/*
    * 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.async;
  
  import java.util.regex.Matcher;
  import java.util.regex.Pattern;
  
  import org.apache.logging.log4j.status.StatusLogger;
  import org.apache.logging.log4j.util.Constants;
  import org.apache.logging.log4j.util.PropertiesUtil;
  
  /**
   * Strategy for deciding whether thread name should be cached or not.
   */
  public enum ThreadNameCachingStrategy { // LOG4J2-467
      CACHED {
          @Override
          public String getThreadName() {
              String result = THREADLOCAL_NAME.get();
              if (result == null) {
                  result = Thread.currentThread().getName();
                  THREADLOCAL_NAME.set(result);
              }
              return result;
          }
      },
      UNCACHED {
          @Override
          public String getThreadName() {
              return Thread.currentThread().getName();
          }
      };
  
      private static final StatusLogger LOGGER = StatusLogger.getLogger();
      private static final ThreadLocal<String> THREADLOCAL_NAME = new ThreadLocal<>();
      static final ThreadNameCachingStrategy DEFAULT_STRATEGY = isAllocatingThreadGetName() ? CACHED : UNCACHED;
  
      abstract String getThreadName();
  
      public static ThreadNameCachingStrategy create() {
          final String name = PropertiesUtil.getProperties().getStringProperty("AsyncLogger.ThreadNameStrategy");
          try {
              final ThreadNameCachingStrategy result = name != null ? ThreadNameCachingStrategy.valueOf(name) : DEFAULT_STRATEGY;
              LOGGER.debug("AsyncLogger.ThreadNameStrategy={} (user specified {}, default is {})",
                           result.name(), name, DEFAULT_STRATEGY.name());
              return result;
          } catch (final Exception ex) {
              LOGGER.debug("Using AsyncLogger.ThreadNameStrategy.{}: '{}' not valid: {}",
                           DEFAULT_STRATEGY.name(), name, ex.toString());
              return DEFAULT_STRATEGY;
          }
      }
  
      static boolean isAllocatingThreadGetName() {
          // LOG4J2-2052, LOG4J2-2635 JDK 8u102 ("1.8.0_102") removed the String allocation in Thread.getName()
          if (Constants.JAVA_MAJOR_VERSION == 8) {
              try {
                  Pattern javaVersionPattern = Pattern.compile("(\\d+)\\.(\\d+)\\.(\\d+)_(\\d+)");
                  Matcher m = javaVersionPattern.matcher(System.getProperty("java.version"));
                  if (m.matches()) {
                      return Integer.parseInt(m.group(3)) == 0 && Integer.parseInt(m.group(4)) < 102;
                  }
                  return true;
              } catch (Exception e) {
                  return true;
              }
          } else {
              return Constants.JAVA_MAJOR_VERSION < 8;
          }
      }
  }