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/*
 * Copyright (C) 2014 the original author or authors.
 *
 * Licensed 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
 *
 *     http://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 ro.pippo.core.util;

import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;

/**
 * DateUtil adapted from Ninja Web Framework
 */
public class DateUtils {

    /**
     * From here: http://www.ietf.org/rfc/rfc1123.txt
     */
    static DateFormat getRFC1123_DateFormat() {
        return new SimpleDateFormat("EEE, dd MMM yyyy HH:mm:ss 'GMT'", Locale.US);
    }

    /**
     * Can be used to format a date into http header compatible strings.
     * 
     * It can be used to generate something like: Date: Wed, 05 Sep 2012
     * 09:16:19 GMT Expires: Thu, 01 Jan 1970 00:00:00 GMT
     *
     * @param date The date to format
     * @return a http header compatible string like
     * "Thu, 01 Jan 1970 00:00:00 GMT"
     */
    public static String formatForHttpHeader(Date date) {
        return getRFC1123_DateFormat().format(date);
    }

    /**
     * Can be used to format a unix timestamp into http header compatible
     * strings.
     * 

     * It can be used to generate something like: Date: Wed, 05 Sep 2012
     * 09:16:19 GMT Expires: Thu, 01 Jan 1970 00:00:00 GMT
     *
     * @param unixTime The long (unixtime) to format
     * @return a http header compatible string like
     * "Thu, 01 Jan 1970 00:00:00 GMT"
     */
    public static String formatForHttpHeader(long unixTime) {
        return getRFC1123_DateFormat().format(new Date(unixTime));
    }

    /**
     * Can be used to parse http times. For instance something like a http
     * header Date: Tue, 26 Mar 2013 13:47:13 GMT
     * 
     * INFO: consider the JodaTime based
     * DateUtil.parseHttpDateFormatToDateTime(...) version
     *
     * @param httpDateFormat in http format: Date: Tue, 26 Mar 2013 13:47:13 GMT
     * @return A nice "Date" object containing that http timestamp.
     * @throws ParseException If something goes wrong.
     */
    public static Date parseHttpDateFormat(String httpDateFormat) throws ParseException {
        return parseHttpDateFormatToDateTime(httpDateFormat);
    }

    /**
     * Can be used to parse http times. For instance something like a http
     * header Date: Tue, 26 Mar 2013 13:47:13 GMT
     *
     * @param httpDateFormat in http format: Date: Tue, 26 Mar 2013 13:47:13 GMT
     * @return A nice "DateTime" (JodaTime) object containing that http
     * timestamp.
     * @throws ParseException If something goes wrong.
     */
    public static Date parseHttpDateFormatToDateTime(String httpDateFormat) throws ParseException {
        return getRFC1123_DateFormat().parse(httpDateFormat);
    }

}