001/*
002 * SonarQube
003 * Copyright (C) 2009-2017 SonarSource SA
004 * mailto:info AT sonarsource DOT com
005 *
006 * This program is free software; you can redistribute it and/or
007 * modify it under the terms of the GNU Lesser General Public
008 * License as published by the Free Software Foundation; either
009 * version 3 of the License, or (at your option) any later version.
010 *
011 * This program is distributed in the hope that it will be useful,
012 * but WITHOUT ANY WARRANTY; without even the implied warranty of
013 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014 * Lesser General Public License for more details.
015 *
016 * You should have received a copy of the GNU Lesser General Public License
017 * along with this program; if not, write to the Free Software Foundation,
018 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
019 */
020package org.sonar.api.utils.internal;
021
022import java.util.Random;
023import java.util.concurrent.atomic.AtomicLong;
024import java.util.function.Supplier;
025import org.sonar.api.utils.System2;
026
027import static com.google.common.base.Preconditions.checkArgument;
028
029/**
030 * A subclass of {@link System2} which implementation of {@link System2#now()} always return a bigger value than the
031 * previous returned value.
032 * <p>
033 * This class is intended to be used in Unit tests.
034 * </p>
035 */
036public class AlwaysIncreasingSystem2 extends System2 {
037  private final AtomicLong now;
038  private final long increment;
039
040  private AlwaysIncreasingSystem2(Supplier<Long> initialValueSupplier, long increment) {
041    checkArgument(increment > 0, "increment must be > 0");
042    long initialValue = initialValueSupplier.get();
043    checkArgument(initialValue >= 0, "Initial value must be >= 0");
044    this.now = new AtomicLong(initialValue);
045    this.increment = increment;
046  }
047
048  public AlwaysIncreasingSystem2(long increment) {
049    this(AlwaysIncreasingSystem2::randomInitialValue, increment);
050  }
051
052  public AlwaysIncreasingSystem2(long initialValue, int increment) {
053    this(() -> initialValue, increment);
054  }
055
056  /**
057   * Values returned by {@link #now()} will start with a random value and increment by 100.
058   */
059  public AlwaysIncreasingSystem2() {
060    this(AlwaysIncreasingSystem2::randomInitialValue, 100);
061  }
062
063  @Override
064  public long now() {
065    return now.getAndAdd(increment);
066  }
067
068  private static long randomInitialValue() {
069    return (long) Math.abs(new Random().nextInt(2_000_000));
070  }
071}