import java.awt.Canvas;
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.Color;

import java.awt.event.KeyListener;
import java.awt.event.KeyEvent;

import java.util.ArrayList;

import java.awt.image.BufferedImage;

public class Snake extends Canvas 
	implements Runnable, KeyListener {

	boolean playing;
	boolean updated;
	int state;
	int dx, dy;
	int dx2, dy2;
	int bitCount;
	final int height = 500;
	final int width = 500;
	long sleep;

	Frame frame;
	BufferedImage off;
	Graphics canvas;
	Coord head;
	Coord food;
	static Thread game;
	ArrayList<Coord> bits;

	public static void main(String args[]) {
		Snake snake = new Snake();
		game = new Thread(snake);
		game.start();
	}

	public Snake() {
		sleep = 100;
		playing = true;
		off = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
		canvas = off.getGraphics();
		frame = new Frame("Snake - RLN");
		frame.add(this);
		addKeyListener(this);
		frame.addKeyListener(this);
		frame.setSize(506, 532);
		frame.setResizable(false);
		frame.setVisible(true);
		state = 0;
	}

	public void run() {
		try {
			while(true) {
				process();
				Thread.sleep(sleep);
			}
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	public void paint(Graphics g) {
		g.drawImage(off, 0, 0, width, height, this);
	}

	public void process() {
		switch(state) {
			case 0: // init
				bitCount = 0;
				updated = false;
				bits = new ArrayList<Coord>(20);
				head = new Coord(100, 100);
				food = new Coord((int)(Math.random() * 50) * 10, (int)(Math.random() * 50) * 10);
				bits.add(head);
				++bitCount;
				dx = 1;
				dy = 0;
				dx2 = 1;
				dy2 = 0;
				state = 1;
			break;
			case 1: // game loop
				if(head.equals(food)) {
					Coord coord = new Coord(0, 0);
					bits.add(coord);
					++bitCount;
					food.x = (int)(Math.random() * 50) * 10;
					food.y = (int)(Math.random() * 50) * 10;
					if((bitCount - 1) % 2 == 0 && sleep > 5)
						sleep -= 5;
				}
				canvas.setColor(Color.GREEN);
				canvas.fillRect(0, 0, height, width);
				canvas.setColor(Color.WHITE);
				for(int i = bitCount - 1; i >= 0; --i) {
					if(i == 0)
						bits.get(i).translate(head.x + dx * 10, head.y + dy * 10);
					else
						bits.get(i).translate(bits.get(i - 1).x, bits.get(i - 1).y);
					canvas.fillRect(bits.get(i).x, bits.get(i).y, 10, 10);
				}
				canvas.setColor(Color.RED);
				canvas.fillRect(food.x, food.y, 10, 10);
				updated = false;
				if(head.x < 0 || head.x > width || head.y < 0 || head.y > height) {
					state = 2;
					playing = false;
					sleep = 100;
					break;
				}
				for(int i = 1; i < bitCount; ++i) {
					if(bits.get(i).equals(head)) {
						state = 2;
						playing = false;
						sleep = 100;
						break;
					}
				}
				paint(getGraphics());
			break;
			case 2: // game over
				canvas.setColor(Color.GREEN);
				canvas.fillRect(0, 0, width, height);
				canvas.setColor(Color.BLUE);
				canvas.drawString("Game over!", 180, 250);
				canvas.drawString("Score: " + (bitCount - 1) * 10, 180, 260);
				canvas.drawString("Press <Enter> to play again", 180, 270);
				paint(getGraphics());
			break;
			default: break;
		}
	}

	public void keyReleased(KeyEvent e) {
	}

	public void keyPressed(KeyEvent e) {
		int k = e.getKeyCode();
		if(!updated) {
			if(k == e.VK_UP) {
				if(dy == 1 && bitCount > 1)
					return;
				dy = -1;
				dx = 0;
				updated = true;
			} else
			if(k == e.VK_DOWN) {
				if(dy == -1 && bitCount > 1)
					return;
				dy = 1;
				dx = 0;
				updated = true;
			} else
			if(k == e.VK_LEFT) {
				if(dx == 1 && bitCount > 1)
					return;
				dx = -1;
				dy = 0;
				updated = true;
			} else
			if(k == e.VK_RIGHT) {
				if(dx == -1 && bitCount > 1)
					return;
				dx = 1;
				dy = 0;
				updated = true;
			}
		}
		if(k == e.VK_ENTER && !playing) {
			state = 0;
			playing = true;
		}
	}

	public void keyTyped(KeyEvent e) {
	}
}

class Coord {

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

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

	public boolean equals(Coord c) {
		return c.x == x && c.y == y;
	}
}