DateTimeUtils.java

/**
 * Copyright (c) 2010-2016 by the respective copyright holders.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 */
package org.openhab.binding.astro.internal.util;

import java.util.Calendar;
import java.util.Date;

import org.apache.commons.lang.time.DateUtils;
import org.openhab.binding.astro.internal.model.Range;

/**
 * Common used DateTime functions.
 *
 * @author Gerhard Riegler
 * @since 1.6.0
 */
public class DateTimeUtils {
    public static final double J1970 = 2440588.0;
    public static final double MILLISECONDS_PER_DAY = 1000 * 60 * 60 * 24;

    /**
     * Truncates the time from the calendar object.
     */
    public static Calendar truncateToMidnight(Calendar calendar) {
        return DateUtils.truncate(calendar, Calendar.DAY_OF_MONTH);
    }

    /**
     * Creates a Range object within the specified months and days. The start
     * time is midnight, the end time is end of the day.
     */
    public static Range getRange(int startYear, int startMonth, int startDay, int endYear, int endMonth, int endDay) {
        Calendar start = Calendar.getInstance();
        start.set(Calendar.YEAR, startYear);
        start.set(Calendar.MONTH, startMonth);
        start.set(Calendar.DAY_OF_MONTH, startDay);
        start = truncateToMidnight(start);

        Calendar end = Calendar.getInstance();
        end.set(Calendar.YEAR, endYear);
        end.set(Calendar.MONTH, endMonth);
        end.set(Calendar.DAY_OF_MONTH, endDay);
        end.set(Calendar.HOUR_OF_DAY, 23);
        end.set(Calendar.MINUTE, 59);
        end.set(Calendar.SECOND, 59);
        end.set(Calendar.MILLISECOND, 999);

        return new Range(start, end);
    }

    /**
     * Returns a calendar object from a julian date.
     */
    public static Calendar toCalendar(double julianDate) {
        if (Double.compare(julianDate, Double.NaN) == 0 || julianDate == 0) {
            return null;
        }
        long millis = (long) ((julianDate + 0.5 - J1970) * MILLISECONDS_PER_DAY);
        Calendar cal = Calendar.getInstance();
        cal.setTimeInMillis(millis);
        return DateUtils.round(cal, Calendar.MINUTE);
    }

    /**
     * Returns the julian date from the calendar object.
     */
    public static double dateToJulianDate(Calendar calendar) {
        return calendar.getTimeInMillis() / MILLISECONDS_PER_DAY - 0.5 + J1970;
    }

    /**
     * Returns the midnight julian date from the calendar object.
     */
    public static double midnightDateToJulianDate(Calendar calendar) {
        return dateToJulianDate(truncateToMidnight(calendar));
    }

    /**
     * Returns the end of day julian date from the calendar object.
     */
    public static double endOfDayDateToJulianDate(Calendar calendar) {
        Calendar cal = (Calendar) calendar.clone();
        cal = DateUtils.ceiling(cal, Calendar.DATE);
        cal.add(Calendar.MILLISECOND, -1);
        return dateToJulianDate(cal);
    }

    /**
     * Returns the year of the calendar object as a decimal value.
     */
    public static double getDecimalYear(Calendar calendar) {
        return calendar.get(Calendar.YEAR)
                + (double) calendar.get(Calendar.DAY_OF_YEAR) / calendar.getActualMaximum(Calendar.DAY_OF_YEAR);
    }

    /**
     * Converts the time (hour.minute) to a calendar object.
     */
    public static Calendar timeToCalendar(Calendar calendar, double time) {
        if (time < 0.0) {
            return null;
        }
        Calendar cal = (Calendar) calendar.clone();
        int hour = 0;
        int minute = 0;
        if (time == 24.0) {
            cal.add(Calendar.DAY_OF_MONTH, 1);
        } else {
            hour = (int) time;
            minute = (int) ((time * 100) - (hour * 100));
        }
        cal.set(Calendar.HOUR_OF_DAY, hour);
        cal.set(Calendar.MINUTE, minute);
        return DateUtils.truncate(cal, Calendar.MINUTE);
    }

    /**
     * Returns true, if two calendar objects are on the same day ignoring time.
     */
    public static boolean isSameDay(Calendar cal1, Calendar cal2) {
        return cal1 != null && cal2 != null && DateUtils.isSameDay(cal1, cal2);
    }

    /**
     * Returns a date object from a calendar.
     */
    public static Date getDate(Calendar calendar) {
        return calendar == null ? null : calendar.getTime();
    }

    /**
     * Returns the next Calendar from today.
     */
    public static Calendar getNext(Calendar... calendars) {
        Calendar now = Calendar.getInstance();
        Calendar next = null;
        for (Calendar calendar : calendars) {
            if (calendar.after(now) && (next == null || calendar.before(next))) {
                next = calendar;
            }
        }
        return next;
    }

    /**
     * Returns the midnight Calendar for the first day next year.
     */
    public static Calendar getFirstDayOfNextYear() {
        Calendar cal = Calendar.getInstance();
        cal.set(Calendar.DAY_OF_YEAR, 1);
        cal.set(Calendar.YEAR, cal.get(Calendar.YEAR) + 1);
        return truncateToMidnight(cal);
    }
}