// Copyright (C) 2015 The Android Open Source Project
//
// 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.gerrit.testutil;

import static com.google.common.base.Preconditions.checkState;
import static java.util.concurrent.TimeUnit.MILLISECONDS;

import org.eclipse.jgit.lib.Config;
import org.eclipse.jgit.storage.file.FileBasedConfig;
import org.eclipse.jgit.util.FS;
import org.eclipse.jgit.util.SystemReader;
import org.joda.time.DateTime;
import org.joda.time.DateTimeUtils;
import org.joda.time.DateTimeUtils.MillisProvider;
import org.joda.time.DateTimeZone;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicLong;

/** Static utility methods for dealing with dates and times in tests. */
public class TestTimeUtil {
  private static Long clockStepMs;
  private static AtomicLong clockMs;

  /**
   * Reset the clock to a known start point, then set the clock step.
   * <p>
   * The clock is initially set to 2009/09/30 17:00:00 -0400.
   *
   * @param clockStep amount to increment clock by on each lookup.
   * @param clockStepUnit time unit for {@code clockStep}.
   */
  public static synchronized void resetWithClockStep(
      long clockStep, TimeUnit clockStepUnit) {
    // Set an arbitrary start point so tests are more repeatable.
    clockMs = new AtomicLong(
        new DateTime(2009, 9, 30, 17, 0, 0, DateTimeZone.forOffsetHours(-4))
            .getMillis());
    setClockStep(clockStep, clockStepUnit);
  }

  /**
   * Set the clock step used by {@link com.google.gerrit.common.TimeUtil}.
   *
   * @param clockStep amount to increment clock by on each lookup.
   * @param clockStepUnit time unit for {@code clockStep}.
   */
  public static synchronized void setClockStep(
      long clockStep, TimeUnit clockStepUnit) {
    checkState(clockMs != null, "call resetWithClockStep first");
    clockStepMs = MILLISECONDS.convert(clockStep, clockStepUnit);
    DateTimeUtils.setCurrentMillisProvider(new MillisProvider() {
      @Override
      public long getMillis() {
        return clockMs.getAndAdd(clockStepMs);
      }
    });

    SystemReader.setInstance(null);
    final SystemReader defaultReader = SystemReader.getInstance();
    SystemReader r = new SystemReader() {
      @Override
      public String getHostname() {
        return defaultReader.getHostname();
      }

      @Override
      public String getenv(String variable) {
        return defaultReader.getenv(variable);
      }

      @Override
      public String getProperty(String key) {
        return defaultReader.getProperty(key);
      }

      @Override
      public FileBasedConfig openUserConfig(Config parent, FS fs) {
        return defaultReader.openUserConfig(parent, fs);
      }

      @Override
      public FileBasedConfig openSystemConfig(Config parent, FS fs) {
        return defaultReader.openSystemConfig(parent, fs);
      }

      @Override
      public long getCurrentTime() {
        return clockMs.getAndAdd(clockStepMs);
      }

      @Override
      public int getTimezone(long when) {
        return defaultReader.getTimezone(when);
      }
    };
    SystemReader.setInstance(r);
  }

  /**
   * Reset the clock to use the actual system clock.
   * <p>
   * As a side effect, resets the {@link SystemReader} to the original default
   * instance.
   */
  public static synchronized void useSystemTime() {
    DateTimeUtils.setCurrentMillisSystem();
    SystemReader.setInstance(null);
  }

  private TestTimeUtil() {
  }
}