Resource.part_hierarchy uses the exam definition

Previously, a Resource's part hierarchy was computed from the SCORM
elements of attempts at that resource. That meant that the hierarchy
can't be worked with until there is at least one attempt, and attempts
can't differ in their structure.

This replaces that routine with one that looks at the exam's definition.
It still doesn't cope with randomised order or different structures
resulting from things like explore or diagnostic mode, but at least it
can be determined without waiting for an attempt.

The form to discount parts is always available, fixing #344

Author: christianp

numbas_lti/models.py

@@ -316,6 +316,24 @@ def resolve_feedback_setting(setting):
 
         return info
 
+    def part_hierarchy(self):
+        data = self.source()
+
+        hierarchy = {}
+        qn = 0
+        for qg in data.get('question_groups',[]):
+            for q in qg.get('questions',[]):
+                qd = hierarchy[qn] = {}
+                for i,part in enumerate(q.get('parts',[])):
+                    p = {'gaps': [], 'steps': []}
+                    if part['type'] == 'gapfill':
+                        p['gaps'] = list(range(len(part.get('gaps',[]))))
+                    p['steps'] = list(range(len(part.get('steps',[]))))
+                    qd[i] = p
+                qn += 1
+        
+        return hierarchy
+
 
 GRADING_METHODS = [
     ('highest',_('Highest score')),
@@ -672,33 +690,9 @@ def user_data(self,user):
         return LTIUserData.objects.filter(resource=self,user=user).last()
 
     def part_hierarchy(self):
-        """
-            Returns an object
-                {
-                    question_num: {
-                        part_num: {
-                            gaps: [list of gap indices],
-                            steps: [list of step indices]
-                        }
-                    }
-                }
-        """
-        paths = sorted(set(e['value'] for e in ScormElement.objects.filter(attempt__resource=self,key__regex=r'cmi.interactions.[0-9]+.id').values('value')),key=lambda x:(len(x),x))
-        re_path = re.compile(r'q([0-9]+)p([0-9]+)(?:g([0-9]+)|s([0-9]+))?')
-        out = defaultdict(lambda: defaultdict(lambda: {'gaps':[],'steps':[]}))
-        for path in paths:
-            m = re_path.match(path)
-            question_index = m.group(1)
-            part_index = m.group(2)
-            gap_index = m.group(3)
-            step_index = m.group(4)
-            p = out[question_index][part_index]
-            if m.group(3):
-                p['gaps'].append(gap_index)
-            elif m.group(4):
-                p['steps'].append(step_index)
-    
-        return out
+        if self.exam is None:
+            return {}
+        return self.exam.part_hierarchy()
 
     def last_activity(self):
         if self.attempts.exists():
@@ -1362,6 +1356,7 @@ def part_discount(self,part):
         return self.resource.discounted_parts.filter(part=part).first()
 
     def part_paths(self):
+        """ Paths to all parts in this attempt. """
         return set(e['value'] for e in self.scormelements.filter(key__regex='cmi.interactions.[0-9]+.id').values('value').distinct())
 
     def part_hierarchy(self):

numbas_lti/templates/numbas_lti/management/dashboard.html

@@ -37,7 +37,7 @@ <h1>{% translate "Dashboard" %}
         {% endif %}
     </section>
 
-    {% if resource.attempts.count %}
+    {% if has_attempts %}
 
         <section id="attempts-count">
             <p><strong>{{resource.unbroken_attempts.count}}</strong> {% blocktranslate count counter=resource.unbroken_attempts.count %}attempt{% plural %}attempts{% endblocktranslate %} {% translate "by" %} <strong>{{students.count}}</strong> {% blocktranslate count counter=students.count %}student{% plural %}students{% endblocktranslate %}.</p>
@@ -66,8 +66,15 @@ <h1>{% translate "Dashboard" %}
         </section>
         {% endif %}
 
-        <section>
-            <ul class="list-unstyled actions">
+    {% else %}
+        <section id="attempts-count">
+            <p>{% translate "No students have attempted this exam yet. Information about scores will appear here once a student attempts this exam." %}</p>
+        </section>
+    {% endif %}
+
+    <section>
+        <ul class="list-unstyled actions">
+            {% if has_attempts %}
                 <li><form method="POST" action="{% url_with_lti 'scores_csv' resource.pk %}">{% csrf_token %}<button type="submit" class="button info">{% icon 'save' %} {% translate "Download scores as CSV" %}</button></form></li>
                 {% if not last_report_process %}
                 <li>
@@ -77,22 +84,19 @@ <h1>{% translate "Dashboard" %}
                     {% endif %}
                 </li>
                 {% endif %}
-                <li><a class="button" href="{% url_with_lti 'student_progress' resource.pk %}">{% icon 'user' %} {% translate "View individual student progress and grant access tokens" %}</a></li>
-                <li>
-                    <a class="button danger" href="{% url_with_lti 'discount_parts' resource.pk %}">{% icon 'minus-sign' %} {% translate "Discount question parts" %}</a>
-                    <span class="help-block">{% translate "You can remark individual attempts on the attempts page." %}</span>
-                </li>
-                <li>
-                    <a class="button info" href="{% url_with_lti 'validate_receipt' resource.pk %}">{% icon 'ok' %} {% translate "Validate a receipt code" %}</a>
-                </li>
-            </ul>
-        </section>
-
-    {% else %}
-        <section id="attempts-count">
-            <p>{% translate "No students have attempted this exam yet. Information about scores will appear here once a student attempts this exam." %}</p>
-        </section>
-    {% endif %}
+            {% endif %}
+            <li><a class="button" href="{% url_with_lti 'student_progress' resource.pk %}">{% icon 'user' %} {% translate "View individual student progress and grant access tokens" %}</a></li>
+            <li>
+                <a class="button danger" href="{% url_with_lti 'discount_parts' resource.pk %}">{% icon 'minus-sign' %} {% translate "Discount question parts" %}</a>
+                <span class="help-block">{% translate "You can remark individual attempts on the attempts page." %}</span>
+            </li>
+            {% if has_attempts %}
+            <li>
+                <a class="button info" href="{% url_with_lti 'validate_receipt' resource.pk %}">{% icon 'ok' %} {% translate "Validate a receipt code" %}</a>
+            </li>
+            {% endif %}
+        </ul>
+    </section>
 
     {% if exam_info %}
     <hr>

numbas_lti/templates/numbas_lti/management/discount.html

@@ -39,10 +39,10 @@ <h1>{% translate "Discount question parts" %}</h1>
             </thead>
             <tbody>
                 {% for part in parts %}
-                <tr class="{% if part.p == None %}info{% endif %} {% if part.discount %}warning{% endif %}">
-                    <td class="{% if part.p == None %}question-id{% endif %} {% if part.p %}muted not-first-appearance{% endif %}">{{part.q}}</td>
+                <tr class="{% if part.p is None %}info{% endif %} {% if part.discount %}warning{% endif %}">
+                    <td class="{% if part.p is None %}question-id{% endif %} {% if part.p %}muted not-first-appearance{% endif %}">{{part.q}}</td>
                     <td class="{% if part.p and part.g %}muted not-first-appearance{% endif %}">{% if part.p %}{{part.p}}{% endif %}</td>
-                    <td>{% if part.g %}{{part.g}}{% endif %}</td>
+                    <td>{% if part.g is not None %}{{part.g}}{% endif %}</td>
                     <td class="part-control">
                         {% if part.p %}
                         <select name="discount-{{part.path}}">

numbas_lti/util.py

@@ -24,6 +24,11 @@ def hierarchy_key(x):
         return key
 
 def transform_part_hierarchy(hierarchy,transform,hierarchy_key=hierarchy_key):
+    """ 
+        Transform the part hierarchy of an exam.
+        ``hierarchy`` is a dictionary Dict[question_number:int -> Dict[part_number:int -> Dict["gaps" -> list[int], "steps" -> list[int]]]].
+        For each part in the hierarchy, the function ``transform`` is called with information about that part.
+    """
     out = []
 
     def row(q,p=None,g=None,parent=None,has_gaps=False):

numbas_lti/views/resource.py

@@ -211,6 +211,8 @@ def get_context_data(self,*args,**kwargs):
 
         context['num_unbroken_attempts'] = resource.attempts.exclude(broken=True).count()
 
+        context['has_attempts'] = resource.attempts.exists()
+
         if not resource.lineitem_unwanted and resource.lti_13_links.exists():
             lti_context = resource.lti_13_contexts().first()
             if lti_context: