From eb1d482e2498973d8b5efdc60661bcb043a94571 Mon Sep 17 00:00:00 2001
From: Nicolas Kogler <nicolas.kogler@outlook.com>
Date: Wed, 13 May 2026 23:47:31 +0200
Subject: [PATCH] fix: avoid startup crash when saved appdata path is
 unavailable

---
 .../Features/Settings/PathManagerTests.cs     | 27 +++++++++++++++++++
 WheelWizard/Services/PathManager.cs           | 23 +++++++++++++++-
 2 files changed, 49 insertions(+), 1 deletion(-)
 create mode 100644 WheelWizard.Test/Features/Settings/PathManagerTests.cs

diff --git a/WheelWizard.Test/Features/Settings/PathManagerTests.cs b/WheelWizard.Test/Features/Settings/PathManagerTests.cs
new file mode 100644
index 00000000..fbef7d2a
--- /dev/null
+++ b/WheelWizard.Test/Features/Settings/PathManagerTests.cs
@@ -0,0 +1,27 @@
+using WheelWizard.Services;
+
+namespace WheelWizard.Test.Features.Settings;
+
+[Collection("SettingsFeature")]
+public class PathManagerTests
+{
+    [Fact]
+    public void TrySetWheelWizardAppdataPath_ReturnsFalse_WhenTargetPathIsUnavailable()
+    {
+        if (!OperatingSystem.IsWindows())
+            return;
+
+        var unavailablePath = GetUnavailableWindowsPath();
+        var result = PathManager.TrySetWheelWizardAppdataPath(unavailablePath, out var errorMessage, out _);
+
+        Assert.False(result);
+        Assert.False(string.IsNullOrWhiteSpace(errorMessage));
+    }
+
+    private static string GetUnavailableWindowsPath()
+    {
+        var used = DriveInfo.GetDrives().Select(d => char.ToUpperInvariant(d.Name[0])).ToHashSet();
+        var drive = "ZYXWVUTSRQPONMLKJIHGFEDCBA".FirstOrDefault(letter => !used.Contains(letter), 'Z');
+        return $@"{drive}:\WheelWizardTests\{Guid.NewGuid():N}";
+    }
+}
diff --git a/WheelWizard/Services/PathManager.cs b/WheelWizard/Services/PathManager.cs
index 998bce82..d7e5fdca 100644
--- a/WheelWizard/Services/PathManager.cs
+++ b/WheelWizard/Services/PathManager.cs
@@ -95,7 +95,15 @@ public static bool IsUsingCustomWheelWizardAppdataPath
                 return null;
 
             var normalized = FileHelper.NormalizePath(storedPath);
-            return FileHelper.PathsEqual(normalized, DefaultWheelWizardAppdataPath) ? null : normalized;
+            if (FileHelper.PathsEqual(normalized, DefaultWheelWizardAppdataPath))
+                return null;
+
+            // If a previously selected custom location is no longer available (for example,
+            // when an external drive letter changes), fall back to the default path.
+            if (!TryEnsureWheelWizardAppdataPathAccessible(normalized))
+                return null;
+
+            return normalized;
         }
         catch
         {
@@ -103,6 +111,19 @@ public static bool IsUsingCustomWheelWizardAppdataPath
         }
     }
 
+    private static bool TryEnsureWheelWizardAppdataPathAccessible(string normalizedPath)
+    {
+        try
+        {
+            FileHelper.EnsureDirectory(normalizedPath);
+            return true;
+        }
+        catch
+        {
+            return false;
+        }
+    }
+
     private static string? LoadPersistedWheelWizardAppdataOverride()
     {
 #if WINDOWS