// Copyright 2014 The Bazel Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//    http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package com.google.devtools.build.lib.testutil;

import com.google.devtools.build.lib.clock.Clock;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.time.Duration;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicLong;

/**
 * A fake clock for testing.
 */
public final class ManualClock implements Clock {
  private final AtomicLong currentTimeMillis = new AtomicLong();

  @Override
  public long currentTimeMillis() {
    return currentTimeMillis.get();
  }

  /**
   * Nano time should not be confused with wall time. Nano time is only mean to compute time
   * differences. Because of this, we shift the time returned by 1000s, to test that the users
   * of this class do not rely on nanoTime == currentTimeMillis.
   */
  @Override
  public long nanoTime() {
    return TimeUnit.MILLISECONDS.toNanos(currentTimeMillis.get())
        + TimeUnit.SECONDS.toNanos(1000);
  }

  public long advanceMillis(long time) {
    return currentTimeMillis.addAndGet(time);
  }

  @CanIgnoreReturnValue
  public long advance(Duration duration) {
    return advanceMillis(duration.toMillis());
  }
}