/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements. See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF licenses this file to You under the Apache License, Version 2.0
    * (the "License"); you may not use this file except in compliance with
    * the License. You may obtain a copy of the License at
    *
    *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package org.apache.logging.log4j.core.osgi;
  
  import java.util.concurrent.atomic.AtomicReference;
  
  import org.apache.logging.log4j.Logger;
  import org.apache.logging.log4j.core.config.plugins.util.PluginRegistry;
  import org.apache.logging.log4j.core.util.Constants;
  import org.apache.logging.log4j.status.StatusLogger;
  import org.apache.logging.log4j.util.PropertiesUtil;
  import org.osgi.framework.Bundle;
  import org.osgi.framework.BundleActivator;
  import org.osgi.framework.BundleContext;
  import org.osgi.framework.BundleEvent;
  import org.osgi.framework.SynchronousBundleListener;
  import org.osgi.framework.wiring.BundleWiring;
  
  /**
   * OSGi BundleActivator.
   */
  public final class Activator implements BundleActivator, SynchronousBundleListener {
  
      private static final Logger LOGGER = StatusLogger.getLogger();
  
      private final AtomicReference<BundleContext> context = new AtomicReference<BundleContext>();
  
      @Override
      public void start(final BundleContext context) throws Exception {
          // allow the user to override the default ContextSelector (e.g., by using BasicContextSelector for a global cfg)
          if (PropertiesUtil.getProperties().getStringProperty(Constants.LOG4J_CONTEXT_SELECTOR) == null) {
              System.setProperty(Constants.LOG4J_CONTEXT_SELECTOR, BundleContextSelector.class.getName());
          }
          if (this.context.compareAndSet(null, context)) {
              context.addBundleListener(this);
              // done after the BundleListener as to not miss any new bundle installs in the interim
              scanInstalledBundlesForPlugins(context);
          }
      }
  
      private static void scanInstalledBundlesForPlugins(final BundleContext context) {
          final Bundle[] bundles = context.getBundles();
          for (final Bundle bundle : bundles) {
              if (bundle.getState() == Bundle.ACTIVE) {
                  // TODO: bundle state can change during this
                  scanBundleForPlugins(bundle);
              }
          }
      }
  
      private static void scanBundleForPlugins(final Bundle bundle) {
          LOGGER.trace("Scanning bundle [{}] for plugins.", bundle.getSymbolicName());
          PluginRegistry.getInstance().loadFromBundle(bundle.getBundleId(),
              bundle.adapt(BundleWiring.class).getClassLoader());
      }
  
      private static void stopBundlePlugins(final Bundle bundle) {
          LOGGER.trace("Stopping bundle [{}] plugins.", bundle.getSymbolicName());
          // TODO: plugin lifecycle code
          PluginRegistry.getInstance().clearBundlePlugins(bundle.getBundleId());
      }
  
      @Override
      public void stop(final BundleContext context) throws Exception {
          // not much can be done that isn't already automated by the framework
          this.context.compareAndSet(context, null);
          // TODO: shut down log4j
      }
  
      @Override
      public void bundleChanged(final BundleEvent event) {
          switch (event.getType()) {
              // FIXME: STARTING instead of STARTED?
              case BundleEvent.STARTED:
                  scanBundleForPlugins(event.getBundle());
                  break;
  
              case BundleEvent.STOPPING:
                  stopBundlePlugins(event.getBundle());
                  break;
  
              default:
                  break;
          }
     }
 }