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DSpace OAI-PMH Extension
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/**
 * The contents of this file are subject to the license and copyright
 * detailed in the LICENSE and NOTICE files at the root of the source
 * tree and available online at
 *
 * http://www.dspace.org/license/
 */
package org.dspace.xoai.util;

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

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

/**
 * @author Lyncode Development Team (dspace at lyncode dot com)
 */
public class DateUtils {

    private static Logger log = LogManager.getLogger(DateUtils.class);

    /**
     * Default constructor
     */
    private DateUtils() { }

    /**
     * Format a Date object as a valid UTC Date String, per OAI-PMH guidelines
     * http://www.openarchives.org/OAI/openarchivesprotocol.html#DatestampsResponses
     *
     * @param date Date object
     * @return UTC date string
     */
    public static String format(Date date) {
        // NOTE: OAI-PMH REQUIRES that all dates be expressed in UTC format
        // as YYYY-MM-DDThh:mm:ssZ  For more details, see
        // http://www.openarchives.org/OAI/openarchivesprotocol.html#DatestampsResponses
        SimpleDateFormat sdf = new SimpleDateFormat(
            "yyyy-MM-dd'T'HH:mm:ss'Z'");
        // We indicate that the returned date is in UTC so we have
        // to set the time zone of sdf correctly
        sdf.setTimeZone(TimeZone.getTimeZone("UTC"));
        String ret = sdf.format(date);
        return ret;
    }

    /**
     * Parse a string into a Date object
     *
     * @param date string to parse
     * @return Date
     */
    public static Date parse(String date) {
        // First try to parse as a full UTC date/time, e.g. 2008-01-01T00:00:00Z
        SimpleDateFormat format = new SimpleDateFormat(
            "yyyy-MM-dd'T'HH:mm:ss'Z'");
        format.setTimeZone(TimeZone.getTimeZone("UTC"));
        Date ret;
        try {
            ret = format.parse(date);
            return ret;
        } catch (ParseException ex) {
            // If a parse exception, try other logical date/time formats
            // based on the local timezone
            format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss",
                                          Locale.getDefault());
            try {
                return format.parse(date);
            } catch (ParseException e1) {
                format = new SimpleDateFormat("yyyy-MM-dd",
                                              Locale.getDefault());
                try {
                    return format.parse(date);
                } catch (ParseException e2) {
                    format = new SimpleDateFormat("yyyy-MM",
                                                  Locale.getDefault());
                    try {
                        return format.parse(date);
                    } catch (ParseException e3) {
                        format = new SimpleDateFormat("yyyy",
                                                      Locale.getDefault());
                        try {
                            return format.parse(date);
                        } catch (ParseException e4) {
                            log.error(e4.getMessage(), e4);
                        }
                    }
                }
            }
        }
        return new Date();
    }

    public static Date parseFromSolrDate(String date) {
        SimpleDateFormat format = new SimpleDateFormat(
            "yyyy-MM-dd'T'HH:mm:ss'Z'");
        format.setTimeZone(TimeZone.getTimeZone("UTC"));
        Date ret;
        try {
            ret = format.parse(date);
            return ret;
        } catch (ParseException e) {
            log.error(e.getMessage(), e);
        }
        return new Date();
    }
}