package net.websoup.wormscan;

/*
*    This file is part of WormScan.
*
*    WormScan is free software; you can redistribute it and/or
*    modify it under the terms of the GNU General Public License
*    as published by the Free Software Foundation; either version 2
*    of the License, or (at your option) any later version.
*
*    This program is distributed in the hope that it will be useful,
*    but WITHOUT ANY WARRANTY; without even the implied warranty of
*    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
*    GNU General Public License for more details.
*
*    You should have received a copy of the GNU General Public License
*    along with this program; if not, write to the Free Software
*    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
*/

import java.util.Stack;

import net.websoup.wormscan.AttackSource;
import net.websoup.wormscan.Program;

/**
 * Gathers AttackSource objects and resolves their hostnames.
 * The pool of AttackSource objects is shared between all Resolver threads.
 * Resolver threads will wait until AttackSource objects appear in the Stack.
 * Threads will exit only when areDone() method is called and no AttackSource objects
 * are waiting for resolution.
 * Copyright:    Copyright (c) 2001-2004 Andriy Rozeluk <arozeluk@websoup.net>
 * @author Andriy Rozeluk
 * @version 1.6.1
 */
public class Resolver extends Thread {
  static int MAX_WAITING = 100;
  private static Stack sourceStack;
  private static boolean done = false;

  /**
   * Initialize our storage for AttackSource objects
   */
  static {
    sourceStack = new Stack();
  }

  /**
   * Signal that no more AttackSource objects will be added. Finish up!
   */
  public static void areDone(){
    done = true;
    synchronized( sourceStack ){
      sourceStack.notifyAll();
    }
  }

  /**
   * Add AttackSource object to the Stack for resolution
   */
  public static void addSource( AttackSource as ){
    if ( !Program.RESOLVE_DNS ) return;
    for (;;){
      synchronized(sourceStack){
        if ( MAX_WAITING <= 0 || sourceStack.size() < MAX_WAITING ){
          sourceStack.push( as );
          if ( Program.OUTPUT_LEVEL > 3 )
            System.out.println( "" + sourceStack.size() + " hostnames waiting to be resolved" );
          sourceStack.notifyAll();
          return;
        }
        else{
          try {
            sourceStack.wait();
          }
          catch( Exception e ){
            //ignore
          }
        }
      }
    }
  }

  /**
   * Go through stack, resolve hostnames of AttackSource objects that appear
   */
  public void run(){
    int lastcount = 0;
    while(!done || lastcount > 0){
      AttackSource as = null;
      synchronized( sourceStack ){
        lastcount = sourceStack.size();
        if ( lastcount > 0 ){
          as = (AttackSource)(sourceStack.pop());
          sourceStack.notifyAll();
        }
      }
      if ( as != null ){
        as.resolveHostnames();
      }
      else {
        synchronized( sourceStack ){
          if (!done ){
            try {
              sourceStack.wait();
            }
            catch( Exception e ){
              //ignore
            }
          }
        }
      }
    }
  }
}