/*
    * 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.util;
  
  import java.net.URL;
  import java.security.Permission;
  import java.util.Collection;
  import java.util.List;
  
  import org.apache.logging.log4j.Logger;
  import org.apache.logging.log4j.spi.LoggerContextFactory;
  import org.apache.logging.log4j.spi.Provider;
  import org.apache.logging.log4j.status.StatusLogger;
  import org.osgi.framework.AdaptPermission;
  import org.osgi.framework.AdminPermission;
  import org.osgi.framework.Bundle;
  import org.osgi.framework.BundleActivator;
  import org.osgi.framework.BundleContext;
  import org.osgi.framework.BundleEvent;
  import org.osgi.framework.InvalidSyntaxException;
  import org.osgi.framework.ServiceReference;
  import org.osgi.framework.SynchronousBundleListener;
  import org.osgi.framework.wiring.BundleWire;
  import org.osgi.framework.wiring.BundleWiring;
  
  /**
   * <em>Consider this class private.</em>
   * OSGi bundle activator. Used for locating an implementation of
   * {@link org.apache.logging.log4j.spi.LoggerContextFactory} et al. that have corresponding
   * {@code META-INF/log4j-provider.properties} files. As with all OSGi BundleActivator classes, this class is not for
   * public use and is only useful in an OSGi framework environment.
   */
  public class Activator implements BundleActivator, SynchronousBundleListener {
  
      private static final SecurityManager SECURITY_MANAGER = System.getSecurityManager();
  
      private static final Logger LOGGER = StatusLogger.getLogger();
  
      // until we have at least one Provider, we'll lock ProviderUtil which locks LogManager.<clinit> by extension.
      // this variable needs to be reset once the lock has been released
      private boolean lockingProviderUtil;
  
      private static void checkPermission(final Permission permission) {
          if (SECURITY_MANAGER != null) {
              SECURITY_MANAGER.checkPermission(permission);
          }
      }
  
      private void loadProvider(final Bundle bundle) {
          if (bundle.getState() == Bundle.UNINSTALLED) {
              return;
          }
          try {
              checkPermission(new AdminPermission(bundle, AdminPermission.RESOURCE));
              checkPermission(new AdaptPermission(BundleWiring.class.getName(), bundle, AdaptPermission.ADAPT));
              loadProvider(bundle.getBundleContext(), bundle.adapt(BundleWiring.class));
          } catch (final SecurityException e) {
              LOGGER.debug("Cannot access bundle [{}] contents. Ignoring.", bundle.getSymbolicName(), e);
          } catch (final Exception e) {
              LOGGER.warn("Problem checking bundle {} for Log4j 2 provider.", bundle.getSymbolicName(), e);
          }
      }
  
      private void loadProvider(final BundleContext context, final BundleWiring bundleWiring) {
          final String filter = "(APIVersion>=2.60)";
          try {
              final Collection<ServiceReference<Provider>> serviceReferences = context.getServiceReferences(Provider.class, filter);
              Provider maxProvider = null;
              for (final ServiceReference<Provider> serviceReference : serviceReferences) {
                  final Provider provider = context.getService(serviceReference);
                  if (maxProvider == null || provider.getPriority() > maxProvider.getPriority()) {
                      maxProvider = provider;
                  }
              }
              if (maxProvider != null) {
                  ProviderUtil.addProvider(maxProvider);
              }
          } catch (final InvalidSyntaxException ex) {
              LOGGER.error("Invalid service filter: " + filter, ex);
          }
          final List<URL> urls = bundleWiring.findEntries("META-INF", "log4j-provider.properties", 0);
          for (final URL url : urls) {
              ProviderUtil.loadProvider(url, bundleWiring.getClassLoader());
          }
      }
 
     @Override
     public void start(final BundleContext context) throws Exception {
         ProviderUtil.STARTUP_LOCK.lock();
         lockingProviderUtil = true;
         final BundleWiring self = context.getBundle().adapt(BundleWiring.class);
         final List<BundleWire> required = self.getRequiredWires(LoggerContextFactory.class.getName());
         for (final BundleWire wire : required) {
             loadProvider(context, wire.getProviderWiring());
         }
         context.addBundleListener(this);
         final Bundle[] bundles = context.getBundles();
         for (final Bundle bundle : bundles) {
             loadProvider(bundle);
         }
         unlockIfReady();
     }
 
     private void unlockIfReady() {
         if (lockingProviderUtil && !ProviderUtil.PROVIDERS.isEmpty()) {
             ProviderUtil.STARTUP_LOCK.unlock();
             lockingProviderUtil = false;
         }
     }
 
     @Override
     public void stop(final BundleContext context) throws Exception {
         context.removeBundleListener(this);
         unlockIfReady();
     }
 
     @Override
     public void bundleChanged(final BundleEvent event) {
         switch (event.getType()) {
             case BundleEvent.STARTED:
                 loadProvider(event.getBundle());
                 unlockIfReady();
                 break;
 
             default:
                 break;
         }
     }
 
 }