from django.conf import settings
from django.db import transaction
from django.db.models import Q
from django.utils import timezone
from rest_framework import decorators, mixins, response, status, viewsets

from apps.core.errors import error_response
from apps.payments.gateways import get_gateway
from apps.payments.models import Payment
from apps.payments.serializers import PaymentSerializer
from apps.rbac.permissions import ActionPermission


class PaymentViewSet(
    mixins.ListModelMixin, mixins.RetrieveModelMixin, mixins.CreateModelMixin, viewsets.GenericViewSet
):
    serializer_class = PaymentSerializer
    permission_classes = [ActionPermission]
    code_map = {
        "list": "invoice.view",
        "retrieve": "invoice.view",
        "create": "reservation.create",
        "verify": "invoice.create",
    }

    def get_queryset(self):
        user = self.request.user
        qs = Payment.objects.select_related("order", "reservation").all()
        if user.is_superuser:
            return qs
        return qs.filter(Q(order__customer__user=user) | Q(reservation__customer__user=user))

    def create(self, request, *args, **kwargs):
        serializer = self.get_serializer(data=request.data)
        serializer.is_valid(raise_exception=True)
        order = serializer.validated_data.get("order")
        reservation = serializer.validated_data.get("reservation")
        if not order and not reservation:
            return response.Response(
                error_response("PAYMENT_TARGET_REQUIRED", "An order or reservation is required."),
                status=status.HTTP_400_BAD_REQUEST,
            )
        amount = serializer.validated_data["amount"]
        currency = order.currency if order else getattr(settings, "BASE_CURRENCY", "IRR")
        reference = order.order_number if order else f"RES-{str(reservation.id)[:8]}"

        gateway = get_gateway()
        callback_url = request.build_absolute_uri("/api/v1/payments/callback/")
        result = gateway.request_payment(str(amount), currency, reference, callback_url)
        payment = Payment.objects.create(
            order=order,
            reservation=reservation,
            amount=amount,
            currency=currency,
            gateway=settings.PAYMENT_GATEWAY_PROVIDER or "mock",
            authority=result["authority"],
            status=Payment.Status.PENDING,
            request_time=timezone.now(),
        )
        return response.Response(
            {"id": str(payment.id), "authority": result["authority"], "redirect_url": result["redirect_url"]},
            status=status.HTTP_201_CREATED,
        )

    @decorators.action(detail=True, methods=["post"])
    @transaction.atomic
    def verify(self, request, pk=None):
        payment = Payment.objects.select_for_update().get(pk=pk)
        # Idempotent: a duplicate callback must not create a duplicate success.
        if payment.status == Payment.Status.SUCCESS:
            return response.Response(PaymentSerializer(payment).data)
        gateway = get_gateway()
        result = gateway.verify(payment.authority, str(payment.amount))
        payment.verification_time = timezone.now()
        if result.get("status") == "success":
            payment.status = Payment.Status.SUCCESS
            payment.transaction_id = result["transaction_id"]
        else:
            payment.status = Payment.Status.FAILED
            payment.error = result.get("error", "")
        payment.save()
        return response.Response(PaymentSerializer(payment).data)