import LinkedList, { LinkedListElement } from './linked_list'

/**
 * Class implements circular bidirectional linked list <br/>
 * LinkedListElement - object of any type that has properties next and prev.
 */
class CircularLinkedList<T extends LinkedListElement<T>> extends LinkedList<T> {
  constructor(first?: T, last?: T) {
    super(first, last)
    this.setCircularLinks()
  }

  setCircularLinks() {
    if (this.isEmpty()) return
    this.last.next = this.first
    this.first.prev = this.last
  }

  [Symbol.iterator]() {
    let element = undefined
    return {
      next: () => {
        let value = element ? element : this.first
        let done = this.first ? (element ? element === this.first : false) : true
        element = value ? value.next : undefined
        return { value: value, done: done }
      },
    }
  }

  /**
   * Append new element to the end of the list
   * @param element - new element to be appended
   */
  append(element: T) {
    super.append(element)
    this.setCircularLinks()
    return this
  }

  /**
   * Insert new element to the list after elementBefore
   */
  insert(newElement: T, elementBefore: T) {
    super.insert(newElement, elementBefore)
    this.setCircularLinks()
    return this
  }

  /**
   * Remove element from the list
   */
  remove(element: T) {
    super.remove(element)
    return this
  }
}

export default CircularLinkedList