from django.shortcuts import render
from django.contrib.auth.models import User, Group
from django.core.exceptions import ObjectDoesNotExist
from rest_framework import viewsets, status
from rest_framework import permissions
from rest_framework.views import APIView
from .serializers import *
from parts import models as parts_models
from rest_framework.response import Response
from django.db.models.deletion import ProtectedError
from django.db.models import F
import datetime
from datetime import timedelta
from django.conf import settings
from django.utils import timezone
from rest_framework.authtoken.views import ObtainAuthToken
from rest_framework.authtoken.models import Token
from rest_framework.throttling import AnonRateThrottle
from rest_framework.decorators import action
from rest_framework import filters
import django_filters.rest_framework

# Create your views here.
class UserViewSet(viewsets.ReadOnlyModelViewSet):
    """
    API endpoint that allows users to be viewed or edited.
    """
    queryset = User.objects.all()
    serializer_class = UserSerializer
    permission_classes = [permissions.IsAuthenticated]
    filter_backends = [filters.SearchFilter]
    search_fields = ['username', 'first_name', 'last_name', 'email']

class GroupViewSet(viewsets.ReadOnlyModelViewSet):
    """
    API endpoint that allows users to be viewed or edited.
    """
    queryset = Group.objects.all()
    serializer_class = GroupSerializer
    permission_classes = [permissions.IsAuthenticated]

class PartsStorageViewSet(viewsets.ModelViewSet):
    queryset = parts_models.Storage.objects.all()
    serializer_class = StorageSerializer
    permission_classes = [permissions.DjangoModelPermissions]
    filter_backends = [django_filters.rest_framework.DjangoFilterBackend]
    filterset_fields = ['id', 'name', 'parent_storage']
    
class PartsComponentViewSet(viewsets.ModelViewSet):
    queryset = parts_models.Component.objects.all()
    serializer_class = ComponentSerializer
    permission_classes = [permissions.DjangoModelPermissions]
    filter_backends = [filters.SearchFilter]
    search_fields = ['id', 'name', 'package__name', 'manufacturer__name']

class PartsComponentTypeViewSet(viewsets.ModelViewSet):
    queryset = parts_models.ComponentType.objects.all()
    serializer_class = ComponentTypeSerializer
    permission_classes = [permissions.DjangoModelPermissions]
    filter_backends = [filters.SearchFilter]
    search_fields = ['class_name']

class PartsComponentParameterTypeViewSet(viewsets.ModelViewSet):
    queryset = parts_models.ComponentParameterType.objects.all()
    serializer_class = ComponentParameterTypeSerializer
    permission_classes = [permissions.DjangoModelPermissions]
    filter_backends = [filters.SearchFilter]
    search_fields = ['parameter_name', 'unit']

class PartsManufacturerViewSet(viewsets.ModelViewSet):
    queryset = parts_models.Manufacturer.objects.all()
    serializer_class = ManufacturerSerializer
    permission_classes = [permissions.DjangoModelPermissions]
    filter_backends = [filters.SearchFilter]
    search_fields = ['name']

class PartsStockViewSet(viewsets.ModelViewSet):
    queryset = parts_models.Stock.objects.all()
    serializer_class = StockSerializer
    permission_classes = [permissions.DjangoModelPermissions]

    @action(detail=True, methods=['patch'], name="change-stock-count")
    def update_stock(self, request, pk=None):
        stock = self.get_object()
        serializer = StockIncrementDecrementSerializer(data=request.data)
        if serializer.is_valid():
            increment = serializer.data['increment']
            if stock.atomic_increment(increment):
                return Response({'status': 'Stock updated', 'update_value': increment})
            else:
                return Response({'status': 'Stock not updated. Would be negative'}, status=status.HTTP_400_BAD_REQUEST)
        else:
            return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)

class PartsPackageViewSet(viewsets.ModelViewSet):
    queryset = parts_models.Package.objects.all()
    serializer_class = PackageSerializer
    permission_classes = [permissions.DjangoModelPermissions]
    filter_backends = [filters.SearchFilter]
    search_fields = ['name']

class PartsDistributorviewSet(viewsets.ModelViewSet):
    queryset = parts_models.Distributor.objects.all()
    serializer_class = DistributorSerializer
    permission_classes = [permissions.DjangoModelPermissions]
    filter_backends = [filters.SearchFilter]
    search_fields = ['name']


## Token Authentication views

EXPIRE_HOURS = getattr(settings, 'REST_FRAMEWORK_TOKEN_EXPIRE_HOURS', 24)


class ObtainExpiringAuthToken(ObtainAuthToken):
    throttle_classes = [AnonRateThrottle]
    def post(self, request):
        serializer = self.serializer_class(data=request.data)
        if serializer.is_valid():
            try:
                token = Token.objects.get(user=serializer.validated_data['user'])
                if token.created < timezone.now() - timedelta(hours=EXPIRE_HOURS):
                   token.delete()
            except Token.DoesNotExist:
                pass

            token, created =  Token.objects.get_or_create(user=serializer.validated_data['user'])

            if not created:
                # update the created time of the token to keep it valid
                token.created = datetime.datetime.utcnow()
            token.save()

            return Response({'token': token.key, 'username': serializer.validated_data['user'].username, 'expiry': token.created + timedelta(hours=EXPIRE_HOURS)})
        return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)


class TokenLogout(APIView):
    def post(self, request, format=None):
        try:
            request.user.auth_token.delete()
        except AttributeError as e:
            pass
        return Response(status=status.HTTP_200_OK)
    def get(self, request, format=None):
        return Response(status=status.HTTP_405_METHOD_NOT_ALLOWED)