content: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you 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 org.apache.cassandra.io.sstable;
  
  import java.util.function.BiFunction;
  import java.util.function.Function;
  
  import org.apache.cassandra.io.sstable.format.SSTableReader;
  
  public abstract class AbstractMetricsProviders<R extends SSTableReader> implements MetricsProviders
  {
      protected final <T extends Number> GaugeProvider<T> newGaugeProvider(String name, Function<Iterable<R>, T> combiner)
      {
          return new SimpleGaugeProvider<>(this::map, name, combiner);
      }
  
      protected final <T extends Number> GaugeProvider<T> newGaugeProvider(String name, T neutralValue, Function<R, T> extractor, BiFunction<T, T, T> combiner)
      {
          return new SimpleGaugeProvider<>(this::map, name, readers -> {
              T total = neutralValue;
              for (R reader : readers)
                  total = combiner.apply(total, extractor.apply(reader));
              return total;
          });
      }
  
      protected abstract R map(SSTableReader r);
  }
  