import LinkedListNode from './linked-list-node.js';

export default class DoublyLinkedList {
  #head = null;
  #tail = null;
  #count = 0;
  constructor(){
    this.#head=null;
    this.#tail=null;
    this.#count=0;
  }
  get count() {
    return this.#count;
  }
  get head() {
    return this.#head;
  }
  get tail() {
    return this.#tail;
  }
  get isEmpty() {
    return !this.#head;
  }
  addFirst(value) {
    const node = new LinkedListNode(value);
    if (this.isEmpty) {
      this.#head = node;
      this.#tail = this.#head;
    } else {
      node.next = this.#head;
      this.#head = node;
    }
    this.#count = this.#count + 1;
  }
  addLast(value) {
    const node = new LinkedListNode(value);
    if (this.isEmpty) {
      this.#head = node;
      this.#tail = node;
    } else {
      this.#tail.next = node;
      this.#tail = this.#tail.next;
    }
    this.#count = this.#count + 1;
  }
  removeFirst() {
    if (this.isEmpty){
      throw new Error('node empty');
    }
    const value = this.#head.value;
    this.#head = this.#head.next;
    this.#count--;
    return value;
  }
  removeLast() {
    if (this.isEmpty){
      throw new Error('node empty');
    }
    const value = this.#tail.value;
    this.#tail = this.#tail.prev;
    this.#count--;
    return value;
  }
  insertBefore(node, value) {

    this.#count++;
    const newNode = new LinkedListNode(value);
    if (node.value === this.#head.value) {
      this.#head.prev = newNode;
      newNode.next = this.#head;
      this.#head = newNode;
    }
    newNode.prev = node.prev;
    node.prev.next = newNode;
    newNode.next = node;
  }
  insertAfter(node, value) {
    if(node === null){
      throw new Error('the given node cannot be null');
    }
    const newNode = new LinkedListNode(value);
    newNode.next = node.next;
    node.next = newNode;
    if(node === this.#tail){
      this.#tail.next = newNode;
      this.#tail=this.#tail.next;
    }
    this.#count++;
  }
  find(val) {
    let current = this.#head;
    let final = null;
    while(current){
      if(current.value === val) {
        final = current;
      }
      current =current.next;
    }
    return final;
  }
  values(){
    if(this.isEmpty){
      return [];
    }
    let current = this.#head;
    let final = [];
    while(current){
      final.push(current.value);
      current = current.next;
    }
    return final;
  }
}