CronSchedule.java

/*
 * Copyright 2015 Collective, Inc.
 *
 * Licensed under the Apache 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://www.apache.org/licenses/LICENSE-2.0
 *
 * 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 com.collective.celos;

import java.text.ParseException;
import java.util.Date;
import java.util.SortedSet;
import java.util.TreeSet;

import org.joda.time.DateTime;
import org.joda.time.DateTimeZone;
import org.quartz.CronExpression;

/**
 * Schedule implementation that uses cron-like syntax.
 */
public class CronSchedule implements Schedule {

    private CronExpression cronExpression;

    public CronSchedule(String cronConfig) {
        try {
            CronExpression.validateExpression(cronConfig);
            cronExpression = new CronExpression(cronConfig);
            cronExpression.setTimeZone(DateTimeZone.UTC.toTimeZone());
        } catch (ParseException e) {
            throw new IllegalArgumentException("Error in cron expression", e);
        }
    }

    public String getCronExpression() {
        return cronExpression.getCronExpression();
    }

    @Override
    public SortedSet<ScheduledTime> getScheduledTimes(Scheduler scheduler, ScheduledTime start, ScheduledTime end) {
        SortedSet<ScheduledTime> scheduledTimes = new TreeSet<ScheduledTime>();
        DateTime startDT = start.getDateTime();
        DateTime endDT = end.getDateTime();

        if (!startDT.isBefore(endDT)) {
            return scheduledTimes;
        }
        
        if (cronExpression.isSatisfiedBy(startDT.toDate())) {
            scheduledTimes.add(start);
        }

        DateTime candidate = startDT;
        while((candidate = getNextDateTime(candidate)) != null && candidate.isBefore(endDT)) {
            scheduledTimes.add(new ScheduledTime(candidate));
        }
        
        return scheduledTimes;
    }

    private DateTime getNextDateTime(DateTime candidate) {
        Date date = cronExpression.getNextValidTimeAfter(candidate.toDate());
        if (date != null) {
            return new DateTime(date, DateTimeZone.UTC);
        } else {
            return null;
        }
    }

}