groovysh that uses RRule

rrule.groovh

import groovy.grape.Grape

Grape.addResolver(name:'mvnRepository', root:'http://central.maven.org/maven2/')
Grape.addResolver(name:'kint', root:'http://nexus.k-int.com/content/repositories/releases')
Grape.grab(group:'org.scala-saddle', module:'google-rfc-2445',version:'20110304')

import com.google.ical.iter.RecurrenceIterator;
import com.google.ical.iter.RecurrenceIteratorFactory;
import com.google.ical.values.DateTimeValueImpl;
import com.google.ical.values.DateValue;
import com.google.ical.values.DateValueImpl;
import com.google.ical.values.Frequency;
import com.google.ical.values.RRule;
import com.google.ical.values.WeekdayNum;
import java.util.TimeZone;

rrule = new RRule('RRULE:FREQ=MINUTELY;COUNT=30;INTERVAL=15;WKST=MO');
startDateAsDV = new DateValueImpl(2019, 10, 1);
nextDate=null;

println("Create iterator");

iterator = RecurrenceIteratorFactory.createRecurrenceIterator(rrule, startDateAsDV, TimeZone.getDefault());

if(!iterator.hasNext()) {
  return -1;
}

println("get next date");
nextDate = iterator.next();

println("next date: ${nextDate}")