/*
    * 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.routing;
  
  import java.util.Map.Entry;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentMap;
  import java.util.concurrent.ScheduledFuture;
  import java.util.concurrent.TimeUnit;
  
  import org.apache.logging.log4j.Logger;
  import org.apache.logging.log4j.core.AbstractLifeCycle;
  import org.apache.logging.log4j.core.LogEvent;
  import org.apache.logging.log4j.core.config.Configuration;
  import org.apache.logging.log4j.core.config.ConfigurationScheduler;
  import org.apache.logging.log4j.core.config.Scheduled;
  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.PluginFactory;
  import org.apache.logging.log4j.status.StatusLogger;
  
  /**
   * Policy is purging appenders that were not in use specified time in minutes
   */
  @Plugin(name = "IdlePurgePolicy", category = "Core", printObject = true)
  @Scheduled
  public class IdlePurgePolicy extends AbstractLifeCycle implements PurgePolicy, Runnable {
  
      private static final Logger LOGGER = StatusLogger.getLogger();
      private final long timeToLive;
      private final ConcurrentMap<String, Long> appendersUsage = new ConcurrentHashMap<>();
      private RoutingAppender routingAppender;
      private final ConfigurationScheduler scheduler;
      private volatile ScheduledFuture<?> future = null;
  
      public IdlePurgePolicy(final long timeToLive, final ConfigurationScheduler scheduler) {
          this.timeToLive = timeToLive;
          this.scheduler = scheduler;
      }
  
      @Override
      public void initialize(final RoutingAppender routingAppender) {
          this.routingAppender = routingAppender;
      }
  
      @Override
      public void stop() {
          super.stop();
          future.cancel(true);
      }
  
      /**
       * Purging appenders that were not in use specified time
       */
      @Override
      public void purge() {
          final long createTime = System.currentTimeMillis() - timeToLive;
          for (final Entry<String, Long> entry : appendersUsage.entrySet()) {
              if (entry.getValue() < createTime) {
                  LOGGER.debug("Removing appender " + entry.getKey());
                  appendersUsage.remove(entry.getKey());
                  routingAppender.deleteAppender(entry.getKey());
              }
          }
      }
  
      @Override
      public void update(final String key, final LogEvent event) {
          final long now = System.currentTimeMillis();
          appendersUsage.put(key, now);
          if (future == null) {
              synchronized (this) {
                  if (future == null) {
                      scheduleNext();
                  }
              }
          }
  
      }
  
      @Override
      public void run() {
          purge();
          scheduleNext();
     }
 
     private void scheduleNext() {
         long createTime = Long.MAX_VALUE;
         for (final Entry<String, Long> entry : appendersUsage.entrySet()) {
             if (entry.getValue() < createTime) {
                 createTime = entry.getValue();
             }
         }
         if (createTime < Long.MAX_VALUE) {
             final long interval = timeToLive - (System.currentTimeMillis() - createTime);
             future = scheduler.schedule(this, interval, TimeUnit.MILLISECONDS);
         }
     }
 
     /**
      * Create the PurgePolicy
      *
      * @param timeToLive the number of increments of timeUnit before the Appender should be purged.
      * @param timeUnit   the unit of time the timeToLive is expressed in.
      * @return The Routes container.
      */
     @PluginFactory
     public static PurgePolicy createPurgePolicy(
         @PluginAttribute("timeToLive") final String timeToLive,
         @PluginAttribute("timeUnit") final String timeUnit,
         @PluginConfiguration final Configuration configuration) {
 
         if (timeToLive == null) {
             LOGGER.error("A timeToLive  value is required");
             return null;
         }
         TimeUnit units;
         if (timeUnit == null) {
             units = TimeUnit.MINUTES;
         } else {
             try {
                 units = TimeUnit.valueOf(timeUnit.toUpperCase());
             } catch (final Exception ex) {
                 LOGGER.error("Invalid time unit {}", timeUnit);
                 units = TimeUnit.MINUTES;
             }
         }
 
         final long ttl = units.toMillis(Long.parseLong(timeToLive));
 
 
         return new IdlePurgePolicy(ttl, configuration.getScheduler());
     }
 
     @Override
     public String toString() {
         return "timeToLive=" + timeToLive;
     }
 
 }