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.forms import CheckoutForm
from orders.models import CartItem, Order
from orders.services import (
    add_item_to_cart,
    calculate_checkout_totals,
    create_order_from_cart,
    format_currency,
    get_user_cart_items,
    remove_item_from_cart,
    send_order_confirmation_email,
    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 = get_user_cart_items(request.user)
    total_quantity = sum(cart_item.quantity for cart_item in cart_items)
    totals = calculate_checkout_totals(cart_items, Order.DeliveryMethod.COURIER)
    form = CheckoutForm(initial={
        "customer_name": request.user.get_full_name() or request.user.get_username(),
        "email": request.user.email,
    })

    return render(request, "orders/cart.html", {
        "cart_items": cart_items,
        "checkout_form": form,
        "total_quantity": total_quantity,
        "products_total_value": totals["products_total"],
        "products_total": format_currency(totals["products_total"]),
        "discount_total": format_currency(totals["discount_total"]),
        "delivery_total": format_currency(totals["delivery_total"]),
        "floor_lift_total": format_currency(totals["floor_lift_total"]),
        "total_amount": format_currency(totals["total"]),
    })


@login_required
@require_POST
def checkout(request: HttpRequest) -> HttpResponse:
    cart_items = get_user_cart_items(request.user)
    if not cart_items:
        messages.error(request, "Корзина пуста. Добавьте товары перед оформлением заказа.")
        return redirect("orders:cart")

    form = CheckoutForm(request.POST)
    if not form.is_valid():
        total_quantity = sum(cart_item.quantity for cart_item in cart_items)
        delivery_method = request.POST.get("delivery_method") or Order.DeliveryMethod.COURIER
        totals = calculate_checkout_totals(cart_items, delivery_method)
        return render(request, "orders/cart.html", {
            "cart_items": cart_items,
            "checkout_form": form,
            "total_quantity": total_quantity,
            "products_total_value": totals["products_total"],
            "products_total": format_currency(totals["products_total"]),
            "discount_total": format_currency(totals["discount_total"]),
            "delivery_total": format_currency(totals["delivery_total"]),
            "floor_lift_total": format_currency(totals["floor_lift_total"]),
            "total_amount": format_currency(totals["total"]),
        }, status=400)

    try:
        order = create_order_from_cart(request.user, form.cleaned_data)
    except ValidationError as error:
        messages.error(request, error.message)
        return redirect("orders:cart")

    try:
        send_order_confirmation_email(order)
    except Exception:
        messages.error(request, "Заказ создан, но письмо с деталями не удалось отправить. Мы свяжемся с вами.")
    else:
        messages.success(request, "Оплата прошла успешно. Детали заказа отправлены на почту.")

    return redirect("orders:success", order_id=order.id)


@login_required
def success(request: HttpRequest, order_id: int) -> HttpResponse:
    order = get_object_or_404(
        Order.objects.prefetch_related("items"),
        pk=order_id,
        user=request.user,
    )
    return render(request, "orders/success.html", {"order": order})


@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")))