<?php
  
  namespace Sabre\VObject;
  
  /**
   * DateTimeParser
   *
   * This class is responsible for parsing the several different date and time
   * formats iCalendar and vCards have.
   *

   * @copyright Copyright (C) 2007-2013 fruux GmbH (https://fruux.com/).
   * @author Evert Pot (http://evertpot.com/)

   * @license http://code.google.com/p/sabredav/wiki/License Modified BSD License
   */
  class DateTimeParser {
  
      /**
       * Parses an iCalendar (rfc5545) formatted datetime and returns a DateTime object
       *
       * Specifying a reference timezone is optional. It will only be used
       * if the non-UTC format is used. The argument is used as a reference, the
       * returned DateTime object will still be in the UTC timezone.
       *
       * @param string $dt
       * @param DateTimeZone $tz
       * @return DateTime
       */
      static public function parseDateTime($dt,\DateTimeZone $tz = null) {
  
          // Format is YYYYMMDD + "T" + hhmmss
          $result = preg_match('/^([1-4][0-9]{3})([0-1][0-9])([0-3][0-9])T([0-2][0-9])([0-5][0-9])([0-5][0-9])([Z]?)$/',$dt,$matches);
  
          if (!$result) {
              throw new \LogicException('The supplied iCalendar datetime value is incorrect: ' . $dt);
          }
  
          if ($matches[7]==='Z' || is_null($tz)) {
              $tz = new \DateTimeZone('UTC');
          }
          $date = new \DateTime($matches[1] . '-' . $matches[2] . '-' . $matches[3] . ' ' . $matches[4] . ':' . $matches[5] .':' . $matches[6], $tz);
  
          // Still resetting the timezone, to normalize everything to UTC
          $date->setTimeZone(new \DateTimeZone('UTC'));
          return $date;
  
      }
  
      /**
       * Parses an iCalendar (rfc5545) formatted date and returns a DateTime object
       *
       * @param string $date
       * @return DateTime
       */
      static public function parseDate($date) {
  
          // Format is YYYYMMDD
          $result = preg_match('/^([1-4][0-9]{3})([0-1][0-9])([0-3][0-9])$/',$date,$matches);
  
          if (!$result) {
              throw new \LogicException('The supplied iCalendar date value is incorrect: ' . $date);
          }
  
          $date = new \DateTime($matches[1] . '-' . $matches[2] . '-' . $matches[3], new \DateTimeZone('UTC'));
          return $date;
  
      }
  
      /**
       * Parses an iCalendar (RFC5545) formatted duration value.
       *
       * This method will either return a DateTimeInterval object, or a string
       * suitable for strtotime or DateTime::modify.
       *
       * @param string $duration
       * @param bool $asString
       * @return DateInterval|string
       */
      static public function parseDuration($duration, $asString = false) {
  
          $result = preg_match('/^(?P<plusminus>\+|-)?P((?P<week>\d+)W)?((?P<day>\d+)D)?(T((?P<hour>\d+)H)?((?P<minute>\d+)M)?((?P<second>\d+)S)?)?$/', $duration, $matches);
          if (!$result) {
              throw new \LogicException('The supplied iCalendar duration value is incorrect: ' . $duration);
          }
  
          if (!$asString) {
              $invert = false;
              if ($matches['plusminus']==='-') {
                  $invert = true;
              }
  
  
              $parts = array(
                  'week',
                  'day',
                  'hour',
                  'minute',
                  'second',
              );
              foreach($parts as $part) {
                  $matches[$part] = isset($matches[$part])&&$matches[$part]?(int)$matches[$part]:0;
              }
  
  
              // We need to re-construct the $duration string, because weeks and
              // days are not supported by DateInterval in the same string.
              $duration = 'P';
              $days = $matches['day'];
              if ($matches['week']) {
                  $days+=$matches['week']*7;
              }
              if ($days)
                  $duration.=$days . 'D';
  
              if ($matches['minute'] || $matches['second'] || $matches['hour']) {
                  $duration.='T';
  
                  if ($matches['hour'])
                      $duration.=$matches['hour'].'H';
  
                  if ($matches['minute'])
                      $duration.=$matches['minute'].'M';
  
                  if ($matches['second'])
                      $duration.=$matches['second'].'S';
  
              }
  
              if ($duration==='P') {
                  $duration = 'PT0S';
              }
              $iv = new \DateInterval($duration);
              if ($invert) $iv->invert = true;
  
              return $iv;
  
          }
  
  
  
          $parts = array(
              'week',
              'day',
              'hour',
              'minute',
              'second',
          );
  
          $newDur = '';
          foreach($parts as $part) {
              if (isset($matches[$part]) && $matches[$part]) {
                  $newDur.=' '.$matches[$part] . ' ' . $part . 's';
              }
          }
  
          $newDur = ($matches['plusminus']==='-'?'-':'+') . trim($newDur);
          if ($newDur === '+') { $newDur = '+0 seconds'; };
          return $newDur;
  
      }
  
      /**
       * Parses either a Date or DateTime, or Duration value.
       *
       * @param string $date
       * @param DateTimeZone|string $referenceTZ
       * @return DateTime|DateInterval
       */
      static public function parse($date, $referenceTZ = null) {
  
          if ($date[0]==='P' || ($date[0]==='-' && $date[1]==='P')) {
              return self::parseDuration($date);
          } elseif (strlen($date)===8) {
              return self::parseDate($date);
          } else {
              return self::parseDateTime($date, $referenceTZ);
          }
  
      }
  
  
  }