content: /*
   * Copyright 1999-2018 Alibaba Group Holding Ltd.
   *
   * Licensed 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 com.alibaba.nacos.client.config.impl;
  
  import com.alibaba.nacos.api.config.ConfigChangeItem;
  import com.alibaba.nacos.api.config.listener.ConfigChangeParser;
  import com.alibaba.nacos.common.spi.NacosServiceLoader;
  
  import java.io.IOException;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.LinkedList;
  import java.util.List;
  import java.util.Map;
  
  /**
   * ConfigChangeHandler.
   *
   * @author rushsky518
   */
  public class ConfigChangeHandler {
      
      private static class ConfigChangeHandlerHolder {
          
          private static final ConfigChangeHandler INSTANCE = new ConfigChangeHandler();
      }
      
      private ConfigChangeHandler() {
          this.parserList = new LinkedList<>();
          
          Collection<ConfigChangeParser> loader = NacosServiceLoader.load(ConfigChangeParser.class);
          this.parserList.addAll(loader);
  
          this.parserList.add(new PropertiesChangeParser());
          this.parserList.add(new YmlChangeParser());
      }
      
      public static ConfigChangeHandler getInstance() {
          return ConfigChangeHandlerHolder.INSTANCE;
      }
      
      /**
       * Parse changed data.
       *
       * @param oldContent old data
       * @param newContent new data
       * @param type       data type
       * @return change data map
       * @throws IOException io exception
       */
      public Map<String, ConfigChangeItem> parseChangeData(String oldContent, String newContent, String type) throws IOException {
          for (ConfigChangeParser changeParser : this.parserList) {
              if (changeParser.isResponsibleFor(type)) {
                  return changeParser.doParse(oldContent, newContent, type);
              }
          }
          
          return Collections.emptyMap();
      }
      
      private final List<ConfigChangeParser> parserList;
      
  }
  