--- a/server/python/django2/renkanmanager/api/views.py	Tue May 03 14:32:28 2016 +0200
+++ b/server/python/django2/renkanmanager/api/views.py	Tue Jun 07 10:44:41 2016 +0200
@@ -87,7 +87,7 @@
         try:
             renkan = self.get_object(renkan_guid=renkan_guid)
         except Renkan.DoesNotExist:
-            return Response({'detail': 'Renkan project %r does not exist'.format(renkan_guid)}, status=status.HTTP_404_NOT_FOUND)
+            return Response({'detail': 'Renkan project '+renkan_guid+' does not exist'}, status=status.HTTP_404_NOT_FOUND)
         self.check_object_permissions(request, renkan)
         serializer = RenkanSerializer(renkan)
         if {'true': True, 'false': False, "0": False, "1": True}.get(request.GET.get("content_only", "false").lower()):
@@ -98,7 +98,7 @@
         try:
             renkan = self.get_object(renkan_guid=renkan_guid)
         except Renkan.DoesNotExist:
-            return Response({'detail': 'Renkan project %r does not exist'.format(renkan_guid)}, status=status.HTTP_404_NOT_FOUND)
+            return Response({'detail': 'Renkan project '+renkan_guid+' does not exist'}, status=status.HTTP_404_NOT_FOUND)
         logger.debug("RENKAN PUT %r : CHECKING OBJECT PERMISSION", renkan_guid)
         logger.debug("RENKAN PUT: permission? %r", request.user.has_perm("change_renkan", renkan))
         self.check_object_permissions(request, renkan)
@@ -109,9 +109,13 @@
             put_data["title"] = request.data.get("title", "")
         else:
             put_data = request.data
+        if put_data.get("validation_timestamp", None) is None and put_data.get("content", None) is not None:
+            put_data["validation_timestamp"] = json.loads(put_data["content"]).get("updated", "")
         serializer = RenkanSerializer(renkan, data=put_data)
         if serializer.is_valid():
             serializer.save(updator=request.user)
+            if {'true': True, 'false': False, "0": False, "1": True}.get(request.GET.get("content_only", "false").lower()):
+                return Response(json.loads(serializer.data["content"]), status=status.HTTP_200_OK, content_type='application/json')
             return Response(serializer.data, status=status.HTTP_200_OK, content_type='application/json')
         return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)
 

--- a/server/python/django2/renkanmanager/models.py	Tue May 03 14:32:28 2016 +0200
+++ b/server/python/django2/renkanmanager/models.py	Tue Jun 07 10:44:41 2016 +0200
@@ -9,6 +9,7 @@
 from django.db import models, transaction
 from django.core.exceptions import ValidationError
 from django.utils import timezone, dateparse
+from django.utils.translation import ugettext_lazy as _
 
 
 
@@ -120,6 +121,12 @@
         else:
             return ''
     
+    def __unicode__(self):
+        return self.renkan_guid
+    
+    def __str__(self):
+        return self.renkan_guid
+    
     @transaction.atomic
     def save_renkan(self, updator, timestamp="", title="", content="", create_new_revision=False):
         """
@@ -128,7 +135,7 @@
         """
         if (not timestamp) or ((self.current_revision is not None) and dateparse.parse_datetime(timestamp) < self.current_revision.modification_date):
             logger.error("SAVING RENKAN: provided timestamp is %r, which isn't current revision modification_date %r", timestamp, self.current_revision.modification_date)
-            raise ValidationError(message="Error saving Renkan: provided timestamp isn't current revision modification_date")
+            raise ValidationError(_("Cannot save, provided timestamp is invalid"))
         else:
             dt_timestamp = dateparse.parse_datetime(timestamp)
         self.save()

--- a/server/python/django2/renkanmanager/serializers.py	Tue May 03 14:32:28 2016 +0200
+++ b/server/python/django2/renkanmanager/serializers.py	Tue Jun 07 10:44:41 2016 +0200
@@ -1,11 +1,14 @@
-import json, uuid, datetime, time
+import json, logging, uuid, datetime, time
 
 from django.db import transaction
 from django.contrib.auth import get_user_model
 from django.conf import settings
+from django.core.exceptions import ValidationError
+from django.utils import dateparse
 from renkanmanager.models import Renkan, Workspace, Revision
 from rest_framework import serializers
 
+logger = logging.getLogger(__name__)
 RENKAN_USER_DISPLAY_FIELD = getattr(settings, "RENKAN_USER_DISPLAY_FIELD", get_user_model().USERNAME_FIELD)
 
 class RenkanSerializer(serializers.Serializer):
@@ -66,6 +69,8 @@
             validation_timestamp = validated_data.get('validation_timestamp')
         else:
             validation_timestamp = json.loads(content).get("updated", "")
+        if dateparse.parse_datetime(validation_timestamp) < renkan.current_revision.modification_date:
+            raise serializers.ValidationError("Provided timestamp is invalid")
         if title != json.loads(content).get("title", ""):
             content_dict = json.loads(content)
             content_dict["title"] = title
@@ -73,7 +78,7 @@
         try:
             renkan.save_renkan(updator=updator, timestamp=validation_timestamp, title=title, content=content, create_new_revision=create_new_revision)
         except ValidationError as ve:
-            raise serializers.ValidationError(ve.args[0])
+            raise serializers.ValidationError(str(ve.args[0]))
         return renkan
     
     def validate_workspace_id(self, value):
@@ -88,20 +93,22 @@
     
     def validate_content(self, value):  
         try:
-            json.loads(value)
+            loaded_json = json.loads(value)
         except ValueError:
             raise serializers.ValidationError("Content format is not a JSON-serializable")
-        loaded_json = json.loads(value)
-            
         if (not "nodes" in loaded_json):
             raise serializers.ValidationError("Content requires a 'nodes' entry")
         if (not "edges" in loaded_json):
             raise serializers.ValidationError("Content requires a 'edges' entry")
         if (not "views" in loaded_json):
             raise serializers.ValidationError("Content requires a 'views' entry")
-            
         return value
-
+    
+    def validate_validation_timestamp(self, value):
+        logger.debug("%r", value)
+        if self.instance and dateparse.parse_datetime(value) < self.get_current_revision_modification_date(self.instance):
+            raise serializers.ValidationError("Invalid timestamp was provided")
+        return value
 
 class RevisionSerializer(serializers.Serializer):
     id = serializers.ReadOnlyField(source="revision_guid")