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

public class Harmos2 extends Applet implements Runnable {
  Thread runstring;

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

  public Harmos2() //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);
    upDown=new Scrollbar(Scrollbar.VERTICAL,35,0,10,65);
    leftRight=new Scrollbar(Scrollbar.HORIZONTAL,50,0,10,100);
    canv=new MyCanvas(this);
    canv.init();
    thePanel.init();
    add("Center",canv);
    add("West",upDown);
    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;
//      runstring.start();
  }

  public void run()
  {
    while(true){
     
      try{
        Thread.currentThread().sleep(250);}
      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==upDown)canv.setHeight(upDown.getValue());
     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
   Harmos2 runstring;
   double mxx,bxx,myy,byy,yypos,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() //canvas
   {
    psr= new double[301][2];
    psi=new double[301][2];
    v=new double [301];
    p2=new double [301];
    jj=1;
   }
   public MyCanvas(Harmos2 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;
   }
  /*  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=250;
    xxcom=0.05*maxx;
    xxfin=0.9*maxx;
    yyin=0.95*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;
    int pvx,pvy,max,arrow;
    double pi,dx,k0;
    int i,n;
    double x;
    double dt;
    //k0: initial momentum given to the wave packet
    dx=0.02;
    dt=dx*dx/4.0;
    max=300;
    pi=3.1415926535897932385;
 //   k0=3*pi;
    xxpos=(double)xpos;
    k0=3*pi*xxpos/50.0;
    x=-3.0;
    g.drawString("Momentum Scrollbar",150,10);
    g.drawString("Potential Scrollbar",20,155);
    g.setColor(Color.red);
    g.drawRect(5,10,320,150);
    g.setColor(Color.blue);
    if(jj==1){
      coormundo(0.0,3.5,301,0.0);
      incr=20;
      max=300;
      yypos=(double)ypos;
      xxpos=(double)xpos;
      arrow=(int)(40.0*xxpos/50.0)+165;
      g.setColor(Color.yellow);
      g.drawLine(165,105,arrow,105);//arrow
      g.drawLine(arrow-5,100,arrow,105); //upper tip
      g.drawLine(arrow-5,110,arrow,105); //lower tip
      g.setColor(Color.blue);
      for(i=0;i<max+1;i++)
      {
         psr[i][0]=(Math.cos(k0*x))*Math.exp(-0.9*(x/0.5)*x/0.5);
         // imaginary part of initial wave function
         psi[i][0]=(Math.sin(k0*x))*Math.exp(-0.9*(x/0.5)*x/0.5);
         // the potential
         v[i]=(95.0-yypos)*x*x;//depends on left scroll bar(yypos)
         x=x+dx;
      }
    }
    //  propagate  through time
    for(n=first-1;n<jj+1;n++)
    {
      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])/(dx*dx)+dt*v[i]*psi[i][0];
         p2[i]=psr[i][0]*psr[i][1]+psi[i][0]*psi[i][0];
      }
      // same thing for the imaginary part of the wave packet
     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])/(dx*dx)-dt*v[i]*psr[i][1];
     }
     if( jj==1){
        byy=byy-50;
      }
     if(n==jj) //esta en jj
     {
       for(i=0;i<max+1;i++)
       {
         if(i>0){
           peo=(int)(mxx*(i-1)+bxx);
           peyo=(int)(myy*(p2[i-1]+0.0015*v[i-1])+byy);
           peyv0=(int)(myy*0.0015*v[i-1]+byy);
           pex=(int)(mxx*i+bxx);
           peye=(int)(myy*(p2[i]+0.0015*v[i])+byy);
           g.drawLine(peo,peyo,pex,peye);
           peyv1=(int)(myy*0.0015*v[i]+byy);
           g.drawLine(peo,peyv0,pex,peyv1);
         }
       }
     }
     // new iterations are now the old ones
     for(i=0;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
  Harmos2 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(Harmos2 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;
  }

}