// Propossed solution for Assignment#3: Wake-On-LAN Server - 5662.blogspot.com
import java.io.*;
import java.net.*;
import java.util.*;

class WolServer extends Thread {
static Hashtable<String,Date> list = new Hashtable<String,Date>();
static InetAddress ip = null;

	public static void wakeOnLan(String mac, InetAddress ip) {
		DatagramSocket ds1 = null;
		try { ds1 = new DatagramSocket(); } catch(SocketException e) {System.err.println("Socket error"); }
		String[] addr=mac.split(":");
		byte[] buffer = new byte[102];
		for(int i=0;i<6; i++) {
			buffer[i]=-1; // -1 == 0xff
			for(int j=0;j<16; j++) buffer[(j+1)*6+i]=(byte) ((Character.digit(addr[i].charAt(0), 16) << 4)
                             + Character.digit(addr[i].charAt(1), 16));
		}
		DatagramPacket dp = new DatagramPacket(buffer,102,ip,7);
		try { ds1.send(dp); } catch (IOException e) {System.err.println("Cannot send magic packet"); }
		// not asked for: list.remove(mac);
	}

	public void run() { //check if it is the time
		while(true) {
			Date now = new Date();
			for(String key : list.keySet()) if(list.get(key).toString().equals(now.toString()))  wakeOnLan(key, ip);
			try {sleep(1000); } catch (InterruptedException e) {}
			}
		}

	public static void main(String s[]) throws SocketException, IOException{
		DatagramSocket ds = new DatagramSocket(2323);
		byte[] buffer = new byte[1024];
		Thread t = new WolServer();
		t.start();
		while(true) { // it is a server!!
		DatagramPacket dp = new DatagramPacket(buffer,buffer.length);
		ds.receive(dp);
		if(dp.getLength()<10) for(String key : list.keySet()) System.out.println(key + " " + list.get(key));
		else { // add to the list
				String line = new String(dp.getData(),0,dp.getLength()-1); // remove new-line char
				if(line.matches("([0-9a-f]{2}:){5}[0-9a-f]{2}\\s\\d+.\\d+.\\d+.\\d+\\s\\d+")) try { // correct format, then Ok
					Scanner sc = new Scanner(line);
					String mac = sc.next();
					ip = InetAddress.getByName(sc.next());
					long time = sc.nextLong();
					if(time==0) list.remove(mac);
					else list.put(mac, new Date( time*1000 + System.currentTimeMillis() ));
					dp.setData("Ok\n".getBytes());
					ds.send(dp);
				} catch(Exception e) { dp.setData("Error\n".getBytes()); ds.send(dp); } // Bad parameters error
				else {dp.setData("Error\n".getBytes()); ds.send(dp); } // Bad format => Error
			}
		}
	}
}