subscription fixes

app/routes/threads.py

@@ -46,9 +46,10 @@ def thread(slug):
             'user_id': get_active_user().id,
         })
         if subscription:
-            subscription.update({
-                'last_seen': int(time.time())
-            })
+            if int(posts[-1]['created_at']) > int(subscription.last_seen):
+                subscription.update({
+                    'last_seen': int(posts[-1]['created_at'])
+                })
             is_subscribed = True
 
     return render_template(
@@ -78,6 +79,13 @@ def reply(slug):
     post_content = request.form['post_content']
     post = create_post(thread.id, user.id, post_content)
 
+    subscription = Subscriptions.find({'user_id': user.id, 'thread_id': thread.id})
+
+    if subscription:
+        subscription.update({'last_seen': int(time.time())})
+    elif request.form.get('subscribe', default=None) == 'on':
+        Subscriptions.create({'user_id': user.id, 'thread_id': thread.id, 'last_seen': int(time.time())})
+
     return redirect(url_for(".thread", slug=slug, after=post.id, _anchor="latest-post"))