/*
    * 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.mom.kafka;
  
  import java.io.Serializable;
  import java.nio.charset.StandardCharsets;
  
  import org.apache.logging.log4j.core.Appender;
  import org.apache.logging.log4j.core.Filter;
  import org.apache.logging.log4j.core.Layout;
  import org.apache.logging.log4j.core.LogEvent;
  import org.apache.logging.log4j.core.appender.AbstractAppender;
  import org.apache.logging.log4j.core.appender.AppenderLoggingException;
  import org.apache.logging.log4j.core.config.Node;
  import org.apache.logging.log4j.core.config.Property;
  import org.apache.logging.log4j.core.config.plugins.Plugin;
  import org.apache.logging.log4j.core.config.plugins.PluginAttribute;
  import org.apache.logging.log4j.core.config.plugins.PluginElement;
  import org.apache.logging.log4j.core.config.plugins.PluginFactory;
  import org.apache.logging.log4j.core.config.plugins.validation.constraints.Required;
  import org.apache.logging.log4j.core.layout.SerializedLayout;
  import org.apache.logging.log4j.core.util.StringEncoder;
  
  /**
   * Sends log events to an Apache Kafka topic.
   */
  @Plugin(name = "Kafka", category = Node.CATEGORY, elementType = Appender.ELEMENT_TYPE, printObject = true)
  public final class KafkaAppender extends AbstractAppender {
  
      @PluginFactory
      public static KafkaAppender createAppender(
              @PluginElement("Layout") final Layout<? extends Serializable> layout,
              @PluginElement("Filter") final Filter filter,
              @Required(message = "No name provided for KafkaAppender") @PluginAttribute("name") final String name,
              @PluginAttribute(value = "ignoreExceptions", defaultBoolean = true) final boolean ignoreExceptions,
              @Required(message = "No topic provided for KafkaAppender") @PluginAttribute("topic") final String topic,
              @PluginElement("Properties") final Property[] properties) {
          final KafkaManager kafkaManager = new KafkaManager(name, topic, properties);
          return new KafkaAppender(name, layout, filter, ignoreExceptions, kafkaManager);
      }
  
      private final KafkaManager manager;
  
      private KafkaAppender(final String name, final Layout<? extends Serializable> layout, final Filter filter, final boolean ignoreExceptions, final KafkaManager manager) {
          super(name, filter, layout, ignoreExceptions);
          this.manager = manager;
      }
  
      @Override
      public void append(final LogEvent event) {
          if (event.getLoggerName().startsWith("org.apache.kafka")) {
              LOGGER.warn("Recursive logging from [{}] for appender [{}].", event.getLoggerName(), getName());
          } else {
              try {
                  final Layout<? extends Serializable> layout = getLayout();
                  byte[] data;
                  if (layout != null) {
                      if (layout instanceof SerializedLayout) {
                          final byte[] header = layout.getHeader();
                          final byte[] body = layout.toByteArray(event);
                          data = new byte[header.length + body.length];
                          System.arraycopy(header, 0, data, 0, header.length);
                          System.arraycopy(body, 0, data, header.length, body.length);
                      } else {
                          data = layout.toByteArray(event);
                      }
                  } else {
                      data = StringEncoder.toBytes(event.getMessage().getFormattedMessage(), StandardCharsets.UTF_8);
                  }
                  manager.send(data);
              } catch (final Exception e) {
                  LOGGER.error("Unable to write to Kafka [{}] for appender [{}].", manager.getName(), getName(), e);
                  throw new AppenderLoggingException("Unable to write to Kafka in appender: " + e.getMessage(), e);
              }
          }
      }
  
      @Override
      public void start() {
          super.start();
          manager.startup();
      }
  
      @Override
     public void stop() {
         super.stop();
         manager.release();
     }
 
     @Override
     public String toString() {
         return "KafkaAppender{" +
             "name=" + getName() +
             ", state=" + getState() +
             ", topic=" + manager.getTopic() +
             '}';
     }
 }