/**
    * This file Copyright (c) 2008-2015 Magnolia International
    * Ltd.  (http://www.magnolia-cms.com). All rights reserved.
    *
    *
    * This file is dual-licensed under both the Magnolia
    * Network Agreement and the GNU General Public License.
    * You may elect to use one or the other of these licenses.
    *
   * This file is distributed in the hope that it will be
   * useful, but AS-IS and WITHOUT ANY WARRANTY; without even the
   * implied warranty of MERCHANTABILITY or FITNESS FOR A
   * PARTICULAR PURPOSE, TITLE, or NONINFRINGEMENT.
   * Redistribution, except as permitted by whichever of the GPL
   * or MNA you select, is prohibited.
   *
   * 1. For the GPL license (GPL), you can redistribute and/or
   * modify this file under the terms of the GNU General
   * Public License, Version 3, as published by the Free Software
   * Foundation.  You should have received a copy of the GNU
   * General Public License, Version 3 along with this program;
   * if not, write to the Free Software Foundation, Inc., 51
   * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * 2. For the Magnolia Network Agreement (MNA), this file
   * and the accompanying materials are made available under the
   * terms of the MNA which accompanies this distribution, and
   * is available at http://www.magnolia-cms.com/mna.html
   *
   * Any modifications to this file must keep this entire header
   * intact.
   *
   */
  package info.magnolia.module.rssaggregator.importhandler;
  
  import info.magnolia.objectfactory.ComponentProvider;
  
  import java.util.ArrayList;
  import java.util.List;
  import java.util.Set;
  import java.util.concurrent.CancellationException;
  import java.util.concurrent.ExecutionException;
  import java.util.concurrent.ExecutorService;
  import java.util.concurrent.Executors;
  import java.util.concurrent.Future;
  import java.util.concurrent.TimeUnit;
  
  import javax.inject.Inject;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import com.sun.syndication.fetcher.impl.HashMapFeedInfoCache;
  
  /**
   * A multithreaded {@link RSSFeedFetcher} for feed retrieval over <code>http</code> that follows redirects and supports
   * conditional gets. <p/> Will attempt to fetch all {@link FeedChannel feed channels} defined in the provided {@link
   * AggregateFeed aggregate feeds}, processing {@value #NUMBER_OF_THREADS} feeds simultaneously. Failures to fetch a feed
   * result for a given feed channel are logged at ERROR level.
   *
   * @author Rob van der Linden Vooren
   * @see RSSFeedFetcher
   */
  public class FastRSSFeedFetcher implements RSSFeedFetcher {
  
      private static final Logger log = LoggerFactory.getLogger(FastRSSFeedFetcher.class);
  
      private static final int NUMBER_OF_THREADS = 3;
  
      private Class<? extends Runnable> feedChannelFetchTask;
  
      private int shutdownTimeout = 300000; // in milliseconds
  
      private final ExecutorService executorService;
  
      private ComponentProvider componentProvider;
  
      private ArrayList<Future<?>> futureList = new ArrayList<Future<?>>();
  
      @Inject
      public FastRSSFeedFetcher(ComponentProvider componentProvider) {
          this.componentProvider = componentProvider;
          setFeedChannelFetchTask(DefaultFeedChannelFetchTask.class);
          executorService = Executors.newFixedThreadPool(NUMBER_OF_THREADS);
      }
  
      @Override
      public Set<AggregateFeed> fetchAggregateFeeds(Set<AggregateFeed> aggregateFeeds) {
          for (AggregateFeed aggregate : aggregateFeeds) {
              for (FeedChannel channel : aggregate.getChannels()) {
                  Runnable task = componentProvider.newInstance(getFeedChannelFetchTaskClass(), new MgnlHttpURLFeedFetcher(HashMapFeedInfoCache.getInstance()), channel, aggregate.getName());
                  Future<?> future = executorService.submit(task);
                  futureList.add(future);
              }
          }
          // Each Future will block on get() when not done, thus ensuring this method will return only when all
          // attempts to fetch feed aggregates have completed.
          for (Future<?> future : futureList) {
              waitForFutureResult(future);
         }
         return aggregateFeeds;
     }
 
     protected void waitForFutureResult(Future<?> future) {
         try {
             future.get();
         } catch (InterruptedException ie) {
             // Restore the interrupted status
             Thread.currentThread().interrupt();
         } catch (ExecutionException ee) {
             log.error(ee.getMessage(), ee);
         } catch (CancellationException e) {
             //set as debug to not flood logs on shutdown
             log.debug("RSS feed update has been cancelled.");
         }
     }
 
     /**
      * All feeds that are being fetched will be shut down.
      */
     public void shutdown() {
         List<Runnable> runnables = executorService.shutdownNow();
         log.info("Canceling {} RSS Update Tasks because of shutdown...", runnables.size());
 
         // stop all running updates (if this is not done scheduler will hang on unfinished job(s) and instance won't shut down)
         for (Future<?> f : futureList) {
             f.cancel(true);
         }
 
         try {
             if (executorService.awaitTermination(getShutdownTimeout(), TimeUnit.MILLISECONDS)) {
                 log.info("Termination successful.");
             } else {
                 log.error("Termination timed out.");
             }
         } catch (InterruptedException e) {
             log.error("Termination error.", e);
         }
     }
 
     public Class<? extends Runnable> getFeedChannelFetchTaskClass() {
         return feedChannelFetchTask;
     }
 
     public void setFeedChannelFetchTask(Class<? extends Runnable> feedChannelFetchTask) {
         this.feedChannelFetchTask = feedChannelFetchTask;
     }
 
     public int getShutdownTimeout() {
         return shutdownTimeout;
     }
 
     public void setShutdownTimeout(int shutdownTimeout) {
         this.shutdownTimeout = shutdownTimeout;
     }
 
     protected ExecutorService getExecutorService() {
         return executorService;
     }
 }