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

/**
    Program:  ShiftCipher
    Purpose:  do shift cipher in text areas
    @author:  Paul Garrett, garrett@math.umn.edu
	 copyright Paul Garrett, GNU Public License, 1997
    @version: Mon Oct 20 11:44:52 CDT 1997
*/

final public class ShiftCipher extends Applet {

  int height, width;
  Color background_color, foreground_color;

  TextArea plainTA, cipherTA;
  Button encryptB, decryptB;
  TextField keyF;
  int theKey;
  boolean queryDataOK;
  TextField msgF;

  /***************************/

  public void init() {
    try {
      background_color = 
	new Color(Integer.parseInt(getParameter("background_color"), 16));
      foreground_color = 
	new Color(Integer.parseInt(getParameter("foreground_color"), 16));
      height = Integer.parseInt(getParameter("height"));
      width = Integer.parseInt(getParameter("width"));
    }
    catch (Exception e) {
      background_color = new Color(0xbaaaaa);
      foreground_color = new Color(0x503030);
      height = 320;
      width = 550;
    }
    setBackground(background_color);
    setForeground(foreground_color);

    setFont(new Font("TimesRoman", Font.PLAIN, 14));

    encryptB = new Button("encrypt");
    decryptB = new Button("decrypt");
    add(encryptB);
    add(decryptB);

    keyF = new TextField(5);
    add(new Label("    Key ="));
    add(keyF);

    msgF = new TextField(30);
    add(msgF);

    plainTA = new TextArea(5,60);
    add(plainTA);
    cipherTA = new TextArea(5,70);
    add(cipherTA);
    
  } // end of init()

  synchronized String shift(int key, String inp) {
    // converts to lower-case... and returns lower-case
    key = ((key % 26) + 26) % 26;
    byte b;
    String outp;
    byte[] theBytes = new byte[inp.length()];
    inp.toLowerCase().getBytes(0, inp.length(), theBytes, 0);
    // latter puts the lower-cased version into "theBytes"
    for (int i=0; i < theBytes.length; i++) {
      if (theBytes[i] >= 97 && theBytes[i] < 97+26) {
		  theBytes[i] = (byte) (((theBytes[i] - 97 + key +26)%26) + 97);
      }
    }
    outp = new String(theBytes, 0); // high byte set to 0
    return outp;
  }

  public synchronized boolean action(Event e, Object arg) {
    if (e.target instanceof Button) {
      try {
	theKey = Integer.parseInt(keyF.getText());
	queryDataOK = true;
      }
      catch (NumberFormatException nfe) {
	queryDataOK = false;
	msgF.setText("The key must be an integer.");
      }
      if (queryDataOK) {
	if (e.target == encryptB) {
	  cipherTA.setText(shift(theKey, plainTA.getText()).toUpperCase()); //__EDIT__
	  msgF.setText("Encrypting with key "+theKey);
	}
	else if (e.target == decryptB) {
	  int neg_key = -theKey;
	  plainTA.setText(shift(-theKey,cipherTA.getText())); //__EDIT__
	  msgF.setText("Decrypting with key "+theKey);
	}
      }
      else {
	msgF.setText("Improper data");
      }
      return true;
    }
    else {
      return false; // old AWT event model...
    }
  } 

    
}

/*********** The End ************/