from django.db import transaction
from rest_framework import status, viewsets
from rest_framework.decorators import api_view, permission_classes
from rest_framework.response import Response
from rest_framework.views import APIView

from .models import (
    Account,
    CompanySettings,
    Employee,
    Invoice,
    Party,
    PartyAdjustment,
    Payslip,
    Product,
    SalesType,
    TreasuryTxn,
    Voucher,
)
from .permissions import IsAdminAccount
from .seeding import seed_default_data
from .serializers import (
    AccountSerializer,
    CompanySettingsSerializer,
    EmployeeSerializer,
    InvoiceSerializer,
    PartyAdjustmentSerializer,
    PartySerializer,
    PayslipSerializer,
    ProductSerializer,
    SalesTypeSerializer,
    TreasuryTxnSerializer,
    VoucherSerializer,
)


class _AdminModelViewSet(viewsets.ModelViewSet):
    """Base viewset restricting access to admin accounts."""

    permission_classes = [IsAdminAccount]


class AccountViewSet(_AdminModelViewSet):
    queryset = Account.objects.all()
    serializer_class = AccountSerializer
    pagination_class = None


class PartyViewSet(_AdminModelViewSet):
    queryset = Party.objects.all()
    serializer_class = PartySerializer
    pagination_class = None


class ProductViewSet(_AdminModelViewSet):
    queryset = Product.objects.all()
    serializer_class = ProductSerializer
    pagination_class = None


class VoucherViewSet(_AdminModelViewSet):
    queryset = Voucher.objects.prefetch_related('lines').all()
    serializer_class = VoucherSerializer
    pagination_class = None


class InvoiceViewSet(_AdminModelViewSet):
    queryset = Invoice.objects.prefetch_related('lines').all()
    serializer_class = InvoiceSerializer
    pagination_class = None


class SalesTypeViewSet(_AdminModelViewSet):
    queryset = SalesType.objects.all()
    serializer_class = SalesTypeSerializer
    pagination_class = None


class PartyAdjustmentViewSet(_AdminModelViewSet):
    queryset = PartyAdjustment.objects.all()
    serializer_class = PartyAdjustmentSerializer
    pagination_class = None


class TreasuryTxnViewSet(_AdminModelViewSet):
    queryset = TreasuryTxn.objects.all()
    serializer_class = TreasuryTxnSerializer
    pagination_class = None


class EmployeeViewSet(_AdminModelViewSet):
    queryset = Employee.objects.all()
    serializer_class = EmployeeSerializer
    pagination_class = None


class PayslipViewSet(_AdminModelViewSet):
    queryset = Payslip.objects.all()
    serializer_class = PayslipSerializer
    pagination_class = None


class CompanySettingsView(APIView):
    """Read/update the singleton company settings."""

    permission_classes = [IsAdminAccount]

    def _get_instance(self):
        instance, _created = CompanySettings.objects.get_or_create(id=1)
        if instance.bank_account_id is None and Account.objects.exists():
            # Backfill the mapping for an empty/legacy settings row.
            seed_default_data(Account, CompanySettings)
            instance.refresh_from_db()
        return instance

    def get(self, request):
        serializer = CompanySettingsSerializer(self._get_instance())
        return Response(serializer.data)

    def patch(self, request):
        serializer = CompanySettingsSerializer(
            self._get_instance(), data=request.data, partial=True
        )
        serializer.is_valid(raise_exception=True)
        serializer.save()
        return Response(serializer.data)


@api_view(['POST'])
@permission_classes([IsAdminAccount])
@transaction.atomic
def reset_accounting_data(request):
    """Wipes all accounting data and recreates a clean, zeroed starting point."""
    Voucher.objects.all().delete()
    Invoice.objects.all().delete()
    PartyAdjustment.objects.all().delete()
    SalesType.objects.all().delete()
    TreasuryTxn.objects.all().delete()
    Payslip.objects.all().delete()
    Employee.objects.all().delete()
    Product.objects.all().delete()
    Party.objects.all().delete()
    CompanySettings.objects.all().delete()
    Account.objects.all().delete()

    seed_default_data(Account, CompanySettings)
    return Response({'message': 'اطلاعات حسابداری بازنشانی شد.'}, status=status.HTTP_200_OK)