package tools

type Node[T any] struct {
	value  T
	before *Node[T]
	after  *Node[T]
}

type List[T any] struct {
	front *Node[T]
	back  *Node[T]
	size  uint
}

func New[T any]() List[T] {
	return List[T]{nil, nil, 0}
}

func (l *List[T]) PushFront(t T) {
	item := &Node[T]{t, nil, nil}

	if l.back == nil {
		l.back = item
	}

	if front := l.front; front != nil {
		front.before, item.after = item, front
	}

	l.size++
	l.front = item
}

func (l *List[T]) PopBack() (result T, good bool) {
	if l.back == nil {
		return
	}

	result = l.back.value
	good = true

	if l.front == l.back {
		l.front = nil
	}

	if before := l.back.before; before != nil {
		before.after = nil
	}

	l.size--
	l.back = l.back.before
	return
}

func (l *List[T]) Size() uint {
	return l.size
}