/*
    * Copyright 2003 - 2013 The eFaps Team
    *
    * 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.
   *
   * Revision:        $Rev$
   * Last Changed:    $Date$
   * Last Changed By: $Author$
   */
  
  package org.efaps.util;
  
  import java.sql.ResultSet;
  import java.sql.SQLException;
  import java.sql.Statement;
  import java.sql.Timestamp;
  import java.util.Date;
  
  import org.efaps.admin.EFapsSystemConfiguration;
  import org.efaps.admin.KernelSettings;
  import org.efaps.db.Context;
  import org.efaps.db.transaction.ConnectionResource;
  import org.joda.time.DateTime;
  import org.joda.time.DateTimeZone;
  import org.joda.time.chrono.ISOChronology;
  import org.joda.time.format.ISODateTimeFormat;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * Date and time utility class to handle the time zone from the eFaps
   * correctly.
   *
   * @author The eFaps Team
   * @version $Id$
   */
  public final class DateTimeUtil
  {
      /**
       * Logging instance used to give logging information of this class.
       */
      private static final Logger LOG = LoggerFactory.getLogger(DateTimeUtil.class);
  
      /**
       * Private constructor so that no instance of this utility class could be
       * created.
       */
      private DateTimeUtil()
      {
      }
  
      /**
       * Static method to get the current time stamp from the eFaps database.
       *
       * @return time stamp containing the current time of the eFaps database
       * @throws EFapsException on error
       */
      public static Timestamp getCurrentTimeFromDB() throws EFapsException
      {
          Timestamp now = null;
          final ConnectionResource rsrc = Context.getThreadContext().getConnectionResource();
          Statement stmt;
          try {
              stmt = rsrc.getConnection().createStatement();
              final ResultSet resultset = stmt.executeQuery("SELECT " + Context.getDbType().getCurrentTimeStamp());
              resultset.next();
              now = resultset.getTimestamp(1);
              resultset.close();
              stmt.close();
              rsrc.commit();
          } catch (final SQLException e) {
              DateTimeUtil.LOG.error("could not execute SQL-Statement", e);
          }
          return now;
      }
  
      /**
       * The given DateTime will be normalized to ISO calendar with time zone
       * from {@link EFapsSystemConfiguration#KERNEL kernel system configuration}
       * "Admin_Common_DataBaseTimeZone". In case that the
       * system configuration is missing "UTC" will be used.
       *
       * @param _date     date to normalize
       * @return DateTime normalized for the database
       * @throws EFapsException on error
       */
      public static DateTime normalize(final DateTime _date)
          throws EFapsException
      {
         // reads the Value from "Admin_Common_DataBaseTimeZone"
         final String timezoneID = EFapsSystemConfiguration.get().getAttributeValue(KernelSettings.DBTIMEZONE);
         final ISOChronology chron;
         if (timezoneID != null) {
             final DateTimeZone timezone = DateTimeZone.forID(timezoneID);
             chron = ISOChronology.getInstance(timezone);
         } else {
             chron = ISOChronology.getInstanceUTC();
         }
         return _date.withChronology(chron);
     }
 
     /**
      * The value that can be set is a Date, a DateTime or a String
      * yyyy-MM-dd'T'HH:mm:ss.SSSZZ. It will be normalized to ISO Calender with
      * TimeZone from SystemAttribute Admin_Common_DataBaseTimeZone. In case
      * that the SystemAttribute is missing UTC will be used.
      *
      *
      * @param _value    value from user interface to translate
      * @return translated date time
      * @throws EFapsException on error
      */
     public static DateTime translateFromUI(final Object _value)
         throws EFapsException
     {
         final DateTime ret;
         // reads the Value from "Admin_Common_DataBaseTimeZone"
         final String timezoneID = EFapsSystemConfiguration.get().getAttributeValue(KernelSettings.DBTIMEZONE);
         final ISOChronology chron;
         if (timezoneID != null) {
             final DateTimeZone timezone = DateTimeZone.forID(timezoneID);
             chron = ISOChronology.getInstance(timezone);
         } else {
             chron = ISOChronology.getInstanceUTC();
         }
         if (_value instanceof Date) {
             ret = new DateTime(_value).withChronology(chron);
         } else if (_value instanceof DateTime) {
             ret = ((DateTime) _value).withChronology(chron);
         } else if (_value instanceof String) {
             ret = ISODateTimeFormat.dateTime().parseDateTime((String) _value).withChronology(chron);
         } else  {
             ret = null;
         }
         return ret;
     }
 }