/*
 * WindTree.java
 *
 * Copyright (C) 1998 by Hiroshi Yuki.
 * All rights reserved.
 * <hyuki@hyuki.com>
 * http://www.hyuki.com/jb/
 */

import java.awt.*;
import java.applet.Applet;

public class WindTree extends Applet {
    Graphics offgra = null;
    Image offimg = null;
    double CENTERX = 200.0;
    double CENTERY = 380.0;
    double basex = 0.0;
    double basey = 0.0;
    double basedir = -Math.PI/2.0;
    double distance = 1.0;

    public void init() {
        resize(400, 400);
    }
    public void start() {
        if (offgra == null) {
           offimg = createImage(400, 400);
           offgra = offimg.getGraphics();
        }
    }
    public boolean mouseMove(Event e, int x, int y) {
        if (y - CENTERY < 0) {
            Graphics g = getGraphics();
            basex = x - CENTERX;
            basey = y - CENTERY;
            basedir = getDirection(x, y) + Math.PI/2.0;
            distance = Math.sqrt(basex * basex + basey * basey) / Math.sqrt(200*200 + 200*200);
            if (distance > 0) {
                update(g);
            }
        }
        return true;
    }
    public void update(Graphics g) {
        if (offgra != null) {
            offgra.setColor(new Color(198, 236, 244));
            offgra.fillRect(0, 0, 400, 400);
            offgra.setColor(Color.black);
            paint(offgra);
            g.drawImage(offimg, 0, 0, this); 
        }
    }
    public void paint(Graphics g) {
        FontMetrics fm = g.getFontMetrics();
        g.setColor(Color.black);
        g.drawString("This is WindTree by Hiroshi Yuki.", 0, fm.getHeight());
        g.drawString("http://www.hyuki.com", 0, fm.getHeight()*2);
        drawtree(g, 0.0, 0.0, -Math.PI/2, 50.0);
    }
    public void drawtree(Graphics g, double x, double y, double dir, double size) {
        // stem
        if (size > 4.0) {
            double nextx = x + (double)Math.cos(dir) * size;
            double nexty = y + (double)Math.sin(dir) * size;
            g.setColor(getColorBySize(size));
            g.drawLine((int)(CENTERX + x), (int)(CENTERY + y), (int)(CENTERX + nextx), (int)(CENTERY + nexty));
            // right
            drawtree(g, nextx, nexty, dir + 0.2/distance + basedir, size / 1.4);
            // left
            drawtree(g, nextx, nexty, dir - 0.2/distance + basedir, size / 1.4);
        }
    }
    public double getDirection(int x, int y) {
        if (x - CENTERX >= 0) {
            return Math.atan((double)(y - CENTERY) / (double)(x - CENTERX));
        } else {
            return Math.atan((double)(CENTERX - x) / (double)(y - CENTERY)) - Math.PI/2.0;
        }
    }
    Color getColorBySize(double size) {
        if (size / 1.4 <= 4.0) {
            return new Color(245, 129, 208);
        } else if (size > 20) {
            return new Color(125, 68, 0);
        } else if (size < 10) {
            return new Color(10,239,0);
        } else {
            return new Color(98, 108, 0);
        }
    }
}