/*
 * Copyright (c) "Neo4j"
 * Neo4j Sweden AB [http://neo4j.com]
 *
 * This file is part of Neo4j.
 *
 * Neo4j is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program 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 for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
package org.neo4j.internal.batchimport;

import static java.lang.Math.max;
import static org.junit.jupiter.api.Assertions.assertEquals;

import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ThreadLocalRandom;
import java.util.concurrent.atomic.AtomicLongArray;
import org.junit.jupiter.api.Test;
import org.neo4j.test.Race;

class HighestIdTest {
    @Test
    void shouldKeepHighest() throws Throwable {
        // GIVEN
        Race race = new Race();
        HighestId highestId = new HighestId();
        int threads = Runtime.getRuntime().availableProcessors();
        CountDownLatch latch = new CountDownLatch(threads);
        AtomicLongArray highestIds = new AtomicLongArray(threads);
        for (int c = 0; c < threads; c++) {
            int cc = c;
            race.addContestant(new Runnable() {
                boolean run;
                final ThreadLocalRandom random = ThreadLocalRandom.current();

                @Override
                public void run() {
                    if (run) {
                        return;
                    }

                    long highest = 0;
                    for (int i = 0; i < 10; i++) {
                        long nextLong = random.nextLong(100);
                        highestId.offer(nextLong);
                        highest = max(highest, nextLong);
                    }
                    highestIds.set(cc, highest);
                    latch.countDown();
                    run = true;
                }
            });
        }
        race.withEndCondition(() -> latch.getCount() == 0);

        // WHEN
        race.go();

        long highest = 0;
        for (int i = 0; i < threads; i++) {
            highest = max(highest, highestIds.get(i));
        }
        assertEquals(highest, highestId.get());
    }
}
