/*
    * 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.selector;
  
  import java.net.URI;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.List;
  import java.util.Map;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentMap;
  import javax.naming.NamingException;
  
  import org.apache.logging.log4j.core.LoggerContext;
  import org.apache.logging.log4j.core.impl.ContextAnchor;
  import org.apache.logging.log4j.core.net.JndiManager;
  import org.apache.logging.log4j.core.util.Constants;
  import org.apache.logging.log4j.status.StatusLogger;
  
  /**
   * This class can be used to define a custom logger repository. It makes use of the fact that in J2EE environments, each
   * web-application is guaranteed to have its own JNDI context relative to the <code>java:comp/env</code> context. In
   * EJBs, each enterprise bean (albeit not each application) has its own context relative to the
   * <code>java:comp/env</code> context. An <code>env-entry</code> in a deployment descriptor provides the information to
   * the JNDI context. Once the <code>env-entry</code> is set, a repository selector can query the JNDI application
   * context to look up the value of the entry. The logging context of the web-application will depend on the value the
   * env-entry. The JNDI context which is looked up by this class is <code>java:comp/env/log4j/context-name</code>.
   *
   * <p>
   * Here is an example of an <code>env-entry</code>:
   * </p>
   * <blockquote>
   * 
   * <pre>
   * &lt;env-entry&gt;
   *   &lt;description&gt;JNDI logging context name for this app&lt;/description&gt;
   *   &lt;env-entry-name&gt;log4j/context-name&lt;/env-entry-name&gt;
   *   &lt;env-entry-value&gt;aDistinctiveLoggingContextName&lt;/env-entry-value&gt;
   *   &lt;env-entry-type&gt;java.lang.String&lt;/env-entry-type&gt;
   * &lt;/env-entry&gt;
   * </pre>
   * 
   * </blockquote>
   *
   * <p>
   * <em>If multiple applications use the same logging context name, then they
   * will share the same logging context.</em>
   * </p>
   *
   * <p>
   * You can also specify the URL for this context's configuration resource. This repository selector
   * (ContextJNDISelector) will use this resource to automatically configure the log4j repository.
   * </p>
   ** <blockquote>
   * 
   * <pre>
   * &lt;env-entry&gt;
   *   &lt;description&gt;URL for configuring log4j context&lt;/description&gt;
   *   &lt;env-entry-name&gt;log4j/configuration-resource&lt;/env-entry-name&gt;
   *   &lt;env-entry-value&gt;urlOfConfigurationResource&lt;/env-entry-value&gt;
   *   &lt;env-entry-type&gt;java.lang.String&lt;/env-entry-type&gt;
   * &lt;/env-entry&gt;
   * </pre>
   * 
   * </blockquote>
   *
   * <p>
   * It usually good practice for configuration resources of distinct applications to have distinct names. However, if
   * this is not possible Naming
   * </p>
   */
  public class JndiContextSelector implements NamedContextSelector {
  
      private static final LoggerContext CONTEXT = new LoggerContext("Default");
  
      private static final ConcurrentMap<String, LoggerContext> CONTEXT_MAP =
          new ConcurrentHashMap<String, LoggerContext>();
  
      private static final StatusLogger LOGGER = StatusLogger.getLogger();
  
      public JndiContextSelector() {
          if (!JndiManager.isJndiContextSelectorEnabled()) {
              throw new IllegalStateException("JNDI must be enabled by setting log4j2.enableJndiContextSelector=true");
          }
      }
 
     @Override
     public LoggerContext getContext(final String fqcn, final ClassLoader loader, final boolean currentContext) {
         return getContext(fqcn, loader, currentContext, null);
     }
 
     @Override
     public LoggerContext getContext(final String fqcn, final ClassLoader loader, final boolean currentContext,
                                     final URI configLocation) {
 
         final LoggerContext lc = ContextAnchor.THREAD_CONTEXT.get();
         if (lc != null) {
             return lc;
         }
 
         String loggingContextName = null;
 
         final JndiManager jndiManager = JndiManager.getDefaultManager();
         try {
             loggingContextName = jndiManager.lookup(Constants.JNDI_CONTEXT_NAME);
         } catch (final NamingException ne) {
             LOGGER.error("Unable to lookup {}", Constants.JNDI_CONTEXT_NAME, ne);
         } finally {
             jndiManager.release();
         }
 
         return loggingContextName == null ? CONTEXT : locateContext(loggingContextName, null, configLocation);
     }
 
     @Override
     public LoggerContext locateContext(final String name, final Object externalContext, final URI configLocation) {
         if (name == null) {
             LOGGER.error("A context name is required to locate a LoggerContext");
             return null;
         }
         if (!CONTEXT_MAP.containsKey(name)) {
             final LoggerContext ctx = new LoggerContext(name, externalContext, configLocation);
             CONTEXT_MAP.putIfAbsent(name, ctx);
         }
         return CONTEXT_MAP.get(name);
     }
 
     @Override
     public void removeContext(final LoggerContext context) {
 
         for (final Map.Entry<String, LoggerContext> entry : CONTEXT_MAP.entrySet()) {
             if (entry.getValue().equals(context)) {
                 CONTEXT_MAP.remove(entry.getKey());
             }
         }
     }
 
     @Override
     public LoggerContext removeContext(final String name) {
         return CONTEXT_MAP.remove(name);
     }
 
     @Override
     public List<LoggerContext> getLoggerContexts() {
         final List<LoggerContext> list = new ArrayList<LoggerContext>(CONTEXT_MAP.values());
         return Collections.unmodifiableList(list);
     }
 
 }