From 648a414f0e684096a18dbbcd43ff8735c7284467 Mon Sep 17 00:00:00 2001
From: Jon <jonathon.lockwood@networkedweb.com>
Date: Sat, 17 May 2025 21:05:57 +0930
Subject: [PATCH] feat(core): Dynamic History model creation

ref: #765 #758 #759
---
 app/core/models/audit.py                      |  3 +-
 app/core/models/centurion.py                  | 31 ++++++++++
 app/core/models/meta.py                       | 62 +++++++++++++++++++
 .../centurion_erp/development/models.md       | 13 +---
 4 files changed, 96 insertions(+), 13 deletions(-)
 create mode 100644 app/core/models/meta.py

diff --git a/app/core/models/audit.py b/app/core/models/audit.py
index 277c019d..cf7911f9 100644
--- a/app/core/models/audit.py
+++ b/app/core/models/audit.py
@@ -143,7 +143,8 @@ class ModelHistory(
         TenancyObject (_type_): Centurion Tenancy Abstract model.
     """
 
-    audit_enabled: bool = False
+    _audit_enabled: bool = False
+    """Don't Save audit history for audit history model"""
 
 
     class Meta:
diff --git a/app/core/models/centurion.py b/app/core/models/centurion.py
index dee6293d..fbdfd18a 100644
--- a/app/core/models/centurion.py
+++ b/app/core/models/centurion.py
@@ -11,6 +11,13 @@ class CenturionModel(
 
 
 
+    _audit_enabled: bool = True
+    """Should this model have audit history kept"""
+
+    _is_submodel: bool = False
+    """This model a sub-model"""
+
+
     class Meta:
 
         abstract = True
@@ -22,3 +29,27 @@ class CenturionModel(
         if value is None:
 
             raise ValidationError(code = 'field_value_not_none', message = 'Value can not be none.')
+
+
+
+    def get_history_model_name(self) -> str:
+        """Get the name for the History Model
+
+        Returns:
+            str: Name of the history model (`<model class name>AuditHistory`)
+        """
+        
+        return f'{self._meta.object_name}AuditHistory'
+
+
+class CenturionSubModel(
+    CenturionModel
+):
+
+    _is_submodel: bool = True
+    """This model a sub-model"""
+
+
+    class Meta:
+
+        abstract = True
diff --git a/app/core/models/meta.py b/app/core/models/meta.py
new file mode 100644
index 00000000..0c9db3e8
--- /dev/null
+++ b/app/core/models/meta.py
@@ -0,0 +1,62 @@
+import sys
+import types
+
+from django.apps import apps
+from django.db import models
+from django.utils.module_loading import import_string
+
+
+
+module_path = f'centurion.models.meta'
+
+if module_path not in sys.modules:
+
+    sys.modules[module_path] = types.ModuleType(module_path)
+
+
+if any(cmd in sys.argv for cmd in ['runserver', 'makemigrations', 'migrate']):
+
+    if apps.models_ready:
+
+        existing_models = { m.__name__ for m in apps.get_models() }
+
+        for model in apps.get_models():
+
+            if not getattr(model, '_audit_enabled', False):
+                continue
+
+            name = model.__name__
+
+            audit_meta_name = model().get_history_model_name()
+
+            if audit_meta_name in existing_models:
+                continue
+
+
+            AuditMetaModel = type(
+                audit_meta_name,
+                ( import_string("core.models.audit.AuditMetaModel"), ),
+                {
+                    '__module__': module_path,
+                    '__qualname__': audit_meta_name,
+                    '__doc__': f'Auto-generated meta model for {name} Audit History.',
+                    'Meta': type('Meta', (), {
+                                'app_label': model._meta.app_label,
+                                'db_table': model._meta.db_table + '_history',
+                                'managed': True,
+                                'verbose_name': model._meta.verbose_name + ' History',
+                                'verbose_name_plural': model._meta.verbose_name + ' Histories',
+                            }),
+                    'model': models.ForeignKey(
+                        model,
+                        blank = False,
+                        help_text = 'Model this history belongs to',
+                        null = False,
+                        on_delete = models.CASCADE,
+                        related_name = 'audit_history',
+                        verbose_name = 'Model',
+                    )
+                }
+            )
+
+            setattr(sys.modules[module_path], audit_meta_name, AuditMetaModel)
diff --git a/docs/projects/centurion_erp/development/models.md b/docs/projects/centurion_erp/development/models.md
index 53dcf582..9f8c0ade 100644
--- a/docs/projects/centurion_erp/development/models.md
+++ b/docs/projects/centurion_erp/development/models.md
@@ -205,18 +205,7 @@ table_fields: list = [
 
 ## History
 
-Adding History to a model is a simple process. Please see the [Model History](./core/model_history.md) docs.
-
-In the case the model you are creating is inherited from another model, (a non-abstrct model), you may need to add the following variables to the inherited class so that the model link works:
-
-- `history_app_label` The application label for the model in question
-
-- `history_model_name` The model name for the model in question.
-
-
-### Example
-
-If you created a model called employee in the human_resources app, which is a sub-model that inherits from `Contact`, `Person` then `Entity`. In this case the `Entity` model is where the history is derived, which would create link `/access/entity/<pk>/history`. This link is incorrect. adding variables `history_app_label = 'human_resources'` and `history_model_name = 'Emplyee'` to the `Employee` model class; will now create a valid link, `/human_resources/employee/<pk>/history`.
+Adding [History](./core/model_history.md) to a model is automatic. If there is a desire not to have model history it can be disabled by adding attribute `_audit_enabled` to the model class and setting its value to `False.`
 
 
 ## Tests