import java.awt.BorderLayout;
import java.awt.GridLayout;
import java.awt.Panel;
import java.util.Stack;

import javax.swing.JApplet;
import javax.swing.JButton;

/**
 * @author RPJ
 * @version 14iii09
 *
 */
public class MagicSquareSolver extends JApplet implements Runnable {
        private static final int SIZE = 3;
        private int numCells = SIZE * SIZE;
        private Stack<PartialSquare> candidates;
        private PartialSquare candidate;
        
        private Panel myPanel;           // for graphic display
        private JButton[] myButtons;     // for graphic display
        public void init() {
                candidates = new Stack<PartialSquare>();
                candidate = new PartialSquare(SIZE);
                candidates.add(candidate);
                setUpDisplay();
                (new Thread(this)).start();
        }
        public void run() {
                while (!candidates.isEmpty()) {
                        candidate = candidates.pop();
                        updateDisplay();
                        if (candidate.success()) break;
                        for (PartialSquare ps : candidate.successors())
                                candidates.push(ps);
                }
                System.out.println("done");
        }
        
        // Stuff for the graphic display below here

        public void setUpDisplay() {
                setSize(400,400);
                setLayout(new BorderLayout());
                myPanel = new Panel();
                myPanel.setLayout(new GridLayout(SIZE,SIZE));
                myButtons = new JButton[numCells];
                for (int i = 0; i < numCells; i++) { // fill the panel with 0
                        myButtons[i] = new JButton(""+0);
                        myPanel.add(myButtons[i]);
                } 
                add(myPanel, BorderLayout.CENTER);
        }
        public void updateDisplay() {
                int i = 0;
                for (int num : candidate.getNums()) 
                        myButtons[i++].setText(""+num);
                validate();
        }
}