//
// JClock.java
// version 961204
// copyright 1996 by bo larsson
// all rights reserved
//
// bugs or feedback to bliss@seagull.net
//

// include all the java packages that are needed.
import java.awt.*;
import java.util.*;
import java.applet.*;

// 
// JClock is a resizeable (through the width and height fields on the
// applet tag) clock that gives the current time on the client machine. 
// It runs a separate thread to update the time.
//

// The time keeping Thread. This is done in a separate class
// for clarity. It is possible to allow the applet class to 
// implement the runnable interface and then run itself as the
// separate thread. That technique is common but not very clear.

class ClockThread extends Thread {
  JClock parentApplet;

  // constructor
  public ClockThread(JClock applet) {
    // store away a reference to the calling applet.
    parentApplet = applet;
  }

  // every thread has a run method. It controls what
  // happens when the thread is started. When this
  // method returns, the thread is no longer running.

  public void run() {

    // a try block to catch the InterruptedException
    // which gets thrown if the thread is interrupted during
    // execution.

    try {
      // Do an infinite loop. It will get interrupted when
      // the thread needs to go away.
      while (true) {
	Date oToday = new Date();
	// call the set date function in the applet.
	parentApplet.setDate(oToday.toString());
	// and repaint the applet.
	parentApplet.repaint();
	// every second. Argument is in milliseconds
	sleep(1000);
      }
    } catch (InterruptedException e) {
      return;
    }
  }
}

//
// The applet class. It creates a ClockThread and runs it.
// The Thread calls the paint routine(indirectly through repaint())
// which updates the display.
//    
public class JClock extends Applet {

  String date;
  ClockThread clockThread;
  boolean showTime;
  boolean showDate;
  Image offScreenImage;

  public void init() {

    // process parameters
    showTime = true;
    showDate = true;
    if (getParameter("NoTime") != null) {
      showTime = false;
    }
    if (getParameter("NoDate") != null) {
      showDate = false;
    }
    // set and initial string.
    date = new String();
    setDate(new String(new Date().toString()));
    // create the off screen image to make
    // painting smoother and reduce flicker.
    offScreenImage = createImage(size().width, size().height);
  }

  // be polite. only start the thread when this
  // applet is started.
  public void start() {
    clockThread = new ClockThread(this);
    clockThread.start();
  }

  // be polite. Stop the thread when this
  // applet is stopped.
  public void stop() {
    if (clockThread != null) {
      clockThread.stop();
      clockThread = null;
    }
  }    
    
  // sets the date string member based on the argument and
  // the two parameters. The string format is in canonical form.
  public void setDate(String newDate) {
    date = "";
    if (showDate && showTime) {
      date = newDate.substring(4, 10);
      date = date.concat(", ");
      date = date.concat(newDate.substring(newDate.length()-4, 
					   newDate.length()));
      date = date.concat(" ");
      date = date.concat(newDate.substring(11,19));
    } else if (showDate) {
      date = newDate.substring(4, 10);
      date = date.concat(", ");
      date = date.concat(newDate.substring(newDate.length()-4, 
					   newDate.length()));
    } else if (showTime) {
      date = date.concat(newDate.substring(11,19));
    }
  }
  
  // paint the bytes retrieved in green on black.
  public void paint(Graphics g) {

    // Create and initial font.
    Font tFont = new Font("Courier", Font.PLAIN, 6);

    // find a good size for the font, by looping
    // through reasonable point sizes. (I have never
    // seen a 400 point font, so it could be argued
    // that it isn't reasonable. But we never should get
    // there). We don't deal with font width so the 
    // sizing is not ideal.
    for (int i = 6; i<400; i++) {
      int fw, fh;
      tFont = new Font("Courier", Font.PLAIN, i);
      fw = g.getFontMetrics(tFont).stringWidth(date);
      fh = g.getFontMetrics(tFont).getHeight();
      // when it finds a font that is bigger in either
      // direction than the window pull back and
      // set it to the last size.
      if (fw > size().width || fh > size().height) {
	tFont = new Font("Courier", Font.PLAIN, i-1);
	break;
      }
    }
      
    g.setFont(tFont);

    int cx, cy;
    // center horizontally.
    cx = (size().width - g.getFontMetrics().stringWidth(date)) /2 ;

    // center vertically. The x y values for drawString refer to
    // the BOTTOM of the font, so compensate by ADDING the height
    // instead of SUBTRACTING it before dividing by 2.
    cy = (size().height + g.getFontMetrics().getHeight() ) /2 ;

    g.setColor(Color.black);
    g.fillRect(0, 0, size().width, size().height);

    g.setColor(Color.green);
    g.drawString(date, cx, cy);
  }

  // avoid flicker.
  public void update(Graphics g) {
    Graphics osg = offScreenImage.getGraphics();
    paint(osg);
    g.drawImage(offScreenImage, 0, 0, this);
  }
}