feat(Reference): Add public API endpoints to get references

Calling the public API endpoints will check for matching registered
reference providers that implement `IPublicReferenceProvider` and call
their respective functions. If no matching provider is found, the
default `LinkReferenceProvider` will be used to provide open graph data.

The frontend reference widget components will call these endpoints from
unauthorized sessions, e.g. in public shares.

If present, the sharing token of the origin URL is passed to
`resolveReferencePublic()` as additional information for the reference
provider to determine the access scope. This allows the respective
reference providers to determine whether the origin share has access to
the linked resource.

`getCacheKeyPublic` also gets the sharing token so it can scope the cached
entry to it.

Contributes to #45978

Signed-off-by: Jonas <jonas@freesources.org>

core/Controller/ReferenceApiController.php

@@ -10,6 +10,7 @@
 
 use OCA\Core\ResponseDefinitions;
 use OCP\AppFramework\Http;
+use OCP\AppFramework\Http\Attribute\AnonRateLimit;
 use OCP\AppFramework\Http\Attribute\ApiRoute;
 use OCP\AppFramework\Http\DataResponse;
 use OCP\Collaboration\Reference\IDiscoverableReferenceProvider;
@@ -62,6 +63,39 @@ public function extract(string $text, bool $resolve = false, int $limit = 1): Da
 		]);
 	}
 
+	/**
+	 * @PublicPage
+	 *
+	 * Extract references from a text
+	 *
+	 * @param string $text Text to extract from
+	 * @param string $sharingToken Token of the public share
+	 * @param bool $resolve Resolve the references
+	 * @param int $limit Maximum amount of references to extract
+	 * @return DataResponse<Http::STATUS_OK, array{references: array<string, CoreReference|null>}, array{}>
+	 *
+	 * 200: References returned
+	 */
+	#[ApiRoute(verb: 'POST', url: '/extractPublic', root: '/references')]
+	#[AnonRateLimit(limit: 10, period: 120)]
+	public function extractPublic(string $text, string $sharingToken, bool $resolve = false, int $limit = 1): DataResponse {
+		$references = $this->referenceManager->extractReferences($text);
+
+		$result = [];
+		$index = 0;
+		foreach ($references as $reference) {
+			if ($index++ >= $limit) {
+				break;
+			}
+
+			$result[$reference] = $resolve ? $this->referenceManager->resolveReference($reference, true, $sharingToken)->jsonSerialize() : null;
+		}
+
+		return new DataResponse([
+			'references' => $result
+		]);
+	}
+
 	/**
 	 * @NoAdminRequired
 	 *
@@ -73,6 +107,7 @@ public function extract(string $text, bool $resolve = false, int $limit = 1): Da
 	 * 200: Reference returned
 	 */
 	#[ApiRoute(verb: 'GET', url: '/resolve', root: '/references')]
+	#[AnonRateLimit(limit: 10, period: 120)]
 	public function resolveOne(string $reference): DataResponse {
 		/** @var ?CoreReference $resolvedReference */
 		$resolvedReference = $this->referenceManager->resolveReference(trim($reference))?->jsonSerialize();
@@ -82,6 +117,28 @@ public function resolveOne(string $reference): DataResponse {
 		return $response;
 	}
 
+	/**
+	 * @PublicPage
+	 *
+	 * Resolve from a public page
+	 *
+	 * @param string $reference Reference to resolve
+	 * @param string $sharingToken Token of the public share
+	 * @return DataResponse<Http::STATUS_OK, array{references: array<string, ?CoreReference>}, array{}>
+	 *
+	 * 200: Reference returned
+	 */
+	#[ApiRoute(verb: 'GET', url: '/resolvePublic', root: '/references')]
+	#[AnonRateLimit(limit: 10, period: 120)]
+	public function resolveOnePublic(string $reference, string $sharingToken): DataResponse {
+		/** @var ?CoreReference $resolvedReference */
+		$resolvedReference = $this->referenceManager->resolveReference(trim($reference), true, trim($sharingToken))?->jsonSerialize();
+
+		$response = new DataResponse(['references' => [$reference => $resolvedReference]]);
+		$response->cacheFor(3600, false, true);
+		return $response;
+	}
+
 	/**
 	 * @NoAdminRequired
 	 *
@@ -110,6 +167,36 @@ public function resolve(array $references, int $limit = 1): DataResponse {
 		]);
 	}
 
+	/**
+	 * @PublicPage
+	 *
+	 * Resolve multiple references from a public page
+	 *
+	 * @param string[] $references References to resolve
+	 * @param string $sharingToken Token of the public share
+	 * @param int $limit Maximum amount of references to resolve
+	 * @return DataResponse<Http::STATUS_OK, array{references: array<string, CoreReference|null>}, array{}>
+	 *
+	 * 200: References returned
+	 */
+	#[ApiRoute(verb: 'POST', url: '/resolvePublic', root: '/references')]
+	#[AnonRateLimit(limit: 10, period: 120)]
+	public function resolvePublic(array $references, string $sharingToken, int $limit = 1): DataResponse {
+		$result = [];
+		$index = 0;
+		foreach ($references as $reference) {
+			if ($index++ >= $limit) {
+				break;
+			}
+
+			$result[$reference] = $this->referenceManager->resolveReference($reference, true, $sharingToken)?->jsonSerialize();
+		}
+
+		return new DataResponse([
+			'references' => $result
+		]);
+	}
+
 	/**
 	 * @NoAdminRequired
 	 *

lib/private/Collaboration/Reference/ReferenceManager.php

@@ -11,6 +11,7 @@
 use OC\AppFramework\Bootstrap\Coordinator;
 use OC\Collaboration\Reference\File\FileReferenceProvider;
 use OCP\Collaboration\Reference\IDiscoverableReferenceProvider;
+use OCP\Collaboration\Reference\IPublicReferenceProvider;
 use OCP\Collaboration\Reference\IReference;
 use OCP\Collaboration\Reference\IReferenceManager;
 use OCP\Collaboration\Reference\IReferenceProvider;
@@ -59,14 +60,14 @@ public function extractReferences(string $text): array {
 	/**
 	 * Try to get a cached reference object from a reference string
 	 */
-	public function getReferenceFromCache(string $referenceId): ?IReference {
-		$matchedProvider = $this->getMatchedProvider($referenceId);
+	public function getReferenceFromCache(string $referenceId, bool $public = false, string $sharingToken = ''): ?IReference {
+		$matchedProvider = $this->getMatchedProvider($referenceId, $public);
 
 		if ($matchedProvider === null) {
 			return null;
 		}
 
-		$cacheKey = $this->getFullCacheKey($matchedProvider, $referenceId);
+		$cacheKey = $this->getFullCacheKey($matchedProvider, $referenceId, $public, $sharingToken);
 		return $this->getReferenceByCacheKey($cacheKey);
 	}
 
@@ -86,20 +87,24 @@ public function getReferenceByCacheKey(string $cacheKey): ?IReference {
 	 * Get a reference object from a reference string with a matching provider
 	 * Use a cached reference if possible
 	 */
-	public function resolveReference(string $referenceId): ?IReference {
-		$matchedProvider = $this->getMatchedProvider($referenceId);
+	public function resolveReference(string $referenceId, bool $public = false, $sharingToken = ''): ?IReference {
+		$matchedProvider = $this->getMatchedProvider($referenceId, $public);
 
 		if ($matchedProvider === null) {
 			return null;
 		}
 
-		$cacheKey = $this->getFullCacheKey($matchedProvider, $referenceId);
+		$cacheKey = $this->getFullCacheKey($matchedProvider, $referenceId, $public, $sharingToken);
 		$cached = $this->cache->get($cacheKey);
 		if ($cached) {
 			return Reference::fromCache($cached);
 		}
 
-		$reference = $matchedProvider->resolveReference($referenceId);
+		if ($public) {
+			$reference = $matchedProvider->resolveReferencePublic($referenceId, $sharingToken);
+		} else {
+			$reference = $matchedProvider->resolveReference($referenceId);
+		}
 		if ($reference) {
 			$cachePrefix = $matchedProvider->getCachePrefix($referenceId);
 			if ($cachePrefix !== '') {
@@ -119,9 +124,12 @@ public function resolveReference(string $referenceId): ?IReference {
 	 *
 	 * @return IReferenceProvider|null the first matching provider
 	 */
-	private function getMatchedProvider(string $referenceId): ?IReferenceProvider {
+	private function getMatchedProvider(string $referenceId, bool $public): ?IReferenceProvider {
 		$matchedProvider = null;
 		foreach ($this->getProviders() as $provider) {
+			if ($public && !($provider instanceof IPublicReferenceProvider)) {
+				continue;
+			}
 			$matchedProvider = $provider->matchReference($referenceId) ? $provider : null;
 			if ($matchedProvider !== null) {
 				break;
@@ -138,8 +146,13 @@ private function getMatchedProvider(string $referenceId): ?IReferenceProvider {
 	/**
 	 * Get a hashed full cache key from a key and prefix given by a provider
 	 */
-	private function getFullCacheKey(IReferenceProvider $provider, string $referenceId): string {
-		$cacheKey = $provider->getCacheKey($referenceId);
+	private function getFullCacheKey(IReferenceProvider $provider, string $referenceId, bool $public, string $sharingToken): string {
+		if ($public && !($provider instanceof IPublicReferenceProvider)) {
+			throw new \RuntimeException('Provider doesn\'t support public lookups');
+		}
+		$cacheKey = $public
+			? $provider->getCacheKeyPublic($referenceId, $sharingToken)
+			: $provider->getCacheKey($referenceId);
 		return md5($provider->getCachePrefix($referenceId)) . (
 			$cacheKey !== null ? ('-' . md5($cacheKey)) : ''
 		);

lib/public/Collaboration/Reference/IPublicReferenceProvider.php

@@ -0,0 +1,33 @@
+<?php
+
+declare(strict_types=1);
+/**
+ * SPDX-FileCopyrightText: 2022 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace OCP\Collaboration\Reference;
+
+/**
+ * @since 30.0.0
+ */
+interface IPublicReferenceProvider extends IReferenceProvider {
+	/**
+	 * Return a reference with its metadata for a given reference identifier and sharingToken
+	 *
+	 * @since 30.0.0
+	 */
+	public function resolveReferencePublic(string $referenceText, string $sharingToken): ?IReference;
+
+	/**
+	 * Return a custom cache key to be used for caching the metadata
+	 * This could be for example the current sharingToken if the reference
+	 * access permissions are different for each share
+	 *
+	 * Should return null, if the cache is only related to the
+	 * reference id and has no further dependency
+	 *
+	 * @since 30.0.0
+	 */
+	public function getCacheKeyPublic(string $referenceId, string $sharingToken): ?string;
+}

lib/public/Collaboration/Reference/IReferenceManager.php

@@ -27,8 +27,9 @@ public function extractReferences(string $text): array;
 	 * but may still return null in case this is disabled or the fetching fails
 	 *
 	 * @since 25.0.0
+	 * @since 30.0.0 optional arguments `$public` and `$sharingToken`
 	 */
-	public function resolveReference(string $referenceId): ?IReference;
+	public function resolveReference(string $referenceId, bool $public = false, string $sharingToken = ''): ?IReference;
 
 	/**
 	 * Get a reference by its cache key
@@ -42,8 +43,9 @@ public function getReferenceByCacheKey(string $cacheKey): ?IReference;
 	 * the cache can then be filled with a separate request from the frontend
 	 *
 	 * @since 25.0.0
+	 * @since 30.0.0 optional arguments `$public` and `$sharingToken`
 	 */
-	public function getReferenceFromCache(string $referenceId): ?IReference;
+	public function getReferenceFromCache(string $referenceId, bool $public = false, string $sharingToken = ''): ?IReference;
 
 	/**
 	 * Invalidate all cache entries with a prefix or just one if the cache key is provided

lib/public/Collaboration/Reference/LinkReferenceProvider.php

@@ -26,7 +26,7 @@
 /**
  * @since 29.0.0
  */
-class LinkReferenceProvider implements IReferenceProvider {
+class LinkReferenceProvider implements IReferenceProvider, IPublicReferenceProvider {
 
 	/**
 	 * for image size and webpage header
@@ -87,6 +87,14 @@ public function resolveReference(string $referenceText): ?IReference {
 		return null;
 	}
 
+	/**
+	 * @inheritDoc
+	 * @since 30.0.0
+	 */
+	public function resolveReferencePublic(string $referenceText, string $sharingToken): ?IReference {
+		return $this->resolveReference($referenceText);
+	}
+
 	/**
 	 * Populates the reference with OpenGraph data
 	 *
@@ -201,4 +209,12 @@ public function getCachePrefix(string $referenceId): string {
 	public function getCacheKey(string $referenceId): ?string {
 		return null;
 	}
+
+	/**
+	 * @inheritDoc
+	 * @since 30.0.0
+	 */
+	public function getCacheKeyPublic(string $referenceId, string $sharingToken): ?string {
+		return null;
+	}
 }