checkoutservice: money proto migration

Signed-off-by: Ahmet Alp Balkan <ahmetb@google.com>

src/checkoutservice/genproto/demo.pb.go

@@ -35,7 +35,7 @@ func (m *CartItem) Reset()         { *m = CartItem{} }
 func (m *CartItem) String() string { return proto.CompactTextString(m) }
 func (*CartItem) ProtoMessage()    {}
 func (*CartItem) Descriptor() ([]byte, []int) {
-	return fileDescriptor_demo_40506d781b7ed975, []int{0}
+	return fileDescriptor_demo_be349a9cb1cf0a0c, []int{0}
 }
 func (m *CartItem) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_CartItem.Unmarshal(m, b)
@@ -81,7 +81,7 @@ func (m *AddItemRequest) Reset()         { *m = AddItemRequest{} }
 func (m *AddItemRequest) String() string { return proto.CompactTextString(m) }
 func (*AddItemRequest) ProtoMessage()    {}
 func (*AddItemRequest) Descriptor() ([]byte, []int) {
-	return fileDescriptor_demo_40506d781b7ed975, []int{1}
+	return fileDescriptor_demo_be349a9cb1cf0a0c, []int{1}
 }
 func (m *AddItemRequest) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_AddItemRequest.Unmarshal(m, b)
@@ -126,7 +126,7 @@ func (m *EmptyCartRequest) Reset()         { *m = EmptyCartRequest{} }
 func (m *EmptyCartRequest) String() string { return proto.CompactTextString(m) }
 func (*EmptyCartRequest) ProtoMessage()    {}
 func (*EmptyCartRequest) Descriptor() ([]byte, []int) {
-	return fileDescriptor_demo_40506d781b7ed975, []int{2}
+	return fileDescriptor_demo_be349a9cb1cf0a0c, []int{2}
 }
 func (m *EmptyCartRequest) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_EmptyCartRequest.Unmarshal(m, b)
@@ -164,7 +164,7 @@ func (m *GetCartRequest) Reset()         { *m = GetCartRequest{} }
 func (m *GetCartRequest) String() string { return proto.CompactTextString(m) }
 func (*GetCartRequest) ProtoMessage()    {}
 func (*GetCartRequest) Descriptor() ([]byte, []int) {
-	return fileDescriptor_demo_40506d781b7ed975, []int{3}
+	return fileDescriptor_demo_be349a9cb1cf0a0c, []int{3}
 }
 func (m *GetCartRequest) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_GetCartRequest.Unmarshal(m, b)
@@ -203,7 +203,7 @@ func (m *Cart) Reset()         { *m = Cart{} }
 func (m *Cart) String() string { return proto.CompactTextString(m) }
 func (*Cart) ProtoMessage()    {}
 func (*Cart) Descriptor() ([]byte, []int) {
-	return fileDescriptor_demo_40506d781b7ed975, []int{4}
+	return fileDescriptor_demo_be349a9cb1cf0a0c, []int{4}
 }
 func (m *Cart) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_Cart.Unmarshal(m, b)
@@ -247,7 +247,7 @@ func (m *Empty) Reset()         { *m = Empty{} }
 func (m *Empty) String() string { return proto.CompactTextString(m) }
 func (*Empty) ProtoMessage()    {}
 func (*Empty) Descriptor() ([]byte, []int) {
-	return fileDescriptor_demo_40506d781b7ed975, []int{5}
+	return fileDescriptor_demo_be349a9cb1cf0a0c, []int{5}
 }
 func (m *Empty) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_Empty.Unmarshal(m, b)
@@ -279,7 +279,7 @@ func (m *ListRecommendationsRequest) Reset()         { *m = ListRecommendationsR
 func (m *ListRecommendationsRequest) String() string { return proto.CompactTextString(m) }
 func (*ListRecommendationsRequest) ProtoMessage()    {}
 func (*ListRecommendationsRequest) Descriptor() ([]byte, []int) {
-	return fileDescriptor_demo_40506d781b7ed975, []int{6}
+	return fileDescriptor_demo_be349a9cb1cf0a0c, []int{6}
 }
 func (m *ListRecommendationsRequest) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_ListRecommendationsRequest.Unmarshal(m, b)
@@ -324,7 +324,7 @@ func (m *ListRecommendationsResponse) Reset()         { *m = ListRecommendations
 func (m *ListRecommendationsResponse) String() string { return proto.CompactTextString(m) }
 func (*ListRecommendationsResponse) ProtoMessage()    {}
 func (*ListRecommendationsResponse) Descriptor() ([]byte, []int) {
-	return fileDescriptor_demo_40506d781b7ed975, []int{7}
+	return fileDescriptor_demo_be349a9cb1cf0a0c, []int{7}
 }
 func (m *ListRecommendationsResponse) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_ListRecommendationsResponse.Unmarshal(m, b)
@@ -356,7 +356,7 @@ type Product struct {
 	Name                 string   `protobuf:"bytes,2,opt,name=name" json:"name,omitempty"`
 	Description          string   `protobuf:"bytes,3,opt,name=description" json:"description,omitempty"`
 	Picture              string   `protobuf:"bytes,4,opt,name=picture" json:"picture,omitempty"`
-	PriceUsd             *MoneyAmount `protobuf:"bytes,5,opt,name=price_usd,json=priceUsd" json:"price_usd,omitempty"`
+	PriceUsd             *Money   `protobuf:"bytes,5,opt,name=price_usd,json=priceUsd" json:"price_usd,omitempty"`
 	XXX_NoUnkeyedLiteral struct{} `json:"-"`
 	XXX_unrecognized     []byte   `json:"-"`
 	XXX_sizecache        int32    `json:"-"`
@@ -366,7 +366,7 @@ func (m *Product) Reset()         { *m = Product{} }
 func (m *Product) String() string { return proto.CompactTextString(m) }
 func (*Product) ProtoMessage()    {}
 func (*Product) Descriptor() ([]byte, []int) {
-	return fileDescriptor_demo_40506d781b7ed975, []int{8}
+	return fileDescriptor_demo_be349a9cb1cf0a0c, []int{8}
 }
 func (m *Product) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_Product.Unmarshal(m, b)
@@ -414,7 +414,7 @@ func (m *Product) GetPicture() string {
 	return ""
 }
 
-func (m *Product) GetPriceUsd() *MoneyAmount {
+func (m *Product) GetPriceUsd() *Money {
 	if m != nil {
 		return m.PriceUsd
 	}
@@ -432,7 +432,7 @@ func (m *ListProductsResponse) Reset()         { *m = ListProductsResponse{} }
 func (m *ListProductsResponse) String() string { return proto.CompactTextString(m) }
 func (*ListProductsResponse) ProtoMessage()    {}
 func (*ListProductsResponse) Descriptor() ([]byte, []int) {
-	return fileDescriptor_demo_40506d781b7ed975, []int{9}
+	return fileDescriptor_demo_be349a9cb1cf0a0c, []int{9}
 }
 func (m *ListProductsResponse) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_ListProductsResponse.Unmarshal(m, b)
@@ -470,7 +470,7 @@ func (m *GetProductRequest) Reset()         { *m = GetProductRequest{} }
 func (m *GetProductRequest) String() string { return proto.CompactTextString(m) }
 func (*GetProductRequest) ProtoMessage()    {}
 func (*GetProductRequest) Descriptor() ([]byte, []int) {
-	return fileDescriptor_demo_40506d781b7ed975, []int{10}
+	return fileDescriptor_demo_be349a9cb1cf0a0c, []int{10}
 }
 func (m *GetProductRequest) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_GetProductRequest.Unmarshal(m, b)
@@ -508,7 +508,7 @@ func (m *SearchProductsRequest) Reset()         { *m = SearchProductsRequest{} }
 func (m *SearchProductsRequest) String() string { return proto.CompactTextString(m) }
 func (*SearchProductsRequest) ProtoMessage()    {}
 func (*SearchProductsRequest) Descriptor() ([]byte, []int) {
-	return fileDescriptor_demo_40506d781b7ed975, []int{11}
+	return fileDescriptor_demo_be349a9cb1cf0a0c, []int{11}
 }
 func (m *SearchProductsRequest) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_SearchProductsRequest.Unmarshal(m, b)
@@ -546,7 +546,7 @@ func (m *SearchProductsResponse) Reset()         { *m = SearchProductsResponse{}
 func (m *SearchProductsResponse) String() string { return proto.CompactTextString(m) }
 func (*SearchProductsResponse) ProtoMessage()    {}
 func (*SearchProductsResponse) Descriptor() ([]byte, []int) {
-	return fileDescriptor_demo_40506d781b7ed975, []int{12}
+	return fileDescriptor_demo_be349a9cb1cf0a0c, []int{12}
 }
 func (m *SearchProductsResponse) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_SearchProductsResponse.Unmarshal(m, b)
@@ -585,7 +585,7 @@ func (m *GetQuoteRequest) Reset()         { *m = GetQuoteRequest{} }
 func (m *GetQuoteRequest) String() string { return proto.CompactTextString(m) }
 func (*GetQuoteRequest) ProtoMessage()    {}
 func (*GetQuoteRequest) Descriptor() ([]byte, []int) {
-	return fileDescriptor_demo_40506d781b7ed975, []int{13}
+	return fileDescriptor_demo_be349a9cb1cf0a0c, []int{13}
 }
 func (m *GetQuoteRequest) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_GetQuoteRequest.Unmarshal(m, b)
@@ -620,7 +620,7 @@ func (m *GetQuoteRequest) GetItems() []*CartItem {
 }
 
 type GetQuoteResponse struct {
-	CostUsd              *MoneyAmount `protobuf:"bytes,1,opt,name=cost_usd,json=costUsd" json:"cost_usd,omitempty"`
+	CostUsd              *Money   `protobuf:"bytes,1,opt,name=cost_usd,json=costUsd" json:"cost_usd,omitempty"`
 	XXX_NoUnkeyedLiteral struct{} `json:"-"`
 	XXX_unrecognized     []byte   `json:"-"`
 	XXX_sizecache        int32    `json:"-"`
@@ -630,7 +630,7 @@ func (m *GetQuoteResponse) Reset()         { *m = GetQuoteResponse{} }
 func (m *GetQuoteResponse) String() string { return proto.CompactTextString(m) }
 func (*GetQuoteResponse) ProtoMessage()    {}
 func (*GetQuoteResponse) Descriptor() ([]byte, []int) {
-	return fileDescriptor_demo_40506d781b7ed975, []int{14}
+	return fileDescriptor_demo_be349a9cb1cf0a0c, []int{14}
 }
 func (m *GetQuoteResponse) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_GetQuoteResponse.Unmarshal(m, b)
@@ -650,7 +650,7 @@ func (m *GetQuoteResponse) XXX_DiscardUnknown() {
 
 var xxx_messageInfo_GetQuoteResponse proto.InternalMessageInfo
 
-func (m *GetQuoteResponse) GetCostUsd() *MoneyAmount {
+func (m *GetQuoteResponse) GetCostUsd() *Money {
 	if m != nil {
 		return m.CostUsd
 	}
@@ -669,7 +669,7 @@ func (m *ShipOrderRequest) Reset()         { *m = ShipOrderRequest{} }
 func (m *ShipOrderRequest) String() string { return proto.CompactTextString(m) }
 func (*ShipOrderRequest) ProtoMessage()    {}
 func (*ShipOrderRequest) Descriptor() ([]byte, []int) {
-	return fileDescriptor_demo_40506d781b7ed975, []int{15}
+	return fileDescriptor_demo_be349a9cb1cf0a0c, []int{15}
 }
 func (m *ShipOrderRequest) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_ShipOrderRequest.Unmarshal(m, b)
@@ -714,7 +714,7 @@ func (m *ShipOrderResponse) Reset()         { *m = ShipOrderResponse{} }
 func (m *ShipOrderResponse) String() string { return proto.CompactTextString(m) }
 func (*ShipOrderResponse) ProtoMessage()    {}
 func (*ShipOrderResponse) Descriptor() ([]byte, []int) {
-	return fileDescriptor_demo_40506d781b7ed975, []int{16}
+	return fileDescriptor_demo_be349a9cb1cf0a0c, []int{16}
 }
 func (m *ShipOrderResponse) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_ShipOrderResponse.Unmarshal(m, b)
@@ -756,7 +756,7 @@ func (m *Address) Reset()         { *m = Address{} }
 func (m *Address) String() string { return proto.CompactTextString(m) }
 func (*Address) ProtoMessage()    {}
 func (*Address) Descriptor() ([]byte, []int) {
-	return fileDescriptor_demo_40506d781b7ed975, []int{17}
+	return fileDescriptor_demo_be349a9cb1cf0a0c, []int{17}
 }
 func (m *Address) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_Address.Unmarshal(m, b)
@@ -811,58 +811,20 @@ func (m *Address) GetZipCode() int32 {
 	return 0
 }
 
-// Describes a money amount without currency. For example, decimal=2 and
+// Represents an amount of money with its currency type.
-// fractional=500 (or fractional=5) makes up 2.5 units.
-type MoneyAmount struct {
-	Decimal              uint32   `protobuf:"varint,1,opt,name=decimal" json:"decimal,omitempty"`
-	Fractional           uint32   `protobuf:"varint,2,opt,name=fractional" json:"fractional,omitempty"`
-	XXX_NoUnkeyedLiteral struct{} `json:"-"`
-	XXX_unrecognized     []byte   `json:"-"`
-	XXX_sizecache        int32    `json:"-"`
-}
-
-func (m *MoneyAmount) Reset()         { *m = MoneyAmount{} }
-func (m *MoneyAmount) String() string { return proto.CompactTextString(m) }
-func (*MoneyAmount) ProtoMessage()    {}
-func (*MoneyAmount) Descriptor() ([]byte, []int) {
-	return fileDescriptor_demo_40506d781b7ed975, []int{18}
-}
-func (m *MoneyAmount) XXX_Unmarshal(b []byte) error {
-	return xxx_messageInfo_MoneyAmount.Unmarshal(m, b)
-}
-func (m *MoneyAmount) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
-	return xxx_messageInfo_MoneyAmount.Marshal(b, m, deterministic)
-}
-func (dst *MoneyAmount) XXX_Merge(src proto.Message) {
-	xxx_messageInfo_MoneyAmount.Merge(dst, src)
-}
-func (m *MoneyAmount) XXX_Size() int {
-	return xxx_messageInfo_MoneyAmount.Size(m)
-}
-func (m *MoneyAmount) XXX_DiscardUnknown() {
-	xxx_messageInfo_MoneyAmount.DiscardUnknown(m)
-}
-
-var xxx_messageInfo_MoneyAmount proto.InternalMessageInfo
-
-func (m *MoneyAmount) GetDecimal() uint32 {
-	if m != nil {
-		return m.Decimal
-	}
-	return 0
-}
-
-func (m *MoneyAmount) GetFractional() uint32 {
-	if m != nil {
-		return m.Fractional
-	}
-	return 0
-}
-
 type Money struct {
 	// The 3-letter currency code defined in ISO 4217.
 	CurrencyCode string `protobuf:"bytes,1,opt,name=currency_code,json=currencyCode" json:"currency_code,omitempty"`
-	Amount               *MoneyAmount `protobuf:"bytes,2,opt,name=amount" json:"amount,omitempty"`
+	// The whole units of the amount.
+	// For example if `currencyCode` is `"USD"`, then 1 unit is one US dollar.
+	Units int64 `protobuf:"varint,2,opt,name=units" json:"units,omitempty"`
+	// Number of nano (10^-9) units of the amount.
+	// The value must be between -999,999,999 and +999,999,999 inclusive.
+	// If `units` is positive, `nanos` must be positive or zero.
+	// If `units` is zero, `nanos` can be positive, zero, or negative.
+	// If `units` is negative, `nanos` must be negative or zero.
+	// For example $-1.75 is represented as `units`=-1 and `nanos`=-750,000,000.
+	Nanos                int32    `protobuf:"varint,3,opt,name=nanos" json:"nanos,omitempty"`
 	XXX_NoUnkeyedLiteral struct{} `json:"-"`
 	XXX_unrecognized     []byte   `json:"-"`
 	XXX_sizecache        int32    `json:"-"`
@@ -872,7 +834,7 @@ func (m *Money) Reset()         { *m = Money{} }
 func (m *Money) String() string { return proto.CompactTextString(m) }
 func (*Money) ProtoMessage()    {}
 func (*Money) Descriptor() ([]byte, []int) {
-	return fileDescriptor_demo_40506d781b7ed975, []int{19}
+	return fileDescriptor_demo_be349a9cb1cf0a0c, []int{18}
 }
 func (m *Money) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_Money.Unmarshal(m, b)
@@ -899,11 +861,18 @@ func (m *Money) GetCurrencyCode() string {
 	return ""
 }
 
-func (m *Money) GetAmount() *MoneyAmount {
+func (m *Money) GetUnits() int64 {
 	if m != nil {
-		return m.Amount
+		return m.Units
 	}
-	return nil
+	return 0
+}
+
+func (m *Money) GetNanos() int32 {
+	if m != nil {
+		return m.Nanos
+	}
+	return 0
 }
 
 type GetSupportedCurrenciesResponse struct {
@@ -918,7 +887,7 @@ func (m *GetSupportedCurrenciesResponse) Reset()         { *m = GetSupportedCurr
 func (m *GetSupportedCurrenciesResponse) String() string { return proto.CompactTextString(m) }
 func (*GetSupportedCurrenciesResponse) ProtoMessage()    {}
 func (*GetSupportedCurrenciesResponse) Descriptor() ([]byte, []int) {
-	return fileDescriptor_demo_40506d781b7ed975, []int{20}
+	return fileDescriptor_demo_be349a9cb1cf0a0c, []int{19}
 }
 func (m *GetSupportedCurrenciesResponse) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_GetSupportedCurrenciesResponse.Unmarshal(m, b)
@@ -958,7 +927,7 @@ func (m *CurrencyConversionRequest) Reset()         { *m = CurrencyConversionReq
 func (m *CurrencyConversionRequest) String() string { return proto.CompactTextString(m) }
 func (*CurrencyConversionRequest) ProtoMessage()    {}
 func (*CurrencyConversionRequest) Descriptor() ([]byte, []int) {
-	return fileDescriptor_demo_40506d781b7ed975, []int{21}
+	return fileDescriptor_demo_be349a9cb1cf0a0c, []int{20}
 }
 func (m *CurrencyConversionRequest) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_CurrencyConversionRequest.Unmarshal(m, b)
@@ -1006,7 +975,7 @@ func (m *CreditCardInfo) Reset()         { *m = CreditCardInfo{} }
 func (m *CreditCardInfo) String() string { return proto.CompactTextString(m) }
 func (*CreditCardInfo) ProtoMessage()    {}
 func (*CreditCardInfo) Descriptor() ([]byte, []int) {
-	return fileDescriptor_demo_40506d781b7ed975, []int{22}
+	return fileDescriptor_demo_be349a9cb1cf0a0c, []int{21}
 }
 func (m *CreditCardInfo) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_CreditCardInfo.Unmarshal(m, b)
@@ -1066,7 +1035,7 @@ func (m *ChargeRequest) Reset()         { *m = ChargeRequest{} }
 func (m *ChargeRequest) String() string { return proto.CompactTextString(m) }
 func (*ChargeRequest) ProtoMessage()    {}
 func (*ChargeRequest) Descriptor() ([]byte, []int) {
-	return fileDescriptor_demo_40506d781b7ed975, []int{23}
+	return fileDescriptor_demo_be349a9cb1cf0a0c, []int{22}
 }
 func (m *ChargeRequest) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_ChargeRequest.Unmarshal(m, b)
@@ -1111,7 +1080,7 @@ func (m *ChargeResponse) Reset()         { *m = ChargeResponse{} }
 func (m *ChargeResponse) String() string { return proto.CompactTextString(m) }
 func (*ChargeResponse) ProtoMessage()    {}
 func (*ChargeResponse) Descriptor() ([]byte, []int) {
-	return fileDescriptor_demo_40506d781b7ed975, []int{24}
+	return fileDescriptor_demo_be349a9cb1cf0a0c, []int{23}
 }
 func (m *ChargeResponse) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_ChargeResponse.Unmarshal(m, b)
@@ -1150,7 +1119,7 @@ func (m *OrderItem) Reset()         { *m = OrderItem{} }
 func (m *OrderItem) String() string { return proto.CompactTextString(m) }
 func (*OrderItem) ProtoMessage()    {}
 func (*OrderItem) Descriptor() ([]byte, []int) {
-	return fileDescriptor_demo_40506d781b7ed975, []int{25}
+	return fileDescriptor_demo_be349a9cb1cf0a0c, []int{24}
 }
 func (m *OrderItem) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_OrderItem.Unmarshal(m, b)
@@ -1199,7 +1168,7 @@ func (m *OrderResult) Reset()         { *m = OrderResult{} }
 func (m *OrderResult) String() string { return proto.CompactTextString(m) }
 func (*OrderResult) ProtoMessage()    {}
 func (*OrderResult) Descriptor() ([]byte, []int) {
-	return fileDescriptor_demo_40506d781b7ed975, []int{26}
+	return fileDescriptor_demo_be349a9cb1cf0a0c, []int{25}
 }
 func (m *OrderResult) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_OrderResult.Unmarshal(m, b)
@@ -1266,7 +1235,7 @@ func (m *SendOrderConfirmationRequest) Reset()         { *m = SendOrderConfirmat
 func (m *SendOrderConfirmationRequest) String() string { return proto.CompactTextString(m) }
 func (*SendOrderConfirmationRequest) ProtoMessage()    {}
 func (*SendOrderConfirmationRequest) Descriptor() ([]byte, []int) {
-	return fileDescriptor_demo_40506d781b7ed975, []int{27}
+	return fileDescriptor_demo_be349a9cb1cf0a0c, []int{26}
 }
 func (m *SendOrderConfirmationRequest) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_SendOrderConfirmationRequest.Unmarshal(m, b)
@@ -1313,7 +1282,7 @@ func (m *CreateOrderRequest) Reset()         { *m = CreateOrderRequest{} }
 func (m *CreateOrderRequest) String() string { return proto.CompactTextString(m) }
 func (*CreateOrderRequest) ProtoMessage()    {}
 func (*CreateOrderRequest) Descriptor() ([]byte, []int) {
-	return fileDescriptor_demo_40506d781b7ed975, []int{28}
+	return fileDescriptor_demo_be349a9cb1cf0a0c, []int{27}
 }
 func (m *CreateOrderRequest) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_CreateOrderRequest.Unmarshal(m, b)
@@ -1366,7 +1335,7 @@ func (m *CreateOrderResponse) Reset()         { *m = CreateOrderResponse{} }
 func (m *CreateOrderResponse) String() string { return proto.CompactTextString(m) }
 func (*CreateOrderResponse) ProtoMessage()    {}
 func (*CreateOrderResponse) Descriptor() ([]byte, []int) {
-	return fileDescriptor_demo_40506d781b7ed975, []int{29}
+	return fileDescriptor_demo_be349a9cb1cf0a0c, []int{28}
 }
 func (m *CreateOrderResponse) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_CreateOrderResponse.Unmarshal(m, b)
@@ -1415,7 +1384,7 @@ func (m *PlaceOrderRequest) Reset()         { *m = PlaceOrderRequest{} }
 func (m *PlaceOrderRequest) String() string { return proto.CompactTextString(m) }
 func (*PlaceOrderRequest) ProtoMessage()    {}
 func (*PlaceOrderRequest) Descriptor() ([]byte, []int) {
-	return fileDescriptor_demo_40506d781b7ed975, []int{30}
+	return fileDescriptor_demo_be349a9cb1cf0a0c, []int{29}
 }
 func (m *PlaceOrderRequest) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_PlaceOrderRequest.Unmarshal(m, b)
@@ -1481,7 +1450,7 @@ func (m *PlaceOrderResponse) Reset()         { *m = PlaceOrderResponse{} }
 func (m *PlaceOrderResponse) String() string { return proto.CompactTextString(m) }
 func (*PlaceOrderResponse) ProtoMessage()    {}
 func (*PlaceOrderResponse) Descriptor() ([]byte, []int) {
-	return fileDescriptor_demo_40506d781b7ed975, []int{31}
+	return fileDescriptor_demo_be349a9cb1cf0a0c, []int{30}
 }
 func (m *PlaceOrderResponse) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_PlaceOrderResponse.Unmarshal(m, b)
@@ -1527,7 +1496,6 @@ func init() {
 	proto.RegisterType((*ShipOrderRequest)(nil), "hipstershop.ShipOrderRequest")
 	proto.RegisterType((*ShipOrderResponse)(nil), "hipstershop.ShipOrderResponse")
 	proto.RegisterType((*Address)(nil), "hipstershop.Address")
-	proto.RegisterType((*MoneyAmount)(nil), "hipstershop.MoneyAmount")
 	proto.RegisterType((*Money)(nil), "hipstershop.Money")
 	proto.RegisterType((*GetSupportedCurrenciesResponse)(nil), "hipstershop.GetSupportedCurrenciesResponse")
 	proto.RegisterType((*CurrencyConversionRequest)(nil), "hipstershop.CurrencyConversionRequest")
@@ -2294,100 +2262,99 @@ var _CheckoutService_serviceDesc = grpc.ServiceDesc{
 	Metadata: "demo.proto",
 }
 
-func init() { proto.RegisterFile("demo.proto", fileDescriptor_demo_40506d781b7ed975) }
+func init() { proto.RegisterFile("demo.proto", fileDescriptor_demo_be349a9cb1cf0a0c) }
 
-var fileDescriptor_demo_40506d781b7ed975 = []byte{
+var fileDescriptor_demo_be349a9cb1cf0a0c = []byte{
-	// 1466 bytes of a gzipped FileDescriptorProto
+	// 1442 bytes of a gzipped FileDescriptorProto
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-	0x83, 0xb6, 0x2a, 0x14, 0xd1, 0x94, 0xf1, 0xbc, 0xf3, 0xf9, 0x32, 0x25, 0xd4, 0x10, 0xeb, 0x91,
+	0x94, 0x7c, 0xbe, 0xf6, 0x93, 0x6c, 0x42, 0x7a, 0xed, 0x49, 0xda, 0x03, 0xd0, 0x2d, 0xe8, 0xa4,
-	0x8d, 0x6e, 0xc0, 0x46, 0x38, 0x71, 0x82, 0x80, 0x57, 0x90, 0x6c, 0x29, 0x89, 0xa3, 0x09, 0xa9,
+	0x3b, 0x24, 0x9b, 0x85, 0x5a, 0x36, 0x2b, 0x1a, 0x38, 0xa0, 0x11, 0x47, 0x77, 0x60, 0x2d, 0xdd,
-	0xb3, 0xa7, 0x49, 0x49, 0x41, 0xb7, 0xa1, 0x93, 0xdc, 0x10, 0x6c, 0x16, 0x2b, 0xd9, 0xac, 0x28,
+	0xa8, 0x1b, 0xdb, 0xe2, 0x31, 0x8d, 0x6d, 0x55, 0xa3, 0x75, 0xc7, 0xb9, 0xa6, 0x1b, 0x5c, 0x43,
-	0xe0, 0xc0, 0x0f, 0x19, 0xba, 0x0b, 0x6b, 0xc9, 0x45, 0x55, 0x27, 0x97, 0x4e, 0xa8, 0x93, 0xab,
+	0x36, 0xb8, 0xb3, 0x85, 0x5d, 0x69, 0x40, 0x75, 0x87, 0x73, 0xe1, 0xfc, 0x01, 0x09, 0x5c, 0x39,
-	0x0a, 0xad, 0x0a, 0xd8, 0x75, 0x55, 0x2f, 0xeb, 0xa2, 0x5e, 0x9e, 0xcf, 0xdd, 0x4a, 0x0c, 0xaa,
+	0x3f, 0xa0, 0xc1, 0x4b, 0x8f, 0xf9, 0x32, 0x6d, 0x72, 0xaf, 0x10, 0xf1, 0x6d, 0xef, 0x50, 0xbf,
-	0x0a, 0xa6, 0x0d, 0x17, 0x0f, 0x89, 0x67, 0x8b, 0xfd, 0x81, 0xef, 0x1d, 0x39, 0xd4, 0x15, 0x61,
+	0x42, 0x72, 0x80, 0xf6, 0xa0, 0x21, 0x43, 0xa3, 0x62, 0xdc, 0x9b, 0xf5, 0x91, 0xc4, 0xd4, 0x4a,
-	0x93, 0x69, 0x6d, 0xc4, 0x35, 0x9d, 0xa9, 0x6a, 0x6d, 0x62, 0x81, 0xf6, 0xa1, 0x2e, 0x4c, 0x53,
+	0x60, 0xf8, 0x9d, 0x01, 0x68, 0xc0, 0x88, 0xcd, 0x49, 0xa1, 0x77, 0xd7, 0x2a, 0x90, 0x1d, 0xe8,
-	0x5a, 0x0f, 0x32, 0x36, 0x35, 0x62, 0x18, 0x7e, 0xa7, 0x01, 0x1a, 0x50, 0x62, 0x32, 0x92, 0x6b,
+	0xc8, 0x05, 0xdd, 0x0b, 0x54, 0xa0, 0x57, 0xc4, 0xa4, 0x6e, 0x07, 0xf9, 0xce, 0xbf, 0x70, 0x8a,
-	0x05, 0x95, 0xc3, 0xcd, 0x2e, 0x74, 0xc4, 0x81, 0xaa, 0x05, 0xd2, 0xd0, 0x2b, 0x7c, 0x53, 0x95,
+	0xce, 0x8f, 0x7f, 0x82, 0x33, 0x05, 0x0e, 0x2a, 0x1b, 0xd3, 0x78, 0x19, 0xa7, 0x88, 0xd7, 0xec,
-	0x83, 0x6c, 0x23, 0x59, 0x3c, 0x43, 0x23, 0xc1, 0x3f, 0xc1, 0xb9, 0x1c, 0x07, 0x19, 0x8d, 0x89,
+	0xbd, 0xce, 0x9f, 0xee, 0x5e, 0xf1, 0x5f, 0x06, 0xac, 0x3f, 0x3e, 0xb4, 0x9d, 0xff, 0x30, 0x02,
-	0xbd, 0xb4, 0x33, 0xd8, 0x6b, 0xde, 0xaf, 0xb5, 0xb3, 0xf9, 0x15, 0xff, 0xa5, 0xc1, 0xfa, 0x93,
+	0xd9, 0x65, 0x36, 0xf2, 0x97, 0x59, 0x2a, 0xef, 0xa5, 0xf7, 0x2b, 0xef, 0x7b, 0x80, 0xf2, 0xc7,
-	0xa9, 0x69, 0xfd, 0x87, 0x16, 0x48, 0x9d, 0x59, 0xcf, 0x3a, 0xb3, 0x90, 0xde, 0xcb, 0xef, 0x97,
+	0x4a, 0xc5, 0x88, 0x4a, 0x10, 0xe3, 0x54, 0x09, 0xd2, 0xff, 0xd3, 0x80, 0xb6, 0x28, 0xe3, 0x03,
-	0xde, 0xf7, 0x01, 0x65, 0x9f, 0x95, 0x4c, 0x38, 0x32, 0x40, 0xb4, 0x33, 0x05, 0x48, 0xff, 0x4f,
+	0xc2, 0x8e, 0x3c, 0x87, 0xa0, 0xdb, 0xf2, 0x05, 0x95, 0x95, 0xbf, 0x55, 0x3e, 0x53, 0x4e, 0xd4,
-	0x0d, 0xda, 0x3c, 0x8d, 0x0f, 0x09, 0x3d, 0x76, 0x2c, 0x82, 0xee, 0x88, 0x86, 0x2c, 0x32, 0x7f,
+	0x9b, 0xc5, 0xb8, 0x27, 0xaa, 0x77, 0x0e, 0x7d, 0x06, 0x4d, 0xa5, 0xbc, 0x4b, 0xbb, 0x8b, 0x7a,
-	0xab, 0xf8, 0xa6, 0xcc, 0xf7, 0x82, 0x9e, 0xb7, 0x7b, 0x3c, 0x50, 0x2f, 0xa0, 0xcf, 0xa0, 0x21,
+	0xdc, 0x5c, 0x9f, 0x69, 0x23, 0x78, 0x0e, 0x7d, 0x09, 0xad, 0x54, 0xe3, 0xa3, 0x0b, 0xb3, 0xf6,
-	0x87, 0xfa, 0xc2, 0xed, 0xfc, 0xa8, 0xaf, 0xaf, 0xcf, 0x95, 0x11, 0xbc, 0x80, 0xbe, 0x84, 0x56,
+	0xf3, 0x06, 0x2a, 0xdd, 0xf7, 0x7f, 0x36, 0x60, 0xb3, 0xa8, 0x8d, 0xf5, 0xb1, 0x7e, 0x80, 0x33,
-	0xf2, 0xf9, 0x80, 0x2e, 0xcd, 0xcb, 0xcf, 0x0a, 0x28, 0x55, 0xdf, 0xff, 0x59, 0x83, 0xcd, 0xfc,
+	0x15, 0xc2, 0x19, 0x7d, 0x58, 0x30, 0x53, 0x2f, 0xd9, 0xcd, 0xdd, 0x93, 0x81, 0xc9, 0x05, 0x08,
-	0xd8, 0xad, 0x9e, 0xf5, 0x03, 0x9c, 0x2b, 0x99, 0xc9, 0xd1, 0x87, 0x39, 0x31, 0xd5, 0x5f, 0x03,
+	0x16, 0xf3, 0xb0, 0xa9, 0x44, 0xdf, 0xc0, 0xe6, 0xf6, 0x21, 0x7d, 0xa5, 0x59, 0x0c, 0x61, 0x25,
-	0xfa, 0xde, 0xe9, 0xc0, 0xd8, 0x01, 0x9c, 0x45, 0x0d, 0x36, 0xe5, 0x24, 0x39, 0x30, 0x99, 0x39,
+	0xaf, 0x70, 0x51, 0xc5, 0x29, 0xcc, 0xff, 0xcf, 0x78, 0x2a, 0x0b, 0x4e, 0x3c, 0x87, 0xee, 0x01,
-	0xf5, 0x5f, 0x29, 0x16, 0x43, 0x58, 0xc9, 0x8e, 0xcd, 0xa8, 0xe4, 0x15, 0xfa, 0xff, 0xe7, 0x34,
+	0x64, 0x02, 0x17, 0x5d, 0x2c, 0x87, 0xba, 0xa8, 0x7c, 0xcd, 0x4a, 0x3d, 0x8a, 0xe7, 0xd0, 0x73,
-	0x15, 0xa7, 0x58, 0xbc, 0x80, 0xee, 0x03, 0xa4, 0x53, 0x33, 0xda, 0x2e, 0x9a, 0x3a, 0x3f, 0x4e,
+	0xe8, 0x16, 0x25, 0x2d, 0xc2, 0x05, 0x64, 0xa5, 0x3c, 0x36, 0x77, 0x8e, 0xc5, 0xa4, 0x51, 0xf8,
-	0xeb, 0xa5, 0x43, 0x2e, 0x5e, 0x40, 0xcf, 0xa1, 0x9b, 0x9f, 0x93, 0x11, 0xce, 0x21, 0x4b, 0x67,
+	0xcd, 0x80, 0xd5, 0x03, 0x55, 0x87, 0xfa, 0xfc, 0x23, 0x58, 0xd6, 0x4a, 0x14, 0x9d, 0x2f, 0x93,
-	0x6e, 0x7d, 0xf7, 0x44, 0x4c, 0x62, 0x85, 0xdf, 0x34, 0x58, 0x3d, 0x94, 0x79, 0xa8, 0xde, 0x3f,
+	0xce, 0x0b, 0x62, 0xf3, 0x42, 0xcd, 0x6a, 0x1a, 0x81, 0x07, 0xd0, 0x4a, 0x05, 0x62, 0x29, 0x59,
-	0x82, 0xa6, 0x1a, 0x6f, 0xd1, 0xc5, 0x22, 0xe9, 0xec, 0x94, 0xad, 0x5f, 0xaa, 0x38, 0x4d, 0x2c,
+	0xca, 0x4a, 0xd5, 0xbc, 0x58, 0xb7, 0x9c, 0x92, 0xfd, 0xc3, 0x80, 0x55, 0x5d, 0xdc, 0x9a, 0xec,
-	0xf0, 0x10, 0x5a, 0xc9, 0xbc, 0x59, 0x08, 0x96, 0xe2, 0xe0, 0xab, 0x6f, 0x57, 0x1d, 0x27, 0x64,
+	0x73, 0x38, 0x5b, 0xad, 0xa4, 0x2a, 0xaf, 0xed, 0x6a, 0x99, 0xf0, 0x31, 0x12, 0x0c, 0xcf, 0xa1,
-	0xff, 0xd0, 0x60, 0x55, 0x25, 0xb7, 0x22, 0xfb, 0x1c, 0xce, 0x97, 0x4f, 0x52, 0xa5, 0x6e, 0xbb,
+	0x21, 0x34, 0x13, 0x55, 0xc5, 0xd1, 0xe5, 0x62, 0x2d, 0xd4, 0x69, 0x2e, 0xb3, 0xa2, 0xd3, 0xe1,
-	0x56, 0x24, 0x7c, 0xc2, 0x08, 0x86, 0x17, 0xd0, 0x10, 0x1a, 0xf1, 0x54, 0xc5, 0xd0, 0x95, 0x7c,
+	0xb9, 0xfe, 0x53, 0xe8, 0x3e, 0xb6, 0xa7, 0x3e, 0x09, 0xd2, 0x0a, 0x1e, 0xc0, 0x52, 0xf2, 0xec,
-	0x2e, 0x54, 0xcd, 0x5c, 0x7a, 0x49, 0xa5, 0xc3, 0x0b, 0xfd, 0x67, 0xd0, 0x7d, 0x62, 0xce, 0x5c,
+	0x23, 0xb3, 0x68, 0x39, 0x2f, 0x43, 0xcc, 0xad, 0xca, 0xb5, 0x34, 0x20, 0x13, 0x58, 0xd9, 0x17,
-	0xe2, 0x25, 0x19, 0x3c, 0x80, 0xe5, 0xb8, 0xed, 0x23, 0x3d, 0x2f, 0x39, 0x3b, 0x86, 0xe8, 0x5b,
+	0x3d, 0x4a, 0x1b, 0x7d, 0x26, 0x7e, 0x2c, 0x55, 0xbc, 0x56, 0xe8, 0x4a, 0x29, 0x1b, 0xea, 0x5f,
-	0xa5, 0x67, 0x89, 0x41, 0x26, 0xb0, 0x72, 0xc0, 0x6b, 0x94, 0x12, 0xfa, 0x2d, 0xff, 0x02, 0x2b,
+	0xb4, 0x9a, 0x9a, 0xfd, 0x5d, 0x84, 0x7e, 0x42, 0x9c, 0xd7, 0x34, 0x4e, 0x8f, 0x60, 0x41, 0x3b,
-	0xe9, 0x56, 0xe8, 0x6a, 0x21, 0x1a, 0xaa, 0x3b, 0x5a, 0x45, 0xce, 0xfe, 0xce, 0x4d, 0x3f, 0x21,
+	0xf7, 0x60, 0xa0, 0x4b, 0xe5, 0x96, 0x58, 0x7a, 0xce, 0xcc, 0xed, 0x7a, 0x40, 0x1a, 0xf1, 0x47,
-	0xd6, 0x6b, 0x3f, 0x4a, 0x9e, 0x60, 0x40, 0x3b, 0xd3, 0x30, 0xd0, 0xe5, 0x62, 0x49, 0x2c, 0xb4,
+	0x00, 0x59, 0xbb, 0x2c, 0x95, 0xcc, 0xcc, 0xf3, 0x60, 0x5e, 0xaa, 0x5d, 0xd7, 0x06, 0x5f, 0x2c,
-	0x33, 0x7d, 0xa7, 0x1a, 0x90, 0x58, 0xfc, 0x31, 0x40, 0x5a, 0x2e, 0x0b, 0x29, 0x33, 0xd7, 0x1e,
+	0xc9, 0xff, 0x50, 0x3e, 0xf9, 0x27, 0x00, 0x00, 0xff, 0xff, 0x67, 0x70, 0xff, 0x79, 0x51, 0x11,
-	0xf4, 0xcb, 0x95, 0xe7, 0x4a, 0xe0, 0xcb, 0x65, 0xf1, 0xf7, 0xcc, 0xad, 0x7f, 0x02, 0x00, 0x00,
+	0x00, 0x00,
-	0xff, 0xff, 0xdd, 0xe8, 0xfb, 0x77, 0xac, 0x11, 0x00, 0x00,
 }

src/checkoutservice/main.go

@@ -13,6 +13,7 @@ import (
 	"google.golang.org/grpc/status"
 
 	pb "./genproto"
+	money "./money"
 )
 
 const (
@@ -71,10 +72,7 @@ func (cs *checkoutService) CreateOrder(ctx context.Context, req *pb.CreateOrderR
 	if err != nil {
 		return nil, status.Errorf(codes.Internal, "shipping quote failure: %+v", err)
 	}
-	resp.ShippingCost = &pb.Money{
+	resp.ShippingCost = shippingQuoteUSD
-		Amount:       shippingQuoteUSD,
-		CurrencyCode: "USD",
-	}
 	// TODO(ahmetb) convert to req.UserCurrency
 	// TODO(ahmetb) calculate resp.OrderItem with req.UserCurrency
 	return resp, nil
@@ -102,20 +100,20 @@ func (cs *checkoutService) PlaceOrder(ctx context.Context, req *pb.PlaceOrderReq
 	if err != nil {
 		return nil, status.Errorf(codes.Internal, "shipping quote failure: %+v", err)
 	}
-	shippingPrice, err := cs.convertCurrency(ctx, &pb.Money{
+	shippingPrice, err := cs.convertCurrency(ctx, shippingUsd, req.UserCurrency)
-		Amount:       shippingUsd,
-		CurrencyCode: usdCurrency}, req.UserCurrency)
 	if err != nil {
 		return nil, status.Errorf(codes.Internal, "failed to convert shipping cost to currency: %+v", err)
 	}
 
-	var totalPrice pb.Money
+	total := pb.Money{CurrencyCode: req.UserCurrency,
-	totalPrice = sumMoney(totalPrice, *shippingPrice)
+		Units: 0,
+		Nanos: 0}
+	total = money.Must(money.Sum(total, *shippingPrice))
 	for _, it := range orderItems {
-		totalPrice = sumMoney(totalPrice, *it.Cost)
+		total = money.Must(money.Sum(total, *it.Cost))
 	}
 
-	txID, err := cs.chargeCard(ctx, &totalPrice, req.CreditCard)
+	txID, err := cs.chargeCard(ctx, &total, req.CreditCard)
 	if err != nil {
 		return nil, status.Errorf(codes.Internal, "failed to charge card: %+v", err)
 	}
@@ -143,7 +141,7 @@ func (cs *checkoutService) PlaceOrder(ctx context.Context, req *pb.PlaceOrderReq
 	return resp, nil
 }
 
-func (cs *checkoutService) quoteShipping(ctx context.Context, address *pb.Address, items []*pb.CartItem) (*pb.MoneyAmount, error) {
+func (cs *checkoutService) quoteShipping(ctx context.Context, address *pb.Address, items []*pb.CartItem) (*pb.Money, error) {
 	conn, err := grpc.DialContext(ctx, cs.shippingSvcAddr, grpc.WithInsecure())
 	if err != nil {
 		return nil, fmt.Errorf("could not connect shipping service: %+v", err)
@@ -189,10 +187,7 @@ func (cs *checkoutService) prepOrderItems(ctx context.Context, items []*pb.CartI
 		if err != nil {
 			return nil, fmt.Errorf("failed to get product #%q", item.GetProductId())
 		}
-		usdPrice := &pb.Money{
+		price, err := cs.convertCurrency(ctx, product.GetPriceUsd(), userCurrency)
-			Amount:       product.GetPriceUsd(),
-			CurrencyCode: usdCurrency}
-		price, err := cs.convertCurrency(ctx, usdPrice, userCurrency)
 		if err != nil {
 			return nil, fmt.Errorf("failed to convert price of %q to %s", item.GetProductId(), userCurrency)
 		}

src/checkoutservice/money.go

@@ -1,44 +0,0 @@
-package main
-
-import (
-	"math"
-
-	pb "./genproto"
-)
-
-func sum(m1, m2 pb.MoneyAmount) pb.MoneyAmount {
-	f1, f2 := float64(m1.Fractional), float64(m2.Fractional)
-	lg1 := math.Max(1, math.Ceil(math.Log10(f1)))
-	if f1 == math.Pow(10, lg1) {
-		lg1++
-	}
-	lg2 := math.Max(1, math.Ceil(math.Log10(f2)))
-	if f2 == math.Pow(10, lg2) {
-		lg2++
-	}
-	lgMax := math.Max(lg1, lg2)
-
-	dSum := m1.Decimal + m2.Decimal
-	o1 := f1 * math.Pow(10, lgMax-lg1)
-	o2 := f2 * math.Pow(10, lgMax-lg2)
-	fSum := o1 + o2
-	if fSum >= math.Pow(10, lgMax) {
-		fSum -= math.Pow(10, lgMax)
-		dSum++
-	}
-
-	for int(fSum)%10 == 0 && fSum != 0 {
-		fSum = float64(int(fSum) / 10)
-	}
-
-	return pb.MoneyAmount{
-		Decimal:    dSum,
-		Fractional: uint32(fSum)}
-}
-
-func sumMoney(m1, m2 pb.Money) pb.Money {
-	s := sum(*m1.Amount, *m2.Amount)
-	return pb.Money{
-		Amount:       &s,
-		CurrencyCode: m1.CurrencyCode}
-}

src/checkoutservice/money/money.go

@@ -0,0 +1,118 @@
+package money
+
+import (
+	"errors"
+
+	pb "../genproto"
+)
+
+const (
+	nanosMin = -999999999
+	nanosMax = +999999999
+	nanosMod = 1000000000
+)
+
+var (
+	ErrInvalidValue        = errors.New("one of the specified money values is invalid")
+	ErrMismatchingCurrency = errors.New("mismatching currency codes")
+)
+
+// IsValid checks if specified value has a valid units/nanos signs and ranges.
+func IsValid(m pb.Money) bool {
+	return signMatches(m) && validNanos(m.GetNanos())
+}
+
+func signMatches(m pb.Money) bool {
+	return m.GetNanos() == 0 || m.GetUnits() == 0 || (m.GetNanos() < 0) == (m.GetUnits() < 0)
+}
+
+func validNanos(nanos int32) bool { return nanosMin <= nanos && nanos <= nanosMax }
+
+// IsZero returns true if the specified money value is equal to zero.
+func IsZero(m pb.Money) bool { return m.GetUnits() == 0 && m.GetNanos() == 0 }
+
+// IsPositive returns true if the specified money value is valid and is
+// positive.
+func IsPositive(m pb.Money) bool {
+	return IsValid(m) && m.GetUnits() > 0 || (m.GetUnits() == 0 && m.GetNanos() > 0)
+}
+
+// IsNegative returns true if the specified money value is valid and is
+// negative.
+func IsNegative(m pb.Money) bool {
+	return IsValid(m) && m.GetUnits() < 0 || (m.GetUnits() == 0 && m.GetNanos() < 0)
+}
+
+// AreSameCurrency returns true if values l and r have a currency code and
+// they are the same values.
+func AreSameCurrency(l, r pb.Money) bool {
+	return l.GetCurrencyCode() == r.GetCurrencyCode() && l.GetCurrencyCode() != ""
+}
+
+// AreEquals returns true if values l and r are the equal, including the
+// currency. This does not check validity of the provided values.
+func AreEquals(l, r pb.Money) bool {
+	return l.GetCurrencyCode() == r.GetCurrencyCode() &&
+		l.GetUnits() == r.GetUnits() && l.GetNanos() == r.GetNanos()
+}
+
+// Negate returns the same amount with the sign negated.
+func Negate(m pb.Money) pb.Money {
+	return pb.Money{
+		Units:        -m.GetUnits(),
+		Nanos:        -m.GetNanos(),
+		CurrencyCode: m.GetCurrencyCode()}
+}
+
+// Must panics if the given error is not nil. This can be used with other
+// functions like: "m := Must(Sum(a,b))".
+func Must(v pb.Money, err error) pb.Money {
+	if err != nil {
+		panic(err)
+	}
+	return v
+}
+
+// Sum adds two values. Returns an error if one of the values are invalid or
+// currency codes are not matching (unless currency code is unspecified for
+// both).
+func Sum(l, r pb.Money) (pb.Money, error) {
+	if !IsValid(l) || !IsValid(r) {
+		return pb.Money{}, ErrInvalidValue
+	} else if l.GetCurrencyCode() != r.GetCurrencyCode() {
+		return pb.Money{}, ErrMismatchingCurrency
+	}
+	units := l.GetUnits() + r.GetUnits()
+	nanos := l.GetNanos() + r.GetNanos()
+
+	if (units == 0 && nanos == 0) || (units > 0 && nanos >= 0) || (units < 0 && nanos <= 0) {
+		// same sign <units, nanos>
+		units += int64(nanos / nanosMod)
+		nanos = nanos % nanosMod
+	} else {
+		// different sign. nanos guaranteed to not to go over the limit
+		if units > 0 {
+			units--
+			nanos += nanosMod
+		} else {
+			units++
+			nanos -= nanosMod
+		}
+	}
+
+	return pb.Money{
+		Units:        units,
+		Nanos:        nanos,
+		CurrencyCode: l.GetCurrencyCode()}, nil
+}
+
+// MultiplySlow is a slow multiplication operation done through adding the value
+// to itself n-1 times.
+func MultiplySlow(m pb.Money, n uint32) pb.Money {
+	out := m
+	for n > 1 {
+		out = Must(Sum(out, m))
+		n--
+	}
+	return out
+}

src/checkoutservice/money/money_test.go

@@ -0,0 +1,231 @@
+package money
+
+import (
+	"fmt"
+	"reflect"
+	"testing"
+
+	pb "../genproto"
+)
+
+func mmc(u int64, n int32, c string) pb.Money { return pb.Money{Units: u, Nanos: n, CurrencyCode: c} }
+func mm(u int64, n int32) pb.Money            { return mmc(u, n, "") }
+
+func TestIsValid(t *testing.T) {
+	tests := []struct {
+		name string
+		in   pb.Money
+		want bool
+	}{
+		{"valid -/-", mm(-981273891273, -999999999), true},
+		{"invalid -/+", mm(-981273891273, +999999999), false},
+		{"valid +/+", mm(981273891273, 999999999), true},
+		{"invalid +/-", mm(981273891273, -999999999), false},
+		{"invalid +/+overflow", mm(3, 1000000000), false},
+		{"invalid +/-overflow", mm(3, -1000000000), false},
+		{"invalid -/+overflow", mm(-3, 1000000000), false},
+		{"invalid -/-overflow", mm(-3, -1000000000), false},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := IsValid(tt.in); got != tt.want {
+				t.Errorf("IsValid(%v) = %v, want %v", tt.in, got, tt.want)
+			}
+		})
+	}
+}
+
+func TestIsZero(t *testing.T) {
+	tests := []struct {
+		name string
+		in   pb.Money
+		want bool
+	}{
+		{"zero", mm(0, 0), true},
+		{"not-zero (-/+)", mm(-1, +1), false},
+		{"not-zero (-/-)", mm(-1, -1), false},
+		{"not-zero (+/+)", mm(+1, +1), false},
+		{"not-zero (+/-)", mm(+1, -1), false},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := IsZero(tt.in); got != tt.want {
+				t.Errorf("IsZero(%v) = %v, want %v", tt.in, got, tt.want)
+			}
+		})
+	}
+}
+
+func TestIsPositive(t *testing.T) {
+	tests := []struct {
+		name string
+		in   pb.Money
+		want bool
+	}{
+		{"zero", mm(0, 0), false},
+		{"positive (+/+)", mm(+1, +1), true},
+		{"invalid (-/+)", mm(-1, +1), false},
+		{"negative (-/-)", mm(-1, -1), false},
+		{"invalid (+/-)", mm(+1, -1), false},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := IsPositive(tt.in); got != tt.want {
+				t.Errorf("IsPositive(%v) = %v, want %v", tt.in, got, tt.want)
+			}
+		})
+	}
+}
+
+func TestIsNegative(t *testing.T) {
+	tests := []struct {
+		name string
+		in   pb.Money
+		want bool
+	}{
+		{"zero", mm(0, 0), false},
+		{"positive (+/+)", mm(+1, +1), false},
+		{"invalid (-/+)", mm(-1, +1), false},
+		{"negative (-/-)", mm(-1, -1), true},
+		{"invalid (+/-)", mm(+1, -1), false},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := IsNegative(tt.in); got != tt.want {
+				t.Errorf("IsNegative(%v) = %v, want %v", tt.in, got, tt.want)
+			}
+		})
+	}
+}
+
+func TestAreSameCurrency(t *testing.T) {
+	type args struct {
+		l pb.Money
+		r pb.Money
+	}
+	tests := []struct {
+		name string
+		args args
+		want bool
+	}{
+		{"both empty currency", args{mmc(1, 0, ""), mmc(2, 0, "")}, false},
+		{"left empty currency", args{mmc(1, 0, ""), mmc(2, 0, "USD")}, false},
+		{"right empty currency", args{mmc(1, 0, "USD"), mmc(2, 0, "")}, false},
+		{"mismatching", args{mmc(1, 0, "USD"), mmc(2, 0, "CAD")}, false},
+		{"matching", args{mmc(1, 0, "USD"), mmc(2, 0, "USD")}, true},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := AreSameCurrency(tt.args.l, tt.args.r); got != tt.want {
+				t.Errorf("AreSameCurrency([%v],[%v]) = %v, want %v", tt.args.l, tt.args.r, got, tt.want)
+			}
+		})
+	}
+}
+
+func TestAreEquals(t *testing.T) {
+	type args struct {
+		l pb.Money
+		r pb.Money
+	}
+	tests := []struct {
+		name string
+		args args
+		want bool
+	}{
+		{"equals", args{mmc(1, 2, "USD"), mmc(1, 2, "USD")}, true},
+		{"mismatching currency", args{mmc(1, 2, "USD"), mmc(1, 2, "CAD")}, false},
+		{"mismatching units", args{mmc(10, 20, "USD"), mmc(1, 20, "USD")}, false},
+		{"mismatching nanos", args{mmc(1, 2, "USD"), mmc(1, 20, "USD")}, false},
+		{"negated", args{mmc(1, 2, "USD"), mmc(-1, -2, "USD")}, false},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := AreEquals(tt.args.l, tt.args.r); got != tt.want {
+				t.Errorf("AreEquals([%v],[%v]) = %v, want %v", tt.args.l, tt.args.r, got, tt.want)
+			}
+		})
+	}
+}
+
+func TestNegate(t *testing.T) {
+	tests := []struct {
+		name string
+		in   pb.Money
+		want pb.Money
+	}{
+		{"zero", mm(0, 0), mm(0, 0)},
+		{"negative", mm(-1, -200), mm(1, 200)},
+		{"positive", mm(1, 200), mm(-1, -200)},
+		{"carries currency code", mmc(0, 0, "XXX"), mmc(0, 0, "XXX")},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := Negate(tt.in); !AreEquals(got, tt.want) {
+				t.Errorf("Negate([%v]) = %v, want %v", tt.in, got, tt.want)
+			}
+		})
+	}
+}
+
+func TestMust_pass(t *testing.T) {
+	v := Must(mm(2, 3), nil)
+	if !AreEquals(v, mm(2, 3)) {
+		t.Errorf("returned the wrong value: %v", v)
+	}
+}
+
+func TestMust_panic(t *testing.T) {
+	defer func() {
+		if r := recover(); r != nil {
+			t.Logf("panic captured: %v", r)
+		}
+	}()
+	Must(mm(2, 3), fmt.Errorf("some error"))
+	t.Fatal("this should not have executed due to the panic above")
+}
+
+func TestSum(t *testing.T) {
+	type args struct {
+		l pb.Money
+		r pb.Money
+	}
+	tests := []struct {
+		name    string
+		args    args
+		want    pb.Money
+		wantErr error
+	}{
+		{"0+0=0", args{mm(0, 0), mm(0, 0)}, mm(0, 0), nil},
+		{"Error: currency code on left", args{mmc(0, 0, "XXX"), mm(0, 0)}, mm(0, 0), ErrMismatchingCurrency},
+		{"Error: currency code on right", args{mm(0, 0), mmc(0, 0, "YYY")}, mm(0, 0), ErrMismatchingCurrency},
+		{"Error: currency code mismatch", args{mmc(0, 0, "AAA"), mmc(0, 0, "BBB")}, mm(0, 0), ErrMismatchingCurrency},
+		{"Error: invalid +/-", args{mm(+1, -1), mm(0, 0)}, mm(0, 0), ErrInvalidValue},
+		{"Error: invalid -/+", args{mm(0, 0), mm(-1, +2)}, mm(0, 0), ErrInvalidValue},
+		{"Error: invalid nanos", args{mm(0, 1000000000), mm(1, 0)}, mm(0, 0), ErrInvalidValue},
+		{"both positive (no carry)", args{mm(2, 200000000), mm(2, 200000000)}, mm(4, 400000000), nil},
+		{"both positive (nanos=max)", args{mm(2, 111111111), mm(2, 888888888)}, mm(4, 999999999), nil},
+		{"both positive (carry)", args{mm(2, 200000000), mm(2, 900000000)}, mm(5, 100000000), nil},
+		{"both negative (no carry)", args{mm(-2, -200000000), mm(-2, -200000000)}, mm(-4, -400000000), nil},
+		{"both negative (carry)", args{mm(-2, -200000000), mm(-2, -900000000)}, mm(-5, -100000000), nil},
+		{"mixed (larger positive, just decimals)", args{mm(11, 0), mm(-2, 0)}, mm(9, 0), nil},
+		{"mixed (larger negative, just decimals)", args{mm(-11, 0), mm(2, 0)}, mm(-9, 0), nil},
+		{"mixed (larger positive, no borrow)", args{mm(11, 100000000), mm(-2, -100000000)}, mm(9, 0), nil},
+		{"mixed (larger positive, with borrow)", args{mm(11, 100000000), mm(-2, -9000000 /*.09*/)}, mm(9, 91000000 /*.091*/), nil},
+		{"mixed (larger negative, no borrow)", args{mm(-11, -100000000), mm(2, 100000000)}, mm(-9, 0), nil},
+		{"mixed (larger negative, with borrow)", args{mm(-11, -100000000), mm(2, 9000000 /*.09*/)}, mm(-9, -91000000 /*.091*/), nil},
+		{"0+negative", args{mm(0, 0), mm(-2, -100000000)}, mm(-2, -100000000), nil},
+		{"negative+0", args{mm(-2, -100000000), mm(0, 0)}, mm(-2, -100000000), nil},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := Sum(tt.args.l, tt.args.r)
+			if err != tt.wantErr {
+				t.Errorf("Sum([%v],[%v]): expected err=\"%v\" got=\"%v\"", tt.args.l, tt.args.r, tt.wantErr, err)
+			}
+			if !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("Sum([%v],[%v]) = %v, want %v", tt.args.l, tt.args.r, got, tt.want)
+			}
+		})
+	}
+}

src/checkoutservice/money_test.go

@@ -1,53 +0,0 @@
-package main
-
-import (
-	"reflect"
-	"testing"
-
-	pb "./genproto"
-)
-
-func Test_sum(t *testing.T) {
-	type args struct {
-		m1 pb.MoneyAmount
-		m2 pb.MoneyAmount
-	}
-	tests := []struct {
-		name string
-		args args
-		want pb.MoneyAmount
-	}{
-		{
-			name: "no fractions",
-			args: args{pb.MoneyAmount{Decimal: 10}, pb.MoneyAmount{Decimal: 100}},
-			want: pb.MoneyAmount{Decimal: 110},
-		},
-		{
-			name: "same fraction digits",
-			args: args{pb.MoneyAmount{Decimal: 1, Fractional: 23}, pb.MoneyAmount{Decimal: 1, Fractional: 44}},
-			want: pb.MoneyAmount{Decimal: 2, Fractional: 67},
-		},
-		{
-			name: "different fraction digits",
-			args: args{pb.MoneyAmount{Decimal: 1, Fractional: 351}, pb.MoneyAmount{Decimal: 1, Fractional: 1}},
-			want: pb.MoneyAmount{Decimal: 2, Fractional: 451},
-		},
-		{
-			name: "redundant trailing zeroes are removed from fraction",
-			args: args{pb.MoneyAmount{Decimal: 1, Fractional: 351}, pb.MoneyAmount{Decimal: 1, Fractional: 349}},
-			want: pb.MoneyAmount{Decimal: 2, Fractional: 7},
-		},
-		{
-			name: "carry",
-			args: args{pb.MoneyAmount{Decimal: 1, Fractional: 5}, pb.MoneyAmount{Decimal: 1, Fractional: 5000000}},
-			want: pb.MoneyAmount{Decimal: 3},
-		},
-	}
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			if got := sum(tt.args.m1, tt.args.m2); !reflect.DeepEqual(got, tt.want) {
-				t.Errorf("sum(%v+%v) = %v, want=%v", tt.args.m1, tt.args.m2, got, tt.want)
-			}
-		})
-	}
-}