Added support for generating occurrences for a given period for recur…

…ring components

src/main/java/net/fortuna/ical4j/model/RecurrenceSupport.java

@@ -0,0 +1,77 @@
+/*
+ *  Copyright (c) 2023, Ben Fortuna
+ *  All rights reserved.
+ *
+ *  Redistribution and use in source and binary forms, with or without
+ *  modification, are permitted provided that the following conditions
+ *  are met:
+ *
+ *   o Redistributions of source code must retain the above copyright
+ *  notice, this list of conditions and the following disclaimer.
+ *
+ *   o Redistributions in binary form must reproduce the above copyright
+ *  notice, this list of conditions and the following disclaimer in the
+ *  documentation and/or other materials provided with the distribution.
+ *
+ *   o Neither the name of Ben Fortuna nor the names of any other contributors
+ *  may be used to endorse or promote products derived from this software
+ *  without specific prior written permission.
+ *
+ *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ *  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ *  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ *  A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ *  CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ *  EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ *  PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ *  PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ *  LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ *  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ *  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+package net.fortuna.ical4j.model;
+
+import net.fortuna.ical4j.model.component.CalendarComponent;
+import net.fortuna.ical4j.model.property.RecurrenceId;
+
+import java.io.IOException;
+import java.net.URISyntaxException;
+import java.text.ParseException;
+import java.util.ArrayList;
+import java.util.List;
+
+public interface RecurrenceSupport<T extends CalendarComponent> extends PropertyContainer {
+
+    <C extends Component> C copy() throws ParseException, IOException, URISyntaxException;
+
+    /**
+     * Calculates the recurrence set for this component using the specified period.
+     * The recurrence set is derived from a combination of the component start date,
+     * recurrence rules and dates, and exception rules and dates. Note that component
+     * transparency and anniversary-style dates do not affect the resulting
+     * intersection.
+     * <p>If an explicit DURATION is not specified, the effective duration of each
+     * returned period is derived from the DTSTART and DTEND or DUE properties.
+     * If the component has no DURATION, DTEND or DUE, the effective duration is set
+     * to PT0S</p>
+     *
+     * @param period a range to calculate recurrences for
+     * @return a list of periods
+     */
+    PeriodList calculateRecurrenceSet(final Period period);
+
+    default List<T> getOccurrences(Period period) throws ParseException, IOException, URISyntaxException {
+        List<T> occurrences = new ArrayList<>();
+
+        PeriodList periods = RecurrenceSupport.this.calculateRecurrenceSet(period);
+        for (Period p : periods) {
+            final T occurrence = this.copy();
+            occurrence.getProperties().add(new RecurrenceId(p.getStart()));
+            occurrences.add(occurrence);
+        }
+
+        return occurrences;
+    }
+}

src/main/java/net/fortuna/ical4j/model/component/VEvent.java

@@ -190,7 +190,7 @@
  *
  * @author Ben Fortuna
  */
-public class VEvent extends CalendarComponent implements ComponentContainer<Component> {
+public class VEvent extends CalendarComponent implements ComponentContainer<Component>, RecurrenceSupport<VEvent> {
 
     private static final long serialVersionUID = 2547948989200697335L;
 
@@ -451,7 +451,9 @@ public final PeriodList getConsumedTime(final Date rangeStart,
      * @throws IOException where an error occurs reading data
      * @throws URISyntaxException where an invalid URI is encountered
      * @throws ParseException where an error occurs parsing data
+     * @deprecated use {@link RecurrenceSupport#getOccurrences(Period)}
      */
+    @Deprecated
     public final VEvent getOccurrence(final Date date) throws IOException,
         URISyntaxException, ParseException {
 

src/main/java/net/fortuna/ical4j/model/component/VJournal.java

@@ -100,7 +100,7 @@
  *
  * @author Ben Fortuna
  */
-public class VJournal extends CalendarComponent implements ComponentContainer<Component> {
+public class VJournal extends CalendarComponent implements ComponentContainer<Component>, RecurrenceSupport<VJournal> {
 
     private static final long serialVersionUID = -7635140949183238830L;
 

src/main/java/net/fortuna/ical4j/model/component/VToDo.java

@@ -112,7 +112,7 @@
  *
  * @author Ben Fortuna
  */
-public class VToDo extends CalendarComponent implements ComponentContainer<Component> {
+public class VToDo extends CalendarComponent implements ComponentContainer<Component>, RecurrenceSupport<VToDo> {
 
     private static final long serialVersionUID = -269658210065896668L;
 

src/test/groovy/net/fortuna/ical4j/model/RecurrenceSupportTest.groovy

@@ -0,0 +1,57 @@
+/*
+ *  Copyright (c) 2023, Ben Fortuna
+ *  All rights reserved.
+ *
+ *  Redistribution and use in source and binary forms, with or without
+ *  modification, are permitted provided that the following conditions
+ *  are met:
+ *
+ *   o Redistributions of source code must retain the above copyright
+ *  notice, this list of conditions and the following disclaimer.
+ *
+ *   o Redistributions in binary form must reproduce the above copyright
+ *  notice, this list of conditions and the following disclaimer in the
+ *  documentation and/or other materials provided with the distribution.
+ *
+ *   o Neither the name of Ben Fortuna nor the names of any other contributors
+ *  may be used to endorse or promote products derived from this software
+ *  without specific prior written permission.
+ *
+ *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ *  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ *  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ *  A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ *  CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ *  EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ *  PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ *  PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ *  LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ *  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ *  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+package net.fortuna.ical4j.model
+
+import net.fortuna.ical4j.model.component.VEvent
+import spock.lang.Specification
+
+class RecurrenceSupportTest extends Specification {
+
+    def 'test get occurrences for recurring event'() {
+        given: 'a recurring event'
+        VEvent event = new ContentBuilder().vevent {
+            summary('a recurring event')
+            dtstart('20230101T010000')
+            dtend('20230101T020000')
+            rrule('FREQ=WEEKLY;INTERVAL=2;BYDAY=SU')
+        }
+
+        expect: 'calculated occurrences match expected'
+        event.getOccurrences(new Period(period)).collect { it.getProperty('RECURRENCE-ID').value} == expectedOccurrences
+
+        where:
+        period                  | expectedOccurrences
+        '20230101T010000/P3W'   | ['20230101T010000', '20230115T010000']
+    }
+}