/*
    * Copyright 2016 The Netty Project
    *
    * The Netty Project 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:
    *
    *   https://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 io.netty.util.concurrent;
  
  import io.netty.util.internal.logging.InternalLogger;
  import io.netty.util.internal.logging.InternalLoggerFactory;
  
  import java.util.Collections;
  import java.util.Iterator;
  import java.util.List;
  import java.util.Set;
  import java.util.concurrent.Callable;
  import java.util.concurrent.Delayed;
  import java.util.concurrent.ExecutionException;
  import java.util.concurrent.RejectedExecutionHandler;
  import java.util.concurrent.RunnableScheduledFuture;
  import java.util.concurrent.ScheduledThreadPoolExecutor;
  import java.util.concurrent.ThreadFactory;
  import java.util.concurrent.TimeUnit;
  
  import static java.util.concurrent.TimeUnit.NANOSECONDS;
  
  /**
   * {@link EventExecutor} implementation which makes no guarantees about the ordering of task execution that
   * are submitted because there may be multiple threads executing these tasks.
   * This implementation is most useful for protocols that do not need strict ordering.
   *
   * <strong>Because it provides no ordering care should be taken when using it!</strong>
   */
  public final class UnorderedThreadPoolEventExecutor extends ScheduledThreadPoolExecutor implements EventExecutor {
      private static final InternalLogger logger = InternalLoggerFactory.getInstance(
              UnorderedThreadPoolEventExecutor.class);
  
      private final Promise<?> terminationFuture = GlobalEventExecutor.INSTANCE.newPromise();
      private final Set<EventExecutor> executorSet = Collections.singleton((EventExecutor) this);
  
      /**
       * Calls {@link UnorderedThreadPoolEventExecutor#UnorderedThreadPoolEventExecutor(int, ThreadFactory)}
       * using {@link DefaultThreadFactory}.
       */
      public UnorderedThreadPoolEventExecutor(int corePoolSize) {
          this(corePoolSize, new DefaultThreadFactory(UnorderedThreadPoolEventExecutor.class));
      }
  
      /**
       * See {@link ScheduledThreadPoolExecutor#ScheduledThreadPoolExecutor(int, ThreadFactory)}
       */
      public UnorderedThreadPoolEventExecutor(int corePoolSize, ThreadFactory threadFactory) {
          super(corePoolSize, threadFactory);
      }
  
      /**
       * Calls {@link UnorderedThreadPoolEventExecutor#UnorderedThreadPoolEventExecutor(int,
       * ThreadFactory, java.util.concurrent.RejectedExecutionHandler)} using {@link DefaultThreadFactory}.
       */
      public UnorderedThreadPoolEventExecutor(int corePoolSize, RejectedExecutionHandler handler) {
          this(corePoolSize, new DefaultThreadFactory(UnorderedThreadPoolEventExecutor.class), handler);
      }
  
      /**
       * See {@link ScheduledThreadPoolExecutor#ScheduledThreadPoolExecutor(int, ThreadFactory, RejectedExecutionHandler)}
       */
      public UnorderedThreadPoolEventExecutor(int corePoolSize, ThreadFactory threadFactory,
                                              RejectedExecutionHandler handler) {
          super(corePoolSize, threadFactory, handler);
      }
  
      @Override
      public EventExecutor next() {
          return this;
      }
  
      @Override
      public EventExecutorGroup parent() {
          return this;
      }
  
      @Override
      public boolean inEventLoop() {
          return false;
      }
  
      @Override
      public boolean inEventLoop(Thread thread) {
          return false;
      }
 
     @Override
     public <V> Promise<V> newPromise() {
         return new DefaultPromise<V>(this);
     }
 
     @Override
     public <V> ProgressivePromise<V> newProgressivePromise() {
         return new DefaultProgressivePromise<V>(this);
     }
 
     @Override
     public <V> Future<V> newSucceededFuture(V result) {
         return new SucceededFuture<V>(this, result);
     }
 
     @Override
     public <V> Future<V> newFailedFuture(Throwable cause) {
         return new FailedFuture<V>(this, cause);
     }
 
     @Override
     public boolean isShuttingDown() {
         return isShutdown();
     }
 
     @Override
     public List<Runnable> shutdownNow() {
         List<Runnable> tasks = super.shutdownNow();
         terminationFuture.trySuccess(null);
         return tasks;
     }
 
     @Override
     public void shutdown() {
         super.shutdown();
         terminationFuture.trySuccess(null);
     }
 
     @Override
     public Future<?> shutdownGracefully() {
         return shutdownGracefully(2, 15, TimeUnit.SECONDS);
     }
 
     @Override
     public Future<?> shutdownGracefully(long quietPeriod, long timeout, TimeUnit unit) {
         // TODO: At the moment this just calls shutdown but we may be able to do something more smart here which
         //       respects the quietPeriod and timeout.
         shutdown();
         return terminationFuture();
     }
 
     @Override
     public Future<?> terminationFuture() {
         return terminationFuture;
     }
 
     @Override
     public Iterator<EventExecutor> iterator() {
         return executorSet.iterator();
     }
 
     @Override
     protected <V> RunnableScheduledFuture<V> decorateTask(Runnable runnable, RunnableScheduledFuture<V> task) {
         return runnable instanceof NonNotifyRunnable ?
                 task : new RunnableScheduledFutureTask<V>(this, task, false);
     }
 
     @Override
     protected <V> RunnableScheduledFuture<V> decorateTask(Callable<V> callable, RunnableScheduledFuture<V> task) {
         return new RunnableScheduledFutureTask<V>(this, task, true);
     }
 
     @Override
     public ScheduledFuture<?> schedule(Runnable command, long delay, TimeUnit unit) {
         return (ScheduledFuture<?>) super.schedule(command, delay, unit);
     }
 
     @Override
     public <V> ScheduledFuture<V> schedule(Callable<V> callable, long delay, TimeUnit unit) {
         return (ScheduledFuture<V>) super.schedule(callable, delay, unit);
     }
 
     @Override
     public ScheduledFuture<?> scheduleAtFixedRate(Runnable command, long initialDelay, long period, TimeUnit unit) {
         return (ScheduledFuture<?>) super.scheduleAtFixedRate(command, initialDelay, period, unit);
     }
 
     @Override
     public ScheduledFuture<?> scheduleWithFixedDelay(Runnable command, long initialDelay, long delay, TimeUnit unit) {
         return (ScheduledFuture<?>) super.scheduleWithFixedDelay(command, initialDelay, delay, unit);
     }
 
     @Override
     public Future<?> submit(Runnable task) {
         return (Future<?>) super.submit(task);
     }
 
     @Override
     public <T> Future<T> submit(Runnable task, T result) {
         return (Future<T>) super.submit(task, result);
     }
 
     @Override
     public <T> Future<T> submit(Callable<T> task) {
         return (Future<T>) super.submit(task);
     }
 
     @Override
     public void execute(Runnable command) {
         super.schedule(new NonNotifyRunnable(command), 0, NANOSECONDS);
     }
 
     private static final class RunnableScheduledFutureTask<V> extends PromiseTask<V>
             implements RunnableScheduledFuture<V>, ScheduledFuture<V> {
         private final RunnableScheduledFuture<V> future;
         private final boolean wasCallable;
 
         RunnableScheduledFutureTask(EventExecutor executor, RunnableScheduledFuture<V> future, boolean wasCallable) {
             super(executor, future);
             this.future = future;
             this.wasCallable = wasCallable;
         }
 
         @Override
         V runTask() throws Throwable {
             V result =  super.runTask();
             if (result == null && wasCallable) {
                 // If this RunnableScheduledFutureTask wraps a RunnableScheduledFuture that wraps a Callable we need
                 // to ensure that we return the correct result by calling future.get().
                 //
                 // See https://github.com/netty/netty/issues/11072
                 assert future.isDone();
                 try {
                     return future.get();
                 } catch (ExecutionException e) {
                     // unwrap exception.
                     throw e.getCause();
                 }
             }
             return result;
         }
 
         @Override
         public void run() {
             if (!isPeriodic()) {
                 super.run();
             } else if (!isDone()) {
                 try {
                     // Its a periodic task so we need to ignore the return value
                     runTask();
                 } catch (Throwable cause) {
                     if (!tryFailureInternal(cause)) {
                         logger.warn("Failure during execution of task", cause);
                     }
                 }
             }
         }
 
         @Override
         public boolean isPeriodic() {
             return future.isPeriodic();
         }
 
         @Override
         public long getDelay(TimeUnit unit) {
             return future.getDelay(unit);
         }
 
         @Override
         public int compareTo(Delayed o) {
             return future.compareTo(o);
         }
     }
 
     // This is a special wrapper which we will be used in execute(...) to wrap the submitted Runnable. This is needed as
     // ScheduledThreadPoolExecutor.execute(...) will delegate to submit(...) which will then use decorateTask(...).
     // The problem with this is that decorateTask(...) needs to ensure we only do our own decoration if we not call
     // from execute(...) as otherwise we may end up creating an endless loop because DefaultPromise will call
     // EventExecutor.execute(...) when notify the listeners of the promise.
     //
     // See https://github.com/netty/netty/issues/6507
     private static final class NonNotifyRunnable implements Runnable {
 
         private final Runnable task;
 
         NonNotifyRunnable(Runnable task) {
             this.task = task;
         }
 
         @Override
         public void run() {
             task.run();
         }
     }
 }