package com.itjob.data;

public class DoubleLink {
	DNode head;
	DNode rear;
	
	public void add(Object data){
		DNode temp = new DNode(data);
		
		if (head == null){
			head = temp;
			rear = temp;
		}else{
			rear.next = temp;
			temp.previous = rear;
			rear = temp;
		}
	}
	
	public Object pop(){
		
		if (rear != null){
			Object temp = rear.data;
			if (rear == head){	
				rear = rear.previous;
				head = null;
			}else{
				rear = rear.previous;
				rear.next = null;
			}
			return temp;
		}else{
			throw new NullDataException("沒有數據");
		}
	}
	
	public boolean delete(Object data){
		DNode temp = find(data);
		if (temp == null){
			return false;
		}else{
			
			if (temp == rear && temp == head){
				head = null;
				rear = null;
			}else if (temp == head){
				head = temp.next;
				head.previous = null;
			}else if (temp == rear){
				temp.previous.next = null;
				rear = temp.previous;
			}else{
				temp.previous.next = temp.next;
				temp.next.previous = temp.previous;
			}
			return true;
		}
	}
	
	
	
	public DNode find(Object data){
		DNode temp = head;
		
		while (temp != null){
			if (temp.data.equals(data)){
				return temp;
			}
			temp = temp.next;
		}
		return null;
	}
	
	public String toString(){
		StringBuilder result = new StringBuilder("[");
		DNode temp = head;
		while (temp != null){
			if (temp == rear){
				result.append(temp.data);
			}else{
				result.append(temp.data + ",");
			}
			temp = temp.next;
		}
		result.append("]");
		return result.toString();
	}
}