import java.awt.*;
import java.awt.event.KeyEvent;
import java.util.LinkedList;

public class Snake {
    private LinkedList<Node> list=new LinkedList<>();
    private Node n = new Node(20, 30, Direction.Left);
    private long lastTime;
    private boolean isDead=false;
    private Node head=null;
    private Yard y;
     float speed=2;


    //构造器
    public Snake(Yard y){
       for(int i=0;i<2;i++) {
           list.addFirst(n);
       }
        this.y = y;
        if(list!=null){
            head=list.getFirst();
        }
    }

    //行走时在头部创建一个方块对象
    public void addToHead(){
        Node node=null;
        switch(head.dir) {
            case Left:
                node = new Node(head.row, head.col - 1, head.dir);
                break;
            case Up:
                node = new Node(head.row - 1, head.col, head.dir);
                break;
            case Right:
                node = new Node(head.row, head.col + 1, head.dir);
                break;
            case Down:
                node = new Node(head.row + 1, head.col, head.dir);
                break;
        }
        list.addFirst(node);
        head=list.getFirst();
    }

    //行走时把后面的尾巴删除
    private void deleteFromTail(){
        if(list.size()==0) return;
        list.removeLast();
    }

    //检测贪吃蛇是否撞到了墙或是否撞到了自己如果撞到了就会gameOver

    private void checkDead(){
        //是否撞墙
        if(head.row < 3 || head.col <1 || head.row > Config.ROWS-1 || head.col >Config.COLS-2)  {
            y.stop();
            isDead=true;
        }
        //是否撞了自己
        for(Node n:list){
            if(head.row==n.row&&head.col==n.col){
               if(n==list.getFirst()) continue;
                y.stop();
                isDead=true;
            }
        }
    }

    //以上三个方法组合成了蛇的移动的方法
    //贪吃蛇移动的方法
    private void move(){
        long current = System.currentTimeMillis();
        if (current - lastTime < 1000/speed) {
            return ;
        }
        else {
            lastTime = current;
        }
        checkDead();
		if(!isDead) {
            addToHead();
            deleteFromTail();
        }
    }

    //画蛇
    public void draw(Graphics g){
        if(list.size()==0) return;
        move();
        for(Node n: list){
            n.draw(g);
        }
    }

    //返回蛇头部的小方块
    private Rectangle getRect() {
        return new Rectangle(Config.BLOCK_SIZE * head.col, Config.BLOCK_SIZE * head.row, head.w, head.h);
    }

    //蛇吃蛋的方法
    public void eat(Egg e){
        if(this.getRect().intersects(e.getRect())){
            e.reAppear();
            this.addToHead();
            //吃掉之后加分数
            y.setScore(y.getScore()+5);
            this.speed= (float) (speed+0.5);
        }
    }

    //通过键盘来控制蛇的方向
    public void keyPressed(KeyEvent e){
        int key=e.getKeyCode();
        switch(key) {
            case KeyEvent.VK_LEFT :
                if(head.dir != Direction.Right)
                    head.dir = Direction.Left;
                break;
            case KeyEvent.VK_UP :
                if(head.dir != Direction.Down)
                    head.dir = Direction.Up;
                break;
            case KeyEvent.VK_RIGHT :
                if(head.dir != Direction.Left)
                    head.dir = Direction.Right;
                break;
            case KeyEvent.VK_DOWN :
                if(head.dir != Direction.Up)
                    head.dir = Direction.Down;
                break;
        }


    }
}