login_required
@require_POST
def update_quantity(request: HttpRequest) -> HttpResponse:
    item = get_object_or_404(Item, pk=request.POST.get("item_id"))

    try:
        quantity = int(request.POST.get("quantity"))
        update_cart_item_quantity(request.user, item.id, quantity)
        messages.success(request, f"Количество товара «{item.name}» обновлено.")
    except (TypeError, ValueError):
        messages.error(request, "Некорректное количество товара.")
    except CartItem.DoesNotExist as error:
        raise Http404() from error
    except ValidationError as error:
        messages.error(request, error.message)

    return redirect(resolve_next_url(request, reverse("orders:cart")))