/*
    * 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.jul;
  
  import java.io.Serializable;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.Comparator;
  import java.util.IdentityHashMap;
  import java.util.List;
  import java.util.Map;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentMap;
  
  import org.apache.logging.log4j.Level;
  
  /**
   * Default implementation of LevelConverter strategy.
   * <p>
   * Since 2.4, supports custom JUL levels by mapping them to their closest mapped neighbour.
   * </p>
   *
   * @since 2.1
   */
  public class DefaultLevelConverter implements LevelConverter {
  
      static final class JulLevelComparator implements Comparator<java.util.logging.Level>, Serializable {
          private static final long serialVersionUID = 1L;
          @Override
          public int compare(final java.util.logging.Level level1, final java.util.logging.Level level2) {
              return Integer.compare(level1.intValue(), level2.intValue());
          }
      }
  
      private final ConcurrentMap<java.util.logging.Level, Level> julToLog4j = new ConcurrentHashMap<>(9);
      private final Map<Level, java.util.logging.Level> log4jToJul = new IdentityHashMap<>(10);
      private final List<java.util.logging.Level> sortedJulLevels = new ArrayList<>(9);
  
      public DefaultLevelConverter() {
          // Map JUL to Log4j
          mapJulToLog4j(java.util.logging.Level.ALL, Level.ALL);
          mapJulToLog4j(java.util.logging.Level.FINEST, LevelTranslator.FINEST);
          mapJulToLog4j(java.util.logging.Level.FINER, Level.TRACE);
          mapJulToLog4j(java.util.logging.Level.FINE, Level.DEBUG);
          mapJulToLog4j(java.util.logging.Level.CONFIG, LevelTranslator.CONFIG);
          mapJulToLog4j(java.util.logging.Level.INFO, Level.INFO);
          mapJulToLog4j(java.util.logging.Level.WARNING, Level.WARN);
          mapJulToLog4j(java.util.logging.Level.SEVERE, Level.ERROR);
          mapJulToLog4j(java.util.logging.Level.OFF, Level.OFF);
          // Map Log4j to JUL
          mapLog4jToJul(Level.ALL, java.util.logging.Level.ALL);
          mapLog4jToJul(LevelTranslator.FINEST, java.util.logging.Level.FINEST);
          mapLog4jToJul(Level.TRACE, java.util.logging.Level.FINER);
          mapLog4jToJul(Level.DEBUG, java.util.logging.Level.FINE);
          mapLog4jToJul(LevelTranslator.CONFIG, java.util.logging.Level.CONFIG);
          mapLog4jToJul(Level.INFO, java.util.logging.Level.INFO);
          mapLog4jToJul(Level.WARN, java.util.logging.Level.WARNING);
          mapLog4jToJul(Level.ERROR, java.util.logging.Level.SEVERE);
          mapLog4jToJul(Level.FATAL, java.util.logging.Level.SEVERE);
          mapLog4jToJul(Level.OFF, java.util.logging.Level.OFF);
          // Sorted Java levels
          sortedJulLevels.addAll(julToLog4j.keySet());
          Collections.sort(sortedJulLevels, new JulLevelComparator());
  
      }
  
      private long distance(final java.util.logging.Level javaLevel, final java.util.logging.Level customJavaLevel) {
          return Math.abs((long) customJavaLevel.intValue() - (long) javaLevel.intValue());
      }
  
      /*
       * TODO consider making public for advanced configuration.
       */
      private void mapJulToLog4j(final java.util.logging.Level julLevel, final Level level) {
          julToLog4j.put(julLevel, level);
      }
  
      /*
       * TODO consider making public for advanced configuration.
       */
      private void mapLog4jToJul(final Level level, final java.util.logging.Level julLevel) {
          log4jToJul.put(level, julLevel);
      }
  
     private Level nearestLevel(final java.util.logging.Level customJavaLevel) {
         long prevDist = Long.MAX_VALUE;
         java.util.logging.Level prevLevel = null;
         for (final java.util.logging.Level mappedJavaLevel : sortedJulLevels) {
             final long distance = distance(customJavaLevel, mappedJavaLevel);
             if (distance > prevDist) {
                 return julToLog4j.get(prevLevel);
             }
             prevDist = distance;
             prevLevel = mappedJavaLevel;
         }
         return julToLog4j.get(prevLevel);
     }
 
     @Override
     public java.util.logging.Level toJavaLevel(final Level level) {
         return log4jToJul.get(level);
     }
 
     @Override
     public Level toLevel(final java.util.logging.Level javaLevel) {
         if (javaLevel == null) {
             return null;
         }
         final Level level = julToLog4j.get(javaLevel);
         if (level != null) {
             return level;
         }
         final Level nearestLevel = nearestLevel(javaLevel);
         julToLog4j.put(javaLevel, nearestLevel);
         return nearestLevel;
     }
 }