/*
    * 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;
 	}
 }