return available drive letters on windows

web/repertory/lib/models/mount.dart

@@ -101,6 +101,34 @@ class Mount with ChangeNotifier {
     }
   }
 
+  Future<List<String>> getAvailableLocations() async {
+    try {
+      final auth = await _auth.createAuth();
+      final response = await http.get(
+        Uri.parse(
+          Uri.encodeFull(
+            '${getBaseUri()}/api/v1/mount_location?auth=$auth&name=$name&type=$type',
+          ),
+        ),
+      );
+
+      if (response.statusCode == 401) {
+        _auth.logoff();
+        return <String>[];
+      }
+
+      if (response.statusCode != 200) {
+        return <String>[];
+      }
+
+      return jsonDecode(response.body) as List<String>;
+    } catch (e) {
+      debugPrint('$e');
+    }
+
+    return <String>[];
+  }
+
   Future<String?> getMountLocation() async {
     try {
       final auth = await _auth.createAuth();

web/repertory/lib/widgets/mount_widget.dart

@@ -149,39 +149,66 @@ class _MountWidgetState extends State<MountWidget> {
       return location;
     }
 
+    final available = await mount.getAvailableLocations();
+
     String? currentLocation;
     return await showDialog(
       context: context,
       builder: (context) {
-        return AlertDialog(
-          actions: [
-            TextButton(
-              child: const Text('Cancel'),
-              onPressed: () => Navigator.of(context).pop(null),
-            ),
-            TextButton(
-              child: const Text('OK'),
-              onPressed: () {
-                final result = getSettingValidators('Path').firstWhereOrNull(
-                  (validator) => !validator(currentLocation ?? ''),
-                );
-                if (result != null) {
-                  return displayErrorMessage(
-                    context,
-                    "Mount location is not valid",
-                  );
-                }
-                Navigator.of(context).pop(currentLocation);
-              },
-            ),
-          ],
-          content: TextField(
-            autofocus: true,
-            controller: TextEditingController(text: currentLocation),
-            inputFormatters: [FilteringTextInputFormatter.deny(RegExp(r'\s'))],
-            onChanged: (value) => currentLocation = value,
-          ),
-          title: const Text('Set Mount Location'),
+        return StatefulBuilder(
+          builder: (context, setState) {
+            return AlertDialog(
+              actions: [
+                TextButton(
+                  child: const Text('Cancel'),
+                  onPressed: () => Navigator.of(context).pop(null),
+                ),
+                TextButton(
+                  child: const Text('OK'),
+                  onPressed: () {
+                    final result = getSettingValidators(
+                      'Path',
+                    ).firstWhereOrNull(
+                      (validator) => !validator(currentLocation ?? ''),
+                    );
+                    if (result != null) {
+                      return displayErrorMessage(
+                        context,
+                        "Mount location is not valid",
+                      );
+                    }
+                    Navigator.of(context).pop(currentLocation);
+                  },
+                ),
+              ],
+              content:
+                  available.isEmpty
+                      ? TextField(
+                        autofocus: true,
+                        controller: TextEditingController(
+                          text: currentLocation,
+                        ),
+                        inputFormatters: [
+                          FilteringTextInputFormatter.deny(RegExp(r'\s')),
+                        ],
+                        onChanged:
+                            (value) => setState(() => currentLocation = value),
+                      )
+                      : DropdownButton<String>(
+                        value: currentLocation,
+                        onChanged:
+                            (value) => setState(() => currentLocation = value),
+                        items:
+                            available.map<DropdownMenuItem<String>>((item) {
+                              return DropdownMenuItem<String>(
+                                value: item,
+                                child: Text(item),
+                              );
+                            }).toList(),
+                      ),
+              title: const Text('Set Mount Location'),
+            );
+          },
         );
       },
     );