myModelSerializer.py

from rest_framework import serializers
from rest_framework.validators import ValidationError
from django.utils import timezone
from .pendingModeration import PendingModeration
from django.contrib.contenttypes.models import ContentType
from .myModel import MyModel
from .pendingModeration import PendingModerationSerializer
from backend.utils import get_user_level
from backend.permissions import is_moderation_required
from backend.models.tools import MySerializerWithJSON

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


def override_data(old_data, new_data):
    for key in new_data:
        old_data[key] = new_data[key]
    return old_data


class MyModelSerializer(MySerializerWithJSON):
    moderated_on = serializers.DateTimeField(
        format="%Y-%m-%d %H:%M:%S", read_only=True)
    updated_on = serializers.DateTimeField(
        format="%Y-%m-%d %H:%M:%S", read_only=True)
    moderated_by = serializers.CharField(read_only=True)
    updated_by = serializers.CharField(read_only=True)
    pending_moderation = serializers.SerializerMethodField()
    model_config = serializers.SerializerMethodField()

    def get_model_config(self, obj=None):
        return self.Meta.model.model_config

    def get_pending_moderation(self, obj):
        if self.context['view'].action != 'list':
            return PendingModerationSerializer(obj.pending_moderation, many=True, read_only=True, context=self.context).data
        return None

    class Meta:
        model = MyModel

    def my_validate(self, attrs):
        return attrs

    def validate(self, attrs):
        """
        TODO unit test this
        """
        self.user = self.context['request'].user
        self.user_level = get_user_level(self.user)

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

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

        return self.my_validate(attrs)

    def set_model_attr_no_moder(self, moderated_and_updated):
        now = timezone.now()
        self.override_validated_data({
            'moderated_by': self.user,
            'moderated_on': now,
        })

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

    def clean_validated_data(self):
        self.override_validated_data(CLEANED_MY_MODEL_DATA)

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

    def my_pre_save(self):
        pass

    def save(self, *args, **kwargs):
        return self.my_save(*args, **kwargs)

    def my_save(self, *args, **kwargs):
        self.clean_validated_data()
        self.my_pre_save()
        ct = ContentType.objects.get_for_model(self.Meta.model)

        if is_moderation_required(self.get_model_config()['moderation_level'], self.instance, self.user, self.user_level):
            if self.instance is None:  # we need to create the main model
                self.instance = super(
                    MyModelSerializer, self).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)

            PendingModeration.objects.update_or_create(
                content_type=ct,
                object_id=self.instance.pk,
                defaults={
                    'updated_on': timezone.now(),
                    'updated_by': self.user,
                    'new_object': data_to_save
                })
            return self.instance

        else:

            moderated_and_updated = True
            if self.instance is None:
                self.set_model_attr_no_moder(moderated_and_updated)
                return super(MyModelSerializer, self).save(*args, **kwargs)
            else:
                try:
                    pending_instance = PendingModeration.objects.get(
                        content_type=ct,
                        object_id=self.instance.pk,
                    )
                    self.clean_validated_data()  # Make that it is done...
                    if pending_instance.new_object == self.validated_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_attr_no_moder(moderated_and_updated)
                return super(MyModelSerializer, self).save(*args, **kwargs)