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pkg/checkout/checkout-grain.go

@@ -87,24 +87,25 @@ type ConfirmationStatus struct {
 }
 
 type CheckoutGrain struct {
-	mu                sync.RWMutex
-	lastDeliveryId    uint32
-	lastGiftcardId    uint32
-	lastAccess        time.Time
-	lastChange        time.Time
-	Version           uint32              `json:"version"`
-	Id                CheckoutId          `json:"id"`
-	CartId            cart.CartId         `json:"cartId"`
-	CartVersion       uint64              `json:"cartVersion"`
-	CartState         *cart.CartGrain     `json:"cartState"` // snapshot of items
-	CartTotalPrice    *cart.Price         `json:"cartTotalPrice"`
-	OrderId           *string             `json:"orderId"`
-	Deliveries        []*CheckoutDelivery `json:"deliveries,omitempty"`
-	PaymentInProgress uint16              `json:"paymentInProgress"`
-	InventoryReserved bool                `json:"inventoryReserved"`
-	Confirmation      *ConfirmationStatus `json:"confirmationViewed,omitempty"`
-	Payments          []*Payment          `json:"payments,omitempty"`
-	ContactDetails    *ContactDetails     `json:"contactDetails,omitempty"`
+	mu                     sync.RWMutex
+	lastDeliveryId         uint32
+	lastGiftcardId         uint32
+	lastAccess             time.Time
+	lastChange             time.Time
+	Version                uint32              `json:"version"`
+	Id                     CheckoutId          `json:"id"`
+	CartId                 cart.CartId         `json:"cartId"`
+	CartVersion            uint64              `json:"cartVersion"`
+	CartState              *cart.CartGrain     `json:"cartState"` // snapshot of items
+	CartTotalPrice         *cart.Price         `json:"cartTotalPrice"`
+	OrderId                *string             `json:"orderId"`
+	Deliveries             []*CheckoutDelivery `json:"deliveries,omitempty"`
+	PaymentInProgress      uint16              `json:"paymentInProgress"`
+	AmountInCentsRemaining int64               `json:"amountRemaining"`
+	InventoryReserved      bool                `json:"inventoryReserved"`
+	Confirmation           *ConfirmationStatus `json:"confirmationViewed,omitempty"`
+	Payments               []*Payment          `json:"payments,omitempty"`
+	ContactDetails         *ContactDetails     `json:"contactDetails,omitempty"`
 }
 
 func NewCheckoutGrain(id uint64, cartId cart.CartId, cartVersion uint64, ts time.Time, cartState *cart.CartGrain) *CheckoutGrain {

pkg/checkout/mutation_initialize_checkout.go

@@ -47,6 +47,7 @@ func HandleInitializeCheckout(g *CheckoutGrain, m *messages.InitializeCheckout)
 	}
 
 	g.CartTotalPrice = g.CartState.TotalPrice
+	g.AmountInCentsRemaining = g.CartTotalPrice.IncVat
 
 	return nil
 }

pkg/checkout/mutation_payment_completed.go

@@ -36,6 +36,12 @@ func HandlePaymentCompleted(g *CheckoutGrain, m *messages.PaymentCompleted) erro
 
 	// Update checkout status
 	g.PaymentInProgress--
+	sum := g.CartState.TotalPrice.IncVat
+
+	for _, payment := range g.SettledPayments() {
+		sum -= payment.Amount
+	}
+	g.AmountInCentsRemaining = sum
 
 	return nil
 }