/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.lang3.time;

import java.util.TimeZone;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * Faster methods to produce custom time zones.
 *
 * @since 3.7
 */
public class FastTimeZone {

    private static final Pattern GMT_PATTERN = Pattern.compile("^(?:(?i)GMT)?([+-])?(\\d\\d?)?(:?(\\d\\d?))?$");

    private static final TimeZone GREENWICH = new GmtTimeZone(false, 0, 0);

    /**
     * Gets the GMT TimeZone.
     *
     * @return A TimeZone with a raw offset of zero.
     */
    public static TimeZone getGmtTimeZone() {
        return GREENWICH;
    }

    /**
     * Gets a TimeZone with GMT offsets.  A GMT offset must be either 'Z', or 'UTC', or match
     * <em>(GMT)? hh?(:?mm?)?</em>, where h and m are digits representing hours and minutes.
     *
     * @param pattern The GMT offset
     * @return A TimeZone with offset from GMT or null, if pattern does not match.
     */
    public static TimeZone getGmtTimeZone(final String pattern) {
