RelativeDateFormatter.java

/*
 * Copyright (C) 2011, Matthias Sohn <matthias.sohn@sap.com> and others
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Distribution License v. 1.0 which is available at
 * https://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */
package org.eclipse.jgit.util;

import java.text.MessageFormat;
import java.util.Date;

import org.eclipse.jgit.internal.JGitText;

/**
 * Formatter to format timestamps relative to the current time using time units
 * in the format defined by {@code git log --relative-date}.
 */
public class RelativeDateFormatter {
    static final long SECOND_IN_MILLIS = 1000;

    static final long MINUTE_IN_MILLIS = 60 * SECOND_IN_MILLIS;

    static final long HOUR_IN_MILLIS = 60 * MINUTE_IN_MILLIS;

    static final long DAY_IN_MILLIS = 24 * HOUR_IN_MILLIS;

    static final long WEEK_IN_MILLIS = 7 * DAY_IN_MILLIS;

    static final long MONTH_IN_MILLIS = 30 * DAY_IN_MILLIS;

    static final long YEAR_IN_MILLIS = 365 * DAY_IN_MILLIS;

    /**
     * Get age of given {@link java.util.Date} compared to now formatted in the
     * same relative format as returned by {@code git log --relative-date}
     *
     * @param when
     *            {@link java.util.Date} to format
     * @return age of given {@link java.util.Date} compared to now formatted in
     *         the same relative format as returned by
     *         {@code git log --relative-date}
     */
    @SuppressWarnings("boxing")
    public static String format(Date when) {

        long ageMillis = SystemReader.getInstance().getCurrentTime()
                - when.getTime();

        // shouldn't happen in a perfect world
        if (ageMillis < 0)
            return JGitText.get().inTheFuture;

        // seconds
        if (ageMillis < upperLimit(MINUTE_IN_MILLIS))
            return MessageFormat.format(JGitText.get().secondsAgo,
                    round(ageMillis, SECOND_IN_MILLIS));

        // minutes
        if (ageMillis < upperLimit(HOUR_IN_MILLIS))
            return MessageFormat.format(JGitText.get().minutesAgo,
                    round(ageMillis, MINUTE_IN_MILLIS));

        // hours
        if (ageMillis < upperLimit(DAY_IN_MILLIS))
            return MessageFormat.format(JGitText.get().hoursAgo,
                    round(ageMillis, HOUR_IN_MILLIS));

        // up to 14 days use days
        if (ageMillis < 14 * DAY_IN_MILLIS)
            return MessageFormat.format(JGitText.get().daysAgo,
                    round(ageMillis, DAY_IN_MILLIS));

        // up to 10 weeks use weeks
        if (ageMillis < 10 * WEEK_IN_MILLIS)
            return MessageFormat.format(JGitText.get().weeksAgo,
                    round(ageMillis, WEEK_IN_MILLIS));

        // months
        if (ageMillis < YEAR_IN_MILLIS)
            return MessageFormat.format(JGitText.get().monthsAgo,
                    round(ageMillis, MONTH_IN_MILLIS));

        // up to 5 years use "year, months" rounded to months
        if (ageMillis < 5 * YEAR_IN_MILLIS) {
            long years = round(ageMillis, MONTH_IN_MILLIS) / 12;
            String yearLabel = (years > 1) ? JGitText.get().years : //
                    JGitText.get().year;
            long months = round(ageMillis - years * YEAR_IN_MILLIS,
                    MONTH_IN_MILLIS);
            String monthLabel = (months > 1) ? JGitText.get().months : //
                    (months == 1 ? JGitText.get().month : ""); //$NON-NLS-1$
            return MessageFormat.format(
                    months == 0 ? JGitText.get().years0MonthsAgo : JGitText
                            .get().yearsMonthsAgo,
                    new Object[] { years, yearLabel, months, monthLabel });
        }

        // years
        return MessageFormat.format(JGitText.get().yearsAgo,
                round(ageMillis, YEAR_IN_MILLIS));
    }

    private static long upperLimit(long unit) {
        long limit = unit + unit / 2;
        return limit;
    }

    private static long round(long n, long unit) {
        long rounded = (n + unit / 2) / unit;
        return rounded;
    }
}