'use strict'
/**
 *
 * Ashish Patel
 * e: ashishsushilPatel@gmail.com
 * w: https://ashish.me
 *
 */
const ListNode = require('../models/list-node')

class LinkedList {
  constructor() {
    this.root = null
    this.size = 0
  }

  isEmpty() {
    return this.root === null
  }

  // O(1) constant time
  prepend(data) {
    const node = new ListNode(data)
    node.next = this.root
    this.root = node
    this.size += 1
  }

  append(data) {
    this.addAtIndex(this.size, data)
  }

  // O(N) linear time
  toString() {
    let result = 'root ->'
    let current = this.root
    while (current !== null) {
      result += current.data + ' -> '
      current = current.next
    }
    result += 'null'
    return result
  }

  // O(n) linear time
  length() {
    let current = this.root
    let count = 0
    while (current !== null) {
      count++
      current = current.next
    }
    return count
  }

  // O(n) linear time
  get(index) {
    let current = this.root
    let count = 0
    while (current != null) {
      if (count === index) {
        return current.data
      }
      count += 1
      current = current.next
    }
    return null
  }

  // O(n) linear time
  removeAtIndex(index) {
    if (!this.isEmpty()) {
      if (index === 0) {
        this.root = this.root.next
      } else {
        let current = this.root
        let i = 0
        while (current !== null && i < index - 1) {
          current = current.next
          i++
        }
        current.next = current.next.next
      }
      this.size -= 1
    } else {
      return
    }
  }

  addAtIndex(index, data) {
    if (index === 0) {
      this.prepend(data)
    } else {
      let i = 0
      let current = this.root
      let node = new ListNode(data)
      while (current !== null && i < index - 1) {
        i++
        current = current.next
      }
      node.next = current.next
      current.next = node
    }
    this.size += 1
  }
}

const log = console.log
const ll = new LinkedList()
log(ll.length())
log(ll.isEmpty())
ll.prepend(10)
ll.prepend(20)
ll.prepend(30)
ll.prepend(40)
ll.prepend(50)
log(ll.length())
log(ll.toString())
log(ll.get(1))
ll.removeAtIndex(0)
log(ll.toString())
ll.removeAtIndex(2)
log(ll.toString())
ll.removeAtIndex(2)
log(ll.toString())
ll.addAtIndex(1, 100)
log(ll.toString())
log(ll.size)
ll.append(99)
log(ll.toString())
// test('linked List', () => {
//   expect(linkedList('Ashish')).toEqual('Asish')
// })