kolab_sync_timezone_converter.php
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kolab_sync_timezone_converter.php
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	<?php

	/**
	* Tine 2.0
	*
	* @package ActiveSync
	* @license http://www.tine20.org/licenses/agpl-nonus.txt AGPL Version 1 (Non-US)
	* NOTE: According to sec. 8 of the AFFERO GENERAL PUBLIC LICENSE (AGPL),
	* Version 1, the distribution of the Tine 2.0 ActiveSync module in or to the
	* United States of America is excluded from the scope of this license.
	* @copyright Copyright (c) 2009 Metaways Infosystems GmbH (http://www.metaways.de)
	* @author Jonas Fischer <j.fischer@metaways.de>
	*/

	class kolab_sync_timezone_converter
	{
	/**
	* holds the instance of the singleton
	*
	* @var kolab_sync_timezone_onverter
	*/
	private static $_instance = NULL;

	protected $_startDate = array();

	/**
	* If set then the timezone guessing results will be cached.
	* This is strongly recommended for performance reasons.
	*
	* @var rcube_cache
	*/
	protected $cache = null;

	/**
	* array of offsets known by ActiceSync clients, but unknown by php
	* @var array
	*/
	protected $_knownTimezones = array(
	'0AIAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA==' => array(
	'Pacific/Kwajalein' => 'MHT'
	)
	);

	/**
	* don't use the constructor. Use the singleton.
	*
	* @param $_logger
	*/
	private function __construct()
	{
	}

	/**
	* don't clone. Use the singleton.
	*
	*/
	private function __clone()
	{
	}

	/**
	* the singleton pattern
	*
	* @return kolab_sync_timezone_converter
	*/
	public static function getInstance()
	{
	if (self::$_instance === NULL) {
	self::$_instance = new kolab_sync_timezone_converter();
	}

	return self::$_instance;
	}

	/**
	* Returns an array of timezones that match to the {@param $_offsets}
	*
	* If {@see $_expectedTimezone} is set then the method will terminate as soon
	* as the expected timezone has matched and the expected timezone will be the
	* first entry to the returned array.
	*
	* @param string\|array $_offsets
	*
	* @return array
	*/
	public function getListOfTimezones($_offsets)
	{
	if (is_string($_offsets) && isset($this->_knownTimezones[$_offsets])) {
	$timezones = $this->_knownTimezones[$_offsets];
	}
	else {
	if (is_string($_offsets)) {
	// unpack timezone info to array
	$_offsets = $this->_unpackTimezoneInfo($_offsets);
	}

	if (!$this->_validateOffsets($_offsets)) {
	return array();
	}
	$this->_setDefaultStartDateIfEmpty($_offsets);

	$cacheId = $this->_getCacheId('timezones', $_offsets);
	$timezones = $this->_loadFromCache($cacheId);

	if (!is_array($timezones)) {
	$timezones = array();
	foreach (DateTimeZone::listIdentifiers() as $timezoneIdentifier) {
	$timezone = new DateTimeZone($timezoneIdentifier);
	if (false !== ($matchingTransition = $this->_checkTimezone($timezone, $_offsets))) {
	$timezones[$timezoneIdentifier] = $matchingTransition['abbr'];
	}
	}
	$this->_saveInCache($timezones, $cacheId);
	}
	}

	// $this->_log(__METHOD__, __LINE__, 'Matching timezones: '.print_r($timezones, true));

	// if (empty($timezones)) {
	// throw new ActiveSync_TimezoneNotFoundException('No timezone found for the given offsets');
	// }

	return $timezones;
	}

	/**
	* Returns PHP timezone that matches to the {@param $_offsets}
	*
	* If {@see $_expectedTimezone} is set then the method will return this timezone if it matches.
	*
	* @param string\|array $_offsets Activesync timezone definition
	* @param string $_expectedTomezone Expected timezone name
	*
	* @return string Expected timezone name
	*/
	public function getTimezone($_offsets, $_expectedTimezone = null)
	{
	$timezones = $this->getListOfTimezones($_offsets);

	if ($_expectedTimezone && isset($timezones[$_expectedTimezone])) {
	return $_expectedTimezone;
	}
	else {
	return key($timezones);
	}
	}

	/**
	* Unpacks {@param $_packedTimezoneInfo} using {@see unpackTimezoneInfo} and then
	* calls {@see getTimezoneForOffsets} with the unpacked timezone info
	*
	* @param String $_packedTimezoneInfo
	* @return String [timezone abbreviation e.g. CET, MST etc.]
	*
	*/
	// public function getTimezoneForPackedTimezoneInfo($_packedTimezoneInfo)
	// {
	// $offsets = $this->_unpackTimezoneInfo($_packedTimezoneInfo);
	// $matchingTimezones = $this->getTimezoneForOffsets($offsets);
	// $maxMatches = 0;
	// $matchingAbbr = null;
	// foreach ($matchingTimezones as $abbr => $timezones) {
	// if (count($timezones) > $maxMatches) {
	// $maxMatches = count($timezones);
	// $matchingAbbr = $abbr;
	// }
	// }
	// return $matchingAbbr;
	// }

	/**
	* Return packed string for given {@param $_timezone}
	* @param String $_timezone
	* @param String \| int \| null $_startDate
	* @return String
	*/
	public function encodeTimezone($_timezone, $_startDate = null)
	{
	foreach ($this->_knownTimezones as $packedString => $knownTimezone) {
	if (array_key_exists($_timezone, $knownTimezone)) {
	return $packedString;
	}
	}

	$offsets = $this->getOffsetsForTimezone($_timezone, $_startDate);
	return $this->_packTimezoneInfo($offsets);
	}

	/**
	* get offsets for given timezone
	*
	* @param string $_timezone
	* @param $_startDate
	* @return array
	*/
	public function getOffsetsForTimezone($_timezone, $_startDate = null)
	{
	$this->_setStartDate($_startDate);

	$cacheId = $this->_getCacheId('offsets', array($_timezone));

	if (false === ($offsets = $this->_loadFromCache($cacheId))) {
	$offsets = $this->_getOffsetsTemplate();

	try {
	$timezone = new DateTimeZone($_timezone);
	}
	catch (Exception $e) {
	// $this->_log(__METHOD__, __LINE__, ": could not instantiate timezone {$_timezone}: {$e->getMessage()}");
	return null;
	}

	list($standardTransition, $daylightTransition) = $this->_getTransitionsForTimezoneAndYear($timezone, $this->_startDate['year']);

	if ($standardTransition) {
	$offsets['bias'] = $standardTransition['offset']/60*-1;
	if ($daylightTransition) {
	$offsets = $this->_generateOffsetsForTransition($offsets, $standardTransition, 'standard');
	$offsets = $this->_generateOffsetsForTransition($offsets, $daylightTransition, 'daylight');
	$offsets['standardHour'] += $daylightTransition['offset']/3600;
	$offsets['daylightHour'] += $standardTransition['offset']/3600;

	//@todo how do we get the standardBias (is usually 0)?
	//$offsets['standardBias'] = ...

	$offsets['daylightBias'] = ($daylightTransition['offset'] - $standardTransition['offset'])/60*-1;
	}
	}

	$this->_saveInCache($offsets, $cacheId);
	}

	return $offsets;
	}

	/**
	*
	*
	* @param array $_offsets
	* @param array $_transition
	* @param String $_type
	* @return array
	*/
	protected function _generateOffsetsForTransition(Array $_offsets, Array $_transition, $_type)
	{
	$transitionDateParsed = getdate($_transition['ts']);

	$_offsets[$_type . 'Month'] = $transitionDateParsed['mon'];
	$_offsets[$_type . 'DayOfWeek'] = $transitionDateParsed['wday'];
	$_offsets[$_type . 'Minute'] = $transitionDateParsed['minutes'];
	$_offsets[$_type . 'Hour'] = $transitionDateParsed['hours'];

	for ($i=5; $i>0; $i--) {
	if ($this->_isNthOcurrenceOfWeekdayInMonth($_transition['ts'], $i)) {
	$_offsets[$_type . 'Day'] = $i;
	break;
	};
	}

	return $_offsets;
	}

	/**
	* Test if the weekday of the given {@param $_timestamp} is the {@param $_occurence}th occurence of this weekday within its month.
	*
	* @param int $_timestamp
	* @param int $_occurence [1 to 5, where 5 indicates the final occurrence during the month if that day of the week does not occur 5 times]
	*
	* @return bool
	*/
	protected function _isNthOcurrenceOfWeekdayInMonth($_timestamp, $_occurence)
	{
	if ($_occurence <= 1) {
	return true;
	}

	$original = new DateTime('@'.$_timestamp);
	$orig = $original->format('n');

	if ($_occurence == 5) {
	$modified = clone($original);
	$modified->modify('1 week');
	$mod = $modified->format('n');

	// modified date is a next month
	return $mod > $orig \|\| ($mod == 1 && $orig == 12);
	}

	$modified = clone($original);
	$modified->modify(sprintf('-%d weeks', $_occurence - 1));
	$mod = $modified->format('n');

	if ($mod != $orig) {
	return false;
	}

	$modified = clone($original);
	$modified->modify(sprintf('-%d weeks', $_occurence));
	$mod = $modified->format('n');

	// modified month is earlier than original
	return $mod < $orig \|\| ($mod == 12 && $orig == 1);
	}

	/**
	* Check if the given {@param $_standardTransition} and {@param $_daylightTransition}
	* match to the object property {@see $_offsets}
	*
	* @param Array $standardTransition
	* @param Array $daylightTransition
	*
	* @return bool
	*/
	protected function _checkTransition($_standardTransition, $_daylightTransition, $_offsets)
	{
	if (empty($_standardTransition) \|\| empty($_offsets)) {
	return false;
	}

	$standardOffset = ($_offsets['bias'] + $_offsets['standardBias']) * 60 * -1;

	//check each condition in a single if statement and break the chain when one condition is not met - for performance reasons
	if ($standardOffset == $_standardTransition['offset'] ) {

	if (empty($_offsets['daylightMonth']) && (empty($_daylightTransition) \|\| empty($_daylightTransition['isdst']))) {
	//No DST
	return true;
	}

	$daylightOffset = ($_offsets['bias'] + $_offsets['daylightBias']) * 60 * -1;

	// the milestone is sending a positive value for daylightBias while it should send a negative value
	$daylightOffsetMilestone = ($_offsets['bias'] + ($_offsets['daylightBias'] * -1) ) * 60 * -1;

	if ($daylightOffset == $_daylightTransition['offset'] \|\| $daylightOffsetMilestone == $_daylightTransition['offset']) {
	$standardParsed = getdate($_standardTransition['ts']);
	$daylightParsed = getdate($_daylightTransition['ts']);

	if ($standardParsed['mon'] == $_offsets['standardMonth'] &&
	$daylightParsed['mon'] == $_offsets['daylightMonth'] &&
	$standardParsed['wday'] == $_offsets['standardDayOfWeek'] &&
	$daylightParsed['wday'] == $_offsets['daylightDayOfWeek']
	) {
	return $this->_isNthOcurrenceOfWeekdayInMonth($_daylightTransition['ts'], $_offsets['daylightDay']) &&
	$this->_isNthOcurrenceOfWeekdayInMonth($_standardTransition['ts'], $_offsets['standardDay']);
	}
	}
	}

	return false;
	}

	/**
	* decode timezone info from activesync
	*
	* @param string $_packedTimezoneInfo the packed timezone info
	* @return array
	*/
	protected function _unpackTimezoneInfo($_packedTimezoneInfo)
	{
	$timezoneUnpackString = 'lbias/a64standardName/vstandardYear/vstandardMonth/vstandardDayOfWeek/vstandardDay/vstandardHour/vstandardMinute/vstandardSecond/vstandardMilliseconds/lstandardBias/a64daylightName/vdaylightYear/vdaylightMonth/vdaylightDayOfWeek/vdaylightDay/vdaylightHour/vdaylightMinute/vdaylightSecond/vdaylightMilliseconds/ldaylightBias';

	$timezoneInfo = unpack($timezoneUnpackString, base64_decode($_packedTimezoneInfo));

	return $timezoneInfo;
	}

	/**
	* encode timezone info to activesync
	*
	* @param array $_timezoneInfo
	* @return string
	*/
	protected function _packTimezoneInfo($_timezoneInfo)
	{
	if (!is_array($_timezoneInfo)) {
	return null;
	}

	$packed = pack(
	"la64vvvvvvvvla64vvvvvvvvl",
	$_timezoneInfo['bias'],
	$_timezoneInfo['standardName'],
	$_timezoneInfo['standardYear'],
	$_timezoneInfo['standardMonth'],
	$_timezoneInfo['standardDayOfWeek'],
	$_timezoneInfo['standardDay'],
	$_timezoneInfo['standardHour'],
	$_timezoneInfo['standardMinute'],
	$_timezoneInfo['standardSecond'],
	$_timezoneInfo['standardMilliseconds'],
	$_timezoneInfo['standardBias'],
	$_timezoneInfo['daylightName'],
	$_timezoneInfo['daylightYear'],
	$_timezoneInfo['daylightMonth'],
	$_timezoneInfo['daylightDayOfWeek'],
	$_timezoneInfo['daylightDay'],
	$_timezoneInfo['daylightHour'],
	$_timezoneInfo['daylightMinute'],
	$_timezoneInfo['daylightSecond'],
	$_timezoneInfo['daylightMilliseconds'],
	$_timezoneInfo['daylightBias']
	);

	return base64_encode($packed);
	}

	/**
	* Returns complete offsets array with all fields empty
	*
	* Used e.g. when reverse-generating ActiveSync Timezone Offset Information
	* based on a given Timezone, {@see getOffsetsForTimezone}
	*
	* @return unknown_type
	*/
	protected function _getOffsetsTemplate()
	{
	return array(
	'bias' => 0,
	'standardName' => '',
	'standardYear' => 0,
	'standardMonth' => 0,
	'standardDayOfWeek' => 0,
	'standardDay' => 0,
	'standardHour' => 0,
	'standardMinute' => 0,
	'standardSecond' => 0,
	'standardMilliseconds' => 0,
	'standardBias' => 0,
	'daylightName' => '',
	'daylightYear' => 0,
	'daylightMonth' => 0,
	'daylightDayOfWeek' => 0,
	'daylightDay' => 0,
	'daylightHour' => 0,
	'daylightMinute' => 0,
	'daylightSecond' => 0,
	'daylightMilliseconds' => 0,
	'daylightBias' => 0
	);
	}

	/**
	* Validate and set offsets
	*
	* @param array $value
	*
	* @return bool Validation result
	*/
	protected function _validateOffsets($value)
	{
	// validate $value
	if ((!empty($value['standardMonth']) \|\| !empty($value['standardDay']) \|\| !empty($value['daylightMonth']) \|\| !empty($value['daylightDay'])) &&
	(empty($value['standardMonth']) \|\| empty($value['standardDay']) \|\| empty($value['daylightMonth']) \|\| empty($value['daylightDay']))
	) {
	// It is not possible not set standard offsets without setting daylight offsets and vice versa
	return false;
	}

	return true;
	}

	/**
	* Parse and set object property {@see $_startDate}
	*
	* @param String \| int $_startDate
	* @return void
	*/
	protected function _setStartDate($_startDate)
	{
	if (empty($_startDate)) {
	$this->_setDefaultStartDateIfEmpty();
	return;
	}

	$startDateParsed = array();

	if (is_string($_startDate)) {
	$startDateParsed['string'] = $_startDate;
	$startDateParsed['ts'] = strtotime($_startDate);
	}
	else if (is_int($_startDate)) {
	$startDateParsed['ts'] = $_startDate;
	$startDateParsed['string'] = strftime('%F', $_startDate);
	}
	else {
	$this->_setDefaultStartDateIfEmpty();
	return;
	}

	$startDateParsed['object'] = new DateTime($startDateParsed['string']);

	$startDateParsed = array_merge($startDateParsed, getdate($startDateParsed['ts']));

	$this->_startDate = $startDateParsed;
	}

	/**
	* Set default value for object property {@see $_startdate} if it is not set yet.
	* Tries to guess the correct startDate depending on object property {@see $_offsets} and
	* falls back to current date.
	*
	* @param array $_offsets [offsets may be avaluated for a given start year]
	* @return void
	*/
	protected function _setDefaultStartDateIfEmpty($_offsets = null)
	{
	if (!empty($this->_startDate)) {
	return;
	}

	if (!empty($_offsets['standardYear'])) {
	$this->_setStartDate($_offsets['standardYear'].'-01-01');
	}
	else {
	$this->_setStartDate(time());
	}
	}

	/**
	* Check if the given {@param $_timezone} matches the {@see $_offsets}
	* and also evaluate the daylight saving time transitions for this timezone if necessary.
	*
	* @param DateTimeZone $timezone
	* @param array $offsets
	*
	* @return array\|bool
	*/
	protected function _checkTimezone(DateTimeZone $timezone, $offsets)
	{
	list($standardTransition, $daylightTransition) = $this->_getTransitionsForTimezoneAndYear($timezone, $this->_startDate['year']);
	if ($this->_checkTransition($standardTransition, $daylightTransition, $offsets)) {
	// echo 'Matching timezone ' . $timezone->getName();
	// echo 'Matching daylight transition ' . print_r($daylightTransition, 1);
	// echo 'Matching standard transition ' . print_r($standardTransition, 1);
	return $standardTransition;
	}

	return false;
	}

	/**
	* Returns the standard and daylight transitions for the given {@param $_timezone}
	* and {@param $_year}.
	*
	* @param DateTimeZone $_timezone
	* @param $_year
	* @return Array
	*/
	protected function _getTransitionsForTimezoneAndYear(DateTimeZone $_timezone, $_year)
	{
	$standardTransition = null;
	$daylightTransition = null;

	if (version_compare(PHP_VERSION, '5.3.0', '>=')) {
	// Since php version 5.3.0 getTransitions accepts optional start and end parameters.
	$start = mktime(0, 0, 0, 12, 1, $_year - 1);
	$end = mktime(24, 0, 0, 12, 31, $_year);
	$transitions = $_timezone->getTransitions($start, $end);
	} else {
	$transitions = $_timezone->getTransitions();
	}

	$index = 0; //we need to access index counter outside of the foreach loop
	$transition = array(); //we need to access the transition counter outside of the foreach loop
	foreach ($transitions as $index => $transition) {
	if (strftime('%Y', $transition['ts']) == $_year) {
	if (isset($transitions[$index+1]) && strftime('%Y', $transitions[$index]['ts']) == strftime('%Y', $transitions[$index+1]['ts'])) {
	$daylightTransition = $transition['isdst'] ? $transition : $transitions[$index+1];
	$standardTransition = $transition['isdst'] ? $transitions[$index+1] : $transition;
	}
	else {
	$daylightTransition = $transition['isdst'] ? $transition : null;
	$standardTransition = $transition['isdst'] ? null : $transition;
	}
	break;
	}
	else if ($index == count($transitions) -1) {
	$standardTransition = $transition;
	}
	}

	return array($standardTransition, $daylightTransition);
	}

	protected function _getCacheId($_prefix, $_offsets)
	{
	return $_prefix . md5(serialize($_offsets));
	}

	protected function _loadFromCache($key)
	{
	if ($cache = $this->getCache) {
	return $cache->get($key);
	}

	return false;
	}

	protected function _saveInCache($value, $key)
	{
	if ($cache = $this->getCache) {
	$cache->set($key, $value);
	}
	}

	/**
	* Getter for the cache engine object
	*/
	protected function getCache()
	{
	if ($this->cache === null) {
	$rcube = rcube::get_instance();
	$cache = $rcube->get_cache_shared('activesync');
	$this->cache = $cache ? $cache : false;
	}

	return $this->cache;
	}
	}

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