// Copyright © 2002
// John M. Thompson
// Boulder, Colorado  USA
// jt@iwaytechnology.com
// http://www.iwaytechnology.com
// 
// A limited right to copy this page for 
// individual (non-commercial) educational 
// use only is hereby granted. 

import iwaypublishing.util.IMsgPortManager;

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

/**********************************************************************
 * A server app that requires an orderly shutdown feature.
 * <p>
 * 
 * Usage (Windows): 
 * 
 *    Start first Server app (in cmd wdw 1): 
 * 
 *       > java -classpath . myserver 1789 sample.txt
 * 
 *    Start second Server app w/stop (in cmd wdw 2):
 *  
 *       > java -classpath . myserver 1789 stop
 * 
 */
public class myserver
{
   /** 
    * Port number for termination communication.
    * 'static' implies we'll have one instance of 
    * this server per JVM.
    */
   private static int msgPort_ = 0;
   
   /** 
    * IMsgPortManager portManager_ will listen for a second 
    * instance of myserver attempting to notify us to 
    * shutdown in orderly fashion.  This communication is
    * achieved with IMsgPortManager.sendTerminate().
    */
   private static IMsgPortManager portManager_ = null;
   
   /** Where 'important work' is 'documented' */
   private static PrintWriter out_ = null;
   
   // Optional upper bound on processing iterations
   // (demonstration purposes only, not required).
   private static final int INTERNAL_MAX_COUNT = 100000;
   
   /*******************************************************************
    * @param args String array of command line args - first one is 
    * port number to monitor or terminate with, and if followed by
    * 'stop' (no quotes), attempt to terminate running server. 
    */
   public static void main( String[] args )
      throws IOException, SocketException, InterruptedException
   {
      // See processArgs() for reasons it may return false
      if( ! processArgs( args ) ) return;
      
      // Start up a message port manager
      startupPortManager();
      
      // Do work, waiting for termination request; 
      // when returns, shutdown
      go();
      
      shutdownPortManager();
      
      shutdownPrintWriter();
      
      // Hold up app for a response
      byte[] response = new byte[ 256 ];
      System.out.println( "\nmyserver.main() all done. Press <CR>." );
      System.in.read( response );
   
   }
   
   /*******************************************************************
    * processArgs - Handle comand line args
    * 
    * @param args String array of cmd line args.
    * @return boolean true => continue, false => exit
    */
   private static boolean processArgs( String[] args )
   {
      if( args.length < 2 ) {
         System.out.println( "Usage: myserver <port> ( stop | <output_filename> )" );
         return false;
      }
      
      try {
         msgPort_ = Integer.parseInt( args[ 0 ] );
         
         // Is second arg Stop msg or file name?
         if( args[ 1 ].equalsIgnoreCase( "stop" ) ) {
                  
            // DEBUG
            System.out.println( "Attempting to stop running instance -" );
               
            if( IMsgPortManager.sendTerminate( msgPort_ ) ) {
               // DEBUG
               System.out.println( " - Success." );
            } else {
               // DEBUG
               System.out.println( " - Failure." );
            } 
            return false;
               
         } else {
            // Get file name arg
            out_ = 
              new PrintWriter( new BufferedWriter( new FileWriter( args[ 1 ] ) ) );
         }
      }
      catch( Exception e ) { 
         System.out.println( "Usage: myserver <port> ( stop | <output_filename> )" );
         return false; 
      }
      return true;
   }
   
   /* ************************************************************** */
   private static void shutdownPrintWriter()
      throws IOException, SocketException, InterruptedException
   {
      out_.flush();
      out_.close();
   }

   /* ************************************************************** */
   private static void startupPortManager()
      throws IOException, SocketException
   {
      portManager_ = new IMsgPortManager( msgPort_ );
      portManager_.start();
   }      
   
   /* ************************************************************** */
   private static void shutdownPortManager()
      throws IOException, SocketException, InterruptedException
   {
      portManager_.kill();
      portManager_.join();
   }

   /* ****************************************************************/
   private static void go()
      throws InterruptedException
   {
      int count = 0;
      
      int workUnit = 0;

      while( count++ < INTERNAL_MAX_COUNT ) {
         
         // Begin important, uniterruptable work.       
         out_.println( "Started work unit " + ++workUnit );

         // Do important work (sleep to simulate passage of time)
         
         try {
            Thread.sleep( 3000 ); // milliseconds
         }
         catch( InterruptedException e ){ return; }
         
         out_.println( "Finished work unit " + workUnit );
         
         // Check for termination request from a second cmd-line 
         // instance. This should be done AT LEAST once every ten
         // seconds, if possible, at a "good time" for shutdown 
         // (ie, no possible loss of data)
         System.out.println( "In myserver.go(), checking for termination request." );
         
         if( portManager_.isTerminate() ) {
            System.out.println( "\nIn myserver.go(), handling termination request after " + workUnit + " units of work." );
            return;
         }
      }
   }
   
}