/*
    * Copyright (c) 2002-2022, City of Paris
    * All rights reserved.
    *
    * Redistribution and use in source and binary forms, with or without
    * modification, are permitted provided that the following conditions
    * are met:
    *
    *  1. Redistributions of source code must retain the above copyright notice
   *     and the following disclaimer.
   *
   *  2. Redistributions in binary form must reproduce the above copyright notice
   *     and the following disclaimer in the documentation and/or other materials
   *     provided with the distribution.
   *
   *  3. Neither the name of 'Mairie de Paris' nor 'Lutece' nor the names of its
   *     contributors may be used to endorse or promote products derived from
   *     this software without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
   * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE
   * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
   * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
   * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
   * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
   * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   * POSSIBILITY OF SUCH DAMAGE.
   *
   * License 1.0
   */
  package fr.paris.lutece.portal.service.daemon;
  
  import fr.paris.lutece.portal.service.plugin.Plugin;
  import fr.paris.lutece.portal.service.util.AppPropertiesService;
  
  import java.util.ArrayDeque;
  import java.util.ArrayList;
  import java.util.Deque;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  import java.util.Map.Entry;
  
  import org.apache.commons.collections.CollectionUtils;
  
  /**
   * Daemon that manage a pool of threads to launch runnables.
   */
  public class ThreadLauncherDaemon extends Daemon
  {
      private static final String THREAD_LAUNCHER_DAEMON_ID = "threadLauncherDaemon";
  
      /**
       * Runnable wrapper to signal the daemon on processing end
       */
      private class RunnableWrapper implements Runnable
      {
          private final Runnable _wrapped;
  
          /**
           * Constructor
           * 
           * @param wrapped
           *            the wrapped Runnable
           */
          public RunnableWrapper( Runnable wrapped )
          {
              _wrapped = wrapped;
          }
  
          @Override
          public void run( )
          {
              try
              {
                  _wrapped.run( );
              }
              finally
              {
                  // will clean up the dead thread
                  // and permit execution of blocked tasks
                  AppDaemonService.signalDaemon( THREAD_LAUNCHER_DAEMON_ID );
              }
          }
  
      }
  
      private static final String PROPERTY_MAX_NUMBER_THREAD = "daemon.threadLauncherDaemon.maxNumberOfThread";
      private static Deque<RunnableQueueItem> _stackItems = new ArrayDeque<>( );
      private Map<String, Thread> _mapThreadByKey = new HashMap<>( );
      private List<Thread> _listThread = new ArrayList<>( );
  
      /**
       * {@inheritDoc}
       */
      @Override
     public void run( )
     {
         int nMaxNumberThread = AppPropertiesService.getPropertyInt( PROPERTY_MAX_NUMBER_THREAD, 5 );
 
         // We remove dead threads from running thread collections
         String logs = removeDeadThreads( );
 
         RunnableQueueItem item = null;
         int nCurrentNumberRunningThreads = _mapThreadByKey.size( ) + _listThread.size( );
 
         List<RunnableQueueItem> listLockedItems = new ArrayList<>( );
 
         while ( ( nCurrentNumberRunningThreads < nMaxNumberThread ) && ( ( item = popItemFromQueue( ) ) != null ) )
         {
             String key = item.computeKey( );
             // If the item has a key, then we must make sure that another thread with the same key and plugin is not running
             if ( key != null )
             {
                 Thread thread = _mapThreadByKey.get( key );
 
                 if ( thread != null )
                 {
                     if ( thread.isAlive( ) )
                     {
                         // The thread is already running. We declare this item as locked for this run of the daemon.
                         listLockedItems.add( item );
                     }
                     else
                     {
                         // Dead threads are removed from collections at the beginning of the run of the daemon
                         // We still check again that the thread is alive just in case it died during the run
                         thread = getThread( item );
                         _mapThreadByKey.put( key, thread );
 
                         // We do not increase the number of running threads, because we removed and add one
                     }
                 }
                 else
                 {
                     thread = getThread( item );
                     _mapThreadByKey.put( key, thread );
                     nCurrentNumberRunningThreads++;
                 }
             }
             else
             {
                 // If it has no key, or if the plugin has not been set, we create a thread in the keyless collection
                 Thread thread = getThread( item );
                 _mapThreadByKey.put( key, thread );
                 nCurrentNumberRunningThreads++;
             }
         }
 
         // We replace in the queue items that was locked
         listLockedItems.stream( ).forEach( ThreadLauncherDaemon::addItemToQueue );
 
         // If the maximum number of running threads has been reached, we end this run
         if ( nCurrentNumberRunningThreads >= nMaxNumberThread )
         {
             setLastRunLogs( logs + "Every threads are running. Daemon execution ending." );
             return;
         }
 
         setLastRunLogs( logs + "There is no more runnable to launch." );
     }
 
     private Thread getThread( RunnableQueueItem item )
     {
         Thread thread = new Thread( new RunnableWrapper( item.getRunnable( ) ) );
         thread.start( );
         return thread;
     }
 
     private String removeDeadThreads( )
     {
         List<String> listDeadThreadKeys = new ArrayList<>( );
         for ( Entry<String, Thread> threadEntry : _mapThreadByKey.entrySet( ) )
         {
             if ( !threadEntry.getValue( ).isAlive( ) )
             {
                 listDeadThreadKeys.add( threadEntry.getKey( ) );
             }
         }
 
         for ( String strThreadKey : listDeadThreadKeys )
         {
             _mapThreadByKey.remove( strThreadKey );
         }
 
         List<Thread> listDeadThreads = new ArrayList<>( );
 
         for ( Thread thread : _listThread )
         {
             if ( !thread.isAlive( ) )
             {
                 listDeadThreads.add( thread );
             }
         }
 
         String logs = "";
         if ( !listDeadThreads.isEmpty( ) )
         {
             logs = "Releasing " + listDeadThreads.size( ) + " dead threads.\n";
         }
         for ( Thread thread : listDeadThreads )
         {
             _listThread.remove( thread );
         }
         return logs;
     }
 
     /**
      * Add a runnable to the launch queue. It will be launched as soon as a thread is available.
      * 
      * @param runnable
      *            The runnable to execute
      * @param strKey
      *            The key of the runnable. Runnables of a given plugin are ensured that they will not be executed at the same time if they have the same key.
      * @param plugin
      *            The plugin the runnable is associated with
      */
     public static void addItemToQueue( Runnable runnable, String strKey, Plugin plugin )
     {
         RunnableQueueItemunnableQueueItem.html#RunnableQueueItem">RunnableQueueItem runnableItem = new RunnableQueueItem( runnable, strKey, plugin );
 
         synchronized( ThreadLauncherDaemon.class )
         {
             _stackItems.addLast( runnableItem );
         }
 
         AppDaemonService.signalDaemon( THREAD_LAUNCHER_DAEMON_ID );
     }
 
     /**
      * Add a runnable item to the queue
      * 
      * @param runnableItem
      *            The runnable item to add to the queue
      */
     private static synchronized void addItemToQueue( RunnableQueueItem runnableItem )
     {
         _stackItems.addLast( runnableItem );
     }
 
     /**
      * Pop the first item of the queue. The item is removed from the queue.
      * 
      * @return The first item of the queue, or null if the queue is empty
      */
     private static synchronized RunnableQueueItem popItemFromQueue( )
     {
         if ( CollectionUtils.isEmpty( _stackItems ) )
         {
             return null;
         }
 
         return _stackItems.pop( );
     }
 
     /**
      * Count the number of items in the queue.
      * 
      * @return The current number of items in the queue
      */
     public static synchronized Integer countItemsInQueue( )
     {
         return _stackItems.size( );
     }
 }