cart and checkout

pkg/promotions/evaluate.go

@@ -52,7 +52,7 @@ type EvaluateResponse struct {
 // Evaluate runs rules against a synthetic cart built from req and returns the
 // resulting totals and effects without touching any real cart state.
 func (s *PromotionService) Evaluate(rules []PromotionRule, req EvaluateRequest) EvaluateResponse {
-	g := req.toCart()
+	g := req.toCart(s.DefaultTaxProvider)
 	g.UpdateTotals()
 	ctx := NewContextFromCart(g, req.contextOptions()...)
 	results, _ := s.EvaluateAll(rules, ctx)
@@ -65,7 +65,8 @@ func (s *PromotionService) Evaluate(rules []PromotionRule, req EvaluateRequest)
 }
 
 // toCart materialises the request into a throwaway CartGrain.
-func (req EvaluateRequest) toCart() *cart.CartGrain {
+// tp is an optional TaxProvider for the default VAT rate; when nil, falls back to 25 %.
+func (req EvaluateRequest) toCart(tp cart.TaxProvider) *cart.CartGrain {
 	now := time.Now()
 	if req.Now != nil {
 		now = *req.Now
@@ -78,7 +79,7 @@ func (req EvaluateRequest) toCart() *cart.CartGrain {
 		}
 		vat := it.VatRate
 		if vat == 0 {
-			vat = 25
+			vat = defaultVatRate(tp)
 		}
 		item := &cart.CartItem{
 			Sku:      it.Sku,
@@ -91,15 +92,25 @@ func (req EvaluateRequest) toCart() *cart.CartGrain {
 		g.Items = append(g.Items, item)
 	}
 	if len(g.Items) == 0 && req.CartTotalIncVat > 0 {
+		vat := defaultVatRate(tp)
 		g.Items = append(g.Items, &cart.CartItem{
 			Sku:      "synthetic",
 			Quantity: 1,
-			Price:    *cart.NewPriceFromIncVat(req.CartTotalIncVat, 25),
+			Price:    *cart.NewPriceFromIncVat(req.CartTotalIncVat, vat),
 		})
 	}
 	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 {
+	if tp == nil {
+		return 25
+	}
+	return float32(tp.DefaultTaxRate(""))
+}
+
 // contextOptions maps the optional customer/time fields onto context options.
 func (req EvaluateRequest) contextOptions() []ContextOption {
 	var opts []ContextOption