/*
    * 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.appender;
  
  import org.apache.logging.log4j.core.Appender;
  import org.apache.logging.log4j.core.Filter;
  import org.apache.logging.log4j.core.Layout;
  import org.apache.logging.log4j.core.LogEvent;
  import org.apache.logging.log4j.core.config.AppenderControl;
  import org.apache.logging.log4j.core.config.AppenderRef;
  import org.apache.logging.log4j.core.config.Configuration;
  import org.apache.logging.log4j.core.config.ConfigurationException;
  import org.apache.logging.log4j.core.config.plugins.Plugin;
  import org.apache.logging.log4j.core.config.plugins.PluginAttr;
  import org.apache.logging.log4j.core.config.plugins.PluginConfiguration;
  import org.apache.logging.log4j.core.config.plugins.PluginElement;
  import org.apache.logging.log4j.core.config.plugins.PluginFactory;
  import org.apache.logging.log4j.core.impl.Log4jLogEvent;
  
  import java.io.Serializable;
  import java.util.ArrayList;
  import java.util.List;
  import java.util.Map;
  import java.util.concurrent.ArrayBlockingQueue;
  import java.util.concurrent.BlockingQueue;
  
  /**
   * Appends to one or more Appenders asynchronously.  You can configure an AsynchAppender with one
   * or more Appenders and an Appender to append to if the queue is full. The AsynchAppender does not allow
   * a filter to be specified on the Appender references.
   *
   * @param <T> The {@link Layout}'s {@link Serializable} type.
   */
  @Plugin(name = "Asynch", type = "Core", elementType = "appender", printObject = true)
  public final class AsynchAppender<T extends Serializable> extends AbstractAppender<T> {
  
      private static final int DEFAULT_QUEUE_SIZE = 128;
      private static final String SHUTDOWN = "Shutdown";
  
      private final BlockingQueue<Serializable> queue;
      private final boolean blocking;
      private final Configuration config;
      private final AppenderRef[] appenderRefs;
      private final String errorRef;
      private AppenderControl errorAppender;
      private AsynchThread thread;
  
      private AsynchAppender(final String name, final Filter filter, final AppenderRef[] appenderRefs,
                             final String errorRef, final int queueSize, final boolean blocking,
                             final boolean handleExceptions, final Configuration config) {
          super(name, filter, null, handleExceptions);
          this.queue = new ArrayBlockingQueue<Serializable>(queueSize);
          this.blocking = blocking;
          this.config = config;
          this.appenderRefs = appenderRefs;
          this.errorRef = errorRef;
      }
  
      @Override
      public void start() {
          final Map<String, Appender<?>> map = config.getAppenders();
          final List<AppenderControl> appenders = new ArrayList<AppenderControl>();
          for (final AppenderRef appenderRef : appenderRefs) {
              if (map.containsKey(appenderRef.getRef())) {
                  appenders.add(new AppenderControl(map.get(appenderRef.getRef()), null, null));
              } else {
                  LOGGER.error("No appender named {} was configured", appenderRef);
              }
          }
          if (errorRef != null) {
              if (map.containsKey(errorRef)) {
                  errorAppender = new AppenderControl(map.get(errorRef), null, null);
              } else {
                  LOGGER.error("Unable to set up error Appender. No appender named {} was configured", errorRef);
              }
          }
          if (appenders.size() > 0) {
              thread = new AsynchThread(appenders, queue);
          } else if (errorRef == null) {
              throw new ConfigurationException("No appenders are available for AsynchAppender " + getName());
          }
  
          thread.start();
          super.start();
      }
 
     @Override
     public void stop() {
         super.stop();
         thread.shutdown();
         try {
             thread.join();
         } catch (final InterruptedException ex) {
             LOGGER.warn("Interrupted while stopping AsynchAppender {}", getName());
         }
     }
 
     /**
      * Actual writing occurs here.
      * <p/>
      * @param event The LogEvent.
      */
     public void append(final LogEvent event) {
         if (!isStarted()) {
             throw new IllegalStateException("AsynchAppender " + getName() + " is not active");
         }
         if (event instanceof Log4jLogEvent) {
             if (blocking && queue.remainingCapacity() > 0) {
                 try {
                     queue.add(Log4jLogEvent.serialize((Log4jLogEvent) event));
                     return;
                 } catch (final IllegalStateException ex) {
                     error("Appender " + getName() + " is unable to write primary appenders. queue is full");
                 }
             }
             if (errorAppender != null) {
                 if (!blocking) {
                     error("Appender " + getName() + " is unable to write primary appenders. queue is full");
                 }
                 errorAppender.callAppender(event);
             }
         }
     }
 
     /**
      * Create an AsynchAppender.
      * @param appenderRefs The Appenders to reference.
      * @param errorRef An optional Appender to write to if the queue is full or other errors occur.
      * @param blocking True if the Appender should wait when the queue is full. The default is true.
      * @param size The size of the event queue. The default is 128.
      * @param name The name of the Appender.
      * @param filter The Filter or null.
      * @param config The Configuration.
      * @param suppress "true" if exceptions should be hidden from the application, "false" otherwise.
      * The default is "true".
      * @param <S> The actual type of the Serializable.
      * @return The AsynchAppender.
      */
     @PluginFactory
     public static <S extends Serializable> AsynchAppender<S> createAppender(
                                                 @PluginElement("appender-ref") final AppenderRef[] appenderRefs,
                                                 @PluginAttr("error-ref") final String errorRef,
                                                 @PluginAttr("blocking") final String blocking,
                                                 @PluginAttr("bufferSize") final String size,
                                                 @PluginAttr("name") final String name,
                                                 @PluginElement("filter") final Filter filter,
                                                 @PluginConfiguration final Configuration config,
                                                 @PluginAttr("suppressExceptions") final String suppress) {
         if (name == null) {
             LOGGER.error("No name provided for AsynchAppender");
             return null;
         }
         if (appenderRefs == null) {
             LOGGER.error("No appender references provided to AsynchAppender {}", name);
         }
 
         final boolean isBlocking = blocking == null ? true : Boolean.valueOf(blocking);
         final int queueSize = size == null ? DEFAULT_QUEUE_SIZE : Integer.parseInt(size);
 
         final boolean handleExceptions = suppress == null ? true : Boolean.valueOf(suppress);
 
         return new AsynchAppender<S>(name, filter, appenderRefs, errorRef, queueSize, isBlocking, handleExceptions,
                                   config);
     }
 
     /**
      * Thread that calls the Appenders.
      */
     private class AsynchThread extends Thread {
 
         private volatile boolean shutdown = false;
         private final List<AppenderControl> appenders;
         private final BlockingQueue<Serializable> queue;
 
         public AsynchThread(final List<AppenderControl> appenders, final BlockingQueue<Serializable> queue) {
             this.appenders = appenders;
             this.queue = queue;
         }
 
         @Override
         public void run() {
             while (!shutdown) {
                 Serializable s;
                 try {
                     s = queue.take();
                     if (s != null && s instanceof String && SHUTDOWN.equals(s.toString())) {
                         shutdown = true;
                         continue;
                     }
                 } catch (final InterruptedException ex) {
                     // No good reason for this.
                     continue;
                 }
                 final Log4jLogEvent event = Log4jLogEvent.deserialize(s);
                 boolean success = false;
                 for (final AppenderControl control : appenders) {
                     try {
                         control.callAppender(event);
                         success = true;
                     } catch (final Exception ex) {
                         // If no appender is successful the error appender will get it.
                     }
                 }
                 if (!success && errorAppender != null) {
                     try {
                         errorAppender.callAppender(event);
                     } catch (final Exception ex) {
                         // Silently accept the error.
                     }
                 }
             }
             // Process any remaining items in the queue.
             while (!queue.isEmpty()) {
                 try {
                     final Log4jLogEvent event = Log4jLogEvent.deserialize(queue.take());
                     for (final AppenderControl control : appenders) {
                         control.callAppender(event);
                     }
                 } catch (final InterruptedException ex) {
                     // May have been interrupted to shut down.
                 }
             }
         }
 
         public void shutdown() {
             shutdown = true;
             if (queue.isEmpty()) {
                 queue.offer(SHUTDOWN);
             }
         }
     }
 }