package java6226.lesson05;

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

public class Calculator extends JFrame {
    private JTextField display;
    private double result = 0;
    private String operator = "";
    private boolean calculating = true;

    public Calculator() {
        setTitle("Simple Calculator");
        setSize(250, 350);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLayout(new BorderLayout());

        display = new JTextField("0");
        display.setEditable(false);
        display.setHorizontalAlignment(JTextField.RIGHT);
        add(display, BorderLayout.NORTH);

        JPanel buttonPanel = new JPanel();
        buttonPanel.setLayout(new GridLayout(4, 4, 5, 5)); // 4行4列的按钮布局

        String[] buttonLabels = {
                "7", "8", "9", "/",
                "4", "5", "6", "*",
                "1", "2", "3", "-",
                "C", "0", "=", "+"
        };

        for (String label : buttonLabels) {
            JButton button = new JButton(label);
            button.setFont(new Font("Arial", Font.BOLD, 18));
            button.setPreferredSize(new Dimension(50, 40));
            button.addActionListener(new ButtonClickListener());
            buttonPanel.add(button);
        }

        add(buttonPanel, BorderLayout.CENTER);
        setVisible(true);
    }

    private class ButtonClickListener implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            String command = e.getActionCommand();
            if (calculating) {
                if (command.equals("C")) {
                    display.setText("0");
                    operator = "";
                    result = 0;
                    calculating = true;
                } else if (command.equals("+") || command.equals("-") || command.equals("*") || command.equals("/")) {
                    operator = command;
                    calculating = false;
                    display.setText("");
                } else if (command.equals("=")) {
                    calculate(Double.parseDouble(display.getText()));
                } else {
                    display.setText(display.getText() + command);
                }
            } else {
                if (command.equals("C")) {
                    display.setText("0");
                    operator = "";
                    result = 0;
                    calculating = true;
                } else if (command.equals("=")) {
                    calculate(Double.parseDouble(display.getText()));
                } else {
                    display.setText(display.getText() + command);
                }
            }
        }

        private void calculate(double num) {
            switch (operator) {
                case "+":
                    result += num;
                    break;
                case "-":
                    result -= num;
                    break;
                case "*":
                    result *= num;
                    break;
                case "/":
                    if (num != 0) {
                        result /= num;
                    } else {
                        display.setText("Error");
                        return;
                    }
                    break;
            }
            display.setText("" + result);
            operator = "";
            calculating = true;
        }
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new Calculator();
            }
        });
    }
}