import java.awt.*;
import java.applet.*;
import java.awt.image.*;

public class Asym extends Applet implements Runnable {
  Thread runstring;

  public Scrollbar leftRight;
  private MyCanvas canv;
  private MyPanel thePanel;
  BorderLayout MyLay;
  int Flag;
  public boolean stopped=false;

  public Asym() //to initialize Flag
  {
     setFlag(0);
  }
  public void setFlag(int fl)
  {
     Flag=fl;    //Flag 0 do not begin string motion, 1 yes
   }
  public void init()
  {
    setLayout(MyLay=new BorderLayout());
    thePanel=new MyPanel(this,canv);
    leftRight=new Scrollbar(Scrollbar.HORIZONTAL,80,0,40,110);
    canv=new MyCanvas(this);
    canv.init();
    thePanel.init();
    add("Center",canv);
    add("North",leftRight);
    add("South", thePanel);
  }
  public void start()
  {
    if(! stopped)
    {
    if(Flag==1){
       canv.jj=1;
       canv.flag=1;
       runstring=new Thread(this);
       runstring.start();
     }
    }
  }
  public void stop()
  {
     if(runstring != null){
        runstring.suspend();
        runstring=null;
     }
  }

  public void brk()
  {   //stops motion temporarily
      runstring.stop();
      stopped=false;
      setFlag(0);
      canv.jj=1;
  }

  public void run()
  {
    while(true){
     
      try{
        Thread.currentThread().sleep(350);}
      catch
          (InterruptedException e){ }
            canv.repaint();
    }
  }


   public void paint(Graphics g){
    canv.repaint();    //called many times
   }

   public boolean handleEvent(Event ev){
   //events sent by Mypanel and scrollbar interpreted here
   if(ev.target instanceof Scrollbar){
     if(ev.target==leftRight)canv.setWidth(leftRight.getValue());
     canv.repaint();
     return true;
    }
    return false;
   }
}   //class

class MyCanvas extends Canvas implements ImageObserver{
   //all the painting occurs here
   Asym runstring;
   double mxx,bxx,myy,byy,xxpos;
   private Image offScreenImage;
   Graphics offScreenGraphics;
   int ypos,xpos;
   int first,incr,jj=1;
   double  psr[][], psi[][], v[], p2[];
   int flag=0; //do not draw equation

   public void init()
   {
     psr=new double[401][2];
     psi=new double[401][2];
     p2=new double[401];
     v=new double[401];
     jj=1;
 }

   public MyCanvas(Asym runstring) //to initialize class and variables
   {
     this.runstring=runstring;
     setWidth(50);  //initial position of the horizontal
//     setHeight(20); //position
   }
 public void update(Graphics g)
  { //To avoid screen flicker use double buffer technique
    offScreenImage=createImage(size().width,size().height);
    offScreenGraphics=offScreenImage.getGraphics();
    offScreenGraphics.setColor(getBackground());
    offScreenGraphics.fillRect(0,0,size().width,size().height);
    offScreenGraphics.setColor(g.getColor());
    paint(offScreenGraphics);
    g.drawImage(offScreenImage,0,0,this);
  }
/*   public void setHeight(int h)
   {
     ypos=h;  //initial vertical
   }*/
   public void setWidth(int hx)
   {
     xpos=hx;
   }
   void coormundo(double xiz,double ysu,double xde,double yinf)
  { //to convert world to screen coordinates. Gives mxx bxx for
    //x_screen=mxx*x_world +byy same for y.
    double maxx,maxy,xxfin,xxcom,yyin,yysu;
    maxx=350;
    maxy=280;
    xxcom=0.05*maxx;
    xxfin=0.8*maxx;
    yyin=0.98*maxy;
    yysu=0.2*maxy;
    mxx=(xxfin-xxcom)/(xde-xiz);
    bxx=0.5*(xxcom+xxfin-mxx*(xiz+xde));
    myy=(yyin-yysu)/(yinf-ysu);
    byy=0.5*(yysu+yyin-myy*(yinf+ysu));
  }

 public void Equation(Graphics g)
 {
   int peo,peye,pex,peyo,peyv0,peyv1;
   double dt,x,fact2,fact22;
   double pi,dx,k0,vh;
   double expon,expon2;
   int i,n,max,arrow;
   pi=3.14159265358979323846;
   max=400;
   xxpos=(double)xpos;
   dx=0.02;
   dt=0.9*dx*dx;
   x=0.0;
   g.drawString("Momentum",60,10);
  // g.drawString("M.J. Paez",250,200);
   g.setColor(Color.red);
   g.drawRect(5,10,340,190);
   g.setColor(Color.blue);
   if(jj==1){
     // initial conditions
     coormundo(0.0,1.5,max+1,-1.5);
     incr=10;
     xxpos=(double)xpos;
     k0=pi*xxpos/7.0;
     arrow=(int)(2.0*xxpos/5.0)+50;
     g.setColor(Color.yellow);
     g.drawLine(130,85,130+arrow,85);//arrow
     g.drawLine(130+arrow-5,80,130+arrow,85); //upper tip
     g.drawLine(130+arrow-5,90,130+arrow,85); //lower tip
     g.setColor(Color.blue);
     for(i=0;i<max+1;i++){
       //real part of the initial wave function at t=0
       fact2=2.0*(x-3.3);
       fact22=2.0*(x-4.7);
       expon=Math.exp(-fact2*fact2);
       expon2=Math.exp(-fact22*fact22);
       psr[i][0] = Math.cos(k0*x)*(expon+0.7*expon2);
       //imaginary part of the initial wave function at t=0
       psi[i][0] = Math.sin(k0*x)*(expon+0.7*expon2);
       x=x+dx;
     }
   }//if jj
   // solution for new times
   for( n=first-1;n<jj+1;n++){
     //real part of wavefunction and probability
     for( i=1;i<max;i++){
       psr[i][1]=psr[i][0] - dt*(psi[i+1][0] + psi[i-1][0]
                -2.0*psi[i][0])/(2.0*dx*dx);
       p2[i]=psr[i][0]*psr[i][1]+psi[i][0]*psi[i][0];
     }
     //imaginary part of the wave function
     for(i=1;i<max;i++){
       psi[i][1] = psi[i][0]+dt*(psr[i+1][1] + psr[i-1][1]
                     -2.0*psr[i][1])/(2.0*dx*dx);
     }
      if(jj==1)byy=byy-25;
     // the probability plotted at times=incr
     if(n==jj){
       for(i=1;i<max+1;i++){
         if(i>0){
            peo=(int)(mxx*(i-1)+bxx);
            peyo=(int)(myy*p2[i-1]+byy);
            pex=(int)(mxx*i+bxx);
            peye=(int)(myy*p2[i]+byy);
            g.drawLine(peo,peyo,pex,peye);
          }
       }
     }
     // new iterations are now the old ones
     for(i=1;i<max+1;i++){
       psi[i][0]=psi[i][1];
       psr[i][0]=psr[i][1];
     }
   }
 }


  public void paint(Graphics g){
     first=jj;
     if(jj==1)Equation(g);
     if((runstring.Flag==1)&&(flag==1)){
       if(first==incr+1)first=1;
       if(first>=incr+1)first=jj-incr;
       Equation(g);
       jj=jj+incr;
     }
   }
 }

 class MyPanel extends Panel{
  //controls Stop, start and scrollbars
  //transmits to Eqstring the events
  Asym runstring;
  GridBagLayout GBLay;
  GridBagConstraints c;
  MyCanvas canv;

  public void init(){
    GBLay=new GridBagLayout();
    c=new GridBagConstraints();
    setLayout(GBLay);
    c.gridx=1;
    c.gridy=1;
    c.gridheight=1;
    c.fill=GridBagConstraints.BOTH;
   /* Button sta=new Button("Cont");
    GBLay.setConstraints(sta,c);
    add(sta);*/
    //  c.gridx=2;
    Button stp=new Button("Stop");
    GBLay.setConstraints(stp,c);
    add(stp);
    c.gridx=2;
    Button rest=new Button("Start");
    GBLay.setConstraints(rest,c);
    add(rest);
  }
  public MyPanel(Asym runstring, MyCanvas canv)
  {
    this.canv=canv;
    this.runstring=runstring;
  }

 public boolean action(Event ev, Object arg)
 {
   if (ev.target  instanceof Button) {
     String label=(String)ev.arg;
     if (label.equals("Stop")){
       runstring.brk();
     }
     if(label.equals("Start")){
       runstring.setFlag(1);
       runstring.stopped=false;
       runstring.start();
       canv.flag=1;
     }
     return true;
   }
   else
    if(ev.target instanceof Scrollbar){
      runstring.postEvent(ev);//sent to Eqstring handlEvent
      return true;
    }
    return false;
  }
}