//  Hydrogen.java  (for JDK 1.0)
//
/*************************************************************************
 *                                                                       *
 * Copyright (c) 1998         Greg W. Anderson                           *
 *                                                                       *
 * This program is free software.  You can copy, modify, or redistribute *
 * this software under the terms of the GNU General Public License       *
 * as published by the Free Software Foundation; either version 2 of the *
 * License, or (at your option) any later version, provided that both    *
 * the above copyright notice appears in all copies and that this        *
 * permission notice appear in any supporting documentation.             *
 *                                                                       *
 * This software is provided "as is" in the hope that it will be useful, *
 * but WITHOUT any expressed or implied warranty of merchantability or   *
 * fitness for any particular purpose.                                   * 
 * See the GNU General Public License for more details.                  *
 * Your milage may vary.                                                 *
 *************************************************************************/

//  Modification History
//    Date      Initials     Change
//    2/01/98    GWA         Initial release
//  Abstract:
/*
 *
 * @author Greg Anderson
 * @version 0.1, 21 Feb 1998
 */

import java.awt.Graphics;
import java.awt.*;
import java.applet.*;  
import java.lang.Math;

public class HydrogenLevels extends java.applet.Applet {

  HydrogenCanvas c;
  HydrogenControls controls;
  HydrogenLevelsBanner banner;

  Label appletName  = new Label ("The Virtual Physics Laboratory");
  Label department  = new Label ("Department of Physics and Astronomy");
  Label university = new Label ("Northwestern University");

  public void init(){
    setLayout(new BorderLayout());
    
    banner =  new HydrogenLevelsBanner (2,2);
    banner.add("Center",department);
    banner.add(appletName);
    banner.add("Center",university);
    banner.add("South", new Label ("G.Anderson"));
    add ("North",banner);

    c = new HydrogenCanvas();
    add("Center",c);
    add("South", controls = new HydrogenControls(c));
  }

  public void start(){
    controls.enable();
  }
  public void stop(){
    controls.disable();
  }
  
  public boolean handleEvent(Event e){
    if (e.id == Event.WINDOW_DESTROY){
      System.exit(0);
    }
    return false;
  }

  public String getAppletInfo(){
    return "HydrogenLevels by Greg Anderson";
  }
  
}

class HydrogenCanvas extends Canvas {

  public boolean displayLabels  = true;
  public boolean trueColor  = false;

  public boolean displayBalmer   = true;
  public boolean displayPaschen  = true;
  public boolean displayLyman    = true;
  public boolean displayBrackett = true;

  public boolean displayElectricDipole     = true; 
  public boolean displayMagneticDipole     = true; 
  public boolean displayElectricQuadrupole = true; 
  public boolean allowedTransition         = true;

  public int  displayModel = 0;

  Color darkMagenta = new Color(150,0,150);
  Color darkdarkGray = new Color(32,32,32);
  
  int leftSpace  = 30;
  int rightSpace = 10;
  int hSpace = 10;
  int topMargin = 40;
  int bottomMargin = 10;
  int plotWidth; 
  int halfWidth; 
  int plotHeight;
  int halfHeight;
  int levelSpacing;
  int Z;

  int nmax = 8;        // The number of radial orbitals displayed
  int lmax = 7;        // The number of angular momentum states displayed

  public void initSizes(){
    plotWidth = size().width - leftSpace -rightSpace;  
    halfWidth = plotWidth/2;
    plotHeight = size().height - bottomMargin;
    halfHeight = plotHeight/2;
    levelSpacing = plotWidth/(lmax+1);
    Z = 1;  // the number of protons
  }

  double Energy(int n){
    return Energy(n,0);
  }
  double Energy(int n, int j){
    double E0;
    double alpha = 1./137.;
    double En;
    double dE;   // note, this fine structure is too small to see here
    E0 = size().height - topMargin - bottomMargin; // 13.6 eV
    En =  E0*Math.pow(Z,2)/Math.pow(n,2);
    dE = En*( Math.pow(Z*alpha/n,2)*(n/(j+0.5) - 3./4.)  );
    En = En + dE;
    return En;
  }
  

  void drawLevel(Graphics g, int n, int l){ // and (n,l) level
    g.drawLine(leftSpace + l*levelSpacing + hSpace/2,
	       topMargin + (int) Energy(n),
	       leftSpace + (l+1)*levelSpacing - hSpace/2,
	       topMargin + (int) Energy(n));	
  }

  void drawLevel(Graphics g, int n){  // Bohr levels only
    g.drawLine(leftSpace + hSpace/2,
	       topMargin + (int) Energy(n),
	       leftSpace + plotWidth - hSpace/2,
	       topMargin + (int) Energy(n));	
  }

  public void displayTransition(Graphics g, 
				int ni, int li,
				int nf, int lf){
    if(trueColor){
      g.setColor(Color.gray);
      if(ni==3 && nf ==2)g.setColor(Color.red); // Balmer Red = 3->2
      if(ni==4 && nf ==2)g.setColor(Color.blue);  // Balmer blue = 4->2
      if(ni==5 && nf ==2)g.setColor(darkMagenta);  // Balmer violet = 5->2
    }
    // try to keep displayed lines from crossing
    if (lf <= li){
      g.drawLine(leftSpace - hSpace/2 - 5*ni + (li+1)*levelSpacing,
		 topMargin + (int) Energy(ni),
		 leftSpace - hSpace/2 - 5*ni + (lf+1)*levelSpacing,
		 topMargin + (int) Energy(nf));	
    }
    else{
      g.drawLine(leftSpace + hSpace/2 + 5*ni + li*levelSpacing,
		 topMargin + (int) Energy(ni),
		 leftSpace + hSpace/2 + 5*ni + lf*levelSpacing,
		 topMargin + (int) Energy(nf));	
    }
  }    
  
  public boolean IsAllowedTransition(int li, int ji,
				     int lf, int jf){
    // ED (dl = +/-1 ), (dj = 0,+/-1 , ! 0->0)
    if(displayElectricDipole){
      if ( Math.abs(li-lf)==1 && Math.abs(ji-jf)==1){
	return true;
      }
      if ( Math.abs(li-lf)==1 && Math.abs(ji-jf)==0 && jf !=0){
	return true;
      }
    }
    
    // MD (dl = 0), (dj = 0,+/- 1 !0->0)
    if(displayMagneticDipole){
    }
    
    // EQ (dl = 0,+/-2), (no l= 0->0)
    if(displayElectricQuadrupole){} 
    
    return allowedTransition;
  }
  
  public void displaySeries(Graphics g, int nf, int lf){
    if(displayModel ==0){
      for (int ni=nf+1; ni<nmax; ni++){
	displayTransition(g,ni,nf-1,nf,nf-1);
      }
    }
    else{
      for (int ni=nf+1; ni<=nmax; ni++){
	for (int li=0; li< ni; li++){ // Conseration of Angular Momentum
	  if (li== lf+1 || li == lf-1){ 
	    displayTransition(g,ni,li,nf,lf);
	  }
	}
      }
    }
  }
  
  public void paint(Graphics g) {
    
    initSizes();
    setBackground(Color.black);
    int nf;

    g.setColor(Color.yellow);
    g.drawString("Energy Levels of ",plotWidth-150,plotHeight-40);
    g.drawString("the Hydrogen Atom",plotWidth-150,plotHeight-20);

    // axes
    g.setColor(Color.lightGray);
    g.drawLine(leftSpace,3,leftSpace,plotHeight);
    g.drawLine(leftSpace,3,leftSpace-3,6);
    g.drawLine(leftSpace,3,leftSpace+3,6);
    g.drawString("Energy",leftSpace+4,12);
    g.drawString("0",leftSpace-12,topMargin+5);
    g.drawLine(leftSpace-2,topMargin,leftSpace+2,topMargin);

    if (displayLabels){
      for (int n=1; n <= nmax; n++){
	if ( n < 5){
	  g.setColor(Color.lightGray);
	  g.drawString("n="+n,0, topMargin + (int) Energy(n) + 5);
	}
      }
      if (displayModel !=0){  // 0 = Bohr Model
	for (int l=0;  l <= lmax; l++){
	  g.setColor(Color.lightGray);
	  g.drawString("l="+l,10+leftSpace + l*plotWidth/(1+lmax), topMargin -6);
	}
      }
    }
    
    // draw Energy Levels
    for (int n=1; n <= nmax; n++){
      for (int l=0; l < n; l++){
	g.setColor(Color.yellow);
	if(displayModel ==0) drawLevel(g,n);
	if(displayModel !=0) drawLevel(g,n,l);
      }      
    }
      
    
    if (displayLyman){ 
      g.setColor(Color.red);
      if(displayModel ==0){
	displaySeries(g,1,0);
      }
      else{
	displaySeries(g,1,0);
      }
    }

    if (displayBalmer){ 
      g.setColor(Color.magenta);
      if(displayModel ==0){
	displaySeries(g,2,0);
      }
      else{
	nf = 2;
	for (int lf=0; lf < nf; lf++){
	displaySeries(g,nf,lf);
	}
      }
    }

    if (displayPaschen){ 
      nf = 3;
      g.setColor(Color.blue);
      if(displayModel ==0){
	displaySeries(g,3,0);
      }
      else{
	nf = 3;
	for (int lf=0; lf < nf; lf++){
	  displaySeries(g,nf,lf);
	}
      }
    }

  if (displayBrackett){ 
      nf = 4;
      g.setColor(Color.green);
      if(displayModel ==0){
	displaySeries(g,4,0);
      }
      else{
	nf = 4;
	for (int lf=0; lf < nf; lf++){
	  displaySeries(g,nf,lf);
	}
      }
    }


  }


  public void redraw(Integer Nmax, Integer Lmax){
    nmax = Nmax.intValue();
    lmax = Lmax.intValue();
    repaint();
  }


}

class HydrogenControls extends Panel{
  
  Checkbox Lyman;
  Checkbox Balmer;
  Checkbox Paschen;
  Checkbox Brackett;
  Checkbox TrueColor;
  Button btemp;

  TextField nmax;
  TextField lmax;
  Choice c = new Choice();
  HydrogenCanvas canvas;
  //  Double dtemp;
  Integer itemp;

  public HydrogenControls(HydrogenCanvas canvas){

    // s,p,d,f,g,h
    setLayout(new GridLayout(3,4,5,5));  /* nr,nc, vg, hg */
    this.canvas = canvas;
    Color darkMagenta = new Color(150,0,150);
    Color darkGreen = new Color(0,150,0);

    btemp = new Button("n_max = ");
    btemp.setForeground(Color.black);
    add (btemp);
    itemp = new Integer(canvas.nmax);
    add (nmax = new TextField(itemp.toString(),4 ));

    btemp = new Button("l_max = ");
    btemp.setForeground(Color.black);
    add (btemp);
    itemp = new Integer(canvas.lmax);
    add (lmax = new TextField(itemp.toString(),4 ));

    TrueColor = new Checkbox("True Colors");
    TrueColor.setState(canvas.trueColor);
    add (TrueColor);
    add (new Label("",Label.LEFT));
    add (new Label("Theory:",Label.LEFT));

    c.addItem("Bohr Model");
    c.addItem("Schrodinger");
    add(c);

    Lyman = new Checkbox("Lyman Series");
    Lyman.setState(canvas.displayLyman);
    add (Lyman);
    Balmer = new Checkbox("Balmer Series");
    Balmer.setState(canvas.displayBalmer);
    add (Balmer);
    Paschen = new Checkbox("Paschen Series");
    Paschen.setState(canvas.displayPaschen);
    add (Paschen);
    Brackett = new Checkbox("Brackett Series");
    Brackett.setState(canvas.displayBrackett);
    add (Brackett);
  }

  public boolean action(Event ev, Object arg){
    String label = (String)arg;
    if(ev.target instanceof Button 
       || ( arg instanceof Boolean
       || ev.target instanceof Choice )
       || ev.id == ev.END   ){         // Redisplay if Return
      //      int Theory;
      canvas.trueColor  = TrueColor.getState();
      canvas.displayLyman  = Lyman.getState();
      canvas.displayBalmer = Balmer.getState();
      canvas.displayPaschen = Paschen.getState();
      canvas.displayBrackett    = Brackett.getState();
      int Theory = c.getSelectedIndex();
      if (Theory == 0){
	canvas.displayModel = Theory;
      }
      else{
	canvas.displayModel = 1;
      }
      canvas.redraw(Integer.valueOf( nmax.getText().trim() ),
		    Integer.valueOf( lmax.getText().trim() )
		    );
      return true;
    }
    
    return false;
  }
  
}

class HydrogenLevelsBanner extends Panel{
  
  public HydrogenLevelsBanner(int n, int m){
    Color darkMagenta = new Color(150,0,150);
    setBackground(darkMagenta);
    setForeground(Color.white);
    setLayout(new GridLayout(n,m,40,-5));  /* nr,nc, vg, hg */
  }
}