/*
    * 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.appender;
  
  import org.apache.logging.log4j.Logger;
  import org.apache.logging.log4j.core.Appender;
  import org.apache.logging.log4j.core.ErrorHandler;
  import org.apache.logging.log4j.core.Filter;
  import org.apache.logging.log4j.core.Layout;
  import org.apache.logging.log4j.core.LifeCycle;
  import org.apache.logging.log4j.core.LogEvent;
  import org.apache.logging.log4j.core.filter.AbstractFilterable;
  import org.apache.logging.log4j.status.StatusLogger;
  
  import java.io.Serializable;
  
  /**
   * Abstract base class for Appenders. Although Appenders do not have to extend this class, doing so
   * will simplify their implementation.
   *
   * @param <T> The {@link Layout}'s {@link Serializable} type.
   */
  public abstract class AbstractAppender<T extends Serializable> extends AbstractFilterable
      implements Appender<T>, LifeCycle {
      /**
       * Allow subclasses access to the status logger without creating another instance.
       */
      protected static final Logger LOGGER = StatusLogger.getLogger();
  
      /**
       * Appenders set this by calling super.start().
       */
      private boolean started = false;
  
      private final Layout<T> layout;
  
      private final String name;
  
      private final boolean handleException;
  
      private ErrorHandler handler = new DefaultErrorHandler(this);
  
      /**
       * Constructor that defaults to suppressing exceptions.
       * @param name The Appender name.
       * @param filter The Filter to associate with the Appender.
       * @param layout The layout to use to format the event.
       */
      protected AbstractAppender(final String name, final Filter filter, final Layout<T> layout) {
          this(name, filter, layout, true);
      }
  
      /**
       * Constructor.
       * @param name The Appender name.
       * @param filter The Filter to associate with the Appender.
       * @param layout The layout to use to format the event.
       * @param handleException If true, exceptions will be logged and suppressed. If false errors will be
       * logged and then passed to the application.
       */
      protected AbstractAppender(final String name, final Filter filter, final Layout<T> layout,
                                 final boolean handleException) {
          super(filter);
          this.name = name;
          this.layout = layout;
          this.handleException = handleException;
      }
  
      /**
       * Returns the ErrorHandler, if any.
       * @return The ErrorHandler.
       */
      @Override
      public ErrorHandler getHandler() {
          return handler;
      }
  
      /**
       * The handler must be set before the appender is started.
       * @param handler The ErrorHandler to use.
       */
      @Override
      public void setHandler(final ErrorHandler handler) {
          if (handler == null) {
              LOGGER.error("The handler cannot be set to null");
         }
         if (isStarted()) {
             LOGGER.error("The handler cannot be changed once the appender is started");
             return;
         }
         this.handler = handler;
     }
 
     /**
      * Close the stream associated with the Appender.
      */
     public void close() {
 
     }
 
     /**
      * Returns the name of the Appender.
      * @return The name of the Appender.
      */
     @Override
     public String getName() {
         return name;
     }
 
     /**
      * Returns the Layout for the appender.
      * @return The Layout used to format the event.
      */
     @Override
     public Layout<T> getLayout() {
         return layout;
     }
 
     /**
      * Some appenders need to propagate exceptions back to the application. When suppressException is false the
      * AppenderControl will allow the exception to percolate.
      * @return true if exceptions will be suppressed, false otherwise.
      */
     @Override
     public boolean isExceptionSuppressed() {
         return handleException;
     }
 
     /**
      * Start the Appender.
      */
     @Override
     public void start() {
         startFilter();
         this.started = true;
     }
 
     /**
      * Stop the Appender.
      */
     @Override
     public void stop() {
         this.started = false;
         stopFilter();
     }
 
     /**
      * Returns true if the Appender is started, false otherwise.
      * @return true if the Appender is started, false otherwise.
      */
     @Override
     public boolean isStarted() {
         return started;
     }
 
     @Override
     public String toString() {
         return name;
     }
 
     /**
      * Handle an error with a message.
      * @param msg The message.
      */
     public void error(final String msg) {
         handler.error(msg);
     }
 
     /**
      * Handle an error with a message and an exception.
      * @param msg The message.
      * @param t The Throwable.
      */
     public void error(final String msg, final Throwable t) {
         handler.error(msg, t);
     }
 
     /**
      * Handle an error with a message, and exception and a logging event.
      * @param msg The message.
      * @param event The LogEvent.
      * @param t The Throwable.
      */
     public void error(final String msg, final LogEvent event, final Throwable t) {
         handler.error(msg, event, t);
     }
 
 }