Extracted featured_users functionality out of Topic.

* Created a TopicFeatureUsers model
* Topic#featured_user_ids and Topic#feature_topic_users now delegate to
* a TopicFeatureUsers instance to keep demeter happy.

app/models/topic.rb

@@ -15,11 +15,19 @@ class Topic < ActiveRecord::Base
     2**31 - 1
   end
 
-  def self.featured_users_count
-    4
+  versioned if: :new_version_required?
+
+  def featured_users
+    @featured_users ||= TopicFeaturedUsers.new(self)
   end
 
-  versioned if: :new_version_required?
+  def featured_user_ids
+    featured_users.user_ids
+  end
+
+  def feature_topic_users(args={})
+    featured_users.choose(args)
+  end
 
   def trash!(trashed_by=nil)
     update_category_topic_count_by(-1) if deleted_at.nil?
@@ -368,9 +376,6 @@ class Topic < ActiveRecord::Base
     changed_to_category(cat)
   end
 
-  def featured_user_ids
-    [featured_user1_id, featured_user2_id, featured_user3_id, featured_user4_id].uniq.compact
-  end
 
   def remove_allowed_user(username)
     user = User.where(username: username).first
@@ -466,13 +471,6 @@ class Topic < ActiveRecord::Base
     end
   end
 
-  # Chooses which topic users to feature
-  def feature_topic_users(args={})
-    reload unless rails4?
-    clear_featured_users
-    update_featured_users featured_user_keys(args)
-    save
-  end
 
   def posters_summary(options = {})
     @posters_summary ||= TopicPostersSummary.new(self, options).summary
@@ -624,30 +622,6 @@ class Topic < ActiveRecord::Base
       end
     end
 
-    def featured_user_keys(args)
-      # Don't include the OP or the last poster
-      to_feature = posts.where('user_id NOT IN (?, ?)', user_id, last_post_user_id)
-
-      # Exclude a given post if supplied (in the case of deletes)
-      to_feature = to_feature.where("id <> ?", args[:except_post_id]) if args[:except_post_id].present?
-
-
-      # Assign the featured_user{x} columns
-      to_feature.group(:user_id).order('count_all desc').limit(Topic.featured_users_count).count.keys
-    end
-
-
-    def clear_featured_users
-      Topic.featured_users_count.times do |i|
-        send("featured_user#{i+1}_id=", nil)
-      end
-    end
-
-    def update_featured_users(user_keys)
-      user_keys.each_with_index do |user_id, i|
-        send("featured_user#{i+1}_id=", user_id)
-      end
-    end
 end
 
 # == Schema Information

app/models/topic_featured_users.rb

@@ -0,0 +1,51 @@
+class TopicFeaturedUsers
+  attr_reader :topic
+
+  def initialize(topic)
+    @topic = topic
+  end
+
+  def self.count
+    4
+  end
+
+  # Chooses which topic users to feature
+  def choose(args={})
+    topic.reload unless rails4?
+    clear
+    update keys(args)
+    topic.save
+  end
+
+  def user_ids
+    [topic.featured_user1_id, 
+     topic.featured_user2_id, 
+     topic.featured_user3_id, 
+     topic.featured_user4_id].uniq.compact
+  end
+
+  private
+
+    def keys(args)
+      # Don't include the OP or the last poster
+      to_feature = topic.posts.where('user_id NOT IN (?, ?)', topic.user_id, topic.last_post_user_id)
+
+      # Exclude a given post if supplied (in the case of deletes)
+      to_feature = to_feature.where("id <> ?", args[:except_post_id]) if args[:except_post_id].present?
+
+      # Assign the featured_user{x} columns
+      to_feature.group(:user_id).order('count_all desc').limit(TopicFeaturedUsers.count).count.keys
+    end
+
+    def clear
+      TopicFeaturedUsers.count.times do |i|
+        topic.send("featured_user#{i+1}_id=", nil)
+      end
+    end
+
+    def update(user_keys)
+      user_keys.each_with_index do |user_id, i|
+        topic.send("featured_user#{i+1}_id=", user_id)
+      end
+    end
+end