work in progress wide category list

app/models/category_list.rb

@@ -8,10 +8,11 @@ class CategoryList
                 :draft_key,
                 :draft_sequence
 
-  def initialize(guardian=nil)
+  def initialize(guardian=nil, options = {})
     @guardian = guardian || Guardian.new
+    @options = options
 
-    find_relevant_topics
+    find_relevant_topics unless latest_post_only?
     find_categories
 
     prune_empty
@@ -21,6 +22,10 @@ class CategoryList
 
   private
 
+    def latest_post_only?
+      @options[:latest_post_only]
+    end
+
     # Retrieve a list of all the topics we'll need
     def find_relevant_topics
       @topics_by_category_id = {}
@@ -47,16 +52,35 @@ class CategoryList
                       .order('COALESCE(categories.topics_month, 0) DESC')
                       .order('COALESCE(categories.topics_year, 0) DESC')
 
+      if latest_post_only?
+        @categories = @categories.includes(:latest_post => :topic )
+      end
+
       @categories = @categories.to_a
-      @categories.each do |c|
-        topics_in_cat = @topics_by_category_id[c.id]
-        if topics_in_cat.present?
-          c.displayable_topics = []
-          topics_in_cat.each do |topic_id|
-            topic = @topics_by_id[topic_id]
-            if topic.present?
-              topic.category = c
-              c.displayable_topics << topic
+
+      if latest_post_only?
+        @all_topics = []
+        @categories.each do |c|
+          if c.latest_post && c.latest_post.topic
+            c.displayable_topics = [c.latest_post.topic]
+            topic = c.latest_post.topic
+            topic.include_last_poster = true # hint for serialization
+            @all_topics << topic
+          end
+        end
+      end
+
+      if @topics_by_category_id
+        @categories.each do |c|
+          topics_in_cat = @topics_by_category_id[c.id]
+          if topics_in_cat.present?
+            c.displayable_topics = []
+            topics_in_cat.each do |topic_id|
+              topic = @topics_by_id[topic_id]
+              if topic.present?
+                topic.category = c
+                c.displayable_topics << topic
+              end
             end
           end
         end