/*

 * 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.

 *

 * 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

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 */

/*

 * This file is available under and governed by the GNU General Public

 * License version 2 only, as published by the Free Software Foundation.

 * However, the following notice accompanied the original version of this

 * file:

 *

 * Written by Martin Buchholz with assistance from members of JCP

 * JSR-166 Expert Group and released to the public domain, as

 * explained at http://creativecommons.org/publicdomain/zero/1.0/

 */

/*

 * @test

 * @bug 8022642 8065320 8129861

 * @summary Ensure relative sanity when zero core threads

 * @library /lib/testlibrary/

 */

import static java.util.concurrent.TimeUnit.HOURS;

import static java.util.concurrent.TimeUnit.MILLISECONDS;

import java.lang.reflect.Field;

import java.util.concurrent.BlockingQueue;

import java.util.concurrent.ScheduledThreadPoolExecutor;

import java.util.concurrent.locks.Condition;

import java.util.concurrent.locks.ReentrantLock;

import java.util.function.BooleanSupplier;

import jdk.testlibrary.Utils;

public class ZeroCoreThreads {

    static final long LONG_DELAY_MS = Utils.adjustTimeout(10_000);

    static long millisElapsedSince(long startTime) {

        return (System.nanoTime() - startTime) / (1000L * 1000L);

    }

    static void spinWaitUntil(BooleanSupplier predicate, long timeoutMillis) {

        long startTime = -1L;

        while (!predicate.getAsBoolean()) {

            if (startTime == -1L)

                startTime = System.nanoTime();

            else if (millisElapsedSince(startTime) > timeoutMillis)

                throw new AssertionError(

                    String.format("timed out after %s ms", timeoutMillis));

            Thread.yield();

        }

    }

    static boolean hasWaiters(ReentrantLock lock, Condition condition) {

        lock.lock();

        try {

            return lock.hasWaiters(condition);

        } finally {

            lock.unlock();

        }

    }

    static void awaitHasWaiters(ReentrantLock lock, Condition condition,

                                long timeoutMillis) {

        spinWaitUntil(() -> hasWaiters(lock, condition), timeoutMillis);

    }

    static <T> T getField(Object x, String fieldName) {

        try {

            Field field = x.getClass().getDeclaredField(fieldName);

            field.setAccessible(true);

            return (T) field.get(x);

        } catch (ReflectiveOperationException ex) {

            throw new AssertionError(ex);

        }

    }

    void test(String[] args) throws Throwable {

        ScheduledThreadPoolExecutor p = new ScheduledThreadPoolExecutor(0);

        try {

            test(p);

        } finally {

            p.shutdownNow();

            check(p.awaitTermination(LONG_DELAY_MS, MILLISECONDS));

        }

    }

    void test(ScheduledThreadPoolExecutor p) throws Throwable {

        Runnable dummy = new Runnable() { public void run() {

            throw new AssertionError("shouldn't get here"); }};

        BlockingQueue q = p.getQueue();

        ReentrantLock lock = getField(q, "lock");

        Condition available = getField(q, "available");

        equal(0, p.getPoolSize());

        equal(0, p.getLargestPoolSize());

        equal(0L, p.getTaskCount());

        equal(0L, p.getCompletedTaskCount());

        p.schedule(dummy, 1L, HOURS);

        // Ensure one pool thread actually waits in timed queue poll

        awaitHasWaiters(lock, available, LONG_DELAY_MS);

        equal(1, p.getPoolSize());

        equal(1, p.getLargestPoolSize());

        equal(1L, p.getTaskCount());

        equal(0L, p.getCompletedTaskCount());

    }

    //--------------------- Infrastructure ---------------------------

    volatile int passed = 0, failed = 0;

    void pass() {passed++;}

    void fail() {failed++; Thread.dumpStack();}

    void fail(String msg) {System.err.println(msg); fail();}

    void unexpected(Throwable t) {failed++; t.printStackTrace();}

    void check(boolean cond) {if (cond) pass(); else fail();}

    void equal(Object x, Object y) {

        if (x == null ? y == null : x.equals(y)) pass();

        else fail(x + " not equal to " + y);}

    public static void main(String[] args) throws Throwable {

        new ZeroCoreThreads().instanceMain(args);}

    void instanceMain(String[] args) throws Throwable {

        try {test(args);} catch (Throwable t) {unexpected(t);}

        System.out.printf("%nPassed = %d, failed = %d%n%n", passed, failed);

        if (failed > 0) throw new AssertionError("Some tests failed");}

}