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

public class KnightsTour extends JFrame
{
    private KnightsTourBoard m_ktBoard = new KnightsTourBoard(5, 5);
    private Thread m_tourThread;

    /* GUI elements */
    private ActionEventHandler m_handler = new ActionEventHandler(this);
    private JTextField m_widthField;
    private JTextField m_heightField;
    private JTextField m_startXField;
    private JTextField m_startYField;
    private JButton m_startButton;
    private JButton m_cancelButton;
    private JPanel m_mainPanel;
    private JPanel m_boardPanel;
    private JLabel m_statusLabel;

    public KnightsTour()
    {
        super("Josh's Knights Tour project for CS621");
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setSize(500, 600);

        /* set up the main window contents */
        getContentPane().add(m_mainPanel = new JPanel(new BorderLayout()) {{
            setBorder(BorderFactory.createEmptyBorder(9, 9, 9, 9));
            add(new JPanel() {{
                setLayout(new BoxLayout(this, BoxLayout.X_AXIS));
                setBorder(BorderFactory.createEmptyBorder(0, 0, 0, 7));
                add(new JPanel() {{     /* board size panel */
                    setBorder(BorderFactory.createTitledBorder("Board Size"));
                    add(new JPanel() {{
                        setBorder(BorderFactory.createEmptyBorder());
                        setLayout(new GridLayout(2, 2, 5, 5));
                        add(new JLabel("Width:", SwingConstants.RIGHT));
                        add(m_widthField = new JTextField("5"));
                        add(new JLabel("Height:", SwingConstants.RIGHT));
                        add(m_heightField = new JTextField("5"));
                    }});
                }});
                add(new Box.Filler(new Dimension(5, 0),
                                   new Dimension(5, 0),
                                   new Dimension(5, 0)));
                add(new JPanel() {{     /* starting position panel */
                    setBorder(BorderFactory.createTitledBorder("Starting Position"));
                    add(new JPanel() {{
                        setBorder(BorderFactory.createEmptyBorder());
                        setLayout(new GridLayout(2, 2, 5, 5));
                        add(new JLabel("Column (X):", SwingConstants.RIGHT));
                        add(m_startXField = new JTextField("2"));
                        add(new JLabel("Row (Y):", SwingConstants.RIGHT));
                        add(m_startYField = new JTextField("2"));
                    }});
                }});
                add(new Box.Filler(new Dimension(5, 0),
                                   new Dimension(5, 0),
                                   new Dimension(5, 0)));
                add(new JPanel() {{     /* start button panel */
                    setBorder(BorderFactory.createTitledBorder("Start"));
                    add(new JPanel() {{
                        setBorder(BorderFactory.createEmptyBorder());
                        setLayout(new BoxLayout(this, BoxLayout.Y_AXIS));
                        add(m_startButton = new JButton("Start Knight's Tour"));
                        m_startButton.addActionListener(m_handler);
                        add(m_cancelButton = new JButton("Cancel Knight's Tour"));
                        m_cancelButton.addActionListener(m_handler);
                        m_cancelButton.setVisible(false);
                        add(new Box.Filler(new Dimension(0, 4),
                                           new Dimension(0, 4),
                                           new Dimension(0, 4)));
                        add(m_statusLabel = new JLabel());
                    }});
                }});
                add(new Box.Filler(new Dimension(0, 0),
                                   new Dimension(Short.MAX_VALUE, 0),
                                   new Dimension(10000, 10000)));
            }}, BorderLayout.NORTH);
        }});

        createBoardPanel();

        setVisible(true);
    }

    private void createBoardPanel()
    {
        int width = m_ktBoard.getWidth();
        int height = m_ktBoard.getHeight();
        JPanel oldBoardPanel = m_boardPanel;
        m_boardPanel = new JPanel(new GridLayout(height, width, 1, 1));
        m_boardPanel.setBorder(BorderFactory.createEmptyBorder(5, 0, 0, 0));
        for (int y = 0; y < height; y++)
        {
            for (int x = 0; x < width; x++)
            {
                JLabel l = new JLabel(m_ktBoard.getStepAt(x, y) == 0
                        ? ""
                        : new Integer(m_ktBoard.getStepAt(x, y)).toString(),
                    SwingConstants.CENTER);
                l.setBorder(BorderFactory.createBevelBorder(BevelBorder.LOWERED));
                m_boardPanel.add(l);
            }
        }
        if (oldBoardPanel != null)
            m_mainPanel.remove(oldBoardPanel);
        m_mainPanel.add(m_boardPanel);
        m_mainPanel.validate();
    }

    private class ActionEventHandler implements ActionListener
    {
        private KnightsTour m_kt;

        public ActionEventHandler(KnightsTour kt) { m_kt = kt; }

        public void actionPerformed(ActionEvent e)
        {
            if (e.getSource() == m_startButton)
            {
                m_statusLabel.setText("Running...");

                /* first validate input text fields */
                int width, height, startx, starty;
                try
                {
                    width = Integer.parseInt(m_widthField.getText());
                    height = Integer.parseInt(m_heightField.getText());
                    startx = Integer.parseInt(m_startXField.getText());
                    starty = Integer.parseInt(m_startYField.getText());
                }
                catch (NumberFormatException nfe)
                {
                    m_statusLabel.setText("Non-numerical input!");
                    return;
                }
                if (width < 1 || height < 1 || startx < 0 || starty < 0 ||
                        startx >= width || starty >= height)
                {
                    m_statusLabel.setText("Invalid input!");
                    return;
                }

                /* create a new KnightsTourBoard object */
                m_ktBoard = new KnightsTourBoard(width, height);
                createBoardPanel();
                
                /* run the tour in a separate thread */
                m_startButton.setVisible(false);
                m_cancelButton.setVisible(true);

                m_tourThread = new Thread(new TourThread(startx, starty));
                m_tourThread.start();
            }
            else if (e.getSource() == m_cancelButton)
            {
                if (m_tourThread != null)
                {
                    m_tourThread.stop();
                    m_tourThread = null;
                    m_startButton.setVisible(true);
                    m_cancelButton.setVisible(false);
                    m_statusLabel.setText("Cancelled.");
                }
            }
        }
    }

    private class TourThread implements Runnable
    {
        int m_startx, m_starty;

        public TourThread(int startx, int starty)
        {
            m_startx = startx;
            m_starty = starty;
        }

        public void run()
        {
            if (m_ktBoard.tour(m_startx, m_starty))
            {
                SwingUtilities.invokeLater(new Runnable() {
                    public void run()
                    {
                        createBoardPanel();
                        m_statusLabel.setText("Finished.");
                        m_startButton.setVisible(true);
                        m_cancelButton.setVisible(false);
                    }
                });
            }
            else
            {
                SwingUtilities.invokeLater(new Runnable() {
                    public void run()
                    {
                        createBoardPanel();
                        m_statusLabel.setText("Solution not found!");
                        m_startButton.setVisible(true);
                        m_cancelButton.setVisible(false);
                    }
                });
            }
            m_tourThread = null;
        }
    }

    public static void main(String[] args)
    {
        KnightsTour kt = new KnightsTour();
    }
}