add is_free annotations on subject lists

frontend/templates/subjects.html

@@ -8,17 +8,23 @@
         <p>
         Below is a list of subjects for books that users have added to 
         wishlists. It is here primarily to show what subjects are present 
-        in the database to guide further development. You can order by the 
-        <a href="{% url subjects %}">subject name</a> or by the 
-        <a href="{% url subjects %}?order=count">number</a> of works 
-        with that subject.
+        in the database to guide further development. 
         </p>
+        <ul> 
+        <li> ordered by <a href="{% url subjects %}">subject name</a> </li>
+        <li> ordered by <a href="{% url subjects %}?order=count">number</a> of works with the subject.</li>
+        <li> ordered by <a href="{% url subjects %}?subset=free">subject name</a> (free works only)</li> 
+        <li> ordered by <a href="{% url subjects %}?order=count&amp;subset=free">number</a> of free works with the subject.</li>
+        </ul>
 
         <p>
         <ul>
         {% for subject in subjects %}
         
-            <li><a href="{% url free %}kw.{{ subject.name }}/">{{ subject.name }}</a> ({{ subject.works__count }}). {% if request.user.is_staff %} <a href="{% url free %}?setkw={{ subject.name }}">set keywords</a>{% endif %}</li>
+            <li><a href="{% url free %}kw.{{ subject.name }}/">{{ subject.name }}</a> 
+            ({% if subject.works__is_free__count %}{{ subject.works__is_free__count }} free out of {{ subject.works.all.count }}{% else %}{{ subject.works__count }}{% endif %} total works). 
+            {% if request.user.is_staff %} <a href="{% url free %}?setkw={{ subject.name }}">set keywords</a>{% endif %}
+            </li>
         {% endfor %}
         </ul>
         </p>

frontend/views.py

@@ -768,12 +768,19 @@ def googlebooks(request, googlebooks_id):
 def subjects(request):
     order = request.GET.get('order')
     subjects = models.Subject.objects.all()
-    subjects = subjects.annotate(Count('works'))
-
-    if request.GET.get('order') == 'count':
-        subjects = subjects.order_by('-works__count')
+    subjects = subjects
+    if request.GET.get('subset') == 'free':
+        subjects = models.Subject.objects.filter(works__is_free = True).annotate(Count('works__is_free'))
+        if request.GET.get('order') == 'count':
+            subjects = subjects.order_by('-works__is_free__count')
+        else:
+            subjects = subjects.order_by('name')
     else:
-        subjects = subjects.order_by('name')
+        subjects = models.Subject.objects.all().annotate(Count('works'))
+        if request.GET.get('order') == 'count':
+            subjects = subjects.order_by('-works__count')
+        else:
+            subjects = subjects.order_by('name')
 
     return render(request, 'subjects.html', {'subjects': subjects})