cart and checkout

pkg/promotions/mcp/mcp.go

@@ -133,6 +133,15 @@ func (s *Server) initialize(params json.RawMessage) map[string]any {
 	}
 }
 
+// defaultVatRate returns the default VAT rate from the eval service's
+// configured tax provider, falling back to 25 if none is set.
+func (s *Server) defaultVatRate() float32 {
+	if s.eval == nil || s.eval.DefaultTaxProvider == nil {
+		return 25
+	}
+	return float32(s.eval.DefaultTaxProvider.DefaultTaxRate(""))
+}
+
 func isBatch(body []byte) bool {
 	for _, b := range body {
 		switch b {

pkg/promotions/mcp/public.go

@@ -86,7 +86,7 @@ func (s *Server) buildPublicTools() []tool {
 				if err := decode(args, &a); err != nil {
 					return nil, err
 				}
-				g := syntheticCart(a.CartTotalIncVat, a.ItemQuantity)
+				g := syntheticCart(a.CartTotalIncVat, a.ItemQuantity, s.defaultVatRate())
 				opts := []promotions.ContextOption{promotions.WithNow(time.Now())}
 				if a.CustomerSegment != "" {
 					opts = append(opts, promotions.WithCustomerSegment(a.CustomerSegment))
@@ -141,7 +141,7 @@ func (s *Server) buildPublicTools() []tool {
 					rules = filtered
 				}
 
-				g := syntheticCart(a.CartTotalIncVat, a.ItemQuantity)
+				g := syntheticCart(a.CartTotalIncVat, a.ItemQuantity, s.defaultVatRate())
 				opts := []promotions.ContextOption{promotions.WithNow(time.Now())}
 				if a.CustomerSegment != "" {
 					opts = append(opts, promotions.WithCustomerSegment(a.CustomerSegment))

pkg/promotions/mcp/tools.go

@@ -190,7 +190,7 @@ func (s *Server) buildTools() []tool {
 				if err := decode(args, &a); err != nil {
 					return nil, err
 				}
-				g := syntheticCart(a.CartTotalIncVat, a.ItemQuantity)
+				g := syntheticCart(a.CartTotalIncVat, a.ItemQuantity, s.defaultVatRate())
 				opts := []promotions.ContextOption{promotions.WithNow(time.Now())}
 				if a.CustomerSegment != "" {
 					opts = append(opts, promotions.WithCustomerSegment(a.CustomerSegment))
@@ -210,15 +210,19 @@ func (s *Server) buildTools() []tool {
 	}
 }
 
-// syntheticCart builds a one-line cart whose gross total is incVat öre (25% VAT
-// assumed) so the promotion engine can be evaluated against an arbitrary total.
-func syntheticCart(incVat int64, qty int) *cart.CartGrain {
+// syntheticCart builds a one-line cart whose gross total is incVat ore so the
+// promotion engine can be evaluated against an arbitrary total. defaultVatRate
+// is the VAT rate as a float32 percentage (e.g. 25 = 25 %).
+func syntheticCart(incVat int64, qty int, defaultVatRate float32) *cart.CartGrain {
 	if qty <= 0 {
 		qty = 1
 	}
+	if defaultVatRate == 0 {
+		defaultVatRate = 25
+	}
 	g := cart.NewCartGrain(0, time.Now())
 	g.Items = []*cart.CartItem{
-		{Id: 1, Sku: "PREVIEW", Quantity: uint16(qty), Price: *cart.NewPriceFromIncVat(incVat, 25)},
+		{Id: 1, Sku: "PREVIEW", Quantity: uint16(qty), Price: *cart.NewPriceFromIncVat(incVat, defaultVatRate)},
 	}
 	// Quantity > 1 would multiply the row total; keep the gross equal to incVat by
 	// pricing a single unit at the full total.