from django.db import transaction

from rest_framework.decorators import action
from rest_framework import exceptions
from rest_framework import mixins
from rest_framework import permissions
from rest_framework import response
from rest_framework import viewsets

from . import filters
from . import models
from . import mutations
from . import serializers
from . import signals
from . import tasks
from . import utils


class SkipFilterForGetObject:
    def get_object(self, *args, **kwargs):
        setattr(self.request, "_skip_filters", True)
        return super().get_object(*args, **kwargs)

    def filter_queryset(self, queryset):
        if getattr(self.request, "_skip_filters", False):
            return queryset
        return super().filter_queryset(queryset)


class MutationViewSet(
    mixins.ListModelMixin,
    mixins.RetrieveModelMixin,
    mixins.DestroyModelMixin,
    viewsets.GenericViewSet,
):
    lookup_field = "uuid"
    queryset = (
        models.Mutation.objects.all()
        .exclude(target_id=None)
        .order_by("-creation_date")
        .select_related("created_by", "approved_by")
        .prefetch_related("target")
    )
    serializer_class = serializers.APIMutationSerializer
    permission_classes = [permissions.IsAuthenticated]
    ordering_fields = ("creation_date",)
    filterset_class = filters.MutationFilter

    def perform_destroy(self, instance):
        if instance.is_applied:
            raise exceptions.PermissionDenied("You cannot delete an applied mutation")

        actor = self.request.user.actor
        is_owner = actor == instance.created_by

        if not any(
            [
                is_owner,
                mutations.registry.has_perm(
                    perm="approve", type=instance.type, obj=instance.target, actor=actor
                ),
            ]
        ):
            raise exceptions.PermissionDenied()

        return super().perform_destroy(instance)

    @action(detail=True, methods=["post"])
    @transaction.atomic
    def approve(self, request, *args, **kwargs):
        instance = self.get_object()
        if instance.is_applied:
            return response.Response(
                {"error": "This mutation was already applied"}, status=403
            )
        actor = self.request.user.actor
        can_approve = mutations.registry.has_perm(
            perm="approve", type=instance.type, obj=instance.target, actor=actor
        )

        if not can_approve:
            raise exceptions.PermissionDenied()
        previous_is_approved = instance.is_approved
        instance.approved_by = actor
        instance.is_approved = True
        instance.save(update_fields=["approved_by", "is_approved"])
        utils.on_commit(tasks.apply_mutation.delay, mutation_id=instance.id)
        utils.on_commit(
            signals.mutation_updated.send,
            sender=None,
            mutation=instance,
            old_is_approved=previous_is_approved,
            new_is_approved=instance.is_approved,
        )
        return response.Response({}, status=200)

    @action(detail=True, methods=["post"])
    @transaction.atomic
    def reject(self, request, *args, **kwargs):
        instance = self.get_object()
        if instance.is_applied:
            return response.Response(
                {"error": "This mutation was already applied"}, status=403
            )
        actor = self.request.user.actor
        can_approve = mutations.registry.has_perm(
            perm="approve", type=instance.type, obj=instance.target, actor=actor
        )

        if not can_approve:
            raise exceptions.PermissionDenied()
        previous_is_approved = instance.is_approved
        instance.approved_by = actor
        instance.is_approved = False
        instance.save(update_fields=["approved_by", "is_approved"])
        utils.on_commit(
            signals.mutation_updated.send,
            sender=None,
            mutation=instance,
            old_is_approved=previous_is_approved,
            new_is_approved=instance.is_approved,
        )
        return response.Response({}, status=200)