001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      https://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.lang3.time;
018
019import java.util.TimeZone;
020import java.util.regex.Matcher;
021import java.util.regex.Pattern;
022
023/**
024 * Faster methods to produce custom time zones.
025 *
026 * @since 3.7
027 */
028public class FastTimeZone {
029
030    private static final Pattern GMT_PATTERN = Pattern.compile("^(?:(?i)GMT)?([+-])?(\\d\\d?)?(:?(\\d\\d?))?$");
031
032    private static final TimeZone GREENWICH = new GmtTimeZone(false, 0, 0);
033
034    /**
035     * Gets the GMT TimeZone.
036     *
037     * @return A TimeZone with a raw offset of zero.
038     */
039    public static TimeZone getGmtTimeZone() {
040        return GREENWICH;
041    }
042
043    /**
044     * Gets a TimeZone with GMT offsets.  A GMT offset must be either 'Z', or 'UTC', or match
045     * <em>(GMT)? hh?(:?mm?)?</em>, where h and m are digits representing hours and minutes.
046     *
047     * @param pattern The GMT offset
048     * @return A TimeZone with offset from GMT or null, if pattern does not match.
049     */
050    public static TimeZone getGmtTimeZone(final String pattern) {
051        if ("Z".equals(pattern) || "UTC".equals(pattern)) {
052            return GREENWICH;
053        }
054
055        final Matcher m = GMT_PATTERN.matcher(pattern);
056        if (m.matches()) {
057            final int hours = parseInt(m.group(2));
058            final int minutes = parseInt(m.group(4));
059            if (hours == 0 && minutes == 0) {
060                return GREENWICH;
061            }
062            return new GmtTimeZone(parseSign(m.group(1)), hours, minutes);
063        }
064        return null;
065    }
066
067    /**
068     * Gets a TimeZone, looking first for GMT custom ids, then falling back to Olson ids.
069     * A GMT custom id can be 'Z', or 'UTC', or has an optional prefix of GMT,
070     * followed by sign, hours digit(s), optional colon(':'), and optional minutes digits.
071     * i.e. <em>[GMT] (+|-) Hours [[:] Minutes]</em>
072     *
073     * @param id A GMT custom id (or Olson id
074     * @return A time zone
075     */
076    public static TimeZone getTimeZone(final String id) {
077        final TimeZone tz = getGmtTimeZone(id);
078        if (tz != null) {
079            return tz;
080        }
081        return TimeZones.getTimeZone(id);
082    }
083
084    private static int parseInt(final String group) {
085        return group != null ? Integer.parseInt(group) : 0;
086    }
087
088    private static boolean parseSign(final String group) {
089        return group != null && group.charAt(0) == '-';
090    }
091
092    // do not instantiate
093    private FastTimeZone() {
094    }
095
096}