import java.net.*;
import java.io.*;
import java.util.*;

class ClientInfo {
   String partner, ipaddress;
   int port;

   public ClientInfo (String partner, String ip, int port) {
      this.partner = partner;
      this.ipaddress = ip;
      this.port = port;
   }
}

class Checker extends Thread {
   Doit server;
   boolean new_buddies = true, new_buddies_temp = true;

   public Checker (Doit server) { this.server = server; }

   boolean isAlive (String ipaddress, int port) {
      try {
	  Socket socket = new Socket(ipaddress, port);
	  (socket.getOutputStream()).write((new Byte((byte)10)).byteValue());
	  if (new_buddies) {
	     (socket.getOutputStream()).write((new Byte((byte)85)).byteValue());
	     (socket.getOutputStream()).write((new Byte((byte)10)).byteValue());
	  } else
	     (socket.getOutputStream()).write((new Byte((byte)10)).byteValue());
	  socket.close();
	  return true;
      } catch(Exception ex) { }
      return false;
   }

   public void run () {
      while (true) {
	 try { sleep (1000); } catch (Exception e) {}
	 new_buddies = new_buddies_temp;
	 new_buddies_temp = false;
	 Enumeration elements = server.hash.elements();
	 while (elements.hasMoreElements()) {
	    ClientInfo ci = (ClientInfo)elements.nextElement();
	    String prt = String.valueOf(ci.port);
	    if (!isAlive(ci.ipaddress, ci.port)) {
	       server.hash.remove(ci.partner);
	       System.out.println("Server:"+ci.partner+" removed");
	       new_buddies_temp = true;
	    }
	 }
	 new_buddies = false;
      }
   }
}

class Register extends Thread {
   Doit server;

   public Register (Doit server) {  this.server = server;  }

   public void run () {
      String msg;
      try {
         ServerSocket socket = new ServerSocket(8081);
         while (true) {
            Socket cli = socket.accept();
            String ip = cli.getInetAddress().toString();
            System.out.println("Receiving from: "+ip);
            BufferedReader in = 
               new BufferedReader(new InputStreamReader(cli.getInputStream()));
            DataOutputStream out = new DataOutputStream(cli.getOutputStream());
            try {
               msg = in.readLine();
	       System.out.println("Register: from:"+ip+" msg:"+msg);
               if (msg != null) {
		  StringTokenizer t = new StringTokenizer(msg," ");
		  String partner = t.nextToken();
		  int port = Integer.parseInt(t.nextToken());
                  String pip = ip.substring(ip.indexOf('/')+1);
                  System.out.println(msg+" registered on machine "+pip);
                  out.writeBytes(msg+" registered on machine "+pip+"\n");
		  ClientInfo ci = new ClientInfo(partner, pip, port);
                  server.hash.put(partner, ci);
		  server.checker.new_buddies_temp = true;
               }
            } catch (Exception e1) {
               System.out.println("Connection closed ("+e1.toString()+")\n");
            }
	    out.close();
	    in.close();
	    cli.close();
         }
      }
      catch (Exception e) { }
   }
}

class Message extends Thread {
   Doit server;
   
   public Message (Doit server) {
      this.server = server;
   }

   public void run () {
      String msg, header;
      try {
         ServerSocket socket = new ServerSocket(8080);
         while (true) {
            Socket cli = socket.accept();
            String ip = cli.getInetAddress().toString();
            System.out.println("Receiving from: "+ip);
            BufferedReader in = 
               new BufferedReader(new InputStreamReader(cli.getInputStream()));
	    DataOutputStream out = 
	       new DataOutputStream(cli.getOutputStream());
            try {
               header = in.readLine();
	       System.out.println("Message: from:"+ip+" header:"+header);
	       StringTokenizer t = new StringTokenizer(header," ");
	       String orig = t.nextToken();
	       String dest = t.nextToken();
	       ClientInfo ci = (ClientInfo)server.hash.get(dest);
               String srvip = ci.ipaddress;
	       if (srvip != null) {
		  System.out.println("Sending to: "+srvip);
		  Socket srv = new Socket(srvip, ci.port);
		  BufferedReader srvin = 
		     new BufferedReader(
			 new InputStreamReader(srv.getInputStream()));
		  DataOutputStream srvout = 
		     new DataOutputStream(srv.getOutputStream());
		  if (header != null) {
		     srvout.writeBytes(orig+"\n");
		     String text;
		     srvout.writeBytes(text=in.readLine()+"\n");
		     System.out.println("Message: from:"+ip+" msg:"+text);
		  }
		  srvin.close();
		  srvout.close();
		  out.writeBytes("ok\n");
	       } else {
		  System.out.println("User "+dest+" not found by "+orig);
		  out.writeBytes("bad\n");
	       }
	       out.close();
            } catch (Exception e1) {
               System.out.println("Connection closed");
            }
	    in.close();
	    cli.close();
         }
      }
      catch (Exception e) { }
   }
}

class ShowAll extends Thread {
   Doit server;
   
   public ShowAll (Doit server) {  this.server = server;  }

   public void run () {
      String msg;
      try {
         ServerSocket socket = new ServerSocket(8082);
         while (true) {
            Socket cli = socket.accept();
            String ip = cli.getInetAddress().toString();
            System.out.println("ShowAll: receiving null from: "+ip);
            BufferedReader in = 
               new BufferedReader(new InputStreamReader(cli.getInputStream()));
            DataOutputStream out = new DataOutputStream(cli.getOutputStream());
            try {
	       String outstr = "";
	       Enumeration elements = server.hash.elements();
	       while (elements.hasMoreElements()) {
		  ClientInfo ci = (ClientInfo)elements.nextElement();
		  String prt = String.valueOf(ci.port);
		  outstr += ci.partner+" "+ci.ipaddress+" "+prt+"|";
	       }
	       out.writeBytes(outstr+"\n");
            } catch (Exception e1) {
               System.out.println("Connection closed");
            }
         }
      }
      catch (Exception e) { }
   }
}

class RemoveFromDB extends Thread {
   Doit server;
   
   public RemoveFromDB (Doit server) {  this.server = server;  }

   public void run () {
      String msg;
      try {
         ServerSocket socket = new ServerSocket(8083);
         while (true) {
            Socket cli = socket.accept();
            String ip = cli.getInetAddress().toString();
            System.out.println("RemoveFromDB: connection: "+ip);
            BufferedReader in = 
               new BufferedReader(new InputStreamReader(cli.getInputStream()));
            DataOutputStream out = new DataOutputStream(cli.getOutputStream());
	    String toremove = in.readLine();
	    System.out.println("RemoveFromDB: from:"+ip+" msg:"+toremove);
            try {
	       ClientInfo object;
	       if ((object = (ClientInfo)server.hash.get(toremove)) != null) {
		  String ipaddress = ip.substring(ip.indexOf('/')+1);
		  if (object.ipaddress.equals(ipaddress)) {
		     server.hash.remove((Object)toremove);
		     out.writeBytes("Client "+toremove+" removed from DB\n");
		     server.checker.new_buddies_temp = true;
		  } else {
		     out.writeBytes("Client name does not match machine ip\n");
		  }
	       } else {
		  out.writeBytes("Client not in the data base\n");
	       }
            } catch (Exception e1) {
               System.out.println("Connection closed");
            }
	    in.close();
	    out.close();
	    cli.close();
         }
      }
      catch (Exception e) { }
   }
}

class Doit {
   Checker checker;
   Hashtable hash;

   Doit () { 
      hash = new Hashtable();
      Register register = new Register(this);
      Message message = new Message(this);
      ShowAll showall = new ShowAll(this);
      RemoveFromDB remover = new RemoveFromDB(this);
      checker = new Checker(this);
      register.start();
      message.start();
      showall.start();
      remover.start();
      checker.start();
   }
}

public class Server {
   public static void main (String arg[]) {  new Doit();  }
}