Util.java

/*
 * Licensed to The Apereo Foundation under one or more contributor license
 * agreements. See the NOTICE file distributed with this work for additional
 * information regarding copyright ownership.
 *
 *
 * The Apereo Foundation licenses this file to you under the Educational
 * Community 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://opensource.org/licenses/ecl2.txt
 *
 * 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 org.opencastproject.scheduler.api;

import net.fortuna.ical4j.model.Period;
import net.fortuna.ical4j.model.Recur;
import net.fortuna.ical4j.model.property.RRule;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.text.SimpleDateFormat;
import java.time.Duration;
import java.time.ZoneId;
import java.time.ZoneOffset;
import java.time.ZonedDateTime;
import java.util.Calendar;
import java.util.Date;
import java.util.LinkedList;
import java.util.List;
import java.util.TimeZone;

public final class Util {
  /** The minimum separation between one event ending and the next starting */
  public static final int EVENT_MINIMUM_SEPARATION_MILLISECONDS = 0;

  private static final Logger logger = LoggerFactory.getLogger(Util.class);

  private Util() {
  }


  /**
   * Adjust the given UTC rrule to the given timezone.
   *
   * @param rRule The rrule to adjust.
   * @param start The start date in UTC
   *
   * @param tz The target timezone.
   */
  public static void adjustRrule(final RRule<ZonedDateTime> rRule, final Date start, final TimeZone tz) {
    final Recur<ZonedDateTime> recur = rRule.getRecur();
    if (recur.getHourList().size() != 1 || recur.getMinuteList().size() != 1) {
      throw new IllegalArgumentException(
          "RRules with multiple hours/minutes are not supported by Opencast. " + recur.toString());
    }
    final ZonedDateTime adjustedDate = ZonedDateTime.ofInstant(start.toInstant(), ZoneOffset.UTC)
            .withHour(recur.getHourList().get(0))
            .withMinute(recur.getMinuteList().get(0))
            .withZoneSameInstant(tz.toZoneId());
    recur.getHourList().set(0, adjustedDate.getHour());
    recur.getMinuteList().set(0, adjustedDate.getMinute());
  }

  /**
   * Backward compatibility, converts parameters as required for the updated calculatePeriods
   *
   * @param start date in the scheduled time zone
   * @param end date in the scheduled time zone
   * @param duration
   * @param rRule
   * @param tz, time zone of the scheduled event
   * @return the calculated periods
   */
  public static List<Period<ZonedDateTime>> calculatePeriods(Date start, Date end, long duration,
          RRule<ZonedDateTime> rRule, TimeZone tz) {
    Calendar startCal = Calendar.getInstance(tz);
    Calendar endCal = Calendar.getInstance(tz);
    startCal.setTime(start);
    endCal.setTime(end);
    return Util.calculatePeriods(startCal, endCal, duration, rRule.getRecur(), tz);
  }

  /**
   * Given a start time and end time with a recurrence rule and a timezone, all periods of the recurrence rule are
   * calculated taken daylight saving time into account.
   *
   * @param startCalTz, Calendar date time of the recurrence in the timezone of the scheduled CA
   * @param endCalTz, Calendar date time of the recurrence in the timezone of the scheduled CA
   * @param duration, the length of each event
   * @param recur, the recurrence rule (based on the Start time zone, including start hour and days of week)
   * @param tz, the timezone of the scheduled CA
   * @return a list of event Periods that match the rule and start and end times
   */
  public static List<Period<ZonedDateTime>> calculatePeriods(
      Calendar startCalTz, Calendar endCalTz, long duration, Recur<ZonedDateTime> recur, TimeZone tz) {
    SimpleDateFormat simpleDateFormat = new SimpleDateFormat("EE MMM dd HH:mm:ss zzz yyyy");
    simpleDateFormat.setTimeZone(tz);
    String tzStr = tz.getID();
    List<Period<ZonedDateTime>> event = new LinkedList<>();
    logger.debug("Inbound start of recurrence {} to end of recurrence {}, in Tz {}",
        simpleDateFormat.format(startCalTz.getTime()),
        simpleDateFormat.format(endCalTz.getTime()), tzStr);

    ZoneId zoneId = tz.toZoneId();
    logger.debug("ical4j timeZone for {} is {}", tzStr, zoneId);
    ZonedDateTime periodStart = startCalTz.toInstant().atZone(zoneId);
    ZonedDateTime periodEnd = endCalTz.toInstant().atZone(zoneId);

    logger.debug("({}) Looking at recurrences for {} to {}, duration {}, {}", zoneId,
        simpleDateFormat.format(Date.from(periodStart.toInstant())),
        simpleDateFormat.format(Date.from(periodEnd.toInstant())), duration, recur.toString());

    List<ZonedDateTime> dates = recur.getDates(periodStart, periodEnd);
    logger.trace("Got {} dates: {}, tz '{}'", dates.size(), dates, zoneId);

    for (ZonedDateTime date : dates) {
      ZonedDateTime endDT = date.plus(Duration.ofMillis(duration));
      Period<ZonedDateTime> p = new Period<>(date, endDT);
      event.add(p);
    }
    for (Period<ZonedDateTime> e: event) {
      ZonedDateTime eStart = e.getStart();
      logger.debug("EventList start {} Instance {}, calendar hour {}, zone {}",
          eStart, eStart, eStart.getHour(), eStart.getZone());
    }
    return event;
  }

  /**
   * Check if two intervals (for example, for two scheduled events), overlap.
   * @param start1 start of first interval
   * @param end1 end of first interval
   * @param start2 start of second interval
   * @param end2 end of second interval
   * @return <code>true</code> if they overlap, <code>false</code> if they don't
   */
  public static boolean schedulingIntervalsOverlap(
      final Date start1, final Date end1, final Date start2, final Date end2) {
    return end2.after(start1) && end1.after(start2)
        || eventWithinMinimumSeparation(start1, end1, start2, end2);
  }

  /**
   * Returns true of checkStart is within EVENT_MINIMUM_SEPARATION_SECONDS of either the start or end dates, or checkEnd
   * is within EVENT_MINIMUM_SEPARATION_SECONDS of either the start or end dates.  False otherwise
   */
  private static boolean eventWithinMinimumSeparation(Date checkStart, Date checkEnd, Date start, Date end) {
    return Math.abs(checkStart.getTime() - start.getTime()) < EVENT_MINIMUM_SEPARATION_MILLISECONDS
        || Math.abs(checkStart.getTime() - end.getTime()) < EVENT_MINIMUM_SEPARATION_MILLISECONDS
        || Math.abs(checkEnd.getTime() - start.getTime()) < EVENT_MINIMUM_SEPARATION_MILLISECONDS
        || Math.abs(checkEnd.getTime() - end.getTime()) < EVENT_MINIMUM_SEPARATION_MILLISECONDS;
  }
}