satellite/payments: available coupon value feature

Change-Id: Ieae9385fbd917230298afff91a6be2838ad9b313

satellite/console/billinghistoryitem.go

@@ -12,6 +12,7 @@ type BillingHistoryItem struct {
 	ID          string                 `json:"id"`
 	Description string                 `json:"description"`
 	Amount      int64                  `json:"amount"`
+	Remaining   int64                  `json:"remaining"`
 	Received    int64                  `json:"received"`
 	Status      string                 `json:"status"`
 	Link        string                 `json:"link"`

satellite/console/service.go

@@ -299,11 +299,22 @@ func (paymentService PaymentsService) BillingHistory(ctx context.Context) (billi
 	}
 
 	for _, coupon := range coupons {
+		alreadyUsed, err := paymentService.service.accounts.Coupons().TotalUsage(ctx, coupon.ID)
+		if err != nil {
+			return nil, Error.Wrap(err)
+		}
+
+		remaining := coupon.Amount - alreadyUsed
+		if coupon.Status == payments.CouponExpired {
+			remaining = 0
+		}
+
 		billingHistory = append(billingHistory,
 			&BillingHistoryItem{
 				ID:          coupon.ID.String(),
 				Description: coupon.Description,
 				Amount:      coupon.Amount,
+				Remaining:   remaining,
 				Status:      "Added to balance",
 				Link:        "",
 				Start:       coupon.Created,

satellite/payments/coupons.go

@@ -18,6 +18,9 @@ type Coupons interface {
 	// ListByUserID return list of all coupons of specified payment account.
 	ListByUserID(ctx context.Context, userID uuid.UUID) ([]Coupon, error)
 
+	// TotalUsage returns sum of all usage records for specified coupon.
+	TotalUsage(ctx context.Context, couponID uuid.UUID) (int64, error)
+
 	// Create attaches a coupon for payment account.
 	Create(ctx context.Context, coupon Coupon) (coup Coupon, err error)
 

satellite/payments/stripecoinpayments/coupons.go

@@ -106,6 +106,15 @@ func (coupons *coupons) ListByUserID(ctx context.Context, userID uuid.UUID) (_ [
 	return couponList, Error.Wrap(err)
 }
 
+// TotalUsage returns sum of all usage records for specified coupon.
+func (coupons *coupons) TotalUsage(ctx context.Context, couponID uuid.UUID) (_ int64, err error) {
+	defer mon.Task()(&ctx, couponID)(&err)
+
+	totalUsage, err := coupons.service.db.Coupons().TotalUsage(ctx, couponID)
+
+	return totalUsage, Error.Wrap(err)
+}
+
 // PopulatePromotionalCoupons is used to populate promotional coupons through all active users who already have
 // a project, payment method and do not have a promotional coupon yet.
 // And updates project limits to selected size.