// Fig. 10.3: MessengerServer.java
// This program provides implementation for the
// messenger server.

import java.awt.*;
import java.awt.event.*;
import java.net.*;
import java.io.*;
import javax.swing.*;
import java.util.*;

import org.w3c.dom.*;
import org.xml.sax.*;
import javax.xml.parsers.*;
import com.sun.xml.tree.XmlDocument;

public class MessengerServer extends JFrame {
   private JLabel status;
   private JTextArea display;
   private Vector onlineUsers;
   private DocumentBuilderFactory factory;
   private DocumentBuilder builder;
   private Document users;

   public MessengerServer()
   {
      // create GUI
      super ( "Messenger Server" );

      try {

         // obtain the default parser
         factory = DocumentBuilderFactory.newInstance();

         // get DocumentBuilder
         builder = factory.newDocumentBuilder();
      } 
      catch ( ParserConfigurationException pce ) {
         pce.printStackTrace();
      }

      Container c = getContentPane();

      status = new JLabel( "Status" );
      c.add( status, BorderLayout.NORTH );

      display = new JTextArea();
      display.setLineWrap( true );
      display.setEditable( false );
      c.add( new JScrollPane( display ), BorderLayout.CENTER );
      display.append( "Server waiting for connections\n" );

      setSize( 300, 300 );
      show();

      // initialize variables
      onlineUsers = new Vector();
      users = initUsers();
   }

   public void runServer()
   {
      ServerSocket server;

      try {
         // create a ServerSocket
         server = new ServerSocket( 5000, 100 );

         // wait for connections
         while ( true ) {
            Socket clientSocket = server.accept();

            display.append( "\nConnection received from: " +
               clientSocket.getInetAddress().getHostName() );

            UserThread newUser = 
               new UserThread( clientSocket, this );

            newUser.start();
         }
      } 
      catch ( IOException e ) {
         e.printStackTrace();
         System.exit( 1 );
      }
   }

   private Document initUsers()
   {
      // initialize users xml document with root element users
      Document init = builder.newDocument();

      init.appendChild( init.createElement( "users" ) );
      return init;
   }

   public void updateGUI( String s )
   {
      display.append( "\n" + s );
   }

   public Document getUsers()
   {
      return users;
   }

   public void addUser( UserThread newUserThread ) 
   {
      // get new user's name
      String userName = newUserThread.getUsername();

      updateGUI( "Received new user: " + userName );

      // notify all users of user's login
      updateUsers( userName, "login" );

      // add new user element to Document users
      Element usersRoot = users.getDocumentElement();
      Element newUser = users.createElement( "user" );

      newUser.appendChild( 
         users.createTextNode( userName ) );
      usersRoot.appendChild( newUser );

      updateGUI( "Added user: " + userName );

      // add to Vector onlineUsers
      onlineUsers.addElement( newUserThread );
   }

   public void sendMessage( Document message )
   {
      // transfer message to specified receiver 
      Element root = message.getDocumentElement();
      String from = root.getAttribute( "from" );
      String to = root.getAttribute( "to" );
      int index = findUserIndex( to );

      updateGUI( "Received message To: " + to + ",  From: " + from );

      // send message to corresponding user
      UserThread receiver = 
         ( UserThread ) onlineUsers.elementAt( index );
      receiver.send( message );
      updateGUI( "Sent message To: " + to +
         ",  From: " + from );
   }

   public void updateUsers( String userName, String type )
   {
      // create xml update document
      Document doc = builder.newDocument();
      Element root = doc.createElement( "update" );
      Element userElt = doc.createElement( "user" );

      doc.appendChild( root );
      root.setAttribute( "type", type );
      root.appendChild( userElt );
      userElt.appendChild( doc.createTextNode( userName ) );

      // send to all users
      for ( int i = 0; i < onlineUsers.size(); i++ ) {
         UserThread receiver = 
            ( UserThread ) onlineUsers.elementAt( i );
         receiver.send( doc );
      }

      updateGUI( "Notified online users of " + 
         userName + "'s " + type );
   }

   public int findUserIndex( String userName )
   {
      // find index of specified UserThread in Vector onlineUsers
      // return -1 if no corresponding UserThread is found
      for ( int i = 0; i < onlineUsers.size(); i++ ) {
         UserThread current = 
            ( UserThread ) onlineUsers.elementAt( i );

         if ( current.getUsername().equals( userName ) ) 
            return i;
      }

      return -1;
   }

   public void removeUser( String userName )
   {
      // remove user from Vector onlineUsers
      int index = findUserIndex( userName );

      onlineUsers.removeElementAt( index );

      // remove this user's element from Document users
      NodeList userElements =
         users.getDocumentElement().getElementsByTagName(
         "user" );

      for ( int i = 0; i < userElements.getLength(); i++ ) {
         String str = 
            userElements.item( i ).getFirstChild().getNodeValue();

         if ( str.equals( userName ) )
            users.getDocumentElement().removeChild( 
               userElements.item( i ) );
            
      }

      updateGUI( "Removed user: " + userName );

      // update all users of user's logout
      updateUsers( userName, "logout" );
   }

   public static void main( String args[] )
   {
      MessengerServer ms = new MessengerServer();

      ms.addWindowListener( 
         new WindowAdapter() {
            public void windowClosing( WindowEvent e ) {
               System.exit( 0 );
            }
         } 
      );

      ms.runServer();
   }
}
/*
 **************************************************************************
 * (C) Copyright 2001 by Deitel & Associates, Inc. and Prentice Hall.     *
 * All Rights Reserved.                                                   *
 *                                                                        *
 * DISCLAIMER: The authors and publisher of this book have used their     *
 * best efforts in preparing the book. These efforts include the          *
 * development, research, and testing of the theories and programs        *
 * to determine their effectiveness. The authors and publisher make       *
 * no warranty of any kind, expressed or implied, with regard to these    *
 * programs or to the documentation contained in these books. The authors *
 * and publisher shall not be liable in any event for incidental or       *
 * consequential damages in connection with, or arising out of, the       *
 * furnishing, performance, or use of these programs.                     *
 **************************************************************************
*/