/**
    * This file Copyright (c) 2014-2015 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.classpathwatch;
  
  import info.magnolia.init.MagnoliaConfigurationProperties;
  
  import java.io.IOException;
  import java.net.URL;
  import java.util.concurrent.Executors;
  import java.util.concurrent.Future;
  import java.util.concurrent.ScheduledExecutorService;
  import java.util.concurrent.TimeUnit;
  
  import javax.inject.Inject;
  import javax.inject.Singleton;
  import javax.servlet.ServletContext;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import com.google.common.base.Function;
  import com.google.common.base.Predicate;
  
  /**
   * Service controlling execution of the @link {@link ClasspathScanner}.
   */
  @Singleton
  public class ClasspathScannerService {
  
      private static final int SCAN_INTERVAL = 10;
  
      private static final Logger log = LoggerFactory.getLogger(ClasspathScannerService.class);
  
      private final ServletContext servletContext;
      private final boolean devMode;
  
      private ScheduledExecutorService executorService;
      private ClasspathScanner scanner;
  
      private Future<?> scannerFuture;
  
      @Inject
      public ClasspathScannerService(MagnoliaConfigurationProperties mcp, ServletContext servletContext) throws IOException {
          this.servletContext = servletContext;
          this.devMode = mcp.getBooleanProperty("magnolia.develop");
          if (!devMode) {
              log.info("Not in dev mode, will not watch resource changes on the classpath.");
          }
      }
  
      public void start() {
      }
  
      public boolean isEnabled() {
          return devMode;
      }
  
      /**
       * Sets up observation of classpath resource changes.
       */
      public synchronized void watch(Predicate<String> resourcesFilter, Predicate<? super URL> urlsFilter, Function<String, Void> callbackFunction) {
          if (!devMode) {
              return;
          }
  
          /*
           * All ClasspathOrigins have the same resource and url exclusion filters, by implementation/design.
           * 
          * - For now, first ClasspathResourceOrigin requesting #watchForChanges passes these on; scanner is then created accordingly.
          * - Hence we currently don't support scanning for heterogeneous ClasspathOrigins with different filtering impl.
          * - LegacyClasspathResourceOrigin is intentionally left out, in particular as it's not meant to host config files.
          * - We may revise this whenever there is need for generalization.
          */
         if (scannerFuture == null) {
             scanner = new ClasspathScanner(resourcesFilter, urlsFilter, servletContext);
 
             // We intentionally use a single thread executor (single ClasspathScanner with multiple callbacks)
             executorService = Executors.newSingleThreadScheduledExecutor();
             log.info("Scheduling execution of ClasspathScanner every {}s.", SCAN_INTERVAL);
             scannerFuture = executorService.scheduleWithFixedDelay(scanner, SCAN_INTERVAL, SCAN_INTERVAL, TimeUnit.SECONDS);
         }
         scanner.watchResourceChanges(callbackFunction);
     }
 
     public void stop() {
         if (executorService != null) {
             executorService.shutdownNow();
             boolean terminated = false;
             try {
                 terminated = executorService.awaitTermination(1, TimeUnit.SECONDS);
             } catch (InterruptedException e) {
                 log.error("Exception during service termination", e);
             }
             if (terminated) {
                 log.info("{} terminated.", getClass().getSimpleName());
             } else {
                 log.warn("{} not terminated, some tasks are still running.", getClass().getSimpleName());
             }
         }
     }
 
 }