/*
    * 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.Collection;
  import java.util.Objects;
  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.ConfigurationSource; // SUPPRESS CHECKSTYLE
  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.impl.Log4jLogEvent;
  import org.apache.logging.log4j.core.jmx.Server;
  import org.apache.logging.log4j.core.util.Cancellable;
  import org.apache.logging.log4j.core.util.NanoClockFactory;
  import org.apache.logging.log4j.core.util.NetUtils;
  import org.apache.logging.log4j.core.util.ShutdownCallbackRegistry;
  import org.apache.logging.log4j.message.MessageFactory;
  import org.apache.logging.log4j.spi.AbstractLogger;
  import org.apache.logging.log4j.spi.LoggerContextFactory;
  import org.apache.logging.log4j.spi.LoggerContextKey;
  
  import static org.apache.logging.log4j.core.util.ShutdownCallbackRegistry.*;
  
  /**
   * 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 extends AbstractLifeCycle implements org.apache.logging.log4j.spi.LoggerContext,
          ConfigurationListener {
  
      /**
       * Property name of the property change event fired if the configuration is changed.
       */
      public static final String PROPERTY_CONFIG = "config";
  
      private static final long serialVersionUID = 1L;
      private static final Configuration NULL_CONFIGURATION = new NullConfiguration();
  
      private final ConcurrentMap<String, Logger> loggers = new ConcurrentHashMap<>();
      private final CopyOnWriteArrayList<PropertyChangeListener> propertyChangeListeners = new CopyOnWriteArrayList<>();
  
      /**
       * The Configuration is volatile to guarantee that initialization of the Configuration has completed before the
       * reference is updated.
       */
      private volatile Configuration configuration = new DefaultConfiguration();
      private Object externalContext;
      private String contextName;
      private volatile URI configLocation;
      private Cancellable shutdownCallback;
  
      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.contextName = 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.contextName = 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;
         }
     }
 
     /**
      * Returns the current LoggerContext.
      * <p>
      * Avoids the type cast for:
      * </p>
      *
      * <pre>
      * (LoggerContext) LogManager.getContext();
      * </pre>
      *
      * <p>
      * WARNING - The LoggerContext returned by this method may not be the LoggerContext used to create a Logger for the
      * calling class.
      * </p>
      * 
      * @return The current LoggerContext.
      * @see LogManager#getContext()
      */
     public static LoggerContext getContext() {
         return (LoggerContext) LogManager.getContext();
     }
 
     /**
      * Returns a LoggerContext.
      * <p>
      * Avoids the type cast for:
      * </p>
      *
      * <pre>
      * (LoggerContext) LogManager.getContext(currentContext);
      * </pre>
      *
      * @param currentContext if false the LoggerContext appropriate for the caller of this method is returned. For
      *            example, in a web application if the caller is a class in WEB-INF/lib then one LoggerContext may be
      *            returned and if the caller is a class in the container's classpath then a different LoggerContext may
      *            be returned. If true then only a single LoggerContext will be returned.
      * @return a LoggerContext.
      * @see LogManager#getContext(boolean)
      */
     public static LoggerContext getContext(final boolean currentContext) {
         return (LoggerContext) LogManager.getContext(currentContext);
     }
 
     /**
      * Returns a LoggerContext.
      * <p>
      * Avoids the type cast for:
      * </p>
      *
      * <pre>
      * (LoggerContext) LogManager.getContext(loader, currentContext, configLocation);
      * </pre>
      *
      * @param loader The ClassLoader for the context. If null the context will attempt to determine the appropriate
      *            ClassLoader.
      * @param currentContext if false the LoggerContext appropriate for the caller of this method is returned. For
      *            example, in a web application if the caller is a class in WEB-INF/lib then one LoggerContext may be
      *            returned and if the caller is a class in the container's classpath then a different LoggerContext may
      *            be returned. If true then only a single LoggerContext will be returned.
      * @param configLocation The URI for the configuration to use.
      * @return a LoggerContext.
      * @see LogManager#getContext(ClassLoader, boolean, URI)
      */
     public static LoggerContext getContext(final ClassLoader loader, final boolean currentContext,
             final URI configLocation) {
         return (LoggerContext) LogManager.getContext(loader, currentContext, configLocation);
     }
 
     @Override
     public void start() {
         LOGGER.debug("Starting LoggerContext[name={}, {}]...", getName(), this);
         if (configLock.tryLock()) {
             try {
                 if (this.isInitialized() || this.isStopped()) {
                     this.setStarting();
                     reconfigure();
                     if (this.configuration.isShutdownHookEnabled()) {
                         setUpShutdownHook();
                     }
                     this.setStarted();
                 }
             } finally {
                 configLock.unlock();
             }
         }
         LOGGER.debug("LoggerContext[name={}, {}] started OK.", getName(), this);
     }
 
     /**
      * Starts with a specific configuration.
      * 
      * @param config The new Configuration.
      */
     public void start(final Configuration config) {
         LOGGER.debug("Starting LoggerContext[name={}, {}] with configuration {}...", getName(), this, config);
         if (configLock.tryLock()) {
             try {
                 if (this.isInitialized() || this.isStopped()) {
                     if (this.configuration.isShutdownHookEnabled()) {
                         setUpShutdownHook();
                     }
                     this.setStarted();
                 }
             } finally {
                 configLock.unlock();
             }
         }
         setConfiguration(config);
         LOGGER.debug("LoggerContext[name={}, {}] started OK with configuration {}.", getName(), this, config);
     }
 
     private void setUpShutdownHook() {
         if (shutdownCallback == null) {
             final LoggerContextFactory factory = LogManager.getFactory();
             if (factory instanceof ShutdownCallbackRegistry) {
                 LOGGER.debug(SHUTDOWN_HOOK_MARKER, "Shutdown hook enabled. Registering a new one.");
                 try {
                     this.shutdownCallback = ((ShutdownCallbackRegistry) factory).addShutdownCallback(new Runnable() {
                         @Override
                         public void run() {
                             final LoggerContext context = LoggerContext.this;
                             LOGGER.debug(SHUTDOWN_HOOK_MARKER, "Stopping LoggerContext[name={}, {}]",
                                     context.getName(), context);
                             context.stop();
                         }
 
                         @Override
                         public String toString() {
                             return "Shutdown callback for LoggerContext[name=" + LoggerContext.this.getName() + ']';
                         }
                     });
                 } catch (final IllegalStateException e) {
                     LOGGER.error(SHUTDOWN_HOOK_MARKER,
                             "Unable to register shutdown hook because JVM is shutting down.", e);
                 } catch (final SecurityException e) {
                     LOGGER.error(SHUTDOWN_HOOK_MARKER, "Unable to register shutdown hook due to security restrictions",
                             e);
                 }
             }
         }
     }
 
     @Override
     public void stop() {
         LOGGER.debug("Stopping LoggerContext[name={}, {}]...", getName(), this);
         configLock.lock();
         try {
             if (this.isStopped()) {
                 return;
             }
 
             this.setStopping();
             try {
                 Server.unregisterLoggerContext(getName()); // LOG4J2-406, LOG4J2-500
             } catch (final Exception ex) {
                 LOGGER.error("Unable to unregister MBeans", ex);
             }
             if (shutdownCallback != null) {
                 shutdownCallback.cancel();
                 shutdownCallback = null;
             }
             final Configuration prev = configuration;
             configuration = NULL_CONFIGURATION;
             updateLoggers();
             prev.stop();
             externalContext = null;
             LogManager.getFactory().removeContext(this);
             this.setStopped();
         } finally {
             configLock.unlock();
         }
         LOGGER.debug("Stopped LoggerContext[name={}, {}]...", getName(), this);
     }
 
     /**
      * Gets the name.
      *
      * @return the name.
      */
     public String getName() {
         return contextName;
     }
     
     /**
      * Gets the root logger.
      * 
      * @return the root logger.
      */
     public Logger getRootLogger() {
         return getLogger(LogManager.ROOT_LOGGER_NAME);
     }
     
     /**
      * Sets the name.
      * 
      * @param name the new LoggerContext name
      * @throws NullPointerException if the specified name is {@code null}
      */
     public void setName(final String name) {
     	contextName = Objects.requireNonNull(name);
     }
 
     /**
      * Sets 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;
     }
 
     /**
      * Gets 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);
     }
 
     /**
      * Gets a collection of the current loggers.
      * <p>
      * Whether this collection is a copy of the underlying collection or not is undefined. Therefore, modify this
      * collection at your own risk.
      * </p>
      *
      * @return a collection of the current loggers.
      */
     public Collection<Logger> getLoggers() {
         return loggers.values();
     }
 
     /**
      * Obtains 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) {
         // Note: This is the only method where we add entries to the 'loggers' ivar. 
         // The loggers map key is the logger name plus the messageFactory FQCN.
         String key = LoggerContextKey.create(name, messageFactory);
         Logger logger = loggers.get(key);
         if (logger != null) {
             AbstractLogger.checkMessageFactory(logger, messageFactory);
             return logger;
         }
 
         logger = newInstance(this, name, messageFactory);
         // If messageFactory was null then we need to pull it out of the logger now
         key = LoggerContextKey.create(name, logger.getMessageFactory());
         final Logger prev = loggers.putIfAbsent(key, logger);
         return prev == null ? logger : prev;
     }
 
     /**
      * Determines 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(LoggerContextKey.create(name));
     }
 
     /**
      * Determines 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, MessageFactory messageFactory) {
         return loggers.containsKey(LoggerContextKey.create(name, messageFactory));
     }
 
     /**
      * Determines 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, Class<? extends MessageFactory> messageFactoryClass) {
         return loggers.containsKey(LoggerContextKey.create(name, messageFactoryClass));
     }
 
     /**
      * Returns the current Configuration. The Configuration will be replaced when a reconfigure occurs.
      *
      * @return The Configuration.
      */
     public Configuration getConfiguration() {
         return configuration;
     }
 
     /**
      * Adds 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) {
         configuration.addFilter(filter);
     }
 
     /**
      * Removes a Filter from the current Configuration.
      * 
      * @param filter The Filter to remove.
      */
     public void removeFilter(final Filter filter) {
         configuration.removeFilter(filter);
     }
 
     /**
      * Sets the Configuration to be used.
      * 
      * @param config The new Configuration.
      * @return The previous Configuration.
      */
     private Configuration setConfiguration(final Configuration config) {
         Objects.requireNonNull(config, "No Configuration was provided");
         configLock.lock();
         try {
             final Configuration prev = this.configuration;
             config.addListener(this);
             final ConcurrentMap<String, String> map = config.getComponent(Configuration.CONTEXT_PROPERTIES);
 
             try { // LOG4J2-719 network access may throw android.os.NetworkOnMainThreadException
                 map.putIfAbsent("hostName", NetUtils.getLocalHostname());
             } catch (final Exception ex) {
                 LOGGER.debug("Ignoring {}, setting hostName to 'unknown'", ex.toString());
                 map.putIfAbsent("hostName", "unknown");
             }
             map.putIfAbsent("contextName", contextName);
             config.start();
             this.configuration = config;
             updateLoggers();
             if (prev != null) {
                 prev.removeListener(this);
                 prev.stop();
             }
 
             firePropertyChangeEvent(new PropertyChangeEvent(this, PROPERTY_CONFIG, prev, config));
 
             try {
                 Server.reregisterMBeansAfterReconfigure();
             } catch (final Throwable t) {
                 // LOG4J2-716: Android has no java.lang.management
                 LOGGER.error("Could not reconfigure JMX", t);
             }
             // AsyncLoggers update their nanoClock when the configuration changes
             Log4jLogEvent.setNanoClock(NanoClockFactory.createNanoClock());
             
             return prev;
         } finally {
             configLock.unlock();
         }
     }
 
     private void firePropertyChangeEvent(final PropertyChangeEvent event) {
         for (final PropertyChangeListener listener : propertyChangeListeners) {
             listener.propertyChange(event);
         }
     }
 
     public void addPropertyChangeListener(final PropertyChangeListener listener) {
         propertyChangeListeners.add(Objects.requireNonNull(listener, "listener"));
     }
 
     public void removePropertyChangeListener(final PropertyChangeListener listener) {
         propertyChangeListeners.remove(listener);
     }
 
     /**
      * Returns the initial configuration location or {@code null}. The returned value may not be the location of the
      * current configuration. Use {@link #getConfiguration()}.{@link Configuration#getConfigurationSource()
      * getConfigurationSource()}.{@link ConfigurationSource#getLocation() getLocation()} to get the actual source of the
      * current configuration.
      * 
      * @return the initial configuration location or {@code null}
      */
     public URI getConfigLocation() {
         return configLocation;
     }
 
     /**
      * Sets the configLocation to the specified value and reconfigures this context.
      * 
      * @param configLocation the location of the new configuration
      */
     public void setConfigLocation(final URI configLocation) {
         this.configLocation = configLocation;
 
         reconfigure(configLocation);
     }
 
     /**
      * Reconfigures the context.
      */
     private void reconfigure(final URI configURI) {
         final ClassLoader cl = ClassLoader.class.isInstance(externalContext) ? (ClassLoader) externalContext : null;
         LOGGER.debug("Reconfiguration started for context[name={}] at URI {} ({}) with optional ClassLoader: {}",
                 contextName, configURI, this, cl);
         final Configuration instance = ConfigurationFactory.getInstance().getConfiguration(contextName, configURI, cl);
         setConfiguration(instance);
         /*
          * instance.start(); Configuration old = setConfiguration(instance); updateLoggers(); if (old != null) {
          * old.stop(); }
          */
         final String location = configuration == null ? "?" : String.valueOf(configuration.getConfigurationSource());
         LOGGER.debug("Reconfiguration complete for context[name={}] at URI {} ({}) with optional ClassLoader: {}",
                 contextName, location, this, cl);
     }
 
     /**
      * Reconfigures the context. Log4j does not remove Loggers during a reconfiguration. Log4j will create new
      * LoggerConfig objects and Log4j will point the Loggers at the new LoggerConfigs. Log4j will free the old
      * LoggerConfig, along with old Appenders and Filters.
      */
     public void reconfigure() {
         reconfigure(configLocation);
     }
 
     /**
      * Causes all Loggers to be updated against the current Configuration.
      */
     public void updateLoggers() {
         updateLoggers(this.configuration);
     }
 
     /**
      * Causes 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);
         }
     }
 
     /**
      * Causes 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 {} ({})", contextName, this);
         final Configuration newConfig = reconfigurable.reconfigure();
         if (newConfig != null) {
             setConfiguration(newConfig);
             LOGGER.debug("Reconfiguration completed for {} ({})", contextName, this);
         } else {
             LOGGER.debug("Reconfiguration failed for {} ({})", contextName, this);
         }
     }
 
     // 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);
     }
 
 }