Chris@1295: module CollectiveIdea #:nodoc:
Chris@1295:   module Acts #:nodoc:
Chris@1295:     module NestedSet #:nodoc:
Chris@1295: 
Chris@1295:       # This acts provides Nested Set functionality. Nested Set is a smart way to implement
Chris@1295:       # an _ordered_ tree, with the added feature that you can select the children and all of their
Chris@1295:       # descendants with a single query. The drawback is that insertion or move need some complex
Chris@1295:       # sql queries. But everything is done here by this module!
Chris@1295:       #
Chris@1295:       # Nested sets are appropriate each time you want either an orderd tree (menus,
Chris@1295:       # commercial categories) or an efficient way of querying big trees (threaded posts).
Chris@1295:       #
Chris@1295:       # == API
Chris@1295:       #
Chris@1295:       # Methods names are aligned with acts_as_tree as much as possible to make replacment from one
Chris@1295:       # by another easier.
Chris@1295:       #
Chris@1295:       #   item.children.create(:name => "child1")
Chris@1295:       #
Chris@1295: 
Chris@1295:       # Configuration options are:
Chris@1295:       #
Chris@1295:       # * +:parent_column+ - specifies the column name to use for keeping the position integer (default: parent_id)
Chris@1295:       # * +:left_column+ - column name for left boundry data, default "lft"
Chris@1295:       # * +:right_column+ - column name for right boundry data, default "rgt"
Chris@1295:       # * +:scope+ - restricts what is to be considered a list. Given a symbol, it'll attach "_id"
Chris@1295:       #   (if it hasn't been already) and use that as the foreign key restriction. You
Chris@1295:       #   can also pass an array to scope by multiple attributes.
Chris@1295:       #   Example: <tt>acts_as_nested_set :scope => [:notable_id, :notable_type]</tt>
Chris@1295:       # * +:dependent+ - behavior for cascading destroy. If set to :destroy, all the
Chris@1295:       #   child objects are destroyed alongside this object by calling their destroy
Chris@1295:       #   method. If set to :delete_all (default), all the child objects are deleted
Chris@1295:       #   without calling their destroy method.
Chris@1295:       # * +:counter_cache+ adds a counter cache for the number of children.
Chris@1295:       #   defaults to false.
Chris@1295:       #   Example: <tt>acts_as_nested_set :counter_cache => :children_count</tt>
Chris@1295:       #
Chris@1295:       # See CollectiveIdea::Acts::NestedSet::Model::ClassMethods for a list of class methods and
Chris@1295:       # CollectiveIdea::Acts::NestedSet::Model for a list of instance methods added
Chris@1295:       # to acts_as_nested_set models
Chris@1295:       def acts_as_nested_set(options = {})
Chris@1295:         options = {
Chris@1295:           :parent_column => 'parent_id',
Chris@1295:           :left_column => 'lft',
Chris@1295:           :right_column => 'rgt',
Chris@1295:           :dependent => :delete_all, # or :destroy
Chris@1295:           :counter_cache => false,
Chris@1295:           :order => 'id'
Chris@1295:         }.merge(options)
Chris@1295: 
Chris@1295:         if options[:scope].is_a?(Symbol) && options[:scope].to_s !~ /_id$/
Chris@1295:           options[:scope] = "#{options[:scope]}_id".intern
Chris@1295:         end
Chris@1295: 
Chris@1295:         class_attribute :acts_as_nested_set_options
Chris@1295:         self.acts_as_nested_set_options = options
Chris@1295: 
Chris@1295:         include CollectiveIdea::Acts::NestedSet::Model
Chris@1295:         include Columns
Chris@1295:         extend Columns
Chris@1295: 
Chris@1295:         belongs_to :parent, :class_name => self.base_class.to_s,
Chris@1295:           :foreign_key => parent_column_name,
Chris@1295:           :counter_cache => options[:counter_cache],
Chris@1295:           :inverse_of => :children
Chris@1295:         has_many :children, :class_name => self.base_class.to_s,
Chris@1295:           :foreign_key => parent_column_name, :order => left_column_name,
Chris@1295:           :inverse_of => :parent,
Chris@1295:           :before_add    => options[:before_add],
Chris@1295:           :after_add     => options[:after_add],
Chris@1295:           :before_remove => options[:before_remove],
Chris@1295:           :after_remove  => options[:after_remove]
Chris@1295: 
Chris@1295:         attr_accessor :skip_before_destroy
Chris@1295: 
Chris@1295:         before_create  :set_default_left_and_right
Chris@1295:         before_save    :store_new_parent
Chris@1295:         after_save     :move_to_new_parent
Chris@1295:         before_destroy :destroy_descendants
Chris@1295: 
Chris@1295:         # no assignment to structure fields
Chris@1295:         [left_column_name, right_column_name].each do |column|
Chris@1295:           module_eval <<-"end_eval", __FILE__, __LINE__
Chris@1295:             def #{column}=(x)
Chris@1295:               raise ActiveRecord::ActiveRecordError, "Unauthorized assignment to #{column}: it's an internal field handled by acts_as_nested_set code, use move_to_* methods instead."
Chris@1295:             end
Chris@1295:           end_eval
Chris@1295:         end
Chris@1295: 
Chris@1295:         define_model_callbacks :move
Chris@1295:       end
Chris@1295: 
Chris@1295:       module Model
Chris@1295:         extend ActiveSupport::Concern
Chris@1295: 
Chris@1295:         module ClassMethods
Chris@1295:           # Returns the first root
Chris@1295:           def root
Chris@1295:             roots.first
Chris@1295:           end
Chris@1295: 
Chris@1295:           def roots
Chris@1295:             where(parent_column_name => nil).order(quoted_left_column_name)
Chris@1295:           end
Chris@1295: 
Chris@1295:           def leaves
Chris@1295:             where("#{quoted_right_column_name} - #{quoted_left_column_name} = 1").order(quoted_left_column_name)
Chris@1295:           end
Chris@1295: 
Chris@1295:           def valid?
Chris@1295:             left_and_rights_valid? && no_duplicates_for_columns? && all_roots_valid?
Chris@1295:           end
Chris@1295: 
Chris@1295:           def left_and_rights_valid?
Chris@1295:             joins("LEFT OUTER JOIN #{quoted_table_name} AS parent ON " +
Chris@1295:                 "#{quoted_table_name}.#{quoted_parent_column_name} = parent.#{primary_key}").
Chris@1295:             where(
Chris@1295:                 "#{quoted_table_name}.#{quoted_left_column_name} IS NULL OR " +
Chris@1295:                 "#{quoted_table_name}.#{quoted_right_column_name} IS NULL OR " +
Chris@1295:                 "#{quoted_table_name}.#{quoted_left_column_name} >= " +
Chris@1295:                   "#{quoted_table_name}.#{quoted_right_column_name} OR " +
Chris@1295:                 "(#{quoted_table_name}.#{quoted_parent_column_name} IS NOT NULL AND " +
Chris@1295:                   "(#{quoted_table_name}.#{quoted_left_column_name} <= parent.#{quoted_left_column_name} OR " +
Chris@1295:                   "#{quoted_table_name}.#{quoted_right_column_name} >= parent.#{quoted_right_column_name}))"
Chris@1295:             ).count == 0
Chris@1295:           end
Chris@1295: 
Chris@1295:           def no_duplicates_for_columns?
Chris@1295:             scope_string = Array(acts_as_nested_set_options[:scope]).map do |c|
Chris@1295:               connection.quote_column_name(c)
Chris@1295:             end.push(nil).join(", ")
Chris@1295:             [quoted_left_column_name, quoted_right_column_name].all? do |column|
Chris@1295:               # No duplicates
Chris@1295:               select("#{scope_string}#{column}, COUNT(#{column})").
Chris@1295:                   group("#{scope_string}#{column}").
Chris@1295:                   having("COUNT(#{column}) > 1").
Chris@1295:                   first.nil?
Chris@1295:             end
Chris@1295:           end
Chris@1295: 
Chris@1295:           # Wrapper for each_root_valid? that can deal with scope.
Chris@1295:           def all_roots_valid?
Chris@1295:             if acts_as_nested_set_options[:scope]
Chris@1295:               roots.group(scope_column_names).group_by{|record| scope_column_names.collect{|col| record.send(col.to_sym)}}.all? do |scope, grouped_roots|
Chris@1295:                 each_root_valid?(grouped_roots)
Chris@1295:               end
Chris@1295:             else
Chris@1295:               each_root_valid?(roots)
Chris@1295:             end
Chris@1295:           end
Chris@1295: 
Chris@1295:           def each_root_valid?(roots_to_validate)
Chris@1295:             left = right = 0
Chris@1295:             roots_to_validate.all? do |root|
Chris@1295:               (root.left > left && root.right > right).tap do
Chris@1295:                 left = root.left
Chris@1295:                 right = root.right
Chris@1295:               end
Chris@1295:             end
Chris@1295:           end
Chris@1295: 
Chris@1295:           # Rebuilds the left & rights if unset or invalid.
Chris@1295:           # Also very useful for converting from acts_as_tree.
Chris@1295:           def rebuild!(validate_nodes = true)
Chris@1295:             # Don't rebuild a valid tree.
Chris@1295:             return true if valid?
Chris@1295: 
Chris@1295:             scope = lambda{|node|}
Chris@1295:             if acts_as_nested_set_options[:scope]
Chris@1295:               scope = lambda{|node|
Chris@1295:                 scope_column_names.inject(""){|str, column_name|
Chris@1295:                   str << "AND #{connection.quote_column_name(column_name)} = #{connection.quote(node.send(column_name.to_sym))} "
Chris@1295:                 }
Chris@1295:               }
Chris@1295:             end
Chris@1295:             indices = {}
Chris@1295: 
Chris@1295:             set_left_and_rights = lambda do |node|
Chris@1295:               # set left
Chris@1295:               node[left_column_name] = indices[scope.call(node)] += 1
Chris@1295:               # find
Chris@1295:               where(["#{quoted_parent_column_name} = ? #{scope.call(node)}", node]).order(acts_as_nested_set_options[:order]).each{|n| set_left_and_rights.call(n) }
Chris@1295:               # set right
Chris@1295:               node[right_column_name] = indices[scope.call(node)] += 1
Chris@1295:               node.save!(:validate => validate_nodes)
Chris@1295:             end
Chris@1295: 
Chris@1295:             # Find root node(s)
Chris@1295:             root_nodes = where("#{quoted_parent_column_name} IS NULL").order(acts_as_nested_set_options[:order]).each do |root_node|
Chris@1295:               # setup index for this scope
Chris@1295:               indices[scope.call(root_node)] ||= 0
Chris@1295:               set_left_and_rights.call(root_node)
Chris@1295:             end
Chris@1295:           end
Chris@1295: 
Chris@1295:           # Iterates over tree elements and determines the current level in the tree.
Chris@1295:           # Only accepts default ordering, odering by an other column than lft
Chris@1295:           # does not work. This method is much more efficent than calling level
Chris@1295:           # because it doesn't require any additional database queries.
Chris@1295:           #
Chris@1295:           # Example:
Chris@1295:           #    Category.each_with_level(Category.root.self_and_descendants) do |o, level|
Chris@1295:           #
Chris@1295:           def each_with_level(objects)
Chris@1295:             path = [nil]
Chris@1295:             objects.each do |o|
Chris@1295:               if o.parent_id != path.last
Chris@1295:                 # we are on a new level, did we decent or ascent?
Chris@1295:                 if path.include?(o.parent_id)
Chris@1295:                   # remove wrong wrong tailing paths elements
Chris@1295:                   path.pop while path.last != o.parent_id
Chris@1295:                 else
Chris@1295:                   path << o.parent_id
Chris@1295:                 end
Chris@1295:               end
Chris@1295:               yield(o, path.length - 1)
Chris@1295:             end
Chris@1295:           end
Chris@1295:         end
Chris@1295: 
Chris@1295:         # 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.
Chris@1295:         #
Chris@1295:         #   category.self_and_descendants.count
Chris@1295:         #   category.ancestors.find(:all, :conditions => "name like '%foo%'")
Chris@1295: 
Chris@1295:         # Value of the parent column
Chris@1295:         def parent_id
Chris@1295:           self[parent_column_name]
Chris@1295:         end
Chris@1295: 
Chris@1295:         # Value of the left column
Chris@1295:         def left
Chris@1295:           self[left_column_name]
Chris@1295:         end
Chris@1295: 
Chris@1295:         # Value of the right column
Chris@1295:         def right
Chris@1295:           self[right_column_name]
Chris@1295:         end
Chris@1295: 
Chris@1295:         # Returns true if this is a root node.
Chris@1295:         def root?
Chris@1295:           parent_id.nil?
Chris@1295:         end
Chris@1295: 
Chris@1295:         def leaf?
Chris@1295:           new_record? || (right - left == 1)
Chris@1295:         end
Chris@1295: 
Chris@1295:         # Returns true is this is a child node
Chris@1295:         def child?
Chris@1295:           !parent_id.nil?
Chris@1295:         end
Chris@1295: 
Chris@1295:         # Returns root
Chris@1295:         def root
Chris@1295:           self_and_ancestors.where(parent_column_name => nil).first
Chris@1295:         end
Chris@1295: 
Chris@1295:         # Returns the array of all parents and self
Chris@1295:         def self_and_ancestors
Chris@1295:           nested_set_scope.where([
Chris@1295:             "#{self.class.quoted_table_name}.#{quoted_left_column_name} <= ? AND #{self.class.quoted_table_name}.#{quoted_right_column_name} >= ?", left, right
Chris@1295:           ])
Chris@1295:         end
Chris@1295: 
Chris@1295:         # Returns an array of all parents
Chris@1295:         def ancestors
Chris@1295:           without_self self_and_ancestors
Chris@1295:         end
Chris@1295: 
Chris@1295:         # Returns the array of all children of the parent, including self
Chris@1295:         def self_and_siblings
Chris@1295:           nested_set_scope.where(parent_column_name => parent_id)
Chris@1295:         end
Chris@1295: 
Chris@1295:         # Returns the array of all children of the parent, except self
Chris@1295:         def siblings
Chris@1295:           without_self self_and_siblings
Chris@1295:         end
Chris@1295: 
Chris@1295:         # Returns a set of all of its nested children which do not have children
Chris@1295:         def leaves
Chris@1295:           descendants.where("#{self.class.quoted_table_name}.#{quoted_right_column_name} - #{self.class.quoted_table_name}.#{quoted_left_column_name} = 1")
Chris@1295:         end
Chris@1295: 
Chris@1295:         # Returns the level of this object in the tree
Chris@1295:         # root level is 0
Chris@1295:         def level
Chris@1295:           parent_id.nil? ? 0 : ancestors.count
Chris@1295:         end
Chris@1295: 
Chris@1295:         # Returns a set of itself and all of its nested children
Chris@1295:         def self_and_descendants
Chris@1295:           nested_set_scope.where([
Chris@1295:             "#{self.class.quoted_table_name}.#{quoted_left_column_name} >= ? AND #{self.class.quoted_table_name}.#{quoted_right_column_name} <= ?", left, right
Chris@1295:           ])
Chris@1295:         end
Chris@1295: 
Chris@1295:         # Returns a set of all of its children and nested children
Chris@1295:         def descendants
Chris@1295:           without_self self_and_descendants
Chris@1295:         end
Chris@1295: 
Chris@1295:         def is_descendant_of?(other)
Chris@1295:           other.left < self.left && self.left < other.right && same_scope?(other)
Chris@1295:         end
Chris@1295: 
Chris@1295:         def is_or_is_descendant_of?(other)
Chris@1295:           other.left <= self.left && self.left < other.right && same_scope?(other)
Chris@1295:         end
Chris@1295: 
Chris@1295:         def is_ancestor_of?(other)
Chris@1295:           self.left < other.left && other.left < self.right && same_scope?(other)
Chris@1295:         end
Chris@1295: 
Chris@1295:         def is_or_is_ancestor_of?(other)
Chris@1295:           self.left <= other.left && other.left < self.right && same_scope?(other)
Chris@1295:         end
Chris@1295: 
Chris@1295:         # Check if other model is in the same scope
Chris@1295:         def same_scope?(other)
Chris@1295:           Array(acts_as_nested_set_options[:scope]).all? do |attr|
Chris@1295:             self.send(attr) == other.send(attr)
Chris@1295:           end
Chris@1295:         end
Chris@1295: 
Chris@1295:         # Find the first sibling to the left
Chris@1295:         def left_sibling
Chris@1295:           siblings.where(["#{self.class.quoted_table_name}.#{quoted_left_column_name} < ?", left]).
Chris@1295:                   order("#{self.class.quoted_table_name}.#{quoted_left_column_name} DESC").last
Chris@1295:         end
Chris@1295: 
Chris@1295:         # Find the first sibling to the right
Chris@1295:         def right_sibling
Chris@1295:           siblings.where(["#{self.class.quoted_table_name}.#{quoted_left_column_name} > ?", left]).first
Chris@1295:         end
Chris@1295: 
Chris@1295:         # Shorthand method for finding the left sibling and moving to the left of it.
Chris@1295:         def move_left
Chris@1295:           move_to_left_of left_sibling
Chris@1295:         end
Chris@1295: 
Chris@1295:         # Shorthand method for finding the right sibling and moving to the right of it.
Chris@1295:         def move_right
Chris@1295:           move_to_right_of right_sibling
Chris@1295:         end
Chris@1295: 
Chris@1295:         # Move the node to the left of another node (you can pass id only)
Chris@1295:         def move_to_left_of(node)
Chris@1295:           move_to node, :left
Chris@1295:         end
Chris@1295: 
Chris@1295:         # Move the node to the left of another node (you can pass id only)
Chris@1295:         def move_to_right_of(node)
Chris@1295:           move_to node, :right
Chris@1295:         end
Chris@1295: 
Chris@1295:         # Move the node to the child of another node (you can pass id only)
Chris@1295:         def move_to_child_of(node)
Chris@1295:           move_to node, :child
Chris@1295:         end
Chris@1295: 
Chris@1295:         # Move the node to root nodes
Chris@1295:         def move_to_root
Chris@1295:           move_to nil, :root
Chris@1295:         end
Chris@1295: 
Chris@1295:         def move_possible?(target)
Chris@1295:           self != target && # Can't target self
Chris@1295:           same_scope?(target) && # can't be in different scopes
Chris@1295:           # !(left..right).include?(target.left..target.right) # this needs tested more
Chris@1295:           # detect impossible move
Chris@1295:           !((left <= target.left && right >= target.left) or (left <= target.right && right >= target.right))
Chris@1295:         end
Chris@1295: 
Chris@1295:         def to_text
Chris@1295:           self_and_descendants.map do |node|
Chris@1295:             "#{'*'*(node.level+1)} #{node.id} #{node.to_s} (#{node.parent_id}, #{node.left}, #{node.right})"
Chris@1295:           end.join("\n")
Chris@1295:         end
Chris@1295: 
Chris@1295:       protected
Chris@1295: 
Chris@1295:         def without_self(scope)
Chris@1295:           scope.where(["#{self.class.quoted_table_name}.#{self.class.primary_key} != ?", self])
Chris@1295:         end
Chris@1295: 
Chris@1295:         # All nested set queries should use this nested_set_scope, which performs finds on
Chris@1295:         # the base ActiveRecord class, using the :scope declared in the acts_as_nested_set
Chris@1295:         # declaration.
Chris@1295:         def nested_set_scope(options = {})
Chris@1295:           options = {:order => "#{self.class.quoted_table_name}.#{quoted_left_column_name}"}.merge(options)
Chris@1295:           scopes = Array(acts_as_nested_set_options[:scope])
Chris@1295:           options[:conditions] = scopes.inject({}) do |conditions,attr|
Chris@1295:             conditions.merge attr => self[attr]
Chris@1295:           end unless scopes.empty?
Chris@1295:           self.class.base_class.scoped options
Chris@1295:         end
Chris@1295: 
Chris@1295:         def store_new_parent
Chris@1295:           @move_to_new_parent_id = send("#{parent_column_name}_changed?") ? parent_id : false
Chris@1295:           true # force callback to return true
Chris@1295:         end
Chris@1295: 
Chris@1295:         def move_to_new_parent
Chris@1295:           if @move_to_new_parent_id.nil?
Chris@1295:             move_to_root
Chris@1295:           elsif @move_to_new_parent_id
Chris@1295:             move_to_child_of(@move_to_new_parent_id)
Chris@1295:           end
Chris@1295:         end
Chris@1295: 
Chris@1295:         # on creation, set automatically lft and rgt to the end of the tree
Chris@1295:         def set_default_left_and_right
Chris@1295:           highest_right_row = nested_set_scope(:order => "#{quoted_right_column_name} desc").limit(1).lock(true).first
Chris@1295:           maxright = highest_right_row ? (highest_right_row[right_column_name] || 0) : 0
Chris@1295:           # adds the new node to the right of all existing nodes
Chris@1295:           self[left_column_name] = maxright + 1
Chris@1295:           self[right_column_name] = maxright + 2
Chris@1295:         end
Chris@1295: 
Chris@1295:         def in_tenacious_transaction(&block)
Chris@1295:           retry_count = 0
Chris@1295:           begin
Chris@1295:             transaction(&block)
Chris@1295:           rescue ActiveRecord::StatementInvalid => error
Chris@1295:             raise unless connection.open_transactions.zero?
Chris@1295:             raise unless error.message =~ /Deadlock found when trying to get lock|Lock wait timeout exceeded/
Chris@1295:             raise unless retry_count < 10
Chris@1295:             retry_count += 1
Chris@1295:             logger.info "Deadlock detected on retry #{retry_count}, restarting transaction"
Chris@1295:             sleep(rand(retry_count)*0.1) # Aloha protocol
Chris@1295:             retry
Chris@1295:           end
Chris@1295:         end
Chris@1295: 
Chris@1295:         # Prunes a branch off of the tree, shifting all of the elements on the right
Chris@1295:         # back to the left so the counts still work.
Chris@1295:         def destroy_descendants
Chris@1295:           return if right.nil? || left.nil? || skip_before_destroy
Chris@1295: 
Chris@1295:           in_tenacious_transaction do
Chris@1295:             reload_nested_set
Chris@1295:             # select the rows in the model that extend past the deletion point and apply a lock
Chris@1295:             self.class.base_class.
Chris@1295:               select("id").
Chris@1295:               where("#{quoted_left_column_name} >= ?", left).
Chris@1295:               lock(true).
Chris@1295:               all
Chris@1295: 
Chris@1295:             if acts_as_nested_set_options[:dependent] == :destroy
Chris@1295:               descendants.each do |model|
Chris@1295:                 model.skip_before_destroy = true
Chris@1295:                 model.destroy
Chris@1295:               end
Chris@1295:             else
Chris@1295:               nested_set_scope.delete_all(
Chris@1295:                 ["#{quoted_left_column_name} > ? AND #{quoted_right_column_name} < ?",
Chris@1295:                   left, right]
Chris@1295:               )
Chris@1295:             end
Chris@1295: 
Chris@1295:             # update lefts and rights for remaining nodes
Chris@1295:             diff = right - left + 1
Chris@1295:             nested_set_scope.update_all(
Chris@1295:               ["#{quoted_left_column_name} = (#{quoted_left_column_name} - ?)", diff],
Chris@1295:               ["#{quoted_left_column_name} > ?", right]
Chris@1295:             )
Chris@1295:             nested_set_scope.update_all(
Chris@1295:               ["#{quoted_right_column_name} = (#{quoted_right_column_name} - ?)", diff],
Chris@1295:               ["#{quoted_right_column_name} > ?", right]
Chris@1295:               )
Chris@1295:               
Chris@1295: reload
Chris@1295:               # Don't allow multiple calls to destroy to corrupt the set
Chris@1295:             self.skip_before_destroy = true
Chris@1295:           end
Chris@1295:         end
Chris@1295: 
Chris@1295:         # reload left, right, and parent
Chris@1295:         def reload_nested_set
Chris@1295:           reload(
Chris@1295:             :select => "#{quoted_left_column_name}, #{quoted_right_column_name}, #{quoted_parent_column_name}",
Chris@1295:             :lock => true
Chris@1295:           )
Chris@1295:         end
Chris@1295: 
Chris@1295:         def move_to(target, position)
Chris@1295:           raise ActiveRecord::ActiveRecordError, "You cannot move a new node" if self.new_record?
Chris@1295:           run_callbacks :move do
Chris@1295:             in_tenacious_transaction do
Chris@1295:               if target.is_a? self.class.base_class
Chris@1295:                 target.reload_nested_set
Chris@1295:               elsif position != :root
Chris@1295:                 # load object if node is not an object
Chris@1295:                 target = nested_set_scope.find(target)
Chris@1295:               end
Chris@1295:               self.reload_nested_set
Chris@1295: 
Chris@1295:               unless position == :root || move_possible?(target)
Chris@1295:                 raise ActiveRecord::ActiveRecordError, "Impossible move, target node cannot be inside moved tree."
Chris@1295:               end
Chris@1295: 
Chris@1295:               bound = case position
Chris@1295:                 when :child;  target[right_column_name]
Chris@1295:                 when :left;   target[left_column_name]
Chris@1295:                 when :right;  target[right_column_name] + 1
Chris@1295:                 when :root;   1
Chris@1295:                 else raise ActiveRecord::ActiveRecordError, "Position should be :child, :left, :right or :root ('#{position}' received)."
Chris@1295:               end
Chris@1295: 
Chris@1295:               if bound > self[right_column_name]
Chris@1295:                 bound = bound - 1
Chris@1295:                 other_bound = self[right_column_name] + 1
Chris@1295:               else
Chris@1295:                 other_bound = self[left_column_name] - 1
Chris@1295:               end
Chris@1295: 
Chris@1295:               # there would be no change
Chris@1295:               return if bound == self[right_column_name] || bound == self[left_column_name]
Chris@1295: 
Chris@1295:               # we have defined the boundaries of two non-overlapping intervals,
Chris@1295:               # so sorting puts both the intervals and their boundaries in order
Chris@1295:               a, b, c, d = [self[left_column_name], self[right_column_name], bound, other_bound].sort
Chris@1295: 
Chris@1295:               # select the rows in the model between a and d, and apply a lock
Chris@1295:               self.class.base_class.select('id').lock(true).where(
Chris@1295:                 ["#{quoted_left_column_name} >= :a and #{quoted_right_column_name} <= :d", {:a => a, :d => d}]
Chris@1295:               )
Chris@1295: 
Chris@1295:               new_parent = case position
Chris@1295:                 when :child;  target.id
Chris@1295:                 when :root;   nil
Chris@1295:                 else          target[parent_column_name]
Chris@1295:               end
Chris@1295: 
Chris@1295:               self.nested_set_scope.update_all([
Chris@1295:                 "#{quoted_left_column_name} = CASE " +
Chris@1295:                   "WHEN #{quoted_left_column_name} BETWEEN :a AND :b " +
Chris@1295:                     "THEN #{quoted_left_column_name} + :d - :b " +
Chris@1295:                   "WHEN #{quoted_left_column_name} BETWEEN :c AND :d " +
Chris@1295:                     "THEN #{quoted_left_column_name} + :a - :c " +
Chris@1295:                   "ELSE #{quoted_left_column_name} END, " +
Chris@1295:                 "#{quoted_right_column_name} = CASE " +
Chris@1295:                   "WHEN #{quoted_right_column_name} BETWEEN :a AND :b " +
Chris@1295:                     "THEN #{quoted_right_column_name} + :d - :b " +
Chris@1295:                   "WHEN #{quoted_right_column_name} BETWEEN :c AND :d " +
Chris@1295:                     "THEN #{quoted_right_column_name} + :a - :c " +
Chris@1295:                   "ELSE #{quoted_right_column_name} END, " +
Chris@1295:                 "#{quoted_parent_column_name} = CASE " +
Chris@1295:                   "WHEN #{self.class.base_class.primary_key} = :id THEN :new_parent " +
Chris@1295:                   "ELSE #{quoted_parent_column_name} END",
Chris@1295:                 {:a => a, :b => b, :c => c, :d => d, :id => self.id, :new_parent => new_parent}
Chris@1295:               ])
Chris@1295:             end
Chris@1295:             target.reload_nested_set if target
Chris@1295:             self.reload_nested_set
Chris@1295:           end
Chris@1295:         end
Chris@1295: 
Chris@1295:       end
Chris@1295: 
Chris@1295:       # Mixed into both classes and instances to provide easy access to the column names
Chris@1295:       module Columns
Chris@1295:         def left_column_name
Chris@1295:           acts_as_nested_set_options[:left_column]
Chris@1295:         end
Chris@1295: 
Chris@1295:         def right_column_name
Chris@1295:           acts_as_nested_set_options[:right_column]
Chris@1295:         end
Chris@1295: 
Chris@1295:         def parent_column_name
Chris@1295:           acts_as_nested_set_options[:parent_column]
Chris@1295:         end
Chris@1295: 
Chris@1295:         def scope_column_names
Chris@1295:           Array(acts_as_nested_set_options[:scope])
Chris@1295:         end
Chris@1295: 
Chris@1295:         def quoted_left_column_name
Chris@1295:           connection.quote_column_name(left_column_name)
Chris@1295:         end
Chris@1295: 
Chris@1295:         def quoted_right_column_name
Chris@1295:           connection.quote_column_name(right_column_name)
Chris@1295:         end
Chris@1295: 
Chris@1295:         def quoted_parent_column_name
Chris@1295:           connection.quote_column_name(parent_column_name)
Chris@1295:         end
Chris@1295: 
Chris@1295:         def quoted_scope_column_names
Chris@1295:           scope_column_names.collect {|column_name| connection.quote_column_name(column_name) }
Chris@1295:         end
Chris@1295:       end
Chris@1295: 
Chris@1295:     end
Chris@1295:   end
Chris@1295: end