net.fortuna.ical4j.model.ComponentSequenceComparator Maven / Gradle / Ivy

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package net.fortuna.ical4j.model;

import net.fortuna.ical4j.model.property.DtStamp;
import net.fortuna.ical4j.model.property.Sequence;

import java.time.Instant;
import java.util.Comparator;

/**
 * A comparator to determine natural ordering of component instances based on
 * sequence information.
 *
 * See RFC5446 - Message Sequencing
 * for further details.
 */
public class ComponentSequenceComparator implements Comparator {

    @Override
    public int compare(Component o1, Component o2) {
        int retVal = 0;

        var defaultSequence = new Sequence(0);
        var sequence1 = (Sequence) o1.getProperty(Property.SEQUENCE).orElse(defaultSequence);
        var sequence2 = (Sequence) o2.getProperty(Property.SEQUENCE).orElse(defaultSequence);

        retVal = sequence1.compareTo(sequence2);
        if (retVal == 0) {
            var defaultDtStamp = new DtStamp(Instant.EPOCH);
            var dtStamp1 = (DtStamp) o1.getProperty(Property.DTSTAMP).orElse(defaultDtStamp);
            var dtStamp2 = (DtStamp) o2.getProperty(Property.DTSTAMP).orElse(defaultDtStamp);

            retVal = dtStamp1.compareTo(dtStamp2);
        }
        return retVal;
    }
}