/*
    * Copyright 2012 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:
    *
    *   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.jboss.netty.channel.socket.nio;
  
  import org.jboss.netty.channel.socket.Worker;
  import org.jboss.netty.logging.InternalLogger;
  import org.jboss.netty.logging.InternalLoggerFactory;
  import org.jboss.netty.util.ExternalResourceReleasable;
  import org.jboss.netty.util.internal.ExecutorUtil;
  
  import java.util.concurrent.Executor;
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.atomic.AtomicBoolean;
  import java.util.concurrent.atomic.AtomicInteger;
  
  /**
   * Abstract base class for {@link WorkerPool} implementations that create the {@link Worker}'s
   * up-front and return them in a "fair" fashion when calling {@link #nextWorker()}
   */
  public abstract class AbstractNioWorkerPool<E extends AbstractNioWorker>
          implements WorkerPool<E>, ExternalResourceReleasable {
  
      /**
       * The worker pool raises an exception unless all worker threads start and run within this timeout (in seconds.)
       */
      private static final int INITIALIZATION_TIMEOUT = 10;
  
      private static final InternalLogger logger = InternalLoggerFactory.getInstance(AbstractNioWorkerPool.class);
  
      private final AbstractNioWorker[] workers;
      private final AtomicInteger workerIndex = new AtomicInteger();
      private final Executor workerExecutor;
      private final AtomicBoolean initialized = new AtomicBoolean(false);
  
      /**
       * Create a new instance
       *
       * @param workerExecutor the {@link Executor} to use for the {@link Worker}'s
       * @param workerCount the count of {@link Worker}'s to create
       */
      AbstractNioWorkerPool(Executor workerExecutor, int workerCount) {
          this(workerExecutor, workerCount, true);
      }
  
      AbstractNioWorkerPool(Executor workerExecutor, int workerCount, boolean autoInit) {
          if (workerExecutor == null) {
              throw new NullPointerException("workerExecutor");
          }
          if (workerCount <= 0) {
              throw new IllegalArgumentException(
                      "workerCount (" + workerCount + ") " + "must be a positive integer.");
          }
          workers = new AbstractNioWorker[workerCount];
          this.workerExecutor = workerExecutor;
          if (autoInit) {
              init();
          }
      }
  
      protected void init() {
          if (!initialized.compareAndSet(false, true)) {
              throw new IllegalStateException("initialized already");
          }
  
          for (int i = 0; i < workers.length; i++) {
              workers[i] = newWorker(workerExecutor);
          }
  
          waitForWorkerThreads();
      }
  
      private void waitForWorkerThreads() {
          long deadline = System.nanoTime() + TimeUnit.SECONDS.toNanos(INITIALIZATION_TIMEOUT);
          boolean warn = false;
          for (AbstractNioSelector worker: workers) {
              long waitTime = deadline - System.nanoTime();
              try {
                  if (waitTime <= 0) {
                      if (worker.thread == null) {
                          warn = true;
                          break;
                      }
                  } else if (!worker.startupLatch.await(waitTime, TimeUnit.NANOSECONDS)) {
                      warn = true;
                      break;
                 }
             } catch (InterruptedException ignore) {
                 // Stop waiting for the worker threads and let someone else take care of the interruption.
                 Thread.currentThread().interrupt();
                 break;
             }
         }
 
         if (warn) {
             logger.warn(
                     "Failed to get all worker threads ready within " + INITIALIZATION_TIMEOUT + " second(s). " +
                     "Make sure to specify the executor which has more threads than the requested workerCount. " +
                     "If unsure, use Executors.newCachedThreadPool().");
         }
     }
 
     /**
      * Create a new {@link Worker} which uses the given {@link Executor} to service IO.
      *
      * @param executor the {@link Executor} to use
      * @return worker the new {@link Worker}
      */
     protected abstract E newWorker(Executor executor);
 
     @SuppressWarnings("unchecked")
     public E nextWorker() {
         return (E) workers[Math.abs(workerIndex.getAndIncrement() % workers.length)];
     }
 
     public void rebuildSelectors() {
         for (AbstractNioWorker worker: workers) {
             worker.rebuildSelector();
         }
     }
 
     public void releaseExternalResources() {
         shutdown();
         ExecutorUtil.shutdownNow(workerExecutor);
     }
 
     public void shutdown() {
         for (AbstractNioWorker worker: workers) {
             worker.shutdown();
         }
     }
 
 }