from django.utils.module_loading import import_string
from rest_framework import status, viewsets
from rest_framework.permissions import AllowAny, IsAuthenticated
from rest_framework.response import Response

from infrasynth.shared.settings_utils import get_setting

from .filters import (
    InboundEndpointFilter,
    InboundEventFilter,
    OutboundDeliveryFilter,
    OutboundEndpointFilter,
    OutboundSubscriptionFilter,
)
from .models import (
    InboundEndpoint,
    InboundEvent,
    OutboundDelivery,
    OutboundEndpoint,
    OutboundSubscription,
)
from .serializers import (
    InboundEndpointSerializer,
    InboundEventSerializer,
    InboundReceiveSerializer,
    OutboundDeliverySerializer,
    OutboundEndpointSerializer,
    OutboundSubscriptionSerializer,
)
from .signals import inbound_event_received


class OutboundEndpointViewSet(viewsets.ModelViewSet):
    queryset = OutboundEndpoint.objects.all()
    serializer_class = OutboundEndpointSerializer
    permission_classes = [IsAuthenticated]
    filterset_class = OutboundEndpointFilter
    search_fields = ["name"]

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


class OutboundSubscriptionViewSet(viewsets.ModelViewSet):
    queryset = OutboundSubscription.objects.select_related("endpoint").all()
    serializer_class = OutboundSubscriptionSerializer
    permission_classes = [IsAuthenticated]
    filterset_class = OutboundSubscriptionFilter
    search_fields = ["event_name"]

    def get_queryset(self):
        return OutboundSubscription.objects.select_related("endpoint").all()


class OutboundDeliveryViewSet(viewsets.ReadOnlyModelViewSet):
    queryset = OutboundDelivery.objects.select_related("subscription__endpoint").all()
    serializer_class = OutboundDeliverySerializer
    permission_classes = [IsAuthenticated]
    filterset_class = OutboundDeliveryFilter

    def get_queryset(self):
        return OutboundDelivery.objects.select_related("subscription__endpoint").all()


class InboundEndpointViewSet(viewsets.ModelViewSet):
    queryset = InboundEndpoint.objects.all()
    serializer_class = InboundEndpointSerializer
    permission_classes = [IsAuthenticated]
    filterset_class = InboundEndpointFilter
    search_fields = ["name", "slug"]

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


class InboundEventViewSet(viewsets.ReadOnlyModelViewSet):
    queryset = InboundEvent.objects.select_related("endpoint").all()
    serializer_class = InboundEventSerializer
    permission_classes = [IsAuthenticated]
    filterset_class = InboundEventFilter

    def get_queryset(self):
        return InboundEvent.objects.select_related("endpoint").all()


class InboundReceiveView(viewsets.ViewSet):
    permission_classes = [AllowAny]

    def create(self, request, slug=None):
        serializer = InboundReceiveSerializer(data=request.data)
        serializer.is_valid(raise_exception=True)

        # Unauthenticated inbound webhook: resolve the tenant from the
        # tenant-scoped credential (endpoint slug + verified signature), never
        # from the caller.
        endpoint = InboundEndpoint.all_objects.filter(slug=slug, is_active=True).first()
        if endpoint is None:
            return Response({"detail": "Endpoint not found"}, status=status.HTTP_404_NOT_FOUND)

        raw_body = request.body or b""
        max_bytes = int(get_setting("INFRASYNTH_WEBHOOKS", "MAX_PAYLOAD_SIZE_BYTES", 1048576))
        if len(raw_body) > max_bytes:
            return Response(
                {
                    "code": "VALIDATION_PAYLOAD_TOO_LARGE",
                    "message": "Webhook payload exceeds the size limit.",
                    "details": [],
                },
                status=status.HTTP_413_REQUEST_ENTITY_TOO_LARGE,
            )

        payload = serializer.validated_data["payload"]
        headers = serializer.validated_data["headers"]
        # Signature/event headers normally arrive as real HTTP headers; merge the
        # optional payload-level ``headers`` map on top (payload wins).
        normalized_headers = {str(k): str(v) for k, v in request.headers.items()}
        normalized_headers.update({str(k): str(v) for k, v in (headers or {}).items()})
        event_type = get_signal_header(normalized_headers, "X-Event-Type") or "unknown"
        external_id = get_signal_header(normalized_headers, "X-Event-Id") or ""

        try:
            handler = import_string(endpoint.handler)() if endpoint.handler else None
        except (ImportError, TypeError):
            handler = None

        verified = self._verify(endpoint, handler, payload, normalized_headers, raw_body)
        if not verified:
            return Response(
                {
                    "code": "AUTH_INVALID_SIGNATURE",
                    "message": "The webhook signature is missing or invalid.",
                    "details": [],
                },
                status=status.HTTP_401_UNAUTHORIZED,
            )

        from infrasynth.tenancy.context import tenant_context

        with tenant_context(endpoint.tenant):
            if external_id:
                existing = InboundEvent.all_objects.filter(endpoint=endpoint, external_id=external_id).first()
                if existing is not None:
                    data = InboundEventSerializer(existing).data
                    data = dict(data) if isinstance(data, dict) else data
                    return Response({**data, "duplicate": True}, status=status.HTTP_200_OK)

            event = InboundEvent.all_objects.create(
                tenant=endpoint.tenant,
                endpoint=endpoint,
                event_type=event_type,
                external_id=external_id,
                raw_payload=payload,
                is_verified=True,
            )

            backend = get_setting("INFRASYNTH_WEBHOOKS", "INBOUND_PROCESSING_BACKEND", "sync")
            from .dispatch import process_inbound_event

            if backend == "celery":
                process_inbound_event.delay(event.id, str(endpoint.tenant_id))
            else:
                process_inbound_event(event.id, str(endpoint.tenant_id))

            event.refresh_from_db()

        inbound_event_received.send(
            sender=InboundReceiveView,
            event=event,
            payload=payload,
            headers=normalized_headers,
        )

        return Response(
            InboundEventSerializer(event).data,
            status=status.HTTP_201_CREATED,
        )

    @staticmethod
    def _verify(endpoint, handler, payload, headers, raw_body) -> bool:
        if handler is not None:
            try:
                return bool(handler.verify(payload, headers, endpoint.secret, raw_body=raw_body))
            except TypeError:
                # Older handlers without the ``raw_body`` keyword.
                pass
        from .signature import verify_signature

        header_name = get_setting("INFRASYNTH_WEBHOOKS", "SIGNATURE_HEADER", "X-Webhook-Signature")
        signature = headers.get(header_name) or headers.get("X-Signature") or ""
        if not signature:
            return False
        tolerance = int(get_setting("INFRASYNTH_WEBHOOKS", "INBOUND_SIGNATURE_TOLERANCE_SECONDS", 300))
        return verify_signature(
            endpoint.secret,
            raw_body.decode("utf-8", errors="replace"),
            signature,
            tolerance_seconds=tolerance,
        )


def get_signal_header(headers: dict, name: str) -> str:
    """Case-insensitive header lookup that preserves the original casing."""
    lowered = name.lower()
    for key, value in headers.items():
        if key.lower() == lowered:
            return value
    return ""