scalesApp/backend/api/views.py

from rest_framework import viewsets, status, mixins
from rest_framework.decorators import action
from rest_framework.response import Response
from rest_framework.views import APIView
from rest_framework.permissions import IsAuthenticated, AllowAny
from .models import (ComPortReading, User, Report, ScaleProtocol, License,
                     StationSlot, generate_doc_number)
from .serializers import (
    ComPortReadingSerializer, UserSerializer, UserDetailSerializer,
    ChangePasswordSerializer, VehicleSerializer, NomenclatureSerializer,
    NomenclatureEntrySerializer, ReportSerializer, ExtraCombinationSerializer,
    ScaleProtocolSerializer,
)
from django.utils import timezone
from vehicles.models import Vehicle, ExtraCombination, combination_hash
from nomenclatures.models import Nomenclature, NomenclatureEntry
from scalesapp.sse import sse_broadcast_update
from . import licensing


class IsAdminUser(IsAuthenticated):
    def has_permission(self, request, view):
        return bool(request.user and request.user.is_authenticated and request.user.is_admin)


class UserViewSet(viewsets.ModelViewSet):
    """
    API endpoint for user management.

    list: Get all users
    create: Create a new user
    retrieve: Get a specific user
    update: Update a user
    destroy: Soft-delete a user (sets is_active=False)
    me: Get current authenticated user
    change_password: Change password for current user
    """
    queryset = User.objects.all()
    serializer_class = UserSerializer
    filterset_fields = ['role', 'is_admin', 'is_active']
    ordering = ['username']

    def get_permissions(self):
        if self.action in ('me', 'change_password'):
            return [IsAuthenticated()]
        return [IsAuthenticated(), IsAdminUser()]

    def destroy(self, request, *args, **kwargs):
        instance = self.get_object()
        instance.is_active = False
        instance.save()
        return Response(status=status.HTTP_204_NO_CONTENT)

    @action(detail=False, methods=['get'])
    def me(self, request):
        """Get current authenticated user details"""
        serializer = UserDetailSerializer(request.user)
        return Response(serializer.data)

    @action(detail=False, methods=['post'],
            url_path='change-password', url_name='change_password')
    def change_password(self, request):
        """Change password for current user"""
        serializer = ChangePasswordSerializer(
            data=request.data,
            context={'request': request}
        )
        if serializer.is_valid():
            serializer.save()
            return Response({
                'detail': 'Password updated successfully'
            }, status=status.HTTP_200_OK)
        return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)


class ComPortReadingViewSet(viewsets.ModelViewSet):
    """
    API endpoint for COM port readings.

    list: Get all readings with optional filtering
    create: Create a new reading (allows unauthenticated for serial bridge)
    retrieve: Get a specific reading
    destroy: Delete a reading
    latest: Get the latest reading
    by_port: Get readings for a specific port
    """
    queryset = ComPortReading.objects.all()
    serializer_class = ComPortReadingSerializer
    filterset_fields = ['port']
    ordering = ['-timestamp']

    def get_permissions(self):
        """Allow unauthenticated POST for serial bridge"""
        if self.action == 'create':
            return [AllowAny()]
        return [IsAuthenticated()]

    @action(detail=False, methods=['get'])
    def latest(self, request):
        """Get the latest reading"""
        reading = ComPortReading.objects.first()
        if reading:
            serializer = self.get_serializer(reading)
            return Response(serializer.data)
        return Response({'detail': 'No readings yet'}, status=status.HTTP_404_NOT_FOUND)

    @action(detail=False, methods=['get'])
    def by_port(self, request):
        """Get readings for a specific port"""
        port = request.query_params.get('port', None)
        if not port:
            return Response(
                {'detail': 'port parameter is required'},
                status=status.HTTP_400_BAD_REQUEST
            )
        readings = ComPortReading.objects.filter(port=port)
        serializer = self.get_serializer(readings, many=True)
        return Response(serializer.data)

    def get_client_ip(self, request):
        """Get client IP address"""
        x_forwarded_for = request.META.get('HTTP_X_FORWARDED_FOR')
        if x_forwarded_for:
            ip = x_forwarded_for.split(',')[0]
        else:
            ip = request.META.get('REMOTE_ADDR')
        return ip

    def perform_create(self, serializer):
        """Save the reading with client IP"""
        serializer.save(source_ip=self.get_client_ip(self.request))


def _maybe_finalize(vehicle, user):
    """If both tare and gross are set and net hasn't been calculated yet, compute net and assign doc_number."""
    if vehicle.tare is not None and vehicle.gross is not None and vehicle.net is None:
        vehicle.net = vehicle.gross - vehicle.tare
        vehicle.net_date = timezone.now()
        vehicle.net_user = user
        vehicle.doc_number = generate_doc_number(timezone.now().year)
        vehicle.save()


def _assign_weighing(vehicle, value, user, manual=False, note=None):
    """Record a weighing. Assigns by weight: lighter becomes tare, heavier becomes gross.

    The first weighing is parked in tare; the second may push it to gross if the new
    reading is lighter, since trucks may arrive either empty (inbound) or loaded (outbound).
    """
    now = timezone.now()

    def apply(prefix):
        setattr(vehicle, prefix, value)
        setattr(vehicle, f'{prefix}_date', now)
        setattr(vehicle, f'{prefix}_user', user)
        setattr(vehicle, f'{prefix}_manual', manual)
        setattr(vehicle, f'{prefix}_manual_user', user if manual else None)
        setattr(vehicle, f'{prefix}_manual_date', now if manual else None)
        setattr(vehicle, f'{prefix}_manual_note', note if manual else None)

    def move(src_prefix, dst_prefix):
        """Move a recorded weighing to the other slot, carrying all its provenance."""
        for suffix in ('', '_date', '_user', '_manual', '_manual_user', '_manual_date', '_manual_note'):
            setattr(vehicle, f'{dst_prefix}{suffix}', getattr(vehicle, f'{src_prefix}{suffix}'))

    if vehicle.tare is not None and vehicle.gross is not None:
        raise ValueError('Vehicle already has both weights.')

    if vehicle.tare is None and vehicle.gross is None:
        apply('tare')
    elif vehicle.gross is None:
        # tare holds the first weighing - keep the lighter one as tare
        if value >= vehicle.tare:
            apply('gross')
        else:
            move('tare', 'gross')
            apply('tare')
    else:
        # gross set but tare empty (only reachable via direct API use)
        if value <= vehicle.gross:
            apply('tare')
        else:
            move('gross', 'tare')
            apply('gross')

    vehicle.save()
    _maybe_finalize(vehicle, user)


def _record_extra_combination(extra_data):
    """Record the lookup/selector projection of a vehicle's extra data as a reusable combination.

    The selector value is part of the combination: without it, "Ship + Varna Star"
    and "Warehouse + WH-3" would collapse into indistinguishable rows.
    """
    if not extra_data:
        return

    lookup_codes = set(
        Nomenclature.objects.filter(
            applies_to='vehicle',
            kind__in=[Nomenclature.LOOKUP, Nomenclature.SELECTOR],
        )
        .values_list('code', flat=True)
    )
    combo = {k: v for k, v in extra_data.items() if k in lookup_codes and v is not None}
    if not combo:
        return

    existing, created = ExtraCombination.objects.get_or_create(
        data_hash=combination_hash(combo), defaults={'data': combo}
    )
    if not created:
        existing.use_count += 1
        existing.last_used = timezone.now()
        existing.save()

    action = 'created' if created else 'updated'
    sse_broadcast_update('extra_combination', action, ExtraCombinationSerializer(existing).data)


class VehicleViewSet(viewsets.ModelViewSet):
    """
    API endpoint for vehicle management.

    list: Get all vehicles with pagination
    create: Create a new vehicle with optional extra data
    retrieve: Get a specific vehicle by ID
    update: Full update of vehicle and extra data
    partial_update: Partial update of vehicle
    destroy: Delete a vehicle (cascades to VehicleExtra)
    by_number: Get vehicle by vehicle_number
    measure: Record a weighing (app assigns tare vs gross by weight)
    """
    queryset = Vehicle.objects.select_related('extra', 'tare_user', 'gross_user').all()
    serializer_class = VehicleSerializer
    permission_classes = [IsAuthenticated]
    filterset_fields = ['vehicle_number']
    search_fields = ['vehicle_number']
    ordering = ['vehicle_number']

    def perform_create(self, serializer):
        instance = serializer.save()
        data = VehicleSerializer(instance).data
        sse_broadcast_update('vehicle', 'created', data)
        _record_extra_combination(instance.extra.data if hasattr(instance, 'extra') else None)

    def perform_update(self, serializer):
        instance = serializer.save()
        data = VehicleSerializer(instance).data
        sse_broadcast_update('vehicle', 'updated', data)
        _record_extra_combination(instance.extra.data if hasattr(instance, 'extra') else None)

    def perform_destroy(self, instance):
        data = VehicleSerializer(instance).data
        instance.delete()
        sse_broadcast_update('vehicle', 'deleted', data)

    @action(detail=False, methods=['get'], url_path='by-number')
    def by_number(self, request):
        """Get vehicle by vehicle_number query parameter"""
        vehicle_number = request.query_params.get('vehicle_number', None)
        if not vehicle_number:
            return Response(
                {'detail': 'vehicle_number parameter is required'},
                status=status.HTTP_400_BAD_REQUEST
            )

        try:
            vehicle = Vehicle.objects.get(vehicle_number=vehicle_number)
            serializer = self.get_serializer(vehicle)
            return Response(serializer.data)
        except Vehicle.DoesNotExist:
            return Response(
                {'detail': 'Vehicle not found'},
                status=status.HTTP_404_NOT_FOUND
            )

    @action(detail=True, methods=['post'], url_path='measure')
    def measure(self, request, pk=None):
        """Record a weighing. The app assigns tare vs gross by weight."""
        if not request.user.can_measure:
            return Response({'detail': 'You do not have permission to measure.'},
                            status=status.HTTP_403_FORBIDDEN)

        # Licence enforcement. The UI also disables the button, but this is the
        # actual rule - the button state is only a convenience.
        station_key = (request.data.get('station_key') or '').strip()
        if not _station_allowed(station_key):
            limit = licensing.effective_station_limit()
            return Response(
                {'detail': f'This station is not licensed to measure '
                           f'(limit: {limit} stations).'},
                status=status.HTTP_403_FORBIDDEN)

        manual = bool(request.data.get('manual', False))
        if manual and not request.user.can_manually_measure:
            return Response({'detail': 'You do not have permission to measure manually.'},
                            status=status.HTTP_403_FORBIDDEN)

        note = (request.data.get('note') or '').strip()
        if manual and not note:
            return Response({'detail': 'A note is required for a manual measurement.'},
                            status=status.HTTP_400_BAD_REQUEST)

        value = request.data.get('value')
        if value is None:
            return Response({'detail': 'value is required'}, status=status.HTTP_400_BAD_REQUEST)
        try:
            value = int(value)
        except (ValueError, TypeError):
            return Response({'detail': 'value must be a number'}, status=status.HTTP_400_BAD_REQUEST)

        vehicle = self.get_object()
        try:
            _assign_weighing(vehicle, value, request.user, manual=manual, note=note or None)
        except ValueError as exc:
            return Response({'detail': str(exc)}, status=status.HTTP_400_BAD_REQUEST)

        serializer = self.get_serializer(vehicle)
        sse_broadcast_update('vehicle', 'updated', serializer.data)
        return Response(serializer.data)


class ExtraCombinationViewSet(mixins.ListModelMixin,
                              mixins.RetrieveModelMixin,
                              mixins.DestroyModelMixin,
                              viewsets.GenericViewSet):
    """
    API endpoint for previously-used combinations of vehicle extra (lookup) data.

    list: Get all combinations, most recently used first
    retrieve: Get a specific combination
    destroy: Delete a combination the user no longer needs

    Rows are created/bumped automatically when a vehicle's extra data is saved.
    """
    queryset = ExtraCombination.objects.all()
    serializer_class = ExtraCombinationSerializer
    permission_classes = [IsAuthenticated]
    ordering = ['-last_used']

    def perform_destroy(self, instance):
        data = ExtraCombinationSerializer(instance).data
        instance.delete()
        sse_broadcast_update('extra_combination', 'deleted', data)


def _live_slots():
    return StationSlot.objects.filter(last_seen__gte=licensing.live_slot_cutoff())


def _station_allowed(station_key):
    """Whether this station may measure.

    A station already holding a live slot is always allowed - including when the
    licence is full - so a brief disconnection does not lock a working station
    out behind its own expiring slot.
    """
    if not station_key:
        return False
    if _live_slots().filter(station_key=station_key).exists():
        return True
    return _live_slots().count() < licensing.effective_station_limit()


class LicenseView(APIView):
    """Licence status, and installing a new licence key."""
    permission_classes = [IsAuthenticated]

    def get(self, request):
        status_info = licensing.license_status()
        slots = _live_slots()
        payload = {
            **status_info,
            'stations_used': slots.count(),
            'components': licensing.machine_components(),
        }
        if request.user.is_admin:
            payload['slots'] = [
                {'station_key': s.station_key, 'com_port': s.com_port,
                 'bridge_version': s.bridge_version, 'last_seen': s.last_seen}
                for s in slots
            ]
        return Response(payload)

    def post(self, request):
        if not request.user.is_admin:
            return Response({'detail': 'Only administrators can install a licence.'},
                            status=status.HTTP_403_FORBIDDEN)

        blob = (request.data.get('key_blob') or '').strip()
        if not blob:
            return Response({'detail': 'key_blob is required'},
                            status=status.HTTP_400_BAD_REQUEST)

        # Validate before storing, so a bad paste cannot displace a working licence.
        valid, payload, reason = licensing.verify_license(blob)
        if not valid:
            return Response({'detail': reason}, status=status.HTTP_400_BAD_REQUEST)

        record = License.objects.first() or License()
        record.key_blob = blob
        record.grace_started = None
        record.save()

        return Response(licensing.license_status())


class LicenseHeartbeatView(APIView):
    """Stations report in here so the server can count them.

    The bridge deliberately does not talk to Django - the browser, which already
    talks to both, reports which bridge it is using. That keeps the bridge pure
    transport with no startup dependency on the server.
    """
    permission_classes = [IsAuthenticated]

    def post(self, request):
        station_key = (request.data.get('station_key') or '').strip()
        if not station_key:
            return Response({'detail': 'station_key is required'},
                            status=status.HTTP_400_BAD_REQUEST)

        limit = licensing.effective_station_limit()
        existing = StationSlot.objects.filter(station_key=station_key).first()
        live = _live_slots()

        if existing is None and live.count() >= limit:
            return Response({
                'allowed': False,
                'stations_used': live.count(),
                'stations_licensed': limit,
                'detail': f'Licence limit reached ({limit} stations)',
            }, status=status.HTTP_403_FORBIDDEN)

        slot, _ = StationSlot.objects.update_or_create(
            station_key=station_key,
            defaults={
                'bridge_version': request.data.get('bridge_version', '') or '',
                'com_port': request.data.get('com_port', '') or '',
            },
        )
        # update_or_create does not touch auto_now when nothing changed
        slot.save(update_fields=['last_seen'])

        return Response({
            'allowed': True,
            'stations_used': _live_slots().count(),
            'stations_licensed': limit,
        })


class ScaleProtocolViewSet(viewsets.ModelViewSet):
    """
    API endpoint for scale protocol definitions.

    The frontend caches these and uses them to parse raw serial lines, so adding
    a scale type needs no change to the serial bridge running on station PCs.
    Built-in protocols cannot be deleted.
    """
    queryset = ScaleProtocol.objects.all()
    serializer_class = ScaleProtocolSerializer
    permission_classes = [IsAuthenticated]
    search_fields = ['name']
    ordering = ['name']

    def perform_create(self, serializer):
        instance = serializer.save()
        sse_broadcast_update('scale_protocol', 'created', ScaleProtocolSerializer(instance).data)

    def perform_update(self, serializer):
        instance = serializer.save()
        sse_broadcast_update('scale_protocol', 'updated', ScaleProtocolSerializer(instance).data)

    def destroy(self, request, *args, **kwargs):
        instance = self.get_object()
        if instance.is_builtin:
            return Response({'detail': 'Built-in protocols cannot be deleted.'},
                            status=status.HTTP_400_BAD_REQUEST)
        data = ScaleProtocolSerializer(instance).data
        instance.delete()
        sse_broadcast_update('scale_protocol', 'deleted', data)
        return Response(status=status.HTTP_204_NO_CONTENT)


class NomenclatureViewSet(viewsets.ModelViewSet):
    """
    API endpoint for nomenclature management.

    list: Get all nomenclatures with pagination
    create: Create a new nomenclature with fields
    retrieve: Get a specific nomenclature by ID
    update: Full update of nomenclature and fields
    partial_update: Partial update of nomenclature
    destroy: Delete a nomenclature (cascades to fields and entries)
    by_code: Get nomenclature by code
    by_applies_to: Filter nomenclatures by applies_to type
    entries: List or create entries for a specific nomenclature
    """
    queryset = Nomenclature.objects.prefetch_related('fields').all()
    serializer_class = NomenclatureSerializer
    permission_classes = [IsAuthenticated]
    filterset_fields = ['applies_to', 'code', 'kind']
    search_fields = ['code', 'name']
    ordering = ['sort_order', 'code']

    def perform_create(self, serializer):
        instance = serializer.save()
        sse_broadcast_update('nomenclature', 'insert', NomenclatureSerializer(instance).data)

    def perform_update(self, serializer):
        instance = serializer.save()
        sse_broadcast_update('nomenclature', 'update', NomenclatureSerializer(instance).data)

    def perform_destroy(self, instance):
        data = NomenclatureSerializer(instance).data
        instance.delete()
        sse_broadcast_update('nomenclature', 'delete', data)

    @action(detail=False, methods=['get'], url_path='by-code')
    def by_code(self, request):
        """Get nomenclature by code query parameter"""
        code = request.query_params.get('code', None)
        if not code:
            return Response(
                {'detail': 'code parameter is required'},
                status=status.HTTP_400_BAD_REQUEST
            )

        try:
            nomenclature = Nomenclature.objects.get(code=code)
            serializer = self.get_serializer(nomenclature)
            return Response(serializer.data)
        except Nomenclature.DoesNotExist:
            return Response(
                {'detail': 'Nomenclature not found'},
                status=status.HTTP_404_NOT_FOUND
            )

    @action(detail=False, methods=['get'], url_path='by-applies-to')
    def by_applies_to(self, request):
        """Get nomenclatures filtered by applies_to query parameter"""
        applies_to = request.query_params.get('applies_to', None)
        if not applies_to:
            return Response(
                {'detail': 'applies_to parameter is required'},
                status=status.HTTP_400_BAD_REQUEST
            )

        if applies_to not in ['vehicle', 'container']:
            return Response(
                {'detail': 'applies_to must be either vehicle or container'},
                status=status.HTTP_400_BAD_REQUEST
            )

        nomenclatures = Nomenclature.objects.filter(applies_to=applies_to)
        page = self.paginate_queryset(nomenclatures)
        if page is not None:
            serializer = self.get_serializer(page, many=True)
            return self.get_paginated_response(serializer.data)

        serializer = self.get_serializer(nomenclatures, many=True)
        return Response(serializer.data)

    @action(detail=True, methods=['get', 'post'], url_path='entries')
    def entries(self, request, pk=None):
        """List or create entries for a specific nomenclature."""
        nomenclature = self.get_object()

        if request.method == 'GET':
            entries = nomenclature.entries.all()
            is_active = request.query_params.get('is_active')
            if is_active is not None:
                entries = entries.filter(is_active=is_active.lower() == 'true')
            serializer = NomenclatureEntrySerializer(entries, many=True)
            return Response(serializer.data)

        serializer = NomenclatureEntrySerializer(
            data=request.data,
            context={'nomenclature': nomenclature},
        )
        serializer.is_valid(raise_exception=True)
        serializer.save(nomenclature=nomenclature)
        entry_data = {**serializer.data, 'nomenclature_code': nomenclature.code}
        sse_broadcast_update('nomenclature_entry', 'insert', entry_data)
        return Response(serializer.data, status=status.HTTP_201_CREATED)


class NomenclatureEntryViewSet(viewsets.ModelViewSet):
    """
    API endpoint for individual nomenclature entry management.
    For list/create use the nested endpoint: /api/nomenclatures/{id}/entries/
    This viewset handles retrieve/update/delete of individual entries.
    """
    queryset = NomenclatureEntry.objects.select_related('nomenclature').all()
    serializer_class = NomenclatureEntrySerializer
    permission_classes = [IsAuthenticated]

    def get_serializer_context(self):
        context = super().get_serializer_context()
        if self.kwargs.get('pk'):
            try:
                entry = NomenclatureEntry.objects.select_related('nomenclature').get(pk=self.kwargs['pk'])
                context['nomenclature'] = entry.nomenclature
            except NomenclatureEntry.DoesNotExist:
                pass
        return context

    def perform_update(self, serializer):
        instance = serializer.save()
        entry_data = {**NomenclatureEntrySerializer(instance).data, 'nomenclature_code': instance.nomenclature.code}
        sse_broadcast_update('nomenclature_entry', 'update', entry_data)

    def perform_destroy(self, instance):
        entry_data = {**NomenclatureEntrySerializer(instance).data, 'nomenclature_code': instance.nomenclature.code}
        instance.delete()
        sse_broadcast_update('nomenclature_entry', 'delete', entry_data)


class ReportViewSet(viewsets.ModelViewSet):
    """
    API endpoint for report template management.

    list: Get all reports
    create: Create a new report
    retrieve: Get a specific report by ID
    update: Update a report
    destroy: Delete a report
    """
    queryset = Report.objects.select_related('created_by').all()
    serializer_class = ReportSerializer
    permission_classes = [IsAuthenticated]
    filterset_fields = ['name', 'kind']
    search_fields = ['name']
    ordering = ['-updated_at']

    def perform_create(self, serializer):
        serializer.save(created_by=self.request.user)

    def perform_update(self, serializer):
        serializer.save()