/*
 * qm2.java - revised 27 Dec 07 - width 321, height 221
 * @author jackord@kw.igs.net
 * wave pulse on a quantum string
 * time dependence calculated either directly from the Schrodinger Equation
 *   or from FFSS expansion
 */

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

public class qm2 extends Applet
                 implements ActionListener {
  int kk=0; int plt=0; int first=0;                    // Declarations
  String b1s="P Dens"; Button b1=new Button(b1s);
  String b2s="R Comp"; Button b2=new Button(b2s);
  String b3s="Motion"; Button b3=new Button(b3s);
  Checkbox ch1=new Checkbox("FFSS");
  Image bim;
  Graphics bgr;

  public void init() {
    setLayout(new FlowLayout(FlowLayout.LEFT));
    setBackground(new Color(211, 211, 211));
    ch1.setBackground(getBackground());
    add(b1); b1.addActionListener(this);
    add(b2); b2.addActionListener(this);
    add(b3); b3.addActionListener(this);
    add(ch1);
  }

  public void paint(Graphics g) {
    int n, nf, nk, c, jt, del, delt;
    n=320; nf=320; c=30; nk=4;                         // Loop constants
    double [] yr=new double[n+1];
    double [] yrr=new double[n+1];
    double [] dyr=new double[n+1];
    double [] yi=new double[n+1];
    double [] yii=new double[n+1];
    double [] dyi=new double[n+1];
    double [] b=new double[n+1];
    double [] d=new double[n+1];
    double [] w=new double[n+1];
    int [] xx=new int[n+1];
    int [] yy=new int[n+1];
    double dt, pi, phi, sn;
    pi=Math.PI; dt=n*n/4/pi/c/nf/nk/nk;                // d(t/T1) * constants
    g.drawRect(0, 0, 320, 220);
    if (first==0) {
      bim=createImage(321, 221);                       // Animation buffer
      bgr=bim.getGraphics();
      first=1;
    }
    for (int i=0; i<=n; i=i+1) {
      xx[i]=i;
    }
    for (int i=3*n/8; i<=5*n/8; i=i+1) {               // Initial wave fcn
      phi=2*pi*(i-3*n/8)/(n/4); yr[i]=(1-Math.cos(phi))/2;
      yi[i]=-yr[i]*Math.sin(phi*nk); yr[i]=yr[i]*Math.cos(phi*nk);
    }
    if (ch1.getState()==true) {                        // FFSS
      for (int i=1; i<=n-1; i=i+1) {
        for (int j=1; j<=n-1; j=j+1) {
          sn=Math.sin(pi*i*j/n);
          b[i]=b[i]+yr[j]*2/n*sn; d[i]=d[i]+yi[j]*2/n*sn;
        }
        w[i]=i*i*2*pi/8/nf/16;
      }
    }
    else {
      for (int i=1; i<=n-1; i=i+1) {                   // Initialize dy step    
        dyr[i]=dt*(yi[i-1]+yi[i+1]-2*yi[i]);
        dyi[i]=-dt*(yr[i-1]+yr[i+1]-2*yr[i]);
      }
    }
    if (kk>0) {
      jt=0; long tt=System.currentTimeMillis(); del=25;
      do {                                             // Frame loop
        for (int i=0; i<=n; i=i+1) {
          if (kk==1) {                                 // Plot prob dens...
            yy[i]=220-(int)(160*(yr[i]*yr[i]+yi[i]*yi[i])+.5);
          }
          else {                                       // ...or real comp
            yy[i]=120-(int)(80*yr[i]+.5);
          }
        }
        bgr.setColor(getBackground());                 // Set up plot buffer
        bgr.fillRect(0, 0, 320, 220);
        bgr.setColor(Color.blue);
        if (kk==1) {
          bgr.fillPolygon(xx, yy, n+1);                // Draw filled polygon
        }
        else {
          bgr.drawPolyline(xx, yy, n+1);               // Draw polyline
        }
        bgr.setColor(Color.black);
        bgr.drawRect(0, 0, 320, 220);
        bgr.drawString("Frm "+jt+"/"+nf, 245, 20);
        g.drawImage(bim, 0, 0, null);                  // Show plot buffer
        jt=jt+1;
        if (ch1.getState()==true) {                    // FFSS
          for (int i=0; i<=n; i=i+1) {
            yr[i]=0; yi[i]=0;
            for (int k=1; k<=n-1; k=k+2) {
              sn=Math.sin(pi*i*k/n);
              yr[i]=yr[i]+sn*b[k]*Math.cos(w[k]*jt);
              yi[i]=yi[i]+sn*b[k]*Math.sin(w[k]*jt);
            }
            for (int k=2; k<=n-2; k=k+2) {
              sn=Math.sin(pi*i*k/n);
              yr[i]=yr[i]-sn*d[k]*Math.sin(w[k]*jt);
              yi[i]=yi[i]+sn*d[k]*Math.cos(w[k]*jt);
            }
          }
        }
        else {                                         // Schrodinger eqn
          for (int jj=1; jj<=c; jj=jj+1) {             // Accuracy loop
            for (int i=1; i<=n-1; i=i+1) {             // Project ahead dy/2
              yrr[i]=yr[i]+dyr[i]/2; yii[i]=yi[i]+dyi[i]/2;
            }
            for (int i=1; i<=n-1; i=i+1) {             
              dyr[i]=dt*(yii[i-1]+yii[i+1]-2*yii[i]);
              dyi[i]=-dt*(yrr[i-1]+yrr[i+1]-2*yrr[i]);
              yr[i]=yr[i]+dyr[i];
              yi[i]=yi[i]+dyi[i];
            }
          }
        }
        while (tt>System.currentTimeMillis()) { }
        tt=tt+del; if (jt==nf+1) { kk=0; plt=0; }
      } while (plt==1);
    }
  } 

  public void actionPerformed(ActionEvent e) {         // Buttons
    String tst;
    tst=e.getActionCommand();
    if (b1s.equals(tst)) { kk=1; }                     // Prob dens
    if (b2s.equals(tst)) { kk=2; }                     // Real comp
    if (b3s.equals(tst)) { if (kk>0) { plt=1; } }      // Motion
    repaint();
  }
}