/*
    * 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 org.apache.logging.log4j.util.PerformanceSensitive;
  import org.apache.logging.log4j.util.ReadOnlyStringMap;
  import org.apache.logging.log4j.core.LogEvent;
  import org.apache.logging.log4j.core.config.plugins.Plugin;
  import org.apache.logging.log4j.core.util.Constants;
  import org.apache.logging.log4j.util.TriConsumer;
  import org.apache.logging.log4j.util.StringBuilders;
  
  /**
   * 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" })
  @PerformanceSensitive("allocation")
  public final class MdcPatternConverter extends LogEventPatternConverter {
  
      private static final ThreadLocal<StringBuilder> threadLocal = new ThreadLocal<>();
      private static final int DEFAULT_STRING_BUILDER_SIZE = 64;
  
      /**
       * Name of property to output.
       */
      private final String key;
      private final String[] keys;
      private final boolean full;
  
      /**
       * Private constructor.
       *
       * @param options options, may be null.
       */
      private MdcPatternConverter(final String[] options) {
          super(options != null && options.length > 0 ? "MDC{" + options[0] + '}' : "MDC", "mdc");
          if (options != null && options.length > 0) {
              full = false;
              if (options[0].indexOf(',') > 0) {
                  keys = options[0].split(",");
                  for (int i = 0; i < keys.length; i++) {
                      keys[i] = keys[i].trim();
                  }
                  key = null;
              } else {
                  keys = null;
                  key = options[0];
              }
          } else {
              full = true;
              key = null;
              keys = 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);
      }
  
      private static final TriConsumer<String, Object, StringBuilder> WRITE_KEY_VALUES_INTO = new TriConsumer<String, Object, StringBuilder>() {
          @Override
          public void accept(final String key, final Object value, final StringBuilder sb) {
              if (sb.length() > 1) {
                  sb.append(", ");
              }
              sb.append(key).append('=');
              StringBuilders.appendValue(sb, value);
          }
      };
  
      /**
       * {@inheritDoc}
       */
      @Override
     public void format(final LogEvent event, final StringBuilder toAppendTo) {
         final ReadOnlyStringMap contextData = event.getContextData();
         // if there is no additional options, we output every single
         // Key/Value pair for the MDC in a similar format to Hashtable.toString()
         if (full) {
             if (contextData == null || contextData.size() == 0) {
                 toAppendTo.append("{}");
                 return;
             }
             appendFully(contextData, toAppendTo);
         } else {
             if (keys != null) {
                 if (contextData == null || contextData.size() == 0) {
                     toAppendTo.append("{}");
                     return;
                 }
                 appendSelectedKeys(keys, contextData, toAppendTo);
             } else if (contextData != null){
                 // otherwise they just want a single key output
                 final Object value = contextData.getValue(key);
                 if (value != null) {
                     StringBuilders.appendValue(toAppendTo, value);
                 }
             }
         }
     }
 
     private static void appendFully(final ReadOnlyStringMap contextData, final StringBuilder toAppendTo) {
         final StringBuilder sb = getStringBuilder();
         sb.append("{");
         contextData.forEach(WRITE_KEY_VALUES_INTO, sb);
         sb.append('}');
         toAppendTo.append(sb);
         trimToMaxSize(sb);
     }
 
     private static void appendSelectedKeys(final String[] keys, final ReadOnlyStringMap contextData, final StringBuilder toAppendTo) {
         // Print all the keys in the array that have a value.
         final StringBuilder sb = getStringBuilder();
         sb.append("{");
         for (int i = 0; i < keys.length; i++) {
             final String theKey = keys[i];
             final Object value = contextData.getValue(theKey);
             if (value != null) { // !contextData.containskey(theKey)
                 if (sb.length() > 1) {
                     sb.append(", ");
                 }
                 sb.append(theKey).append('=');
                 StringBuilders.appendValue(sb, value);
             }
         }
         sb.append('}');
         toAppendTo.append(sb);
         trimToMaxSize(sb);
     }
 
     private static StringBuilder getStringBuilder() {
         StringBuilder result = threadLocal.get();
         if (result == null) {
             result = new StringBuilder(DEFAULT_STRING_BUILDER_SIZE);
             threadLocal.set(result);
         }
         result.setLength(0);
         return result;
     }
 
     private static void trimToMaxSize(final StringBuilder stringBuilder) {
         StringBuilders.trimToMaxSize(stringBuilder, Constants.MAX_REUSABLE_MESSAGE_SIZE);
     }
 }