/* This file is part of the project "Hilbert II" - http://www.qedeq.org" target="alexandria_uri">http://www.qedeq.org
    *
    * Copyright 2000-2014,  Michael Meyling <mime@qedeq.org>.
    *
    * "Hilbert II" 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 2 of the License, or (at your option) any later version.
    *
   * This program 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.
   */
  
  package org.qedeq.base.utility;
  
  import java.util.Calendar;
  import java.util.Date;
  import java.util.GregorianCalendar;
  import java.util.TimeZone;
  
  import org.apache.commons.lang.time.FastDateFormat;
  
  /**
   * Various methods for date and time handling.
   *
   * @author Michael Meyling
   */
  public final class DateUtility {
  
      /** ISO 8601 date and time format. */
      public static final FastDateFormat ISO_8601_TIMESTAMP_FORMATTER = FastDateFormat.getInstance(
          "yyyy-MM-dd'T'HH:mm:ss.SSS");
  
      /** ISO 8601 time format. */
      public static final FastDateFormat ISO_8601_TIME_FORMATTER = FastDateFormat.getInstance(
          "HH:mm:ss.SSS");
  
      /** Date format YYYYMMDD HHmm. */
      public static final FastDateFormat NICE_TIMESTAMP_FORMATTER = FastDateFormat.getInstance(
          "yyyy-MM-dd' 'HH:mm:ss.SSS");
  
      /** GMT timezone. */
      private static final TimeZone GMT = TimeZone.getTimeZone("GMT");
  
      /**
       * Hidden constructor.
       */
      private DateUtility() {
          // nothing to do
      }
  
      /**
       * Current timestamp in ISO 8601 format (date and time).
       *
       * @return  Current timestamp.
       */
      public static final String getIsoTimestamp() {
          return ISO_8601_TIMESTAMP_FORMATTER.format(new Date());
      }
  
      /**
       * Timestamp in ISO 8601 format (date and time).
       *
       * @param   date    Date to format.
       * @return  Timestamp.
       */
      public static final String getIsoTimestamp(final Date date) {
          return ISO_8601_TIMESTAMP_FORMATTER.format(date);
      }
  
      /**
       * Timestamp in ISO 8601 format (date and time).
       *
       * @param   millis  Time in UTC milliseconds from the epoch.
       * @return  Timestamp.
       */
      public static final String getIsoTimestamp(final long millis) {
          return ISO_8601_TIMESTAMP_FORMATTER.format(getDate(millis));
      }
  
      /**
       * Times in ISO 8601 format (time).
       *
       * @param   millis  Time in UTC milliseconds from the epoch.
       * @return  Times.
       */
      public static final String getIsoTime(final long millis) {
          return ISO_8601_TIME_FORMATTER.format(getDate(millis));
      }
  
      /**
       * Current timestamp as ISO 8601 date and time separated by space.
       *
       * @return  Current timestamp.
       */
      public static final String getTimestamp() {
          return NICE_TIMESTAMP_FORMATTER.format(new Date());
     }
 
     /**
      * Current GMT timestamp as ISO 8601 date and time separated by space.
      *
      * @return  Current GMT timestamp.
      */
     public static final String getGmtTimestamp() {
         return NICE_TIMESTAMP_FORMATTER.format(getCurrentGmtDate());
     }
 
     /**
      * Returns a current GMT date.
      *
      * @return  Current GMT date.
      */
     public static final Date getCurrentGmtDate() {
         final Calendar cal = Calendar.getInstance(GMT);
         final Calendar gmtDate = new GregorianCalendar();
         gmtDate.set(Calendar.MONTH, cal.get(Calendar.MONTH));
         gmtDate.set(Calendar.YEAR, cal.get(Calendar.YEAR));
         gmtDate.set(Calendar.DAY_OF_MONTH, cal.get(Calendar.DAY_OF_MONTH));
         gmtDate.set(Calendar.HOUR_OF_DAY, cal.get(Calendar.HOUR_OF_DAY));
         gmtDate.set(Calendar.MINUTE, cal.get(Calendar.MINUTE));
         gmtDate.set(Calendar.SECOND, cal.get(Calendar.SECOND));
         return gmtDate.getTime();
     }
 
     /**
      * Convert millisecond duration into readable time amount.
      *
      * @param   milliseconds    Duration in milliseconds.
      * @return  Time in format "[d day[s] ]HH:mm:ss.SSS".
      */
     public static final String getDuration(final long milliseconds) {
         final StringBuffer buffer = new StringBuffer();
         long factor = 1000 * 60 * 60 * 24;
         long rest = milliseconds;
         long mod = 0;
 
         // days
         mod = rest / factor;
         rest = rest % factor;
         if (mod > 0) {
             buffer.append(mod);
             buffer.append(" day");
             if (mod > 1) {
                 buffer.append("s");
             }
             buffer.append(" ");
         }
 
         // hours
         factor = factor / 24;
         mod = rest / factor;
         rest = rest % factor;
         buffer.append(StringUtility.format(mod, 2));
 
         buffer.append(":");
 
         // minutes
         factor = factor / 60;
         mod = rest / factor;
         rest = rest % factor;
         buffer.append(StringUtility.format(mod, 2));
 
         buffer.append(":");
 
         // seconds
         factor = factor / 60;
         mod = rest / factor;
         rest = rest % factor;
         buffer.append(StringUtility.format(mod, 2));
 
         buffer.append(".");
 
         // milliseconds
         factor = factor / 1000;
         mod = rest / factor;
         // rest = rest % factor;
         buffer.append(StringUtility.format(mod, 3));
 
         return buffer.toString();
     }
 
     /**
      * Transform milliseconds from the epoch into date.
      *
      * @param   millis  Time in UTC milliseconds from the epoch.
      * @return  Date.
      */
     public static final Date getDate(final long millis) {
         final Calendar calendar = Calendar.getInstance();
         calendar.setTimeInMillis(millis);
         return calendar.getTime();
     }
 
 }