try new vouchers

cmd/cart/cart-grain.go

@@ -8,6 +8,7 @@ import (
 	"time"
 
 	messages "git.tornberg.me/go-cart-actor/pkg/messages"
+	"git.tornberg.me/go-cart-actor/pkg/voucher"
 )
 
 // Legacy padded [16]byte CartId and its helper methods removed.
@@ -86,7 +87,55 @@ type Voucher struct {
 	Code  string                  `json:"code"`
 	Rules []*messages.VoucherRule `json:"rules"`
 	Id    uint32                  `json:"id"`
-	Value Price                   `json:"value"`
+	Value int64                   `json:"value"`
+}
+
+func (v *Voucher) AppliesTo(cart *CartGrain) ([]*CartItem, bool) {
+	// No rules -> applies to entire cart
+	if len(v.Rules) == 0 {
+		return cart.Items, true
+	}
+
+	// Build evaluation context once
+	ctx := voucher.EvalContext{
+		Items:        make([]voucher.Item, 0, len(cart.Items)),
+		CartTotalInc: 0,
+	}
+
+	if cart.TotalPrice != nil {
+		ctx.CartTotalInc = cart.TotalPrice.IncVat
+	}
+
+	for _, it := range cart.Items {
+		category := ""
+		if it.Meta != nil {
+			category = it.Meta.Category
+		}
+		ctx.Items = append(ctx.Items, voucher.Item{
+			Sku:       it.Sku,
+			Category:  category,
+			UnitPrice: it.Price.IncVat,
+		})
+	}
+
+	// All voucher rules must pass (logical AND)
+	for _, rule := range v.Rules {
+		expr := rule.GetCondition()
+		if expr == "" {
+			// Empty condition treated as pass (acts like a comment / placeholder)
+			continue
+		}
+		rs, err := voucher.ParseRules(expr)
+		if err != nil {
+			// Fail closed on parse error
+			return nil, false
+		}
+		if !rs.Applies(ctx) {
+			return nil, false
+		}
+	}
+
+	return cart.Items, true
 }
 
 func (c *CartGrain) GetId() uint64 {
@@ -208,9 +257,11 @@ func (c *CartGrain) UpdateTotals() {
 	for _, delivery := range c.Deliveries {
 		c.TotalPrice.Add(delivery.Price)
 	}
-	// for _, voucher := range c.Vouchers {
-	// 	c.TotalPrice -= voucher.Value
-	// 	c.TotalTax -= voucher.TaxValue
-	// 	c.TotalDiscountTax += voucher.TaxValue
-	// }
+	for _, voucher := range c.Vouchers {
+		if _, ok := voucher.AppliesTo(c); ok {
+			value := NewPriceFromIncVat(voucher.Value, 25)
+
+			c.TotalDiscount.Add(*value)
+		}
+	}
 }