#330 backend: add moved_from field to assignable mixin

backend/dps_training_k/game/migrations/0007_materialinstance_moved_from_content_type_and_more.py

@@ -0,0 +1,45 @@
+# Generated by Django 5.0.1 on 2024-09-12 12:47
+
+import django.db.models.deletion
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("contenttypes", "0002_remove_content_type_name"),
+        ("game", "0006_remove_area_unique_area_names_per_exercise"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="materialinstance",
+            name="moved_from_content_type",
+            field=models.ForeignKey(
+                blank=True,
+                null=True,
+                on_delete=django.db.models.deletion.SET_NULL,
+                to="contenttypes.contenttype",
+            ),
+        ),
+        migrations.AddField(
+            model_name="materialinstance",
+            name="moved_from_object_id",
+            field=models.PositiveIntegerField(blank=True, null=True),
+        ),
+        migrations.AddField(
+            model_name="personnel",
+            name="moved_from_content_type",
+            field=models.ForeignKey(
+                blank=True,
+                null=True,
+                on_delete=django.db.models.deletion.SET_NULL,
+                to="contenttypes.contenttype",
+            ),
+        ),
+        migrations.AddField(
+            model_name="personnel",
+            name="moved_from_object_id",
+            field=models.PositiveIntegerField(blank=True, null=True),
+        ),
+    ]

backend/dps_training_k/helpers/assignable.py

@@ -1,11 +1,11 @@
+from django.contrib.contenttypes.fields import GenericForeignKey
+from django.contrib.contenttypes.models import ContentType
 from django.db import models
 
 from helpers import exactly_one_field_not_null
 
 
-class Assignable(
-    models.Model,
-):
+class Assignable(models.Model):
     class Meta:
         abstract = True
 
@@ -18,10 +18,16 @@ class Meta:
     area = models.ForeignKey("Area", on_delete=models.CASCADE, null=True, blank=True)
     lab = models.ForeignKey("Lab", on_delete=models.CASCADE, null=True, blank=True)
 
+    # GenericForeignKey is just a virtual field for unified access, only _content_type and _object_id are actually stored in DB
+    moved_from_content_type = models.ForeignKey(
+        ContentType, on_delete=models.SET_NULL, null=True, blank=True
+    )
+    moved_from_object_id = models.PositiveIntegerField(null=True, blank=True)
+    moved_from = GenericForeignKey("moved_from_content_type", "moved_from_object_id")
+
     def __init_subclass__(cls, **kwargs):
-        """Needed to create unique name for each constraint given to the subclasses of Assignable, but I can already define the constraint here."""
+        """Create a unique name for each constraint for subclasses of Assignable."""
         super().__init_subclass__(**kwargs)
-        # Add a unique constraint for each subclass of Assignable
         constraint_name = (
             f"assignable_{cls.__name__.lower()}_exactly_one_field_not_null"
         )
@@ -34,6 +40,8 @@ def __init_subclass__(cls, **kwargs):
     def _perform_move(self, obj):
         from game.models import PatientInstance, Area, Lab
 
+        self.moved_from = self.attached_instance()
+
         if isinstance(obj, PatientInstance):
             if self.patient_instance is obj:
                 return False
@@ -52,26 +60,30 @@ def _perform_move(self, obj):
             self.patient_instance = None
             self.area = None
             self.lab = obj
-        self.save(update_fields=["patient_instance", "area", "lab"])
+
+        self.save(
+            update_fields=[
+                "patient_instance",
+                "area",
+                "lab",
+                "moved_from_content_type",
+                "moved_from_object_id",
+            ]
+        )
         return True, ""
 
     @staticmethod
     def can_move_to_type(obj):
         from game.models import PatientInstance, Area, Lab
 
-        return (
-            isinstance(obj, PatientInstance)
-            or isinstance(obj, Area)
-            or isinstance(obj, Lab)
-        )
+        return isinstance(obj, (PatientInstance, Area, Lab))
 
     def is_blocked(self):
         return self.action_instance is not None
 
     def attached_instance(self):
-        return (
-            self.patient_instance or self.area or self.lab
-        )  # first not null value determined by short-circuiting
+        # First non-null value determined by short-circuiting
+        return self.patient_instance or self.area or self.lab
 
     def block(self, action_instance):
         self.action_instance = action_instance