content: /*
   * The Alluxio Open Foundation licenses this work under the Apache License, version 2.0
   * (the "License"). You may not use this work except in compliance with the License, which is
   * available at www.apache.org/licenses/LICENSE-2.0
   *
   * This software is distributed on an "AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
   * either express or implied, as more fully set forth in the License.
   *
   * See the NOTICE file distributed with this work for information regarding copyright ownership.
   */
  
  package alluxio.heartbeat;
  
  import com.google.common.base.Preconditions;
  import org.apache.logging.log4j.core.util.CronExpression;
  
  import java.time.Duration;
  import java.time.Instant;
  import java.util.Date;
  import java.util.Objects;
  
  /**
  * Calculate the next interval by given cron expression.
  */
  public class CronExpressionIntervalSupplier implements SleepIntervalSupplier {
    private final long mInterval;
    private final CronExpression mCron;
  
    /**
     * Constructs a new {@link CronExpressionIntervalSupplier}.
     *
     * @param cronExpression the cron expression
     * @param fixedInterval the fixed interval
     */
    public CronExpressionIntervalSupplier(CronExpression cronExpression, long fixedInterval) {
      Preconditions.checkNotNull(cronExpression, "CronExpression is null");
      mInterval = fixedInterval;
      mCron = cronExpression;
    }
  
    @Override
    public long getNextInterval(long previousTickedMs, long nowTimeStampMillis) {
      long nextInterval = 0;
      long executionTimeMs = nowTimeStampMillis - previousTickedMs;
      if (executionTimeMs < mInterval) {
        nextInterval = mInterval - executionTimeMs;
      }
      Date now = Date.from(Instant.ofEpochMilli(nowTimeStampMillis + nextInterval));
      if (mCron.isSatisfiedBy(now)) {
        return nextInterval;
      }
      return nextInterval + Duration.between(
          now.toInstant(), mCron.getNextValidTimeAfter(now).toInstant()).toMillis();
    }
  
    @Override
    public long getRunLimit(long previousTickedMs) {
      Date now = Date.from(Instant.ofEpochMilli(previousTickedMs));
      return Duration.between(now.toInstant(),
          mCron.getNextInvalidTimeAfter(now).toInstant()).toMillis();
    }
  
    @Override
    public boolean equals(Object o) {
      if (this == o) {
        return true;
      }
      if (o == null || getClass() != o.getClass()) {
        return false;
      }
      CronExpressionIntervalSupplier that = (CronExpressionIntervalSupplier) o;
      return mInterval == that.mInterval
          && Objects.equals(mCron.getCronExpression(), that.mCron.getCronExpression());
    }
  
    @Override
    public int hashCode() {
      return Objects.hash(mInterval, mCron.getCronExpression());
    }
  }
  