class Async::Node

def add_child child
 ||= Children.new
.insert(child)
_parent(self)

def annotate(annotation)
	if block_given?
		previous_annotation = @annotation
		@annotation = annotation
		yield
		@annotation = previous_annotation
	else
		@annotation = annotation
	end
end

def backtrace(*arguments)
	nil
end

def children?
	@children != nil && !@children.empty?
end

def consume
	if parent = @parent and finished?
		parent.delete_child(self)
		
		if @children
			@children.each do |child|
				if child.finished?
					delete_child(child)
				else
					parent.add_child(child)
				end
			end
			
			@children = nil
		end
		
		parent.consume
	end
end

def delete_child(child)
.delete(child)
_parent(nil)

def description
	@object_name ||= "#{self.class}:0x#{object_id.to_s(16)}#{@transient ? ' transient' : nil}"
	
	if @annotation
		"#{@object_name} #{@annotation}"
	else
		@object_name
	end
end

def finished?
	@children.nil? || @children.finished?
end

def initialize(parent = nil, annotation: nil, transient: false)
	@parent = nil
	@children = nil
	
	@annotation = annotation
	@object_name = nil
	
	@transient = transient
	
	@head = nil
	@tail = nil
	
	if parent
		parent.add_child(self)
	end
end

def parent=(parent)
	return if @parent.equal?(parent)
	
	if @parent
		@parent.delete_child(self)
		@parent = nil
	end
	
	if parent
		parent.add_child(self)
	end
	
	return self
end

def print_backtrace(out, indent, node)
	if backtrace = node.backtrace
		backtrace.each_with_index do |line, index|
			out.puts "#{indent}#{index.zero? ? "→ " : "  "}#{line}"
		end
	end
end

def print_hierarchy(out = $stdout, backtrace: true)
	self.traverse do |node, level|
		indent = "\t" * level
		
		out.puts "#{indent}#{node}"
		
		print_backtrace(out, indent, node) if backtrace
	end
end

def set_parent parent
 parent

def stop
	@children&.each(&:stop)
end

def to_s
	"\#<#{description}>"
end

def transient?
	@transient
end

def traverse(level = 0, &block)
	yield self, level
	
	@children&.each do |child|
		child.traverse(level + 1, &block)
	end
end