food to tree (model, api, serializer)

cookbook/migrations/food_to_tree.py

@@ -0,0 +1,57 @@
+# Generated by Django 3.2.5 on 2021-08-14 15:40
+
+from treebeard.mp_tree import MP_Node
+from django.db import migrations, models
+from django_scopes import scopes_disabled
+# update if needed
+steplen = MP_Node.steplen
+alphabet = MP_Node.alphabet
+node_order_by = ["name"]
+
+
+def update_paths(apps, schema_editor):
+    with scopes_disabled():
+        Node = apps.get_model("cookbook", "Food")
+        nodes = Node.objects.all().order_by(*node_order_by)
+        for i, node in enumerate(nodes, 1):
+            # for default values, this resolves to: "{:04d}".format(i)
+            node.path = f"{{:{alphabet[0]}{steplen}d}}".format(i)
+        if nodes:
+            Node.objects.bulk_update(nodes, ["path"])
+
+
+def backwards(apps, schema_editor):
+    """nothing to do"""
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('cookbook', '0147_auto_20210813_1829'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='food',
+            name='depth',
+            field=models.PositiveIntegerField(default=0),
+            preserve_default=False,
+        ),
+        migrations.AddField(
+            model_name='food',
+            name='numchild',
+            field=models.PositiveIntegerField(default=0),
+        ),
+        migrations.AddField(
+            model_name='food',
+            name='path',
+            field=models.CharField(default=0, max_length=255, unique=False),
+            preserve_default=False,
+        ),
+        migrations.RunPython(update_paths, backwards),
+        migrations.AlterField(
+            model_name="food",
+            name="path",
+            field=models.CharField(max_length=255, unique=True),
+        ),
+    ]