/*
    * 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;
  
  import java.beans.PropertyChangeEvent;
  import java.beans.PropertyChangeListener;
  import java.io.File;
  import java.net.URI;
  import java.util.HashMap;
  import java.util.Map;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentMap;
  import java.util.concurrent.CopyOnWriteArrayList;
  import java.util.concurrent.locks.Lock;
  import java.util.concurrent.locks.ReentrantLock;
  
  import org.apache.logging.log4j.LogManager;
  import org.apache.logging.log4j.core.config.Configuration;
  import org.apache.logging.log4j.core.config.ConfigurationFactory;
  import org.apache.logging.log4j.core.config.ConfigurationListener;
  import org.apache.logging.log4j.core.config.DefaultConfiguration;
  import org.apache.logging.log4j.core.config.NullConfiguration;
  import org.apache.logging.log4j.core.config.Reconfigurable;
  import org.apache.logging.log4j.core.helpers.Assert;
  import org.apache.logging.log4j.core.helpers.NetUtils;
  import org.apache.logging.log4j.message.MessageFactory;
  import org.apache.logging.log4j.spi.AbstractLogger;
  import org.apache.logging.log4j.status.StatusLogger;
  
  /**
   * The LoggerContext is the anchor for the logging system. It maintains a list
   * of all the loggers requested by applications and a reference to the
   * Configuration. The Configuration will contain the configured loggers,
   * appenders, filters, etc and will be atomically updated whenever a reconfigure
   * occurs.
   */
  public class LoggerContext implements org.apache.logging.log4j.spi.LoggerContext, ConfigurationListener, LifeCycle {
  
      public static final String PROPERTY_CONFIG = "config";
      private static final StatusLogger LOGGER = StatusLogger.getLogger();
  
      private final ConcurrentMap<String, Logger> loggers = new ConcurrentHashMap<String, Logger>();
      private final CopyOnWriteArrayList<PropertyChangeListener> propertyChangeListeners = new CopyOnWriteArrayList<PropertyChangeListener>();
  
      /**
       * The Configuration is volatile to guarantee that initialization of the
       * Configuration has completed before the reference is updated.
       */
      private volatile Configuration config = new DefaultConfiguration();
      private Object externalContext;
      private final String name;
      private URI configLocation;
  
      private ShutdownThread shutdownThread = null;
  
      /**
       * Status of the LoggerContext.
       */
      public enum Status {
          /** Initialized but not yet started. */
          INITIALIZED,
          /** In the process of starting. */
          STARTING,
          /** Is active. */
          STARTED,
          /** Shutdown is in progress. */
          STOPPING,
          /** Has shutdown. */
          STOPPED
      }
  
      private volatile Status status = Status.INITIALIZED;
  
      private final Lock configLock = new ReentrantLock();
  
      /**
       * Constructor taking only a name.
       * @param name The context name.
       */
      public LoggerContext(final String name) {
          this(name, null, (URI) null);
      }
  
      /**
       * Constructor taking a name and a reference to an external context.
      * @param name The context name.
      * @param externalContext The external context.
      */
     public LoggerContext(final String name, final Object externalContext) {
         this(name, externalContext, (URI) null);
     }
 
     /**
      * Constructor taking a name, external context and a configuration URI.
      * @param name The context name.
      * @param externalContext The external context.
      * @param configLocn The location of the configuration as a URI.
      */
     public LoggerContext(final String name, final Object externalContext, final URI configLocn) {
         this.name = name;
         this.externalContext = externalContext;
         this.configLocation = configLocn;
     }
 
     /**
      * Constructor taking a name external context and a configuration location
      * String. The location must be resolvable to a File.
      *
      * @param name The configuration location.
      * @param externalContext The external context.
      * @param configLocn The configuration location.
      */
     public LoggerContext(final String name, final Object externalContext, final String configLocn) {
         this.name = name;
         this.externalContext = externalContext;
         if (configLocn != null) {
             URI uri;
             try {
                 uri = new File(configLocn).toURI();
             } catch (final Exception ex) {
                 uri = null;
             }
             configLocation = uri;
         } else {
             configLocation = null;
         }
     }
 
     @Override
     public void start() {
         if (configLock.tryLock()) {
             try {
                 if ((status == Status.INITIALIZED || status == Status.STOPPED)) {
                     status = Status.STARTING;
                     reconfigure();
                     if (config.isShutdownHookEnabled()) {
                         shutdownThread = new ShutdownThread(this);
                         try {
                             Runtime.getRuntime().addShutdownHook(shutdownThread);
                         } catch (final IllegalStateException ise) {
                             LOGGER.warn("Unable to register shutdown hook due to JVM state");
                             shutdownThread = null;
                         } catch (final SecurityException se) {
                             LOGGER.warn("Unable to register shutdown hook due to security restrictions");
                             shutdownThread = null;
                         }
                     }
                     status = Status.STARTED;
                 }
             } finally {
                 configLock.unlock();
             }
         }
     }
 
     /**
      * Start with a specific configuration.
      * @param config The new Configuration.
      */
     public void start(final Configuration config) {
         if (configLock.tryLock()) {
             try {
                 if ((status == Status.INITIALIZED || status == Status.STOPPED) && config.isShutdownHookEnabled() ) {
                     shutdownThread = new ShutdownThread(this);
                     try {
                         Runtime.getRuntime().addShutdownHook(shutdownThread);
                     } catch (final IllegalStateException ise) {
                         LOGGER.warn("Unable to register shutdown hook due to JVM state");
                         shutdownThread = null;
                     } catch (final SecurityException se) {
                         LOGGER.warn("Unable to register shutdown hook due to security restrictions");
                         shutdownThread = null;
                     }
                     status = Status.STARTED;
                 }
             } finally {
                 configLock.unlock();
             }
         }
         setConfiguration(config);
     }
 
     @Override
     public void stop() {
         configLock.lock();
         try {
             if (status == Status.STOPPED) {
                 return;
             }
             status = Status.STOPPING;
             if (shutdownThread != null) {
                 Runtime.getRuntime().removeShutdownHook(shutdownThread);
                 shutdownThread = null;
             }
             final Configuration prev = config;
             config = new NullConfiguration();
             updateLoggers();
             prev.stop();
             externalContext = null;
             LogManager.getFactory().removeContext(this);
             status = Status.STOPPED;
         } finally {
             configLock.unlock();
         }
     }
 
     /**
      * Gets the name.
      *
      * @return the name.
      */
     public String getName() {
         return name;
     }
 
     public Status getStatus() {
         return status;
     }
 
     @Override
     public boolean isStarted() {
         return status == Status.STARTED;
     }
 
     /**
      * Set the external context.
      * @param context The external context.
      */
     public void setExternalContext(final Object context) {
         this.externalContext = context;
     }
 
     /**
      * Returns the external context.
      * @return The external context.
      */
     @Override
     public Object getExternalContext() {
         return this.externalContext;
     }
 
     /**
      * Obtain a Logger from the Context.
      * @param name The name of the Logger to return.
      * @return The Logger.
      */
     @Override
     public Logger getLogger(final String name) {
         return getLogger(name, null);
     }
 
     /**
      * Obtain a Logger from the Context.
      * @param name The name of the Logger to return.
      * @param messageFactory The message factory is used only when creating a
      *            logger, subsequent use does not change the logger but will log
      *            a warning if mismatched.
      * @return The Logger.
      */
     @Override
     public Logger getLogger(final String name, final MessageFactory messageFactory) {
         Logger logger = loggers.get(name);
         if (logger != null) {
             AbstractLogger.checkMessageFactory(logger, messageFactory);
             return logger;
         }
 
         logger = newInstance(this, name, messageFactory);
         final Logger prev = loggers.putIfAbsent(name, logger);
         return prev == null ? logger : prev;
     }
 
     /**
      * Determine if the specified Logger exists.
      * @param name The Logger name to search for.
      * @return True if the Logger exists, false otherwise.
      */
     @Override
     public boolean hasLogger(final String name) {
         return loggers.containsKey(name);
     }
 
     /**
      * Returns the current Configuration. The Configuration will be replaced
      * when a reconfigure occurs.
      *
      * @return The Configuration.
      */
     public Configuration getConfiguration() {
         return config;
     }
 
     /**
      * Add a Filter to the Configuration. Filters that are added through the API will be lost
      * when a reconfigure occurs.
      * @param filter The Filter to add.
      */
     public void addFilter(final Filter filter) {
         config.addFilter(filter);
     }
 
     /**
      * Removes a Filter from the current Configuration.
      * @param filter The Filter to remove.
      */
     public void removeFilter(final Filter filter) {
         config.removeFilter(filter);
     }
 
     /**
      * Set the Configuration to be used.
      * @param config The new Configuration.
      * @return The previous Configuration.
      */
     private synchronized Configuration setConfiguration(final Configuration config) {
         if (config == null) {
             throw new NullPointerException("No Configuration was provided");
         }
         final Configuration prev = this.config;
         config.addListener(this);
         final Map<String, String> map = new HashMap<String, String>();
         map.put("hostName", NetUtils.getLocalHostname());
         map.put("contextName", name);
         config.addComponent(Configuration.CONTEXT_PROPERTIES, map);
         config.start();
         this.config = config;
         updateLoggers();
         if (prev != null) {
             prev.removeListener(this);
             prev.stop();
         }
 
         // notify listeners
         final PropertyChangeEvent evt = new PropertyChangeEvent(this, PROPERTY_CONFIG, prev, config);
         for (final PropertyChangeListener listener : propertyChangeListeners) {
             listener.propertyChange(evt);
         }
         return prev;
     }
 
     public void addPropertyChangeListener(final PropertyChangeListener listener) {
         propertyChangeListeners.add(Assert.isNotNull(listener, "listener"));
     }
 
     public void removePropertyChangeListener(final PropertyChangeListener listener) {
         propertyChangeListeners.remove(listener);
     }
 
     public synchronized URI getConfigLocation() {
         return configLocation;
     }
 
     public synchronized void setConfigLocation(final URI configLocation) {
         this.configLocation = configLocation;
         reconfigure();
     }
 
     /**
      * Reconfigure the context.
      */
     public synchronized void reconfigure() {
         LOGGER.debug("Reconfiguration started for context " + name);
         final Configuration instance = ConfigurationFactory.getInstance().getConfiguration(name, configLocation);
         setConfiguration(instance);
         /*
          * instance.start(); Configuration old = setConfiguration(instance);
          * updateLoggers(); if (old != null) { old.stop(); }
          */
         LOGGER.debug("Reconfiguration completed");
     }
 
     /**
      * Cause all Loggers to be updated against the current Configuration.
      */
     public void updateLoggers() {
         updateLoggers(this.config);
     }
 
     /**
      * Cause all Logger to be updated against the specified Configuration.
      * @param config The Configuration.
      */
     public void updateLoggers(final Configuration config) {
         for (final Logger logger : loggers.values()) {
             logger.updateConfiguration(config);
         }
     }
 
     /**
      * Cause a reconfiguration to take place when the underlying configuration
      * file changes.
      *
      * @param reconfigurable The Configuration that can be reconfigured.
      */
     @Override
     public synchronized void onChange(final Reconfigurable reconfigurable) {
         LOGGER.debug("Reconfiguration started for context " + name);
         final Configuration config = reconfigurable.reconfigure();
         if (config != null) {
             setConfiguration(config);
             LOGGER.debug("Reconfiguration completed");
         } else {
             LOGGER.debug("Reconfiguration failed");
         }
     }
 
     // LOG4J2-151: changed visibility from private to protected
     protected Logger newInstance(final LoggerContext ctx, final String name, final MessageFactory messageFactory) {
         return new Logger(ctx, name, messageFactory);
     }
 
     private class ShutdownThread extends Thread {
 
         private final LoggerContext context;
 
         public ShutdownThread(final LoggerContext context) {
             this.context = context;
         }
 
         @Override
         public void run() {
             context.shutdownThread = null;
             context.stop();
         }
     }
 
 }