serializers.py

from rest_framework import serializers


class ActionSerializer(serializers.Serializer):
    """
    A special serializer that can operate on a list of objects
    and apply actions on it.
    """

    action = serializers.CharField(required=True)
    objects = serializers.JSONField(required=True)
    filters = serializers.DictField(required=False)
    actions = None
    filterset_class = None
    # those are actions identifier where we don't want to allow the "all"
    # selector because it's to dangerous. Like object deletion.
    dangerous_actions = []

    def __init__(self, *args, **kwargs):
        self.queryset = kwargs.pop("queryset")
        if self.actions is None:
            raise ValueError(
                "You must declare a list of actions on " "the serializer class"
            )

        for action in self.actions:
            handler_name = "handle_{}".format(action)
            assert hasattr(self, handler_name), "{} miss a {} method".format(
                self.__class__.__name__, handler_name
            )
        super().__init__(self, *args, **kwargs)

    def validate_action(self, value):
        if value not in self.actions:
            raise serializers.ValidationError(
                "{} is not a valid action. Pick one of {}.".format(
                    value, ", ".join(self.actions)
                )
            )
        return value

    def validate_objects(self, value):
        if value == "all":
            return self.queryset.all().order_by("id")
        if type(value) in [list, tuple]:
            return self.queryset.filter(pk__in=value).order_by("id")

        raise serializers.ValidationError(
            "{} is not a valid value for objects. You must provide either a "
            'list of identifiers or the string "all".'.format(value)
        )

    def validate(self, data):
        dangerous = data["action"] in self.dangerous_actions
        if dangerous and self.initial_data["objects"] == "all":
            raise serializers.ValidationError(
                "This action is to dangerous to be applied to all objects"
            )
        if self.filterset_class and "filters" in data:
            qs_filterset = self.filterset_class(
                data["filters"], queryset=data["objects"]
            )
            try:
                assert qs_filterset.form.is_valid()
            except (AssertionError, TypeError):
                raise serializers.ValidationError("Invalid filters")
            data["objects"] = qs_filterset.qs

        data["count"] = data["objects"].count()
        if data["count"] < 1:
            raise serializers.ValidationError("No object matching your request")
        return data

    def save(self):
        handler_name = "handle_{}".format(self.validated_data["action"])
        handler = getattr(self, handler_name)
        result = handler(self.validated_data["objects"])
        payload = {
            "updated": self.validated_data["count"],
            "action": self.validated_data["action"],
            "result": result,
        }
        return payload