from django.db.models import Q
from django.shortcuts import get_object_or_404
from rest_framework import status
from rest_framework.response import Response
from rest_framework.filters import OrderingFilter, SearchFilter
from django_filters.rest_framework import DjangoFilterBackend
from rest_framework.viewsets import ModelViewSet
from rest_framework.permissions import IsAuthenticated

from apps.notifications.membership_events import (
    notify_workspace_membership_added,
    notify_workspace_membership_deactivated,
    notify_workspace_membership_removed,
    notify_workspace_membership_role_changed,
)
from apps.workspaces.api.permissions import IsWorkspaceOwner, IsWorkspaceAdmin
from apps.workspaces.api.serializers import WorkspaceMembershipSerializer, WorkspaceSerializer
from apps.workspaces.api.filters import WorkspaceFilter, WorkspaceMembershipFilter
from apps.workspaces.models import Workspace, WorkspaceMembership
from core.paginations.limit_offset import CustomLimitOffsetPagination


class WorkspaceViewSet(ModelViewSet):
    serializer_class = WorkspaceSerializer
    pagination_class = CustomLimitOffsetPagination
    filter_backends = (DjangoFilterBackend, OrderingFilter, SearchFilter)
    filterset_class = WorkspaceFilter
    search_fields = ("name", "description")
    ordering_fields = ("created_at", "updated_at", "name")
    ordering = ("-updated_at", "-created_at")

    def get_queryset(self):
        user = self.request.user
        if not user.is_authenticated:
            return Workspace.objects.none()

        return Workspace.objects.filter(
            Q(owner=user) | 
            Q(memberships__user=user, memberships__is_active=True)
        ).distinct()
    
    def get_permissions(self):
        if self.action in ["update", "partial_update"]:
            return [IsAuthenticated(), IsWorkspaceAdmin()]

        elif self.action == "destroy":
            return [IsAuthenticated(), IsWorkspaceOwner()]

        return [IsAuthenticated()]
        
    def perform_create(self, serializer):
        serializer.save(owner=self.request.user)


class WorkspaceMembershipViewSet(ModelViewSet):
    serializer_class = WorkspaceMembershipSerializer
    pagination_class = CustomLimitOffsetPagination
    filter_backends = (DjangoFilterBackend, OrderingFilter, SearchFilter)
    filterset_class = WorkspaceMembershipFilter
    search_fields = (
        "user__mobile", 
        "user__email", 
        "user__first_name", 
        "user__last_name", 
        "workspace__name"
    )
    ordering_fields = ("joined_at", "created_at", "role")
    ordering = ("-created_at",)

    def get_queryset(self):
        user = self.request.user
        if not user.is_authenticated:
            return WorkspaceMembership.objects.none()

        return WorkspaceMembership.objects.filter(
            Q(workspace__owner=user) | 
            Q(workspace__memberships__user=user, workspace__memberships__is_active=True)
        ).distinct()

    def get_permissions(self):
        if self.action in ["update", "partial_update"]:
            return [IsAuthenticated(), IsWorkspaceAdmin()]
        if self.action in ["destroy"]:
            return [IsAuthenticated(), IsWorkspaceOwner()]
            
        return [IsAuthenticated()]

    def create(self, request, *args, **kwargs):
        """
        Overridden to check permissions manually. 
        Because the membership object doesn't exist yet, standard DRF object-level 
        permissions won't catch payload-level workspace violations.
        """
        workspace_id = request.data.get("workspace")
        if not workspace_id:
            return Response(
                {"workspace": ["This field is required."]}, 
                status=status.HTTP_400_BAD_REQUEST
            )
            
        workspace = get_object_or_404(Workspace, id=workspace_id)
        
        permission = IsWorkspaceAdmin()
        if not permission.has_object_permission(request, self, workspace):
            return Response(
                {"detail": "You must be a Workspace Admin or Owner to add members."},
                status=status.HTTP_403_FORBIDDEN
            )
            
        serializer = self.get_serializer(data=request.data)
        serializer.is_valid(raise_exception=True)
        membership = serializer.save()
        notify_workspace_membership_added(
            actor=request.user,
            recipient=membership.user,
            workspace=membership.workspace,
            role=membership.role,
        )
        return Response(
            WorkspaceMembershipSerializer(membership, context=self.get_serializer_context()).data,
            status=status.HTTP_201_CREATED,
        )

    def update(self, request, *args, **kwargs):
        partial = kwargs.pop("partial", False)
        membership = self.get_object()
        previous_role = membership.role
        previous_is_active = membership.is_active

        serializer = self.get_serializer(membership, data=request.data, partial=partial)
        serializer.is_valid(raise_exception=True)
        updated_membership = serializer.save()

        if not previous_is_active and updated_membership.is_active:
            notify_workspace_membership_added(
                actor=request.user,
                recipient=updated_membership.user,
                workspace=updated_membership.workspace,
                role=updated_membership.role,
            )
        elif previous_is_active and not updated_membership.is_active:
            notify_workspace_membership_deactivated(
                actor=request.user,
                recipient=updated_membership.user,
                workspace=updated_membership.workspace,
                role=previous_role,
            )
        elif previous_role != updated_membership.role:
            notify_workspace_membership_role_changed(
                actor=request.user,
                recipient=updated_membership.user,
                workspace=updated_membership.workspace,
                previous_role=previous_role,
                new_role=updated_membership.role,
            )

        return Response(
            WorkspaceMembershipSerializer(
                updated_membership,
                context=self.get_serializer_context(),
            ).data,
            status=status.HTTP_200_OK,
        )

    def partial_update(self, request, *args, **kwargs):
        kwargs["partial"] = True
        return self.update(request, *args, **kwargs)

    def destroy(self, request, *args, **kwargs):
        membership = self.get_object()
        recipient = membership.user
        workspace = membership.workspace
        role = membership.role
        membership.delete()
        notify_workspace_membership_removed(
            actor=request.user,
            recipient=recipient,
            workspace=workspace,
            role=role,
        )
        return Response(status=status.HTTP_204_NO_CONTENT)