implemented Nextcloud file previews for unknown file types using fileId and has-preview flags, updated file models, and refined manual refresh logic.

lib/api/marianumcloud/webdav/queries/list_files/cacheable_file.dart

@@ -15,6 +15,16 @@ class CacheableFile {
   DateTime? modifiedAt;
   String? sort;
 
+  /// Nextcloud's instance-local file id (`oc:fileid`). Used to address the
+  /// preview API by id, which is more reliable than the path-based variant
+  /// on some server configurations.
+  int? fileId;
+
+  /// Server's answer to "can I render a thumbnail for this file?"
+  /// (`nc:has-preview`). Lets the file viewer skip the placeholder text
+  /// when a preview is going to load anyway.
+  bool? hasPreview;
+
   CacheableFile({
     required this.path,
     required this.isDirectory,
@@ -24,6 +34,8 @@ class CacheableFile {
     this.eTag,
     this.createdAt,
     this.modifiedAt,
+    this.fileId,
+    this.hasPreview,
   });
 
   CacheableFile.fromDavFile(WebDavFile file) {
@@ -35,6 +47,8 @@ class CacheableFile {
     eTag = file.etag;
     createdAt = file.createdDate;
     modifiedAt = file.lastModified;
+    fileId = int.tryParse(file.fileId ?? '');
+    hasPreview = file.hasPreview;
   }
 
   factory CacheableFile.fromJson(Map<String, dynamic> json) =>

lib/api/marianumcloud/webdav/queries/list_files/cacheable_file.g.dart

@@ -20,6 +20,8 @@ CacheableFile _$CacheableFileFromJson(Map<String, dynamic> json) =>
       modifiedAt: json['modifiedAt'] == null
           ? null
           : DateTime.parse(json['modifiedAt'] as String),
+      fileId: (json['fileId'] as num?)?.toInt(),
+      hasPreview: json['hasPreview'] as bool?,
     )..sort = json['sort'] as String?;
 
 Map<String, dynamic> _$CacheableFileToJson(CacheableFile instance) =>
@@ -33,4 +35,6 @@ Map<String, dynamic> _$CacheableFileToJson(CacheableFile instance) =>
       'createdAt': instance.createdAt?.toIso8601String(),
       'modifiedAt': instance.modifiedAt?.toIso8601String(),
       'sort': instance.sort,
+      'fileId': instance.fileId,
+      'hasPreview': instance.hasPreview,
     };

lib/api/marianumcloud/webdav/queries/list_files/list_files.dart

@@ -25,8 +25,23 @@ class ListFiles extends WebdavApi<ListFilesParams> {
   Future<ListFilesResponse> run() async {
     final webdav = await WebdavApi.webdav;
     final timeout = _isRoot ? _rootTimeout : _subfolderTimeout;
+    // Explicit prop list — without it the server omits OC-namespaced
+    // properties like oc:fileid, which the preview endpoint relies on.
+    final prop = WebDavPropWithoutValues.fromBools(
+      davgetlastmodified: true,
+      davgetetag: true,
+      davgetcontenttype: true,
+      davgetcontentlength: true,
+      davresourcetype: true,
+      ocfileid: true,
+      ocsize: true,
+      nccreationtime: true,
+      nchaspreview: true,
+    );
     final davFiles =
-        (await webdav.propfind(PathUri.parse(params.path)).timeout(timeout))
+        (await webdav
+                .propfind(PathUri.parse(params.path), prop: prop)
+                .timeout(timeout))
             .toWebDavFiles();
     final files = davFiles.map(CacheableFile.fromDavFile).toSet();