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.util.Queue;
  import java.util.concurrent.ConcurrentLinkedQueue;
  import java.util.function.Consumer;
  import java.util.function.Predicate;
  
  import org.apache.cassandra.simulator.systems.InterceptingAwaitable.InterceptingSignal;
  import org.apache.cassandra.utils.concurrent.WaitQueue;
  
  import static org.apache.cassandra.simulator.systems.InterceptorOfGlobalMethods.Global.ifIntercepted;
  
  @PerClassLoader
  class InterceptingWaitQueue extends WaitQueue.Standard implements WaitQueue
  {
      final Queue<InterceptingSignal<?>> interceptible = new ConcurrentLinkedQueue<>();
  
      public InterceptingWaitQueue()
      {
      }
  
      public Signal register()
      {
          if (ifIntercepted() == null)
              return super.register();
  
          InterceptingSignal<?> signal = new InterceptingSignal<>();
          interceptible.add(signal);
          return signal;
      }
  
      public <V> Signal register(V value, Consumer<V> consumer)
      {
          if (ifIntercepted() == null)
              return super.register(value, consumer);
  
          InterceptingSignal<V> signal = new InterceptingSignal<>(value, consumer);
          interceptible.add(signal);
          return signal;
      }
  
      public boolean signal()
      {
          // directly signal the actual underlying queue if no intercepted waiters are present
          return consumeUntil(InterceptingSignal::doSignal) || super.signal();
      }
  
      public void signalAll()
      {
          consumeUntil(s -> {
              s.signal();
              return false;
          });
          super.signalAll();
      }
  
      public boolean hasWaiters()
      {
          if (super.hasWaiters())
              return true;
          if (interceptible.isEmpty())
              return false;
  
          return !interceptible.stream().allMatch(Signal::isSet);
      }
  
      private boolean consumeUntil(Predicate<InterceptingSignal<?>> consumeUntil)
      {
          InterceptingSignal<?> signal;
          while (null != (signal = interceptible.poll()))
          {
              if (consumeUntil.test(signal))
                  return true;
          }
          return false;
      }
  
      public int getWaiting()
      {
          return super.getWaiting() + (int)interceptible.stream().filter(s -> !s.isSignalled).count();
      }
  }
  