/*
 * Copyright (c) 2023, 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.
 */

package org.openjdk.bench.java.math;

import java.math.BigInteger;
import java.util.Arrays;
import java.util.concurrent.TimeUnit;

import org.openjdk.jmh.annotations.Benchmark;
import org.openjdk.jmh.annotations.BenchmarkMode;
import org.openjdk.jmh.annotations.Fork;
import org.openjdk.jmh.annotations.Measurement;
import org.openjdk.jmh.annotations.Mode;
import org.openjdk.jmh.annotations.OutputTimeUnit;
import org.openjdk.jmh.annotations.Param;
import org.openjdk.jmh.annotations.Scope;
import org.openjdk.jmh.annotations.Setup;
import org.openjdk.jmh.annotations.State;
import org.openjdk.jmh.annotations.Warmup;
import org.openjdk.jmh.infra.Blackhole;

@BenchmarkMode(Mode.AverageTime)
@OutputTimeUnit(TimeUnit.NANOSECONDS)
@State(Scope.Thread)
@Warmup(iterations = 3, time = 5)
@Measurement(iterations = 3, time = 5)
@Fork(value = 3)
public class BigIntegerHashCode {

    public enum Group {S, M, L}

    @Param({"S", "M", "L"})
    private Group group;

    private static final int MAX_LENGTH = Arrays.stream(Group.values())
            .mapToInt(p -> getNumbersOfBits(p).length)
            .max()
            .getAsInt();

    private BigInteger[] numbers;

    @Setup
    public void setup() {
        int[] nBits = getNumbersOfBits(group);
        numbers = new BigInteger[MAX_LENGTH];
        for (int i = 0; i < MAX_LENGTH; i++) {
            numbers[i] = Shared.createSingle(nBits[i % nBits.length]);
        }
    }

    private static int[] getNumbersOfBits(Group p) {
        // the below arrays were derived from stats gathered from running tests in
        // the security area, which is the biggest client of BigInteger in JDK
        return switch (p) {
            case S -> new int[]{2, 7, 13, 64};
            case M -> new int[]{256, 384, 511, 512, 521, 767, 768};
            case L -> new int[]{1024, 1025, 2047, 2048, 2049, 3072, 4096, 5120, 6144};
        };
    }

    @Benchmark
    public void testHashCode(Blackhole bh) {
        for (var n : numbers)
            bh.consume(n.hashCode());
    }
}