price marchalling

pkg/cart/price.go

@@ -87,6 +87,34 @@ func (p Price) MarshalJSON() ([]byte, error) {
 	return json.Marshal(wire{ExVat: exVat, IncVat: p.IncVat, Vat: vat})
 }
 
+func (p *Price) UnmarshalJSON(data []byte) error {
+	type wire struct {
+		ExVat  int64            `json:"exVat"`
+		IncVat int64            `json:"incVat"`
+		Vat    map[string]int64 `json:"vat,omitempty"`
+	}
+	var w wire
+	if err := json.Unmarshal(data, &w); err != nil {
+		return err
+	}
+
+	p.IncVat = w.IncVat
+	if len(w.Vat) > 0 {
+		p.VatRates = make(map[float32]int64, len(w.Vat))
+		for rateStr, amount := range w.Vat {
+			rate, err := strconv.ParseFloat(rateStr, 32)
+			if err != nil {
+				return err
+			}
+			p.VatRates[float32(rate)] = amount
+		}
+	} else {
+		p.VatRates = make(map[float32]int64)
+	}
+
+	return nil
+}
+
 // trimFloat converts a float32 tax rate like 25 or 12.5 into a compact string without
 // unnecessary decimals ("25", "12.5").
 func trimFloat(f float32) string {