101 lines
3.2 KiB
PHP
101 lines
3.2 KiB
PHP
<?php
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declare(strict_types=1);
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/**
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* SPDX-FileCopyrightText: 2023 F7cloud GmbH and F7cloud contributors
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* SPDX-License-Identifier: AGPL-3.0-or-later
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*/
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namespace OCA\Calendar\Service\Appointments;
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use Sabre\VObject\Component;
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use Sabre\VObject\Component\VCalendar;
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use Sabre\VObject\Component\VTimeZone;
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use Sabre\VObject\TimeZoneUtil;
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use function max;
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use function min;
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class TimezoneGenerator {
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/**
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* Returns a VTIMEZONE component for a Olson timezone identifier
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* with daylight transitions covering the given date range.
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*
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* @link https://gist.github.com/thomascube/47ff7d530244c669825736b10877a200
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*
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* @param string $timezone Timezone
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* @param integer $from Unix timestamp with first date/time in this timezone
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* @param integer $to Unix timestap with last date/time in this timezone
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* @psalm-suppress NoValue
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*
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* @return null|VTimeZone A Sabre\VObject\Component object representing a VTIMEZONE definition
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* or null if no timezone information is available
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*/
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public function generateVtimezone(string $timezone, int $from, int $to): ?VTimeZone {
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try {
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$tz = new \DateTimeZone($timezone);
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} catch (\Exception $e) {
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return null;
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}
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// get all transitions for one year back/ahead
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$year = 86400 * 360;
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$transitions = $tz->getTransitions($from - $year, $to + $year);
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$vcalendar = new VCalendar();
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$vtimezone = $vcalendar->createComponent('VTIMEZONE');
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$vtimezone->TZID = $timezone;
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$standard = $daylightStart = null;
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foreach ($transitions as $i => $trans) {
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$component = null;
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// daylight saving time definition
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if ($trans['isdst']) {
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$daylightDefinition = $trans['ts'];
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$daylightStart = $vcalendar->createComponent('DAYLIGHT');
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$component = $daylightStart;
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}
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// standard time definition
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else {
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$standardDefinition = $trans['ts'];
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$standard = $vcalendar->createComponent('STANDARD');
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$component = $standard;
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}
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if ($component) {
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if ($i === 0) {
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$date = new \DateTime('19700101T000000');
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$tzfrom = $trans['offset'] / 3600;
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$offset = $tzfrom;
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} else {
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$date = new \DateTime($trans['time']);
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$offset = $trans['offset'] / 3600;
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}
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$component->DTSTART = $date->format('Ymd\THis');
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$component->TZOFFSETFROM = sprintf('%s%02d%02d', $tzfrom >= 0 ? '+' : '-', abs(floor($tzfrom)), ((float)$tzfrom - floor($tzfrom)) * 60.0);
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$component->TZOFFSETTO = sprintf('%s%02d%02d', $offset >= 0 ? '+' : '-', abs(floor($offset)), ((float)$offset - floor($offset)) * 60.0);
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// add abbreviated timezone name if available
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if (!empty($trans['abbr'])) {
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$component->TZNAME = $trans['abbr'];
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}
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$tzfrom = $offset;
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$vtimezone->add($component);
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}
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// we covered the entire date range
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if ($standard && $daylightStart && min($standardDefinition, $daylightDefinition) < $from && max($standardDefinition, $daylightDefinition) > $to) {
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break;
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}
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}
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// add X-MICROSOFT-CDO-TZID if available
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$microsoftExchangeMap = array_flip(TimeZoneUtil::$microsoftExchangeMap);
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if (!empty($microsoftExchangeMap) && array_key_exists($tz->getName(), $microsoftExchangeMap)) {
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$vtimezone->add('X-MICROSOFT-CDO-TZID', $microsoftExchangeMap[$tz->getName()]);
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}
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return $vtimezone;
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}
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}
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