export class Node<T>{
  data: T;
  prev: Node<T> = null;
  next: Node<T> = null;
  
  constructor(data: T) {
    this.data = data;
  }
}

// create a node and optionally link it with previous one (in a circular doubly linked list)
export function insertNode<T>(data: T, last: Node<T> | null) {
  const p = new Node(data);

  if (last === null) {
    p.prev = p;
    p.next = p;
  } else {
    p.next = last.next;
    p.prev = last;
    last.next.prev = p;
    last.next = p;
  }
  return p;
}

export function removeNode<T>(p: Node<T>) {
  p.next.prev = p.prev;
  p.prev.next = p.next;
}