fix ftp external storage with filezilla server

- filezilla doesn't like "" as parameter for `mdtm` (all others seem fine)
- filezilla sends fractional modified date

Signed-off-by: Robin Appelman <robin@icewind.nl>

apps/files_external/lib/Lib/Storage/FTP.php

@@ -123,7 +123,8 @@ public function filemtime($path) {
 					return $item['type'] === 'cdir';
 				}));
 				if ($currentDir) {
-					$time = \DateTime::createFromFormat('YmdHis', $currentDir['modify'] ?? '');
+					[$modify] = explode('.', $currentDir['modify'] ?? '', 2);
+					$time = \DateTime::createFromFormat('YmdHis', $modify);
 					if ($time === false) {
 						throw new \Exception("Invalid date format for directory: $currentDir");
 					}
@@ -355,10 +356,11 @@ public function getDirectoryContent($directory): \Traversable {
 
 			$data = [];
 			$data['mimetype'] = $isDir ? FileInfo::MIMETYPE_FOLDER : $mimeTypeDetector->detectPath($name);
-			$data['mtime'] = \DateTime::createFromFormat('YmdGis', $file['modify'])->getTimestamp();
-			if ($data['mtime'] === false) {
-				$data['mtime'] = time();
-			}
+
+			// strip fractional seconds
+			[$modify] = explode('.', $file['modify'], 2);
+			$mtime = \DateTime::createFromFormat('YmdGis', $modify);
+			$data['mtime'] = $mtime === false ? time() : $mtime->getTimestamp();
 			if ($isDir) {
 				$data['size'] = -1; //unknown
 			} elseif (isset($file['size'])) {

apps/files_external/lib/Lib/Storage/FtpConnection.php

@@ -89,8 +89,14 @@ public function rename(string $source, string $target) {
 		return @ftp_rename($this->connection, $source, $target);
 	}
 
-	public function mdtm(string $path) {
-		return @ftp_mdtm($this->connection, $path);
+	public function mdtm(string $path): int {
+		$result = @ftp_mdtm($this->connection, $path);
+
+		// filezilla doesn't like empty path with mdtm
+		if ($result === -1 && $path === "") {
+			$result = @ftp_mdtm($this->connection, "/");
+		}
+		return $result;
 	}
 
 	public function size(string $path) {