myModelSerializer.py

from django.contrib.contenttypes.models import ContentType
from django.utils import timezone

from backend_app.custom import MySerializerWithJSON
from backend_app.permissions import is_moderation_required
from backend_app.utils import get_user_level
from rest_framework import serializers
from rest_framework.validators import ValidationError
from shared.obj_moderation_permission import DEFAULT_OBJ_MODERATION_LV

from .myModel import MyModel
from .pendingModeration import PendingModeration

CLEANED_MY_MODEL_DATA = {
    "moderated_by": None,
    "moderated_on": None,
    "updated_by": None,
    "updated_on": None,
}


def override_data(old_data: dict, new_data: dict) -> dict:
    """Update the data in old_data with the one in new_data
    """

    for key in new_data:
        if key in old_data:
            old_data[key] = new_data[key]
    return old_data


class MyModelSerializer(MySerializerWithJSON):
    """Serializer to go along the MyModel Model. This serializer handles backend data moderation checks and tricks.

    Raises:
        ValidationError -- If you are trying to moderate something you don't have rights to
    """

    ######
    # Basic fields serializers
    updated_by = serializers.CharField(read_only=True)
    updated_on = serializers.DateTimeField(format="%Y-%m-%d %H:%M:%S", read_only=True)

    moderated_by = serializers.CharField(read_only=True)
    moderated_on = serializers.DateTimeField(format="%Y-%m-%d %H:%M:%S", read_only=True)

    has_pending_moderation = serializers.BooleanField(read_only=True)
    model_config = serializers.SerializerMethodField()

    # For easier handling on the client side, we force an id field
    # this is useful when a model has a dedicated primary key
    id = serializers.SerializerMethodField()

    def get_model_config(self, obj=None) -> dict:
        """
        Serializer for the `model_config` field.
        `obj` is required in the function definition, but it's not used.
        """

        return self.Meta.model.model_config

    def get_id(self, obj: MyModel):
        """
        Serializer for the id field.
        """
        return obj.pk

    class Meta:
        model = MyModel

    def get_user_from_request(self):
        """
        Function to retrieve the user from the request
        """
        return self.context["request"].user

    def validate(self, attrs):
        """
        Validate `MyModel` fields and enforce certain field at the backend level.

        Checks that the requested moderation level is not higher than the one of the user.
        """

        if "obj_moderation_level" in attrs:
            requested_obj_moder_lv = attrs["obj_moderation_level"]

            try:
                user_level = get_user_level(self.get_user_from_request())
            except KeyError:
                # if for some reason we don't have the user in the request
                # we set the level to the default one
                # this can occur during testing.
                user_level = DEFAULT_OBJ_MODERATION_LV

            if requested_obj_moder_lv > user_level:
                raise ValidationError(
                    "You can't request moderation for a higher rank than you."
                )

        return attrs

    def set_model_attrs_for_moderation_and_update(
        self, user, moderated_and_updated: bool
    ):
        """
        Overrides model attributes regarding moderation and update.
        The moderated field is set to the request user. The moderated_on field is reset to now.

        If there was an updated, the updated_by field and updated_on field are also reset.
        """
        now = timezone.now()
        self.override_validated_data({"moderated_by": user, "moderated_on": now})

        if moderated_and_updated:
            self.override_validated_data({"updated_by": user, "updated_on": now})

    def clean_validated_data(self):
        """
        Clear fields related to update and moderation
        """
        self.override_validated_data(CLEANED_MY_MODEL_DATA)

    def override_validated_data(self, new_data: dict):
        """
        Method used to force specific attributes when saving a model
        """
        for key in new_data:
            self.validated_data[key] = new_data[key]

    def do_before_save(self):
        """
        Action to perform before saving a model
        """
        pass

    def save(self, *args, **kwargs):
        """
        Function that handles all the moderation in a smart way.
        Nothing has to be done to tell that we won't the data to be moderated,
        it is detected automatically.
        """

        user = self.context["request"].user
        user_level = get_user_level(user)

        self.clean_validated_data()
        self.do_before_save()
        ct = ContentType.objects.get_for_model(self.Meta.model)

        if is_moderation_required(
            self.get_model_config(), self.instance, user, user_level
        ):
            if self.instance is None:  # we need to create the main model
                # Store the user for squashing data in versions models
                self.validated_data.updated_by = user
                self.instance = super().save(*args, **kwargs)

            data_to_save = dict()
            for key in self.validated_data:
                try:
                    # retrieve the submitted data and save the clean json
                    # to make sure it will be savable
                    data_to_save[key] = self.initial_data[key]
                except KeyError:
                    pass

            data_to_save = override_data(data_to_save, CLEANED_MY_MODEL_DATA)

            # Save instance into pending moderation state
            PendingModeration.objects.update_or_create(
                content_type=ct,
                object_id=self.instance.pk,
                defaults={
                    "updated_on": timezone.now(),
                    "updated_by": user,
                    "new_object": data_to_save,
                },
            )

            # Performance optimization, we store the fact that there is an object pending moderation
            self.instance.has_pending_moderation = True
            self.instance.save()
            return self.instance

        else:  # Moderation is not needed, we need to check whether it's a moderation or an update with no moderation

            moderated_and_updated = True
            if self.instance is None:
                self.set_model_attrs_for_moderation_and_update(
                    user, moderated_and_updated
                )
                instance = super().save(*args, **kwargs)
            else:
                try:
                    pending_instance = PendingModeration.objects.get(
                        content_type=ct, object_id=self.instance.pk
                    )
                    self.clean_validated_data()  # Make quez that it is done...
                    # We have to compare the serialized data
                    # So we make sure to compare the same elements
                    key_to_remove = []
                    for key in self.initial_data:
                        if key not in self.validated_data:
                            key_to_remove.append(key)
                    for key in key_to_remove:
                        self.initial_data.pop(key, None)

                    if pending_instance.new_object == self.initial_data:
                        moderated_and_updated = False
                        self.validated_data["updated_by"] = pending_instance.updated_by
                        self.validated_data["updated_on"] = pending_instance.updated_on
                    pending_instance.delete()

                except PendingModeration.DoesNotExist:
                    pass

                self.set_model_attrs_for_moderation_and_update(
                    user, moderated_and_updated
                )
                instance = super().save(*args, **kwargs)

            # Performance optimization to know if has pending moderation
            instance.has_pending_moderation = False
            instance.save()
            return instance