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.simulator.systems;
  
  import java.net.InetSocketAddress;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.CopyOnWriteArrayList;
  import java.util.concurrent.CopyOnWriteArraySet;
  import java.util.function.Consumer;
  import java.util.function.Function;
  
  import org.apache.cassandra.distributed.Cluster;
  import org.apache.cassandra.gms.FailureDetector;
  import org.apache.cassandra.gms.IFailureDetectionEventListener;
  import org.apache.cassandra.gms.IFailureDetector;
  import org.apache.cassandra.locator.InetAddressAndPort;
  
  public class SimulatedFailureDetector
  {
      public static class Instance implements IFailureDetector
      {
          private static volatile FailureDetector wrapped;
  
          private static volatile Function<InetSocketAddress, Boolean> OVERRIDE;
          private static final Set<IFailureDetectionEventListener> LISTENERS = new CopyOnWriteArraySet<>();
  
          private static FailureDetector wrapped()
          {
              FailureDetector detector = wrapped;
              if (detector == null)
              {
                  synchronized (LISTENERS)
                  {
                      if (wrapped == null)
                          wrapped = new FailureDetector();
                  }
                  detector = wrapped;
              }
              return detector;
          }
  
          private Boolean override(InetAddressAndPort ep)
          {
              Function<InetSocketAddress, Boolean> overrideF = OVERRIDE;
              return overrideF == null ? null : overrideF.apply(new InetSocketAddress(ep.getAddress(), ep.getPort()));
          }
  
          public boolean isAlive(InetAddressAndPort ep)
          {
              Boolean override = override(ep);
              return override != null ? override : wrapped().isAlive(ep);
          }
  
          public void interpret(InetAddressAndPort ep)
          {
              wrapped().interpret(ep);
          }
  
          public void report(InetAddressAndPort ep)
          {
              wrapped().report(ep);
          }
  
          public void remove(InetAddressAndPort ep)
          {
              wrapped().remove(ep);
          }
  
          public void forceConviction(InetAddressAndPort ep)
          {
              wrapped().forceConviction(ep);
          }
  
          public void registerFailureDetectionEventListener(IFailureDetectionEventListener listener)
          {
              LISTENERS.add(listener);
          }
  
          public void unregisterFailureDetectionEventListener(IFailureDetectionEventListener listener)
          {
              LISTENERS.remove(listener);
          }
  
          synchronized static void setup(Function<InetSocketAddress, Boolean> override, Consumer<Consumer<InetSocketAddress>> register)
          {
              OVERRIDE = override;
              register.accept(ep -> LISTENERS.forEach(c -> c.convict(InetAddressAndPort.getByAddress(ep), Double.MAX_VALUE)));
          }
      }
  
      final List<Consumer<InetSocketAddress>> listeners = new CopyOnWriteArrayList<>();
      final Map<InetSocketAddress, Boolean> override = new ConcurrentHashMap<>();
  
      public SimulatedFailureDetector(Cluster cluster)
      {
          cluster.forEach(i -> i.unsafeAcceptOnThisThread(Instance::setup,
                  override::get,
                  consumer -> listeners.add(e -> i.unsafeAcceptOnThisThread(Consumer::accept, consumer, e)))
          );
      }
  
      public void markUp(InetSocketAddress address)
      {
          override.put(address, Boolean.TRUE);
          listeners.forEach(c -> c.accept(address));
      }
  
      public void markDown(InetSocketAddress address)
      {
          override.put(address, Boolean.FALSE);
          listeners.forEach(c -> c.accept(address));
      }
  }
  