/*
    * 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 java.util.concurrent.Executor;
  import java.util.concurrent.atomic.AtomicInteger;
  
  import org.jboss.netty.channel.socket.Worker;
  import org.jboss.netty.util.ExternalResourceReleasable;
  import org.jboss.netty.util.internal.ExecutorUtil;
  
  /**
   * 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 {
  
      private final AbstractNioWorker[] workers;
      private final AtomicInteger workerIndex = new AtomicInteger();
      private final Executor workerExecutor;
  
  
      /**
       * 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) {
          if (workerExecutor == null) {
              throw new NullPointerException("workerExecutor");
          }
          if (workerCount <= 0) {
              throw new IllegalArgumentException(
                      "workerCount (" + workerCount + ") " +
                      "must be a positive integer.");
          }
          workers = new AbstractNioWorker[workerCount];
  
          for (int i = 0; i < workers.length; i++) {
              workers[i] = createWorker(workerExecutor);
          }
          this.workerExecutor = workerExecutor;
      }
  
      /**
       * 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 createWorker(Executor executor);
  
      @SuppressWarnings("unchecked")
      public E nextWorker() {
          return (E) workers[Math.abs(workerIndex.getAndIncrement() % workers.length)];
      }
  
  
      public void releaseExternalResources() {
          ExecutorUtil.terminate(workerExecutor);
          for (AbstractNioWorker worker: workers) {
              worker.releaseExternalResources();
          }
      }
  
  }