/*
 * Copyright 2011 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.Channel;
import org.jboss.netty.channel.socket.Worker;
import org.jboss.netty.util.ExternalResourceReleasable;
import org.jboss.netty.util.internal.ExecutorUtil;

import java.util.concurrent.Executor;
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 {

    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 allowShutdownOnIdle allow the {@link Worker}'s to shutdown when there is not {@link Channel} is registered with it
     * @param workerCount the count of {@link Worker}'s to create
     */
    AbstractNioWorkerPool(Executor workerExecutor, int workerCount, boolean allowShutDownOnIdle) {
        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, allowShutDownOnIdle);
        }
        this.workerExecutor = workerExecutor;

    }

    /**
     * Create a new {@link Worker} which uses the given {@link Executor} to service IO
     * 
     * 
     * @param executor the {@link Executor} to use
     * @param allowShutdownOnIdle allow the {@link Worker} to shutdown when there is not {@link Channel} is registered with it
     * @return worker the new {@link Worker} 
     */
    protected abstract E createWorker(Executor executor, boolean allowShutdownOnIdle);

    @SuppressWarnings("unchecked")
    public E nextWorker() {
        return (E) workers[Math.abs(workerIndex.getAndIncrement() % workers.length)];
    }


    public void releaseExternalResources() {
        ExecutorUtil.terminate(workerExecutor);
    }

}