content: /*
   * Copyright 1999-2022 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.common.ability.discover;
  
  import com.alibaba.nacos.common.ability.AbstractAbilityControlManager;
  import com.alibaba.nacos.common.spi.NacosServiceLoader;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.util.Collection;
  import java.util.Comparator;
  import java.util.List;
  import java.util.stream.Collectors;
  
  /**
   * This class is used to discover {@link AbstractAbilityControlManager} implements. All the ability operation will be
   * finish in this singleton.
   *
   * @author Daydreamer
   * @date 2022/7/14 19:58
   **/
  public class NacosAbilityManagerHolder {
      
      /**
       * . private constructor
       */
      private NacosAbilityManagerHolder() {
      }
      
      private static final Logger LOGGER = LoggerFactory.getLogger(NacosAbilityManagerHolder.class);
      
      /**
       * . singleton
       */
      private static AbstractAbilityControlManager abstractAbilityControlManager;
      
      /**
       * . get nacos ability control manager
       *
       * @return BaseAbilityControlManager
       */
      public static synchronized AbstractAbilityControlManager getInstance() {
          if (null == abstractAbilityControlManager) {
              initAbilityControlManager();
          }
          return abstractAbilityControlManager;
      }
      
      /**
       * . Return the target type of ability manager
       *
       * @param clazz clazz
       * @param <T>   target type
       * @return AbilityControlManager
       */
      public static <T extends AbstractAbilityControlManager> T getInstance(Class<T> clazz) {
          return clazz.cast(abstractAbilityControlManager);
      }
      
      private static void initAbilityControlManager() {
          // spi discover implement
          Collection<AbstractAbilityControlManager> load = null;
          load = NacosServiceLoader.load(AbstractAbilityControlManager.class);
          // the priority of the server is higher
          List<AbstractAbilityControlManager> collect = load.stream()
                  .sorted(Comparator.comparingInt(AbstractAbilityControlManager::getPriority))
                  .collect(Collectors.toList());
          // get the highest priority one
          if (load.size() > 0) {
              abstractAbilityControlManager = collect.get(collect.size() - 1);
              LOGGER.info("[AbilityControlManager] Successfully initialize AbilityControlManager");
          }
      }
  }
  