/*
    * 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.pattern;
  
  import java.lang.management.ManagementFactory;
  
  import org.apache.logging.log4j.core.LogEvent;
  import org.apache.logging.log4j.core.config.plugins.Plugin;
  
  /**
   * Returns the relative time in milliseconds since JVM Startup.
   */
  @Plugin(name = "RelativeTimePatternConverter", category = PatternConverter.CATEGORY)
  @ConverterKeys({ "r", "relative" })
  public class RelativeTimePatternConverter extends LogEventPatternConverter {
      /**
       * Cached formatted timestamp.
       */
      private long lastTimestamp = Long.MIN_VALUE;
      private final long startTime = ManagementFactory.getRuntimeMXBean().getStartTime();
      private String relative;
  
      /**
       * Private constructor.
       */
      public RelativeTimePatternConverter() {
          super("Time", "time");
      }
  
      /**
       * Obtains an instance of RelativeTimePatternConverter.
       *
       * @param options options, currently ignored, may be null.
       * @return instance of RelativeTimePatternConverter.
       */
      public static RelativeTimePatternConverter newInstance(
          final String[] options) {
          return new RelativeTimePatternConverter();
      }
  
      /**
       * {@inheritDoc}
       */
      @Override
      public void format(final LogEvent event, final StringBuilder toAppendTo) {
          final long timestamp = event.getTimeMillis();
  
          synchronized (this) {
              if (timestamp != lastTimestamp) {
                  lastTimestamp = timestamp;
                  relative = Long.toString(timestamp - startTime);
              }
          }
          toAppendTo.append(relative);
      }
  }