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

// here comes the Map

class Parameter {
  public int number;
  double K;
  double xb,xe,yb,ye;
  
  public Parameter() {
    K = 0.7;
    xb = 0; yb = 0;
    xe = 1;  ye = 1;
  }
}

class Map extends Parameter {
  double psi[],theta[];
  
  public Map() {
    number = 20;
    psi   = new double [number];
    theta = new double [number];

    init();
  }

  public void init() {
    double dpsi = (ye-yb)/number;
    for (int i = 0; i < number; i++) {
      psi[i] = yb + dpsi*i;
      theta[i] = 0.5;
    }
  }

  void integrate() {
    while (true) {
      singlestep(); break;
    }
  }

  void singlestep() {

    double psin, thetan;
    double twopi = 2.*Math.PI;

    for (int i = 0; i < number; i++) {
      psin   = psi[i] + K/(twopi)*Math.sin(twopi*theta[i]);
      thetan = theta[i] + psin; 
      while (thetan > xe) thetan -= (xe-xb);
      while (thetan < xb) thetan += (xe-xb);
      psi[i] = psin;
      theta[i] = thetan;
    }
  }
}

// here comes the graphics

class mapCanvas extends Container {
  int number;
  public int x[],y[];
  boolean reset_flag=true;

  public mapCanvas() {
    number = 20;
    x = new int [number];
    y = new int [number];
  }

  public synchronized void reset() {
    reset_flag=true;
  }

  public synchronized void paint(Graphics g) {
    if (reset_flag) {
      Dimension size = getSize();
      g.setColor(Color.yellow);
      g.fillRect(0,0,size.width,size.height);
      reset_flag=false;
    }
    g.setColor(Color.blue);
    for (int i = 0; i < number; i++) {
      g.drawLine(x[i],y[i],x[i],y[i]);
    }
  }
}

public class Mapping extends Applet 
  implements Runnable, AdjustmentListener, MouseListener
{
  Map map;
  Thread killme = null;

  Scrollbar perturbation;
  mapCanvas canvas;

  public synchronized void init() {
    map=new Map();

    GridBagLayout gridbag = new GridBagLayout();
    GridBagConstraints c = new GridBagConstraints();
    setLayout(gridbag);

    c.fill = GridBagConstraints.HORIZONTAL;

    c.weightx = 1;
    add(new Label("Perturbation K"));
    perturbation=new Scrollbar(Scrollbar.HORIZONTAL, 0, 1, 0, 255);
    perturbation.setValue(45);
    perturbation.addAdjustmentListener(this);
    c.gridwidth = GridBagConstraints.REMAINDER; //end row
    gridbag.setConstraints(perturbation, c);
    add(perturbation);

    canvas = new mapCanvas();
    canvas.addMouseListener(this);
    c.fill = GridBagConstraints.BOTH;
    c.weighty = 1.0;
    gridbag.setConstraints(canvas, c);
    add(canvas);
  }

  public void start() {
    if(killme == null) {
      killme = new Thread(this);
      killme.start();
    }
  }

  public void stop() {
    killme = null;
  }

  public void run() {
    while (killme != null) {
      try {
	map.integrate();
	Dimension size;
	size = canvas.getSize();
	for (int i = 0; i < map.number; i++) {
	  canvas.x[i]=(int)((map.theta[i]-map.xb)*size.width/(map.xe-map.xb));
	  canvas.y[i]=(int)((map.ye-map.psi[i])*size.height/(map.ye-map.yb));
	}
	Thread.sleep(10);
      } 
      catch (InterruptedException e){}
      repaint();
    }
    killme = null;
  }
  
  public synchronized void update(Graphics g) {
    paintAll(g);
  }
  
  public void adjustmentValueChanged(AdjustmentEvent evt) {
    if (evt.getSource() == perturbation) {
      map.init();
      map.K = (perturbation.getValue())*2./128;
      canvas.reset();
    }
  }

  public void mouseClicked(MouseEvent evt) {
    canvas.reset();
  }

  public void mousePressed(MouseEvent evt) { }
  public void mouseReleased(MouseEvent evt) { }
  public void mouseEntered(MouseEvent evt) { }
  public void mouseExited(MouseEvent evt) { }
}