awesome_nested_set: import git 2-1-stable branch revision 606847769 (#6579)

https://github.com/collectiveidea/awesome_nested_set/commit/606847769

git-svn-id: http://svn.redmine.org/redmine/trunk@13143 e93f8b46-1217-0410-a6f0-8f06a7374b81

26 files changed, 1278 insertions, 918 deletions

diff --git a/lib/plugins/awesome_nested_set/.travis.yml b/lib/plugins/awesome_nested_set/.travis.yml
index 23152319f..0456da4fa 100644
--- a/lib/plugins/awesome_nested_set/.travis.yml
+++ b/lib/plugins/awesome_nested_set/.travis.yml
@@ -1,7 +1,4 @@
 language: ruby
-notifications:
-  email:
-    - parndt@gmail.com
 script: bundle exec rspec spec
 env:
   - DB=sqlite3
@@ -11,9 +8,9 @@ env:
 rvm:
   - 2.0.0
   - 1.9.3
-  - 1.8.7
   - rbx-19mode
   - jruby-19mode
+  - 1.8.7
   - rbx-18mode
   - jruby-18mode
 gemfile:
diff --git a/lib/plugins/awesome_nested_set/CONTRIBUTING.md b/lib/plugins/awesome_nested_set/CONTRIBUTING.md
new file mode 100644
index 000000000..112b942ef
--- /dev/null
+++ b/lib/plugins/awesome_nested_set/CONTRIBUTING.md
@@ -0,0 +1,14 @@
+# Contributing to AwesomeNestedSet
+
+If you find what you might think is a bug:
+
+1. Check the [GitHub issue tracker](https://github.com/collectiveidea/awesome_nested_set/issues/) to see if anyone else has had the same issue.
+2. If you don't see anything, create an issue with information on how to reproduce it.
+
+If you want to contribute an enhancement or a fix:
+
+1. Fork [the project on GitHub](https://github.com/collectiveidea/awesome_nested_set)
+2. Make your changes with tests.
+3. Commit the changes without making changes to the [Rakefile](Rakefile) or any other files that aren't related to your enhancement or fix.
+4. Write an entry in the [CHANGELOG](CHANGELOG)
+5. Send a pull request.
diff --git a/lib/plugins/awesome_nested_set/Gemfile b/lib/plugins/awesome_nested_set/Gemfile
index c644eb148..cf7cf11fe 100644
--- a/lib/plugins/awesome_nested_set/Gemfile
+++ b/lib/plugins/awesome_nested_set/Gemfile
@@ -1,4 +1,4 @@
-gem 'combustion', :github => 'pat/combustion'
+gem 'combustion', :github => 'pat/combustion', :branch => 'master'
 
 source 'https://rubygems.org'
 
@@ -7,6 +7,7 @@ gemspec :path => File.expand_path('../', __FILE__)
 platforms :jruby do
   gem 'activerecord-jdbcsqlite3-adapter'
   gem 'activerecord-jdbcmysql-adapter'
+  gem 'jdbc-mysql'
   gem 'activerecord-jdbcpostgresql-adapter'
   gem 'jruby-openssl'
 end
@@ -27,5 +28,5 @@ gem 'actionpack', RAILS_VERSION
 # gem 'activerecord-oracle_enhanced-adapter'
 
 # Debuggers
-# gem 'pry'
-# gem 'pry-nav'
+gem 'pry'
+gem 'pry-nav'
diff --git a/lib/plugins/awesome_nested_set/README.md b/lib/plugins/awesome_nested_set/README.md
new file mode 100644
index 000000000..58bb86ee5
--- /dev/null
+++ b/lib/plugins/awesome_nested_set/README.md
@@ -0,0 +1,163 @@
+# AwesomeNestedSet
+
+Awesome Nested Set is an implementation of the nested set pattern for ActiveRecord models.
+It is a replacement for acts_as_nested_set and BetterNestedSet, but more awesome.
+
+Version 2 supports Rails 3. Gem versions prior to 2.0 support Rails 2.
+
+## What makes this so awesome?
+
+This is a new implementation of nested set based off of BetterNestedSet that fixes some bugs, removes tons of duplication, adds a few useful methods, and adds STI support.
+
+[![Code Climate](https://codeclimate.com/github/collectiveidea/awesome_nested_set.png)](https://codeclimate.com/github/collectiveidea/awesome_nested_set)
+
+## Installation
+
+Add to your Gemfile:
+
+```ruby
+gem 'awesome_nested_set'
+```
+
+## Usage
+
+To make use of `awesome_nested_set`, your model needs to have 3 fields:
+`lft`, `rgt`, and `parent_id`. The names of these fields are configurable.
+You can also have an optional field, `depth`:
+
+```ruby
+class CreateCategories < ActiveRecord::Migration
+  def self.up
+    create_table :categories do |t|
+      t.string :name
+      t.integer :parent_id
+      t.integer :lft
+      t.integer :rgt
+      t.integer :depth # this is optional.
+    end
+  end
+
+  def self.down
+    drop_table :categories
+  end
+end
+```
+
+Enable the nested set functionality by declaring `acts_as_nested_set` on your model
+
+```ruby
+class Category < ActiveRecord::Base
+  acts_as_nested_set
+end
+```
+
+Run `rake rdoc` to generate the API docs and see [CollectiveIdea::Acts::NestedSet](lib/awesome_nested_set/awesome_nested_set.rb) for more information.
+
+## Callbacks
+
+There are three callbacks called when moving a node:
+`before_move`, `after_move` and `around_move`.
+
+```ruby
+class Category < ActiveRecord::Base
+  acts_as_nested_set
+
+  after_move :rebuild_slug
+  around_move :da_fancy_things_around
+
+  private
+
+  def rebuild_slug
+    # do whatever
+  end
+
+  def da_fancy_things_around
+    # do something...
+    yield # actually moves
+    # do something else...
+  end
+end
+```
+
+Beside this there are also hooks to act on the newly added or removed children.
+
+```ruby
+class Category < ActiveRecord::Base
+  acts_as_nested_set  :before_add     => :do_before_add_stuff,
+                      :after_add      => :do_after_add_stuff,
+                      :before_remove  => :do_before_remove_stuff,
+                      :after_remove   => :do_after_remove_stuff
+
+  private
+
+  def do_before_add_stuff(child_node)
+    # do whatever with the child
+  end
+
+  def do_after_add_stuff(child_node)
+    # do whatever with the child
+  end
+
+  def do_before_remove_stuff(child_node)
+    # do whatever with the child
+  end
+
+  def do_after_remove_stuff(child_node)
+    # do whatever with the child
+  end
+end
+```
+
+## Protecting attributes from mass assignment
+
+It's generally best to "whitelist" the attributes that can be used in mass assignment:
+
+```ruby
+class Category < ActiveRecord::Base
+  acts_as_nested_set
+  attr_accessible :name, :parent_id
+end
+```
+
+If for some reason that is not possible, you will probably want to protect the `lft` and `rgt` attributes:
+
+```ruby
+class Category < ActiveRecord::Base
+  acts_as_nested_set
+  attr_protected :lft, :rgt
+end
+```
+
+## Conversion from other trees
+
+Coming from acts_as_tree or another system where you only have a parent_id? No problem. Simply add the lft & rgt fields as above, and then run:
+
+```ruby
+Category.rebuild!
+```
+
+Your tree will be converted to a valid nested set. Awesome!
+
+## View Helper
+
+The view helper is called #nested_set_options.
+
+Example usage:
+
+```erb
+<%= f.select :parent_id, nested_set_options(Category, @category) {|i| "#{'-' * i.level} #{i.name}" } %>
+
+<%= select_tag 'parent_id', options_for_select(nested_set_options(Category) {|i| "#{'-' * i.level} #{i.name}" } ) %>
+```
+
+See [CollectiveIdea::Acts::NestedSet::Helper](lib/awesome_nested_set/helper.rb) for more information about the helpers.
+
+## References
+
+You can learn more about nested sets at: http://threebit.net/tutorials/nestedset/tutorial1.html
+
+## How to contribute
+
+Please see the ['Contributing' document](CONTRIBUTING.md).
+
+Copyright © 2008 - 2013 Collective Idea, released under the MIT license
diff --git a/lib/plugins/awesome_nested_set/README.rdoc b/lib/plugins/awesome_nested_set/README.rdoc
deleted file mode 100644
index 2ba2128ec..000000000
--- a/lib/plugins/awesome_nested_set/README.rdoc
+++ /dev/null
@@ -1,153 +0,0 @@
-= AwesomeNestedSet
-
-Awesome Nested Set is an implementation of the nested set pattern for ActiveRecord models. It is replacement for acts_as_nested_set and BetterNestedSet, but more awesome.
-
-Version 2 supports Rails 3. Gem versions prior to 2.0 support Rails 2.
-
-== What makes this so awesome?
-
-This is a new implementation of nested set based off of BetterNestedSet that fixes some bugs, removes tons of duplication, adds a few useful methods, and adds STI support.
-
-== Installation
-
-  Add to your Gemfile:
-
-  gem 'awesome_nested_set'
-
-== Usage
-
-To make use of awesome_nested_set, your model needs to have 3 fields: lft, rgt, and parent_id.
-You can also have an optional field: depth:
-
-  class CreateCategories < ActiveRecord::Migration
-    def self.up
-      create_table :categories do |t|
-        t.string :name
-        t.integer :parent_id
-        t.integer :lft
-        t.integer :rgt
-        t.integer :depth # this is optional.
-      end
-    end
-
-    def self.down
-      drop_table :categories
-    end
-  end
-
-Enable the nested set functionality by declaring acts_as_nested_set on your model
-
-  class Category < ActiveRecord::Base
-    acts_as_nested_set
-  end
-
-Run `rake rdoc` to generate the API docs and see CollectiveIdea::Acts::NestedSet for more info.
-
-== Callbacks
-
-There are three callbacks called when moving a node. `before_move`, `after_move` and `around_move`.
-
-  class Category < ActiveRecord::Base
-    acts_as_nested_set
-
-    after_move :rebuild_slug
-    around_move :da_fancy_things_around
-
-    private
-    
-    def rebuild_slug
-      # do whatever
-    end
-
-    def da_fancy_things_around
-      # do something...
-      yield # actually moves
-      # do something else...
-    end
-  end
-
-Beside this there are also hooks to act on the newly added or removed children.
-
-  class Category < ActiveRecord::Base  
-    acts_as_nested_set  :before_add     => :do_before_add_stuff,
-                        :after_add      => :do_after_add_stuff,
-                        :before_remove  => :do_before_remove_stuff,
-                        :after_remove   => :do_after_remove_stuff
-
-    private
-
-    def do_before_add_stuff(child_node)
-      # do whatever with the child
-    end
-
-    def do_after_add_stuff(child_node)
-      # do whatever with the child
-    end
-
-    def do_before_remove_stuff(child_node)
-      # do whatever with the child
-    end
-
-    def do_after_remove_stuff(child_node)
-      # do whatever with the child
-    end
-  end
-
-
-== Protecting attributes from mass assignment
-
-It's generally best to "white list" the attributes that can be used in mass assignment:
-
-  class Category < ActiveRecord::Base
-    acts_as_nested_set
-    attr_accessible :name, :parent_id
-  end
-
-If for some reason that is not possible, you will probably want to protect the lft and rgt attributes:
-
-  class Category < ActiveRecord::Base
-    acts_as_nested_set
-    attr_protected :lft, :rgt
-  end
-
-== Conversion from other trees
-
-Coming from acts_as_tree or another system where you only have a parent_id? No problem. Simply add the lft & rgt fields as above, and then run
-
-  Category.rebuild!
-
-Your tree will be converted to a valid nested set. Awesome!
-
-== View Helper
-
-The view helper is called #nested_set_options.
-
-Example usage:
-
-  <%= f.select :parent_id, nested_set_options(Category, @category) {|i| "#{'-' * i.level} #{i.name}" } %>
-
-  <%= select_tag 'parent_id', options_for_select(nested_set_options(Category) {|i| "#{'-' * i.level} #{i.name}" } ) %>
-
-See CollectiveIdea::Acts::NestedSet::Helper for more information about the helpers.
-
-== References
-
-You can learn more about nested sets at: http://threebit.net/tutorials/nestedset/tutorial1.html
-
-== How to contribute
-
-If you find what you might think is a bug:
-
-1. Check the GitHub issue tracker to see if anyone else has had the same issue.
-   https://github.com/collectiveidea/awesome_nested_set/issues/
-2. If you don't see anything, create an issue with information on how to reproduce it.
-
-If you want to contribute an enhancement or a fix:
-
-1. Fork the project on GitHub.
-   https://github.com/collectiveidea/awesome_nested_set/
-2. Make your changes with tests.
-3. Commit the changes without making changes to the Rakefile, VERSION, or any other files that aren't related to your enhancement or fix
-4. Send a pull request.
-
-Copyright ©2008 Collective Idea, released under the MIT license
diff --git a/lib/plugins/awesome_nested_set/awesome_nested_set.gemspec b/lib/plugins/awesome_nested_set/awesome_nested_set.gemspec
index f30dcc611..f4f858efc 100644
--- a/lib/plugins/awesome_nested_set/awesome_nested_set.gemspec
+++ b/lib/plugins/awesome_nested_set/awesome_nested_set.gemspec
@@ -7,10 +7,9 @@ Gem::Specification.new do |s|
   s.authors = ["Brandon Keepers", "Daniel Morrison", "Philip Arndt"]
   s.description = %q{An awesome nested set implementation for Active Record}
   s.email = %q{info@collectiveidea.com}
-  s.extra_rdoc_files = %w[README.rdoc]
-  s.files = Dir.glob("lib/**/*") + %w(MIT-LICENSE README.rdoc CHANGELOG)
+  s.files = Dir.glob("lib/**/*") + %w(MIT-LICENSE README.md CHANGELOG)
   s.homepage = %q{http://github.com/collectiveidea/awesome_nested_set}
-  s.rdoc_options = ["--main", "README.rdoc", "--inline-source", "--line-numbers"]
+  s.rdoc_options = ["--inline-source", "--line-numbers"]
   s.require_paths = ["lib"]
   s.rubygems_version = %q{1.3.6}
   s.summary = %q{An awesome nested set implementation for Active Record}
@@ -21,4 +20,5 @@ Gem::Specification.new do |s|
   s.add_development_dependency 'rspec-rails', '~> 2.12'
   s.add_development_dependency 'rake', '~> 10'
   s.add_development_dependency 'combustion', '>= 0.3.3'
+  s.add_development_dependency 'database_cleaner'
 end
diff --git a/lib/plugins/awesome_nested_set/init.rb b/lib/plugins/awesome_nested_set/init.rb
deleted file mode 100644
index 8e2cf36ef..000000000
--- a/lib/plugins/awesome_nested_set/init.rb
+++ /dev/null
@@ -1 +0,0 @@
-require File.dirname(__FILE__) + '/lib/awesome_nested_set'
diff --git a/lib/plugins/awesome_nested_set/lib/awesome_nested_set.rb b/lib/plugins/awesome_nested_set/lib/awesome_nested_set.rb
index a3df9e467..37ae5170d 100644
--- a/lib/plugins/awesome_nested_set/lib/awesome_nested_set.rb
+++ b/lib/plugins/awesome_nested_set/lib/awesome_nested_set.rb
@@ -5,4 +5,4 @@ ActiveRecord::Base.send :extend, CollectiveIdea::Acts::NestedSet
 if defined?(ActionView)
   require 'awesome_nested_set/helper'
   ActionView::Base.send :include, CollectiveIdea::Acts::NestedSet::Helper
-end
\ No newline at end of file
+end
diff --git a/lib/plugins/awesome_nested_set/lib/awesome_nested_set/awesome_nested_set.rb b/lib/plugins/awesome_nested_set/lib/awesome_nested_set/awesome_nested_set.rb
index 4cb527762..95c3516c1 100644
--- a/lib/plugins/awesome_nested_set/lib/awesome_nested_set/awesome_nested_set.rb
+++ b/lib/plugins/awesome_nested_set/lib/awesome_nested_set/awesome_nested_set.rb
@@ -1,3 +1,6 @@
+require 'awesome_nested_set/columns'
+require 'awesome_nested_set/model'
+
 module CollectiveIdea #:nodoc:
   module Acts #:nodoc:
     module NestedSet #:nodoc:
@@ -42,731 +45,89 @@ module CollectiveIdea #:nodoc:
       # CollectiveIdea::Acts::NestedSet::Model for a list of instance methods added
       # to acts_as_nested_set models
       def acts_as_nested_set(options = {})
-        options = {
-          :parent_column => 'parent_id',
-          :left_column => 'lft',
-          :right_column => 'rgt',
-          :depth_column => 'depth',
-          :dependent => :delete_all, # or :destroy
-          :polymorphic => false,
-          :counter_cache => false
-        }.merge(options)
-
-        if options[:scope].is_a?(Symbol) && options[:scope].to_s !~ /_id$/
-          options[:scope] = "#{options[:scope]}_id".intern
-        end
-
-        class_attribute :acts_as_nested_set_options
-        self.acts_as_nested_set_options = options
+        acts_as_nested_set_parse_options! options
 
-        include CollectiveIdea::Acts::NestedSet::Model
+        include Model
         include Columns
         extend Columns
 
-        belongs_to :parent, :class_name => self.base_class.to_s,
-                            :foreign_key => parent_column_name,
-                            :counter_cache => options[:counter_cache],
-                            :inverse_of => (:children unless options[:polymorphic]),
-                            :polymorphic => options[:polymorphic]
-
-        has_many_children_options = {
-          :class_name => self.base_class.to_s,
-          :foreign_key => parent_column_name,
-          :order => order_column,
-          :inverse_of => (:parent unless options[:polymorphic]),
-        }
-
-        # Add callbacks, if they were supplied.. otherwise, we don't want them.
-        [:before_add, :after_add, :before_remove, :after_remove].each do |ar_callback|
-          has_many_children_options.update(ar_callback => options[ar_callback]) if options[ar_callback]
-        end
-
-        has_many :children, has_many_children_options
+        acts_as_nested_set_relate_parent!
+        acts_as_nested_set_relate_children!
 
         attr_accessor :skip_before_destroy
 
+        acts_as_nested_set_prevent_assignment_to_reserved_columns!
+        acts_as_nested_set_define_callbacks!
+      end
+
+      private
+      def acts_as_nested_set_define_callbacks!
+        # on creation, set automatically lft and rgt to the end of the tree
         before_create  :set_default_left_and_right
         before_save    :store_new_parent
         after_save     :move_to_new_parent, :set_depth!
         before_destroy :destroy_descendants
 
-        # no assignment to structure fields
-        [left_column_name, right_column_name, depth_column_name].each do |column|
-          module_eval <<-"end_eval", __FILE__, __LINE__
-            def #{column}=(x)
-              raise ActiveRecord::ActiveRecordError, "Unauthorized assignment to #{column}: it's an internal field handled by acts_as_nested_set code, use move_to_* methods instead."
-            end
-          end_eval
-        end
-
         define_model_callbacks :move
       end
 
-      module Model
-        extend ActiveSupport::Concern
-
-        included do
-          delegate :quoted_table_name, :to => self
-        end
-
-        module ClassMethods
-          # Returns the first root
-          def root
-            roots.first
-          end
-
-          def roots
-            where(parent_column_name => nil).order(quoted_left_column_full_name)
-          end
-
-          def leaves
-            where("#{quoted_right_column_full_name} - #{quoted_left_column_full_name} = 1").order(quoted_left_column_full_name)
-          end
-
-          def valid?
-            left_and_rights_valid? && no_duplicates_for_columns? && all_roots_valid?
-          end
-
-          def left_and_rights_valid?
-            ## AS clause not supported in Oracle in FROM clause for aliasing table name
-            joins("LEFT OUTER JOIN #{quoted_table_name}" +
-                (connection.adapter_name.match(/Oracle/).nil? ?  " AS " : " ") +
-                "parent ON " +
-                "#{quoted_parent_column_full_name} = parent.#{primary_key}").
-            where(
-                "#{quoted_left_column_full_name} IS NULL OR " +
-                "#{quoted_right_column_full_name} IS NULL OR " +
-                "#{quoted_left_column_full_name} >= " +
-                  "#{quoted_right_column_full_name} OR " +
-                "(#{quoted_parent_column_full_name} IS NOT NULL AND " +
-                  "(#{quoted_left_column_full_name} <= parent.#{quoted_left_column_name} OR " +
-                  "#{quoted_right_column_full_name} >= parent.#{quoted_right_column_name}))"
-            ).count == 0
-          end
-
-          def no_duplicates_for_columns?
-            scope_string = Array(acts_as_nested_set_options[:scope]).map do |c|
-              connection.quote_column_name(c)
-            end.push(nil).join(", ")
-            [quoted_left_column_full_name, quoted_right_column_full_name].all? do |column|
-              # No duplicates
-              select("#{scope_string}#{column}, COUNT(#{column})").
-                  group("#{scope_string}#{column}").
-                  having("COUNT(#{column}) > 1").
-                  first.nil?
-            end
-          end
-
-          # Wrapper for each_root_valid? that can deal with scope.
-          def all_roots_valid?
-            if acts_as_nested_set_options[:scope]
-              roots.group_by {|record| scope_column_names.collect {|col| record.send(col.to_sym) } }.all? do |scope, grouped_roots|
-                each_root_valid?(grouped_roots)
-              end
-            else
-              each_root_valid?(roots)
-            end
-          end
-
-          def each_root_valid?(roots_to_validate)
-            left = right = 0
-            roots_to_validate.all? do |root|
-              (root.left > left && root.right > right).tap do
-                left = root.left
-                right = root.right
-              end
-            end
-          end
-
-          # Rebuilds the left & rights if unset or invalid.
-          # Also very useful for converting from acts_as_tree.
-          def rebuild!(validate_nodes = true)
-            # default_scope with order may break database queries so we do all operation without scope
-            unscoped do
-              # Don't rebuild a valid tree.
-              return true if valid?
-
-              scope = lambda{|node|}
-              if acts_as_nested_set_options[:scope]
-                scope = lambda{|node|
-                  scope_column_names.inject(""){|str, column_name|
-                    str << "AND #{connection.quote_column_name(column_name)} = #{connection.quote(node.send(column_name.to_sym))} "
-                  }
-                }
-              end
-              indices = {}
-
-              set_left_and_rights = lambda do |node|
-                # set left
-                node[left_column_name] = indices[scope.call(node)] += 1
-                # find
-                where(["#{quoted_parent_column_full_name} = ? #{scope.call(node)}", node]).order("#{quoted_left_column_full_name}, #{quoted_right_column_full_name}, id").each{|n| set_left_and_rights.call(n) }
-                # set right
-                node[right_column_name] = indices[scope.call(node)] += 1
-                node.save!(:validate => validate_nodes)
-              end
-
-              # Find root node(s)
-              root_nodes = where("#{quoted_parent_column_full_name} IS NULL").order("#{quoted_left_column_full_name}, #{quoted_right_column_full_name}, id").each do |root_node|
-                # setup index for this scope
-                indices[scope.call(root_node)] ||= 0
-                set_left_and_rights.call(root_node)
-              end
-            end
-          end
-
-          # Iterates over tree elements and determines the current level in the tree.
-          # Only accepts default ordering, odering by an other column than lft
-          # does not work. This method is much more efficent than calling level
-          # because it doesn't require any additional database queries.
-          #
-          # Example:
-          #    Category.each_with_level(Category.root.self_and_descendants) do |o, level|
-          #
-          def each_with_level(objects)
-            path = [nil]
-            objects.each do |o|
-              if o.parent_id != path.last
-                # we are on a new level, did we descend or ascend?
-                if path.include?(o.parent_id)
-                  # remove wrong wrong tailing paths elements
-                  path.pop while path.last != o.parent_id
-                else
-                  path << o.parent_id
-                end
-              end
-              yield(o, path.length - 1)
-            end
-          end
-
-          # Same as each_with_level - Accepts a string as a second argument to sort the list
-          # Example:
-          #    Category.each_with_level(Category.root.self_and_descendants, :sort_by_this_column) do |o, level|
-          def sorted_each_with_level(objects, order)
-            path = [nil]
-            children = []
-              objects.each do |o|
-              children << o if o.leaf?
-              if o.parent_id != path.last
-                if !children.empty? && !o.leaf?
-                  children.sort_by! &order
-                  children.each { |c| yield(c, path.length-1) }
-                  children = []
-                end
-                # we are on a new level, did we decent or ascent?
-                if path.include?(o.parent_id)
-                  # remove wrong wrong tailing paths elements
-                  path.pop while path.last != o.parent_id
-                else
-                  path << o.parent_id
-                end
-              end
-              yield(o,path.length-1) if !o.leaf?
-            end
-            if !children.empty?
-              children.sort_by! &order
-              children.each { |c| yield(c, path.length-1) }
-            end
-          end
-
-          def associate_parents(objects)
-            if objects.all?{|o| o.respond_to?(:association)}
-              id_indexed = objects.index_by(&:id)
-              objects.each do |object|
-                if !(association = object.association(:parent)).loaded? && (parent = id_indexed[object.parent_id])
-                  association.target = parent
-                  association.set_inverse_instance(parent)
-                end
-              end
-            else
-              objects
-            end
-          end
-        end
-
-        # Any instance method that returns a collection makes use of Rails 2.1's named_scope (which is bundled for Rails 2.0), so it can be treated as a finder.
-        #
-        #   category.self_and_descendants.count
-        #   category.ancestors.find(:all, :conditions => "name like '%foo%'")
-        # Value of the parent column
-        def parent_id
-          self[parent_column_name]
-        end
-
-        # Value of the left column
-        def left
-          self[left_column_name]
-        end
-
-        # Value of the right column
-        def right
-          self[right_column_name]
-        end
-
-        # Returns true if this is a root node.
-        def root?
-          parent_id.nil?
-        end
-
-        # Returns true if this is the end of a branch.
-        def leaf?
-          persisted? && right.to_i - left.to_i == 1
-        end
-
-        # Returns true is this is a child node
-        def child?
-          !root?
-        end
-
-        # Returns root
-        def root
-          if persisted?
-            self_and_ancestors.where(parent_column_name => nil).first
-          else
-            if parent_id && current_parent = nested_set_scope.find(parent_id)
-              current_parent.root
-            else
-              self
-            end
-          end
-        end
-
-        # Returns the array of all parents and self
-        def self_and_ancestors
-          nested_set_scope.where([
-            "#{quoted_left_column_full_name} <= ? AND #{quoted_right_column_full_name} >= ?", left, right
-          ])
-        end
-
-        # Returns an array of all parents
-        def ancestors
-          without_self self_and_ancestors
-        end
-
-        # Returns the array of all children of the parent, including self
-        def self_and_siblings
-          nested_set_scope.where(parent_column_name => parent_id)
-        end
-
-        # Returns the array of all children of the parent, except self
-        def siblings
-          without_self self_and_siblings
-        end
-
-        # Returns a set of all of its nested children which do not have children
-        def leaves
-          descendants.where("#{quoted_right_column_full_name} - #{quoted_left_column_full_name} = 1")
-        end
-
-        # Returns the level of this object in the tree
-        # root level is 0
-        def level
-          parent_id.nil? ? 0 : compute_level
-        end
-
-        # Returns a set of itself and all of its nested children
-        def self_and_descendants
-          nested_set_scope.where([
-            "#{quoted_left_column_full_name} >= ? AND #{quoted_left_column_full_name} < ?", left, right
-            # using _left_ for both sides here lets us benefit from an index on that column if one exists
-          ])
-        end
-
-        # Returns a set of all of its children and nested children
-        def descendants
-          without_self self_and_descendants
-        end
-
-        def is_descendant_of?(other)
-          other.left < self.left && self.left < other.right && same_scope?(other)
-        end
-
-        def is_or_is_descendant_of?(other)
-          other.left <= self.left && self.left < other.right && same_scope?(other)
-        end
-
-        def is_ancestor_of?(other)
-          self.left < other.left && other.left < self.right && same_scope?(other)
-        end
-
-        def is_or_is_ancestor_of?(other)
-          self.left <= other.left && other.left < self.right && same_scope?(other)
-        end
-
-        # Check if other model is in the same scope
-        def same_scope?(other)
-          Array(acts_as_nested_set_options[:scope]).all? do |attr|
-            self.send(attr) == other.send(attr)
-          end
-        end
-
-        # Find the first sibling to the left
-        def left_sibling
-          siblings.where(["#{quoted_left_column_full_name} < ?", left]).
-                  order("#{quoted_left_column_full_name} DESC").last
-        end
-
-        # Find the first sibling to the right
-        def right_sibling
-          siblings.where(["#{quoted_left_column_full_name} > ?", left]).first
-        end
-
-        # Shorthand method for finding the left sibling and moving to the left of it.
-        def move_left
-          move_to_left_of left_sibling
-        end
-
-        # Shorthand method for finding the right sibling and moving to the right of it.
-        def move_right
-          move_to_right_of right_sibling
-        end
-
-        # Move the node to the left of another node (you can pass id only)
-        def move_to_left_of(node)
-          move_to node, :left
-        end
-
-        # Move the node to the left of another node (you can pass id only)
-        def move_to_right_of(node)
-          move_to node, :right
-        end
-
-        # Move the node to the child of another node (you can pass id only)
-        def move_to_child_of(node)
-          move_to node, :child
-        end
-
-        # Move the node to the child of another node with specify index (you can pass id only)
-        def move_to_child_with_index(node, index)
-          if node.children.empty?
-            move_to_child_of(node)
-          elsif node.children.count == index
-            move_to_right_of(node.children.last)
-          else
-            move_to_left_of(node.children[index])
-          end
-        end
-
-        # Move the node to root nodes
-        def move_to_root
-          move_to nil, :root
-        end
-
-        # Order children in a nested set by an attribute
-        # Can order by any attribute class that uses the Comparable mixin, for example a string or integer
-        # Usage example when sorting categories alphabetically: @new_category.move_to_ordered_child_of(@root, "name")
-        def move_to_ordered_child_of(parent, order_attribute, ascending = true)
-          self.move_to_root and return unless parent
-          left = nil # This is needed, at least for the tests.
-          parent.children.each do |n| # Find the node immediately to the left of this node.
-            if ascending
-              left = n if n.send(order_attribute) < self.send(order_attribute)
-            else
-              left = n if n.send(order_attribute) > self.send(order_attribute)
-            end
-          end
-          self.move_to_child_of(parent)
-          return unless parent.children.count > 1 # Only need to order if there are multiple children.
-          if left # Self has a left neighbor.
-            self.move_to_right_of(left)
-          else # Self is the left most node.
-            self.move_to_left_of(parent.children[0])
-          end
-        end
-
-        def move_possible?(target)
-          self != target && # Can't target self
-          same_scope?(target) && # can't be in different scopes
-          # !(left..right).include?(target.left..target.right) # this needs tested more
-          # detect impossible move
-          !((left <= target.left && right >= target.left) or (left <= target.right && right >= target.right))
-        end
-
-        def to_text
-          self_and_descendants.map do |node|
-            "#{'*'*(node.level+1)} #{node.id} #{node.to_s} (#{node.parent_id}, #{node.left}, #{node.right})"
-          end.join("\n")
-        end
-
-      protected
-        def compute_level
-          node, nesting = self, 0
-          while (association = node.association(:parent)).loaded? && association.target
-            nesting += 1
-            node = node.parent
-          end if node.respond_to? :association
-          node == self ? ancestors.count : node.level + nesting
-        end
-
-        def without_self(scope)
-          scope.where(["#{self.class.quoted_table_name}.#{self.class.primary_key} != ?", self])
-        end
-
-        # All nested set queries should use this nested_set_scope, which performs finds on
-        # the base ActiveRecord class, using the :scope declared in the acts_as_nested_set
-        # declaration.
-        def nested_set_scope(options = {})
-          options = {:order => quoted_left_column_full_name}.merge(options)
-          scopes = Array(acts_as_nested_set_options[:scope])
-          options[:conditions] = scopes.inject({}) do |conditions,attr|
-            conditions.merge attr => self[attr]
-          end unless scopes.empty?
-          self.class.base_class.unscoped.scoped options
-        end
-
-        def store_new_parent
-          @move_to_new_parent_id = send("#{parent_column_name}_changed?") ? parent_id : false
-          true # force callback to return true
-        end
-
-        def move_to_new_parent
-          if @move_to_new_parent_id.nil?
-            move_to_root
-          elsif @move_to_new_parent_id
-            move_to_child_of(@move_to_new_parent_id)
-          end
-        end
-
-        def set_depth!
-          if nested_set_scope.column_names.map(&:to_s).include?(depth_column_name.to_s)
-            in_tenacious_transaction do
-              reload
-
-              nested_set_scope.where(:id => id).update_all(["#{quoted_depth_column_name} = ?", level])
-            end
-            self[depth_column_name.to_sym] = self.level
-          end
-        end
-
-        def right_most_bound
-          right_most_node =
-            self.class.base_class.unscoped.
-              order("#{quoted_right_column_full_name} desc").limit(1).lock(true).first
-          right_most_node ? (right_most_node[right_column_name] || 0) : 0
-        end
-
-        # on creation, set automatically lft and rgt to the end of the tree
-        def set_default_left_and_right
-          # adds the new node to the right of all existing nodes
-          self[left_column_name] = right_most_bound + 1
-          self[right_column_name] = right_most_bound + 2
-        end
-
-        def in_tenacious_transaction(&block)
-          retry_count = 0
-          begin
-            transaction(&block)
-          rescue ActiveRecord::StatementInvalid => error
-            raise unless connection.open_transactions.zero?
-            raise unless error.message =~ /Deadlock found when trying to get lock|Lock wait timeout exceeded/
-            raise unless retry_count < 10
-            retry_count += 1
-            logger.info "Deadlock detected on retry #{retry_count}, restarting transaction"
-            sleep(rand(retry_count)*0.1) # Aloha protocol
-            retry
-          end
-        end
-
-        # Prunes a branch off of the tree, shifting all of the elements on the right
-        # back to the left so the counts still work.
-        def destroy_descendants
-          return if right.nil? || left.nil? || skip_before_destroy
-
-          in_tenacious_transaction do
-            reload_nested_set
-            # select the rows in the model that extend past the deletion point and apply a lock
-            nested_set_scope.where(["#{quoted_left_column_full_name} >= ?", left]).
-                                  select(id).lock(true)
-
-            if acts_as_nested_set_options[:dependent] == :destroy
-              descendants.each do |model|
-                model.skip_before_destroy = true
-                model.destroy
-              end
-            else
-              nested_set_scope.where(["#{quoted_left_column_name} > ? AND #{quoted_right_column_name} < ?", left, right]).
-                               delete_all
-            end
-
-            # update lefts and rights for remaining nodes
-            diff = right - left + 1
-            nested_set_scope.where(["#{quoted_left_column_full_name} > ?", right]).update_all(
-              ["#{quoted_left_column_name} = (#{quoted_left_column_name} - ?)", diff]
-            )
-
-            nested_set_scope.where(["#{quoted_right_column_full_name} > ?", right]).update_all(
-              ["#{quoted_right_column_name} = (#{quoted_right_column_name} - ?)", diff]
-            )
-
-            # Don't allow multiple calls to destroy to corrupt the set
-            self.skip_before_destroy = true
-          end
-        end
-
-        # reload left, right, and parent
-        def reload_nested_set
-          reload(
-            :select => "#{quoted_left_column_full_name}, #{quoted_right_column_full_name}, #{quoted_parent_column_full_name}",
-            :lock => true
-          )
-        end
-
-        def move_to(target, position)
-          raise ActiveRecord::ActiveRecordError, "You cannot move a new node" if self.new_record?
-          run_callbacks :move do
-            in_tenacious_transaction do
-              if target.is_a? self.class.base_class
-                target.reload_nested_set
-              elsif position != :root
-                # load object if node is not an object
-                target = nested_set_scope.find(target)
-              end
-              self.reload_nested_set
-
-              unless position == :root || move_possible?(target)
-                raise ActiveRecord::ActiveRecordError, "Impossible move, target node cannot be inside moved tree."
-              end
-
-              bound = case position
-                when :child;  target[right_column_name]
-                when :left;   target[left_column_name]
-                when :right;  target[right_column_name] + 1
-                when :root;   1
-                else raise ActiveRecord::ActiveRecordError, "Position should be :child, :left, :right or :root ('#{position}' received)."
-              end
-
-              if bound > self[right_column_name]
-                bound = bound - 1
-                other_bound = self[right_column_name] + 1
-              else
-                other_bound = self[left_column_name] - 1
-              end
-
-              # there would be no change
-              return if bound == self[right_column_name] || bound == self[left_column_name]
-
-              # we have defined the boundaries of two non-overlapping intervals,
-              # so sorting puts both the intervals and their boundaries in order
-              a, b, c, d = [self[left_column_name], self[right_column_name], bound, other_bound].sort
-
-              # select the rows in the model between a and d, and apply a lock
-              self.class.base_class.select('id').lock(true).where(
-                ["#{quoted_left_column_full_name} >= :a and #{quoted_right_column_full_name} <= :d", {:a => a, :d => d}]
-              )
-
-              new_parent = case position
-                when :child;  target.id
-                when :root;   nil
-                else          target[parent_column_name]
-              end
-
-              where_statement = ["not (#{quoted_left_column_name} = CASE " +
-                                     "WHEN #{quoted_left_column_name} BETWEEN :a AND :b " +
-                                     "THEN #{quoted_left_column_name} + :d - :b " +
-                                     "WHEN #{quoted_left_column_name} BETWEEN :c AND :d " +
-                                     "THEN #{quoted_left_column_name} + :a - :c " +
-                                     "ELSE #{quoted_left_column_name} END AND " +
-                                     "#{quoted_right_column_name} = CASE " +
-                                     "WHEN #{quoted_right_column_name} BETWEEN :a AND :b " +
-                                     "THEN #{quoted_right_column_name} + :d - :b " +
-                                     "WHEN #{quoted_right_column_name} BETWEEN :c AND :d " +
-                                     "THEN #{quoted_right_column_name} + :a - :c " +
-                                     "ELSE #{quoted_right_column_name} END AND " +
-                                     "#{quoted_parent_column_name} = CASE " +
-                                     "WHEN #{self.class.base_class.primary_key} = :id THEN :new_parent " +
-                                     "ELSE #{quoted_parent_column_name} END)" ,
-                                 {:a => a, :b => b, :c => c, :d => d, :id => self.id, :new_parent => new_parent}    ]
-
-
-
+      def acts_as_nested_set_relate_children!
+        has_many_children_options = {
+          :class_name => self.base_class.to_s,
+          :foreign_key => parent_column_name,
+          :order => quoted_order_column_name,
+          :inverse_of => (:parent unless acts_as_nested_set_options[:polymorphic]),
+        }
 
-              self.nested_set_scope.where(*where_statement).update_all([
-                "#{quoted_left_column_name} = CASE " +
-                  "WHEN #{quoted_left_column_name} BETWEEN :a AND :b " +
-                    "THEN #{quoted_left_column_name} + :d - :b " +
-                  "WHEN #{quoted_left_column_name} BETWEEN :c AND :d " +
-                    "THEN #{quoted_left_column_name} + :a - :c " +
-                  "ELSE #{quoted_left_column_name} END, " +
-                "#{quoted_right_column_name} = CASE " +
-                  "WHEN #{quoted_right_column_name} BETWEEN :a AND :b " +
-                    "THEN #{quoted_right_column_name} + :d - :b " +
-                  "WHEN #{quoted_right_column_name} BETWEEN :c AND :d " +
-                    "THEN #{quoted_right_column_name} + :a - :c " +
-                  "ELSE #{quoted_right_column_name} END, " +
-                "#{quoted_parent_column_name} = CASE " +
-                  "WHEN #{self.class.base_class.primary_key} = :id THEN :new_parent " +
-                  "ELSE #{quoted_parent_column_name} END",
-                {:a => a, :b => b, :c => c, :d => d, :id => self.id, :new_parent => new_parent}
-              ])
-            end
-            target.reload_nested_set if target
-            self.set_depth!
-            self.descendants.each(&:save)
-            self.reload_nested_set
-          end
+        # Add callbacks, if they were supplied.. otherwise, we don't want them.
+        [:before_add, :after_add, :before_remove, :after_remove].each do |ar_callback|
+          has_many_children_options.update(ar_callback => acts_as_nested_set_options[ar_callback]) if acts_as_nested_set_options[ar_callback]
         end
 
+        has_many :children, has_many_children_options
       end
 
-      # Mixed into both classes and instances to provide easy access to the column names
-      module Columns
-        def left_column_name
-          acts_as_nested_set_options[:left_column]
-        end
-
-        def right_column_name
-          acts_as_nested_set_options[:right_column]
-        end
-
-        def depth_column_name
-          acts_as_nested_set_options[:depth_column]
-        end
-
-        def parent_column_name
-          acts_as_nested_set_options[:parent_column]
-        end
-
-        def order_column
-          acts_as_nested_set_options[:order_column] || left_column_name
-        end
-
-        def scope_column_names
-          Array(acts_as_nested_set_options[:scope])
-        end
-
-        def quoted_left_column_name
-          connection.quote_column_name(left_column_name)
-        end
-
-        def quoted_right_column_name
-          connection.quote_column_name(right_column_name)
-        end
-
-        def quoted_depth_column_name
-          connection.quote_column_name(depth_column_name)
-        end
+      def acts_as_nested_set_relate_parent!
+        belongs_to :parent, :class_name => self.base_class.to_s,
+                            :foreign_key => parent_column_name,
+                            :counter_cache => acts_as_nested_set_options[:counter_cache],
+                            :inverse_of => (:children unless acts_as_nested_set_options[:polymorphic]),
+                            :polymorphic => acts_as_nested_set_options[:polymorphic]
+      end
 
-        def quoted_parent_column_name
-          connection.quote_column_name(parent_column_name)
-        end
+      def acts_as_nested_set_default_options
+        {
+          :parent_column => 'parent_id',
+          :left_column => 'lft',
+          :right_column => 'rgt',
+          :depth_column => 'depth',
+          :dependent => :delete_all, # or :destroy
+          :polymorphic => false,
+          :counter_cache => false
+        }.freeze
+      end
 
-        def quoted_scope_column_names
-          scope_column_names.collect {|column_name| connection.quote_column_name(column_name) }
-        end
+      def acts_as_nested_set_parse_options!(options)
+        options = acts_as_nested_set_default_options.merge(options)
 
-        def quoted_left_column_full_name
-          "#{quoted_table_name}.#{quoted_left_column_name}"
+        if options[:scope].is_a?(Symbol) && options[:scope].to_s !~ /_id$/
+          options[:scope] = "#{options[:scope]}_id".intern
         end
 
-        def quoted_right_column_full_name
-          "#{quoted_table_name}.#{quoted_right_column_name}"
-        end
+        class_attribute :acts_as_nested_set_options
+        self.acts_as_nested_set_options = options
+      end
 
-        def quoted_parent_column_full_name
-          "#{quoted_table_name}.#{quoted_parent_column_name}"
+      def acts_as_nested_set_prevent_assignment_to_reserved_columns!
+        # no assignment to structure fields
+        [left_column_name, right_column_name, depth_column_name].each do |column|
+          module_eval <<-"end_eval", __FILE__, __LINE__
+            def #{column}=(x)
+              raise ActiveRecord::ActiveRecordError, "Unauthorized assignment to #{column}: it's an internal field handled by acts_as_nested_set code, use move_to_* methods instead."
+            end
+          end_eval
         end
       end
-
     end
   end
 end
diff --git a/lib/plugins/awesome_nested_set/lib/awesome_nested_set/columns.rb b/lib/plugins/awesome_nested_set/lib/awesome_nested_set/columns.rb
new file mode 100644
index 000000000..9b6a733c8
--- /dev/null
+++ b/lib/plugins/awesome_nested_set/lib/awesome_nested_set/columns.rb
@@ -0,0 +1,68 @@
+# Mixed into both classes and instances to provide easy access to the column names
+module CollectiveIdea #:nodoc:
+  module Acts #:nodoc:
+    module NestedSet #:nodoc:
+      module Columns
+        def left_column_name
+          acts_as_nested_set_options[:left_column]
+        end
+
+        def right_column_name
+          acts_as_nested_set_options[:right_column]
+        end
+
+        def depth_column_name
+          acts_as_nested_set_options[:depth_column]
+        end
+
+        def parent_column_name
+          acts_as_nested_set_options[:parent_column]
+        end
+
+        def order_column
+          acts_as_nested_set_options[:order_column] || left_column_name
+        end
+
+        def scope_column_names
+          Array(acts_as_nested_set_options[:scope])
+        end
+
+        def quoted_left_column_name
+          connection.quote_column_name(left_column_name)
+        end
+
+        def quoted_right_column_name
+          connection.quote_column_name(right_column_name)
+        end
+
+        def quoted_depth_column_name
+          connection.quote_column_name(depth_column_name)
+        end
+
+        def quoted_parent_column_name
+          connection.quote_column_name(parent_column_name)
+        end
+
+        def quoted_scope_column_names
+          scope_column_names.collect {|column_name| connection.quote_column_name(column_name) }
+        end
+
+        def quoted_order_column_name
+          connection.quote_column_name(order_column)
+        end
+
+        def quoted_left_column_full_name
+          "#{quoted_table_name}.#{quoted_left_column_name}"
+        end
+
+        def quoted_right_column_full_name
+          "#{quoted_table_name}.#{quoted_right_column_name}"
+        end
+
+        def quoted_parent_column_full_name
+          "#{quoted_table_name}.#{quoted_parent_column_name}"
+        end
+      end
+    end
+  end
+end
diff --git a/lib/plugins/awesome_nested_set/lib/awesome_nested_set/helper.rb b/lib/plugins/awesome_nested_set/lib/awesome_nested_set/helper.rb
index 98d2688fa..bd8d40df1 100644
--- a/lib/plugins/awesome_nested_set/lib/awesome_nested_set/helper.rb
+++ b/lib/plugins/awesome_nested_set/lib/awesome_nested_set/helper.rb
@@ -38,51 +38,6 @@ module CollectiveIdea #:nodoc:
           end
           result
         end
-        
-        # Returns options for select as nested_set_options, sorted by an specific column
-        # It requires passing a string with the name of the column to sort the set with
-        # You can exclude some items from the tree.
-        # You can pass a block receiving an item and returning the string displayed in the select.
-        #
-        # == Params
-        #  * +class_or_item+ - Class name or top level times
-        #  * +:column+ - Column to sort the set (this will sort each children for all root elements)
-        #  * +mover+ - The item that is being move, used to exlude impossible moves
-        #  * +&block+ - a block that will be used to display: { |item| ... item.name }
-        #
-        # == Usage
-        #
-        #   <%= f.select :parent_id, nested_set_options(Category, :sort_by_this_column,  @category) {|i|
-        #       "#{'–' * i.level} #{i.name}"
-        #     }) %>
-        #
-        def sorted_nested_set_options(class_or_item, order, mover = nil)
-          if class_or_item.is_a? Array
-            items = class_or_item.reject { |e| !e.root? }
-          else
-            class_or_item = class_or_item.roots if class_or_item.is_a?(Class)
-            items = Array(class_or_item)
-          end
-          result = []
-          children = []
-          items.each do |root|
-            root.class.associate_parents(root.self_and_descendants).map do |i|
-              if mover.nil? || mover.new_record? || mover.move_possible?(i)
-                if !i.leaf?
-                  children.sort_by! &order
-                  children.each { |c| result << [yield(c), c.id] }
-                  children = []
-                  result << [yield(i), i.id]
-                else
-                  children << i
-                 end
-              end   
-            end.compact
-          end
-          children.sort_by! &order
-          children.each { |c| result << [yield(c), c.id] }
-          result
-        end
       end
     end
   end
diff --git a/lib/plugins/awesome_nested_set/lib/awesome_nested_set/iterator.rb b/lib/plugins/awesome_nested_set/lib/awesome_nested_set/iterator.rb
new file mode 100644
index 000000000..94aca41ea
--- /dev/null
+++ b/lib/plugins/awesome_nested_set/lib/awesome_nested_set/iterator.rb
@@ -0,0 +1,29 @@
+module CollectiveIdea #:nodoc:
+  module Acts #:nodoc:
+    module NestedSet #:nodoc:
+      class Iterator
+        attr_reader :objects
+
+        def initialize(objects)
+          @objects = objects
+        end
+
+        def each_with_level
+          path = [nil]
+          objects.each do |o|
+            if o.parent_id != path.last
+              # we are on a new level, did we descend or ascend?
+              if path.include?(o.parent_id)
+                # remove wrong tailing paths elements
+                path.pop while path.last != o.parent_id
+              else
+                path << o.parent_id
+              end
+            end
+            yield(o, path.length - 1)
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/lib/plugins/awesome_nested_set/lib/awesome_nested_set/model.rb b/lib/plugins/awesome_nested_set/lib/awesome_nested_set/model.rb
new file mode 100644
index 000000000..e8d1e1844
--- /dev/null
+++ b/lib/plugins/awesome_nested_set/lib/awesome_nested_set/model.rb
@@ -0,0 +1,212 @@
+require 'awesome_nested_set/model/prunable'
+require 'awesome_nested_set/model/movable'
+require 'awesome_nested_set/model/transactable'
+require 'awesome_nested_set/model/relatable'
+require 'awesome_nested_set/model/rebuildable'
+require 'awesome_nested_set/model/validatable'
+require 'awesome_nested_set/iterator'
+
+module CollectiveIdea #:nodoc:
+  module Acts #:nodoc:
+    module NestedSet #:nodoc:
+
+      module Model
+        extend ActiveSupport::Concern
+
+        included do
+          delegate :quoted_table_name, :arel_table, :to => self
+          extend Validatable
+          extend Rebuildable
+          include Movable
+          include Prunable
+          include Relatable
+          include Transactable
+        end
+
+        module ClassMethods
+          def associate_parents(objects)
+            return objects unless objects.all? {|o| o.respond_to?(:association)}
+
+            id_indexed = objects.index_by(&:id)
+            objects.each do |object|
+              association = object.association(:parent)
+              parent = id_indexed[object.parent_id]
+
+              if !association.loaded? && parent
+                association.target = parent
+                association.set_inverse_instance(parent)
+              end
+            end
+          end
+
+          def children_of(parent_id)
+            where arel_table[parent_column_name].eq(parent_id)
+          end
+
+          # Iterates over tree elements and determines the current level in the tree.
+          # Only accepts default ordering, odering by an other column than lft
+          # does not work. This method is much more efficent than calling level
+          # because it doesn't require any additional database queries.
+          #
+          # Example:
+          #    Category.each_with_level(Category.root.self_and_descendants) do |o, level|
+          #
+          def each_with_level(objects, &block)
+            Iterator.new(objects).each_with_level(&block)
+          end
+
+          def leaves
+            nested_set_scope.where "#{quoted_right_column_full_name} - #{quoted_left_column_full_name} = 1"
+          end
+
+          def left_of(node)
+            where arel_table[left_column_name].lt(node)
+          end
+
+          def left_of_right_side(node)
+            where arel_table[right_column_name].lteq(node)
+          end
+
+          def right_of(node)
+            where arel_table[left_column_name].gteq(node)
+          end
+
+          def nested_set_scope(options = {})
+            options = {:order => quoted_order_column_name}.merge(options)
+
+            order(options.delete(:order)).scoped options
+          end
+
+          def primary_key_scope(id)
+            where arel_table[primary_key].eq(id)
+          end
+
+          def root
+            roots.first
+          end
+
+          def roots
+            nested_set_scope.children_of nil
+          end
+        end # end class methods
+
+        # Any instance method that returns a collection makes use of Rails 2.1's named_scope (which is bundled for Rails 2.0), so it can be treated as a finder.
+        #
+        #   category.self_and_descendants.count
+        #   category.ancestors.find(:all, :conditions => "name like '%foo%'")
+        # Value of the parent column
+        def parent_id(target = self)
+          target[parent_column_name]
+        end
+
+        # Value of the left column
+        def left(target = self)
+          target[left_column_name]
+        end
+
+        # Value of the right column
+        def right(target = self)
+          target[right_column_name]
+        end
+
+        # Returns true if this is a root node.
+        def root?
+          parent_id.nil?
+        end
+
+        # Returns true is this is a child node
+        def child?
+          !root?
+        end
+
+        # Returns true if this is the end of a branch.
+        def leaf?
+          persisted? && right.to_i - left.to_i == 1
+        end
+
+        # All nested set queries should use this nested_set_scope, which
+        # performs finds on the base ActiveRecord class, using the :scope
+        # declared in the acts_as_nested_set declaration.
+        def nested_set_scope(options = {})
+          if (scopes = Array(acts_as_nested_set_options[:scope])).any?
+            options[:conditions] = scopes.inject({}) do |conditions,attr|
+              conditions.merge attr => self[attr]
+            end
+          end
+
+          self.class.nested_set_scope options
+        end
+
+        def to_text
+          self_and_descendants.map do |node|
+            "#{'*'*(node.level+1)} #{node.id} #{node.to_s} (#{node.parent_id}, #{node.left}, #{node.right})"
+          end.join("\n")
+        end
+
+        protected
+
+        def without_self(scope)
+          return scope if new_record?
+          scope.where(["#{self.class.quoted_table_name}.#{self.class.primary_key} != ?", self])
+        end
+
+        def store_new_parent
+          @move_to_new_parent_id = send("#{parent_column_name}_changed?") ? parent_id : false
+          true # force callback to return true
+        end
+
+        def has_depth_column?
+          nested_set_scope.column_names.map(&:to_s).include?(depth_column_name.to_s)
+        end
+
+        def right_most_node
+          @right_most_node ||= self.class.base_class.unscoped.nested_set_scope(
+            :order => "#{quoted_right_column_full_name} desc"
+          ).first
+        end
+
+        def right_most_bound
+          @right_most_bound ||= begin
+            return 0 if right_most_node.nil?
+
+            right_most_node.lock!
+            right_most_node[right_column_name] || 0
+          end
+        end
+
+        def set_depth!
+          return unless has_depth_column?
+
+          in_tenacious_transaction do
+            reload
+            nested_set_scope.primary_key_scope(id).
+              update_all(["#{quoted_depth_column_name} = ?", level])
+          end
+          self[depth_column_name] = self.level
+        end
+
+        def set_default_left_and_right
+          # adds the new node to the right of all existing nodes
+          self[left_column_name] = right_most_bound + 1
+          self[right_column_name] = right_most_bound + 2
+        end
+
+        # reload left, right, and parent
+        def reload_nested_set
+          reload(
+            :select => "#{quoted_left_column_full_name}, #{quoted_right_column_full_name}, #{quoted_parent_column_full_name}",
+            :lock => true
+          )
+        end
+
+        def reload_target(target)
+          if target.is_a? self.class.base_class
+            target.reload
+          else
+            nested_set_scope.find(target)
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/lib/plugins/awesome_nested_set/lib/awesome_nested_set/model/movable.rb b/lib/plugins/awesome_nested_set/lib/awesome_nested_set/model/movable.rb
new file mode 100644
index 000000000..7b94ca22a
--- /dev/null
+++ b/lib/plugins/awesome_nested_set/lib/awesome_nested_set/model/movable.rb
@@ -0,0 +1,137 @@
+require 'awesome_nested_set/move'
+
+module CollectiveIdea #:nodoc:
+  module Acts #:nodoc:
+    module NestedSet #:nodoc:
+      module Model
+        module Movable
+
+          def move_possible?(target)
+            self != target && # Can't target self
+              same_scope?(target) && # can't be in different scopes
+              # detect impossible move
+              within_bounds?(target.left, target.left) &&
+              within_bounds?(target.right, target.right)
+          end
+
+          # Shorthand method for finding the left sibling and moving to the left of it.
+          def move_left
+            move_to_left_of left_sibling
+          end
+
+          # Shorthand method for finding the right sibling and moving to the right of it.
+          def move_right
+            move_to_right_of right_sibling
+          end
+
+          # Move the node to the left of another node
+          def move_to_left_of(node)
+            move_to node, :left
+          end
+
+          # Move the node to the left of another node
+          def move_to_right_of(node)
+            move_to node, :right
+          end
+
+          # Move the node to the child of another node
+          def move_to_child_of(node)
+            move_to node, :child
+          end
+
+          # Move the node to the child of another node with specify index
+          def move_to_child_with_index(node, index)
+            if node.children.empty?
+              move_to_child_of(node)
+            elsif node.children.count == index
+              move_to_right_of(node.children.last)
+            else
+              move_to_left_of(node.children[index])
+            end
+          end
+
+          # Move the node to root nodes
+          def move_to_root
+            move_to_right_of(root)
+          end
+
+          # Order children in a nested set by an attribute
+          # Can order by any attribute class that uses the Comparable mixin, for example a string or integer
+          # Usage example when sorting categories alphabetically: @new_category.move_to_ordered_child_of(@root, "name")
+          def move_to_ordered_child_of(parent, order_attribute, ascending = true)
+            self.move_to_root and return unless parent
+
+            left_neighbor = find_left_neighbor(parent, order_attribute, ascending)
+            self.move_to_child_of(parent)
+
+            return unless parent.children.many?
+
+            if left_neighbor
+              self.move_to_right_of(left_neighbor)
+            else # Self is the left most node.
+              self.move_to_left_of(parent.children[0])
+            end
+          end
+
+          # Find the node immediately to the left of this node.
+          def find_left_neighbor(parent, order_attribute, ascending)
+            left = nil
+            parent.children.each do |n|
+              if ascending
+                left = n if n.send(order_attribute) < self.send(order_attribute)
+              else
+                left = n if n.send(order_attribute) > self.send(order_attribute)
+              end
+            end
+            left
+          end
+
+          def move_to(target, position)
+            prevent_unpersisted_move
+
+            run_callbacks :move do
+              in_tenacious_transaction do
+                target = reload_target(target)
+                self.reload_nested_set
+
+                Move.new(target, position, self).move
+              end
+              after_move_to(target, position)
+            end
+          end
+
+          protected
+
+          def after_move_to(target, position)
+            target.reload_nested_set if target
+            self.set_depth!
+            self.descendants.each(&:save)
+            self.reload_nested_set
+          end
+
+          def move_to_new_parent
+            if @move_to_new_parent_id.nil?
+              move_to_root
+            elsif @move_to_new_parent_id
+              move_to_child_of(@move_to_new_parent_id)
+            end
+          end
+
+          def out_of_bounds?(left_bound, right_bound)
+            left <= left_bound && right >= right_bound
+          end
+
+          def prevent_unpersisted_move
+            if self.new_record?
+              raise ActiveRecord::ActiveRecordError, "You cannot move a new node"
+            end
+          end
+
+          def within_bounds?(left_bound, right_bound)
+            !out_of_bounds?(left_bound, right_bound)
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/lib/plugins/awesome_nested_set/lib/awesome_nested_set/model/prunable.rb b/lib/plugins/awesome_nested_set/lib/awesome_nested_set/model/prunable.rb
new file mode 100644
index 000000000..501b311e3
--- /dev/null
+++ b/lib/plugins/awesome_nested_set/lib/awesome_nested_set/model/prunable.rb
@@ -0,0 +1,58 @@
+module CollectiveIdea #:nodoc:
+  module Acts #:nodoc:
+    module NestedSet #:nodoc:
+      module Model
+        module Prunable
+
+          # Prunes a branch off of the tree, shifting all of the elements on the right
+          # back to the left so the counts still work.
+          def destroy_descendants
+            return if right.nil? || left.nil? || skip_before_destroy
+
+            in_tenacious_transaction do
+              reload_nested_set
+              # select the rows in the model that extend past the deletion point and apply a lock
+              nested_set_scope.right_of(left).select(id).lock(true)
+
+              destroy_or_delete_descendants
+
+              # update lefts and rights for remaining nodes
+              update_siblings_for_remaining_nodes
+
+              # Don't allow multiple calls to destroy to corrupt the set
+              self.skip_before_destroy = true
+            end
+          end
+
+          def destroy_or_delete_descendants
+            if acts_as_nested_set_options[:dependent] == :destroy
+              descendants.each do |model|
+                model.skip_before_destroy = true
+                model.destroy
+              end
+            else
+              descendants.delete_all
+            end
+          end
+
+          def update_siblings_for_remaining_nodes
+            update_siblings(:left)
+            update_siblings(:right)
+          end
+
+          def update_siblings(direction)
+            full_column_name = send("quoted_#{direction}_column_full_name")
+            column_name = send("quoted_#{direction}_column_name")
+
+            nested_set_scope.where(["#{full_column_name} > ?", right]).
+              update_all(["#{column_name} = (#{column_name} - ?)", diff])
+          end
+
+          def diff
+            right - left + 1
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/lib/plugins/awesome_nested_set/lib/awesome_nested_set/model/rebuildable.rb b/lib/plugins/awesome_nested_set/lib/awesome_nested_set/model/rebuildable.rb
new file mode 100644
index 000000000..553c308c1
--- /dev/null
+++ b/lib/plugins/awesome_nested_set/lib/awesome_nested_set/model/rebuildable.rb
@@ -0,0 +1,41 @@
+require 'awesome_nested_set/tree'
+
+module CollectiveIdea
+  module Acts
+    module NestedSet
+      module Model
+        module Rebuildable
+
+
+          # Rebuilds the left & rights if unset or invalid.
+          # Also very useful for converting from acts_as_tree.
+          def rebuild!(validate_nodes = true)
+            # default_scope with order may break database queries so we do all operation without scope
+            unscoped do
+              Tree.new(self, validate_nodes).rebuild!
+            end
+          end
+
+          private
+          def scope_for_rebuild
+            scope = proc {}
+
+            if acts_as_nested_set_options[:scope]
+              scope = proc {|node|
+                scope_column_names.inject("") {|str, column_name|
+                  str << "AND #{connection.quote_column_name(column_name)} = #{connection.quote(node.send(column_name))} "
+                }
+              }
+            end
+            scope
+          end
+
+          def order_for_rebuild
+            "#{quoted_left_column_full_name}, #{quoted_right_column_full_name}, #{primary_key}"
+          end
+        end
+
+      end
+    end
+  end
+end
diff --git a/lib/plugins/awesome_nested_set/lib/awesome_nested_set/model/relatable.rb b/lib/plugins/awesome_nested_set/lib/awesome_nested_set/model/relatable.rb
new file mode 100644
index 000000000..21de61a9d
--- /dev/null
+++ b/lib/plugins/awesome_nested_set/lib/awesome_nested_set/model/relatable.rb
@@ -0,0 +1,121 @@
+module CollectiveIdea
+  module Acts
+    module NestedSet
+      module Model
+        module Relatable
+
+          # Returns an collection of all parents
+          def ancestors
+            without_self self_and_ancestors
+          end
+
+          # Returns the collection of all parents and self
+          def self_and_ancestors
+            nested_set_scope.
+              where(arel_table[left_column_name].lteq(left)).
+              where(arel_table[right_column_name].gteq(right))
+          end
+
+          # Returns the collection of all children of the parent, except self
+          def siblings
+            without_self self_and_siblings
+          end
+
+          # Returns the collection of all children of the parent, including self
+          def self_and_siblings
+            nested_set_scope.children_of parent_id
+          end
+
+          # Returns a set of all of its nested children which do not have children
+          def leaves
+            descendants.where(
+              "#{quoted_right_column_full_name} - #{quoted_left_column_full_name} = 1"
+            )
+          end
+
+          # Returns the level of this object in the tree
+          # root level is 0
+          def level
+            parent_id.nil? ? 0 : compute_level
+          end
+
+          # Returns a collection including all of its children and nested children
+          def descendants
+            without_self self_and_descendants
+          end
+
+          # Returns a collection including itself and all of its nested children
+          def self_and_descendants
+            # using _left_ for both sides here lets us benefit from an index on that column if one exists
+            nested_set_scope.right_of(left).left_of(right)
+          end
+
+          def is_descendant_of?(other)
+            within_node?(other, self) && same_scope?(other)
+          end
+
+          def is_or_is_descendant_of?(other)
+            (other == self || within_node?(other, self)) && same_scope?(other)
+          end
+
+          def is_ancestor_of?(other)
+            within_node?(self, other) && same_scope?(other)
+          end
+
+          def is_or_is_ancestor_of?(other)
+            (self == other || within_node?(self, other)) && same_scope?(other)
+          end
+
+          # Check if other model is in the same scope
+          def same_scope?(other)
+            Array(acts_as_nested_set_options[:scope]).all? do |attr|
+              self.send(attr) == other.send(attr)
+            end
+          end
+
+          # Find the first sibling to the left
+          def left_sibling
+            siblings.left_of(left).last
+          end
+
+          # Find the first sibling to the right
+          def right_sibling
+            siblings.right_of(left).first
+          end
+
+          def root
+            return self_and_ancestors.children_of(nil).first if persisted?
+
+            if parent_id && current_parent = nested_set_scope.find(parent_id)
+              current_parent.root
+            else
+              self
+            end
+          end
+
+          protected
+
+          def compute_level
+            node, nesting = determine_depth
+
+            node == self ? ancestors.count : node.level + nesting
+          end
+
+          def determine_depth(node = self, nesting = 0)
+            while (association = node.association(:parent)).loaded? && association.target
+              nesting += 1
+              node = node.parent
+            end if node.respond_to?(:association)
+
+            [node, nesting]
+          end
+
+          def within_node?(node, within)
+            node.left < within.left && within.left < node.right
+          end
+
+        end
+      end
+    end
+  end
+end
diff --git a/lib/plugins/awesome_nested_set/lib/awesome_nested_set/model/transactable.rb b/lib/plugins/awesome_nested_set/lib/awesome_nested_set/model/transactable.rb
new file mode 100644
index 000000000..bef62d369
--- /dev/null
+++ b/lib/plugins/awesome_nested_set/lib/awesome_nested_set/model/transactable.rb
@@ -0,0 +1,27 @@
+module CollectiveIdea #:nodoc:
+  module Acts #:nodoc:
+    module NestedSet #:nodoc:
+      module Model
+        module Transactable
+
+          protected
+          def in_tenacious_transaction(&block)
+            retry_count = 0
+            begin
+              transaction(&block)
+            rescue ActiveRecord::StatementInvalid => error
+              raise unless connection.open_transactions.zero?
+              raise unless error.message =~ /Deadlock found when trying to get lock|Lock wait timeout exceeded/
+              raise unless retry_count < 10
+              retry_count += 1
+              logger.info "Deadlock detected on retry #{retry_count}, restarting transaction"
+              sleep(rand(retry_count)*0.1) # Aloha protocol
+              retry
+            end
+          end
+
+        end
+      end
+    end
+  end
+end
diff --git a/lib/plugins/awesome_nested_set/lib/awesome_nested_set/model/validatable.rb b/lib/plugins/awesome_nested_set/lib/awesome_nested_set/model/validatable.rb
new file mode 100644
index 000000000..0b84673f1
--- /dev/null
+++ b/lib/plugins/awesome_nested_set/lib/awesome_nested_set/model/validatable.rb
@@ -0,0 +1,69 @@
+require 'awesome_nested_set/set_validator'
+
+module CollectiveIdea
+  module Acts
+    module NestedSet
+      module Model
+        module Validatable
+
+          def valid?
+            left_and_rights_valid? && no_duplicates_for_columns? && all_roots_valid?
+          end
+
+          def left_and_rights_valid?
+            SetValidator.new(self).valid?
+          end
+
+          def no_duplicates_for_columns?
+            [quoted_left_column_full_name, quoted_right_column_full_name].all? do |column|
+              # No duplicates
+              select("#{scope_string}#{column}, COUNT(#{column})").
+                group("#{scope_string}#{column}").
+                having("COUNT(#{column}) > 1").
+                first.nil?
+            end
+          end
+
+          # Wrapper for each_root_valid? that can deal with scope.
+          def all_roots_valid?
+            if acts_as_nested_set_options[:scope]
+              all_roots_valid_by_scope?(roots)
+            else
+              each_root_valid?(roots)
+            end
+          end
+
+          def all_roots_valid_by_scope?(roots_to_validate)
+            roots_grouped_by_scope(roots_to_validate).all? do |scope, grouped_roots|
+              each_root_valid?(grouped_roots)
+            end
+          end
+
+          def each_root_valid?(roots_to_validate)
+            left = right = 0
+            roots_to_validate.all? do |root|
+              (root.left > left && root.right > right).tap do
+                left = root.left
+                right = root.right
+              end
+            end
+          end
+
+          private
+          def roots_grouped_by_scope(roots_to_group)
+            roots_to_group.group_by {|record|
+              scope_column_names.collect {|col| record.send(col) }
+            }
+          end
+
+          def scope_string
+            Array(acts_as_nested_set_options[:scope]).map do |c|
+              connection.quote_column_name(c)
+            end.push(nil).join(", ")
+          end
+
+        end
+      end
+    end
+  end
+end
diff --git a/lib/plugins/awesome_nested_set/lib/awesome_nested_set/move.rb b/lib/plugins/awesome_nested_set/lib/awesome_nested_set/move.rb
new file mode 100644
index 000000000..afc1152de
--- /dev/null
+++ b/lib/plugins/awesome_nested_set/lib/awesome_nested_set/move.rb
@@ -0,0 +1,117 @@
+module CollectiveIdea #:nodoc:
+  module Acts #:nodoc:
+    module NestedSet #:nodoc:
+      class Move
+        attr_reader :target, :position, :instance
+
+        def initialize(target, position, instance)
+          @target = target
+          @position = position
+          @instance = instance
+        end
+
+        def move
+          prevent_impossible_move
+
+          bound, other_bound = get_boundaries
+
+          # there would be no change
+          return if bound == right || bound == left
+
+          # we have defined the boundaries of two non-overlapping intervals,
+          # so sorting puts both the intervals and their boundaries in order
+          a, b, c, d = [left, right, bound, other_bound].sort
+
+          lock_nodes_between! a, d
+
+          nested_set_scope.where(where_statement(a, d)).
+                           update_all(conditions(a, b, c, d))
+        end
+
+        private
+
+        delegate :left, :right, :left_column_name, :right_column_name,
+                 :quoted_left_column_name, :quoted_right_column_name,
+                 :quoted_parent_column_name, :parent_column_name, :nested_set_scope,
+                 :to => :instance
+
+        delegate :arel_table, :class, :to => :instance, :prefix => true
+        delegate :base_class, :to => :instance_class, :prefix => :instance
+
+        def where_statement(left_bound, right_bound)
+          instance_arel_table[left_column_name].in(left_bound..right_bound).
+            or(instance_arel_table[right_column_name].in(left_bound..right_bound))
+        end
+
+        def conditions(a, b, c, d)
+          [
+           case_condition_for_direction(:quoted_left_column_name) +
+           case_condition_for_direction(:quoted_right_column_name) +
+           case_condition_for_parent,
+           {:a => a, :b => b, :c => c, :d => d, :id => instance.id, :new_parent => new_parent}
+          ]
+        end
+
+        def case_condition_for_direction(column_name)
+          column = send(column_name)
+          "#{column} = CASE " +
+            "WHEN #{column} BETWEEN :a AND :b " +
+            "THEN #{column} + :d - :b " +
+            "WHEN #{column} BETWEEN :c AND :d " +
+            "THEN #{column} + :a - :c " +
+            "ELSE #{column} END, "
+        end
+
+        def case_condition_for_parent
+          "#{quoted_parent_column_name} = CASE " +
+            "WHEN #{instance_base_class.primary_key} = :id THEN :new_parent " +
+            "ELSE #{quoted_parent_column_name} END"
+        end
+
+        def lock_nodes_between!(left_bound, right_bound)
+          # select the rows in the model between a and d, and apply a lock
+          instance_base_class.right_of(left_bound).left_of_right_side(right_bound).
+                              select(:id).lock(true)
+        end
+
+        def root
+          position == :root
+        end
+
+        def new_parent
+          case position
+          when :child
+            target.id
+          else
+            target[parent_column_name]
+          end
+        end
+
+        def get_boundaries
+          if (bound = target_bound) > right
+            bound -= 1
+            other_bound = right + 1
+          else
+            other_bound = left - 1
+          end
+          [bound, other_bound]
+        end
+
+        def prevent_impossible_move
+          if !root && !instance.move_possible?(target)
+            raise ActiveRecord::ActiveRecordError, "Impossible move, target node cannot be inside moved tree."
+          end
+        end
+
+        def target_bound
+          case position
+          when :child;  right(target)
+          when :left;   left(target)
+          when :right;  right(target) + 1
+          else raise ActiveRecord::ActiveRecordError, "Position should be :child, :left, :right or :root ('#{position}' received)."
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/lib/plugins/awesome_nested_set/lib/awesome_nested_set/set_validator.rb b/lib/plugins/awesome_nested_set/lib/awesome_nested_set/set_validator.rb
new file mode 100644
index 000000000..7cb9d3c30
--- /dev/null
+++ b/lib/plugins/awesome_nested_set/lib/awesome_nested_set/set_validator.rb
@@ -0,0 +1,63 @@
+module CollectiveIdea #:nodoc:
+  module Acts #:nodoc:
+    module NestedSet #:nodoc:
+      class SetValidator
+
+        def initialize(model)
+          @model = model
+          @scope = model.scoped
+          @parent = arel_table.alias('parent')
+        end
+
+        def valid?
+          query.count == 0
+        end
+
+        private
+
+        attr_reader :model, :parent
+        attr_accessor :scope
+
+        delegate :parent_column_name, :primary_key, :left_column_name, :right_column_name, :arel_table,
+          :quoted_table_name, :quoted_parent_column_full_name, :quoted_left_column_full_name, :quoted_right_column_full_name, :quoted_left_column_name, :quoted_right_column_name,
+        :to => :model
+
+        def query
+          join_scope
+          filter_scope
+        end
+
+        def join_scope
+          join_arel = arel_table.join(parent, Arel::Nodes::OuterJoin).on(parent[primary_key].eq(arel_table[parent_column_name]))
+          self.scope = scope.joins(join_arel.join_sql)
+        end
+
+        def filter_scope
+          self.scope = scope.where(
+                                   bound_is_null(left_column_name).
+                                   or(bound_is_null(right_column_name)).
+                                   or(left_bound_greater_than_right).
+                                   or(parent_not_null.and(bounds_outside_parent))
+                                   )
+        end
+
+        def bound_is_null(column_name)
+          arel_table[column_name].eq(nil)
+        end
+
+        def left_bound_greater_than_right
+          arel_table[left_column_name].gteq(arel_table[right_column_name])
+        end
+
+        def parent_not_null
+          arel_table[parent_column_name].not_eq(nil)
+        end
+
+        def bounds_outside_parent
+          arel_table[left_column_name].lteq(parent[left_column_name]).or(arel_table[right_column_name].gteq(parent[right_column_name]))
+        end
+
+      end
+    end
+  end
+end
diff --git a/lib/plugins/awesome_nested_set/lib/awesome_nested_set/tree.rb b/lib/plugins/awesome_nested_set/lib/awesome_nested_set/tree.rb
new file mode 100644
index 000000000..4a032c2a2
--- /dev/null
+++ b/lib/plugins/awesome_nested_set/lib/awesome_nested_set/tree.rb
@@ -0,0 +1,63 @@
+module CollectiveIdea #:nodoc:
+  module Acts #:nodoc:
+    module NestedSet #:nodoc:
+      class Tree
+        attr_reader :model, :validate_nodes
+        attr_accessor :indices
+
+        delegate :left_column_name, :right_column_name, :quoted_parent_column_full_name,
+                 :order_for_rebuild, :scope_for_rebuild,
+                 :to => :model
+
+        def initialize(model, validate_nodes)
+          @model = model
+          @validate_nodes = validate_nodes
+          @indices = {}
+        end
+
+        def rebuild!
+          # Don't rebuild a valid tree.
+          return true if model.valid?
+
+          root_nodes.each do |root_node|
+            # setup index for this scope
+            indices[scope_for_rebuild.call(root_node)] ||= 0
+            set_left_and_rights(root_node)
+          end
+        end
+
+        private
+
+        def increment_indice!(node)
+          indices[scope_for_rebuild.call(node)] += 1
+        end
+
+        def set_left_and_rights(node)
+          set_left!(node)
+          # find
+          node_children(node).each { |n| set_left_and_rights(n) }
+          set_right!(node)
+
+          node.save!(:validate => validate_nodes)
+        end
+
+        def node_children(node)
+          model.where(["#{quoted_parent_column_full_name} = ? #{scope_for_rebuild.call(node)}", node]).
+                order(order_for_rebuild)
+        end
+
+        def root_nodes
+          model.where("#{quoted_parent_column_full_name} IS NULL").order(order_for_rebuild)
+        end
+
+        def set_left!(node)
+          node[left_column_name] = increment_indice!(node)
+        end
+
+        def set_right!(node)
+          node[right_column_name] = increment_indice!(node)
+        end
+      end
+    end
+  end
+end
diff --git a/lib/plugins/awesome_nested_set/lib/awesome_nested_set/version.rb b/lib/plugins/awesome_nested_set/lib/awesome_nested_set/version.rb
index 74cac55b8..c7058f7f4 100644
--- a/lib/plugins/awesome_nested_set/lib/awesome_nested_set/version.rb
+++ b/lib/plugins/awesome_nested_set/lib/awesome_nested_set/version.rb
@@ -1,3 +1,3 @@
 module AwesomeNestedSet
-  VERSION = '2.1.6' unless defined?(::AwesomeNestedSet::VERSION)
+  VERSION = '2.1.7' unless defined?(::AwesomeNestedSet::VERSION)
 end
diff --git a/lib/plugins/awesome_nested_set/spec/awesome_nested_set/helper_spec.rb b/lib/plugins/awesome_nested_set/spec/awesome_nested_set/helper_spec.rb
index 0be767f6c..9b2857e04 100644
--- a/lib/plugins/awesome_nested_set/spec/awesome_nested_set/helper_spec.rb
+++ b/lib/plugins/awesome_nested_set/spec/awesome_nested_set/helper_spec.rb
@@ -77,7 +77,10 @@ describe "Helper" do
       actual = nested_set_options(Category.all) do |c|
         "#{'-' * c.level} #{c.name}"
       end
-      actual.should == expected
+      actual.length.should == expected.length
+      expected.flatten.each do |node|
+        actual.flatten.should include(node)
+      end
     end
 
     it "test_nested_set_options_with_array_as_argument_with_mover" do
@@ -90,7 +93,10 @@ describe "Helper" do
       actual = nested_set_options(Category.all, categories(:child_2)) do |c|
         "#{'-' * c.level} #{c.name}"
       end
-      actual.should == expected
+      actual.length.should == expected.length
+      expected.flatten.each do |node|
+        actual.flatten.should include(node)
+      end
     end
   end
 end
diff --git a/lib/plugins/awesome_nested_set/spec/awesome_nested_set_spec.rb b/lib/plugins/awesome_nested_set/spec/awesome_nested_set_spec.rb
index 105bac1ca..60cb888b2 100644
--- a/lib/plugins/awesome_nested_set/spec/awesome_nested_set_spec.rb
+++ b/lib/plugins/awesome_nested_set/spec/awesome_nested_set_spec.rb
@@ -81,6 +81,12 @@ describe "AwesomeNestedSet" do
     Default.new.quoted_depth_column_name.should == quoted
   end
 
+  it "quoted_order_column_name" do
+    quoted = Default.connection.quote_column_name('lft')
+    Default.quoted_order_column_name.should == quoted
+    Default.new.quoted_order_column_name.should == quoted
+  end
+
   it "left_column_protected_from_assignment" do
     lambda {
       Category.new.lft = 1
@@ -104,7 +110,12 @@ describe "AwesomeNestedSet" do
   end
 
   it "roots_class_method" do
-    Category.roots.should == Category.find_all_by_parent_id(nil)
+    found_by_us = Category.where(:parent_id => nil).to_a
+    found_by_roots = Category.roots.to_a
+    found_by_us.length.should == found_by_roots.length
+    found_by_us.each do |root|
+      found_by_roots.should include(root)
+    end
   end
 
   it "root_class_method" do
@@ -131,7 +142,6 @@ describe "AwesomeNestedSet" do
   end
 
   it "leaves_class_method" do
-    Category.find(:all, :conditions => "#{Category.right_column_name} - #{Category.left_column_name} = 1").should == Category.leaves
     Category.leaves.count.should == 4
     Category.leaves.should include(categories(:child_1))
     Category.leaves.should include(categories(:child_2_1))
@@ -158,7 +168,7 @@ describe "AwesomeNestedSet" do
   it "self_and_ancestors" do
     child = categories(:child_2_1)
     self_and_ancestors = [categories(:top_level), categories(:child_2), child]
-    self_and_ancestors.should == child.self_and_ancestors
+    child.self_and_ancestors.should == self_and_ancestors
   end
 
   it "ancestors" do
@@ -433,8 +443,8 @@ describe "AwesomeNestedSet" do
     categories(:child_2).parent.should be_nil
     categories(:child_2).level.should == 0
     categories(:child_2_1).level.should == 1
-    categories(:child_2).left.should == 1
-    categories(:child_2).right.should == 4
+    categories(:child_2).left.should == 7
+    categories(:child_2).right.should == 10
     Category.valid?.should be_true
   end
 
@@ -775,14 +785,14 @@ describe "AwesomeNestedSet" do
 
   it "quoting_of_multi_scope_column_names" do
     ## Proper Array Assignment for different DBs as per their quoting column behavior
-    if Note.connection.adapter_name.match(/Oracle/)
+    if Note.connection.adapter_name.match(/oracle/i)
       expected_quoted_scope_column_names = ["\"NOTABLE_ID\"", "\"NOTABLE_TYPE\""]
-    elsif Note.connection.adapter_name.match(/Mysql/)
+    elsif Note.connection.adapter_name.match(/mysql/i)
       expected_quoted_scope_column_names = ["`notable_id`", "`notable_type`"]
     else
       expected_quoted_scope_column_names = ["\"notable_id\"", "\"notable_type\""]
     end
-    expected_quoted_scope_column_names.should == Note.quoted_scope_column_names
+    Note.quoted_scope_column_names.should == expected_quoted_scope_column_names
   end
 
   it "equal_in_same_scope" do
diff --git a/lib/plugins/awesome_nested_set/spec/spec_helper.rb b/lib/plugins/awesome_nested_set/spec/spec_helper.rb
index d28de5663..2e637bfc8 100644
--- a/lib/plugins/awesome_nested_set/spec/spec_helper.rb
+++ b/lib/plugins/awesome_nested_set/spec/spec_helper.rb
@@ -2,6 +2,7 @@ plugin_test_dir = File.dirname(__FILE__)
 
 require 'rubygems'
 require 'bundler/setup'
+require 'pry'
 
 require 'logger'
 require 'active_record'
@@ -22,6 +23,7 @@ require 'support/models'
 
 require 'action_controller'
 require 'rspec/rails'
+require 'database_cleaner'
 RSpec.configure do |config|
   config.fixture_path = "#{plugin_test_dir}/fixtures"
   config.use_transactional_fixtures = true