/*
    * 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.config;
  
  import java.util.Objects;
  import java.util.concurrent.locks.ReadWriteLock;
  import java.util.concurrent.locks.ReentrantReadWriteLock;
  
  import org.apache.logging.log4j.Level;
  import org.apache.logging.log4j.Marker;
  import org.apache.logging.log4j.core.LogEvent;
  import org.apache.logging.log4j.message.Message;
  import org.apache.logging.log4j.util.Supplier;
  
  /**
   * ReliabilityStrategy that uses read/write locks to prevent the LoggerConfig from stopping while it is in use.
   */
  public class LockingReliabilityStrategy implements ReliabilityStrategy {
      private final LoggerConfig loggerConfig;
      private final ReadWriteLock reconfigureLock = new ReentrantReadWriteLock();
      private volatile boolean isStopping = false;
  
      public LockingReliabilityStrategy(final LoggerConfig loggerConfig) {
          this.loggerConfig = Objects.requireNonNull(loggerConfig, "loggerConfig was null");
      }
  
      /*
       * (non-Javadoc)
       *
       * @see org.apache.logging.log4j.core.config.ReliabilityStrategy#log(org.apache.logging.log4j.util.Supplier,
       * java.lang.String, java.lang.String, org.apache.logging.log4j.Marker, org.apache.logging.log4j.Level,
       * org.apache.logging.log4j.message.Message, java.lang.Throwable)
       */
      @Override
      public void log(final Supplier<LoggerConfig> reconfigured, final String loggerName, final String fqcn,
              final Marker marker, final Level level, final Message data, final Throwable t) {
  
          final LoggerConfig config = getActiveLoggerConfig(reconfigured);
          try {
              config.log(loggerName, fqcn, marker, level, data, t);
          } finally {
              config.getReliabilityStrategy().afterLogEvent();
          }
      }
  
      /*
       * (non-Javadoc)
       *
       * @see org.apache.logging.log4j.core.config.ReliabilityStrategy#log(org.apache.logging.log4j.util.Supplier,
       * org.apache.logging.log4j.core.LogEvent)
       */
      @Override
      public void log(final Supplier<LoggerConfig> reconfigured, final LogEvent event) {
          final LoggerConfig config = getActiveLoggerConfig(reconfigured);
          try {
              config.log(event);
          } finally {
              config.getReliabilityStrategy().afterLogEvent();
          }
      }
  
      /*
       * (non-Javadoc)
       *
       * @see
       * org.apache.logging.log4j.core.config.ReliabilityStrategy#beforeLogEvent(org.apache.logging.log4j.core.config.
       * LoggerConfig, org.apache.logging.log4j.util.Supplier)
       */
      @Override
      public LoggerConfig getActiveLoggerConfig(final Supplier<LoggerConfig> next) {
          LoggerConfig result = this.loggerConfig;
          if (!beforeLogEvent()) {
              result = next.get();
              return result == this.loggerConfig ? result : result.getReliabilityStrategy().getActiveLoggerConfig(next);
          }
          return result;
      }
  
      private boolean beforeLogEvent() {
          reconfigureLock.readLock().lock();
          if (isStopping) {
              reconfigureLock.readLock().unlock();
              return false;
          }
         return true;
     }
 
     @Override
     public void afterLogEvent() {
         reconfigureLock.readLock().unlock();
     }
 
     /*
      * (non-Javadoc)
      *
      * @see org.apache.logging.log4j.core.config.ReliabilityStrategy#beforeStopAppenders()
      */
     @Override
     public void beforeStopAppenders() {
         reconfigureLock.writeLock().lock();
         try {
             isStopping = true;
         } finally {
             reconfigureLock.writeLock().unlock();
         }
     }
 
     /*
      * (non-Javadoc)
      *
      * @see
      * org.apache.logging.log4j.core.config.ReliabilityStrategy#beforeStopConfiguration(org.apache.logging.log4j.core
      * .config.Configuration)
      */
     @Override
     public void beforeStopConfiguration(final Configuration configuration) {
         // no action
     }
 
 }