Step navigation is adjusted to stay within the assignment

econplayground/assignment/migrations/0011_remove_step_next_step.py

@@ -0,0 +1,17 @@
+# Generated by Django 4.2.7 on 2023-11-20 18:44
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('assignment', '0010_stepresult_scorepath'),
+    ]
+
+    operations = [
+        migrations.RemoveField(
+            model_name='step',
+            name='next_step',
+        ),
+    ]

econplayground/assignment/models.py

@@ -177,18 +177,15 @@ class Step(MP_Node):
         Question, on_delete=models.SET_NULL,
         blank=True, null=True)
 
-    next_step = models.ForeignKey(
-        'self', on_delete=models.SET_NULL,
-        blank=True, null=True)
-
     @property
     def is_last_step(self) -> bool:
-        return self.next_step is None and \
-            self.get_next() is None and \
-            self.get_next_intervention() is None
+        return (self.depth == 2 and self.get_next_sibling() is None) or \
+            (self.depth == 3 and self.get_next() is None)
 
     def get_prev(self) -> Self:
         """Return the previous child, or the prev sibling, or None."""
+        if self.is_root_node:
+            return None
 
         node = self.get_prev_sibling()
         if node:
@@ -197,7 +194,11 @@ def get_prev(self) -> Self:
                 return child
 
         if not node:
-            return self.get_parent()
+            parent = self.get_parent()
+            if parent and not parent.is_root_node:
+                return parent
+            else:
+                return None
 
         return node
 
@@ -207,6 +208,13 @@ def get_next(self) -> Self:
         This is probably the result of a correct answer on the student
         side.
         """
+
+        # In case you find yourself in a root node, go to the first child.
+        if self.is_root_node:
+            child = self.get_first_child()
+            if child:
+                return child
+
         node = self.get_next_sibling()
         if node:
             return node
@@ -215,7 +223,7 @@ def get_next(self) -> Self:
         if parent:
             node = parent.get_next_sibling()
 
-        if node:
+        if node and not node.is_root_node:
             return node
 
         child = self.get_first_child()

econplayground/assignment/tests/test_views.py

@@ -247,13 +247,12 @@ def test_step_question_management(self):
         r = self.client.post(
             reverse('tree_edit', kwargs={'pk': self.assignment.pk}), {
                 'action': 'save',
-                'step_next_' + str(step.pk): new_step.pk,
             }, follow=True)
         self.assertEqual(r.status_code, 200)
         self.assertContains(r, 'Steps updated.')
         self.assertEqual(Step.objects.count(), 3)
         step.refresh_from_db()
-        self.assertEqual(step.next_step, new_step)
+        self.assertEqual(step.get_next(), new_step)
 
     def test_build_linear_assignment(self):
         r = self.client.post(