/*
    * This file is part of ***  M y C o R e  ***
    * See http://www.mycore.de/ for details.
    *
    * MyCoRe is free software: you can redistribute it and/or modify
    * it under the terms of the GNU General Public License as published by
    * the Free Software Foundation, either version 3 of the License, or
    * (at your option) any later version.
    *
   * MyCoRe is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with MyCoRe.  If not, see <http://www.gnu.org/licenses/>.
   */
  
  package org.mycore.mods;
  
  import static org.mycore.mods.MCRMODSDateFormat.DATE_LOCALE;
  import static org.mycore.mods.MCRMODSDateFormat.MODS_TIMEZONE;
  
  import java.text.ParseException;
  import java.util.Calendar;
  import java.util.Date;
  import java.util.GregorianCalendar;
  import java.util.Objects;
  
  import org.jdom2.Element;
  import org.mycore.common.MCRException;
  
  /**
   * Helper class to parse and build MODS date elements, see
   * http://www.loc.gov/standards/mods/userguide/generalapp.html#encoding
   * 
   * @author Frank L\u00FCtzenkirchen
   */
  public class MCRMODSDateHelper {
  
      public static Date getDate(Element element) {
          if (element == null) {
              return null;
          }
  
          String text = element.getTextTrim();
          if ((text == null) || text.isEmpty()) {
              return null;
          }
  
          String encoding = element.getAttributeValue("encoding", "unknown").toLowerCase(DATE_LOCALE);
          String key = encoding + "-" + text.length();
          MCRMODSDateFormat format = firstNonNull(MCRMODSDateFormat.getFormat(key),
              MCRMODSDateFormat.getFormat(encoding));
          if (format == null) {
              throw reportParseException(encoding, text, null);
          }
          try {
              return format.parseDate(text);
          } catch (ParseException ex) {
              throw reportParseException(encoding, text, ex);
          }
      }
  
      @SafeVarargs
      private static <T> T firstNonNull(T... o) {
          for (T test : Objects.requireNonNull(o)) {
              if (test != null) {
                  return test;
              }
          }
          throw new NullPointerException();
      }
  
      public static GregorianCalendar getCalendar(Element element) {
          Date date = getDate(element);
          if (date == null) {
              return null;
          }
          GregorianCalendar cal = new GregorianCalendar(MODS_TIMEZONE, DATE_LOCALE);
          cal.setTime(date);
          return cal;
      }
  
      public static void setDate(Element element, Date date, MCRMODSDateFormat encoding) {
          Objects.requireNonNull(encoding, "encoding is required: " + encoding);
          element.setText(encoding.formatDate(date));
          element.setAttribute("encoding", encoding.asEncodingAttributeValue());
      }
  
      public static void setDate(Element element, GregorianCalendar cal, MCRMODSDateFormat encoding) {
          setDate(element, encoding.isDateOnly() ? adjustTimeOffset(cal) : cal.getTime(), encoding);
      }
  
      private static Date adjustTimeOffset(GregorianCalendar cal) {
          GregorianCalendar clone = new GregorianCalendar(MODS_TIMEZONE, DATE_LOCALE);
          clone.set(cal.get(Calendar.YEAR),
              cal.get(Calendar.MONTH),
              cal.get(Calendar.DAY_OF_MONTH));
         return clone.getTime();
     }
 
     private static MCRException reportParseException(String encoding, String text, ParseException ex) {
         String msg = "Unable to parse MODS date encoded " + encoding + " " + text;
         return new MCRException(msg, ex);
     }
 }