/* S0640.java
 *        ホコリのシミュレーション 
 *         (C) H.Ishikawa 2008 
 */

package simulation;

import java.applet.*;
import java.awt.*;
import java.awt.event.*;
import window.Window;


public class S0640 extends Applet implements ActionListener {
	Button button0;
	Button button1;
	int sw =0;
	public void init() {
		button0 = new Button(" 実行 ");
		button1 = new Button("クリア");
		add(button0);
		add(button1);
		button0.addActionListener(this);
		button1.addActionListener(this);
	}
	public void actionPerformed(ActionEvent e) {
		String label = e.getActionCommand();
		if (label.equals(" 実行 ")) sw = 1; else sw = 0;
		repaint();
	}

	public void paint(Graphics g) {
		Window w ;
		w = new Window();
		int SPACE = 30;
		int HIGHT = 400;
		int WIDTH = 640;
		int PARTICLE =  1000;                       /* 粒子の数 */
		double MAX  =     50.0;
		long T_END =   10000;

		double x[] = new  double[PARTICLE];
		double y[] = new  double[PARTICLE];
		int       i;                                /* 粒子のカウンタ */
		long      t = 0;
		double    th;
		double    l;

		/*グラフィックの準備*/
		w.setWindow(0, -MAX,-MAX,MAX,MAX,  SPACE,HIGHT-SPACE,HIGHT-SPACE,SPACE);
		w.axis(0, "", MAX, "", MAX, g);
		
		/*開始*/
		if ( sw == 1) {
			for (i = 0; i < PARTICLE; i ++) {
				x[i] = MAX * (2.0 * Math.random() - 1.0);      /* 始めは一様に分布 */
				y[i] = MAX * (2.0 * Math.random() - 1.0);
				g.setColor(Color.green);
				w.putPixel(0, x[i], y[i], g);
			}
  
			/*メイン*/
			while (t < T_END) {
				for (i = 0; i < PARTICLE; i ++) {
					g.setColor(Color.white);
					w.putPixel(0, x[i], y[i], g);
					th = 2.0 * Math.PI * Math.random();
					l = (Math.sqrt(2.0) * MAX - Math.sqrt(x[i] * x[i] + y[i] * y[i])) / MAX;
					x[i] = x[i] + l * Math.cos(th);
					y[i] = y[i] + l * Math.sin(th);
					if (x[i] >=  MAX) { x[i] =  2*MAX - x[i];}   /* 反射　右の壁 */
					if (x[i] <= -MAX) { x[i] = -2*MAX - x[i];}   /* 反射  左の壁 */
					if (y[i] >=  MAX) { y[i] =  2*MAX - y[i];}   /* 反射  上の壁 */
					if (y[i] <= -MAX) { y[i] = -2*MAX - y[i];}   /* 反射  下の壁 */
					g.setColor(Color.blue);
					w.putPixel(0, x[i], y[i], g);
				}
				w.axis(0, "", MAX, "", MAX ,g);
				t = t + 1;
			}
			stop();
		}
	}
}