content: /*
   * Copyright 2022 The FeatHub Authors
   *
   * 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
   *
   *     https://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.feathub.flink.connectors.prometheus;
  
  import io.prometheus.client.CollectorRegistry;
  import io.prometheus.client.Gauge;
  import io.prometheus.client.SimpleCollector;
  
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  
  /**
   * The base class for MetricUpdater that update the metric with a list.
   *
   * @param <ELEMENT_T> The element type in the list.
   */
  public abstract class AbstractListMetricUpdater<ELEMENT_T>
          implements MetricUpdater<List<ELEMENT_T>> {
  
      protected final SimpleCollector<Gauge.Child> collector;
  
      public AbstractListMetricUpdater(
              String name, List<Map<String, String>> labelLists, CollectorRegistry registry) {
          verifyLabelLists(labelLists);
  
          collector =
                  Gauge.build()
                          .name(name)
                          .help(name)
                          .labelNames(labelLists.get(0).keySet().toArray(new String[0]))
                          .register(registry);
      }
  
      private void verifyLabelLists(List<Map<String, String>> labelLists) {
          if (labelLists.isEmpty()) {
              throw new RuntimeException("List metric must has at least one list of labels.");
          }
  
          if (labelLists.get(0).isEmpty()) {
              throw new RuntimeException("List metric must has at least one label.");
          }
  
          final Set<String> keySet = labelLists.get(0).keySet();
          for (Map<String, String> labels : labelLists) {
              if (!keySet.equals(labels.keySet())) {
                  throw new RuntimeException("All labels list must have the same set of label keys.");
              }
          }
      }
  }
  