myModelSerializer.py

from rest_framework import serializers
from django.utils import timezone
from .pendingModeration import PendingModeration
from django.conf import settings
from django.contrib.contenttypes.models import ContentType
from backend.utils import is_member
from .myModel import MyModel


class MyModelSerializer(serializers.ModelSerializer):
    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)

    # TODO : updated_by_username useless ? See in rest API
    updated_by_username = serializers.SerializerMethodField(read_only=True)

    def get_updated_by_username(self, obj):
        if obj.updated_by:
            return obj.updated_by.username
        else:
            return None

    class Meta:
        model = MyModel

    def moderation_required(self):
        user = self.get_user_in_request()
        request = self.context['request']

        if user.is_staff:
            return False

        if settings.MODERATION_ACTIVATED:
            if request.method in ['POST', 'PUT']:  # should be always the case
                return not is_member('Moderators', request.user)

        return False

    def get_user_in_request(self):
        return self.context['request'].user

    def set_model_attr_no_moder(self, moderated_and_updated):
        user = self.get_user_in_request()
        now = timezone.now()
        self.validated_data['moderated_by'] = user
        self.validated_data['moderated_on'] = now

        if moderated_and_updated:
            self.validated_data['updated_by'] = user
            self.validated_data['updated_on'] = now

    def clean_validated_data(self):
        self.validated_data['moderated_by'] = None
        self.validated_data['moderated_on'] = None
        self.validated_data['updated_by'] = None
        self.validated_data['updated_on'] = None

    def get_pending_models(self):
        ct = ContentType.objects.get_for_model(self.Meta.model)
        return PendingModeration.objects.filter(
            content_type=ct, object_id=self.instance.pk)

    def save(self, **kwargs):
        user = self.get_user_in_request()
        self.clean_validated_data()

        if self.moderation_required():
            if self.instance is None:  # we need to create the main model
                self.instance = super(
                    MyModelSerializer, self).save(**kwargs)

            objs_pending_db = self.get_pending_models()

            self.clean_validated_data()  # Make that it is done...
            if len(objs_pending_db) > 0:
                pending_instance = objs_pending_db[0]
                pending_instance.updated_on = timezone.now()
                pending_instance.updated_by = user
                pending_instance.new_object = self.validated_data
            else:
                pending_instance = PendingModeration(
                    referenced_object=self.instance,
                    updated_by=user,
                    updated_on=timezone.now(),
                    new_object=self.validated_data
                )
            pending_instance.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(**kwargs)
            else:
                # We check if we don't have any moderation pending
                objs_pending_db = self.get_pending_models()
                if len(objs_pending_db) > 0:
                    obj_pending_db = objs_pending_db[0]
                    self.clean_validated_data()  # Make that it is done...
                    if obj_pending_db.new_object == self.validated_data:
                        moderated_and_updated = False
                        self.validated_data['updated_by'] = obj_pending_db.updated_by
                        self.validated_data['updated_on'] = obj_pending_db.updated_on

                    objs_pending_db.delete()

                self.set_model_attr_no_moder(moderated_and_updated)
                return super(MyModelSerializer, self).save(**kwargs)