/*
   Copyright F. P. Marin ( August 11 20:38:23 1997 )
   E-mail: felix@bloch.ciens.ucv.ve
   
   Permission to use, copy, modify and distribute this software and its
   documentation for NON-COMERCIAL purposes and without fee is hereby
   granted provided that this copyright notice appears in all copies.

   F. P. Marin makes no representations or warranties about the suitability
   of the software, either express or implied, including but no limited to
   the implied warranties of merchantability, fitness for a particular
   purpose, or non-infringement. F. P. Marin shall not be liable for any
   damage suffered by license as a result of using, modifying or
   distributing this software or its derivatives.
 
   HTML code is

   <applet archive="ArnoldCat.jar"
              code="ArnoldCat.class"
            height=400
             width=400>
   <param name="delay" value="42">
   </applet>
*/
import java.applet.Applet;
import java.awt.*;


public class ArnoldCat extends Applet
{
       final static double TWOPI=2.0*Math.PI;
       final int NPOINTS=3000;
       final String GENSTR="Generation ";
       double ax,bx,ay,by,x[]=new double[NPOINTS],y[]=new double[NPOINTS];
       Font f=new Font("Helvetica",Font.BOLD + Font.ITALIC,20);
       FontMetrics fm=getFontMetrics(f);
       Graphics gr;
       Image img;
       int genstrwidth=fm.stringWidth(GENSTR),gen=0,ygen;
       

       public void init()
       {
        ax=0.4*size().width;
        bx=0.5*size().width + 0.5;
        ay=-0.4*size().height;
        by=0.5*size().height + 0.5;
        ygen=size().height - 5;
        img=createImage(size().width,size().height);
        gr=img.getGraphics();
        gr.setFont(f);
        pattern0();
        setFont(new Font("TimesRoman",Font.BOLD,18));
        setBackground(Color.red.brighter());
        setForeground(Color.yellow.brighter());
        add(new Button("Original Generation"));
       }


       public void update(Graphics g)
       {
        paint(g);
       }


       public void paint(Graphics g)
       {
        gr.setColor(Color.black);
        gr.fillRect(0,0,size().width,size().height);
        double temp,theta;
        int xcat,ycat;
        for ( int i=0 ; i<x.length ; ++i ) {
            temp=Math.sin(x[i]*Math.PI);            
            theta=y[i]*TWOPI;
            xcat=(int)(ax*temp*Math.cos(theta) + bx);
            ycat=(int)(ay*temp*Math.sin(theta) + by);
            if ( x[i]<0.5 ) {
                    if ( y[i]<0.25 ) gr.setColor(Color.blue.brighter());
               else if ( y[i]<0.5  ) gr.setColor(Color.cyan.brighter());
               else if ( y[i]<0.75 ) gr.setColor(Color.green.brighter());
                                else gr.setColor(Color.pink.brighter());
            } else {
                    if ( y[i]<0.25 ) gr.setColor(Color.red.brighter());
               else if ( y[i]<0.5  ) gr.setColor(Color.white.brighter());
               else if ( y[i]<0.75 ) gr.setColor(Color.orange.brighter());
                                else gr.setColor(Color.yellow.brighter());
            }
            gr.fillOval(xcat - 1,ycat - 1,2,2);
        }
        String s=GENSTR + gen;
        int xpos=(size().width - fm.stringWidth(s))/2;
        gr.setColor(Color.white.brighter());
        gr.drawString(GENSTR,xpos,ygen);
        xpos+=genstrwidth;
        gr.setColor(Color.cyan.brighter());
        gr.drawString(String.valueOf(gen++),xpos,ygen);
        g.drawImage(img,0,0,this);
       }

       
       public boolean action(Event e,Object arg)
       {
        gen=0;
        pattern0();
        repaint();
        try {
             Thread.sleep(42);
        } catch ( InterruptedException ie ) {}
        return true;
       }
       

       public boolean mouseDown(Event e,int xmd,int ymd)
       {
        nextState();
        repaint();
        try {
             Thread.sleep(42);
        } catch ( InterruptedException ie ) {}
        return true;
       }
 

       public void nextState()
       {
        double temp;

        for ( int i=0 ; i<x.length ; ++i ) {
            temp=x[i];
            x[i]+=y[i];
            x[i]-=Math.floor(x[i]);
            y[i]=temp + 2.0*y[i];
            y[i]-=Math.floor(y[i]);
        }
       }


       public void pattern0()
       {
        for ( int i=0 ; i<x.length ; ++i ) {
            do x[i]=Math.random();
            while (  ( x[i]<0.25 ) || ( x[i]>0.75 )  );
            do y[i]=Math.random();
            while (  ( 0.25<y[i] ) && ( y[i]<0.75 )  );
        }
        nextState();
       }
}