delete thread when no more posts remain

app/routes/posts.py

@@ -5,7 +5,7 @@ from .users import login_required, get_active_user
 from ..lib.babycode import babycode_to_html
 from ..constants import InfoboxKind
 from ..db import db
-from ..models import Posts, PostHistory, Threads
+from ..models import Posts, PostHistory, Threads, Topics
 
 bp = Blueprint("posts", __name__, url_prefix = "/post")
 
@@ -50,10 +50,25 @@ def delete(post_id):
     post = Posts.find({'id': post_id})
     thread = Threads.find({'id': post.thread_id})
     user = get_active_user()
+    if not user:
+        return redirect(url_for('threads.thread', slug=thread.slug))
 
     if user.is_mod() or post.user_id == user.id:
         post.delete()
-        flash("Post deleted.", InfoboxKind.INFO)
+
+        post_count = Posts.count({
+            'thread_id': thread.id,
+        })
+
+        if post_count == 0:
+            topic = Topics.find({
+                'id': thread.topic_id,
+            })
+            thread.delete()
+            flash('Thread deleted.', InfoboxKind.INFO)
+            return redirect(url_for('topics.topic', slug=topic.slug))
+
+        flash('Post deleted.', InfoboxKind.INFO)
 
     return redirect(url_for('threads.thread', slug=thread.slug))