1 files changed, 27 insertions, 0 deletions
diff --git a/src/Godosa.Core/Diagnostics/PerfCsv.cs b/src/Godosa.Core/Diagnostics/PerfCsv.cs
new file mode 100644
index 0000000..6c4ef0d
--- /dev/null
+++ b/src/Godosa.Core/Diagnostics/PerfCsv.cs
@@ -0,0 +1,27 @@
+using System.Globalization;
+
+namespace Godosa.Core.Diagnostics;
+
+/// <summary>Per-frame CSV rows for perf-log stall hunts. Fixed columns first, then the
+/// caller's own (<see cref="Header"/> names, <see cref="Row"/> values, same order).
+/// Invariant culture; times in ms with 3 decimals; blank = unknown (e.g. GPU before a
+/// timer query reports).</summary>
+public static class PerfCsv
+{
+    public const string BaseHeader = "t_s,frame_ms,work_ms,sim_ticks,sim_ms,gpu_ms";
+
+    public static string Header(params string[] extraColumns) =>
+        extraColumns.Length == 0 ? BaseHeader : BaseHeader + "," + string.Join(',', extraColumns);
+
+    public static string Row(double timeSeconds, double frameSeconds, double workSeconds, int simTicks,
+        double simSeconds, double? gpuSeconds, params string[] extraValues)
+    {
+        string row = string.Create(CultureInfo.InvariantCulture,
+            $"{timeSeconds:F3},{frameSeconds * 1000:F3},{workSeconds * 1000:F3},{simTicks},{simSeconds * 1000:F3},{Ms(gpuSeconds)}");
+        return extraValues.Length == 0 ? row : row + "," + string.Join(',', extraValues);
+    }
+
+    /// <summary>Seconds → ms with 3 decimals (invariant); blank for null.</summary>
+    public static string Ms(double? seconds) =>
+        seconds is { } s ? (s * 1000).ToString("F3", CultureInfo.InvariantCulture) : "";
+}