content: /*
   * Copyright 1999-2020 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.core.remote.grpc.negotiator;
  
  import com.alibaba.nacos.common.spi.NacosServiceLoader;
  import com.alibaba.nacos.common.utils.Pair;
  import com.alibaba.nacos.core.utils.Loggers;
  import com.alibaba.nacos.sys.env.EnvUtil;
  
  import java.util.Map;
  import java.util.concurrent.ConcurrentHashMap;
  
  /**
   * Abstract base class for ProtocolNegotiatorBuilder singletons. This class provides a common implementation for
   * building ProtocolNegotiator instances based on a given type. Subclasses should provide implementations for loading
   * ProtocolNegotiatorBuilder instances via SPI and defining default builders.
   *
   * @author stone-98
   * @date 2024/2/21
   */
  public abstract class AbstractProtocolNegotiatorBuilderSingleton implements ProtocolNegotiatorBuilder {
      
      /**
       * Map to store ProtocolNegotiatorBuilders based on their types.
       */
      protected static final Map<String, ProtocolNegotiatorBuilder> BUILDER_MAP = new ConcurrentHashMap<>();
      
      static {
          try {
              for (ProtocolNegotiatorBuilder each : NacosServiceLoader.load(ProtocolNegotiatorBuilder.class)) {
                  BUILDER_MAP.put(each.type(), each);
                  Loggers.REMOTE.info("Load ProtocolNegotiatorBuilder {} for type {}", each.getClass().getCanonicalName(),
                          each.type());
              }
          } catch (Exception e) {
              Loggers.REMOTE.warn("Load ProtocolNegotiatorBuilder failed.", e);
          }
      }
      
      /**
       * The property key to retrieve the actual type of ProtocolNegotiatorBuilder.
       */
      protected final String typePropertyKey;
      
      /**
       * The actual type of ProtocolNegotiatorBuilder, retrieved from system properties.
       */
      protected String actualType;
      
      /**
       * Constructs an instance of AbstractProtocolNegotiatorBuilderSingleton with the specified type property key.
       *
       * @param typePropertyKey the property key to retrieve the actual type
       */
      public AbstractProtocolNegotiatorBuilderSingleton(String typePropertyKey) {
          this.typePropertyKey = typePropertyKey;
          this.actualType = EnvUtil.getProperty(typePropertyKey, defaultBuilderPair().getFirst());
      }
      
      /**
       * Builds a ProtocolNegotiator instance based on the actual type.
       *
       * @return a ProtocolNegotiator instance
       */
      @Override
      public NacosGrpcProtocolNegotiator build() {
          ProtocolNegotiatorBuilder actualBuilder = BUILDER_MAP.get(actualType);
          if (null == actualBuilder) {
              Loggers.REMOTE.warn("Not found ProtocolNegotiatorBuilder for type {}, will use default type {}", actualType,
                      defaultBuilderPair().getFirst());
              return defaultBuilderPair().getSecond().build();
          }
          return actualBuilder.build();
      }
      
      /**
       * Declare default ProtocolNegotiatorBuilders in case loading from SPI fails.
       *
       * @return a Pair of String and ProtocolNegotiatorBuilder representing the default builder
       */
      protected abstract Pair<String, ProtocolNegotiatorBuilder> defaultBuilderPair();
  }
  