File ICal/Timezone/VTimezoneResolver.php

1:	<?php
2:	declare(strict_types=1);
3:
4:	namespace om\ICal\Timezone;
5:
6:	use DateTimeImmutable;
7:	use om\ICal\Component;
8:	use om\ICal\Value\Text;
9:	use om\TimezoneGuesser;
10:	use WeakMap;
11:
12:	/**
13:	* Resolves a TZID defined by a VTIMEZONE component of the calendar.
14:	*
15:	* PHP cannot create a timezone from custom rules, so the IANA timezone with the same
16:	* transitions around the reference date is used (see TimezoneGuesser), preferring the
17:	* timezone of the same name. A definition without transitions becomes a fixed offset.
18:	*/
19:	final class VTimezoneResolver implements TimezoneResolver {
20:	/** @var WeakMap<Component, array<string, ?ResolvedTimezone>> */
21:	private WeakMap $cache;
22:
23:	public function __construct(
24:	private readonly TimezoneResolver $names = new CompositeTimezoneResolver(new IanaTimezoneResolver(), new AliasTimezoneResolver()),
25:	private readonly ?DateTimeImmutable $reference = null,
26:	) {
27:	$this->cache = new WeakMap();
28:	}
29:
30:	public function resolve(string $tzid, Component $calendar): ?ResolvedTimezone {
31:	$cache = $this->cache[$calendar] ?? [];
32:	if (!array_key_exists($tzid, $cache)) {
33:	$cache[$tzid] = $this->find($tzid, $calendar);
34:	$this->cache[$calendar] = $cache;
35:	}
36:	return $cache[$tzid];
37:	}
38:
39:	private function find(string $tzid, Component $calendar): ?ResolvedTimezone {
40:	foreach ($calendar->components('VTIMEZONE') as $definition) {
41:	$defined = $definition->property('TZID')?->value;
42:	if ($defined === null \|\| Text::unescape($defined) !== $tzid) {
43:	continue;
44:	}
45:	// X-LIC-LOCATION (Mozilla) and the TZID itself name the intended zone
46:	$location = $definition->property('X-LIC-LOCATION')?->value;
47:	$named = array_values(array_unique(array_filter([
48:	$location === null ? null : $this->names->resolve($location, $calendar)?->timezone->getName(),
49:	$this->names->resolve($tzid, $calendar)?->timezone->getName(),
50:	])));
51:	$preferred = array_values(array_unique(AliasTimezoneResolver::windowsTimezones()));
52:	$timezone = TimezoneGuesser::guess(self::observances($definition), $this->reference, $preferred, $named);
53:	return $timezone === null ? null : new ResolvedTimezone($tzid, $timezone, TimezoneSource::VTimezone);
54:	}
55:	return null;
56:	}
57:
58:	/**
59:	* @return list<array{start: string, offsetFrom: string, offsetTo: string, rrule: ?string, rdates: list<string>}>
60:	*/
61:	public static function observances(Component $definition): array {
62:	$observances = [];
63:	foreach ($definition->components as $observance) {
64:	if ($observance->name !== 'STANDARD' && $observance->name !== 'DAYLIGHT') {
65:	continue;
66:	}
67:	$rdates = [];
68:	foreach ($observance->properties('RDATE') as $rdate) {
69:	array_push($rdates, ...explode(',', $rdate->value));
70:	}
71:	$observances[] = [
72:	'start' => $observance->property('DTSTART')->value ?? '19700101T000000',
73:	'offsetFrom' => $observance->property('TZOFFSETFROM')->value ?? '+0000',
74:	'offsetTo' => $observance->property('TZOFFSETTO')->value ?? '+0000',
75:	'rrule' => $observance->property('RRULE')?->value,
76:	'rdates' => $rdates,
77:	];
78:	}
79:	return $observances;
80:	}
81:	}
82:

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