Merge pull request #33494 from nextcloud/enh/references

Backend for reference metadata fetching

15 files changed, 1042 insertions, 0 deletions

diff --git a/lib/base.php b/lib/base.php
index 1fca124f072..055cc6786f0 100644
--- a/lib/base.php
+++ b/lib/base.php
@@ -750,6 +750,7 @@ class OC {
 		self::registerEncryptionWrapperAndHooks();
 		self::registerAccountHooks();
 		self::registerResourceCollectionHooks();
+		self::registerFileReferenceEventListener();
 		self::registerAppRestrictionsHooks();
 
 		// Make sure that the application class is not loaded before the database is setup
@@ -912,6 +913,10 @@ class OC {
 		\OC\Collaboration\Resources\Listener::register(Server::get(SymfonyAdapter::class), Server::get(IEventDispatcher::class));
 	}
 
+	private static function registerFileReferenceEventListener() {
+		\OC\Collaboration\Reference\File\FileReferenceEventListener::register(Server::get(IEventDispatcher::class));
+	}
+
 	/**
 	 * register hooks for the filesystem
 	 */
diff --git a/lib/composer/composer/autoload_classmap.php b/lib/composer/composer/autoload_classmap.php
index 5b8e057636c..8c485fe53d9 100644
--- a/lib/composer/composer/autoload_classmap.php
+++ b/lib/composer/composer/autoload_classmap.php
@@ -142,6 +142,9 @@ return array(
     'OCP\\Collaboration\\Collaborators\\ISearchPlugin' => $baseDir . '/lib/public/Collaboration/Collaborators/ISearchPlugin.php',
     'OCP\\Collaboration\\Collaborators\\ISearchResult' => $baseDir . '/lib/public/Collaboration/Collaborators/ISearchResult.php',
     'OCP\\Collaboration\\Collaborators\\SearchResultType' => $baseDir . '/lib/public/Collaboration/Collaborators/SearchResultType.php',
+    'OCP\\Collaboration\\Reference\\IReference' => $baseDir . '/lib/public/Collaboration/Reference/IReference.php',
+    'OCP\\Collaboration\\Reference\\IReferenceManager' => $baseDir . '/lib/public/Collaboration/Reference/IReferenceManager.php',
+    'OCP\\Collaboration\\Reference\\IReferenceProvider' => $baseDir . '/lib/public/Collaboration/Reference/IReferenceProvider.php',
     'OCP\\Collaboration\\Resources\\CollectionException' => $baseDir . '/lib/public/Collaboration/Resources/CollectionException.php',
     'OCP\\Collaboration\\Resources\\ICollection' => $baseDir . '/lib/public/Collaboration/Resources/ICollection.php',
     'OCP\\Collaboration\\Resources\\IManager' => $baseDir . '/lib/public/Collaboration/Resources/IManager.php',
@@ -823,6 +826,11 @@ return array(
     'OC\\Collaboration\\Collaborators\\Search' => $baseDir . '/lib/private/Collaboration/Collaborators/Search.php',
     'OC\\Collaboration\\Collaborators\\SearchResult' => $baseDir . '/lib/private/Collaboration/Collaborators/SearchResult.php',
     'OC\\Collaboration\\Collaborators\\UserPlugin' => $baseDir . '/lib/private/Collaboration/Collaborators/UserPlugin.php',
+    'OC\\Collaboration\\Reference\\File\\FileReferenceEventListener' => $baseDir . '/lib/private/Collaboration/Reference/File/FileReferenceEventListener.php',
+    'OC\\Collaboration\\Reference\\File\\FileReferenceProvider' => $baseDir . '/lib/private/Collaboration/Reference/File/FileReferenceProvider.php',
+    'OC\\Collaboration\\Reference\\LinkReferenceProvider' => $baseDir . '/lib/private/Collaboration/Reference/LinkReferenceProvider.php',
+    'OC\\Collaboration\\Reference\\Reference' => $baseDir . '/lib/private/Collaboration/Reference/Reference.php',
+    'OC\\Collaboration\\Reference\\ReferenceManager' => $baseDir . '/lib/private/Collaboration/Reference/ReferenceManager.php',
     'OC\\Collaboration\\Resources\\Collection' => $baseDir . '/lib/private/Collaboration/Resources/Collection.php',
     'OC\\Collaboration\\Resources\\Listener' => $baseDir . '/lib/private/Collaboration/Resources/Listener.php',
     'OC\\Collaboration\\Resources\\Manager' => $baseDir . '/lib/private/Collaboration/Resources/Manager.php',
@@ -975,6 +983,8 @@ return array(
     'OC\\Core\\Controller\\ProfileApiController' => $baseDir . '/core/Controller/ProfileApiController.php',
     'OC\\Core\\Controller\\ProfilePageController' => $baseDir . '/core/Controller/ProfilePageController.php',
     'OC\\Core\\Controller\\RecommendedAppsController' => $baseDir . '/core/Controller/RecommendedAppsController.php',
+    'OC\\Core\\Controller\\ReferenceApiController' => $baseDir . '/core/Controller/ReferenceApiController.php',
+    'OC\\Core\\Controller\\ReferenceController' => $baseDir . '/core/Controller/ReferenceController.php',
     'OC\\Core\\Controller\\SearchController' => $baseDir . '/core/Controller/SearchController.php',
     'OC\\Core\\Controller\\SetupController' => $baseDir . '/core/Controller/SetupController.php',
     'OC\\Core\\Controller\\TwoFactorChallengeController' => $baseDir . '/core/Controller/TwoFactorChallengeController.php',
diff --git a/lib/composer/composer/autoload_static.php b/lib/composer/composer/autoload_static.php
index dd3031d3a9b..0dd18e5ddbf 100644
--- a/lib/composer/composer/autoload_static.php
+++ b/lib/composer/composer/autoload_static.php
@@ -175,6 +175,9 @@ class ComposerStaticInit749170dad3f5e7f9ca158f5a9f04f6a2
         'OCP\\Collaboration\\Collaborators\\ISearchPlugin' => __DIR__ . '/../../..' . '/lib/public/Collaboration/Collaborators/ISearchPlugin.php',
         'OCP\\Collaboration\\Collaborators\\ISearchResult' => __DIR__ . '/../../..' . '/lib/public/Collaboration/Collaborators/ISearchResult.php',
         'OCP\\Collaboration\\Collaborators\\SearchResultType' => __DIR__ . '/../../..' . '/lib/public/Collaboration/Collaborators/SearchResultType.php',
+        'OCP\\Collaboration\\Reference\\IReference' => __DIR__ . '/../../..' . '/lib/public/Collaboration/Reference/IReference.php',
+        'OCP\\Collaboration\\Reference\\IReferenceManager' => __DIR__ . '/../../..' . '/lib/public/Collaboration/Reference/IReferenceManager.php',
+        'OCP\\Collaboration\\Reference\\IReferenceProvider' => __DIR__ . '/../../..' . '/lib/public/Collaboration/Reference/IReferenceProvider.php',
         'OCP\\Collaboration\\Resources\\CollectionException' => __DIR__ . '/../../..' . '/lib/public/Collaboration/Resources/CollectionException.php',
         'OCP\\Collaboration\\Resources\\ICollection' => __DIR__ . '/../../..' . '/lib/public/Collaboration/Resources/ICollection.php',
         'OCP\\Collaboration\\Resources\\IManager' => __DIR__ . '/../../..' . '/lib/public/Collaboration/Resources/IManager.php',
@@ -856,6 +859,11 @@ class ComposerStaticInit749170dad3f5e7f9ca158f5a9f04f6a2
         'OC\\Collaboration\\Collaborators\\Search' => __DIR__ . '/../../..' . '/lib/private/Collaboration/Collaborators/Search.php',
         'OC\\Collaboration\\Collaborators\\SearchResult' => __DIR__ . '/../../..' . '/lib/private/Collaboration/Collaborators/SearchResult.php',
         'OC\\Collaboration\\Collaborators\\UserPlugin' => __DIR__ . '/../../..' . '/lib/private/Collaboration/Collaborators/UserPlugin.php',
+        'OC\\Collaboration\\Reference\\File\\FileReferenceEventListener' => __DIR__ . '/../../..' . '/lib/private/Collaboration/Reference/File/FileReferenceEventListener.php',
+        'OC\\Collaboration\\Reference\\File\\FileReferenceProvider' => __DIR__ . '/../../..' . '/lib/private/Collaboration/Reference/File/FileReferenceProvider.php',
+        'OC\\Collaboration\\Reference\\LinkReferenceProvider' => __DIR__ . '/../../..' . '/lib/private/Collaboration/Reference/LinkReferenceProvider.php',
+        'OC\\Collaboration\\Reference\\Reference' => __DIR__ . '/../../..' . '/lib/private/Collaboration/Reference/Reference.php',
+        'OC\\Collaboration\\Reference\\ReferenceManager' => __DIR__ . '/../../..' . '/lib/private/Collaboration/Reference/ReferenceManager.php',
         'OC\\Collaboration\\Resources\\Collection' => __DIR__ . '/../../..' . '/lib/private/Collaboration/Resources/Collection.php',
         'OC\\Collaboration\\Resources\\Listener' => __DIR__ . '/../../..' . '/lib/private/Collaboration/Resources/Listener.php',
         'OC\\Collaboration\\Resources\\Manager' => __DIR__ . '/../../..' . '/lib/private/Collaboration/Resources/Manager.php',
@@ -1008,6 +1016,8 @@ class ComposerStaticInit749170dad3f5e7f9ca158f5a9f04f6a2
         'OC\\Core\\Controller\\ProfileApiController' => __DIR__ . '/../../..' . '/core/Controller/ProfileApiController.php',
         'OC\\Core\\Controller\\ProfilePageController' => __DIR__ . '/../../..' . '/core/Controller/ProfilePageController.php',
         'OC\\Core\\Controller\\RecommendedAppsController' => __DIR__ . '/../../..' . '/core/Controller/RecommendedAppsController.php',
+        'OC\\Core\\Controller\\ReferenceApiController' => __DIR__ . '/../../..' . '/core/Controller/ReferenceApiController.php',
+        'OC\\Core\\Controller\\ReferenceController' => __DIR__ . '/../../..' . '/core/Controller/ReferenceController.php',
         'OC\\Core\\Controller\\SearchController' => __DIR__ . '/../../..' . '/core/Controller/SearchController.php',
         'OC\\Core\\Controller\\SetupController' => __DIR__ . '/../../..' . '/core/Controller/SetupController.php',
         'OC\\Core\\Controller\\TwoFactorChallengeController' => __DIR__ . '/../../..' . '/core/Controller/TwoFactorChallengeController.php',
diff --git a/lib/private/AppFramework/Bootstrap/RegistrationContext.php b/lib/private/AppFramework/Bootstrap/RegistrationContext.php
index c98f968c999..3ade98e334f 100644
--- a/lib/private/AppFramework/Bootstrap/RegistrationContext.php
+++ b/lib/private/AppFramework/Bootstrap/RegistrationContext.php
@@ -32,6 +32,7 @@ namespace OC\AppFramework\Bootstrap;
 use Closure;
 use OCP\Calendar\Resource\IBackend as IResourceBackend;
 use OCP\Calendar\Room\IBackend as IRoomBackend;
+use OCP\Collaboration\Reference\IReferenceProvider;
 use OCP\Talk\ITalkBackend;
 use RuntimeException;
 use function array_shift;
@@ -121,6 +122,9 @@ class RegistrationContext {
 	/** @var ServiceRegistration<ICalendarProvider>[] */
 	private $calendarProviders = [];
 
+	/** @var ServiceRegistration<IReferenceProvider>[] */
+	private array $referenceProviders = [];
+
 	/** @var ParameterRegistration[] */
 	private $sensitiveMethods = [];
 
@@ -273,6 +277,13 @@ class RegistrationContext {
 				);
 			}
 
+			public function registerReferenceProvider(string $class): void {
+				$this->context->registerReferenceProvider(
+					$this->appId,
+					$class
+				);
+			}
+
 			public function registerProfileLinkAction(string $actionClass): void {
 				$this->context->registerProfileLinkAction(
 					$this->appId,
@@ -398,6 +409,10 @@ class RegistrationContext {
 		$this->calendarProviders[] = new ServiceRegistration($appId, $class);
 	}
 
+	public function registerReferenceProvider(string $appId, string $class): void {
+		$this->referenceProviders[] = new ServiceRegistration($appId, $class);
+	}
+
 	/**
 	 * @psalm-param class-string<ILinkAction> $actionClass
 	 */
@@ -692,6 +707,13 @@ class RegistrationContext {
 	}
 
 	/**
+	 * @return ServiceRegistration<IReferenceProvider>[]
+	 */
+	public function getReferenceProviders(): array {
+		return $this->referenceProviders;
+	}
+
+	/**
 	 * @return ServiceRegistration<ILinkAction>[]
 	 */
 	public function getProfileLinkActions(): array {
diff --git a/lib/private/Collaboration/Reference/File/FileReferenceEventListener.php b/lib/private/Collaboration/Reference/File/FileReferenceEventListener.php
new file mode 100644
index 00000000000..6ccae9903dc
--- /dev/null
+++ b/lib/private/Collaboration/Reference/File/FileReferenceEventListener.php
@@ -0,0 +1,61 @@
+<?php
+
+declare(strict_types=1);
+/**
+ * @copyright Copyright (c) 2022 Julius Härtl <jus@bitgrid.net>
+ *
+ * @author Julius Härtl <jus@bitgrid.net>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+namespace OC\Collaboration\Reference\File;
+
+use OCP\Collaboration\Reference\IReferenceManager;
+use OCP\EventDispatcher\Event;
+use OCP\EventDispatcher\IEventDispatcher;
+use OCP\Files\Events\Node\NodeDeletedEvent;
+use OCP\Share\Events\ShareCreatedEvent;
+use OCP\Share\Events\ShareDeletedEvent;
+
+class FileReferenceEventListener implements \OCP\EventDispatcher\IEventListener {
+	private IReferenceManager $manager;
+
+	public function __construct(IReferenceManager $manager) {
+		$this->manager = $manager;
+	}
+
+	public static function register(IEventDispatcher $eventDispatcher): void {
+		$eventDispatcher->addServiceListener(NodeDeletedEvent::class, FileReferenceEventListener::class);
+		$eventDispatcher->addServiceListener(ShareDeletedEvent::class, FileReferenceEventListener::class);
+		$eventDispatcher->addServiceListener(ShareCreatedEvent::class, FileReferenceEventListener::class);
+	}
+
+	/**
+	 * @inheritDoc
+	 */
+	public function handle(Event $event): void {
+		if ($event instanceof NodeDeletedEvent) {
+			$this->manager->invalidateCache((string)$event->getNode()->getId());
+		}
+		if ($event instanceof ShareDeletedEvent) {
+			$this->manager->invalidateCache((string)$event->getShare()->getNodeId());
+		}
+		if ($event instanceof ShareCreatedEvent) {
+			$this->manager->invalidateCache((string)$event->getShare()->getNodeId());
+		}
+	}
+}
diff --git a/lib/private/Collaboration/Reference/File/FileReferenceProvider.php b/lib/private/Collaboration/Reference/File/FileReferenceProvider.php
new file mode 100644
index 00000000000..39cdb62b09a
--- /dev/null
+++ b/lib/private/Collaboration/Reference/File/FileReferenceProvider.php
@@ -0,0 +1,153 @@
+<?php
+
+declare(strict_types=1);
+/**
+ * @copyright Copyright (c) 2022 Julius Härtl <jus@bitgrid.net>
+ *
+ * @author Julius Härtl <jus@bitgrid.net>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+namespace OC\Collaboration\Reference\File;
+
+use OC\Collaboration\Reference\Reference;
+use OC\User\NoUserException;
+use OCP\Collaboration\Reference\IReference;
+use OCP\Collaboration\Reference\IReferenceProvider;
+use OCP\Files\InvalidPathException;
+use OCP\Files\IRootFolder;
+use OCP\Files\Node;
+use OCP\Files\NotFoundException;
+use OCP\Files\NotPermittedException;
+use OCP\IPreview;
+use OCP\IURLGenerator;
+use OCP\IUserSession;
+
+class FileReferenceProvider implements IReferenceProvider {
+	private IURLGenerator $urlGenerator;
+	private IRootFolder $rootFolder;
+	private ?string $userId;
+	private IPreview $previewManager;
+
+	public function __construct(IURLGenerator $urlGenerator, IRootFolder $rootFolder, IUserSession $userSession, IPreview $previewManager) {
+		$this->urlGenerator = $urlGenerator;
+		$this->rootFolder = $rootFolder;
+		$this->userId = $userSession->getUser() ? $userSession->getUser()->getUID() : null;
+		$this->previewManager = $previewManager;
+	}
+
+	public function matchReference(string $referenceText): bool {
+		return $this->getFilesAppLinkId($referenceText) !== null;
+	}
+
+	private function getFilesAppLinkId(string $referenceText): ?int {
+		$start = $this->urlGenerator->getAbsoluteURL('/apps/files');
+		$startIndex = $this->urlGenerator->getAbsoluteURL('/index.php/apps/files');
+
+		$fileId = null;
+
+		if (mb_strpos($referenceText, $start) === 0) {
+			$parts = parse_url($referenceText);
+			parse_str($parts['query'], $query);
+			$fileId = isset($query['fileid']) ? (int)$query['fileid'] : $fileId;
+			$fileId = isset($query['openfile']) ? (int)$query['openfile'] : $fileId;
+		}
+
+		if (mb_strpos($referenceText, $startIndex) === 0) {
+			$parts = parse_url($referenceText);
+			parse_str($parts['query'], $query);
+			$fileId = isset($query['fileid']) ? (int)$query['fileid'] : $fileId;
+			$fileId = isset($query['openfile']) ? (int)$query['openfile'] : $fileId;
+		}
+
+		if (mb_strpos($referenceText, $this->urlGenerator->getAbsoluteURL('/index.php/f/')) === 0) {
+			$fileId = str_replace($this->urlGenerator->getAbsoluteURL('/index.php/f/'), '', $referenceText);
+		}
+
+		if (mb_strpos($referenceText, $this->urlGenerator->getAbsoluteURL('/f/')) === 0) {
+			$fileId = str_replace($this->urlGenerator->getAbsoluteURL('/f/'), '', $referenceText);
+		}
+
+		return $fileId !== null ? (int)$fileId : null;
+	}
+
+	public function resolveReference(string $referenceText): ?IReference {
+		if ($this->matchReference($referenceText)) {
+			$reference = new Reference($referenceText);
+			try {
+				$this->fetchReference($reference);
+			} catch (NotFoundException $e) {
+				$reference->setRichObject('file', null);
+				$reference->setAccessible(false);
+			}
+			return $reference;
+		}
+
+		return null;
+	}
+
+	/**
+	 * @throws NotFoundException
+	 */
+	private function fetchReference(Reference $reference): void {
+		if ($this->userId === null) {
+			throw new NotFoundException();
+		}
+
+		$fileId = $this->getFilesAppLinkId($reference->getId());
+		if ($fileId === null) {
+			throw new NotFoundException();
+		}
+
+		try {
+			$userFolder = $this->rootFolder->getUserFolder($this->userId);
+			$files = $userFolder->getById($fileId);
+
+			if (empty($files)) {
+				throw new NotFoundException();
+			}
+
+			/** @var Node $file */
+			$file = array_shift($files);
+
+			$reference->setTitle($file->getName());
+			$reference->setDescription($file->getMimetype());
+			$reference->setUrl($this->urlGenerator->getAbsoluteURL('/index.php/f/' . $fileId));
+			$reference->setImageUrl($this->urlGenerator->linkToRouteAbsolute('core.Preview.getPreviewByFileId', ['x' => 1600, 'y' => 630, 'fileId' => $fileId]));
+
+			$reference->setRichObject('file', [
+				'id' => $file->getId(),
+				'name' => $file->getName(),
+				'size' => $file->getSize(),
+				'path' => $file->getPath(),
+				'link' => $reference->getUrl(),
+				'mimetype' => $file->getMimetype(),
+				'preview-available' => $this->previewManager->isAvailable($file)
+			]);
+		} catch (InvalidPathException|NotFoundException|NotPermittedException|NoUserException $e) {
+			throw new NotFoundException();
+		}
+	}
+
+	public function getCachePrefix(string $referenceId): string {
+		return (string)$this->getFilesAppLinkId($referenceId);
+	}
+
+	public function getCacheKey(string $referenceId): ?string {
+		return $this->userId ?? '';
+	}
+}
diff --git a/lib/private/Collaboration/Reference/LinkReferenceProvider.php b/lib/private/Collaboration/Reference/LinkReferenceProvider.php
new file mode 100644
index 00000000000..36fbdd0b168
--- /dev/null
+++ b/lib/private/Collaboration/Reference/LinkReferenceProvider.php
@@ -0,0 +1,162 @@
+<?php
+
+declare(strict_types=1);
+/**
+ * @copyright Copyright (c) 2022 Julius Härtl <jus@bitgrid.net>
+ *
+ * @author Julius Härtl <jus@bitgrid.net>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+namespace OC\Collaboration\Reference;
+
+use Fusonic\OpenGraph\Consumer;
+use GuzzleHttp\Psr7\LimitStream;
+use GuzzleHttp\Psr7\Utils;
+use OC\Security\RateLimiting\Exception\RateLimitExceededException;
+use OC\Security\RateLimiting\Limiter;
+use OC\SystemConfig;
+use OCP\Collaboration\Reference\IReference;
+use OCP\Collaboration\Reference\IReferenceProvider;
+use OCP\Files\AppData\IAppDataFactory;
+use OCP\Files\NotFoundException;
+use OCP\Http\Client\IClientService;
+use OCP\IRequest;
+use OCP\IURLGenerator;
+use OCP\IUserSession;
+use Psr\Log\LoggerInterface;
+
+class LinkReferenceProvider implements IReferenceProvider {
+	public const MAX_PREVIEW_SIZE = 1024 * 1024;
+
+	public const ALLOWED_CONTENT_TYPES = [
+		'image/png',
+		'image/jpg',
+		'image/jpeg',
+		'image/gif',
+		'image/svg+xml',
+		'image/webp'
+	];
+
+	private IClientService $clientService;
+	private LoggerInterface $logger;
+	private SystemConfig $systemConfig;
+	private IAppDataFactory $appDataFactory;
+	private IURLGenerator $urlGenerator;
+	private Limiter $limiter;
+	private IUserSession $userSession;
+	private IRequest $request;
+
+	public function __construct(IClientService $clientService, LoggerInterface $logger, SystemConfig $systemConfig, IAppDataFactory $appDataFactory, IURLGenerator $urlGenerator, Limiter $limiter, IUserSession $userSession, IRequest $request) {
+		$this->clientService = $clientService;
+		$this->logger = $logger;
+		$this->systemConfig = $systemConfig;
+		$this->appDataFactory = $appDataFactory;
+		$this->urlGenerator = $urlGenerator;
+		$this->limiter = $limiter;
+		$this->userSession = $userSession;
+		$this->request = $request;
+	}
+
+	public function matchReference(string $referenceText): bool {
+		if ($this->systemConfig->getValue('reference_opengraph', true) !== true) {
+			return false;
+		}
+
+		return (bool)preg_match(IURLGenerator::URL_REGEX, $referenceText);
+	}
+
+	public function resolveReference(string $referenceText): ?IReference {
+		if ($this->matchReference($referenceText)) {
+			$reference = new Reference($referenceText);
+			$this->fetchReference($reference);
+			return $reference;
+		}
+
+		return null;
+	}
+
+	private function fetchReference(Reference $reference): void {
+		try {
+			$user = $this->userSession->getUser();
+			if ($user) {
+				$this->limiter->registerUserRequest('opengraph', 10, 120, $user);
+			} else {
+				$this->limiter->registerAnonRequest('opengraph', 10, 120, $this->request->getRemoteAddress());
+			}
+		} catch (RateLimitExceededException $e) {
+			return;
+		}
+
+		$client = $this->clientService->newClient();
+		try {
+			$response = $client->get($reference->getId(), [ 'timeout' => 10 ]);
+		} catch (\Exception $e) {
+			$this->logger->debug('Failed to fetch link for obtaining open graph data', ['exception' => $e]);
+			return;
+		}
+
+		$responseBody = (string)$response->getBody();
+
+		// OpenGraph handling
+		$consumer = new Consumer();
+		$consumer->useFallbackMode = true;
+		$object = $consumer->loadHtml($responseBody);
+
+		$reference->setUrl($reference->getId());
+
+		if ($object->title) {
+			$reference->setTitle($object->title);
+		}
+
+		if ($object->description) {
+			$reference->setDescription($object->description);
+		}
+
+		if ($object->images) {
+			try {
+				$appData = $this->appDataFactory->get('core');
+				try {
+					$folder = $appData->getFolder('opengraph');
+				} catch (NotFoundException $e) {
+					$folder = $appData->newFolder('opengraph');
+				}
+				$response = $client->get($object->images[0]->url, [ 'timeout' => 10 ]);
+				$contentType = $response->getHeader('Content-Type');
+				$contentLength = $response->getHeader('Content-Length');
+
+				if (in_array($contentType, self::ALLOWED_CONTENT_TYPES, true) && $contentLength < self::MAX_PREVIEW_SIZE) {
+					$stream = Utils::streamFor($response->getBody());
+					$bodyStream = new LimitStream($stream, self::MAX_PREVIEW_SIZE, 0);
+					$reference->setImageContentType($contentType);
+					$folder->newFile(md5($reference->getId()), $bodyStream->getContents());
+					$reference->setImageUrl($this->urlGenerator->linkToRouteAbsolute('core.Reference.preview', ['referenceId' => md5($reference->getId())]));
+				}
+			} catch (\Throwable $e) {
+				$this->logger->error('Failed to fetch and store the open graph image for ' . $reference->getId(), ['exception' => $e]);
+			}
+		}
+	}
+
+	public function getCachePrefix(string $referenceId): string {
+		return $referenceId;
+	}
+
+	public function getCacheKey(string $referenceId): ?string {
+		return null;
+	}
+}
diff --git a/lib/private/Collaboration/Reference/Reference.php b/lib/private/Collaboration/Reference/Reference.php
new file mode 100644
index 00000000000..22dc57782d8
--- /dev/null
+++ b/lib/private/Collaboration/Reference/Reference.php
@@ -0,0 +1,163 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * @copyright Copyright (c) 2022 Julius Härtl <jus@bitgrid.net>
+ *
+ * @author Julius Härtl <jus@bitgrid.net>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+namespace OC\Collaboration\Reference;
+
+use OCP\Collaboration\Reference\IReference;
+
+class Reference implements IReference {
+	private string $reference;
+
+	private bool $accessible = true;
+
+	private ?string $title = null;
+	private ?string $description = null;
+	private ?string $imageUrl = null;
+	private ?string $contentType = null;
+	private ?string $url = null;
+
+	private ?string $richObjectType = null;
+	private ?array $richObject = null;
+
+	public function __construct(string $reference) {
+		$this->reference = $reference;
+	}
+
+	public function getId(): string {
+		return $this->reference;
+	}
+
+	public function setAccessible(bool $accessible): void {
+		$this->accessible = $accessible;
+	}
+
+	public function getAccessible(): bool {
+		return $this->accessible;
+	}
+
+	public function setTitle(string $title): void {
+		$this->title = $title;
+	}
+
+	public function getTitle(): string {
+		return $this->title ?? $this->reference;
+	}
+
+	public function setDescription(?string $description): void {
+		$this->description = $description;
+	}
+
+	public function getDescription(): ?string {
+		return $this->description;
+	}
+
+	public function setImageUrl(?string $imageUrl): void {
+		$this->imageUrl = $imageUrl;
+	}
+
+	public function getImageUrl(): ?string {
+		return $this->imageUrl;
+	}
+
+	public function setImageContentType(?string $contentType): void {
+		$this->contentType = $contentType;
+	}
+
+	public function getImageContentType(): ?string {
+		return $this->contentType;
+	}
+
+	public function setUrl(?string $url): void {
+		$this->url = $url;
+	}
+
+	public function getUrl(): ?string {
+		return $this->url;
+	}
+
+	public function setRichObject(string $type, ?array $richObject): void {
+		$this->richObjectType = $type;
+		$this->richObject = $richObject;
+	}
+
+	public function getRichObjectType(): string {
+		if ($this->richObjectType === null) {
+			return 'open-graph';
+		}
+		return $this->richObjectType;
+	}
+
+	public function getRichObject(): array {
+		if ($this->richObject === null) {
+			return $this->getOpenGraphObject();
+		}
+		return $this->richObject;
+	}
+
+	public function getOpenGraphObject(): array {
+		return [
+			'id' => $this->getId(),
+			'name' => $this->getTitle(),
+			'description' => $this->getDescription(),
+			'thumb' => $this->getImageUrl(),
+			'link' => $this->getUrl()
+		];
+	}
+
+	public static function toCache(IReference $reference): array {
+		return [
+			'id' => $reference->getId(),
+			'title' => $reference->getTitle(),
+			'imageUrl' => $reference->getImageUrl(),
+			'imageContentType' => $reference->getImageContentType(),
+			'description' => $reference->getDescription(),
+			'link' => $reference->getUrl(),
+			'accessible' => $reference->getAccessible(),
+			'richObjectType' => $reference->getRichObjectType(),
+			'richObject' => $reference->getRichObject(),
+		];
+	}
+
+	public static function fromCache(array $cache): IReference {
+		$reference = new Reference($cache['id']);
+		$reference->setTitle($cache['title']);
+		$reference->setDescription($cache['description']);
+		$reference->setImageUrl($cache['imageUrl']);
+		$reference->setImageContentType($cache['imageContentType']);
+		$reference->setUrl($cache['link']);
+		$reference->setRichObject($cache['richObjectType'], $cache['richObject']);
+		$reference->setAccessible($cache['accessible']);
+		return $reference;
+	}
+
+	public function jsonSerialize() {
+		return [
+			'richObjectType' => $this->getRichObjectType(),
+			'richObject' => $this->getRichObject(),
+			'openGraphObject' => $this->getOpenGraphObject(),
+			'accessible' => $this->accessible
+		];
+	}
+}
diff --git a/lib/private/Collaboration/Reference/ReferenceManager.php b/lib/private/Collaboration/Reference/ReferenceManager.php
new file mode 100644
index 00000000000..304d693804f
--- /dev/null
+++ b/lib/private/Collaboration/Reference/ReferenceManager.php
@@ -0,0 +1,169 @@
+<?php
+
+declare(strict_types=1);
+/**
+ * @copyright Copyright (c) 2022 Julius Härtl <jus@bitgrid.net>
+ *
+ * @author Julius Härtl <jus@bitgrid.net>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+namespace OC\Collaboration\Reference;
+
+use OC\AppFramework\Bootstrap\Coordinator;
+use OC\Collaboration\Reference\File\FileReferenceProvider;
+use OCP\Collaboration\Reference\IReference;
+use OCP\Collaboration\Reference\IReferenceManager;
+use OCP\Collaboration\Reference\IReferenceProvider;
+use OCP\ICache;
+use OCP\ICacheFactory;
+use OCP\IURLGenerator;
+use Psr\Container\ContainerInterface;
+use Psr\Log\LoggerInterface;
+use Throwable;
+
+class ReferenceManager implements IReferenceManager {
+	public const CACHE_TTL = 3600;
+
+	/** @var IReferenceProvider[]|null */
+	private ?array $providers = null;
+	private ICache $cache;
+	private Coordinator $coordinator;
+	private ContainerInterface $container;
+	private LinkReferenceProvider $linkReferenceProvider;
+	private LoggerInterface $logger;
+
+	public function __construct(LinkReferenceProvider $linkReferenceProvider, ICacheFactory $cacheFactory, Coordinator $coordinator, ContainerInterface $container, LoggerInterface $logger) {
+		$this->linkReferenceProvider = $linkReferenceProvider;
+		$this->cache = $cacheFactory->createDistributed('reference');
+		$this->coordinator = $coordinator;
+		$this->container = $container;
+		$this->logger = $logger;
+	}
+
+	public function extractReferences(string $text): array {
+		preg_match_all(IURLGenerator::URL_REGEX, $text, $matches);
+		$references = $matches[0] ?? [];
+		return array_map(function ($reference) {
+			return trim($reference);
+		}, $references);
+	}
+
+	public function getReferenceFromCache(string $referenceId): ?IReference {
+		$matchedProvider = $this->getMatchedProvider($referenceId);
+
+		if ($matchedProvider === null) {
+			return null;
+		}
+
+		$cacheKey = $this->getFullCacheKey($matchedProvider, $referenceId);
+		return $this->getReferenceByCacheKey($cacheKey);
+	}
+
+	public function getReferenceByCacheKey(string $cacheKey): ?IReference {
+		$cached = $this->cache->get($cacheKey);
+		if ($cached) {
+			return Reference::fromCache($cached);
+		}
+
+		return null;
+	}
+
+	public function resolveReference(string $referenceId): ?IReference {
+		$matchedProvider = $this->getMatchedProvider($referenceId);
+
+		if ($matchedProvider === null) {
+			return null;
+		}
+
+		$cacheKey = $this->getFullCacheKey($matchedProvider, $referenceId);
+		$cached = $this->cache->get($cacheKey);
+		if ($cached) {
+			return Reference::fromCache($cached);
+		}
+
+		$reference = $matchedProvider->resolveReference($referenceId);
+		if ($reference) {
+			$this->cache->set($cacheKey, Reference::toCache($reference), self::CACHE_TTL);
+			return $reference;
+		}
+
+		return null;
+	}
+
+	private function getMatchedProvider(string $referenceId): ?IReferenceProvider {
+		$matchedProvider = null;
+		foreach ($this->getProviders() as $provider) {
+			$matchedProvider = $provider->matchReference($referenceId) ? $provider : null;
+			if ($matchedProvider !== null) {
+				break;
+			}
+		}
+
+		if ($matchedProvider === null && $this->linkReferenceProvider->matchReference($referenceId)) {
+			$matchedProvider = $this->linkReferenceProvider;
+		}
+
+		return $matchedProvider;
+	}
+
+	private function getFullCacheKey(IReferenceProvider $provider, string $referenceId): string {
+		$cacheKey = $provider->getCacheKey($referenceId);
+		return md5($provider->getCachePrefix($referenceId)) . (
+			$cacheKey !== null ? ('-' . md5($cacheKey)) : ''
+		);
+	}
+
+	public function invalidateCache(string $cachePrefix, ?string $cacheKey = null): void {
+		if ($cacheKey === null) {
+			$this->cache->clear(md5($cachePrefix));
+			return;
+		}
+
+		$this->cache->remove(md5($cachePrefix) . '-' . md5($cacheKey));
+	}
+
+	/**
+	 * @return IReferenceProvider[]
+	 */
+	public function getProviders(): array {
+		if ($this->providers === null) {
+			$context = $this->coordinator->getRegistrationContext();
+			if ($context === null) {
+				return [];
+			}
+
+			$this->providers = array_filter(array_map(function ($registration): ?IReferenceProvider {
+				try {
+					/** @var IReferenceProvider $provider */
+					$provider = $this->container->get($registration->getService());
+				} catch (Throwable $e) {
+					$this->logger->error('Could not load reference provider ' . $registration->getService() . ': ' . $e->getMessage(), [
+						'exception' => $e,
+					]);
+					return null;
+				}
+
+				return $provider;
+			}, $context->getReferenceProviders()));
+
+			$this->providers[] = $this->container->get(FileReferenceProvider::class);
+		}
+
+		return $this->providers;
+	}
+}
diff --git a/lib/private/Server.php b/lib/private/Server.php
index 09074e39046..f18ac7b6534 100644
--- a/lib/private/Server.php
+++ b/lib/private/Server.php
@@ -73,6 +73,7 @@ use OC\Collaboration\Collaborators\MailPlugin;
 use OC\Collaboration\Collaborators\RemoteGroupPlugin;
 use OC\Collaboration\Collaborators\RemotePlugin;
 use OC\Collaboration\Collaborators\UserPlugin;
+use OC\Collaboration\Reference\ReferenceManager;
 use OC\Command\CronBus;
 use OC\Comments\ManagerFactory as CommentsManagerFactory;
 use OC\Contacts\ContactsMenu\ActionFactory;
@@ -162,6 +163,7 @@ use OCP\App\IAppManager;
 use OCP\Authentication\LoginCredentials\IStore;
 use OCP\BackgroundJob\IJobList;
 use OCP\Collaboration\AutoComplete\IManager;
+use OCP\Collaboration\Reference\IReferenceManager;
 use OCP\Command\IBus;
 use OCP\Comments\ICommentsManager;
 use OCP\Contacts\ContactsMenu\IActionFactory;
@@ -1338,6 +1340,8 @@ class Server extends ServerContainer implements IServerContainer {
 		$this->registerAlias(\OCP\Collaboration\Resources\IProviderManager::class, \OC\Collaboration\Resources\ProviderManager::class);
 		$this->registerAlias(\OCP\Collaboration\Resources\IManager::class, \OC\Collaboration\Resources\Manager::class);
 
+		$this->registerAlias(IReferenceManager::class, ReferenceManager::class);
+
 		$this->registerDeprecatedAlias('SettingsManager', \OC\Settings\Manager::class);
 		$this->registerAlias(\OCP\Settings\IManager::class, \OC\Settings\Manager::class);
 		$this->registerService(\OC\Files\AppData\Factory::class, function (ContainerInterface $c) {
diff --git a/lib/public/AppFramework/Bootstrap/IRegistrationContext.php b/lib/public/AppFramework/Bootstrap/IRegistrationContext.php
index 6b10d7bfc0f..0f398c13979 100644
--- a/lib/public/AppFramework/Bootstrap/IRegistrationContext.php
+++ b/lib/public/AppFramework/Bootstrap/IRegistrationContext.php
@@ -33,6 +33,7 @@ use OCP\AppFramework\IAppContainer;
 use OCP\Authentication\TwoFactorAuth\IProvider;
 use OCP\Calendar\ICalendarProvider;
 use OCP\Capabilities\ICapability;
+use OCP\Collaboration\Reference\IReferenceProvider;
 use OCP\EventDispatcher\IEventDispatcher;
 use OCP\Files\Template\ICustomTemplateProvider;
 use OCP\IContainer;
@@ -255,6 +256,15 @@ interface IRegistrationContext {
 	public function registerCalendarProvider(string $class): void;
 
 	/**
+	 * Register a reference provider
+	 *
+	 * @param string $class
+	 * @psalm-param class-string<IReferenceProvider> $class
+	 * @since 25.0.0
+	 */
+	public function registerReferenceProvider(string $class): void;
+
+	/**
 	 * Register an implementation of \OCP\Profile\ILinkAction that
 	 * will handle the implementation of a profile link action
 	 *
diff --git a/lib/public/Collaboration/Reference/IReference.php b/lib/public/Collaboration/Reference/IReference.php
new file mode 100644
index 00000000000..0155ae86dd8
--- /dev/null
+++ b/lib/public/Collaboration/Reference/IReference.php
@@ -0,0 +1,130 @@
+<?php
+
+declare(strict_types=1);
+/**
+ * @copyright Copyright (c) 2022 Julius Härtl <jus@bitgrid.net>
+ *
+ * @author Julius Härtl <jus@bitgrid.net>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+namespace OCP\Collaboration\Reference;
+
+use JsonSerializable;
+
+/**
+ * @since 25.0.0
+ */
+interface IReference extends JsonSerializable {
+
+	/**
+	 * @since 25.0.0
+	 */
+	public function getId(): string;
+
+	/**
+	 * Accessible flag indicates if the user has access to the provided reference
+	 *
+	 * @since 25.0.0
+	 */
+	public function setAccessible(bool $accessible): void;
+
+	/**
+	 * Accessible flag indicates if the user has access to the provided reference
+	 *
+	 * @since 25.0.0
+	 */
+	public function getAccessible(): bool;
+
+	/**
+	 * @since 25.0.0
+	 */
+	public function setTitle(string $title): void;
+
+	/**
+	 * @since 25.0.0
+	 */
+	public function getTitle(): string;
+
+	/**
+	 * @since 25.0.0
+	 */
+	public function setDescription(?string $description): void;
+
+	/**
+	 * @since 25.0.0
+	 */
+	public function getDescription(): ?string;
+
+	/**
+	 * @since 25.0.0
+	 */
+	public function setImageUrl(?string $imageUrl): void;
+
+	/**
+	 * @since 25.0.0
+	 */
+	public function getImageUrl(): ?string;
+
+	/**
+	 * @since 25.0.0
+	 */
+	public function setImageContentType(?string $contentType): void;
+
+	/**
+	 * @since 25.0.0
+	 */
+	public function getImageContentType(): ?string;
+
+	/**
+	 * @since 25.0.0
+	 */
+	public function setUrl(?string $url): void;
+
+	/**
+	 * @since 25.0.0
+	 */
+	public function getUrl(): ?string;
+
+	/**
+	 * Set the reference specific rich object representation
+	 *
+	 * @since 25.0.0
+	 */
+	public function setRichObject(string $type, ?array $richObject): void;
+
+	/**
+	 * Returns the type of the reference specific rich object
+	 *
+	 * @since 25.0.0
+	 */
+	public function getRichObjectType(): string;
+
+	/**
+	 * Returns the reference specific rich object representation
+	 *
+	 * @since 25.0.0
+	 */
+	public function getRichObject(): array;
+
+	/**
+	 * Returns the opengraph rich object representation
+	 *
+	 * @since 25.0.0
+	 */
+	public function getOpenGraphObject(): array;
+}
diff --git a/lib/public/Collaboration/Reference/IReferenceManager.php b/lib/public/Collaboration/Reference/IReferenceManager.php
new file mode 100644
index 00000000000..487e243c7ed
--- /dev/null
+++ b/lib/public/Collaboration/Reference/IReferenceManager.php
@@ -0,0 +1,70 @@
+<?php
+
+declare(strict_types=1);
+/**
+ * @copyright Copyright (c) 2022 Julius Härtl <jus@bitgrid.net>
+ *
+ * @author Julius Härtl <jus@bitgrid.net>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+namespace OCP\Collaboration\Reference;
+
+/**
+ * @since 25.0.0
+ */
+interface IReferenceManager {
+	/**
+	 * Return all reference identifiers within a string as an array
+	 *
+	 * @return string[] Array of found references (urls)
+	 * @since 25.0.0
+	 */
+	public function extractReferences(string $text): array;
+
+	/**
+	 * Resolve a given reference id to its metadata with all available providers
+	 *
+	 * This method has a fallback to always provide the open graph metadata,
+	 * but may still return null in case this is disabled or the fetching fails
+	 *
+	 * @since 25.0.0
+	 */
+	public function resolveReference(string $referenceId): ?IReference;
+
+	/**
+	 * Get a reference by its cache key
+	 *
+	 * @since 25.0.0
+	 */
+	public function getReferenceByCacheKey(string $cacheKey): ?IReference;
+
+	/**
+	 * Explicitly get a reference from the cache to avoid heavy fetches for cases
+	 * the cache can then be filled with a separate request from the frontend
+	 *
+	 * @since 25.0.0
+	 */
+	public function getReferenceFromCache(string $referenceId): ?IReference;
+
+	/**
+	 * Invalidate all cache entries with a prefix or just one if the cache key is provided
+	 *
+	 * @since 25.0.0
+	 */
+	public function invalidateCache(string $cachePrefix, ?string $cacheKey = null): void;
+}
diff --git a/lib/public/Collaboration/Reference/IReferenceProvider.php b/lib/public/Collaboration/Reference/IReferenceProvider.php
new file mode 100644
index 00000000000..100374b78b3
--- /dev/null
+++ b/lib/public/Collaboration/Reference/IReferenceProvider.php
@@ -0,0 +1,63 @@
+<?php
+
+declare(strict_types=1);
+/**
+ * @copyright Copyright (c) 2022 Julius Härtl <jus@bitgrid.net>
+ *
+ * @author Julius Härtl <jus@bitgrid.net>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+namespace OCP\Collaboration\Reference;
+
+/**
+ * @since 25.0.0
+ */
+interface IReferenceProvider {
+	/**
+	 * Validate that a given reference identifier matches the current provider
+	 *
+	 * @since 25.0.0
+	 */
+	public function matchReference(string $referenceText): bool;
+
+	/**
+	 * Return a reference with its metadata for a given reference identifier
+	 *
+	 * @since 25.0.0
+	 */
+	public function resolveReference(string $referenceText): ?IReference;
+
+	/**
+	 * Return true if the reference metadata can be globally cached
+	 *
+	 * @since 25.0.0
+	 */
+	public function getCachePrefix(string $referenceId): string;
+
+	/**
+	 * Return a custom cache key to be used for caching the metadata
+	 * This could be for example the current user id if the reference
+	 * access permissions are different for each user
+	 *
+	 * Should return null, if the cache is only related to the
+	 * reference id and has no further dependency
+	 *
+	 * @since 25.0.0
+	 */
+	public function getCacheKey(string $referenceId): ?string;
+}
diff --git a/lib/public/IURLGenerator.php b/lib/public/IURLGenerator.php
index 580536b8b5f..808ba66c862 100644
--- a/lib/public/IURLGenerator.php
+++ b/lib/public/IURLGenerator.php
@@ -35,6 +35,16 @@ namespace OCP;
  * @since 6.0.0
  */
 interface IURLGenerator {
+
+	/**
+	 * Regex for matching http(s) urls
+	 *
+	 * This is a copy of the frontend regex in core/src/OCP/comments.js, make sure to adjust both when changing
+	 *
+	 * @since 25.0.0
+	 */
+	public const URL_REGEX = '/(\s|\n|^)(https?:\/\/)?((?:[-A-Z0-9+_]+\.)+[-A-Z]+(?:\/[-A-Z0-9+&@#%?=~_|!:,.;()]*)*)(\s|\n|$)/mi';
+
 	/**
 	 * Returns the URL for a route
 	 * @param string $routeName the name of the route