validate form to rename entry

lib/model/image_entry.dart

@@ -10,16 +10,14 @@ import 'package:aves/utils/time_utils.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:geocoder/geocoder.dart';
-import 'package:path/path.dart';
+import 'package:path/path.dart' as ppath;
 import 'package:tuple/tuple.dart';
 
 import 'mime_types.dart';
 
 class ImageEntry {
   String uri;
-  String _path;
-  String _directory;
-  String _filename;
+  String _path, _directory, _filename, _extension;
   int contentId;
   final String sourceMimeType;
   int width;
@@ -131,20 +129,26 @@ class ImageEntry {
     _path = path;
     _directory = null;
     _filename = null;
+    _extension = null;
   }
 
   String get path => _path;
 
   String get directory {
-    _directory ??= path != null ? dirname(path) : null;
+    _directory ??= path != null ? ppath.dirname(path) : null;
     return _directory;
   }
 
   String get filenameWithoutExtension {
-    _filename ??= path != null ? basenameWithoutExtension(path) : null;
+    _filename ??= path != null ? ppath.basenameWithoutExtension(path) : null;
     return _filename;
   }
 
+  String get extension {
+    _extension ??= path != null ? ppath.extension(path) : null;
+    return _extension;
+  }
+
   // the MIME type reported by the Media Store is unreliable
   // so we use the one found during cataloguing if possible
   String get mimeType => catalogMetadata?.mimeType ?? sourceMimeType;
@@ -318,7 +322,7 @@ class ImageEntry {
   Future<bool> rename(String newName) async {
     if (newName == filenameWithoutExtension) return true;
 
-    final newFields = await ImageFileService.rename(this, '$newName${extension(this.path)}');
+    final newFields = await ImageFileService.rename(this, '$newName$extension');
     if (newFields.isEmpty) return false;
 
     final uri = newFields['uri'];

lib/widgets/common/action_delegates/create_album_dialog.dart

@@ -77,6 +77,7 @@ class _CreateAlbumDialogState extends State<CreateAlbumDialog> {
                     helperText: exists ? 'Album already exists' : '',
                     hintText: 'Album name',
                   ),
+                  autofocus: _allVolumes.length == 1,
                   onChanged: (_) => _validate(),
                   onSubmitted: (_) => _submit(context),
                 );
@@ -96,7 +97,7 @@ class _CreateAlbumDialogState extends State<CreateAlbumDialog> {
               child: Text('Create'.toUpperCase()),
             );
           },
-        )
+        ),
       ],
     );
   }

lib/widgets/common/action_delegates/rename_entry_dialog.dart

@@ -1,5 +1,8 @@
+import 'dart:io';
+
 import 'package:aves/model/image_entry.dart';
 import 'package:flutter/material.dart';
+import 'package:path/path.dart';
 
 import '../aves_dialog.dart';
 
@@ -14,11 +17,13 @@ class RenameEntryDialog extends StatefulWidget {
 
 class _RenameEntryDialogState extends State<RenameEntryDialog> {
   final TextEditingController _nameController = TextEditingController();
+  final ValueNotifier<bool> _isValidNotifier = ValueNotifier(false);
+
+  ImageEntry get entry => widget.entry;
 
   @override
   void initState() {
     super.initState();
-    final entry = widget.entry;
     _nameController.text = entry.filenameWithoutExtension ?? entry.sourceTitle;
   }
 
@@ -34,17 +39,35 @@ class _RenameEntryDialogState extends State<RenameEntryDialog> {
       content: TextField(
         controller: _nameController,
         autofocus: true,
+        onChanged: (_) => _validate(),
+        onSubmitted: (_) => _submit(context),
       ),
       actions: [
         FlatButton(
           onPressed: () => Navigator.pop(context),
           child: Text('Cancel'.toUpperCase()),
         ),
-        FlatButton(
-          onPressed: () => Navigator.pop(context, _nameController.text),
+        ValueListenableBuilder<bool>(
+          valueListenable: _isValidNotifier,
+          builder: (context, isValid, child) {
+            return FlatButton(
+              onPressed: isValid ? () => _submit(context) : null,
               child: Text('Apply'.toUpperCase()),
-        ),
+            );
+          },
+        )
       ],
     );
   }
+
+  Future<void> _validate() async {
+    var newName = _nameController.text ?? '';
+    if (newName.isNotEmpty) {
+      newName += entry.extension;
+    }
+    final type = await FileSystemEntity.type(join(entry.directory, newName));
+    _isValidNotifier.value = type == FileSystemEntityType.notFound;
+  }
+
+  void _submit(BuildContext context) => Navigator.pop(context, _nameController.text);
 }