Add a newest reply/newest leaf sorting method for comments

Implements #111

tildes/tildes/enums.py

@@ -45,6 +45,7 @@ class CommentTreeSortOption(enum.Enum):
     NEWEST = enum.auto()
     POSTED = enum.auto()
     RELEVANCE = enum.auto()
+    NEWEST_REPLY = enum.auto()
 
     @property
     def description(self) -> str:
@@ -55,6 +56,8 @@ class CommentTreeSortOption(enum.Enum):
             return "order posted"
         elif self.name == "RELEVANCE":
             return "relevance"
+        elif self.name == "NEWEST_REPLY":
+            return "newest reply"
 
         return "most {}".format(self.name.lower())
 

tildes/tildes/models/comment/comment_tree.py

@@ -100,6 +100,15 @@ class CommentTree:
         compare equal on the sorting method will be the same as the order that they were
         originally in when passed to this function.
         """
+        # sort the tree's comments first, this will be important when sorting by newest
+        # reply
+        for comment in tree:
+            if not comment.has_visible_descendant:
+                # no need to bother sorting replies if none will be visible
+                continue
+
+            comment.replies = CommentTree._sort_tree(comment.replies, sort)
+
         if sort == CommentTreeSortOption.NEWEST:
             tree = sorted(tree, key=lambda c: c.created_time, reverse=True)
         elif sort == CommentTreeSortOption.POSTED:
@@ -108,13 +117,15 @@ class CommentTree:
             tree = sorted(tree, key=lambda c: c.num_votes, reverse=True)
         elif sort == CommentTreeSortOption.RELEVANCE:
             tree = sorted(tree, key=lambda c: c.relevance_sorting_value, reverse=True)
-
-        for comment in tree:
-            if not comment.has_visible_descendant:
-                # no need to bother sorting replies if none will be visible
-                continue
-
-            comment.replies = CommentTree._sort_tree(comment.replies, sort)
+        elif sort == CommentTreeSortOption.NEWEST_REPLY:
+            # sort by the creation time of the most recent reply in the entire tree, or
+            # the comment itself if it has no children. the comment's first reply is
+            # the newest reply since it has been sorted above
+            tree = sorted(
+                tree,
+                key=lambda c: (c.replies[0] if c.replies else c).created_time,
+                reverse=True,
+            )
 
         return tree
 

tildes/tildes/views/topic.py

@@ -184,10 +184,13 @@ def get_group_topics(  # noqa
         groups = [request.context]
 
         if request.user:
-            groups.extend([
-                sub.group for sub in request.user.subscriptions
-                if sub.group.is_subgroup_of(request.context)
-            ])
+            groups.extend(
+                [
+                    sub.group
+                    for sub in request.user.subscriptions
+                    if sub.group.is_subgroup_of(request.context)
+                ]
+            )
 
             include_subgroups = all_subgroups
         else: