import objectdraw.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;


public class Powers extends Controller implements ActionListener  {
    private static final int FONTSIZE = 18;
    private static final int INPUT_WIDTH = 4;
    
    // Recursive algorithm to compute powers
    public int power(int base, int n) {
        if (n==0) {
            return 1;    
        } else {
            return base*(power(base,n-1));    
        }
    }

    // Fast recursive algorithm to compute powers
    public int fastPower(int base, int n) {
        if (n == 0) {
            return 1;
        } else if (n % 2 == 0) {  // n is even
            return fastPower(base * base, n / 2);
        } else {                  // n is odd
            return base * fastPower(base, n - 1);
        }
    }

    private JTextField input;
    private JLabel l1, l0;
    private JTextField input2;
    private JButton goButton;
    private JLabel answer;

    public void begin() {
        l0 = new JLabel("power(");
        input = new JTextField("0", INPUT_WIDTH);
        l1 = new JLabel(", ");
        input2 = new JTextField("0", INPUT_WIDTH);
        answer = new JLabel(") = 0              ");
        goButton = new JButton("Go!");

        JPanel panel = new JPanel();

        input.setFont(new Font("System", 0, FONTSIZE));
        l0.setFont(new Font("System", 0, FONTSIZE));
        l1.setFont(new Font("System", 0, FONTSIZE));
        input2.setFont(new Font("System", 0, FONTSIZE));
        answer.setFont(new Font("System", 0, FONTSIZE));

        panel.add(l0);
        panel.add(input);
        panel.add(l1);
        panel.add(input2);
        panel.add(answer);
    
        JPanel buttonPanel = new JPanel();
        buttonPanel.add(goButton);

        Container contentPane = getContentPane();
        contentPane.add(panel, BorderLayout.NORTH);
        contentPane.add(buttonPanel, BorderLayout.CENTER);
     
        goButton.addActionListener(this);
        input.addActionListener(this);
        input2.addActionListener(this);
        validate();
    }

    // calculate power
    public void actionPerformed(ActionEvent e) {
        int base = Integer.parseInt(input.getText());
        int n = Integer.parseInt(input2.getText());
        answer.setText(") = " + power(base, n));
    }
}