//******************************************************************************
// TimeApp.java:	Applet
//
//******************************************************************************
import java.applet.*;
import java.awt.*;
import java.util.*;
import java.net.*;
import java.io.*;

//==============================================================================
// Main Class for applet TimeApp
//
//==============================================================================
public class TimeApp extends Applet
{

	// PARAMETER SUPPORT:
	//		Parameters allow an HTML author to pass information to the applet;
	// the HTML author specifies them using the <PARAM> tag within the <APPLET>
	// tag.  The following variables are used to store the values of the
	// parameters.
    //--------------------------------------------------------------------------

    // Members for applet parameters
    // <type>       <MemberVar>    = <Default Value>
    //--------------------------------------------------------------------------
	private String m_host = "tick.usno.navy.mil";
	private boolean m_SNTP = true;

    // Parameter names.  To change a name of a parameter, you need only make
	// a single change.  Simply modify the value of the parameter string below.
    //--------------------------------------------------------------------------
	private final String PARAM_host = "host";
	private final String PARAM_SNTP = "SNTP";

	// TimeApp Class Constructor
	//--------------------------------------------------------------------------
	public TimeApp()
	{
		// TODO: Add constructor code here
	}

	// APPLET INFO SUPPORT:
	//		The getAppletInfo() method returns a string describing the applet's
	// author, copyright date, or miscellaneous information.
    //--------------------------------------------------------------------------
	public String getAppletInfo()
	{
		return "Name: TimeApp v0.3\r\n" +
		       "Author: Douglas W. Hogarth (http://www.niceties.com)\r\n" +
		       "Created with Microsoft Visual J++ Version 1.1";
	}

	// PARAMETER SUPPORT
	//		The getParameterInfo() method returns an array of strings describing
	// the parameters understood by this applet.
	//
    // NewApp Parameter Information:
    //  { "Name", "Type", "Description" },
    //--------------------------------------------------------------------------
	public String[][] getParameterInfo()
	{
		String[][] info =
		{
			{ PARAM_host, "String", "server name" },
			{ PARAM_SNTP, "boolean", "true for Simple NTP" },
		};
		return info;		
	}

	// The init() method is called by the AWT when an applet is first loaded or
	// reloaded.  Override this method to perform whatever initialization your
	// applet needs, such as initializing data structures, loading images or
	// fonts, creating frame windows, setting the layout manager, or adding UI
	// components.
    //--------------------------------------------------------------------------
	public void init()
	{
        //String m_host;
		//boolean m_SNTP;
		
		// PARAMETER SUPPORT
		//		The following code retrieves the value of each parameter
		// specified with the <PARAM> tag and stores it in a member
		// variable.
		//----------------------------------------------------------------------
		//String param;

		// host: server name
		//----------------------------------------------------------------------
		//param = getParameter(PARAM_host);
		//if (param != null)
		//	m_host = param;

		// SNTP: true for Simple NTP
		//----------------------------------------------------------------------
		//param = getParameter(PARAM_SNTP);
		//if (param != null)
		//	m_SNTP = Boolean.valueOf(param).booleanValue();

		// If you use a ResourceWizard-generated "control creator" class to
        // arrange controls in your applet, you may want to call its
        // CreateControls() method from within this method. Remove the following
        // call to resize() before adding the call to CreateControls();
        // CreateControls() does its own resizing.
        //----------------------------------------------------------------------
		resize(320, 125);

		// TODO: Place additional initialization code here
	}

	// Place additional applet clean up code here.  destroy() is called when
	// when you applet is terminating and being unloaded.
	//-------------------------------------------------------------------------
	public void destroy()
	{
		// TODO: Place applet cleanup code here
	}

	// TimeApp Paint Handler
	//--------------------------------------------------------------------------
	public void paint(Graphics g)
	{
		Date start, stop, utc, zulu; 
		DatagramSocket s = null; 
		DatagramPacket pkt;
		InetAddress in;
		String m_host;
		byte buf[] = new byte[48];
		int ubuf[] = new int[6];
		boolean m_SNTP=false;//default needed for compiler
		String param;

		//bugbug we should be getting these parameters via init,
		// but Doug is lazy and hasn't learned enough yet
		m_host = getParameter(PARAM_host);
		param = getParameter(PARAM_SNTP);
		if (param != null)
			m_SNTP = Boolean.valueOf(param).booleanValue();

		start = stop = new Date();//we need this to keep compiler from complaining
		try {
			s = new DatagramSocket();
		// hostname "null" returns the default address for the local machine
		in = InetAddress.getByName(m_host);
		if (m_SNTP) {
			pkt = new DatagramPacket(buf, 48, in, 123);//IPPORT_NTP
			buf[0] = 0xB;//client, version 1
			buf[1] = 0;
			buf[2] = 0;
			buf[3] = 0;
		} else
			pkt = new DatagramPacket(buf, 0, in, 37);//IPPORT_TIMESERVER, null packet
		//s.setSoTimeout(3000);//set 3 second timeout to cause java.io.InterruptedIOException
		start = new Date();
		s.send(pkt);
		if (!m_SNTP)//RFC-868
			pkt = new DatagramPacket(buf, 4, in, 37);//IPPORT_TIMESERVER
		s.receive(pkt);
		stop = new Date();
		} catch (SecurityException e) {
		g.drawString("Sorry, security doesn't allow accessing "+m_host, 10, 110);
		g.drawString("(try save-as-file and specifying file://)", 10, 120);
		}
		catch (SocketException se) {
		}
		catch (UnknownHostException uhe) {
		}
		catch (IOException ioe) {
		//bugbug would a timeout get to here?
		}
		//we've got to convert from signed to unsigned
		if (m_SNTP) {
		if (buf[0]>=0)
			ubuf[5]=buf[0];
		else
			ubuf[5]=256+buf[0];
		
		if (((buf[1]<1)||(buf[1]>15)) ||
			((ubuf[5]&0xC0)==0xC0) || //test LI field
			((buf[40]==0)&&(buf[41]==0)&&(buf[42]==0)&&(buf[43]==0)))
			g.drawString("Don't trust any server/UTC info above!", 10, 100);
		
		for (int i=0; i<5; i++) {
		if (buf[40+i]>=0)
			ubuf[i]=buf[40+i];
		else
			ubuf[i]=256+buf[40+i];
		}
		utc = new Date((long)((ubuf[0]*256.0*65536+ubuf[1]*65536+ubuf[2]*256+ubuf[3])-(60.0*60*24*365.2422*70+3974.4))*1000+(long)(ubuf[4]/256+.5));
		//bugbug we didn't use the seconds fraction in a standard way
		} else {//RFC-868
		for (int i=0; i<4; i++) {
		if (buf[i]>=0)
			ubuf[i]=buf[i];
		else
			ubuf[i]=256+buf[i];
		}
		utc = new Date((long)((ubuf[0]*256.0*65536+ubuf[1]*65536+ubuf[2]*256+ubuf[3])-(60.0*60*24*365.2422*70+3974.4))*1000);
		}//RFC-868
		zulu = new Date();
		s.close();
		if ((stop.getTime()-start.getTime())>0) {
			//if m_SNTP bugbug we don't subtract time held by server (typically <.5ms)
			//if m_SNTP bugbug we don't check for >16*1000 (NTP.MAXDISPERSE)
			g.drawString("(round-trip to server took ~"+(stop.getTime()-start.getTime())+" milliseconds)", 10, 85);
			utc.setTime(utc.getTime()+(stop.getTime()-start.getTime())/2);//increase by one-way
		}
		g.drawString("Java(tm) thinks it was "+zulu.toLocaleString()+",", 10, 10);
		g.drawString("when it was really "+utc.toLocaleString(), 10, 25);
		if (!zulu.equals(utc)) {
			if (Math.abs(zulu.getTime()-utc.getTime()) < 2000)
				g.drawString("(your system is correct within a couple seconds).", 10, 40);
			else {
			if (zulu.after(utc))
				g.drawString("(your system was ahead approximately "+(zulu.getTime()-utc.getTime())/1000+" seconds).", 10, 40);
			else
				g.drawString("(your system was behind approximately "+(utc.getTime()-zulu.getTime())/1000+" seconds).", 10, 40);
			g.drawString("Try to correct your system's time and test again using Refresh", 10, 55);
			g.drawString("(or clicking the mouse inside this applet)", 10, 70);
			}
		} else
			g.drawString("(your system has the correct time).", 10, 40);
	}

	//		The start() method is called when the page containing the applet
	// first appears on the screen. The AppletWizard's initial implementation
	// of this method starts execution of the applet's thread.
	//--------------------------------------------------------------------------
	public void start()
	{
		// TODO: Place additional applet start code here
	}
	
	//		The stop() method is called when the page containing the applet is
	// no longer on the screen. The AppletWizard's initial implementation of
	// this method stops execution of the applet's thread.
	//--------------------------------------------------------------------------
	public void stop()
	{
	}


	// MOUSE SUPPORT:
	//		The mouseDown() method is called if the mouse button is pressed
	// while the mouse cursor is over the applet's portion of the screen.
	//--------------------------------------------------------------------------
	public boolean mouseDown(Event evt, int x, int y)
	{
		repaint();
		return true;
	}

	
	// TODO: Place additional applet code here

}