Refactor model imports and update admin classes to use pghistory for historical tracking; replace HistoricalModel with TrackedModel in relevant models

history_tracking/models.py

@@ -2,6 +2,7 @@
 from django.db import models
 from django.contrib.contenttypes.models import ContentType
 from django.contrib.contenttypes.fields import GenericForeignKey
+from django.contrib.auth import get_user_model
 from simple_history.models import HistoricalRecords
 from .mixins import HistoricalChangeMixin
 from typing import Any, Type, TypeVar, cast
@@ -9,8 +10,46 @@ from django.db.models import QuerySet
 
 T = TypeVar('T', bound=models.Model)
 
+class DiffMixin:
+    """Mixin to add diffing capabilities to pghistory events"""
+    def get_prev_record(self):
+        """Get the previous record for this instance"""
+        try:
+            return type(self).objects.filter(
+                pgh_created_at__lt=self.pgh_created_at,
+                pgh_obj_id=self.pgh_obj_id
+            ).order_by('-pgh_created_at').first()
+        except (AttributeError, TypeError):
+            return None
+
+    def diff_against_previous(self):
+        """Compare this record against the previous one"""
+        prev_record = self.get_prev_record()
+        if not prev_record:
+            return {}
+
+        changes = {}
+        skip_fields = {
+            'pgh_id', 'pgh_created_at', 'pgh_label', 
+            'pgh_obj_id', 'pgh_context_id', '_state'
+        }
+
+        for field in self.__dict__:
+            if field not in skip_fields and not field.startswith('_'):
+                try:
+                    old_value = getattr(prev_record, field)
+                    new_value = getattr(self, field)
+                    if old_value != new_value:
+                        changes[field] = {"old": str(old_value), "new": str(new_value)}
+                except AttributeError:
+                    continue
+        return changes
+
 class HistoricalModel(models.Model):
-    """Abstract base class for models with history tracking"""
+    """
+    Legacy abstract base class for models with history tracking.
+    Use TrackedModel for new implementations.
+    """
     id = models.BigAutoField(primary_key=True)
     history: HistoricalRecords = HistoricalRecords(
         inherit=True,
@@ -30,6 +69,27 @@ class HistoricalModel(models.Model):
         model = self._history_model
         return model.objects.filter(id=self.pk).order_by('-history_date')
 
+class TrackedModel(models.Model):
+    """Abstract base class for models with pghistory tracking.
+    The @pghistory.track() decorator should be applied to concrete models
+    that inherit from this class.
+    """
+    id = models.BigAutoField(primary_key=True)
+
+    class Meta:
+        abstract = True
+
+    def get_history(self) -> QuerySet:
+        """Get all history records for this instance in chronological order"""
+        history_model = self.get_history_model()
+        return history_model.objects.filter(
+            pgh_obj_id=self.pk
+        ).order_by('-pgh_created_at')
+
+    def get_history_model(self) -> Type[Any]:
+        """Get the pghistory model for this instance"""
+        return self.pgh_obj_event_model
+
 class HistoricalSlug(models.Model):
     """Track historical slugs for models"""
     content_type = models.ForeignKey(ContentType, on_delete=models.CASCADE)