/*
    * 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.slf4j;
  
  import org.apache.logging.log4j.LogManager;
  import org.apache.logging.log4j.LoggingException;
  import org.apache.logging.log4j.spi.AbstractLoggerAdapter;
  import org.apache.logging.log4j.spi.LoggerContext;
  import org.apache.logging.log4j.status.StatusLogger;
  import org.apache.logging.log4j.util.StackLocatorUtil;
  import org.slf4j.ILoggerFactory;
  import org.slf4j.Logger;
  
  import java.util.function.Predicate;
  
  /**
   * Log4j implementation of SLF4J ILoggerFactory interface.
   */
  public class Log4jLoggerFactory extends AbstractLoggerAdapter<Logger> implements ILoggerFactory {
  
      private static final StatusLogger LOGGER = StatusLogger.getLogger();
      private static final String SLF4J_PACKAGE = "org.slf4j";
      private static final String TO_SLF4J_CONTEXT = "org.apache.logging.slf4j.SLF4JLoggerContext";
      private static final Predicate<Class<?>> CALLER_PREDICATE = clazz ->
              !AbstractLoggerAdapter.class.equals(clazz) && !clazz.getName().startsWith(SLF4J_PACKAGE);
  
      @Override
      protected Logger newLogger(final String name, final LoggerContext context) {
          final String key = Logger.ROOT_LOGGER_NAME.equals(name) ? LogManager.ROOT_LOGGER_NAME : name;
          return new Log4jLogger(validateContext(context).getLogger(key), name);
      }
  
      @Override
      protected LoggerContext getContext() {
          final Class<?> anchor = LogManager.getFactory().isClassLoaderDependent()
                  ? StackLocatorUtil.getCallerClass(Log4jLoggerFactory.class, CALLER_PREDICATE)
                  : null;
          LOGGER.trace("Log4jLoggerFactory.getContext() found anchor {}", anchor);
          return anchor == null
                  ? LogManager.getContext(false)
                  : getContext(anchor);
      }
  
      private LoggerContext validateContext(final LoggerContext context) {
          if (TO_SLF4J_CONTEXT.equals(context.getClass().getName())) {
              throw new LoggingException("log4j-slf4j-impl cannot be present with log4j-to-slf4j");
          }
          return context;
      }
  }