/*
    * 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.rewrite;
  
  import java.util.HashMap;
  import java.util.Map;
  
  import org.apache.logging.log4j.Logger;
  import org.apache.logging.log4j.core.Core;
  import org.apache.logging.log4j.core.LogEvent;
  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.impl.Log4jLogEvent;
  import org.apache.logging.log4j.core.util.KeyValuePair;
  import org.apache.logging.log4j.message.MapMessage;
  import org.apache.logging.log4j.message.Message;
  import org.apache.logging.log4j.status.StatusLogger;
  
  /**
   * This policy modifies events by replacing or possibly adding keys and values to the MapMessage.
   */
  @Plugin(name = "MapRewritePolicy", category = Core.CATEGORY_NAME, elementType = "rewritePolicy", printObject = true)
  public final class MapRewritePolicy implements RewritePolicy {
      /**
       * Allow subclasses access to the status logger without creating another instance.
       */
      protected static final Logger LOGGER = StatusLogger.getLogger();
  
      private final Map<String, Object> map;
  
      private final Mode mode;
  
      private MapRewritePolicy(final Map<String, Object> map, final Mode mode) {
          this.map = map;
          this.mode = mode;
      }
  
      /**
       * Rewrite the event.
       * @param source a logging event that may be returned or
       * used to create a new logging event.
       * @return The LogEvent after rewriting.
       */
      @Override
      public LogEvent rewrite(final LogEvent source) {
          final Message msg = source.getMessage();
          if (msg == null || !(msg instanceof MapMessage)) {
              return source;
          }
  
          @SuppressWarnings("unchecked")
          final MapMessage<?, Object> mapMsg = (MapMessage<?, Object>) msg;
          final Map<String, Object> newMap = new HashMap<>(mapMsg.getData());
          switch (mode) {
              case Add: {
                  newMap.putAll(map);
                  break;
              }
              default: {
                  for (final Map.Entry<String, Object> entry : map.entrySet()) {
                      if (newMap.containsKey(entry.getKey())) {
                          newMap.put(entry.getKey(), entry.getValue());
                      }
                  }
              }
          }
          final Message message = mapMsg.newInstance(newMap);
          final LogEvent result = new Log4jLogEvent.Builder(source).setMessage(message).build();
          return result;
      }
  
      /**
       * An enumeration to identify whether keys not in the MapMessage should be added or whether only existing
       * keys should be updated.
       */
      public enum Mode {
          /**
           * Keys should be added.
           */
          Add,
          /**
           * Keys should be updated.
           */
         Update
     }
 
     @Override
     public String toString() {
         final StringBuilder sb = new StringBuilder();
         sb.append("mode=").append(mode);
         sb.append(" {");
         boolean first = true;
         for (final Map.Entry<String, Object> entry : map.entrySet()) {
             if (!first) {
                 sb.append(", ");
             }
             sb.append(entry.getKey()).append('=').append(entry.getValue());
             first = false;
         }
         sb.append('}');
         return sb.toString();
     }
 
     /**
      * The factory method to create the MapRewritePolicy.
      * @param mode The string representation of the Mode.
      * @param pairs key/value pairs for the new Map keys and values.
      * @return The MapRewritePolicy.
      */
     @PluginFactory
     public static MapRewritePolicy createPolicy(
             @PluginAttribute("mode") final String mode,
             @PluginElement("KeyValuePair") final KeyValuePair[] pairs) {
         Mode op = mode == null ? op = Mode.Add : Mode.valueOf(mode);
         if (pairs == null || pairs.length == 0) {
             LOGGER.error("keys and values must be specified for the MapRewritePolicy");
             return null;
         }
         final Map<String, Object> map = new HashMap<>();
         for (final KeyValuePair pair : pairs) {
             final String key = pair.getKey();
             if (key == null) {
                 LOGGER.error("A null key is not valid in MapRewritePolicy");
                 continue;
             }
             final String value = pair.getValue();
             if (value == null) {
                 LOGGER.error("A null value for key " + key + " is not allowed in MapRewritePolicy");
                 continue;
             }
             map.put(pair.getKey(), pair.getValue());
         }
         if (map.isEmpty()) {
             LOGGER.error("MapRewritePolicy is not configured with any valid key value pairs");
             return null;
         }
         return new MapRewritePolicy(map, op);
     }
 }