godosa-engine: initial public history

1 files changed, 21 insertions, 0 deletions

diff --git a/src/Godosa.Core/Input/MenuCursor.cs b/src/Godosa.Core/Input/MenuCursor.cs
new file mode 100644
index 0000000..be6cab3
--- /dev/null
+++ b/src/Godosa.Core/Input/MenuCursor.cs
@@ -0,0 +1,21 @@
+namespace Godosa.Core.Input;
+
+/// <summary>Which action a gamepad highlights in an open window (hud spec §4): wraps at the
+/// ends, stays inside a list that shrinks, −1 when there's nothing to pick.</summary>
+public sealed class MenuCursor
+{
+    public int Index { get; private set; } = -1;
+
+    public void Clamp(int count)
+    {
+        if (count <= 0) Index = -1;
+        else if (Index < 0) Index = 0;
+        else if (Index >= count) Index = count - 1;
+    }
+
+    public void Move(int delta, int count)
+    {
+        if (count <= 0) return;
+        Index = ((Index + delta) % count + count) % count;
+    }
+}