from rest_framework import viewsets, filters, status
from rest_framework.decorators import action
from rest_framework.permissions import IsAuthenticated
from rest_framework.response import Response
from django_filters.rest_framework import DjangoFilterBackend
from django.utils import timezone
from django.db import transaction

from utils.permissions import ClubLevelPermission, ClubFilterBackend
from .models import (
    Homework, HomeworkExerciseItem, HomeworkAssignment, 
    HomeworkAssignmentItem, HomeworkStatus,
    TrainingHomeworkAssignment, TrainingHomeworkExerciseItem
)
from .serializers import (
    HomeworkSerializer, HomeworkDetailSerializer, HomeworkExerciseItemSerializer,
    HomeworkAssignmentSerializer, HomeworkAssignmentListSerializer,
    AssignHomeworkSerializer, CompleteItemSerializer, HomeworkStatusSerializer,
    TrainingHomeworkAssignmentSerializer, TrainingHomeworkAssignmentCreateSerializer
)
from wrestleDesk.pagination import StandardResultsSetPagination


class HomeworkViewSet(viewsets.ModelViewSet):
    queryset = Homework.objects.prefetch_related('exercise_items', 'exercise_items__exercise').all()
    serializer_class = HomeworkSerializer
    pagination_class = StandardResultsSetPagination
    permission_classes = [IsAuthenticated]
    filter_backends = [DjangoFilterBackend, filters.SearchFilter, filters.OrderingFilter]
    filterset_fields = ['club', 'is_active']
    search_fields = ['title', 'description']
    ordering_fields = ['created_at', 'due_date']

    def get_serializer_class(self):
        if self.action == 'retrieve':
            return HomeworkDetailSerializer
        return HomeworkSerializer


class HomeworkExerciseItemViewSet(viewsets.ModelViewSet):
    queryset = HomeworkExerciseItem.objects.select_related('homework', 'exercise').all()
    serializer_class = HomeworkExerciseItemSerializer
    pagination_class = StandardResultsSetPagination
    permission_classes = [IsAuthenticated]
    filter_backends = [DjangoFilterBackend]
    filterset_fields = ['homework']


class HomeworkAssignmentViewSet(viewsets.ModelViewSet):
    queryset = HomeworkAssignment.objects.select_related('homework', 'wrestler', 'club').prefetch_related('items').all()
    serializer_class = HomeworkAssignmentSerializer
    pagination_class = StandardResultsSetPagination
    permission_classes = [IsAuthenticated]
    filter_backends = [DjangoFilterBackend, filters.SearchFilter, filters.OrderingFilter]
    filterset_fields = ['homework', 'wrestler', 'club', 'is_completed']
    search_fields = ['wrestler__first_name', 'wrestler__last_name']
    ordering_fields = ['created_at', 'due_date']

    def get_serializer_class(self):
        if self.action == 'list':
            return HomeworkAssignmentListSerializer
        return HomeworkAssignmentSerializer

    @action(detail=True, methods=['post'])
    @transaction.atomic
    def complete_item(self, request, pk=None):
        serializer = CompleteItemSerializer(data=request.data)
        if not serializer.is_valid():
            return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)

        assignment = self.get_object()
        item_id = serializer.validated_data['item_id']

        try:
            item = assignment.items.get(id=item_id)
        except HomeworkAssignmentItem.DoesNotExist:
            return Response(
                {'detail': 'Item not found'},
                status=status.HTTP_404_NOT_FOUND
            )

        item.is_completed = True
        item.completion_date = timezone.now()
        item.save()

        return Response({'status': 'item completed'})

    @action(detail=False, methods=['post'])
    @transaction.atomic
    def assign(self, request):
        serializer = AssignHomeworkSerializer(data=request.data)
        if not serializer.is_valid():
            return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)

        homework_id = serializer.validated_data['homework']
        wrestler_ids = serializer.validated_data['wrestlers']
        due_date = serializer.validated_data.get('due_date')
        notes = serializer.validated_data.get('notes', '')

        try:
            homework = Homework.objects.get(id=homework_id)
        except Homework.DoesNotExist:
            return Response({'detail': 'Homework not found'}, status=status.HTTP_404_NOT_FOUND)

        created_assignments = []
        errors = []

        for wrestler_id in wrestler_ids:
            try:
                existing = HomeworkAssignment.objects.filter(
                    homework=homework,
                    wrestler_id=wrestler_id
                ).exists()

                if existing:
                    errors.append(f"Wrestler {wrestler_id} hat bereits diese Hausaufgabe")
                    continue

                assignment = HomeworkAssignment.objects.create(
                    homework=homework,
                    wrestler_id=wrestler_id,
                    club=homework.club,
                    due_date=due_date,
                    notes=notes
                )

                # Copy exercises from homework to assignment
                for exercise_item in homework.exercise_items.all():
                    HomeworkAssignmentItem.objects.create(
                        assignment=assignment,
                        exercise=exercise_item.exercise
                    )

                created_assignments.append(assignment.id)

            except Exception as e:
                errors.append(f"Wrestler {wrestler_id}: {str(e)}")

        return Response({
            'created': created_assignments,
            'errors': errors
        })


class HomeworkStatusViewSet(viewsets.ModelViewSet):
    queryset = HomeworkStatus.objects.select_related('homework', 'wrestler').all()
    serializer_class = HomeworkStatusSerializer
    pagination_class = StandardResultsSetPagination
    permission_classes = [IsAuthenticated]
    filter_backends = [DjangoFilterBackend, filters.OrderingFilter]
    filterset_fields = ['homework', 'wrestler', 'is_completed']
    ordering_fields = ['created_at', 'completion_date']


# NEUES SYSTEM: Training-basierte Homework

class TrainingHomeworkAssignmentViewSet(viewsets.ModelViewSet):
    permission_classes = [IsAuthenticated]
    filter_backends = [DjangoFilterBackend, filters.SearchFilter, filters.OrderingFilter]
    serializer_class = TrainingHomeworkAssignmentSerializer
    filterset_fields = ['is_completed', 'training', 'wrestler']
    search_fields = ['wrestler__first_name', 'wrestler__last_name']
    ordering_fields = ['created_at', 'is_completed']
    http_method_names = ['get', 'post', 'patch', 'delete']

    def get_queryset(self):
        queryset = TrainingHomeworkAssignment.objects.select_related(
            'training', 'wrestler'
        ).prefetch_related(
            'exercises', 'exercises__exercise'
        ).all()
        
        # Filter by training ID if provided
        training_id = self.request.query_params.get('training')
        if training_id:
            queryset = queryset.filter(training_id=training_id)
        
        return queryset

    def get_serializer_class(self):
        if self.action == 'create':
            return TrainingHomeworkAssignmentCreateSerializer
        return TrainingHomeworkAssignmentSerializer

    @action(detail=True, methods=['post'])
    def complete(self, request, pk=None):
        assignment = self.get_object()
        assignment.is_completed = True
        assignment.completion_date = timezone.now().date()
        assignment.save()
        # Also mark all exercises as completed
        assignment.exercises.update(is_completed=True)
        serializer = self.get_serializer(assignment)
        return Response(serializer.data)

    @action(detail=True, methods=['post'])
    def uncomplete(self, request, pk=None):
        assignment = self.get_object()
        assignment.is_completed = False
        assignment.completion_date = None
        assignment.save()
        # Also mark all exercises as not completed
        assignment.exercises.update(is_completed=False)
        serializer = self.get_serializer(assignment)
        return Response(serializer.data)

    @action(detail=True, methods=['post'])
    def complete_exercise(self, request, pk=None):
        assignment = self.get_object()
        exercise_id = request.data.get('exercise_id')
        
        if not exercise_id:
            return Response({'detail': 'exercise_id is required'}, status=status.HTTP_400_BAD_REQUEST)
        
        try:
            item = assignment.exercises.get(id=exercise_id)
            item.is_completed = True
            item.save()
            return Response({'status': 'exercise completed'})
        except TrainingHomeworkExerciseItem.DoesNotExist:
            return Response({'detail': 'Exercise not found'}, status=status.HTTP_404_NOT_FOUND)

    @action(detail=True, methods=['post'])
    def uncomplete_exercise(self, request, pk=None):
        assignment = self.get_object()
        exercise_id = request.data.get('exercise_id')
        
        if not exercise_id:
            return Response({'detail': 'exercise_id is required'}, status=status.HTTP_400_BAD_REQUEST)
        
        try:
            item = assignment.exercises.get(id=exercise_id)
            item.is_completed = False
            item.save()
            return Response({'status': 'exercise uncompleted'})
        except TrainingHomeworkExerciseItem.DoesNotExist:
            return Response({'detail': 'Exercise not found'}, status=status.HTTP_404_NOT_FOUND)