// 文件名： test01.java

import javax.crypto.*;
import javax.crypto.spec.*;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.nio.charset.StandardCharsets;

public class test01 extends JFrame implements ActionListener {
    private JFileChooser fileChooser = new JFileChooser();
    private JTextArea inputArea = new JTextArea(10, 40);
    private JTextArea outputArea = new JTextArea(10, 40);
    private JButton encryptButton = new JButton("加密");
    private JButton decryptButton = new JButton("解密");
    private JButton fileButton = new JButton("選擇文件");
    private JComboBox<String> algorithmBox = new JComboBox<String>(new String[] {"DES", "AES"});
    private JLabel keyLabel = new JLabel("密鑰:");
    private JTextField keyField = new JTextField(20);

    public test01() {
        super("對(duì)稱(chēng)加密算法實(shí)現(xiàn)");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JPanel mainPanel = new JPanel();
        mainPanel.setLayout(new BoxLayout(mainPanel, BoxLayout.Y_AXIS));
        JPanel inputPanel = new JPanel();
        inputPanel.add(new JLabel("輸入:"));
        inputPanel.add(new JScrollPane(inputArea));
        JPanel outputPanel = new JPanel();
        outputPanel.add(new JLabel("輸出:"));
        outputPanel.add(new JScrollPane(outputArea));
        JPanel buttonPanel = new JPanel();
        buttonPanel.add(encryptButton);
        buttonPanel.add(decryptButton);
        buttonPanel.add(fileButton);
        buttonPanel.add(algorithmBox);
        buttonPanel.add(keyLabel);
        buttonPanel.add(keyField);
        mainPanel.add(inputPanel);
        mainPanel.add(outputPanel);
        mainPanel.add(buttonPanel);
        encryptButton.addActionListener(this);
        decryptButton.addActionListener(this);
        fileButton.addActionListener(this);
        setContentPane(mainPanel);
        pack();
        setVisible(true);
    }

    public void actionPerformed(ActionEvent e) {
        if (e.getSource() == encryptButton) {
            encrypt();
        } else if (e.getSource() == decryptButton) {
            decrypt();
        } else if (e.getSource() == fileButton) {
            chooseFile();
        }
    }

    private void chooseFile() {
        int returnValue = fileChooser.showOpenDialog(this);
        if (returnValue == JFileChooser.APPROVE_OPTION) {
            File file = fileChooser.getSelectedFile();
            try {
                BufferedReader reader = new BufferedReader(new FileReader(file));
                inputArea.setText("");
                String line = reader.readLine();
                while (line != null) {
                    inputArea.append(line);
                    line = reader.readLine();
                    if (line != null) {
                        inputArea.append("\n");
                    }
                }
                reader.close();
            } catch (IOException e) {
                JOptionPane.showMessageDialog(this, "Error reading file: " + e.getMessage(), "Error", JOptionPane.ERROR_MESSAGE);
            }
        }
    }

    private void encrypt() {
        try {
            String algorithm = (String) algorithmBox.getSelectedItem();
            String keyString = keyField.getText();
            byte[] keyBytes = keyString.getBytes(StandardCharsets.UTF_8);
            SecretKey key;
            if (algorithm.equals("DES")) {
                key = new SecretKeySpec(keyBytes, "DES");
            } else {
                key = new SecretKeySpec(keyBytes, "AES");
            }
            Cipher cipher = Cipher.getInstance(algorithm);
            cipher.init(Cipher.ENCRYPT_MODE, key);
            String input = inputArea.getText();
            byte[] inputBytes = input.getBytes(StandardCharsets.UTF_8);
            byte[] outputBytes = cipher.doFinal(inputBytes);
            String output = new String(outputBytes, StandardCharsets.UTF_8);
            outputArea.setText(output);
        } catch (Exception e) {
            JOptionPane.showMessageDialog(this, "Error encrypting: "
                    + e.getMessage(), "Error", JOptionPane.ERROR_MESSAGE);
        }
    }


    private void decrypt() {
        try {
            String algorithm = (String) algorithmBox.getSelectedItem();
            String keyString = keyField.getText();
            byte[] keyBytes = keyString.getBytes();
            SecretKey key;
            if (algorithm.equals("DES")) {
                key = new SecretKeySpec(keyBytes, "DES");
            } else {
                key = new SecretKeySpec(keyBytes, "AES");
            }
            Cipher cipher = Cipher.getInstance(algorithm);
            cipher.init(Cipher.DECRYPT_MODE, key);
            String input = inputArea.getText();
            byte[] inputBytes = input.getBytes();
            byte[] outputBytes = cipher.doFinal(inputBytes);
            String output = new String(outputBytes);
            outputArea.setText(output);
        } catch (Exception e) {
            JOptionPane.showMessageDialog(this, "Error decrypting: " +
                    e.getMessage(), "Error", JOptionPane.ERROR_MESSAGE);
        }
    }

    public static void main(String[] args) {
        new test01();
    }
}