content: /*
   * Copyright 1999-2023 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.naming.selector;
  
  import com.alibaba.nacos.api.naming.pojo.Instance;
  import com.alibaba.nacos.api.naming.selector.NamingContext;
  import com.alibaba.nacos.api.naming.selector.NamingResult;
  import com.alibaba.nacos.api.naming.selector.NamingSelector;
  
  import java.util.Collections;
  import java.util.List;
  import java.util.function.Predicate;
  import java.util.stream.Collectors;
  
  /**
   * Default naming selector.
   *
   * @author lideyou
   */
  public class DefaultNamingSelector implements NamingSelector {
      
      private final Predicate<Instance> filter;
      
      public DefaultNamingSelector(Predicate<Instance> filter) {
          this.filter = filter;
      }
      
      @Override
      public NamingResult select(NamingContext context) {
          List<Instance> instances = doFilter(context.getInstances());
          return () -> instances;
      }
      
      private List<Instance> doFilter(List<Instance> instances) {
          return instances == null ? Collections.emptyList()
                  : instances.stream().filter(filter).collect(Collectors.toList());
      }
  }
  