import java.awt.FlowLayout;
import java.awt.BorderLayout;
import javax.swing.*;
import javax.swing.border.*;
import java.awt.event.*;
import java.security.AccessControlException;

/*
 * The only code that is missing is in the "code" method below.
 * Everything else should work fine, so if you implement the
 * "code" method your pogram will work properly.
 */
public class Shifter extends JFrame implements ActionListener
{
    private static final int ENCODE = 1;
    private static final int DECODE = 2;
    private static final int MIN_CODE = 32;
    private static final int MAX_CODE = 126;
    private static final int CODE_RANGE = MAX_CODE - MIN_CODE;
    
    private int key = -1;
    private JTextField keyField = new JTextField(10);
    private JTextArea plainText = new JTextArea(7, 50);
    private JTextArea codedText = new JTextArea(7, 50);
    private JButton encodeButton = new JButton("Encode");
    private JButton decodeButton = new JButton("Decode");
    
    private class WindowCloser extends WindowAdapter
    {
        public void windowClosing(WindowEvent we)
        {
            try
            {
                setVisible(false);
                System.exit(0);
            }
            catch(AccessControlException err)
            {
            }
            catch(Exception ex)
            {
            }
            catch(Error err)
            {                
            }
        }
    }
    
    public Shifter()
    {
        super("Shift Coder");
        
        plainText.setBorder(new TitledBorder(new EtchedBorder(), "Plain Text"));
        codedText.setBorder(new TitledBorder(new EtchedBorder(), "Coded Text"));
        
        
        JPanel buttonPanel = new JPanel(new FlowLayout());
        buttonPanel.add(encodeButton);
        buttonPanel.add(decodeButton);
        
        JPanel keyPanel = new JPanel(new BorderLayout());
        keyPanel.add("Center", keyField);
        keyPanel.add("West", new JLabel("Key = "));
        
        JPanel actionPanel = new JPanel(new FlowLayout());
        actionPanel.add(keyPanel);
        actionPanel.add(buttonPanel);
        
        JSplitPane textPanel = new JSplitPane(JSplitPane.VERTICAL_SPLIT);
        textPanel.setTopComponent(new JScrollPane(plainText));
        textPanel.setBottomComponent(new JScrollPane(codedText));
        
        getContentPane().setLayout(new BorderLayout());
        getContentPane().add("Center", textPanel);
        getContentPane().add("South", actionPanel);
        
        encodeButton.addActionListener(this);
        decodeButton.addActionListener(this);
        addWindowListener(new WindowCloser());
        
        validate();
        pack();
    }

    private void setKey(int mode)
    {
        try
        {
            key = Integer.parseInt(keyField.getText().trim());
            if (key <= 0)
                throw new NumberFormatException("Number must be positive");
            if (key >= CODE_RANGE)
                throw new NumberFormatException("Number must be less than " + CODE_RANGE);
            if (mode == ENCODE)
                encode();
            else if (mode == DECODE)
                decode();
        }
        catch(NumberFormatException nfe)
        {
            JOptionPane.showMessageDialog(this, "Error: the key must be a positive integer less than " + MAX_CODE);
        }
    }

    /*
     * CHANGE THIS METHOD OTHERWISE NOTHING HAPPENS
     */
    private String code(String text, int key)
    {
        StringBuffer output = new StringBuffer();
        for (int i = 0; i < text.length(); i++)
        {
           // this is the loop you need to complete. The varialbe "text"
           // contains the text to encode, and "key" contains the 
           // number by which to shift every character.
        }
        return output.toString();
    }
    
    private void encode()
    {
        String text = plainText.getText();
        if (text.equals(""))
            JOptionPane.showMessageDialog(this, "No text to encode");
        else
            codedText.setText(code(text, key));
    }
    
    private void decode()
    {
        String text = codedText.getText();
        if (text.equals(""))
            JOptionPane.showMessageDialog(this, "No text to decode");
        else
            plainText.setText(code(text, -key));        
    }
    
    public void actionPerformed(ActionEvent ae)
    {
        if (ae.getSource() == encodeButton)
            setKey(ENCODE);
        else if (ae.getSource() == decodeButton)
            setKey(DECODE);
    }
    
    public static void main(String args[])
    {
        Shifter s = new Shifter();
        s.setVisible(true);
    }
}