more work on paginators

app/logical/post_sets/base.rb

@@ -0,0 +1,37 @@
+module PostSets
+  class Base
+    def has_wiki?
+      false
+    end
+    
+    def wiki_page
+      nil
+    end
+    
+    def presenter
+      @presenter ||= PostSetPresenter.new(self)
+    end
+    
+    def is_single_tag?
+      false
+    end
+    
+    def tag
+      tag_string
+    end
+    
+    def arbitrary_sql_order_clause(ids, table_name)
+      if ids.empty?
+        return "#{table_name}.id desc"
+      end
+      
+      conditions = []
+      
+      ids.each_with_index do |x, n|
+        conditions << "when #{x} then #{n}"
+      end
+      
+      "case #{table_name}.id " + conditions.join(" ") + " end"
+    end
+  end
+end