First things to implement a event change log

dav_events/models/__init__.py

@@ -1,5 +1,6 @@
 from ..roles import get_system_user, get_ghost_user
 from .event import Event
+from .eventchange import EventChange
 from .eventflag import EventFlag
 from .eventstatus import EventStatus
 from .oneclickaction import OneClickAction

dav_events/models/event.py

@@ -2,6 +2,7 @@
 from __future__ import unicode_literals
 import datetime
 import difflib
+import json
 import logging
 import os
 import re
@@ -16,12 +17,12 @@ from django.utils.encoding import python_2_unicode_compatible
 from django.utils.translation import get_language, ugettext_lazy as _
 from django_countries.fields import CountryField
 
-from . import get_ghost_user
 from .. import choices
 from .. import config
 from .. import signals
 from ..workflow import DefaultWorkflow
-
+from . import get_ghost_user
+from .eventchange import EventChange
 
 logger = logging.getLogger(__name__)
 
@@ -292,9 +293,8 @@ class Event(models.Model):
                 logger.warning('Event is not created by its owner (Current user: %s, Owner: %s)!', self.editor, owner)
             self.owner = owner
             creating = True
-        elif not implicit_update:
+        else:
             original = Event.objects.get(id=self.id)
-            original_text = original.render_as_text(show_internal_fields=True)
 
         if not self.editor or not self.editor.is_authenticated:
             self.editor = self.owner
@@ -305,13 +305,40 @@ class Event(models.Model):
             logger.info('Event created: %s', self)
             signals.event_created.send(sender=self.__class__, event=self)
             self.workflow.update_status('draft', self.editor)
-        elif not implicit_update:
-            modified_text = self.render_as_text(show_internal_fields=True)
-            o_lines = original_text.split('\n')
-            m_lines = modified_text.split('\n')
-            diff_lines = list(difflib.unified_diff(o_lines, m_lines, n=len(m_lines), lineterm=''))
-            logger.info('Event updated: %s', self)
-            signals.event_updated.send(sender=self.__class__, event=self, diff=diff_lines, user=self.editor)
+        else:
+            change = EventChange(event=self, user=self.editor, operation='update', content=self.diff(original))
+            change.save()
+            if not implicit_update:
+                logger.info('Event updated: %s', self)
+                signals.event_updated.send(sender=self.__class__, event=self, diff=self.diff(original, fmt='human_readable'), user=self.editor)
+
+    def diff(self, event, fmt='json'):
+        if fmt == 'human_readable':
+            from_text = event.render_as_text(show_internal_fields=True)
+            to_text = self.render_as_text(show_internal_fields=True)
+            from_lines = from_text.split('\n')
+            to_lines = to_text.split('\n')
+            diff_lines = list(difflib.unified_diff(from_lines, to_lines, n=len(from_lines), lineterm=''))
+            diff_text = '\n'.join(diff_lines[3:])
+        elif fmt == 'json':
+            fields = self._meta.get_fields()
+            changes = []
+            for field in fields:
+                field_name = field.name
+                from_value = getattr(event, field_name)
+                to_value = getattr(self, field_name)
+                if from_value != to_value:
+                    change = {
+                        'field': field_name,
+                        'refer': str(from_value),
+                        'current': str(to_value),
+                    }
+                    changes.append(change)
+            diff_text = json.dumps(changes)
+        else:
+            raise ValueError("Event.diff(): Unsupported format: {}".format(fmt))
+
+        return diff_text
 
     def is_deadline_expired(self):
         today = datetime.date.today()

dav_events/models/eventchange.py

@@ -0,0 +1,36 @@
+from __future__ import unicode_literals
+from django.conf import settings
+from django.db import models
+from django.utils import timezone
+from django.utils.encoding import python_2_unicode_compatible
+
+from . import get_ghost_user, get_system_user
+
+CHANGE_OPERATIONS = (
+    ('update', 'update'),
+)
+
+
+def get_system_user_id():
+    return get_system_user().id
+
+
+@python_2_unicode_compatible
+class EventChange(models.Model):
+    event = models.ForeignKey('dav_events.Event', related_name='changes')
+    timestamp = models.DateTimeField(default=timezone.now)
+    user = models.ForeignKey(settings.AUTH_USER_MODEL,
+                             default=get_system_user_id,
+                             on_delete=models.SET(get_ghost_user),
+                             related_name='+')
+
+    operation = models.CharField(max_length=20, choices=CHANGE_OPERATIONS)
+    content = models.TextField()
+
+    class Meta:
+        ordering = ['event', 'timestamp']
+
+    def __str__(self):
+        s = '{timestamp} - {user} - {operation}'
+        return s.format(operation=self.operation, timestamp=self.timestamp.strftime('%d.%m.%Y %H:%M:%S %Z'),
+                        user=self.user)