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.bifromq.basescheduler;
  
  import org.apache.bifromq.basehookloader.BaseHookLoader;
  import org.apache.bifromq.basescheduler.spi.ICallScheduler;
  import org.apache.bifromq.basescheduler.spi.ICallSchedulerFactory;
  import java.util.Map;
  import lombok.extern.slf4j.Slf4j;
  
  @Slf4j
  class CallSchedulerFactory implements ICallSchedulerFactory {
      public static final ICallSchedulerFactory INSTANCE = new CallSchedulerFactory();
  
      private final ICallSchedulerFactory delegate;
  
      private CallSchedulerFactory() {
          Map<String, ICallSchedulerFactory> factoryMap = BaseHookLoader.load(ICallSchedulerFactory.class);
          if (factoryMap.isEmpty()) {
              delegate = FallbackCallSchedulerFactory.INSTANCE;
          } else {
              delegate = factoryMap.values().iterator().next();
          }
      }
  
      @Override
      public <ReqT> ICallScheduler<ReqT> create(String name) {
          try {
              ICallScheduler<ReqT> scheduler = delegate.create(name);
              if (scheduler == null) {
                  return FallbackCallSchedulerFactory.INSTANCE.create(name);
              }
              return scheduler;
          } catch (Throwable e) {
              log.error("Failed to create pipelineDepthEstimator: scheduler={}", name, e);
              return FallbackCallSchedulerFactory.INSTANCE.create(name);
          }
      }
  
      private static class FallbackCallSchedulerFactory implements ICallSchedulerFactory {
          private static final ICallSchedulerFactory INSTANCE = new FallbackCallSchedulerFactory();
  
          @Override
          public <ReqT> ICallScheduler<ReqT> create(String name) {
              return new ICallScheduler<>() {
              };
          }
      }
  }
  