Refactor Version to use some named scopes.

lib/paper_trail/version.rb

@@ -2,6 +2,20 @@ class Version < ActiveRecord::Base
   belongs_to :item, :polymorphic => true
   validates_presence_of :event
 
+  named_scope :with_item_keys, lambda { |item_type, item_id| {
+    :conditions => { :item_type => item_type, :item_id => item_id }
+  } }
+
+  named_scope :subsequent, lambda { |version| {
+    :conditions => ["id > ?", version.is_a?(ActiveRecord::Base) ? version.id : version],
+    :order      => "id ASC",
+  } }
+
+  named_scope :preceding, lambda { |version| {
+    :conditions => ["id < ?", version.is_a?(ActiveRecord::Base) ? version.id : version],
+    :order      => "id DESC",
+  } }
+
   # Restore the item from this version.
   #
   # This will automatically restore all :has_one associations as they were "at the time",
@@ -69,19 +83,20 @@ class Version < ActiveRecord::Base
     whodunnit
   end
 
+  def sibling_versions
+    Version.with_item_keys(item_type, item_id)
+  end
+
   def next
-    Version.first :conditions => ["id > ? AND item_type = ? AND item_id = ?", id, item_type, item_id],
-                  :order => 'id ASC'
+    sibling_versions.subsequent(self).first
   end
 
   def previous
-    Version.first :conditions => ["id < ? AND item_type = ? AND item_id = ?", id, item_type, item_id],
-                  :order => 'id DESC'
+    sibling_versions.preceding(self).first
   end
 
   def index
-    Version.all(:conditions => ["item_type = ? AND item_id = ?", item_type, item_id],
-                :order => 'id ASC').index(self)
+    sibling_versions.all(:select => :id, :order => "id ASC").map(&:id).index(self.id)
   end
 
   private