import javax.swing.*;
import java.awt.*;
import java.util.Queue;
import java.util.LinkedList;
import java.awt.event.*;
import java.util.Random;

public class Main extends JPanel implements KeyListener{
	
    /*以下包括本注释请在编译前删除，否则可能在一些计算机上编译错误*/
	public static int shu = 12,heng = 15;  //行数，列数
	public static int block_size = 80;     //每格边长(>8)
	private mpair dir,dir_real;
	
	private Queue<mpair> snake_que = new LinkedList<mpair>();
	private mpair front;
	private mpair food;
	private int size_init = 3;  //初始长度

	private int size_change = 0;
	private int zengjia = 3;   //每次长度增加的长度

	private int sleep_time = 100;  //每次刷新后睡眠时间(最好不要太短)
	
	public static void main(String args[]) {
		
		JFrame mf = new JFrame();
		mf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		
		mf.setBounds(20,20,heng*block_size,shu*block_size+20);
		Main mp = new Main();
		
		mf.add(mp);
		mf.setVisible(true);
		mp.requestFocus();
		mf.setResizable(false);
		
		while(true) {
			try {
           		Thread.sleep(mp.sleep_time);
       		} catch (InterruptedException e) {}
       		mp.change();
       		if(mp.test_dead()==true) {
       			System.exit(0);
			}
       		mp.test_food();
       		mp.repaint();
		}
	}
	private void add_food() {

		Random rand_x = new Random();
		Random rand_y = new Random();
		while(true) {
			this.food = new mpair(rand_x.nextInt(shu)+1,rand_y.nextInt(heng)+1);

			boolean boo = true;
			for(mpair i: this.snake_que) {
				if(food.a == i.a && food.b == i.b) {
					boo = false;
					break;
				}
			}
			if(boo) return;
		}
	}
	public void test_food() {

		if(this.front.a == this.food.a && this.front.b == this.food.b) {
			this.add_food();
			this.size_change = this.zengjia;
		}
	}
	public boolean test_dead() {
		int u=1;
		for(mpair i : this.snake_que) {

			if((i.a == front.a && i.b == front.b) && u!=this.snake_que.size()) {
				return true;
			}
			u++;
		}
		return false;
	}
	public void paint(Graphics g) {
        super.paint(g);
        g.setColor(new Color(0,0,0));
        g.fillRect(0,0,this.block_size*heng,this.block_size*shu);
        g.setColor(new Color(255,255,255));
        
        for(mpair i : this.snake_que) {
            g.fillRect((i.b-1)*block_size+1,(i.a-1)*block_size+1,block_size-2,block_size-2);
        }
        g.setColor(new Color(0,0,170));
        g.fillRect((food.b-1)*block_size+4,
				(food.a-1)*block_size+4,block_size-8,block_size-8);
    }
	public void change() {
		
		this.dir_real = this.dir;
		mpair nefront = new mpair(
			front.a+dir_real.a,
			front.b+dir_real.b
		);
		if(nefront.a > this.shu) nefront.a = 1;
		else if(nefront.a < 1) nefront.a = this.shu;
		if(nefront.b > this.heng) nefront.b = 1;
		else if(nefront.b < 1) nefront.b = this.heng;
		
 		this.snake_que.offer(nefront);
		this.front = nefront;
		
		if(size_change == 0) this.snake_que.poll();
		else size_change--;
	}
	public Main() {
		for(int i=1;i<=this.size_init;i++) {
			this.snake_que.offer(new mpair(1,i));
		}
		this.dir = new mpair(0,1);
		this.front = new mpair(1,this.size_init);
		this.add_food();
		
		this.addKeyListener(this);
	}
	@Override
    public void keyPressed(KeyEvent e) {
		
        mpair lin = new mpair(0,0);
        if(e.getKeyCode()==27) System.exit(0);
        if(e.getKeyCode()==38) lin = new mpair(-1,0);
        else if(e.getKeyCode()==37) lin = new mpair(0,-1);
      	else if(e.getKeyCode()==40) lin = new mpair(1,0);
        else if(e.getKeyCode()==39) lin = new mpair(0,1);
        else {
    		return;
		}
        if(this.dir_real.a == -lin.a && this.dir_real.b == -lin.b) return;
        this.dir = lin;
    }
    @Override
    public void keyReleased(KeyEvent keyEvent) { }
    @Override
    public void keyTyped(KeyEvent keyEvent) { }
}
class mpair {
	int a,b;
	public mpair(int x,int y) {
		a = x;
		b = y;
	}
}