/*
    * 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 org.apache.logging.log4j.status.StatusLogger;
  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<>();
  
      abstract String getThreadName();
  
      public static ThreadNameCachingStrategy create() {
          final String defaultStrategy = System.getProperty("java.version").compareTo("1.8.0_102") < 0
                  ? "CACHED" // LOG4J2-2052 JDK 8u102 removed the String allocation in Thread.getName()
                  : "UNCACHED";
          final String name = PropertiesUtil.getProperties().getStringProperty("AsyncLogger.ThreadNameStrategy");
          try {
              final ThreadNameCachingStrategy result = ThreadNameCachingStrategy.valueOf(
                      name != null ? name : defaultStrategy);
              LOGGER.debug("AsyncLogger.ThreadNameStrategy={} (user specified {}, default is {})",
                      result, name, defaultStrategy);
              return result;
          } catch (final Exception ex) {
              LOGGER.debug("Using AsyncLogger.ThreadNameStrategy.{}: '{}' not valid: {}",
                      defaultStrategy, name, ex.toString());
              return ThreadNameCachingStrategy.valueOf(defaultStrategy);
          }
      }
  }