1 files changed, 264 insertions, 0 deletions
diff --git a/apps/dav/lib/CalDAV/WebcalCaching/RefreshWebcalService.php b/apps/dav/lib/CalDAV/WebcalCaching/RefreshWebcalService.php
new file mode 100644
index 00000000000..a0981e6dec1
--- /dev/null
+++ b/apps/dav/lib/CalDAV/WebcalCaching/RefreshWebcalService.php
@@ -0,0 +1,264 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * SPDX-FileCopyrightText: 2020 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+namespace OCA\DAV\CalDAV\WebcalCaching;
+
+use OCA\DAV\CalDAV\CalDavBackend;
+use OCP\AppFramework\Utility\ITimeFactory;
+use Psr\Log\LoggerInterface;
+use Sabre\DAV\Exception\BadRequest;
+use Sabre\DAV\Exception\Forbidden;
+use Sabre\DAV\PropPatch;
+use Sabre\VObject\Component;
+use Sabre\VObject\DateTimeParser;
+use Sabre\VObject\InvalidDataException;
+use Sabre\VObject\ParseException;
+use Sabre\VObject\Reader;
+use Sabre\VObject\Recur\NoInstancesException;
+use Sabre\VObject\Splitter\ICalendar;
+use Sabre\VObject\UUIDUtil;
+use function count;
+
+class RefreshWebcalService {
+
+	public const REFRESH_RATE = '{http://apple.com/ns/ical/}refreshrate';
+	public const STRIP_ALARMS = '{http://calendarserver.org/ns/}subscribed-strip-alarms';
+	public const STRIP_ATTACHMENTS = '{http://calendarserver.org/ns/}subscribed-strip-attachments';
+	public const STRIP_TODOS = '{http://calendarserver.org/ns/}subscribed-strip-todos';
+
+	public function __construct(
+		private CalDavBackend $calDavBackend,
+		private LoggerInterface $logger,
+		private Connection $connection,
+		private ITimeFactory $time,
+	) {
+	}
+
+	public function refreshSubscription(string $principalUri, string $uri) {
+		$subscription = $this->getSubscription($principalUri, $uri);
+		$mutations = [];
+		if (!$subscription) {
+			return;
+		}
+
+		// Check the refresh rate if there is any
+		if (!empty($subscription['{http://apple.com/ns/ical/}refreshrate'])) {
+			// add the refresh interval to the lastmodified timestamp
+			$refreshInterval = new \DateInterval($subscription['{http://apple.com/ns/ical/}refreshrate']);
+			$updateTime = $this->time->getDateTime();
+			$updateTime->setTimestamp($subscription['lastmodified'])->add($refreshInterval);
+			if ($updateTime->getTimestamp() > $this->time->getTime()) {
+				return;
+			}
+		}
+
+
+		$webcalData = $this->connection->queryWebcalFeed($subscription);
+		if (!$webcalData) {
+			return;
+		}
+
+		$localData = $this->calDavBackend->getLimitedCalendarObjects((int)$subscription['id'], CalDavBackend::CALENDAR_TYPE_SUBSCRIPTION);
+
+		$stripTodos = ($subscription[self::STRIP_TODOS] ?? 1) === 1;
+		$stripAlarms = ($subscription[self::STRIP_ALARMS] ?? 1) === 1;
+		$stripAttachments = ($subscription[self::STRIP_ATTACHMENTS] ?? 1) === 1;
+
+		try {
+			$splitter = new ICalendar($webcalData, Reader::OPTION_FORGIVING);
+
+			while ($vObject = $splitter->getNext()) {
+				/** @var Component $vObject */
+				$compName = null;
+				$uid = null;
+
+				foreach ($vObject->getComponents() as $component) {
+					if ($component->name === 'VTIMEZONE') {
+						continue;
+					}
+
+					$compName = $component->name;
+
+					if ($stripAlarms) {
+						unset($component->{'VALARM'});
+					}
+					if ($stripAttachments) {
+						unset($component->{'ATTACH'});
+					}
+
+					$uid = $component->{ 'UID' }->getValue();
+				}
+
+				if ($stripTodos && $compName === 'VTODO') {
+					continue;
+				}
+
+				if (!isset($uid)) {
+					continue;
+				}
+
+				try {
+					$denormalized = $this->calDavBackend->getDenormalizedData($vObject->serialize());
+				} catch (InvalidDataException|Forbidden $ex) {
+					$this->logger->warning('Unable to denormalize calendar object from subscription {subscriptionId}', ['exception' => $ex, 'subscriptionId' => $subscription['id'], 'source' => $subscription['source']]);
+					continue;
+				}
+
+				// Find all identical sets and remove them from the update
+				if (isset($localData[$uid]) && $denormalized['etag'] === $localData[$uid]['etag']) {
+					unset($localData[$uid]);
+					continue;
+				}
+
+				$vObjectCopy = clone $vObject;
+				$identical = isset($localData[$uid]) && $this->compareWithoutDtstamp($vObjectCopy, $localData[$uid]);
+				if ($identical) {
+					unset($localData[$uid]);
+					continue;
+				}
+
+				// Find all modified sets and update them
+				if (isset($localData[$uid]) && $denormalized['etag'] !== $localData[$uid]['etag']) {
+					$this->calDavBackend->updateCalendarObject($subscription['id'], $localData[$uid]['uri'], $vObject->serialize(), CalDavBackend::CALENDAR_TYPE_SUBSCRIPTION);
+					unset($localData[$uid]);
+					continue;
+				}
+
+				// Only entirely new events get created here
+				try {
+					$objectUri = $this->getRandomCalendarObjectUri();
+					$this->calDavBackend->createCalendarObject($subscription['id'], $objectUri, $vObject->serialize(), CalDavBackend::CALENDAR_TYPE_SUBSCRIPTION);
+				} catch (NoInstancesException|BadRequest $ex) {
+					$this->logger->warning('Unable to create calendar object from subscription {subscriptionId}', ['exception' => $ex, 'subscriptionId' => $subscription['id'], 'source' => $subscription['source']]);
+				}
+			}
+
+			$ids = array_map(static function ($dataSet): int {
+				return (int)$dataSet['id'];
+			}, $localData);
+			$uris = array_map(static function ($dataSet): string {
+				return $dataSet['uri'];
+			}, $localData);
+
+			if (!empty($ids) && !empty($uris)) {
+				// Clean up on aisle 5
+				// The only events left over in the $localData array should be those that don't exist upstream
+				// All deleted VObjects from upstream are removed
+				$this->calDavBackend->purgeCachedEventsForSubscription($subscription['id'], $ids, $uris);
+			}
+
+			$newRefreshRate = $this->checkWebcalDataForRefreshRate($subscription, $webcalData);
+			if ($newRefreshRate) {
+				$mutations[self::REFRESH_RATE] = $newRefreshRate;
+			}
+
+			$this->updateSubscription($subscription, $mutations);
+		} catch (ParseException $ex) {
+			$this->logger->error('Subscription {subscriptionId} could not be refreshed due to a parsing error', ['exception' => $ex, 'subscriptionId' => $subscription['id']]);
+		}
+	}
+
+	/**
+	 * loads subscription from backend
+	 */
+	public function getSubscription(string $principalUri, string $uri): ?array {
+		$subscriptions = array_values(array_filter(
+			$this->calDavBackend->getSubscriptionsForUser($principalUri),
+			function ($sub) use ($uri) {
+				return $sub['uri'] === $uri;
+			}
+		));
+
+		if (count($subscriptions) === 0) {
+			return null;
+		}
+
+		return $subscriptions[0];
+	}
+
+
+	/**
+	 * check if:
+	 *  - current subscription stores a refreshrate
+	 *  - the webcal feed suggests a refreshrate
+	 *  - return suggested refreshrate if user didn't set a custom one
+	 *
+	 */
+	private function checkWebcalDataForRefreshRate(array $subscription, string $webcalData): ?string {
+		// if there is no refreshrate stored in the database, check the webcal feed
+		// whether it suggests any refresh rate and store that in the database
+		if (isset($subscription[self::REFRESH_RATE]) && $subscription[self::REFRESH_RATE] !== null) {
+			return null;
+		}
+
+		/** @var Component\VCalendar $vCalendar */
+		$vCalendar = Reader::read($webcalData);
+
+		$newRefreshRate = null;
+		if (isset($vCalendar->{'X-PUBLISHED-TTL'})) {
+			$newRefreshRate = $vCalendar->{'X-PUBLISHED-TTL'}->getValue();
+		}
+		if (isset($vCalendar->{'REFRESH-INTERVAL'})) {
+			$newRefreshRate = $vCalendar->{'REFRESH-INTERVAL'}->getValue();
+		}
+
+		if (!$newRefreshRate) {
+			return null;
+		}
+
+		// check if new refresh rate is even valid
+		try {
+			DateTimeParser::parseDuration($newRefreshRate);
+		} catch (InvalidDataException $ex) {
+			return null;
+		}
+
+		return $newRefreshRate;
+	}
+
+	/**
+	 * update subscription stored in database
+	 * used to set:
+	 *  - refreshrate
+	 *  - source
+	 *
+	 * @param array $subscription
+	 * @param array $mutations
+	 */
+	private function updateSubscription(array $subscription, array $mutations) {
+		if (empty($mutations)) {
+			return;
+		}
+
+		$propPatch = new PropPatch($mutations);
+		$this->calDavBackend->updateSubscription($subscription['id'], $propPatch);
+		$propPatch->commit();
+	}
+
+	/**
+	 * Returns a random uri for a calendar-object
+	 *
+	 * @return string
+	 */
+	public function getRandomCalendarObjectUri():string {
+		return UUIDUtil::getUUID() . '.ics';
+	}
+
+	private function compareWithoutDtstamp(Component $vObject, array $calendarObject): bool {
+		foreach ($vObject->getComponents() as $component) {
+			unset($component->{'DTSTAMP'});
+		}
+
+		$localVobject = Reader::read($calendarObject['calendardata']);
+		foreach ($localVobject->getComponents() as $component) {
+			unset($component->{'DTSTAMP'});
+		}
+
+		return strcasecmp($localVobject->serialize(), $vObject->serialize()) === 0;
+	}
+}