feat(stripe): ivoice sync quantity

openmeter/app/stripe/entity/app/calculator.go

@@ -4,6 +4,9 @@ import (
 	"fmt"
 
 	"github.com/alpacahq/alpacadecimal"
+	"github.com/invopop/gobl/num"
+	"golang.org/x/text/language"
+	"golang.org/x/text/message"
 
 	"github.com/openmeterio/openmeter/pkg/currencyx"
 )
@@ -17,17 +20,45 @@ func NewStripeCalculator(currency currencyx.Code) (StripeCalculator, error) {
 
 	return StripeCalculator{
 		calculator: calculator,
+		printer:    message.NewPrinter(language.English),
 		multiplier: alpacadecimal.NewFromInt(10).Pow(alpacadecimal.NewFromInt(int64(calculator.Def.Subunits))),
 	}, nil
 }
 
 // StripeCalculator provides a currency calculator object.
 type StripeCalculator struct {
 	calculator currencyx.Calculator
+	printer    *message.Printer
 	multiplier alpacadecimal.Decimal
 }
 
 // RoundToAmount rounds the amount to the precision of the Stripe currency in Stripe amount.
 func (c StripeCalculator) RoundToAmount(amount alpacadecimal.Decimal) int64 {
 	return amount.Mul(c.multiplier).Round(0).IntPart()
 }
+
+// FormatAmount formats the amount
+func (c StripeCalculator) FormatAmount(amount alpacadecimal.Decimal) string {
+	if amount.IsInteger() {
+		return c.calculator.Def.FormatAmount(num.MakeAmount(amount.IntPart(), 0))
+	}
+
+	am, _ := amount.Float64()
+	return c.calculator.Def.FormatAmount(num.AmountFromFloat64(am, uint32(amount.NumDigits())))
+}
+
+// FormatQuantity formats the quantity to two decimal places.
+// This should be only used to display the quantity not for calculations.
+func (c StripeCalculator) FormatQuantity(quantity alpacadecimal.Decimal) string {
+	if quantity.IsInteger() {
+		return c.printer.Sprintf("%d", quantity.IntPart())
+	} else {
+		f, _ := quantity.Float64()
+		return c.printer.Sprintf("%.2f", f)
+	}
+}
+
+// IsInteger checks if the amount is an integer in the Stripe currency.
+func (c StripeCalculator) IsInteger(amount alpacadecimal.Decimal) bool {
+	return amount.Mul(c.multiplier).IsInteger()
+}

openmeter/app/stripe/entity/app/invoice.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"sort"
 
+	"github.com/alpacahq/alpacadecimal"
 	"github.com/samber/lo"
 	"github.com/stripe/stripe-go/v80"
 
@@ -457,9 +458,8 @@ func getStripeUpdateLinesLineParams(
 
 // getStripeAddLinesLineParams returns the Stripe line item
 func getStripeAddLinesLineParams(line *billing.Line, calculator StripeCalculator) *stripe.InvoiceAddLinesLineParams {
-	name := getLineName(line)
+	description := getLineName(line)
 	period := getPeriod(line)
-
 	amount := line.Totals.Amount
 
 	// Handle usage based commitments like minimum spend
@@ -469,9 +469,19 @@ func getStripeAddLinesLineParams(line *billing.Line, calculator StripeCalculator
 		amount = line.Totals.ChargesTotal
 	}
 
+	// If the line has a quantity we add the quantity and per unit amount to the description
+	if line.FlatFee.Quantity.GreaterThan(alpacadecimal.NewFromInt(1)) {
+		description = fmt.Sprintf(
+			"%s (%s x %s)",
+			description,
+			calculator.FormatQuantity(line.FlatFee.Quantity),
+			calculator.FormatAmount(line.FlatFee.PerUnitAmount),
+		)
+	}
+
 	// Otherwise we add the calculated total with with quantity one
 	return &stripe.InvoiceAddLinesLineParams{
-		Description: lo.ToPtr(name),
+		Description: lo.ToPtr(description),
 		Amount:      lo.ToPtr(calculator.RoundToAmount(amount)),
 		Period:      period,
 		Metadata: map[string]string{