/*
    * Grapht, an open source dependency injector.
    * Copyright 2014-2015 various contributors (see CONTRIBUTORS.txt)
    * Copyright 2010-2014 Regents of the University of Minnesota
    *
    * This program is free software; you can redistribute it and/or modify
    * it under the terms of the GNU Lesser General Public License as
    * published by the Free Software Foundation; either version 2.1 of the
    * License, or (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful, but WITHOUT
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
   * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
   * details.
   *
   * You should have received a copy of the GNU General Public License along with
   * this program; if not, write to the Free Software Foundation, Inc., 51
   * Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
   */
  package org.grouplens.grapht;
  
  import com.google.common.base.Throwables;
  import com.google.common.util.concurrent.UncheckedExecutionException;
  import org.apache.commons.lang3.reflect.MethodUtils;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import javax.annotation.PreDestroy;
  import java.lang.reflect.InvocationTargetException;
  import java.lang.reflect.Method;
  import java.util.Deque;
  import java.util.LinkedList;
  
  public class LifecycleManager implements AutoCloseable {
      private static final Logger logger = LoggerFactory.getLogger(LifecycleManager.class);
      private Deque<TeardownAction> actions = new LinkedList<TeardownAction>();
  
      /**
       * Register a component with the lifecycle manager.  The component will be torn down when the lifecycle manager
       * is closed, using whatever teardown the lifecycle manager institutes.
       *
       * @param instance The component to register.
       */
      public void registerComponent(Object instance) {
          if (instance == null) {
              return;
          }
  
          if (instance instanceof AutoCloseable) {
              actions.add(new CloseAction((AutoCloseable) instance));
          }
          for (Method m: MethodUtils.getMethodsListWithAnnotation(instance.getClass(), PreDestroy.class)) {
              actions.add(new PreDestroyAction(instance, m));
          }
      }
  
      /**
       * Close the lifecycle manager, shutting down all components it manages.
       */
      @Override
      public void close() {
          Throwable error = null;
          while (!actions.isEmpty()) {
              TeardownAction action = actions.removeFirst();
              try {
                  action.destroy();
              } catch (Throwable th) {
                  if (error == null) {
                      error = th;
                  } else {
                      error.addSuppressed(th);
                  }
              }
          }
          if (error != null) {
              throw Throwables.propagate(error);
          }
      }
  
      /**
       * Interface for actions that tear down components.
       */
      interface TeardownAction {
          void destroy();
      }
  
      static class PreDestroyAction implements TeardownAction {
          private final Object instance;
          private final Method method;
  
          public PreDestroyAction(Object inst, Method m) {
              instance = inst;
              method = m;
          }
  
          @Override
          public void destroy() {
              try {
                  logger.debug("invoking pre-destroy method {} on {}", method, instance);
                 method.invoke(instance);
             } catch (IllegalAccessException e) {
                 throw new RuntimeException("cannot access " + method, e);
             } catch (InvocationTargetException e) {
                 throw new UncheckedExecutionException("error invoking " + method, e);
             }
         }
     }
 
     static class CloseAction implements TeardownAction {
         private final AutoCloseable instance;
 
         public CloseAction(AutoCloseable inst) {
             instance = inst;
         }
 
         @Override
         public void destroy() {
             try {
                 logger.debug("closing {}", instance);
                 instance.close();
             } catch (Exception e) {
                 throw new UncheckedExecutionException("Error destroying " + instance, e);
             }
         }
     }
 }