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.metrics;
  
  import java.util.function.Function;
  
  import accord.local.durability.DurabilityService;
  import accord.topology.TopologyManager;
  import com.codahale.metrics.Gauge;
  import org.apache.cassandra.service.accord.AccordService;
  import org.apache.cassandra.service.accord.IAccordService;
  
  public class AccordMetricUtils
  {
      static <T> Gauge<T> fromAccordService(Function<IAccordService, T> ifSetup, T ifNotSetup)
      {
          return fromAccordService(ifSetup, Function.identity(), ifNotSetup);
      }
  
      static Gauge<Long> fromTopologyManager(Function<TopologyManager, Long> ifSetup)
      {
          return fromAccordService(service -> service.node().topology(), ifSetup, 0L);
      }
  
      static Gauge<Long> fromDurabilityService(Function<DurabilityService, Long> ifSetup)
      {
          return fromAccordService(service -> service.node().durability(), ifSetup, 0L);
      }
  
      static <I, T> Gauge<T> fromAccordService(Function<IAccordService, I> initialStep, Function<I, T> finalStep, T ifNotSetup)
      {
          if (AccordService.isSetup())
          {
              IAccordService service = AccordService.instance();
              if (!service.isEnabled())
                  return () -> ifNotSetup;
              I intermediate = initialStep.apply(service);
              return () -> finalStep.apply(intermediate);
          }
          return () -> {
              IAccordService service = AccordService.instance();
              if (!service.isEnabled())
                  return ifNotSetup;
              return finalStep.apply(initialStep.apply(service));
          };
      }
  }
  