1 files changed, 49 insertions, 0 deletions
diff --git a/src/Godosa.Core/SettingsFile.cs b/src/Godosa.Core/SettingsFile.cs
new file mode 100644
index 0000000..6aca17e
--- /dev/null
+++ b/src/Godosa.Core/SettingsFile.cs
@@ -0,0 +1,49 @@
+namespace Godosa.Core;
+
+/// <summary>A settings file on disk. Failures never stop the game: any load failure
+/// (missing file excepted: plain defaults) → defaults + a stderr line; save failure →
+/// stderr. Saves write a temp file then rename, so a crash never leaves half a file.
+/// <paramref name="report"/> receives those lines (default: stderr).</summary>
+public sealed class SettingsFile<T>(string path, Func<string, T> parse, Func<T, string> serialize, Func<T> defaults,
+    Action<string>? report = null)
+{
+    private readonly Action<string> _report = report ?? Console.Error.WriteLine;
+
+    public string Path => path;
+
+    /// <summary>The override variable's value when set, else
+    /// <c>ApplicationData/&lt;appFolder&gt;/settings.json</c>.</summary>
+    public static string DefaultPath(string environmentOverride, string appFolder) =>
+        Environment.GetEnvironmentVariable(environmentOverride) is { Length: > 0 } overridden
+            ? overridden
+            : System.IO.Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData), appFolder, "settings.json");
+
+    public T Load()
+    {
+        try
+        {
+            return File.Exists(path) ? parse(File.ReadAllText(path)) : defaults();
+        }
+        catch (Exception e) when (e is not OutOfMemoryException)
+        {
+            _report($"settings: load failed ({e.Message}); using defaults");
+            return defaults();
+        }
+    }
+
+    public void Save(T value)
+    {
+        string temp = path + ".tmp";
+        try
+        {
+            Directory.CreateDirectory(System.IO.Path.GetDirectoryName(System.IO.Path.GetFullPath(path))!); // a bare name: the working folder
+            File.WriteAllText(temp, serialize(value));
+            File.Move(temp, path, overwrite: true);
+        }
+        catch (Exception e) when (e is IOException or UnauthorizedAccessException or ArgumentException or NotSupportedException)
+        {
+            _report($"settings: save failed ({e.Message})");
+            try { File.Delete(temp); } catch (Exception) { } // best effort: don't leave the half-step behind
+        }
+    }
+}