/**
    * This file Copyright (c) 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.imaging;
  
  import info.magnolia.module.ModuleLifecycle;
  import info.magnolia.module.ModuleLifecycleContext;
  
  import java.util.ArrayList;
  import java.util.Iterator;
  import java.util.LinkedHashMap;
  import java.util.List;
  import java.util.Map;
  
  import javax.imageio.ImageIO;
  import javax.imageio.spi.IIORegistry;
  import javax.imageio.spi.ServiceRegistry;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * Keeps the configuration of the imaging module.
   */
  public class ImagingModule implements ModuleLifecycle {
  
      private static final Logger log = LoggerFactory.getLogger(ImagingModule.class);
  
      private Map<String, ImageGenerator> generators = new LinkedHashMap<String, ImageGenerator>();
  
      public void addGenerator(String name, ImageGenerator generator) {
          generators.put(name, generator);
      }
  
      public void setGenerators(Map<String, ImageGenerator> generators) {
          this.generators = generators;
      }
  
      public Map<String, ImageGenerator> getGenerators() {
          return generators;
      }
  
      /**
       * Scan for additional plugins when module starts.
       *
       * @see ImageIO#scanForPlugins()
       */
      @Override
      public void start(ModuleLifecycleContext moduleLifecycleContext) {
          ImageIO.scanForPlugins();
      }
  
      /**
       * De-registers all plugins which have the {@link Thread#getContextClassLoader() current thread's context class loader}
       * as its class loader when the module is stopped, to avoid class/resource leak.
       *
       * This is taken from com.twelvemonkeys.servlet.image.IIOProviderContextListener and the details are explained here:
       * https://github.com/haraldk/TwelveMonkeys#deploying-the-plugins-in-a-web-app .
       */
      @Override
      public void stop(ModuleLifecycleContext moduleLifecycleContext) {
  
          // De-register any locally registered IIO plugins. Relies on each web app having its own context class loader.
          final IIORegistry registry = IIORegistry.getDefaultInstance();
          final LocalFilter localFilter = new LocalFilter(Thread.currentThread().getContextClassLoader());
  
          Iterator<Class<?>> categories = registry.getCategories();
  
          while (categories.hasNext()) {
             Class<?> category = categories.next();
             Iterator<?> providers = registry.getServiceProviders(category, localFilter, false);
 
             // Copy the providers, as de-registering while iterating over providers will lead to ConcurrentModificationExceptions.
             List<Object> providersCopy = new ArrayList<>();
             while (providers.hasNext()) {
                 providersCopy.add(providers.next());
             }
 
             for (Object provider : providersCopy) {
                 registry.deregisterServiceProvider(provider);
                 log.debug("Unregistered locally installed provider class: {}", provider.getClass());
             }
         }
     }
 
     /**
      * Filters the providers based on their class loader.
      */
     static class LocalFilter implements ServiceRegistry.Filter {
         private final ClassLoader loader;
 
         public LocalFilter(ClassLoader loader) {
             this.loader = loader;
         }
 
         @Override
         public boolean filter(Object provider) {
             return provider.getClass().getClassLoader() == loader;
         }
     }
 }