/*
 * Copyright (C) The Apache Software Foundation. All rights reserved.
 *
 * This software is published under the terms of the Apache Software
 * License version 1.1, a copy of which has been included with this
 * distribution in the LICENSE.APL file.  */

package examples;

import java.rmi.Remote;
import java.rmi.server.UnicastRemoteObject;
import java.rmi.RemoteException;
import java.rmi.Naming;
import java.util.Vector;


import org.apache.log4j.Category;
import org.apache.log4j.NDC;
import org.apache.log4j.PropertyConfigurator;

/**
   A simple {@link NumberCruncher} implementation that logs its
   progress when factoring numbers. The purpose of the whole exercise
   is to show the use of nested diagnostic contexts in order to
   distinguish the log output from different client requests.

   <pre>
   <b>Usage:</b> java org.apache.log4j.examples.NumberCruncherServer <em>configFile</em>
    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;where <em>configFile</em> is a log4j configuration file.
   </pre>

   We supply a simple config file <a href=doc-files/factor.lcf>factor.lcf</a>
   for directing log output to the file <code>factor.log</code>.

   <p>Try it yourself by starting a <code>NumberCruncherServer</code>
   and make queries from multiple {@link NumberCruncherClient
   NumberCruncherClients} to factor numbers.

   
   <p><b><a href="doc-files/factor.html">Sample output</a></b> shows the log
   output when two clients connect to the server near simultaneously.
      
   <p>See <a href=doc-files/NumberCruncherServer.java>source</a> code
   of <code>NumberCruncherServer</code> for more details.

   <p>Note that class files for the example code is not included in
   any of the distributed log4j jar files. You will have to add the
   directory <code>/dir-where-you-unpacked-log4j/classes</code> to
   your classpath before trying out the examples.

   
 */
public class NumberCruncherServer extends UnicastRemoteObject
                                  implements  NumberCruncher {


  static Category cat = Category.getInstance(
					NumberCruncherServer.class.getName());

  public
  NumberCruncherServer() throws RemoteException {
  }
  
  public
  int[] factor(int number) throws RemoteException {

    // The client's host is an important source of information.
    try {
      NDC.push(this.getClientHost());
    }
    catch(java.rmi.server.ServerNotActiveException e) {
      // we are being called from same VM
      NDC.push("localhost");
    }

    // The information contained within the request is another source of
    // distinctive information. It might reveal the users name, date of request,
    // request ID etc. In servlet type environments, much information is
    // contained in cookies.
    NDC.push(String.valueOf(number));    

    cat.info("Beginning to factor.");
    if(number <= 0) {
      throw new IllegalArgumentException(number+" is not a positive integer.");
    }
    else if(number == 1)
       return new int[] {1};
    
    Vector factors = new Vector();
    int n = number;

    for(int i = 2; (i <= n) && (i*i <= number); i++) {
      // It is bad practice to place log requests within tight loops.
      // It is done here to show interleaved log output from
      // different requests. 
      cat.debug("Trying to see if " + i + " is a factor.");

      if((n % i) == 0) {
	cat.info("Found factor "+i);
	factors.addElement(new Integer(i));
	do {
	  n /= i;
	} while((n % i) == 0);
      }
      // Placing artificial delays in tight-loops will also lead to sub-optimal
      // resuts. :-)
      delay(100);
    }

    if(n != 1) {
      cat.info("Found factor "+n);
      factors.addElement(new Integer(n));
    }
    
    int len = factors.size();
    
    int[] result = new int[len];
    for(int i = 0; i < len; i++) {
      result[i] = ((Integer) factors.elementAt(i)).intValue();
    }

    // Before leaving a thread we call NDC.remove. This deletes the reference
    // to the thread in the internal hash table. Version 0.8.5 introduces a
    // a lazy removal mechanism in case you forget to call remove when
    // exiting a thread. See the java documentation in NDC.remove for further
    // details.
    NDC.remove();
    
    return result;
  }

  static
  void usage(String msg) {
    System.err.println(msg);
    System.err.println(
     "Usage: java org.apache.log4j.examples.NumberCruncherServer configFile\n" +
     "   where configFile is a log4j configuration file.");
    System.exit(1);
  }

  public static
  void delay(int millis) {
    try{Thread.currentThread().sleep(millis);}
    catch(InterruptedException e) {}
  }
  
  public static void main(String[] args) {
    if(args.length != 1) 
      usage("Wrong number of arguments.");
    
    NumberCruncherServer ncs;
    PropertyConfigurator.configure(args[0]);
    try {
      ncs = new NumberCruncherServer();
      Naming.rebind("Factor", ncs);
      cat.info("NumberCruncherServer bound and ready to serve.");
    }
    catch(Exception e) {
      cat.error("Could not bind NumberCruncherServer.", e);
      return;
    }
    NumberCruncherClient.loop(ncs);          
  }
}
