class RecipeViewSet(viewsets.ModelViewSet):
    queryset = Recipe.objects.prefetch_related(
        'author', 'tags', 'ingredients').all()
    serializer_class = RecipeSerializer
    permission_classes = (IsCreatorOrReadOnly,)
    filter_backends = (DjangoFilterBackend,)
    filterset_class = RecipeFilter

    def create_delete_recipe(self, request, pk, sent_serializer, model):
        recipe = get_object_or_404(Recipe, pk=pk)
        if request.method == 'POST':
            serializer = sent_serializer(
                data={'user': request.user.id, 'recipe': recipe.id}
            )
            serializer.is_valid(raise_exception=True)
            serializer.save()
            additional_recipe_serializer = AdditionalRecipeSerializer(recipe)
            return Response(
                additional_recipe_serializer.data,
                status=status.HTTP_201_CREATED,
            )
        specific_recipe = get_object_or_404(
            model, user=request.user, recipe=recipe
        )
        specific_recipe.delete()
        return Response(status=status.HTTP_204_NO_CONTENT)

    @action(
        detail=True,
        methods=['post', 'delete'],
        url_path='favorite',
        permission_classes=(IsAuthenticated,)
    )
    def favorite(self, request, pk):
        return self.create_delete_recipe(
            request, pk, FavoriteSerializer, Favorite)

    @action(
        detail=True,
        methods=['post', 'delete'],
        url_path='shopping_cart',
        permission_classes=(IsAuthenticated,)
    )
    def shopping_cart(self, request, pk):
        return self.create_delete_recipe(
            request, pk, ShoppingListSerializer, ShoppingList)

    def create_shopping_list(self, ingredients):
        shopping_list = ''
        for ingredient in ingredients:
            shopping_list += (
                f"{ingredient['ingredient__name']}: "
                f"{ingredient['sum']}"
                f"({ingredient['ingredient__measurement_unit']})\n"
            )
        return shopping_list

    @action(
        detail=False,
        methods=['get'],
        permission_classes=(IsAuthenticated,),
        url_path='download_shopping_cart',
    )
    def download_shopping_list(self, request):
        ingredients = RecipeIngredient.objects.filter(
            recipe__shopping_list__user=request.user
        ).values(
            'ingredient__name',
            'ingredient__measurement_unit'
        ).annotate(sum=Sum('amount'))
        shopping_list = self.create_shopping_list(ingredients)
        response = HttpResponse(shopping_list, content_type='text/plain')
        return response

    def get_serializer_class(self):
        if self.request.method == 'GET':
            return RecipeSafeSerializer
        return RecipeSerializer