/*
    * 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.taglib;
  
  import java.util.WeakHashMap;
  
  import javax.servlet.ServletContext;
  
  import org.apache.logging.log4j.LogManager;
  import org.apache.logging.log4j.message.MessageFactory;
  import org.apache.logging.log4j.spi.AbstractLogger;
  import org.apache.logging.log4j.spi.ExtendedLogger;
  import org.apache.logging.log4j.spi.LoggerContext;
  import org.apache.logging.log4j.spi.LoggerRegistry;
  
  /**
   * This bridge between the tag library and the Log4j API ensures that instances of {@link Log4jTaglibLogger} are
   * appropriately held in memory and not constantly recreated.
   *
   * @since 2.0
   */
  final class Log4jTaglibLoggerContext implements LoggerContext {
      // These were change to WeakHashMaps to avoid ClassLoader (memory) leak, something that's particularly
      // important in Servlet containers.
      private static final WeakHashMap<ServletContext, Log4jTaglibLoggerContext> CONTEXTS = new WeakHashMap<>();
  
      private final LoggerRegistry<Log4jTaglibLogger> loggerRegistry = new LoggerRegistry<>(
              new LoggerRegistry.WeakMapFactory<Log4jTaglibLogger>());
  
      private final ServletContext servletContext;
  
      private Log4jTaglibLoggerContext(final ServletContext servletContext) {
          this.servletContext = servletContext;
      }
  
      @Override
      public Object getExternalContext() {
          return this.servletContext;
      }
  
      @Override
      public Log4jTaglibLogger getLogger(final String name) {
          return this.getLogger(name, null);
      }
  
      @Override
      public Log4jTaglibLogger getLogger(final String name, final MessageFactory messageFactory) {
          // Note: This is the only method where we add entries to the 'loggerRegistry' ivar.
          Log4jTaglibLogger logger = this.loggerRegistry.getLogger(name, messageFactory);
          if (logger != null) {
              AbstractLogger.checkMessageFactory(logger, messageFactory);
              return logger;
          }
  
          synchronized (this.loggerRegistry) {
              logger = this.loggerRegistry.getLogger(name, messageFactory);
              if (logger == null) {
                  final LoggerContext context = LogManager.getContext(false);
                  final ExtendedLogger original = messageFactory == null ?
                          context.getLogger(name) : context.getLogger(name, messageFactory);
                  // wrap a logger from an underlying implementation
                  logger = new Log4jTaglibLogger(original, name, original.getMessageFactory());
                  this.loggerRegistry.putIfAbsent(name, messageFactory, logger);
              }
          }
  
          return logger;
      }
  
      @Override
      public boolean hasLogger(final String name) {
          return loggerRegistry.hasLogger(name);
      }
  
      @Override
      public boolean hasLogger(final String name, final MessageFactory messageFactory) {
          return loggerRegistry.hasLogger(name, messageFactory);
      }
  
      @Override
      public boolean hasLogger(final String name, final Class<? extends MessageFactory> messageFactoryClass) {
          return loggerRegistry.hasLogger(name, messageFactoryClass);
      }
  
      static synchronized Log4jTaglibLoggerContext getInstance(final ServletContext servletContext) {
         Log4jTaglibLoggerContext loggerContext = CONTEXTS.get(servletContext);
         if (loggerContext != null) {
             return loggerContext;
         }
 
         synchronized (CONTEXTS) {
             loggerContext = CONTEXTS.get(servletContext);
             if (loggerContext == null) {
                 loggerContext = new Log4jTaglibLoggerContext(servletContext);
                 CONTEXTS.put(servletContext, loggerContext);
             }
         }
 
         return loggerContext;
     }
 }