Save the user's selected sort order on the comments service.

Requires cs_comments_service to have the field default_sort_key on users.

lms/djangoapps/django_comment_client/forum/views.py

@@ -102,7 +102,7 @@ def get_threads(request, course_id, discussion_id=None):
     default_query_params = {
         'page': 1,
         'per_page': THREADS_PER_PAGE,
-        'sort_key': 'activity',
+        'sort_key': 'date',
         'sort_order': 'desc',
         'text': '',
         'tags': '',
@@ -110,6 +110,17 @@ def get_threads(request, course_id, discussion_id=None):
         'course_id': course_id,
     }
 
+    if not request.GET.get('sort_key'):
+        # If the user did not select a sort key, use their last used sort key
+        user = cc.User.from_django_user(request.user)
+        user.retrieve()
+        default_query_params['sort_key'] = user.default_sort_key
+    else:
+        # If the user clicked a sort key, update their default sort key
+        user = cc.User.from_django_user(request.user)
+        user.default_sort_key = request.GET.get('sort_key')
+        user.save()
+
     query_params = merge_dict(default_query_params,
                               strip_none(extract(request.GET, ['page', 'sort_key', 'sort_order', 'text', 'tags'])))
 

lms/lib/comment_client/user.py

@@ -8,10 +8,10 @@ class User(models.Model):
     accessible_fields = ['username', 'email', 'follower_ids', 'upvoted_ids', 'downvoted_ids',
                          'id', 'external_id', 'subscribed_user_ids', 'children', 'course_id',
                          'subscribed_thread_ids', 'subscribed_commentable_ids',
-                         'threads_count', 'comments_count',
+                         'threads_count', 'comments_count', 'default_sort_key'
                         ]
 
-    updatable_fields = ['username', 'external_id', 'email']
+    updatable_fields = ['username', 'external_id', 'email', 'default_sort_key']
     initializable_fields = updatable_fields
 
     base_url = "{prefix}/users".format(prefix=settings.PREFIX)