/*
 * Encrypt_Current.bsh - Encrypts the current buffer content. The physical file
 * content will not be modified until user saves the buffer.
 *
 * Uses PBE with MD5 and DES algorithm. Macro will prompt the user for a 
 * password which will be used to encrypt the buffer content. Because encrypted
 * bytes can produce illegal characters for some buffer encodings, their are
 * replaced by their number representations separated by white space.
 *
 * David Mlejnek, mailto:davo@nadhlad.sk
 *
 */

import java.io.*;
import javax.crypto.*;
import javax.crypto.spec.*;
import javax.swing.border.*;

String TRANSFORMATION = "PBEWithMD5AndDES";
String ENCODING = buffer.getStringProperty(Buffer.ENCODING);
int BYTES_REPLACEMENT_OFFSET = 256;
int BYTES_REPLACEMENT_RADIX = 32;

int ENCRYPTED_FILE_WIDTH = 76;

void showDialog() {
  
  title = "Encrypt buffer";
  
  dialog = new JDialog(view, title, false);
  content = new JPanel(new BorderLayout());
  content.setBorder(new EmptyBorder(5, 5, 5, 5));
  dialog.setContentPane(content);
  
  textPanel = new JPanel(new GridLayout(2, 1));
  
  pwPanel1 = new JPanel(new GridLayout(1, 2));
  pwLabel1 = new JLabel("Enter password: ");
  pwField1 = new JPasswordField();
  pwPanel1.add(pwLabel1);
  pwPanel1.add(pwField1);
  textPanel.add(pwPanel1);
  
  pwPanel2 = new JPanel(new GridLayout(1, 2));
  pwLabel2 = new JLabel("Confirm password: ");
  pwField2 = new JPasswordField();
  pwPanel2.add(pwLabel2);
  pwPanel2.add(pwField2);
  textPanel.add(pwPanel2);
  
  content.add(textPanel, BorderLayout.CENTER);
  
  
  buttonPanel = new JPanel(new GridLayout(1, 2));
  buttonPanel.setBorder( new EmptyBorder(5, 0, 0, 0));
  
  okButton = new JButton("OK");
  cancelButton = new JButton("Cancel");
  
  buttonPanel.add(okButton);
  buttonPanel.add(cancelButton);
  
  content.add(buttonPanel, BorderLayout.SOUTH);
  
  okButton.addActionListener(this);
  cancelButton.addActionListener(this);
  
  dialog.getRootPane().setDefaultButton(okButton);
  
  
  actionPerformed(e) {
  
    this.dialog.dispose();
    
    cmd = e.getActionCommand();
    
    if(cmd.equals("OK")) {
      
      char[] passwd = this.pwField1.getPassword();
      char[] passwd2 = this.pwField2.getPassword();
      
      if(!equals(passwd, passwd2)) {
    
        Macros.error(view, "Passwords unequal, operation aborted.");
        
      } else {
        
        encryptBuffer(passwd);
        
      }
      
    }
    
    return;
  }

  dialog.pack();
  dialog.setLocationRelativeTo(view);
  dialog.setDefaultCloseOperation(JDialog.DISPOSE_ON_CLOSE);
  dialog.setVisible(true);
  
}

void encryptBuffer(char[] passwd) {
  
  Cipher pbeCipher = createCipher(passwd, Cipher.ENCRYPT_MODE);
  
  String content = textArea.getText();
  
  // Encode the string into bytes using buffer encoding
  byte[] data = content.getBytes(ENCODING);
  
  // Encrypt
  byte[] enc = pbeCipher.doFinal(data);

  //Replace bytes by their number representations
  content = encodeBytes(enc);

  textArea.setText(content);
  textArea.goToBufferStart(false);
    
}

Cipher createCipher(char[] passwd, int opmode) {
  int iterationCount = 20;
  byte[] salt = {
      (byte)0xc7, (byte)0x73, (byte)0x21, (byte)0x8c,
      (byte)0x7e, (byte)0xc8, (byte)0xee, (byte)0x99
  };
  
  // Create PBE parameter set
  PBEParameterSpec pbeParamSpec = new PBEParameterSpec(salt, iterationCount);
  PBEKeySpec pbeKeySpec = new PBEKeySpec(passwd);
  SecretKeyFactory keyFac = SecretKeyFactory.getInstance(TRANSFORMATION);
  SecretKey pbeKey = keyFac.generateSecret(pbeKeySpec);
  
  // Create PBE Cipher
  Cipher pbeCipher = Cipher.getInstance(TRANSFORMATION);
  pbeCipher.init(opmode, pbeKey, pbeParamSpec);
  
  return pbeCipher;
}

boolean equals(char[] c1, char[] c2) {
  if(c1.length != c2.length) {
    return false;
  }
  for(i=0; i<c1.length; i++) {
    if(c1[i] != c2[i]) {
      return false;
    }
  }
  return true;
}

String encodeBytes(byte[] source) {
  
  StringBuffer buf = new StringBuffer();
  width = 0;
  
  for(int i=0; i<source.length; i++) {
    
    int n = ((int) source[i]) + BYTES_REPLACEMENT_OFFSET;
    String code = Integer.toString(n, BYTES_REPLACEMENT_RADIX);
    buf.append(code);
    
    //insert newline char if width too large
    if(width < ENCRYPTED_FILE_WIDTH) {
      buf.append(" ");
      width += code.length() + 1;
    } else {
      buf.append("\n");
      width = 0;
    }
    
  }
  return buf.toString();
}

showDialog();