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

//--> 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 security logging UI used by system
 * operations staff.
 */
public class LogMonitor extends JFrame {
    private JTextArea _textArea;  // Multiline area for log messages

    /** Constructor */
    public LogMonitor() {
        super("Security Log");

        //--> A quick and easy way to have a scrolling text display
        //--> is to use a JTextArea inside a JScrollPane.
        _textArea = new JTextArea(10,40);
        _textArea.setEditable(false);

        //--> Note that most GUIs do most of their work by
        //--> managing a collection of JDK class objects.
        JScrollPane areaScrollPane = new JScrollPane(_textArea);
        areaScrollPane.setVerticalScrollBarPolicy(
        		JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);

        this.getContentPane().add(areaScrollPane);
        this.pack();
    }

    /**
     * Logs a message to the logging UI.
     * @param msg a non-null string to be logged. 
     */
    public void log(String msg) {
        //assert (msg != null);

        this.show(); // Just in case it was hidden.
        //--> A Date with no arguments gives the current timestamp.
        Date d = new Date();
        _textArea.append(d.toString() + ": "+msg + "\n");
    }
};