// Hook: BeforeCalculation
// Stamp a hidden "_Meta" sheet with generation context.
//
// Readers who open the file later can look at this sheet to see when the
// workbook was refreshed and which department it was generated for. The
// metadata is in place before calculation, so any formulas can reference it.

var meta = Workbook.Worksheets["_Meta"];
if (meta == null)
{
    AddWarning("Metadata sheet '_Meta' not found - skipping stamp.");
    return;
}

meta.Cells["A1"].PutValue("Generated by ReportWORQ");
meta.Cells["B1"].PutValue($"{DateTime.Now:yyyy-MM-dd HH:mm:ss}");

if (Parameters.TryGetValue("Department", out var dept))
    meta.Cells["C1"].PutValue(dept);

meta.AutoFitColumns();
Logger.LogInformation($"Stamped generation metadata for '{OutputName}'.");