from rest_framework import status
from rest_framework.viewsets import ModelViewSet
from rest_framework.decorators import action
from rest_framework.response import Response
from rest_framework.permissions import IsAuthenticated
from rest_framework.filters import SearchFilter, OrderingFilter
from django_filters.rest_framework import DjangoFilterBackend

from core.paginations.limit_offset import CustomLimitOffsetPagination

from apps.time_entries.models import TimeEntry
from apps.time_entries.api.serializers import (
    TimeEntrySerializer,
    TimeEntryCreateSerializer,
    TimeEntryUpdateSerializer,
    TimeEntryStopSerializer
)
from apps.time_entries.services.time_entries import (
    create_time_entry,
    update_time_entry,
    stop_time_entry
)


class TimeEntryViewSet(ModelViewSet):
    """
    API endpoints for managing time entries.
    """
    pagination_class = CustomLimitOffsetPagination
    permission_classes = [IsAuthenticated]
    
    filter_backends = [DjangoFilterBackend, SearchFilter, OrderingFilter]
    filterset_fields = ["workspace", "project", "is_billable"]
    search_fields = ["description", "project__name", "tags__name"]
    ordering_fields = ["start_time", "end_time", "created_at", "updated_at"]
    ordering = ["-start_time"]

    def get_queryset(self):
        """
        Users can only interact with their own time entries within workspaces 
        where they hold an active membership.
        """
        if getattr(self, "swagger_fake_view", False) or not self.request.user.is_authenticated:
            return TimeEntry.objects.none()

        return TimeEntry.objects.filter(
            user=self.request.user,
            workspace__memberships__user=self.request.user,
            workspace__memberships__is_active=True,
            is_deleted=False
        ).distinct()

    def get_serializer_class(self):
        if self.action == "create":
            return TimeEntryCreateSerializer
        elif self.action in ["update", "partial_update"]:
            return TimeEntryUpdateSerializer
        elif self.action == "stop":
            return TimeEntryStopSerializer
        return TimeEntrySerializer

    def create(self, request, *args, **kwargs):
        serializer = self.get_serializer(data=request.data)
        serializer.is_valid(raise_exception=True)
        
        entry = create_time_entry(
            user=request.user,
            workspace_id=serializer.validated_data.pop("workspace_id"),
            **serializer.validated_data
        )
        
        output_serializer = TimeEntrySerializer(entry)
        return Response(output_serializer.data, status=status.HTTP_201_CREATED)

    def update(self, request, *args, **kwargs):
        partial = kwargs.pop("partial", False)
        entry = self.get_object()
        
        serializer = self.get_serializer(data=request.data, partial=partial)
        serializer.is_valid(raise_exception=True)
        
        updated_entry = update_time_entry(
            entry=entry,
            **serializer.validated_data
        )
        
        output_serializer = TimeEntrySerializer(updated_entry)
        return Response(output_serializer.data, status=status.HTTP_200_OK)

    @action(detail=True, methods=["post"])
    def stop(self, request, pk=None):
        """
        Dedicated endpoint to stop an actively running timer.
        """
        entry = self.get_object()
        
        serializer = self.get_serializer(data=request.data)
        serializer.is_valid(raise_exception=True)
        
        end_time = serializer.validated_data.get("end_time")
        stopped_entry = stop_time_entry(entry, end_time=end_time)
        
        output_serializer = TimeEntrySerializer(stopped_entry)
        return Response(output_serializer.data, status=status.HTTP_200_OK)

    def destroy(self, request, *args, **kwargs):
        """
        Soft deletes the time entry.
        """
        entry = self.get_object()
        entry.is_deleted = True
        entry.save(update_fields=["is_deleted", "updated_at"])
        return Response(status=status.HTTP_204_NO_CONTENT)