package snake;

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.util.*;

public class Game {
    @SuppressWarnings("deprecation")
    public static void main(String args[]) {
        GameFrame frame = new GameFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setResizable(false);
        frame.show();
        JOptionPane.showMessageDialog(null, "上,下左,右控制蛇的方向\n回车开始,S暂停");
    }
}

@SuppressWarnings("serial")
class GameFrame extends JFrame {
    public GameFrame() {
        setSize(294, 482);
        setTitle("贪吃蛇DEMO");
        this.setLocation(360, 100);
        Container c = getContentPane();
        GamePanel panel = new GamePanel();
        c.add(panel, BorderLayout.CENTER);
    }
}

@SuppressWarnings("serial")
class GamePanel extends JPanel implements KeyListener {
    static int panelWidth = 294;

    static int panelHeight = 450;

    int rectX = 15;

    int rectY = 15;

    Snake snake;

    Node n;

    public GamePanel() {
        snake = new Snake(this, panelWidth / rectX, panelHeight / rectY);
        setBackground(Color.WHITE);
        setSize(panelWidth, panelHeight);
        setFocusable(true);
        addKeyListener(this);
    }

    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D) g;
        LinkedList list = snake.snakeList;
        Iterator it = list.iterator();
        g2.setColor(Color.black);
        while (it.hasNext()) {
            n = (Node) it.next();
            drawNode(g2, n);
        }
        g2.setColor(Color.ORANGE);
        Node f = snake.food;
        drawNode(g2, f);
        snake.drawMap(g2);// 绘制地图
    }

    public void keyPressed(KeyEvent e) {
        int keycode = e.getKeyCode();
        if (keycode == KeyEvent.VK_ENTER) {
            begin();
        } else if (keycode == KeyEvent.VK_UP) {
            snake.changeDirection(Snake.up);
        } else if (keycode == KeyEvent.VK_DOWN) {
            snake.changeDirection(Snake.down);
        } else if (keycode == KeyEvent.VK_LEFT) {
            snake.changeDirection(Snake.left);
        } else if (keycode == KeyEvent.VK_RIGHT) {
            snake.changeDirection(Snake.right);
        } else if (keycode == KeyEvent.VK_S) {
            Snake.run = false;
        }
    }

    public void keyReleased(KeyEvent e) {
    }

    public void keyTyped(KeyEvent e) {
    }

    public void drawNode(Graphics2D g, Node n) {
        g.fillRect(n.x * rectX, n.y * rectY, rectX - 2, rectY - 2);
    }

    public void begin() {
        Snake.run = true;
        SnakeThread thread = new SnakeThread(snake);
        thread.start();
    }
}

class Node {
    int x;

    int y;

    public Node(int x, int y) {
        this.x = x;
        this.y = y;
    }
}

class SnakeThread extends Thread {
    Snake snake;

    public SnakeThread(Snake s) {
        snake = s;
    }

    public void run() {
        Snake.run = true;

        while (Snake.run) {
            try {
                snake.move();
                sleep(200);
            } catch (InterruptedException e) {
            }
        }
        Snake.run = false;
    }
}

class Snake {
    GamePanel panel;

    Node food;

    boolean[][] all;

    public static boolean run;

    int maxX;

    int maxY;

    public static int left = 1;

    public static int up = 2;

    public static int right = 3;

    public static int down = 4;

    int direction = 4;

    LinkedList snakeList = new LinkedList();

    public Snake(GamePanel p, int maxX, int maxY) {
        panel = p;
        this.maxX = maxX;
        this.maxY = maxY;
        all = new boolean[maxX][maxY];
        for (int i = 0; i < maxX; i++) {
            for (int j = 0; j < maxY; j++) {
                all[i][j] = false;
            }
        }
        int arrayLength = maxX > 20 ? 10 : maxX / 2;
        for (int i = 0; i < arrayLength; i++) {
            int x = maxX / 10 + i;
            int y = maxY / 10;
            snakeList.addFirst(new Node(x, y));
            all[x][y] = true;
        }
        food = createFood();
        all[food.x][food.y] = true;
    }

    // 蛇移动的方法
    public void move() {
        Node n = (Node) snakeList.getFirst();
        int x = n.x;
        int y = n.y;

        if (direction == 3) {
            x++;
        } else if (direction == 4) {
            y++;
        } else if (direction == 1) {
            x--;
        } else if (direction == 2) {
            y--;
        }
        // 实现对蛇撞到自身的检测
        if ((0 <= x && x <= GamePanel.panelWidth / 15 - 1)
                && (0 <= y && y <= GamePanel.panelHeight / 15 - 1)) {
            if (all[x][y]) {
                if (x == food.x && y == food.y) {
                    snakeList.addFirst(food);
                    food = createFood();
                    all[food.x][food.y] = true;
                } else {
                    JOptionPane.showMessageDialog(null, "你撞到自己了");
                    System.exit(0);
                }
            } else {
                snakeList.addFirst(new Node(x, y));
                all[x][y] = true;
                Node l = (Node) snakeList.getLast();
                snakeList.removeLast();
                all[l.x][l.y] = false;
            }
        } else {
            JOptionPane.showMessageDialog(null, "越界了,游戏结束");
            System.exit(0);
        }
        panel.repaint();
    }

    public Node createFood() {
        int x = 0;
        int y = 0;
        do {
            Random r = new Random();
            x = r.nextInt(maxX - 10);
            y = r.nextInt(maxY - 10);

        } while (all[x][y]);
        return new Node(x, y);
    }

    // 设置蛇不能回头
    public void changeDirection(int newDirection) {
        if (direction % 2 != newDirection % 2) {
            direction = newDirection;
        }
    }

    public void drawMap(Graphics2D g) {
        for (int i = 0; i < maxX; i++) {
            for (int j = 0; j < maxY; j++) {
                if (all[i][j] == true) {
                    g.setColor(Color.red);
                    g.fillRect(i, j, 4, 4);
                }
            }
        }
    }
}