from django.http import Http404
from rest_framework import mixins, status, viewsets
from rest_framework.decorators import action
from rest_framework.permissions import AllowAny
from rest_framework.response import Response

from infrasynth.api.idempotency import idempotent
from infrasynth.features.services import FeatureService
from infrasynth.security.permissions import IsAuthenticatedAndPermitted
from infrasynth.shared.exceptions import NotFoundError, ValidationAppError
from infrasynth.tenancy.context import get_current_tenant

from .filters import (
    AppFilter,
    EntitlementFilter,
    InvoiceFilter,
    PaymentGatewayFilter,
    PaymentTransactionFilter,
    PlanFilter,
    SubscriptionFilter,
)
from .models import (
    App,
    Entitlement,
    Invoice,
    PaymentGateway,
    PaymentTransaction,
    Plan,
    Subscription,
)
from .serializers import (
    AppSerializer,
    CheckoutSerializer,
    EntitlementSerializer,
    InvoiceSerializer,
    PaymentGatewaySerializer,
    PaymentTransactionSerializer,
    PlanSerializer,
    SubscribeSerializer,
    SubscriptionSerializer,
)


class _BillingFeatureMixin:
    def initial(self, request, *args, **kwargs):
        if not FeatureService().is_enabled("billing", user=getattr(request, "user", None)):
            raise Http404()
        super().initial(request, *args, **kwargs)


class PaymentGatewayViewSet(_BillingFeatureMixin, viewsets.ModelViewSet):
    queryset = PaymentGateway.objects.all()
    serializer_class = PaymentGatewaySerializer
    permission_classes = [IsAuthenticatedAndPermitted]
    filterset_class = PaymentGatewayFilter

    def get_queryset(self):
        return PaymentGateway.objects.all()


class AppViewSet(mixins.ListModelMixin, mixins.RetrieveModelMixin, viewsets.GenericViewSet):
    queryset = App.objects.filter(is_active=True)
    serializer_class = AppSerializer
    filterset_class = AppFilter
    permission_classes = [AllowAny]

    def get_queryset(self):
        return App.objects.filter(is_active=True).order_by("slug")


class PlanViewSet(mixins.ListModelMixin, mixins.RetrieveModelMixin, viewsets.GenericViewSet):
    queryset = Plan.objects.filter(is_active=True)
    serializer_class = PlanSerializer
    filterset_class = PlanFilter
    permission_classes = [AllowAny]
    lookup_field = "slug"

    def get_queryset(self):
        return Plan.objects.filter(is_active=True).select_related("app", "gateway").order_by("app__slug", "slug")


class EntitlementViewSet(mixins.ListModelMixin, mixins.RetrieveModelMixin, viewsets.GenericViewSet):
    serializer_class = EntitlementSerializer
    permission_classes = [IsAuthenticatedAndPermitted]
    filterset_class = EntitlementFilter

    def get_queryset(self):
        # Entitlement.objects is tenant-scoped by TenantManager (fail closed).
        return Entitlement.objects.select_related("app", "plan").order_by("app__slug")

    @action(detail=False, methods=["get"], url_path=r"by-app/(?P<app_slug>[^/.]+)")
    def by_app(self, request, app_slug=None):
        entitlement = Entitlement.objects.filter(app__slug=app_slug).select_related("app", "plan").first()
        if entitlement is None:
            raise NotFoundError("No entitlement for this app.")
        return Response(EntitlementSerializer(entitlement).data)


class SubscriptionViewSet(_BillingFeatureMixin, viewsets.ModelViewSet):
    serializer_class = SubscriptionSerializer
    permission_classes = [IsAuthenticatedAndPermitted]
    filterset_class = SubscriptionFilter

    def get_queryset(self):
        return Subscription.objects.select_related("plan", "plan__app", "gateway", "entitlement").order_by("-id")

    @action(detail=False, methods=["post"])
    @idempotent
    def checkout(self, request):
        ser = CheckoutSerializer(data=request.data)
        ser.is_valid(raise_exception=True)
        tenant = get_current_tenant()
        plan = (
            Plan.objects.filter(app__slug=ser.validated_data["app"], slug=ser.validated_data["plan"], is_active=True)
            .select_related("gateway", "app")
            .first()
        )
        if plan is None:
            raise NotFoundError("Plan not found.")
        from .services import BillingService

        try:
            result, gateway = BillingService().create_checkout_session(
                plan,
                tenant,
                request.user,
                success_url=ser.validated_data.get("success_url"),
                cancel_url=ser.validated_data.get("cancel_url"),
            )
        except ValueError as exc:
            raise ValidationAppError(str(exc), code="VALIDATION_CHECKOUT_FAILED") from exc
        return Response(
            {
                "checkout_url": result.checkout_url,
                "session_id": result.session_id,
                "client_secret": result.client_secret,
                "gateway": gateway.slug,
                "plan_slug": plan.slug,
                "app_slug": plan.app.slug,
            }
        )

    @action(detail=False, methods=["post"])
    def subscribe(self, request):
        ser = SubscribeSerializer(data=request.data)
        ser.is_valid(raise_exception=True)
        tenant = get_current_tenant()
        plan = (
            Plan.objects.filter(slug=ser.validated_data["plan_slug"], is_active=True).select_related("gateway").first()
        )
        if plan is None:
            raise NotFoundError("Plan not found.")
        from .services import BillingService

        try:
            result, gateway = BillingService().create_checkout_session(
                plan,
                tenant,
                request.user,
                success_url=ser.validated_data.get("success_url"),
                cancel_url=ser.validated_data.get("cancel_url"),
            )
        except ValueError as exc:
            raise ValidationAppError(str(exc), code="VALIDATION_CHECKOUT_FAILED") from exc
        return Response(
            {
                "checkout_url": result.checkout_url,
                "session_id": result.session_id,
                "client_secret": result.client_secret,
                "gateway": gateway.slug,
                "plan_slug": plan.slug,
            }
        )

    @action(detail=True, methods=["post"])
    def cancel(self, request, pk=None):
        subscription = self.get_object()
        from .services import BillingService

        BillingService().cancel_subscription(subscription)
        return Response(SubscriptionSerializer(subscription).data)


class InvoiceViewSet(_BillingFeatureMixin, viewsets.ModelViewSet):
    serializer_class = InvoiceSerializer
    permission_classes = [IsAuthenticatedAndPermitted]
    filterset_class = InvoiceFilter

    def get_queryset(self):
        return Invoice.objects.select_related("subscription", "gateway", "pdf_file").order_by("-id")


class PaymentTransactionViewSet(_BillingFeatureMixin, viewsets.ReadOnlyModelViewSet):
    serializer_class = PaymentTransactionSerializer
    permission_classes = [IsAuthenticatedAndPermitted]
    filterset_class = PaymentTransactionFilter

    def get_queryset(self):
        return PaymentTransaction.objects.select_related("invoice", "gateway").order_by("-id")


class WebhookViewSet(viewsets.GenericViewSet):
    permission_classes = [AllowAny]

    @action(detail=False, methods=["post"])
    def receive(self, request, provider=None):
        from django.utils.module_loading import import_string

        from infrasynth.api.webhooks import assert_fresh_webhook
        from infrasynth.shared.settings_utils import get_setting

        gateway_slug = provider or request.data.get("gateway_slug") or request.query_params.get("gateway_slug")
        gateway = (
            PaymentGateway.objects.filter(slug=gateway_slug, is_active=True).first()
            if gateway_slug
            else PaymentGateway.objects.filter(is_active=True).first()
        )
        if gateway is None:
            return Response({"detail": "No active payment gateway found."}, status=status.HTTP_404_NOT_FOUND)

        # Replay protection (API-STANDARD §10): reject events older than 5 min.
        tolerance = int(get_setting("INFRASYNTH_BILLING", "WEBHOOK_TOLERANCE_SECONDS", 300))
        timestamp = (
            request.data.get("created") or request.data.get("timestamp") or request.headers.get("X-Webhook-Timestamp")
        )
        if timestamp is not None:
            try:
                assert_fresh_webhook(timestamp, tolerance_seconds=tolerance)
            except Exception as exc:  # noqa: BLE001
                raise ValidationAppError(str(exc), code="VALIDATION_WEBHOOK_STALE") from exc

        try:
            gateway_cls = import_string(gateway.gateway_class)
            gateway_instance = gateway_cls(gateway.config)
            result = gateway_instance.handle_webhook(payload=request.data, headers=dict(request.headers))
        except Exception as exc:  # noqa: BLE001
            raise ValidationAppError(f"Webhook processing failed: {exc}", code="VALIDATION_WEBHOOK_FAILED") from exc

        if not result.is_handled:
            return Response({"status": "ignored", "event_type": result.event_type})

        payload = result.data if isinstance(result.data, dict) else {}
        event_id = str(request.data.get("id") or request.headers.get("X-Event-Id") or "") or None
        from .services import BillingService

        outcome = BillingService().process_webhook_event(
            gateway,
            result.event_type,
            payload,
            event_id=event_id,
        )
        return Response(
            {
                "status": "processed",
                "event_type": result.event_type,
                "billing": outcome,
            }
        )