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/**
 * 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 com.datatorrent.stram.util;

import java.util.Enumeration;
import java.util.Iterator;
import java.util.Map;
import java.util.regex.Pattern;

import javax.annotation.Nonnull;
import javax.annotation.Nullable;

import org.apache.log4j.Appender;
import org.apache.log4j.Category;
import org.apache.log4j.Level;
import org.apache.log4j.LogManager;
import org.apache.log4j.Logger;
import org.apache.log4j.spi.DefaultRepositorySelector;
import org.apache.log4j.spi.HierarchyEventListener;
import org.apache.log4j.spi.LoggerFactory;
import org.apache.log4j.spi.LoggerRepository;

import com.google.common.base.Function;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.Maps;

/**
 * @since 3.5.0
 */
public class LoggerUtil
{

  private static final org.slf4j.Logger logger = org.slf4j.LoggerFactory.getLogger(LoggerUtil.class);

  private static final Map patternLevel = Maps.newHashMap();
  private static final Map patterns = Maps.newHashMap();
  private static final Function levelToString = new Function()
  {
    @Override
    public String apply(@Nullable Level input)
    {
      return input == null ? "" : input.toString();
    }
  };

  private static class DelegatingLoggerRepository implements LoggerRepository
  {
    private static class DefaultLoggerFactory implements LoggerFactory
    {
      private static class DefaultLogger extends Logger
      {
        public DefaultLogger(String name)
        {
          super(name);
        }
      }

      @Override
      public Logger makeNewLoggerInstance(String name)
      {
        Logger logger = new DefaultLogger(name);
        Level level = getLevelFor(name);
        if (level != null) {
          logger.setLevel(level);
        }
        return logger;
      }
    }

    private final LoggerFactory loggerFactory = new DefaultLoggerFactory();
    private final LoggerRepository loggerRepository;

    private DelegatingLoggerRepository(LoggerRepository loggerRepository)
    {
      this.loggerRepository = loggerRepository;
    }

    @Override
    public void addHierarchyEventListener(HierarchyEventListener listener)
    {
      loggerRepository.addHierarchyEventListener(listener);
    }

    @Override
    public boolean isDisabled(int level)
    {
      return loggerRepository.isDisabled(level);
    }

    @Override
    public void setThreshold(Level level)
    {
      loggerRepository.setThreshold(level);
    }

    @Override
    public void setThreshold(String val)
    {
      loggerRepository.setThreshold(val);
    }

    @Override
    public void emitNoAppenderWarning(Category cat)
    {
      loggerRepository.emitNoAppenderWarning(cat);
    }

    @Override
    public Level getThreshold()
    {
      return loggerRepository.getThreshold();
    }

    @Override
    public Logger getLogger(String name)
    {
      return loggerRepository.getLogger(name, loggerFactory);
    }

    @Override
    public Logger getLogger(String name, LoggerFactory factory)
    {
      return loggerRepository.getLogger(name, factory);
    }

    @Override
    public Logger getRootLogger()
    {
      return loggerRepository.getRootLogger();
    }

    @Override
    public Logger exists(String name)
    {
      return loggerRepository.exists(name);
    }

    @Override
    public void shutdown()
    {
      loggerRepository.shutdown();
    }

    @Override
    public Enumeration getCurrentLoggers()
    {
      return loggerRepository.getCurrentLoggers();
    }

    @Override
    public Enumeration getCurrentCategories()
    {
      return loggerRepository.getCurrentCategories();
    }

    @Override
    public void fireAddAppenderEvent(Category logger, Appender appender)
    {
      loggerRepository.fireAddAppenderEvent(logger, appender);
    }

    @Override
    public void resetConfiguration()
    {
      loggerRepository.resetConfiguration();
    }
  }

  static {
    logger.debug("initializing LoggerUtil");
    LogManager.setRepositorySelector(new DefaultRepositorySelector(new DelegatingLoggerRepository(LogManager.getLoggerRepository())), null);
  }

  private static synchronized Level getLevelFor(String name)
  {
    if (patternLevel.isEmpty()) {
      return null;
    }
    String longestPatternKey = null;
    for (String patternKey : patternLevel.keySet()) {
      Pattern pattern = patterns.get(patternKey);
      if (pattern.matcher(name).matches() && (longestPatternKey == null || longestPatternKey.length() < patternKey.length())) {
        longestPatternKey = patternKey;
      }
    }
    if (longestPatternKey != null) {
      return patternLevel.get(longestPatternKey);
    }
    return null;
  }

  public static ImmutableMap getPatternLevels()
  {
    return ImmutableMap.copyOf(Maps.transformValues(patternLevel, levelToString));
  }

  public static synchronized void changeLoggersLevel(@Nonnull Map targetChanges)
  {
    /* remove existing patterns which are subsets of new patterns. for eg. if x.y.z.* will be removed if
     *  there is x.y.* in the target changes.
     */
    for (Map.Entry changeEntry : targetChanges.entrySet()) {
      Iterator> patternsIterator = patterns.entrySet().iterator();
      while ((patternsIterator.hasNext())) {
        Map.Entry entry = patternsIterator.next();
        String finer = entry.getKey();
        String wider = changeEntry.getKey();
        if (finer.length() < wider.length()) {
          continue;
        }
        boolean remove = false;
        for (int i = 0; i < wider.length(); i++) {
          if (wider.charAt(i) == '*') {
            remove = true;
            break;
          }
          if (wider.charAt(i) != finer.charAt(i)) {
            break;
          } else if (i == wider.length() - 1) {
            remove = true;
          }
        }
        if (remove) {
          patternsIterator.remove();
          patternLevel.remove(finer);
        }
      }
    }
    for (Map.Entry loggerEntry : targetChanges.entrySet()) {
      String target = loggerEntry.getKey();
      patternLevel.put(target, Level.toLevel(loggerEntry.getValue()));
      patterns.put(target, Pattern.compile(target));
    }

    if (!patternLevel.isEmpty()) {
      @SuppressWarnings("unchecked")
      Enumeration loggerEnumeration = LogManager.getCurrentLoggers();
      while (loggerEnumeration.hasMoreElements()) {
        Logger classLogger = loggerEnumeration.nextElement();
        Level oldLevel = classLogger.getLevel();
        Level newLevel = getLevelFor(classLogger.getName());
        if (newLevel != null && (oldLevel == null || !newLevel.equals(oldLevel))) {
          logger.info("changing level of {} to {}", classLogger.getName(), newLevel);
          classLogger.setLevel(newLevel);
        }
      }
    }
  }

  public static synchronized ImmutableMap getClassesMatching(@Nonnull String searchKey)
  {
    Pattern searchPattern = Pattern.compile(searchKey);
    Map matchedClasses = Maps.newHashMap();
    @SuppressWarnings("unchecked")
    Enumeration loggerEnumeration = LogManager.getCurrentLoggers();
    while (loggerEnumeration.hasMoreElements()) {
      Logger logger = loggerEnumeration.nextElement();
      if (searchPattern.matcher(logger.getName()).matches()) {
        Level level = logger.getLevel();
        matchedClasses.put(logger.getName(), level == null ? "" : level.toString());
      }
    }
    return ImmutableMap.copyOf(matchedClasses);
  }
}