/*
 * Cay S. Horstmann & Gary Cornell, Core Java
 * Published By Sun Microsystems Press/Prentice-Hall
 * Copyright (C) 1997 Sun Microsystems Inc.
 * All Rights Reserved.
 *
 * Permission to use, copy, modify, and distribute this 
 * software and its documentation for NON-COMMERCIAL purposes
 * and without fee is hereby granted provided that this 
 * copyright notice appears in all copies. 
 * 
 * THE AUTHORS AND PUBLISHER MAKE NO REPRESENTATIONS OR 
 * WARRANTIES ABOUT THE SUITABILITY OF THE SOFTWARE, EITHER 
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE 
 * IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A 
 * PARTICULAR PURPOSE, OR NON-INFRINGEMENT. THE AUTHORS
 * AND PUBLISHER SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED 
 * BY LICENSEE AS A RESULT OF USING, MODIFYING OR DISTRIBUTING 
 * THIS SOFTWARE OR ITS DERIVATIVES.
 */
 
/**
 * @version 1.00 10 Sep 1997
 * @author Cay Horstmann
 */


/*
 *  Modified by M. Gallant  09/12/2000 
 *   - converted to applet (requires digital signature).
 *   - suitable for IE4+ or JavaPlugin1.2.2+.
 *   - MessageDigest not implemented in Netscape JVM.
 *   - modified loadBytes() for faster file reading.
 *   - modified computeDigest() for local formatting. 
 *   - replaced menu with two buttons; modified actionPerformed()
 *   -  Modified  04/21/2004 to add b64 encoding of hash
 */

import java.io.*;
import java.security.*;
import java.awt.*;
import java.awt.event.*;

public final class MessageDigestApplet extends java.applet.Applet
   implements ActionListener, ItemListener{

   private Button b0, b1, b2 ;
   private TextArea message = new TextArea();
   private TextField digest = new TextField();
   private TextField digest64 = new TextField();
   private String filename = null;
   private String lastDir = "";
   private MessageDigest currentAlgorithm;


  public void init(){
      this.setLayout(new BorderLayout(7,7)) ;
      Panel p = new Panel();
       b0 = new Button("Clear text") ;
       b0.addActionListener(this) ;
       p.add(b0) ;
       b1 = new Button("File digest") ;
       b1.addActionListener(this) ;
       p.add(b1) ;
       b2 = new Button("Text digest") ;
       b2.addActionListener(this) ;
       p.add(b2) ;

      CheckboxGroup g = new CheckboxGroup();
      addCheckbox(p, "SHA-1", g, true);
      addCheckbox(p, "MD5", g, false);    
      add(p, "North");
      add(message, "Center");

	p = new Panel(new GridLayout(2,1, 7, 7));
	p.add(digest);
	p.add(digest64);
      add(p, "South");

      //add(new Label(""), "East") ;
      //add(new Label(""), "West") ;

      digest.setFont(new Font("Courier", Font.PLAIN, 12));
      digest64.setFont(new Font("Courier", Font.PLAIN, 12));

      setAlgorithm("SHA-1");
   }


   public Insets getInsets() {
    return new Insets(5,7,7,7) ;
   }

   private void addCheckbox(Panel p, String name, 
      CheckboxGroup g, boolean v)
   {  Checkbox c = new Checkbox(name, g, v);
      c.addItemListener(this);
      p.add(c);
   }
   
  public void itemStateChanged(ItemEvent evt)
   {  if (evt.getStateChange() == ItemEvent.SELECTED) 
         setAlgorithm((String)evt.getItem());
   }

   private void setAlgorithm(String alg)
   {  try
      {  currentAlgorithm = MessageDigest.getInstance(alg);
      }
      catch(NoSuchAlgorithmException e)
      {  digest.setText("" + e);
      }
   }

  public void actionPerformed(ActionEvent evt)
   {  String arg = evt.getActionCommand();
      if (arg.equals("File digest"))
      {  FileDialog d = new FileDialog(new Frame(),
            "Open text file", FileDialog.LOAD);
         d.setFile("*.txt");
         d.setDirectory(lastDir);
         d.show();
         String f = d.getFile();
         lastDir = d.getDirectory();
         if (f != null)
         {  filename = lastDir + f;
            computeDigest(loadBytes(filename));
         }
      }
      else if (arg.equals("Text digest"))   
      {  String m = message.getText();
         computeDigest(m.getBytes());
      }
      else if (arg.equals("Clear text"))   
      { message.setText("");
        digest.setText("");
        digest64.setText("");
      }

   }


   private byte[] loadBytes(String name)
   {  FileInputStream in = null;
   
      try
      {  in = new FileInputStream(name); 
         ByteArrayOutputStream buffer 
            = new ByteArrayOutputStream();
 
 	 int bytesread = 0;
 	 byte [] tbuff = new byte[512] ;

       while(true) {
         bytesread = in.read(tbuff);
          if (bytesread == -1)    // if EOF
            break ;
          buffer.write(tbuff,0,bytesread) ;
         }
        return buffer.toByteArray();
      }
      catch (IOException e)
      {  if (in != null) 
         {  try { in.close(); } catch (IOException e2) {}
         }
         return null;
      }
   }
   

   private void computeDigest(byte[] b)
   {  currentAlgorithm.reset();
      currentAlgorithm.update(b);
      byte[] hash = currentAlgorithm.digest();
      String d = "";
      int usbyte = 0;  // unsigned byte
      for (int i = 0; i < hash.length; i++){
       usbyte = hash[i] & 0xFF ;   // byte-wise AND converts signed byte to unsigned.
       if(usbyte<16)
        d += "0" + Integer.toHexString(usbyte);   // pad on left if single hex digit.
         else
        d +=       Integer.toHexString(usbyte);
      } 
	digest.setText("Hash(hex): " + d.toUpperCase());
	//----- Display the digest as b64 encoded --------------
	sun.misc.BASE64Encoder enc = new sun.misc.BASE64Encoder() ;
	String b64str = enc.encodeBuffer(hash).trim();  //removing any leading/trailing whitespace
	digest64.setText("Hash(b64): " + b64str) ;
   }


 public void paint(Graphics g) {   // put black border around applet.
   g.setColor(Color.black) ;
   g.drawRect(0,0,this.getSize().width-1, this.getSize().height-1) ; 
  }


}