/*
 * Copyright (C) 2012 Christian Halstrick 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.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.HashMap;
import java.util.Locale;
import java.util.Map;

import org.eclipse.jgit.internal.JGitText;

Parses strings with time and date specifications into Date. When git needs to parse strings specified by the user this parser can be used. One example is the parsing of the config parameter gc.pruneexpire. The parser can handle only subset of what native gits approxidate parser understands. /**
 * Parses strings with time and date specifications into {@link java.util.Date}.
 *
 * When git needs to parse strings specified by the user this parser can be
 * used. One example is the parsing of the config parameter gc.pruneexpire. The
 * parser can handle only subset of what native gits approxidate parser
 * understands.
 */
public class GitDateParser {
	
The Date representing never. Though this is a concrete value, most
callers are adviced to avoid depending on the actual value.
/**
	 * The Date representing never. Though this is a concrete value, most
	 * callers are adviced to avoid depending on the actual value.
	 */
	public static final Date NEVER = new Date(Long.MAX_VALUE);

	// Since SimpleDateFormat instances are expensive to instantiate they should
	// be cached. Since they are also not threadsafe they are cached using
	// ThreadLocal.
	private static ThreadLocal<Map<Locale, Map<ParseableSimpleDateFormat, SimpleDateFormat>>> formatCache =
			new ThreadLocal<Map<Locale, Map<ParseableSimpleDateFormat, SimpleDateFormat>>>() {

		@Override
		protected Map<Locale, Map<ParseableSimpleDateFormat, SimpleDateFormat>> initialValue() {
			return new HashMap<>();
		}
	};

	// Gets an instance of a SimpleDateFormat for the specified locale. If there
	// is not already an appropriate instance in the (ThreadLocal) cache then
	// create one and put it into the cache.
	private static SimpleDateFormat getDateFormat(ParseableSimpleDateFormat f,
			Locale locale) {
		Map<Locale, Map<ParseableSimpleDateFormat, SimpleDateFormat>> cache = formatCache
				.get();
		Map<ParseableSimpleDateFormat, SimpleDateFormat> map = cache
				.get(locale);
		if (map == null) {
			map = new HashMap<>();
			cache.put(locale, map);
			return getNewSimpleDateFormat(f, locale, map);
		}
		SimpleDateFormat dateFormat = map.get(f);
		if (dateFormat != null)
			return dateFormat;
		SimpleDateFormat df = getNewSimpleDateFormat(f, locale, map);
		return df;
	}

	private static SimpleDateFormat getNewSimpleDateFormat(
			ParseableSimpleDateFormat f, Locale locale,
			Map<ParseableSimpleDateFormat, SimpleDateFormat> map) {
		SimpleDateFormat df = SystemReader.getInstance().getSimpleDateFormat(
				f.formatStr, locale);
		map.put(f, df);
		return df;
	}

	// An enum of all those formats which this parser can parse with the help of
	// a SimpleDateFormat. There are other formats (e.g. the relative formats
	// like "yesterday" or "1 week ago") which this parser can parse but which
	// are not listed here because they are parsed without the help of a
	// SimpleDateFormat.
	enum ParseableSimpleDateFormat {
		ISO("yyyy-MM-dd HH:mm:ss Z"), // //$NON-NLS-1$
		RFC("EEE, dd MMM yyyy HH:mm:ss Z"), // //$NON-NLS-1$
		SHORT("yyyy-MM-dd"), // //$NON-NLS-1$
		SHORT_WITH_DOTS_REVERSE("dd.MM.yyyy"), // //$NON-NLS-1$
		SHORT_WITH_DOTS("yyyy.MM.dd"), // //$NON-NLS-1$
		SHORT_WITH_SLASH("MM/dd/yyyy"), // //$NON-NLS-1$
		DEFAULT("EEE MMM dd HH:mm:ss yyyy Z"), // //$NON-NLS-1$
		LOCAL("EEE MMM dd HH:mm:ss yyyy"); //$NON-NLS-1$

		private final String formatStr;

		private ParseableSimpleDateFormat(String formatStr) {
			this.formatStr = formatStr;
		}
	}

	
Parses a string into a Date using the default locale. Since this parser also supports relative formats (e.g. "yesterday") the caller can specify the reference date. These types of strings can be parsed: 

"never"
"now"
"yesterday"
"(x) years|months|weeks|days|hours|minutes|seconds ago"

Multiple specs can be combined like in "2 weeks 3 days ago". Instead of '
' one can use '.' to separate the words
"yyyy-MM-dd HH:mm:ss Z" (ISO)
"EEE, dd MMM yyyy HH:mm:ss Z" (RFC)
"yyyy-MM-dd"
"yyyy.MM.dd"
"MM/dd/yyyy",
"dd.MM.yyyy"
"EEE MMM dd HH:mm:ss yyyy Z" (DEFAULT)
"EEE MMM dd HH:mm:ss yyyy" (LOCAL)

Params:
dateStr – 
           the string to be parsed
now – 
           the base date which is used for the calculation of relative
           formats. E.g. if baseDate is "25.8.2012" then parsing of the
           string "1 week ago" would result in a date corresponding to
           "18.8.2012". This is used when a JGit command calls this
           parser often but wants a consistent starting point for
           calls.

           If set to null then the current time will be used
           instead.
Throws:
ParseException – 
            if the given dateStr was not recognized
Returns:
the parsed Date/**
	 * Parses a string into a {@link java.util.Date} using the default locale.
	 * Since this parser also supports relative formats (e.g. "yesterday") the
	 * caller can specify the reference date. These types of strings can be
	 * parsed:
	 * <ul>
	 * <li>"never"</li>
	 * <li>"now"</li>
	 * <li>"yesterday"</li>
	 * <li>"(x) years|months|weeks|days|hours|minutes|seconds ago"<br>
	 * Multiple specs can be combined like in "2 weeks 3 days ago". Instead of '
	 * ' one can use '.' to separate the words</li>
	 * <li>"yyyy-MM-dd HH:mm:ss Z" (ISO)</li>
	 * <li>"EEE, dd MMM yyyy HH:mm:ss Z" (RFC)</li>
	 * <li>"yyyy-MM-dd"</li>
	 * <li>"yyyy.MM.dd"</li>
	 * <li>"MM/dd/yyyy",</li>
	 * <li>"dd.MM.yyyy"</li>
	 * <li>"EEE MMM dd HH:mm:ss yyyy Z" (DEFAULT)</li>
	 * <li>"EEE MMM dd HH:mm:ss yyyy" (LOCAL)</li>
	 * </ul>
	 *
	 * @param dateStr
	 *            the string to be parsed
	 * @param now
	 *            the base date which is used for the calculation of relative
	 *            formats. E.g. if baseDate is "25.8.2012" then parsing of the
	 *            string "1 week ago" would result in a date corresponding to
	 *            "18.8.2012". This is used when a JGit command calls this
	 *            parser often but wants a consistent starting point for
	 *            calls.<br>
	 *            If set to <code>null</code> then the current time will be used
	 *            instead.
	 * @return the parsed {@link java.util.Date}
	 * @throws java.text.ParseException
	 *             if the given dateStr was not recognized
	 */
	public static Date parse(String dateStr, Calendar now)
			throws ParseException {
		return parse(dateStr, now, Locale.getDefault());
	}

	
Parses a string into a Date using the given locale. Since this parser also supports relative formats (e.g. "yesterday") the caller can specify the reference date. These types of strings can be parsed: 

"never"
"now"
"yesterday"
"(x) years|months|weeks|days|hours|minutes|seconds ago"

Multiple specs can be combined like in "2 weeks 3 days ago". Instead of '
' one can use '.' to separate the words
"yyyy-MM-dd HH:mm:ss Z" (ISO)
"EEE, dd MMM yyyy HH:mm:ss Z" (RFC)
"yyyy-MM-dd"
"yyyy.MM.dd"
"MM/dd/yyyy",
"dd.MM.yyyy"
"EEE MMM dd HH:mm:ss yyyy Z" (DEFAULT)
"EEE MMM dd HH:mm:ss yyyy" (LOCAL)

Params:
dateStr – 
           the string to be parsed
now – 
           the base date which is used for the calculation of relative
           formats. E.g. if baseDate is "25.8.2012" then parsing of the
           string "1 week ago" would result in a date corresponding to
           "18.8.2012". This is used when a JGit command calls this
           parser often but wants a consistent starting point for
           calls.

           If set to null then the current time will be used
           instead.
locale – 
           locale to be used to parse the date string
Throws:
ParseException – 
            if the given dateStr was not recognized
Returns:
the parsed Date
Since:
3.2/**
	 * Parses a string into a {@link java.util.Date} using the given locale.
	 * Since this parser also supports relative formats (e.g. "yesterday") the
	 * caller can specify the reference date. These types of strings can be
	 * parsed:
	 * <ul>
	 * <li>"never"</li>
	 * <li>"now"</li>
	 * <li>"yesterday"</li>
	 * <li>"(x) years|months|weeks|days|hours|minutes|seconds ago"<br>
	 * Multiple specs can be combined like in "2 weeks 3 days ago". Instead of '
	 * ' one can use '.' to separate the words</li>
	 * <li>"yyyy-MM-dd HH:mm:ss Z" (ISO)</li>
	 * <li>"EEE, dd MMM yyyy HH:mm:ss Z" (RFC)</li>
	 * <li>"yyyy-MM-dd"</li>
	 * <li>"yyyy.MM.dd"</li>
	 * <li>"MM/dd/yyyy",</li>
	 * <li>"dd.MM.yyyy"</li>
	 * <li>"EEE MMM dd HH:mm:ss yyyy Z" (DEFAULT)</li>
	 * <li>"EEE MMM dd HH:mm:ss yyyy" (LOCAL)</li>
	 * </ul>
	 *
	 * @param dateStr
	 *            the string to be parsed
	 * @param now
	 *            the base date which is used for the calculation of relative
	 *            formats. E.g. if baseDate is "25.8.2012" then parsing of the
	 *            string "1 week ago" would result in a date corresponding to
	 *            "18.8.2012". This is used when a JGit command calls this
	 *            parser often but wants a consistent starting point for
	 *            calls.<br>
	 *            If set to <code>null</code> then the current time will be used
	 *            instead.
	 * @param locale
	 *            locale to be used to parse the date string
	 * @return the parsed {@link java.util.Date}
	 * @throws java.text.ParseException
	 *             if the given dateStr was not recognized
	 * @since 3.2
	 */
	public static Date parse(String dateStr, Calendar now, Locale locale)
			throws ParseException {
		dateStr = dateStr.trim();
		Date ret;

		if ("never".equalsIgnoreCase(dateStr)) //$NON-NLS-1$
			return NEVER;
		ret = parse_relative(dateStr, now);
		if (ret != null)
			return ret;
		for (ParseableSimpleDateFormat f : ParseableSimpleDateFormat.values()) {
			try {
				return parse_simple(dateStr, f, locale);
			} catch (ParseException e) {
				// simply proceed with the next parser
			}
		}
		ParseableSimpleDateFormat[] values = ParseableSimpleDateFormat.values();
		StringBuilder allFormats = new StringBuilder("\"") //$NON-NLS-1$
				.append(values[0].formatStr);
		for (int i = 1; i < values.length; i++)
			allFormats.append("\", \"").append(values[i].formatStr); //$NON-NLS-1$
		allFormats.append("\""); //$NON-NLS-1$
		throw new ParseException(MessageFormat.format(
				JGitText.get().cannotParseDate, dateStr, allFormats.toString()), 0);
	}

	// tries to parse a string with the formats supported by SimpleDateFormat
	private static Date parse_simple(String dateStr,
			ParseableSimpleDateFormat f, Locale locale)
			throws ParseException {
		SimpleDateFormat dateFormat = getDateFormat(f, locale);
		dateFormat.setLenient(false);
		return dateFormat.parse(dateStr);
	}

	// tries to parse a string with a relative time specification
	@SuppressWarnings("nls")
	private static Date parse_relative(String dateStr, Calendar now) {
		Calendar cal;
		SystemReader sysRead = SystemReader.getInstance();

		// check for the static words "yesterday" or "now"
		if ("now".equals(dateStr)) {
			return ((now == null) ? new Date(sysRead.getCurrentTime()) : now
					.getTime());
		}

		if (now == null) {
			cal = new GregorianCalendar(sysRead.getTimeZone(),
					sysRead.getLocale());
			cal.setTimeInMillis(sysRead.getCurrentTime());
		} else
			cal = (Calendar) now.clone();

		if ("yesterday".equals(dateStr)) {
			cal.add(Calendar.DATE, -1);
			cal.set(Calendar.HOUR_OF_DAY, 0);
			cal.set(Calendar.MINUTE, 0);
			cal.set(Calendar.SECOND, 0);
			cal.set(Calendar.MILLISECOND, 0);
			cal.set(Calendar.MILLISECOND, 0);
			return cal.getTime();
		}

		// parse constructs like "3 days ago", "5.week.2.day.ago"
		String[] parts = dateStr.split("\\.| ");
		int partsLength = parts.length;
		// check we have an odd number of parts (at least 3) and that the last
		// part is "ago"
		if (partsLength < 3 || (partsLength & 1) == 0
				|| !"ago".equals(parts[parts.length - 1]))
			return null;
		int number;
		for (int i = 0; i < parts.length - 2; i += 2) {
			try {
				number = Integer.parseInt(parts[i]);
			} catch (NumberFormatException e) {
				return null;
			}
			if (parts[i + 1] == null){
				return null;
			}
			switch (parts[i + 1]) {
			case "year":
			case "years":
				cal.add(Calendar.YEAR, -number);
				break;
			case "month":
			case "months":
				cal.add(Calendar.MONTH, -number);
				break;
			case "week":
			case "weeks":
				cal.add(Calendar.WEEK_OF_YEAR, -number);
				break;
			case "day":
			case "days":
				cal.add(Calendar.DATE, -number);
				break;
			case "hour":
			case "hours":
				cal.add(Calendar.HOUR_OF_DAY, -number);
				break;
			case "minute":
			case "minutes":
				cal.add(Calendar.MINUTE, -number);
				break;
			case "second":
			case "seconds":
				cal.add(Calendar.SECOND, -number);
				break;
			default:
				return null;
			}
		}
		return cal.getTime();
	}
}