content: /*
   *  Copyright 1999-2021 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.naming.selector;
  
  import com.alibaba.nacos.api.cmdb.pojo.Entity;
  import com.alibaba.nacos.api.exception.NacosException;
  import com.alibaba.nacos.api.naming.pojo.Instance;
  import com.alibaba.nacos.api.selector.AbstractCmdbSelector;
  import com.alibaba.nacos.api.selector.context.CmdbContext;
  import com.alibaba.nacos.common.utils.CollectionUtils;
  import com.alibaba.nacos.common.utils.StringUtils;
  import com.alibaba.nacos.naming.selector.interpreter.ExpressionInterpreter;
  
  import java.util.Collections;
  import java.util.List;
  import java.util.Map;
  import java.util.Objects;
  import java.util.Optional;
  import java.util.Set;
  import java.util.stream.Collectors;
  
  /**
   * The {@link LabelSelector} will return the instances labels in {@link #labels} and providers' label value is same with consumer.
   * If none matched, then will return all providers instead of.
   *
   * @author chenglu
   * @date 2021-07-16 16:26
   */
  public class LabelSelector<T extends Instance> extends AbstractCmdbSelector<T> {
      
      private static final String TYPE = "label";
      
      /**
       * {@link Entity} labels key.
       */
      private Set<String> labels;
      
      public Set<String> getLabels() {
          return labels;
      }
      
      public void setLabels(Set<String> labels) {
          this.labels = labels;
      }
      
      @Override
      protected List<T> doSelect(CmdbContext<T> context) {
          if (CollectionUtils.isEmpty(labels)) {
              return context.getProviders()
                      .stream()
                      .map(CmdbContext.CmdbInstance::getInstance)
                      .collect(Collectors.toList());
          }
          CmdbContext.CmdbInstance<T> consumer = context.getConsumer();
          Map<String, String> consumerLabels = Optional.ofNullable(consumer.getEntity())
                  .map(Entity::getLabels)
                  .orElse(Collections.emptyMap());
          
          // filter the instance if consumer and providers' label values equals.
          List<T> result = context.getProviders()
                  .stream()
                  .filter(ci -> {
                      Entity providerEntity = ci.getEntity();
                      if (Objects.isNull(providerEntity)) {
                          return false;
                      }
                      Map<String, String> providerLabels = Optional.ofNullable(ci.getEntity().getLabels())
                              .orElse(Collections.emptyMap());
                      return labels.stream()
                              .allMatch(label -> {
                                  String consumerLabelValue = consumerLabels.get(label);
                                  if (StringUtils.isBlank(consumerLabelValue)) {
                                      return false;
                                  }
                                  return Objects.equals(consumerLabelValue, providerLabels.get(label));
                              });
                  })
                  .map(CmdbContext.CmdbInstance::getInstance)
                  .collect(Collectors.toList());
          
          // if none match, then return all providers.
          if (CollectionUtils.isEmpty(result)) {
              return context.getProviders()
                      .stream()
                      .map(CmdbContext.CmdbInstance::getInstance)
                      .collect(Collectors.toList());
          }
          return result;
      }
      
      @Override
      protected void doParse(String expression) throws NacosException {
          this.labels = ExpressionInterpreter.parseExpression(expression);
      }
      
      @Override
      public String getType() {
          return TYPE;
      }
  }
  