/*
 * mw2.java - revised 22 Apr 07 - width 481, height 241
 * @author jackord@kw.igs.net
 * wave striking an absorbing medium, n(left)=1 and n(right)=2-.2i
 */

import java.applet.Applet;
import java.awt.*;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;

public class mw2 extends Applet
                 implements ActionListener, Runnable {
  int kk=0; int first=0;                               // Declarations
  String b1s="Component"; Button b1=new Button(b1s);
  String b2s="Resultant"; Button b2=new Button(b2s);
  Image bim;
  Graphics bgr;
  Thread tmr;

  public void init() {
    setLayout(new FlowLayout(FlowLayout.LEFT));
    setBackground(new Color(211, 211, 211));
    add(b1); add(b2);
    b1.addActionListener(this);
    b2.addActionListener(this);
  }

  public void start() {
    if (kk>0) {
      if (tmr==null) {
        tmr=new Thread(this);
      }
      tmr.start();
    }
  }

  public void stop() {
    tmr=null;
  }

  public void run() {
    Thread.currentThread().setPriority(Thread.MIN_PRIORITY);
    repaint();
  }

  public void paint(Graphics g) {
    int c, x1, y1, x2, y2;                             // Declarations
    double n, k, ph1, ph2, dt, dx, a, r, t;
    g.drawRect(0, 0, 480, 240);
    g.drawLine(0, 120, 480, 120); g.drawLine(240, 0, 240, 240);
    if (first==0) {
      bim=createImage(481, 241);                       // Animation buffer
      bgr=bim.getGraphics();
      first=1;
    }
    c=2; dx=Math.PI/20; dt=dx/c; a=60; n=2.; k=.2;
    r=a*Math.sqrt((1-n)*(1-n)+k*k)/Math.sqrt((1+n)*(1+n)+k*k);
    ph1=Math.atan2(2*k, 1-n*n-k*k);
    t=2*a/Math.sqrt((1+n)*(1+n)+k*k);
    ph2=Math.atan2(k, 1+n);
    long tt=System.currentTimeMillis(); int del=15;
    if (kk!=0) {
      for (int i=0; i<=160*c; i=i+1) {
        bgr.setColor(getBackground());                 // Clear plot buffer
        bgr.fillRect(0, 0, 480, 240);
        bgr.setColor(Color.black);
        bgr.drawRect(0, 0, 480, 240);
        bgr.drawLine(0, 120, 480, 120); bgr.drawLine( 240, 0, 240, 240);
        if (kk==1) {
          bgr.setColor(Color.magenta);                 // Plot incident wave
          x1=0; y1=120-(int)(a*Math.sin(i*dt));
          for (int j=1; j<=80; j=j+1) {               
            x2=3*j; y2=120-(int)(a*Math.sin(i*dt-j*dx));
            bgr.drawLine(x1, y1, x2, y2); x1=x2; y1=y2;
          }
          bgr.setColor(Color.red);                     // Plot reflected wave
          x1=0; y1=120-(int)(r*Math.sin(i*dt-80*dx+ph1));
          for (int j=1; j<=80; j=j+1) {               
            x2=3*j; y2=120-(int)(r*Math.sin(i*dt+j*dx+ph1));
            bgr.drawLine(x1, y1, x2, y2); x1=x2; y1=y2;
          }
        }
        if (kk==2) {
          bgr.setColor(Color.blue);                    // Plot resultant
          x1=0; y1=120-(int)(a*Math.sin(i*dt)+r*Math.sin(i*dt+ph1));
          for (int j=1; j<=80; j=j+1) {               
            x2=3*j; y2=120-(int)(a*Math.sin(i*dt-j*dx)+r*Math.sin(i*dt+j*dx+ph1));
            bgr.drawLine(x1, y1, x2, y2); x1=x2; y1=y2;
          }
        }  
        bgr.setColor(Color.blue);                      // Plot transmitted wave
        x1=240; y1=120-(int)(t*Math.sin(i*dt+ph2));
        for (int j=1; j<=80; j=j+1) {                  
          x2=240+3*j; y2=120-(int)(t*Math.exp(-j*k*dx)*Math.sin(i*dt-j*n*dx+ph2));
          bgr.drawLine(x1, y1, x2, y2); x1=x2; y1=y2;
        }
        g.drawImage(bim, 0, 0, null);                  // Show plot buffer
        while ((System.currentTimeMillis()-tt)<30*i) {
          try {
            Thread.sleep(del);
          }
          catch (InterruptedException e) {
            stop();
          }
        }
      }
    }
    kk=0; stop();
  } 

  public void actionPerformed(ActionEvent e) {
    String tst;
    tst=e.getActionCommand();
    if (b1s.equals(tst)) { kk=1; }
    if (b2s.equals(tst)) { kk=2; }
    start();
  }
}