import javax.swing.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class guiGLM {

 private JButton cipherBtn;
 private JButton resetBtn;
 private JButton exitBtn;
 private JPanel wholePanel;
 private JPanel botmPanl;
 private JPanel botmR;
 private JPanel botmL;
 private JPanel botmM;
 private JPanel topPanl;
 private JTextField key;
 private JTextField plainText;
 private JTextField cipherText;
 private JPanel midPanl;
 private JPanel midM;
 private JPanel midL;
 private JLabel keyL;
 private JLabel cipherL;
 private JLabel plainL;
 private JPanel midR;

 public guiGLM() {
 cipherBtn.addActionListener(new ActionListener() { //cipherBtn
 @Override
 public void actionPerformed(ActionEvent e) {
// key.setText("378126864sbdashdj");
 String k = key.getText();
 String plainString = plainText.getText();
 cipherText.setText(cipher(k, plainString).toString());
 }
 });

 exitBtn.addActionListener(new ActionListener() { //exitBtn
 @Override
 public void actionPerformed(ActionEvent e) {
 System.exit(0);
 }
 });
 resetBtn.addActionListener(new ActionListener() { //resetBtn
 @Override
 public void actionPerformed(ActionEvent e) {
 key.setText("");
 plainText.setText("");
 cipherText.setText("");
 }
 });
 }

 private StringBuilder cipher(String k, String plainString) {
 int bias = Integer.parseInt(k);
 if(plainString.isEmpty()) {
 return new StringBuilder("");
 }
 else if(bias == 0) {
 return new StringBuilder(plainString);
 }
 else {
 return Caesar(bias, plainString);
 }

 }

 private StringBuilder Caesar(int k, String s) {
 int mod_A = 26;
 int delta = (int)'A'; // 便于移位
 char[] plain = s.toCharArray();
 StringBuilder cipher = new StringBuilder();
 int x = 0;
 for (int i = 0; i < plain.length; i++) {
 x = (int)plain[i]; //逐个检查
 if(x >= (int)'A' && x<= (int)'Z') { //大写字母
 x = (x - delta + k) % mod_A + delta; //移位
 }
 else if(x >= (int)'a' && x<= (int)'z') { //小写字母
 x = (x - delta - 32 + k) % mod_A + delta; //移位
 }
 else {continue;}
 cipher.append((char)(x)); //保存结果

 }
 return cipher;
 }

 public static void main(String[] args) {
 JFrame frame = new JFrame("guiGLM");
 frame.setContentPane(new guiGLM().wholePanel);
 frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 frame.pack();
 frame.setVisible(true);
 }
}