/*
    * 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.pattern;
  
  import java.util.Map;
  import java.util.Set;
  import java.util.TreeSet;
  
  import org.apache.logging.log4j.core.LogEvent;
  import org.apache.logging.log4j.core.config.plugins.Plugin;
  
  /**
   * Able to handle the contents of the LogEvent's MDC and either
   * output the entire contents of the properties in a similar format to the
   * java.util.Hashtable.toString(), or to output the value of a specific key
   * within the property bundle
   * when this pattern converter has the option set.
   */
   @Plugin(name = "MdcPatternConverter", category = PatternConverter.CATEGORY)
  @ConverterKeys({ "X", "mdc", "MDC" })
  public final class MdcPatternConverter extends LogEventPatternConverter {
      /**
       * Name of property to output.
       */
      private final String key;
  
      /**
       * Private constructor.
       *
       * @param options options, may be null.
       */
      private MdcPatternConverter(final String[] options) {
          super(options != null && options.length > 0 ? "MDC{" + options[0] + '}' : "MDC", "mdc");
          key = options != null && options.length > 0 ? options[0] : null;
      }
  
      /**
       * Obtains an instance of PropertiesPatternConverter.
       *
       * @param options options, may be null or first element contains name of property to format.
       * @return instance of PropertiesPatternConverter.
       */
      public static MdcPatternConverter newInstance(final String[] options) {
          return new MdcPatternConverter(options);
      }
  
      /**
       * {@inheritDoc}
       */
      @Override
      public void format(final LogEvent event, final StringBuilder toAppendTo) {
          final Map<String, String> contextMap = event.getContextMap();
          // if there is no additional options, we output every single
          // Key/Value pair for the MDC in a similar format to Hashtable.toString()
          if (key == null) {
  
  
              if (contextMap == null || contextMap.isEmpty()) {
                  toAppendTo.append("{}");
                  return;
              }
              final StringBuilder sb = new StringBuilder("{");
              final Set<String> keys = new TreeSet<String>(contextMap.keySet());
              for (final String key : keys) {
                  if (sb.length() > 1) {
                      sb.append(", ");
                  }
                  sb.append(key).append('=').append(contextMap.get(key));
  
              }
              sb.append('}');
              toAppendTo.append(sb);
          } else if (contextMap != null) {
              // otherwise they just want a single key output
              final Object val = contextMap.get(key);
  
              if (val != null) {
                  toAppendTo.append(val);
              }
          }
      }
  }