/*

 * Copyright (c) 2008, 2012, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package sun.nio.ch;

import java.util.concurrent.*;

import java.security.AccessController;

import java.security.PrivilegedAction;

import sun.security.action.GetPropertyAction;

import sun.security.action.GetIntegerAction;

import jdk.internal.misc.InnocuousThread;

/**

 * Encapsulates a thread pool associated with a channel group.

 */

public class ThreadPool {

    private static final String DEFAULT_THREAD_POOL_THREAD_FACTORY =

        "java.nio.channels.DefaultThreadPool.threadFactory";

    private static final String DEFAULT_THREAD_POOL_INITIAL_SIZE =

        "java.nio.channels.DefaultThreadPool.initialSize";

    private final ExecutorService executor;

    // indicates if thread pool is fixed size

    private final boolean isFixed;

    // indicates the pool size (for a fixed thread pool configuratin this is

    // the maximum pool size; for other thread pools it is the initial size)

    private final int poolSize;

    private ThreadPool(ExecutorService executor,

                       boolean isFixed,

                       int poolSize)

    {

        this.executor = executor;

        this.isFixed = isFixed;

        this.poolSize = poolSize;

    }

    ExecutorService executor() {

        return executor;

    }

    boolean isFixedThreadPool() {

        return isFixed;

    }

    int poolSize() {

        return poolSize;

    }

    static ThreadFactory defaultThreadFactory() {

        if (System.getSecurityManager() == null) {

            return (Runnable r) -> {

                Thread t = new Thread(r);

                t.setDaemon(true);

                return t;

            };

        } else {

            return (Runnable r) -> {

                PrivilegedAction<Thread> action = () -> {

                    Thread t = InnocuousThread.newThread(r);

                    t.setDaemon(true);

                    return t;

               };

               return AccessController.doPrivileged(action);

           };

        }

    }

    private static class DefaultThreadPoolHolder {

        static final ThreadPool defaultThreadPool = createDefault();

    }

    // return the default (system-wide) thread pool

    static ThreadPool getDefault() {

        return DefaultThreadPoolHolder.defaultThreadPool;

    }

    // create thread using default settings (configured by system properties)

    static ThreadPool createDefault() {

        // default the number of fixed threads to the hardware core count

        int initialSize = getDefaultThreadPoolInitialSize();

        if (initialSize < 0)

            initialSize = Runtime.getRuntime().availableProcessors();

        // default to thread factory that creates daemon threads

        ThreadFactory threadFactory = getDefaultThreadPoolThreadFactory();

        if (threadFactory == null)

            threadFactory = defaultThreadFactory();

        // create thread pool

        ExecutorService executor = Executors.newCachedThreadPool(threadFactory);

        return new ThreadPool(executor, false, initialSize);

    }

    // create using given parameters

    static ThreadPool create(int nThreads, ThreadFactory factory) {

        if (nThreads <= 0)

            throw new IllegalArgumentException("'nThreads' must be > 0");

        ExecutorService executor = Executors.newFixedThreadPool(nThreads, factory);

        return new ThreadPool(executor, true, nThreads);

    }

    // wrap a user-supplied executor

    public static ThreadPool wrap(ExecutorService executor, int initialSize) {

        if (executor == null)

            throw new NullPointerException("'executor' is null");

        // attempt to check if cached thread pool

        if (executor instanceof ThreadPoolExecutor) {

            int max = ((ThreadPoolExecutor)executor).getMaximumPoolSize();

            if (max == Integer.MAX_VALUE) {

                if (initialSize < 0) {

                    initialSize = Runtime.getRuntime().availableProcessors();

                } else {

                   // not a cached thread pool so ignore initial size

                    initialSize = 0;

                }

            }

        } else {

            // some other type of thread pool

            if (initialSize < 0)

                initialSize = 0;

        }

        return new ThreadPool(executor, false, initialSize);

    }

    private static int getDefaultThreadPoolInitialSize() {

        String propValue = AccessController.doPrivileged(new

            GetPropertyAction(DEFAULT_THREAD_POOL_INITIAL_SIZE));

        if (propValue != null) {

            try {

                return Integer.parseInt(propValue);

            } catch (NumberFormatException x) {

                throw new Error("Value of property '" + DEFAULT_THREAD_POOL_INITIAL_SIZE +

                    "' is invalid: " + x);

            }

        }

        return -1;

    }

    private static ThreadFactory getDefaultThreadPoolThreadFactory() {

        String propValue = AccessController.doPrivileged(new

            GetPropertyAction(DEFAULT_THREAD_POOL_THREAD_FACTORY));

        if (propValue != null) {

            try {

                @SuppressWarnings("deprecation")

                Object tmp = Class

                    .forName(propValue, true, ClassLoader.getSystemClassLoader()).newInstance();

                return (ThreadFactory)tmp;

            } catch (ClassNotFoundException | InstantiationException | IllegalAccessException x) {

                throw new Error(x);

            }

        }

        return null;

    }

}