tag set presenter

app/presenters/post_set_presenters/post.rb

@@ -10,14 +10,38 @@ module PostSetPresenters
     
     def related_tags
       if post_set.is_single_tag?
-        tag = Tag.find_by_name(post_set.tag_string)
-        if tag
-          return tag.related_tag_array.map(&:first)
-        end
+        related_tags_for_single
+      elsif post_set.is_empty_tag?
+        popular_tags
+      else
+        related_tags_for_group
+      end
+    end
+    
+    def popular_tags
+      n = 1
+      results = []
+      
+      while results.empty? && n < 256
+        query = n.days.ago.strftime("date:>%Y-%m-%d")
+        results = RelatedTagCalculator.calculate_from_sample_to_array(query).map(&:first)
+        n *= 2
       end
       
+      results
+    end
+    
+    def related_tags_for_group
       RelatedTagCalculator.calculate_from_sample_to_array(post_set.tag_string).map(&:first)
     end
+    
+    def related_tags_for_single
+      tag = Tag.find_by_name(post_set.tag_string)
+
+      if tag
+        return tag.related_tag_array.map(&:first)
+      end
+    end
 
     def tag_list_html(template)
       tag_set_presenter.tag_list_html(template)