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|
# frozen-string-literal: true
module Sequel
module Plugins
# The tree plugin adds additional associations and methods that allow you to
# treat a Model as a tree.
#
# A column for holding the parent key is required and is :parent_id by default.
# This may be overridden by passing column name via :key.
#
# Optionally, a column to control order of nodes returned can be specified
# by passing column name via :order.
#
# If you pass true for the :single_root option, the class will ensure there is
# only ever one root in the tree.
#
# Examples:
#
# class Node < Sequel::Model
# plugin :tree
# end
#
# class Node < Sequel::Model
# plugin :tree, key: :parentid, order: :position
# end
module Tree
# Create parent and children associations. Any options
# specified are passed to both associations. You can also
# specify options to use for just the parent association
# using a :parent option, and options to use for just the
# children association using a :children option.
def self.apply(model, opts=OPTS)
opts = opts.dup
opts[:class] = model
opts[:key] ||= :parent_id
par = opts.merge(opts.fetch(:parent, OPTS))
parent = par.fetch(:name, :parent)
chi = opts.merge(opts.fetch(:children, OPTS))
children = chi.fetch(:name, :children)
par[:reciprocal] = children
chi[:reciprocal] = parent
model.instance_exec do
@parent_column = opts[:key]
@qualified_parent_column = Sequel.deep_qualify(table_name, opts[:key])
@tree_order = opts[:order]
@parent_association_name = parent
@children_association_name = children
many_to_one parent, par
one_to_many children, chi
plugin SingleRoot if opts[:single_root]
end
end
module ClassMethods
# The column symbol or array of column symbols on which to order the tree.
attr_accessor :tree_order
# The symbol or array of symbols for the column containing the value pointing to the
# parent of the node.
attr_accessor :parent_column
# The qualified identifier or array of qualified identifiers for the column
# containing the value pointing to the parent of the node.
attr_accessor :qualified_parent_column
# The association name for the parent association
attr_reader :parent_association_name
# The association name for the children association
attr_reader :children_association_name
Plugins.inherited_instance_variables(self, :@parent_column=>nil, :@qualified_parent_column=>nil, :@tree_order=>nil, :@parent_association_name=>nil, :@children_association_name=>nil)
Plugins.def_dataset_methods(self, [:roots, :roots_dataset])
# Should freeze tree order if it is an array when freezing the model class.
def freeze
@tree_order.freeze if @tree_order.is_a?(Array)
super
end
end
module InstanceMethods
# Returns list of ancestors, starting from parent until root.
#
# subchild1.ancestors # => [child1, root]
def ancestors
node, nodes = self, []
meth = model.parent_association_name
while par = node.send(meth)
nodes << node = par
end
nodes
end
# Returns list of descendants
#
# node.descendants # => [child1, child2, subchild1_1, subchild1_2, subchild2_1, subchild2_2]
def descendants
nodes = send(model.children_association_name).dup
send(model.children_association_name).each{|child| nodes.concat(child.descendants)}
nodes
end
# Returns the root node of the tree that this node descends from.
# This node is returned if it is a root node itself.
def root
ancestors.last || self
end
# Returns true if this is a root node, false otherwise.
def root?
!new? && possible_root?
end
# Returns all siblings and a reference to the current node.
#
# subchild1.self_and_siblings # => [subchild1, subchild2]
def self_and_siblings
if parent = send(model.parent_association_name)
parent.send(model.children_association_name)
else
model.roots
end
end
# Returns all siblings of the current node.
#
# subchild1.siblings # => [subchild2]
def siblings
self_and_siblings - [self]
end
private
# True if if all parent columns values are not NULL.
def possible_root?
!Array(model.parent_column).map{|c| self[c]}.all?
end
end
module DatasetMethods
# Returns list of all root nodes (those with no parent nodes).
#
# TreeClass.roots # => [root1, root2]
def roots
roots_dataset.all
end
# Returns the dataset for retrieval of all root nodes
#
# TreeClass.roots_dataset # => Sequel::Dataset instance
def roots_dataset
ds = where(Sequel.or(Array(model.qualified_parent_column).zip([])))
ds = ds.order(*model.tree_order) if model.tree_order
ds
end
end
# Plugin included when :single_root option is passed.
module SingleRoot
module ClassMethods
# Returns the single root node.
def root
roots_dataset.first
end
end
module InstanceMethods
# Hook that prevents a second root from being created.
def before_save
if possible_root? && (root = model.root) && pk != root.pk
raise TreeMultipleRootError, "there is already a root #{model.name} defined"
end
super
end
end
end
class TreeMultipleRootError < Error; end
end
end
end
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