first stab at calculating the score of a topic for the top tab

app/controllers/list_controller.rb

@@ -73,8 +73,7 @@ class ListController < ApplicationController
   end
 
   def top
-    sort_order = params[:sort_order] || "posts"
-    top = generate_top_lists_by(sort_order)
+    top = generate_top_lists
 
     respond_to do |format|
       format.html do
@@ -179,7 +178,7 @@ class ListController < ApplicationController
     public_send(method, opts.merge(next_page_params(opts)))
   end
 
-  def generate_top_lists_by(sort_order)
+  def generate_top_lists
     top = {}
     topic_ids = Set.new
 
@@ -188,7 +187,7 @@ class ListController < ApplicationController
         per_page: SiteSetting.topics_per_period_in_summary,
         except_topic_ids: topic_ids.to_a
       }
-      list = TopicQuery.new(current_user, options).list_top(sort_order, period)
+      list = TopicQuery.new(current_user, options).list_top_for(period)
       topic_ids.merge(list.topic_ids)
       top[period] = list
     end

app/models/top_topic.rb

@@ -20,12 +20,17 @@ class TopTopic < ActiveRecord::Base
                 FROM topics
                 WHERE deleted_at IS NULL
                 AND visible
-                AND NOT archived")
-      # update all the counter caches
+                AND archetype <> :private_message
+                AND NOT archived",
+                private_message: Archetype::private_message)
+
       TopTopic.periods.each do |period|
+        # update all the counter caches
         TopTopic.sort_orders.each do |sort|
           TopTopic.send("update_#{sort}_count_for", period)
         end
+        # compute top score
+        TopTopic.compute_top_score_for(period)
       end
     end
   end
@@ -61,6 +66,16 @@ class TopTopic < ActiveRecord::Base
     TopTopic.update_top_topics(period, "likes", sql)
   end
 
+  def self.compute_top_score_for(period)
+    exec_sql("UPDATE top_topics
+              SET #{period}_score = log(
+                1 +
+                (#{period}_posts_count) *
+                (#{period}_likes_count / 2.0 + 1.0) *
+                (#{period}_views_count / 100.0 + 1.0)
+              )")
+  end
+
   def self.start_of(period)
     case period
       when :yearly  then 1.year.ago

db/migrate/20131227164338_add_scores_to_top_topics.rb

@@ -0,0 +1,7 @@
+class AddScoresToTopTopics < ActiveRecord::Migration
+  def change
+    TopTopic.periods.each do |period|
+      add_column :top_topics, "#{period}_score".to_sym, :float
+    end
+  end
+end

lib/topic_query.rb

@@ -84,12 +84,11 @@ class TopicQuery
     create_list(:posted) {|l| l.where('tu.user_id IS NOT NULL') }
   end
 
-  def list_top(sort_order, period)
-    count = "#{period}_#{sort_order}_count"
+  def list_top_for(period)
+    score = "#{period}_score"
     create_list(:top, unordered: true) do |topics|
       topics.joins(:top_topic)
-            .where("top_topics.#{count} > 0")
-            .order("top_topics.#{count} DESC, topics.bumped_at DESC")
+            .order("top_topics.#{score} DESC, topics.bumped_at DESC")
     end
   end