all the refactor

pkg/promotions/evaluate.go

@@ -1,6 +1,7 @@
 package promotions
 
 import (
+	"math"
 	"time"
 
 	"git.k6n.net/mats/go-cart-actor/pkg/cart"
@@ -77,7 +78,9 @@ func (req EvaluateRequest) toCart(tp cart.TaxProvider) *cart.CartGrain {
 		if qty == 0 {
 			qty = 1
 		}
-		vat := it.VatRate
+		// it.VatRate is the request rate in raw percent (external input); convert
+		// to the platform basis-point scale at this boundary.
+		vat := int(math.Round(float64(it.VatRate) * 100))
 		if vat == 0 {
 			vat = defaultVatRate(tp)
 		}
@@ -102,13 +105,13 @@ func (req EvaluateRequest) toCart(tp cart.TaxProvider) *cart.CartGrain {
 	return g
 }
 
-// defaultVatRate returns the default VAT rate (as a float32 for NewPriceFromIncVat)
-// from the provider, or 25 if none is configured.
-func defaultVatRate(tp cart.TaxProvider) float32 {
+// defaultVatRate returns the default VAT rate in basis points (2500 = 25%) from
+// the provider, or 2500 if none is configured.
+func defaultVatRate(tp cart.TaxProvider) int {
 	if tp == nil {
-		return 25
+		return 2500
 	}
-	return float32(tp.DefaultTaxRate(""))
+	return tp.DefaultTaxRate("")
 }
 
 // contextOptions maps the optional customer/time fields onto context options.