/*
    * 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 static net.fortuna.ical4j.model.parameter.Value.DATE_TIME;
  
  import net.fortuna.ical4j.model.DateList;
  import net.fortuna.ical4j.model.DateTime;
  import net.fortuna.ical4j.model.Period;
  import net.fortuna.ical4j.model.Recur;
  import net.fortuna.ical4j.model.TimeZoneRegistry;
  import net.fortuna.ical4j.model.TimeZoneRegistryFactory;
  import net.fortuna.ical4j.model.property.RRule;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.text.SimpleDateFormat;
  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 static final TimeZoneRegistry registry = TimeZoneRegistryFactory.getInstance().createRegistry();
  
    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 rRule, final Date start, final TimeZone tz) {
      final Recur 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> calculatePeriods(Date start, Date end, long duration, RRule 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> calculatePeriods(
       Calendar startCalTz, Calendar endCalTz, long duration, Recur recur, TimeZone tz) {
     SimpleDateFormat simpleDateFormat = new SimpleDateFormat("EE MMM dd HH:mm:ss zzz yyyy");
     simpleDateFormat.setTimeZone(tz);
     String tzStr = tz.getID();
     List<Period> event = new LinkedList<>();
     logger.debug("Inbound start of recurrence {} to end of recurrence {}, in Tz {}",
         simpleDateFormat.format(startCalTz.getTime()),
         simpleDateFormat.format(endCalTz.getTime()), tzStr);
 
     DateTime periodStart = new DateTime(startCalTz.getTime());
     logger.debug("ical4j timeZone for {} is {}", tzStr, registry.getTimeZone(tzStr).toZoneId());
     periodStart.setTimeZone(registry.getTimeZone(tzStr));
     DateTime periodEnd = new DateTime(endCalTz.getTime());
     periodEnd.setTimeZone(registry.getTimeZone(tzStr));
 
     logger.trace("is utc {}? Tz is {} ", periodStart.isUtc(), periodStart.getTimeZone().toZoneId());
     logger.debug("({}) Looking at recurrences for {} to {}, duration {}, {}", periodStart.getTimeZone().toZoneId(),
         simpleDateFormat.format(new Date(periodStart.getTime())),
         simpleDateFormat.format(new Date(periodEnd.getTime())), duration, recur.toString());
 
     DateList dates = recur.getDates(periodStart, periodEnd, DATE_TIME);
     logger.trace("Got {} dates: {}, tz '{}'", dates.size(), dates.toString(), dates.getTimeZone().toZoneId());
 
     for (Date date : dates) {
       Date endTZ = new DateTime(date.getTime() + duration);
       DateTime startDT = new DateTime(date);
       DateTime endDT = new DateTime(endTZ);
       Period p = new Period(startDT, endDT);
       event.add(p);
     }
     for (Period e: event) {
       Calendar cal = Calendar.getInstance(e.getStart().getTimeZone());
       cal.setTimeInMillis(e.getStart().getTime());
       logger.debug("EventList start {} Instance {}, calendar hour {}, zone {}",
           e.getStart().toString(),
           simpleDateFormat.format(cal.getTime()),
           cal.get(Calendar.HOUR_OF_DAY),
           e.getStart().getTimeZone().toZoneId());
     }
     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;
   }
 }