/*
    * 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.rewrite;
  
  import java.util.Map;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentMap;
  
  import org.apache.logging.log4j.core.Appender;
  import org.apache.logging.log4j.core.Filter;
  import org.apache.logging.log4j.core.LogEvent;
  import org.apache.logging.log4j.core.appender.AbstractAppender;
  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.plugins.Plugin;
  import org.apache.logging.log4j.core.config.plugins.PluginAttribute;
  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.util.Booleans;
  
  /**
   * This Appender allows the logging event to be manipulated before it is processed by other Appenders.
   */
  @Plugin(name = "Rewrite", category = "Core", elementType = "appender", printObject = true)
  public final class RewriteAppender extends AbstractAppender {
      private final Configuration config;
      private final ConcurrentMap<String, AppenderControl> appenders = new ConcurrentHashMap<String, AppenderControl>();
      private final RewritePolicy rewritePolicy;
      private final AppenderRef[] appenderRefs;
  
      private RewriteAppender(final String name, final Filter filter, final boolean ignoreExceptions,
                              final AppenderRef[] appenderRefs, final RewritePolicy rewritePolicy,
                              final Configuration config) {
          super(name, filter, null, ignoreExceptions);
          this.config = config;
          this.rewritePolicy = rewritePolicy;
          this.appenderRefs = appenderRefs;
      }
  
      @Override
      public void start() {
          for (final AppenderRef ref : appenderRefs) {
              final String name = ref.getRef();
              final Appender appender = config.getAppender(name);
              if (appender != null) {
                  final Filter filter = appender instanceof AbstractAppender ?
                      ((AbstractAppender) appender).getFilter() : null;
                  appenders.put(name, new AppenderControl(appender, ref.getLevel(), filter));
              } else {
                  LOGGER.error("Appender " + ref + " cannot be located. Reference ignored");
              }
          }
          super.start();
      }
  
      @Override
      public void stop() {
          super.stop();
      }
  
      /**
       * Modify the event and pass to the subordinate Appenders.
       * @param event The LogEvent.
       */
      @Override
      public void append(LogEvent event) {
          if (rewritePolicy != null) {
              event = rewritePolicy.rewrite(event);
          }
          for (final AppenderControl control : appenders.values()) {
              control.callAppender(event);
          }
      }
  
      /**
       * Create a RewriteAppender.
       * @param name The name of the Appender.
       * @param ignore If {@code "true"} (default) exceptions encountered when appending events are logged; otherwise
       *               they are propagated to the caller.
       * @param appenderRefs An array of Appender names to call.
       * @param config The Configuration.
       * @param rewritePolicy The policy to use to modify the event.
       * @param filter A Filter to filter events.
      * @return The created RewriteAppender.
      */
     @PluginFactory
     public static RewriteAppender createAppender(
             @PluginAttribute("name") final String name,
             @PluginAttribute("ignoreExceptions") final String ignore,
             @PluginElement("AppenderRef") final AppenderRef[] appenderRefs,
             @PluginConfiguration final Configuration config,
             @PluginElement("RewritePolicy") final RewritePolicy rewritePolicy,
             @PluginElement("Filter") final Filter filter) {
 
         final boolean ignoreExceptions = Booleans.parseBoolean(ignore, true);
         if (name == null) {
             LOGGER.error("No name provided for RewriteAppender");
             return null;
         }
         if (appenderRefs == null) {
             LOGGER.error("No appender references defined for RewriteAppender");
             return null;
         }
         return new RewriteAppender(name, filter, ignoreExceptions, appenderRefs, rewritePolicy, config);
     }
 }