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

//--> Note: Comments starting with //--> are meta-comments about how to write
//--> OO Java code and wouldn't appear in a production environment.

/**
 * Class representing a popup login dialog with username
 * and password.  Responsible for collecting user input
 * and passing it to a SecuritySystem for validation.
 */
public class PasswordPopup extends JFrame {
    private final SecuritySystem _securitySystem;  // Does security checks
    private final JTextField _userNameField; // UI field containing username
    private final JPasswordField _passwordField; // UI field containing password

    /** Constructor, initializes object with given owner. */
    public PasswordPopup(SecuritySystem ss) {
        //--> Superclass JFrame constructor sets text of title bar from argument:
        super("Login");

        // Keep track of owner:
        _securitySystem = ss;

        _userNameField = new JTextField(16);
        _passwordField = new JPasswordField(16);

        // Check username/password when user hits enter
        // key in password field.  Use the owner SecuritySystem
        // for the actual security check.
        _passwordField.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                String username = _userNameField.getText();
                char[] password = _passwordField.getPassword();
                
                if (!_securitySystem.doLogin(username,password)) {
                    JOptionPane.showMessageDialog(null,
       	                "Invalid user name or password.  Try again.",
                	    "Login Failed",
    	                JOptionPane.ERROR_MESSAGE);
                }
            }
        });

        // Shut down system when user closes window.
        this.addWindowListener(new WindowAdapter() {
                public void windowClosing(WindowEvent e) {
                    System.out.println("Shutting down security system.");
                    System.exit(0);
                }
            }
        );
        
        //--> The code to initialize the layout of various components
        //--> is off in its own function just to keep it out of the way.
        setupLayout();
    }

    private void setupLayout() {
        JPanel labelPane = new JPanel();
        labelPane.setLayout(new GridLayout(0, 1));
        labelPane.add(new JLabel("User name:"));
        labelPane.add(new JLabel("Password:"));

        // Lay out the text fields in a panel:
        JPanel fieldPane = new JPanel();
        fieldPane.setLayout(new GridLayout(0, 1));
        fieldPane.add(_userNameField);
        fieldPane.add(_passwordField);

        // Put the panels in another panel, labels on left,
        // text fields on right:
        JPanel contentPane = new JPanel();
        contentPane.setBorder(BorderFactory.createEmptyBorder(5, 5,
                                                              5, 5));
        contentPane.setLayout(new BorderLayout());
        contentPane.add(labelPane, BorderLayout.CENTER);
        contentPane.add(fieldPane, BorderLayout.EAST);

        //--> The "this." below isn't necessary; it's just there
        //--> to make it clear where setContentPane and pack live.
        //--> In most production code the "this." is omitted.
        this.setContentPane(contentPane);
        this.pack();
    }
};