feat: make preview conversion timeout and max file size configurable

Signed-off-by: Julius Knorr <jus@bitgrid.net>

Author: juliusknorr

docs/app_settings.md

@@ -41,6 +41,14 @@ By default Nextcloud will generate previews of Office files using the Collabora
 
 	occ config:app:set richdocuments preview_generation --type boolean --lazy --value false
 
+The timeout for preview conversion requests (in seconds) can be configured. The default is 5 seconds:
+
+	occ config:app:set richdocuments preview_conversion_timeout --type integer --value 10
+
+Files larger than the configured maximum file size will be skipped and no preview will be generated. The default limit is 100 MB (104857600 bytes):
+
+	occ config:app:set richdocuments preview_conversion_max_filesize --type integer --value 52428800
+
 ### Electronic signature
 From a shell running in the Nextcloud root directory, run the following `occ`
 command to configure a non-default base URL for eID Easy. For example:

lib/AppConfig.php

@@ -32,9 +32,14 @@ class AppConfig {
 	// Default: 'no', set to 'yes' to enable
 	public const USE_SECURE_VIEW_ADDITIONAL_MIMES = 'use_secure_view_additional_mimes';
 
+	public const PREVIEW_CONVERSION_TIMEOUT = 'preview_conversion_timeout';
+	public const PREVIEW_CONVERSION_MAX_FILESIZE = 'preview_conversion_max_filesize';
+
 	private array $defaults = [
 		'wopi_url' => '',
 		'timeout' => 15,
+		'preview_conversion_timeout' => 5,
+		'preview_conversion_max_filesize' => 104857600, // 100 MB
 		'watermark_text' => '{userId}',
 		'watermark_allGroupsList' => [],
 		'watermark_allTagsList' => [],
@@ -248,6 +253,21 @@ public function isPreviewGenerationEnabled(): bool {
 		return $this->appConfig->getAppValueBool('preview_generation', true);
 	}
 
+	/**
+	 * Returns the timeout in seconds for preview conversion requests to Collabora.
+	 */
+	public function getPreviewConversionTimeout(): int {
+		return (int)$this->getAppValue(self::PREVIEW_CONVERSION_TIMEOUT);
+	}
+
+	/**
+	 * Returns the maximum file size in bytes for which preview conversion is attempted.
+	 * Files larger than this limit will be skipped and return no preview.
+	 */
+	public function getPreviewConversionMaxFileSize(): int {
+		return (int)$this->getAppValue(self::PREVIEW_CONVERSION_MAX_FILESIZE);
+	}
+
 	private function getGSDomains(): array {
 		if (!$this->globalScaleConfig->isGlobalScaleEnabled()) {
 			return [];

lib/Preview/Office.php

@@ -42,6 +42,16 @@ public function getThumbnail(File $file, int $maxX, int $maxY): ?IImage {
 			return null;
 		}
 
+		$fileSize = $file->getSize();
+		$maxFileSize = $this->appConfig->getPreviewConversionMaxFileSize();
+		if ($fileSize > $maxFileSize) {
+			$this->logger->debug('Skipping preview conversion: file size {size} exceeds limit {limit}', [
+				'size' => $fileSize,
+				'limit' => $maxFileSize,
+			]);
+			return null;
+		}
+
 		try {
 			$response = $this->remoteService->convertFileTo($file, 'png');
 			$image = new Image();

lib/Service/RemoteService.php

@@ -66,16 +66,17 @@ public function convertFileTo(File $file, string $format) {
 		if ($stream === false) {
 			throw new Exception('Failed to open stream');
 		}
-		return $this->convertTo($file->getName(), $stream, $format);
+		$timeout = $this->appConfig->getPreviewConversionTimeout();
+		return $this->convertTo($file->getName(), $stream, $format, [], $timeout);
 	}
 
 	/**
 	 * @param resource $stream
 	 * @return resource|string
 	 */
-	public function convertTo(string $filename, $stream, string $format, ?array $conversionOptions = []) {
+	public function convertTo(string $filename, $stream, string $format, ?array $conversionOptions = [], int $timeout = RemoteOptionsService::REMOTE_TIMEOUT_DEFAULT) {
 		$client = $this->clientService->newClient();
-		$options = RemoteOptionsService::getDefaultOptions();
+		$options = RemoteOptionsService::getDefaultOptions($timeout);
 		// FIXME: can be removed once https://github.com/CollaboraOnline/online/issues/6983 is fixed upstream
 		$options['expect'] = false;