/*

 * Copyright (c) 2004, 2013, 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.

 *

 * 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.

 */

/*

 * @test

 * @bug 4486658 8010293

 * @summary thread safety of toArray methods of subCollections

 * @author Martin Buchholz

 */

import java.util.concurrent.CompletableFuture;

import java.util.concurrent.ConcurrentHashMap;

import java.util.stream.IntStream;

public class ToArray {

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

        // Execute a number of times to increase the probability of

        // failure if there is an issue

        for (int i = 0; i < 16; i++) {

            executeTest();

        }

    }

    static void executeTest() throws Throwable {

        final Throwable throwable[] = new Throwable[1];

        final ConcurrentHashMap<Integer, Integer> m = new ConcurrentHashMap<>();

        // Number of workers equal to the number of processors

        // Each worker will put globally unique keys into the map

        final int nWorkers = Runtime.getRuntime().availableProcessors();

        final int sizePerWorker = 1024;

        final int maxSize = nWorkers * sizePerWorker;

        // The foreman keeps checking that the size of the arrays

        // obtained from the key and value sets is never less than the

        // previously observed size and is never greater than the maximum size

        // NOTE: these size constraints are not specific to toArray and are

        // applicable to any form of traversal of the collection views

        CompletableFuture<?> foreman = CompletableFuture.runAsync(new Runnable() {

            private int prevSize = 0;

            private boolean checkProgress(Object[] a) {

                int size = a.length;

                if (size < prevSize) throw new RuntimeException("WRONG WAY");

                if (size > maxSize) throw new RuntimeException("OVERSHOOT");

                if (size == maxSize) return true;

                prevSize = size;

                return false;

            }

            @Override

            public void run() {

                try {

                    Integer[] empty = new Integer[0];

                    while (true) {

                        if (checkProgress(m.values().toArray())) return;

                        if (checkProgress(m.keySet().toArray())) return;

                        if (checkProgress(m.values().toArray(empty))) return;

                        if (checkProgress(m.keySet().toArray(empty))) return;

                    }

                }

                catch (Throwable t) {

                    throwable[0] = t;

                }

            }

        });

        // Create workers

        // Each worker will put globally unique keys into the map

        CompletableFuture<?>[] workers = IntStream.range(0, nWorkers).

                mapToObj(w -> CompletableFuture.runAsync(() -> {

                    for (int i = 0, o = w * sizePerWorker; i < sizePerWorker; i++)

                        m.put(o + i, i);

                })).

                toArray(CompletableFuture<?>[]::new);

        // Wait for workers and then foreman to complete

        CompletableFuture.allOf(workers).join();

        foreman.join();

        if (throwable[0] != null)

            throw throwable[0];

    }

}