add latest post info to topics view

apps/topics.lua

@@ -24,7 +24,7 @@ local ThreadCreateError = {
 app:get("all_topics", "", function(self)
   self.topic_list = db.query([[
     SELECT
-      topics.name, topics.slug, topics.description, topics.is_locked,
+      topics.id, topics.name, topics.slug, topics.description, topics.is_locked,
       users.username AS latest_thread_username,
       threads.title AS latest_thread_title,
       threads.slug AS latest_thread_slug,
@@ -43,6 +43,44 @@ app:get("all_topics", "", function(self)
     ORDER BY
       topics.sort_order ASC
   ]])
+  
+  local active_threads_raw = db.query([[
+    WITH ranked_threads AS (
+      SELECT
+        threads.topic_id, threads.id AS thread_id, threads.title AS thread_title, threads.slug AS thread_slug,
+        posts.id AS post_id, posts.created_at AS post_created_at,
+        users.username,
+        ROW_NUMBER() OVER (PARTITION BY threads.topic_id ORDER BY posts.created_at DESC) AS rn
+      FROM
+        threads
+      JOIN
+        posts ON threads.id = posts.thread_id
+      LEFT JOIN
+        users ON posts.user_id = users.id
+    )
+    SELECT
+      topic_id,
+      thread_id, thread_title, thread_slug,
+      post_id, post_created_at,
+      username
+    FROM
+      ranked_threads
+    WHERE
+      rn = 1
+    ORDER BY
+      topic_id
+  ]])
+   self.active_threads = {}
+   for _, thread in ipairs(active_threads_raw) do
+    self.active_threads[tonumber(thread.topic_id)] = {
+      thread_title = thread.thread_title,
+      thread_slug = thread.thread_slug,
+      post_id = thread.post_id,
+      username = thread.username,
+      post_created_at = thread.post_created_at,
+    }
+   end
+  
   self.me = util.get_logged_in_user_or_transient(self)
   return {render = "topics.topics"}
 end)

views/topics/topics.etlua

@@ -23,6 +23,12 @@
           <span>
             Latest thread: <a href="<%= url_for("thread", {slug = topic.latest_thread_slug}) %>"><%= topic.latest_thread_title %></a> by <a href="<%= url_for("user", {username = topic.latest_thread_username}) %>"><%= topic.latest_thread_username %></a> on <% render("views.common.timestamp", {timestamp = topic.latest_thread_created_at}) -%>
           </span>
+          <% if active_threads[topic.id] then %>
+            <% local thread = active_threads[topic.id] %>
+            <span>
+              Latest post in: <a href="<%= url_for("thread", {slug = thread.thread_slug}) %>"><%= thread.thread_title %></a> by <a href="<%= url_for("user", {username = thread.username}) %>"><%= thread.username %></a> at <a href="<%= get_post_url(thread.post_id) %>"><% render("views.common.timestamp", {timestamp = thread.post_created_at}) -%></a>
+            </span>
+          <% end %>
         <% else %>
         <i>No threads yet.</i>
         <% end %>