Fix bugs for shift_to and change items.rake for the missing position in db

app/controllers/admin/items_controller.rb

@@ -17,6 +17,8 @@ class Admin::ItemsController < ApplicationController
   end
 
   def update_position
+    item = Item.find(params[:id])
+    item.shift_to(params[:parent_id], params[:position])
     render :nothing => true
   end
   

app/models/item.rb

@@ -36,12 +36,29 @@ class Item
     a
   end
 
+  def shift_to(new_parent, position)
+    unless self.parent_id.to_s.eql?(new_parent) && self.position.eql?(position.to_i)
+      new_parent = Item.find(new_parent)
+      current_position_sibling = find_by_parent_and_position(new_parent, position.to_i)
+      if current_position_sibling
+        current_position_sibling.at_bottom? ? move_below(current_position_sibling) : move_above(current_position_sibling)
+      elsif self.parent != new_parent
+        self.parent = new_parent
+        save!
+      end
+    end
+   end
+  
   protected
   
   def rebuild_path
     self.path = (self.ancestors_and_self - [Item.root]).collect{|x| x.name unless x.root?}.join('/')
   end
 
+  def find_by_parent_and_position(parent, position)
+    parent.children.detect{|child| child.position == position}
+  end
+
   # Enable the validation for parent_id
   def validates_presence_of_parent_id?
     true

lib/tasks/items.rake

@@ -3,7 +3,7 @@
 namespace :items do
   task :tree_changes => :environment do
   	Item.all.each do |item|
-  		item.position -= 1
+  		item.position -= item.position > 5 ? 2 : 1
   		item.parent_ids = ancestors(item)
   		item.rename(:full_name, :path)
   		item.save