feat: remember uploaded file name on web and use it when downloading

lib/routing/router.dart

@@ -31,7 +31,11 @@ final routerProvider = Provider<GoRouter>((ref) {
             onPickPdf: () => sessionVm.pickAndOpenPdf(),
             onOpenPdf:
                 ({String? path, Uint8List? bytes, String? fileName}) =>
-                    sessionVm.openPdf(path: path, bytes: bytes),
+                    sessionVm.openPdf(
+                      path: path,
+                      bytes: bytes,
+                      fileName: fileName,
+                    ),
           );
         },
       ),
@@ -43,6 +47,7 @@ final routerProvider = Provider<GoRouter>((ref) {
             onPickPdf: () => sessionVm.pickAndOpenPdf(),
             onClosePdf: () => sessionVm.closePdf(),
             currentFile: sessionVm.currentFile,
+            currentFileName: sessionVm.displayFileName,
           );
         },
       ),

lib/ui/features/pdf/view_model/pdf_export_view_model.dart

@@ -10,14 +10,27 @@ class PdfExportViewModel extends ChangeNotifier {
 
   // Dependencies (injectable via constructor for tests)
   final ExportService _exporter;
+  // Zero-arg picker retained for backward compatibility with tests.
   final Future<String?> Function() _savePathPicker;
+  // Preferred picker that accepts a suggested filename.
+  final Future<String?> Function(String suggestedName)
+  _savePathPickerWithSuggestedName;
 
   PdfExportViewModel(
     this.ref, {
     ExportService? exporter,
     Future<String?> Function()? savePathPicker,
+    Future<String?> Function(String suggestedName)?
+    savePathPickerWithSuggestedName,
   }) : _exporter = exporter ?? ExportService(),
-       _savePathPicker = savePathPicker ?? _defaultSavePathPicker;
+       _savePathPicker = savePathPicker ?? _defaultSavePathPicker,
+       // Prefer provided suggested-name picker; otherwise, if only zero-arg
+       // picker is given (tests), wrap it; else use default that honors name.
+       _savePathPickerWithSuggestedName =
+           savePathPickerWithSuggestedName ??
+           (savePathPicker != null
+               ? ((_) => savePathPicker())
+               : _defaultSavePathPickerWithSuggestedName);
 
   bool get exporting => _exporting;
 
@@ -35,11 +48,22 @@ class PdfExportViewModel extends ChangeNotifier {
     return _savePathPicker();
   }
 
+  /// Show save dialog with a suggested name and return the chosen path.
+  Future<String?> pickSavePathWithSuggestedName(String suggestedName) async {
+    return _savePathPickerWithSuggestedName(suggestedName);
+  }
+
   static Future<String?> _defaultSavePathPicker() async {
+    return _defaultSavePathPickerWithSuggestedName('signed.pdf');
+  }
+
+  static Future<String?> _defaultSavePathPickerWithSuggestedName(
+    String suggestedName,
+  ) async {
     final group = fs.XTypeGroup(label: 'PDF', extensions: ['pdf']);
     final location = await fs.getSaveLocation(
       acceptedTypeGroups: [group],
-      suggestedName: 'signed.pdf',
+      suggestedName: suggestedName,
       confirmButtonText: 'Save',
     );
     return location?.path; // null if user cancels

lib/ui/features/pdf/view_model/pdf_view_model.dart

@@ -1,4 +1,5 @@
 import 'dart:typed_data';
+import 'package:file_selector/file_selector.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:pdf_signature/data/repositories/document_repository.dart';
@@ -243,14 +244,21 @@ class PdfSessionViewModel extends ChangeNotifier {
   final Ref ref;
   final GoRouter router;
   fs.XFile _currentFile = fs.XFile('');
+  // Keep a human display name in addition to XFile, because on Linux via
+  // xdg-desktop-portal the path can look like /run/user/.../doc/<UUID>, and
+  // XFile.name derives from that basename, yielding a random UUID instead of
+  // the actual filename the user selected. We preserve the picker/drop name
+  // here to offer a sensible default like "signed_<original>.pdf".
+  String _displayFileName = '';
 
   PdfSessionViewModel({required this.ref, required this.router});
 
   fs.XFile get currentFile => _currentFile;
+  String get displayFileName => _displayFileName;
 
   Future<void> pickAndOpenPdf() async {
     final typeGroup = const fs.XTypeGroup(label: 'PDF', extensions: ['pdf']);
-    final file = await fs.openFile(acceptedTypeGroups: [typeGroup]);
+    final XFile? file = await fs.openFile(acceptedTypeGroups: [typeGroup]);
     if (file != null) {
       Uint8List? bytes;
       try {
@@ -258,11 +266,15 @@ class PdfSessionViewModel extends ChangeNotifier {
       } catch (_) {
         bytes = null;
       }
-      await openPdf(path: file.path, bytes: bytes);
+      await openPdf(path: file.path, bytes: bytes, fileName: file.name);
     }
   }
 
-  Future<void> openPdf({String? path, Uint8List? bytes}) async {
+  Future<void> openPdf({
+    String? path,
+    Uint8List? bytes,
+    String? fileName,
+  }) async {
     int pageCount = 1; // default
     if (bytes != null) {
       try {
@@ -272,8 +284,31 @@ class PdfSessionViewModel extends ChangeNotifier {
         // ignore invalid bytes
       }
     }
-    if (path != null) {
+    if (path != null && path.isNotEmpty) {
       _currentFile = fs.XFile(path);
+    } else if (bytes != null && (fileName != null && fileName.isNotEmpty)) {
+      // Keep in-memory XFile so .name is available for suggestion
+      try {
+        _currentFile = fs.XFile.fromData(
+          bytes,
+          name: fileName,
+          mimeType: 'application/pdf',
+        );
+      } catch (_) {
+        _currentFile = fs.XFile(fileName);
+      }
+    } else {
+      _currentFile = fs.XFile('');
+    }
+
+    // Update display name: prefer explicit fileName (from picker/drop),
+    // fall back to basename of path, otherwise empty.
+    if (fileName != null && fileName.isNotEmpty) {
+      _displayFileName = fileName;
+    } else if (path != null && path.isNotEmpty) {
+      _displayFileName = path.split('/').last.split('\\').last;
+    } else {
+      _displayFileName = '';
     }
     ref
         .read(documentRepositoryProvider.notifier)
@@ -287,6 +322,7 @@ class PdfSessionViewModel extends ChangeNotifier {
     ref.read(documentRepositoryProvider.notifier).close();
     ref.read(signatureCardRepositoryProvider.notifier).clearAll();
     _currentFile = fs.XFile('');
+    _displayFileName = '';
     router.go('/');
     notifyListeners();
   }

lib/ui/features/pdf/widgets/pdf_screen.dart

@@ -20,12 +20,18 @@ class PdfSignatureHomePage extends ConsumerStatefulWidget {
   final Future<void> Function() onPickPdf;
   final VoidCallback onClosePdf;
   final fs.XFile currentFile;
+  // Optional display name for the currently opened file. On Linux
+  // xdg-desktop-portal, XFile.name/path can be a UUID-like value. When
+  // available, this name preserves the user-selected filename so we can
+  // suggest a proper "signed_*.pdf" on save.
+  final String? currentFileName;
 
   const PdfSignatureHomePage({
     super.key,
     required this.onPickPdf,
     required this.onClosePdf,
     required this.currentFile,
+    this.currentFileName,
   });
 
   @override
@@ -152,8 +158,23 @@ class _PdfSignatureHomePageState extends ConsumerState<PdfSignatureHomePage> {
       bool ok = false;
       String? savedPath;
 
+      // Derive a suggested filename based on the opened file. Prefer the
+      // provided display name if available (see Linux portal note above).
+      final display = widget.currentFileName;
+      final originalName =
+          (display != null && display.trim().isNotEmpty)
+              ? display.trim()
+              : widget.currentFile.name.isNotEmpty
+              ? widget.currentFile.name
+              : widget.currentFile.path.isNotEmpty
+              ? widget.currentFile.path.split('/').last.split('\\').last
+              : 'document.pdf';
+      final suggested = _suggestSignedName(originalName);
+
       if (!kIsWeb) {
-        final path = await ref.read(pdfExportViewModelProvider).pickSavePath();
+        final path = await ref
+            .read(pdfExportViewModelProvider)
+            .pickSavePathWithSuggestedName(suggested);
         if (path == null || path.trim().isEmpty) return;
         final fullPath = _ensurePdfExtension(path.trim());
         savedPath = fullPath;
@@ -179,9 +200,9 @@ class _PdfSignatureHomePageState extends ConsumerState<PdfSignatureHomePage> {
           targetDpi: targetDpi,
         );
         if (out != null) {
-          // Use a sensible default filename (cannot prompt path on web)
-          ok = await downloadBytes(out, filename: 'signed.pdf');
-          savedPath = 'signed.pdf';
+          // Use suggested filename for browser download
+          ok = await downloadBytes(out, filename: suggested);
+          savedPath = suggested;
         }
       }
       if (!kIsWeb) {
@@ -224,6 +245,15 @@ class _PdfSignatureHomePageState extends ConsumerState<PdfSignatureHomePage> {
     return name;
   }
 
+  String _suggestSignedName(String original) {
+    // Normalize to a base filename
+    final base = original.split('/').last.split('\\').last;
+    if (base.toLowerCase().endsWith('.pdf')) {
+      return 'signed_' + base;
+    }
+    return 'signed_' + base + '.pdf';
+  }
+
   void _onControllerChanged() {
     if (mounted) {
       if (_viewModel.controller.isReady) {

lib/ui/features/welcome/widgets/welcome_screen.dart

@@ -46,7 +46,7 @@ Future<void> handleDroppedFiles(
     bytes = null;
   }
   final String path = pdf.path ?? pdf.name;
-  await onOpenPdf(path: path, bytes: bytes);
+  await onOpenPdf(path: path, bytes: bytes, fileName: pdf.name);
 }
 
 class WelcomeScreen extends ConsumerStatefulWidget {