weird header stuff

history_tracking/apps.py

@@ -7,14 +7,20 @@ class HistoryTrackingConfig(AppConfig):
     name = "history_tracking"
 
     def ready(self):
+        from django.apps import apps
         from .mixins import HistoricalChangeMixin
-        from .models import Park
 
-        models_with_history = [Park]
-
-        for model in models_with_history:
-            # Check if mixin is already applied
-            if HistoricalChangeMixin not in model.history.model.__bases__:
-                model.history.model.__bases__ = (
-                    HistoricalChangeMixin,
-                ) + model.history.model.__bases__
+        # Get the Park model
+        try:
+            Park = apps.get_model('parks', 'Park')
+            ParkArea = apps.get_model('parks', 'ParkArea')
+            
+            # Apply mixin to historical models
+            if HistoricalChangeMixin not in Park.history.model.__bases__:
+                Park.history.model.__bases__ = (HistoricalChangeMixin,) + Park.history.model.__bases__
+            
+            if HistoricalChangeMixin not in ParkArea.history.model.__bases__:
+                ParkArea.history.model.__bases__ = (HistoricalChangeMixin,) + ParkArea.history.model.__bases__
+        except LookupError:
+            # Models might not be loaded yet
+            pass

history_tracking/mixins.py

@@ -2,6 +2,17 @@
 
 
 class HistoricalChangeMixin:
+    @property
+    def prev_record(self):
+        """Get the previous record for this instance"""
+        try:
+            return type(self).objects.filter(
+                history_date__lt=self.history_date,
+                id=self.id
+            ).order_by('-history_date').first()
+        except (AttributeError, TypeError):
+            return None
+
     @property
     def diff_against_previous(self):
         prev_record = self.prev_record
@@ -15,9 +26,14 @@ class HistoricalChangeMixin:
                 "history_id",
                 "history_type",
                 "history_user_id",
+                "history_change_reason",
+                "history_type",
             ] and not field.startswith("_"):
-                old_value = getattr(prev_record, field)
-                new_value = getattr(self, field)
-                if old_value != new_value:
-                    changes[field] = {"old": old_value, "new": new_value}
+                try:
+                    old_value = getattr(prev_record, field)
+                    new_value = getattr(self, field)
+                    if old_value != new_value:
+                        changes[field] = {"old": old_value, "new": new_value}
+                except AttributeError:
+                    continue
         return changes

history_tracking/models.py

@@ -4,14 +4,11 @@ from simple_history.models import HistoricalRecords
 from .mixins import HistoricalChangeMixin
 
 
-class Park(models.Model):
-    name = models.CharField(max_length=200)
-    # ... other fields ...
-    history = HistoricalRecords()
+class HistoricalModel(models.Model):
+    """Abstract base class for models with history tracking"""
+    class Meta:
+        abstract = True
 
     @property
     def _history_model(self):
         return self.history.model
-
-
-# Apply the mixin