/*
 * mw4.java - revised 23 Apr 07 - width 481, height 241
 * @author jackord@kw.igs.net
 * wave incident (n=1) on a film (n=5/3) on a substrate (n=2-.2i)
 * the film thickness is 3/4 of the wavelength (in the film)
 */

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

public class mw4 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 jd, c, x1, y1, x2, y2;                         // Declarations
    double a, r, a1, r1, r1r, r1i, ip, rp, a2, r2;
    double ph1, ph2, ph3, ph4, phn, phd;
    double t, dt, dx, n, n2, k2, num, den;
    g.drawRect(0, 0, 480, 240); g.drawLine(0, 120, 480, 120);
    g.drawLine(240, 0, 240, 240); g.drawLine(294, 0, 294, 240);
    if (first==0) {
      bim=createImage(481, 241);                       // Animation buffer
      bgr=bim.getGraphics();
      first=1;
    }
    c=2; dx=Math.PI/20; dt=dx/c; jd=18; 
    a1=60; n=5./3.; n2=2; k2=.2;                       // Refractive indices
    rp=n2-n*n; ip=-k2;                                 // Complex arithmetic
    num=Math.sqrt(rp*rp+ip*ip);
    phn=Math.atan2(ip, rp);
    rp=n2+n*n;
    den=Math.sqrt(rp*rp+ip*ip);
    phd=Math.atan2(ip, rp);
    r1=num/den; ph1=phn-phd;
    r1r=r1*Math.cos(ph1); r1i=r1*Math.sin(ph1);
    num=Math.sqrt((1+r1r)*(1+r1r)+r1i*r1i);
    phn=Math.atan2(r1i, 1+r1r);                        //      (ugh!)
    den=Math.sqrt(n2*n2+k2*k2);
    phd=Math.atan2(-k2, n2);
    t=n*num/den;
    ph2=Math.PI/2+phn-phd;
    a2=t/2/n*Math.sqrt((n+n2)*(n+n2)+k2*k2);
    ph3=ph2+Math.atan2(-k2, n+n2);
    r2=t/2/n*Math.sqrt((n-n2)*(n-n2)+k2*k2);
    ph4=ph2+Math.atan2(k2, n-n2);
    r1=a1*r1; a2=a1*a2; r2=a1*r2; t=a1*t;              // Amplitudes (finally)
    if (kk!=0) {
      long tt=System.currentTimeMillis(); int del=15;
      for (int i=0; i<=160*c; i=i+1) {
        bgr.setColor(getBackground());                 // Clear plot buffer
        bgr.fillRect(0, 0, 481, 241);
        bgr.setColor(Color.black);
        bgr.drawRect(0, 0, 480, 240); bgr.drawLine(0, 120, 480, 120);
        bgr.drawLine(240, 0, 240, 240); bgr.drawLine(294, 0, 294, 240);
        if (kk==1) {
          bgr.setColor(Color.magenta);                 // Plot incident wave
          x1=0; y1=120-(int)(a1*Math.sin(i*dt));
          for (int j=1; j<=80; j=j+1) {                
            a=a1*Math.sin(i*dt-j*dx);
            x2=3*j; y2=120-(int)a;
            bgr.drawLine(x1, y1, x2, y2); x1=x2; y1=y2;
          }
          bgr.setColor(Color.red);                     // Plot reflected wave
          x1=0; y1=120-(int)(r1*Math.sin(i*dt+ph1));
          for (int j=1; j<=80; j=j+1) {               
            r=r1*Math.sin(i*dt+j*dx+ph1);
            x2=3*j; y2=120-(int)r;
            bgr.drawLine(x1, y1, x2, y2); x1=x2; y1=y2;
          }
          bgr.setColor(Color.orange);                  // Plot n=5/3 region
          x1=240; y1=120-(int)(a2*Math.sin(i*dt+n*jd*dx+ph3));
          for (int j=1; j<=jd; j=j+1) {              
            a=a2*Math.sin(i*dt-n*(j-jd)*dx+ph3);
            x2=240+3*j; y2=120-(int)a;
            bgr.drawLine(x1, y1, x2, y2); x1=x2; y1=y2;
          }
          bgr.setColor(Color.green);
          x1=240; y1=120-(int)(r2*Math.sin(i*dt-n*jd*dx+ph4));
          for (int j=1; j<=jd; j=j+1) {                
            r=r2*Math.sin(i*dt+n*(j-jd)*dx+ph4);
            x2=240+3*j; y2=120-(int)r;
            bgr.drawLine(x1, y1, x2, y2); x1=x2; y1=y2;
          }
        }
        if (kk==2) {                                   // Plot resultant wave
          bgr.setColor(Color.blue);
          x1=0; y1=120-(int)(a1*Math.sin(i*dt)+r1*Math.sin(i*dt+ph1));
          for (int j=1; j<=80; j=j+1) {                
            a=a1*Math.sin(i*dt-j*dx);
            r=r1*Math.sin(i*dt+j*dx+ph1);
            x2=3*j; y2=120-(int)(a+r);
            bgr.drawLine(x1, y1, x2, y2); x1=x2; y1=y2;
          }
          for (int j=1; j<=jd; j=j+1) {                // Plot n=5/3 region
            a=a2*Math.sin(i*dt-n*(j-jd)*dx+ph3);
            r=r2*Math.sin(i*dt+n*(j-jd)*dx+ph4);
            x2=240+3*j; y2=120-(int)(a+r);
            bgr.drawLine(x1, y1, x2, y2); x1=x2; y1=y2;
          }
        }
        bgr.setColor(Color.blue);                      // Plot transmitted wave
        x1=294; y1=120-(int)(t*Math.sin(i*dt+ph2));
        for (int j=jd+1; j<=80; j=j+1) {                  
          x2=240+3*j; y2=120-(int)(t*Math.exp(-k2*(j-jd)*dx)*Math.sin(i*dt-n2*(j-jd)*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();
  }
}