import java.awt.*;
import java.util.*;

// written by Joseph Silverman (yossie@mail.blacksteel.com), last update 06/05/97

public class Odometer extends Canvas implements Runnable {

	protected Image osg;
	protected Thread t;
	
	protected int digits;
	protected int cycle = 50;
	protected int cellw, cellh;
	
	protected long history[][] = new long[5][2];
	protected int h = 0;
	
	public Odometer(long val, int digits) {
		this.digits = digits;
		history[0][0] = val * 1000;
		history[0][1] = (new Date()).getTime();
		for (int i = 1; i < 5; i++ ) {
			history[i][0] = history[i][0];
			history[i][1] = history[i][1];
		}
		t = new Thread(this);
		t.setPriority(1);
		t.start();
	}

	public Odometer() {
		this(0,8);
	}
	
	protected void measure() {
		FontMetrics fm = getFontMetrics(getFont());
		if (fm == null) return;
		cellw = 0;
		for (int i = 0; i < 10; i++) {
			int w = fm.stringWidth("" + i);
			if (cellw < w) cellw = w;
		}
		cellw += 5; // 2 on each side and room for enclosing box!
		cellh = fm.getHeight();
	}
	
	public void setFont(Font f) {
		super.setFont(f);
		measure();
	}
	
	public void setForeground(Color c) {
		super.setForeground(c);
		repaint();
	}
	
	public synchronized void setVal(long val) {
		h = (h + 1) % 5;
		history[h][0] = val * 1000;
		history[h][1] = (new Date()).getTime();
	}
	
	public void addNotify() {
		super.addNotify();
		measure();
	}
	
	public Dimension minimumSize() {
		return new Dimension(cellw*digits, cellh*4/3);
	}
	
	public Dimension preferredSize() {
		return minimumSize();
	}
	
	public void run() {
		while (true) {
			repaint();
			try { Thread.sleep(cycle); } catch (InterruptedException e) {}
		}
	}
	
	public void paint(Graphics g) {
		update(g);
	}
	public void update(Graphics g) {
		Dimension d = size();
		if (d.width == 0 || d.height == 0) return;
		if (osg == null) osg = createImage(d.width, d.height);

		Graphics og = osg.getGraphics();
		og.setColor(this.getBackground()); 
		og.fillRect(0, 0, d.width, d.height);
		og.setColor(this.getForeground());
		og.drawRect(0, 0, d.width, d.height);
		og.setFont(this.getFont());
		for (int i = 1; i < digits; i++)
			og.drawLine(cellw * i, 0, cellw * i, d.height);
		
		long currval = history[h][0] + (history[h][0] - history[(h + 6) % 5][0]) *
				((new Date()).getTime() - history[h][1]) /
				(history[h][1] - history[(h + 6) % 5][1]);
		long decimal = currval / 1000;
		int fraction = (int) (currval % 1000), pixels = (cellh * fraction) / 1000;
		boolean flag = (fraction != 0);
		for (int i = digits - 1; i >= 0; i--) {
			int digit = (int) (decimal % 10);
			decimal /= 10;
			if (flag) {
				og.drawString("" + digit, cellw * i + 2, cellh - pixels);
				og.drawString("" + ((digit + 1) % 10), cellw * i + 2, cellh * 2 - pixels);
			} else og.drawString("" + digit, cellw * i + 2, cellh);
			flag = flag && (digit == 9);
		}
		g.drawImage(osg, 0, 0, this);
	}
}