package com.careercup.linkedlist;

public class DoubleLinkedList<AnyType> {

  private Node<AnyType> nodeFirst;
  private Node<AnyType> nodeLast;
  private Node<AnyType> nodeIndex;

  public DoubleLinkedList() {
    nodeFirst = null;
    nodeLast = null;
  }

  public void iterReset() {
    nodeIndex = nodeFirst;
  }

  public AnyType iterNext() {
    AnyType data = null;
    if (nodeIndex != null) {
      data = nodeIndex.getData();
    }
    Node<AnyType> nodeNext = nodeIndex.getNext();
    if (nodeNext != null) {
      nodeIndex = nodeNext;
    }
    return data;
  }

  public AnyType iterPrev() {
    AnyType data = null;
    if (nodeIndex != null) {
      data = nodeIndex.getData();
    }
    Node<AnyType> nodePrev = nodeIndex.getPrev();
    if (nodePrev != null) {
      nodeIndex = nodePrev;
    }
    return data;
  }

  public void addLast( AnyType data ) {
    Node<AnyType> nodeNew = new Node<AnyType>(data);

    if (nodeFirst == null) {
      nodeFirst = nodeLast = nodeNew;
      return;
    }

    nodeNew.setPrev(nodeLast);

    nodeLast.setNext(nodeNew);

    nodeLast = nodeNew;

  }

  public void addFirst( AnyType data ) {
    Node<AnyType> nodeNew = new Node<AnyType>(data);

    if (nodeFirst == null) {
      nodeFirst = nodeLast = nodeNew;
      return;
    }

    nodeNew.setNext(nodeFirst);

    nodeFirst.setPrev(nodeNew);

    nodeFirst = nodeNew;

  }

  public class Node<AnyType> {

    private AnyType       data;
    private Node<AnyType> next;
    private Node<AnyType> prev;

    public Node( AnyType data ) {
      this.data = data;
    }

    public Node<AnyType> getNext() {
      return next;
    }

    public void setNext( Node<AnyType> next ) {
      this.next = next;
    }

    public Node<AnyType> getPrev() {
      return prev;
    }

    public void setPrev( Node<AnyType> prev ) {
      this.prev = prev;
    }

    public AnyType getData() {
      return data;
    }

  }

  public static void main( String[] args ) {

    DoubleLinkedList<Integer> list = new DoubleLinkedList<>();

    list.addLast(2);
    list.addLast(3);
    list.addFirst(1);
    list.addFirst(0);

    list.iterReset();

    for (int idx = 0; idx < 8; idx++) {
      System.out.printf("%d ", list.iterNext());
    }
    System.out.println();

    for (int idx = 0; idx < 8; idx++) {
      System.out.printf("%d ", list.iterPrev());
    }
    System.out.println();

  }

}