[#1983] Implement CurrencyValue.ConvertUsingProtobufDef

Author: placer14

core/order.go

@@ -1019,7 +1019,7 @@ func (n *OpenBazaarNode) CalculateOrderTotal(contract *pb.RicardianContract) (*b
 			return big.NewInt(0), fmt.Errorf("preparing reserve currency converter: %s", err.Error())
 		}
 
-		finalItemAmount, err := itemOriginAmt.ConvertUsingProtobufDef(v5Order.Payment.AmountCurrency, cc)
+		finalItemAmount, _, err := itemOriginAmt.ConvertUsingProtobufDef(v5Order.Payment.AmountCurrency, cc)
 		if err != nil {
 			return big.NewInt(0), err
 		}
@@ -1104,7 +1104,7 @@ func (n *OpenBazaarNode) calculateShippingTotalForListings(contract *pb.Ricardia
 		if err != nil {
 			return big.NewInt(0), fmt.Errorf("parsing service price (%v): %s", service.Name, err.Error())
 		}
-		convertedShippingPrice, err := servicePrice.ConvertUsingProtobufDef(v5Order.Payment.AmountCurrency, cc)
+		convertedShippingPrice, _, err := servicePrice.ConvertUsingProtobufDef(v5Order.Payment.AmountCurrency, cc)
 		if err != nil {
 			return big.NewInt(0), fmt.Errorf("converting service price (%s): %s", service.Name, err.Error())
 		}
@@ -1115,7 +1115,7 @@ func (n *OpenBazaarNode) calculateShippingTotalForListings(contract *pb.Ricardia
 		}
 		var convertedAuxPrice = repo.NewCurrencyValueFromBigInt(big.NewInt(0), convertedShippingPrice.Currency)
 		if auxServicePrice.IsPositive() {
-			finalAux, err := auxServicePrice.ConvertUsingProtobufDef(v5Order.Payment.AmountCurrency, cc)
+			finalAux, _, err := auxServicePrice.ConvertUsingProtobufDef(v5Order.Payment.AmountCurrency, cc)
 			if err != nil {
 				return big.NewInt(0), fmt.Errorf("converting aux service price (%s): %s", service.Name, err.Error())
 			}

repo/currency.go

@@ -243,8 +243,14 @@ func (c *CurrencyValue) ConvertTo(final CurrencyDefinition, reserveConverter *Cu
 // target currency. If the divisibility provided by the pb.CurrencyDefinition is different
 // than the one provided for the exchange rate, the converted amount will be adjusted to
 // match the provided divisibility.
-func (c *CurrencyValue) ConvertUsingProtobufDef(convertTo *pb.CurrencyDefinition, reserve *CurrencyConverter) (*CurrencyValue, error) {
-	return c, nil
+func (c *CurrencyValue) ConvertUsingProtobufDef(convertTo *pb.CurrencyDefinition, reserve *CurrencyConverter) (*CurrencyValue, big.Accuracy, error) {
+	var repoCurrencyDef CurrencyDefinition
+	if c, err := AllCurrencies().Lookup(convertTo.Code); err != nil {
+		repoCurrencyDef = c
+	} else {
+		repoCurrencyDef = NewUnknownCryptoDefinition(convertTo.Code, uint(convertTo.Divisibility))
+	}
+	return c.ConvertTo(repoCurrencyDef, reserve)
 }
 
 // Cmp exposes the (*big.Int).Cmp behavior after verifying currency and adjusting

repo/currency_test.go

@@ -5,6 +5,7 @@ import (
 	"strings"
 	"testing"
 
+	"github.com/OpenBazaar/openbazaar-go/pb"
 	"github.com/OpenBazaar/openbazaar-go/repo"
 	"github.com/OpenBazaar/openbazaar-go/test/factory"
 )
@@ -456,6 +457,43 @@ func TestCurrencyValuesConvertCorrectly(t *testing.T) {
 	}
 }
 
+func TestConvertUsingProtobufDef(t *testing.T) {
+	subject := factory.MustNewCurrencyValue("10", "USD")
+	subject.Currency.Divisibility = 2
+	conv, err := factory.NewCurrencyConverter("BTC", map[string]float64{
+		"USD": 2,
+		"BCH": 0.5,
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	convertTo := &pb.CurrencyDefinition{
+		Code:         "TBCH",
+		Divisibility: 8,
+	}
+	expected := &repo.CurrencyValue{
+		Amount: big.NewInt(2500000), // 10 * (1/2 BTC/USD) * (1/2 BCH/BTC) * 1000000 (divisibility)
+		Currency: repo.CurrencyDefinition{
+			Code:         "TBCH",
+			CurrencyType: repo.Crypto,
+			Divisibility: 8,
+		},
+	}
+
+	cv, acc, err := subject.ConvertUsingProtobufDef(convertTo, conv)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if acc != big.Exact {
+		t.Errorf("expected result to be exact, but was (%s)", acc.String())
+	}
+
+	if !cv.Equal(expected) {
+		t.Errorf("expected result amount to be (%v), but was (%v)", expected, cv)
+	}
+}
+
 func TestNewCurrencyValueWithLookup(t *testing.T) {
 	_, err := repo.NewCurrencyValueWithLookup("0", "")
 	if err == nil {