/*
    * 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.List;
  
  import org.apache.logging.log4j.core.LogEvent;
  import org.apache.logging.log4j.core.appender.AbstractAppender;
  import org.apache.logging.log4j.core.config.Configuration;
  import org.apache.logging.log4j.core.config.plugins.Plugin;
  import org.apache.logging.log4j.core.layout.PatternLayout;
  import org.apache.logging.log4j.util.PerformanceSensitive;
  
  /**
   * Max length pattern converter. Limit contained text to a maximum length.
   * On invalid length the default value 100 is used (and an error message is logged).
   * If max length is greater than 20, an abbreviated text will get ellipsis ("...") appended.
   * Example usage (for email subject):
   * {@code "%maxLen{[AppName, ${hostName}, ${web:contextPath}] %p: %c{1} - %m%notEmpty{ =>%ex{short}}}{160}"}
   *
   * @author Thies Wellpott
   */
  @Plugin(name = "maxLength", category = PatternConverter.CATEGORY)
  @ConverterKeys({"maxLength", "maxLen"})
  @PerformanceSensitive("allocation")
  public final class MaxLengthConverter extends LogEventPatternConverter {
  
      /**
       * Gets an instance of the class.
       *
       * @param config  The current Configuration.
       * @param options pattern options, an array of two elements: pattern, max length (defaults to 100 on invalid value).
       * @return instance of class.
       */
      public static MaxLengthConverter newInstance(final Configuration config, final String[] options) {
          if (options.length != 2) {
              LOGGER.error("Incorrect number of options on maxLength: expected 2 received {}: {}", options.length,
                  options);
              return null;
          }
          if (options[0] == null) {
              LOGGER.error("No pattern supplied on maxLength");
              return null;
          }
          if (options[1] == null) {
              LOGGER.error("No length supplied on maxLength");
              return null;
          }
          final PatternParser parser = PatternLayout.createPatternParser(config);
          final List<PatternFormatter> formatters = parser.parse(options[0]);
          return new MaxLengthConverter(formatters, AbstractAppender.parseInt(options[1], 100));
      }
  
  
      private final List<PatternFormatter> formatters;
      private final int maxLength;
  
      /**
       * Construct the converter.
       *
       * @param formatters The PatternFormatters to generate the text to manipulate.
       * @param maxLength  The max. length of the resulting string. Ellipsis ("...") is appended on shorted string, if greater than 20.
       */
      private MaxLengthConverter(final List<PatternFormatter> formatters, final int maxLength) {
          super("MaxLength", "maxLength");
          this.maxLength = maxLength;
          this.formatters = formatters;
          LOGGER.trace("new MaxLengthConverter with {}", maxLength);
      }
  
  
      @Override
      public void format(final LogEvent event, final StringBuilder toAppendTo) {
          final int initialLength = toAppendTo.length();
          for (int i = 0; i < formatters.size(); i++) {
              final PatternFormatter formatter = formatters.get(i);
              formatter.format(event, toAppendTo);
              if (toAppendTo.length() > initialLength + maxLength) {        // stop early
                  break;
              }
          }
          if (toAppendTo.length() > initialLength + maxLength) {
              toAppendTo.setLength(initialLength + maxLength);
              if (maxLength > 20) {        // only append ellipses if length is not very short
                 toAppendTo.append("...");
             }
         }
     }
 }