package series08;

public class DLList<T> {
	private int size;
	private DLNode<T> head;
	private DLNode<T> tail;

	public DLList() {
		this.head = null;
		this.tail = null;

	}

	public int size() {
		return size;
	}

	public boolean isEmpty() {
		return this.head == null;
	}

	private DLNode<T> nodeAt(int index) {
		DLNode<T> current;
		if (index > (size / 2)) {
			current = this.tail;
			for (int i = size; i > index; i--) {
				current = current.prev;
			}
		} else {
			current = this.head;
			for (int i = 0; i < index; i++) {
				current = current.next;

			}
		}
		return current;
	}

	private T get(int index) {
		return nodeAt(index).value;
	}

	private void add(T e, int index) {
		DLNode<T> node = new DLNode<T>(null, e, null);

		if (size == 0 && index == 0) {
			head = node;
			tail = head;
		}
		if (size > 0 && index == 0) {
			node.next = head;
			head.prev = node;
			head = node;
		}
		if (size > 0 && index == size()) {
			node.prev = tail;
			tail.next = node;
			// prev.next=node;
			tail = node;

		} else {
			DLNode<T> pred = nodeAt(index - 1);
			node.next = pred.next;
			pred.next.prev = node;
			node.prev = pred;
			pred.next = node;

		}
		size++;

	}

}