// Exercise12_12.java: Use CardLayout
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;

public class Exercise12_12 extends JApplet
  implements ActionListener
{
  private CardLayout queue = new CardLayout();
  private JPanel cardPanel = new JPanel();
  private JMenuItem jmiInt, jmiRat, jmiClose;

  // Main method
  public static void main(String[] args)
  {
    // Create a frame
    JFrame frame = new JFrame(
      "Running a program as an applet and an application");

    // Create an instance of MortgageApplet
    Exercise12_12 applet = new Exercise12_12();

    // Add the applet instance to the frame
    frame.getContentPane().add(applet, BorderLayout.CENTER);

    // Invoke init() and start()
    applet.init();
    applet.start();

    // Display the frame
    frame.pack();
    frame.setVisible(true);
  }

  public void init()
  {
    // Create JMenuBar jmb
    JMenuBar jmb = new JMenuBar();

    //add a menu "Operation" in jmb
    JMenu operationMenu = new JMenu("Operation", false);
    jmb.add(operationMenu);

    //add a menu "Exit" in jmb
    JMenu exitMenu = new JMenu("Exit", true);
    jmb.add(exitMenu);

    //add JMenuItems
    operationMenu.add(jmiInt = new JMenuItem("Integer"));
    operationMenu.add(jmiRat = new JMenuItem("Rational"));
    exitMenu.add(jmiClose = new JMenuItem("Close"));

    //create intPanel for integer arithmetic
    JPanel intPanel = new IntPanel();

    //create rationalPanel for rational arithmetic
    JPanel rationalPanel = new RationalPanel();

    cardPanel.setLayout(queue);
    cardPanel.add(intPanel, "Integer");
    cardPanel.add(rationalPanel, "Rational");

    //set FlowLayout in the frame
    getContentPane().setLayout(new BorderLayout());
    getContentPane().add(jmb, BorderLayout.NORTH);
    getContentPane().add(cardPanel, BorderLayout.CENTER);

    //register listener with the munu items
    jmiInt.addActionListener(this);
    jmiRat.addActionListener(this);
    jmiClose.addActionListener(this);
  }

  //handling menu selection
  public void actionPerformed(ActionEvent e)
  { String actionCommand = e.getActionCommand();
    if (e.getSource() instanceof JMenuItem)
    { if ("Integer".equals(actionCommand))
        queue.first(cardPanel);
      else if ("Rational".equals(actionCommand))
        queue.last(cardPanel);
      else if ("Close".equals(actionCommand))
        System.exit(0);
    }
  }
}

class IntPanel extends CalculationPanel
{
  IntPanel()
  {
    super("Integer Calculation");
  }

  void add()
  {
    int result = getNum1() + getNum2();
    //set result in JTextField tf3
    tfResult.setText(String.valueOf(result));
  }

  void subtract()
  {
    int result = getNum1() - getNum2();
    //set result in JTextField tf3
    tfResult.setText(String.valueOf(result));
  }

  void multiply()
  {
    int result = getNum1() * getNum2();
    //set result in JTextField tfResult
    tfResult.setText(String.valueOf(result));
  }

  void divide()
  {
    int result = getNum1() / getNum2();
    //set result in JTextField tfResult
    tfResult.setText(String.valueOf(result));
  }

  private int getNum1()
  {
    //use trim() to trim eztraneous space in the text field
    int num1 = Integer.parseInt(tfNum1.getText().trim());
    return num1;
  }

  private int getNum2()
  {
    //use trim() to trim eztraneous space in the text field
    int num2 = Integer.parseInt(tfNum2.getText().trim());
    return num2;
  }
}

class RationalPanel extends CalculationPanel
{
  RationalPanel()
  {
    super("Rational Calculation");
  }

  void add()
  {
    Rational num1 = getNum1();
    Rational num2 = getNum2();
    Rational result = num1.add(num2);

    //set result in JTextField tfResult
    tfResult.setText(result.toString());
  }

  void subtract()
  {
    Rational num1 = getNum1();
    Rational num2 = getNum2();
    Rational result = num1.subtract(num2);

    //set result in JTextField tfResult
    tfResult.setText(result.toString());
  }

  void multiply()
  {
    Rational num1 = getNum1();
    Rational num2 = getNum2();
    Rational result = num1.multiply(num2);

    //set result in JTextField tfResult
    tfResult.setText(result.toString());
  }

  void divide()
  {
    Rational num1 = getNum1();
    Rational num2 = getNum2();
    Rational result = num1.divide(num2);

    //set result in JTextField tfResult
    tfResult.setText(result.toString());
  }

  Rational getNum1()
  {
    StringTokenizer st1 = new
      StringTokenizer(tfNum1.getText().trim(), "/");
    int numer1 = Integer.parseInt(st1.nextToken());
    int denom1 = Integer.parseInt(st1.nextToken());
    return new Rational(numer1,denom1);
  }

  Rational getNum2()
  {
    StringTokenizer st2 = new
      StringTokenizer(tfNum2.getText().trim(), "/");
    int numer2 = Integer.parseInt(st2.nextToken());
    int denom2 = Integer.parseInt(st2.nextToken());
    return new Rational(numer2,denom2);
  }
}

/*design a generic calculation user interface for int and
  rational arithmetic*/
abstract class CalculationPanel extends JPanel
  implements ActionListener
{ private JPanel p0 = new JPanel();
  private JPanel p1 = new JPanel();
  private JPanel p2 = new JPanel();
  JTextField tfNum1, tfNum2, tfResult;
  private JButton jbtAdd, jbtSub, jbtMul, jbtDiv;

  public CalculationPanel(String title)
  { p0.add(new JLabel(title));

    //add labels and text fields
    p1.setLayout(new FlowLayout());
    p1.add(new JLabel("Nujmber 1"));
    p1.add(tfNum1 = new JTextField(" ", 3));
    p1.add(new JLabel("Nujmber 2"));
    p1.add(tfNum2 = new JTextField(" ", 3));
    p1.add(new JLabel("Result"));
    p1.add(tfResult = new JTextField(" ", 4));
    tfResult.setEditable(false);

    //set FlowLayout for p2
    JPanel p2 = new JPanel();
    p2.setLayout(new FlowLayout());
    p2.add(jbtAdd = new JButton("Add"));
    p2.add(jbtSub = new JButton("Subtract"));
    p2.add(jbtMul = new JButton("Multiply"));
    p2.add(jbtDiv = new JButton("Divide"));

    //add panels into CalculationPanel
    setLayout(new BorderLayout());
    add("North",p0);
    add("Center",p1);
    add("South",p2);

    //register listener for source objects
    jbtAdd.addActionListener(this);
    jbtSub.addActionListener(this);
    jbtMul.addActionListener(this);
    jbtDiv.addActionListener(this);
  }

  public void actionPerformed(ActionEvent e)
  { String actionCommand = e.getActionCommand();
    if (e.getSource() instanceof JButton)
    { if ("Add".equals(actionCommand))
        add();
      else if ("Subtract".equals(actionCommand))
        subtract();
      else if ("Multiply".equals(actionCommand))
        multiply();
      else if ("Divide".equals(actionCommand))
        divide();
    }
  }

  abstract void add();

  abstract void subtract();

  abstract void multiply();

  abstract void divide();
}