payment-poc/stripe/service.go

package stripe

import (
	"github.com/gin-gonic/gin"
	"github.com/google/uuid"
	"github.com/stripe/stripe-go/v72"
	"github.com/stripe/stripe-go/v72/checkout/session"
	"github.com/stripe/stripe-go/v72/paymentintent"
	"log"
	"payment-poc/database"
	"payment-poc/state"
)

type Service struct {
	ApiKey     string
	BackendUrl string
}

func (s *Service) UpdatePayment(entry database.PaymentEntry) (updatedEntry database.PaymentEntry, err error) {
	pi, err := paymentintent.Get(*entry.PaymentIntentId, nil)
	if err != nil {
		return entry, err
	}
	newState := determineState(pi.Status)

	if entry.State != newState && newState != "" {
		log.Printf("Updated state for %s: %s -> %s", entry.Id.String(), entry.State, newState)
		if pi.AmountReceived > 0 {
			entry.Amount = &pi.AmountReceived
		}
		entry.State = newState
	}
	return entry, nil
}

func determineState(status stripe.PaymentIntentStatus) state.PaymentState {
	switch status {
	case stripe.PaymentIntentStatusCanceled:
		return state.StateCanceled
	case stripe.PaymentIntentStatusProcessing:
		return state.StatePending
	case stripe.PaymentIntentStatusRequiresAction:
		return state.StatePending
	case stripe.PaymentIntentStatusRequiresCapture:
		return state.StateAccepted
	case stripe.PaymentIntentStatusRequiresConfirmation:
		return state.StatePending
	case stripe.PaymentIntentStatusRequiresPaymentMethod:
		return state.StateVoided
	case stripe.PaymentIntentStatusSucceeded:
		return state.StateCompleted
	}
	return ""
}

func (s *Service) CreatePaymentUrl(entry database.PaymentEntry) (database.PaymentEntry, string, error) {
	entry, url, err := s.InitializePayment(entry)
	if err != nil {
		return entry, "", err
	}
	return entry, url, nil
}

func (s *Service) InitializePayment(entry database.PaymentEntry) (database.PaymentEntry, string, error) {

	currency := string(stripe.CurrencyEUR)
	productName := "Example product"
	productDescription := "Simple example product"

	params := &stripe.CheckoutSessionParams{
		LineItems: []*stripe.CheckoutSessionLineItemParams{
			{
				PriceData: &stripe.CheckoutSessionLineItemPriceDataParams{
					Currency: &currency,
					ProductData: &stripe.CheckoutSessionLineItemPriceDataProductDataParams{
						Name:        &productName,
						Description: &productDescription,
					},
					UnitAmount: &entry.TotalAmount,
				},
				Quantity: stripe.Int64(1),
			},
		},
		Mode: stripe.String(string(stripe.CheckoutSessionModePayment)),
		PaymentIntentData: &stripe.CheckoutSessionPaymentIntentDataParams{
			CaptureMethod: stripe.String("manual"),
		},
		SuccessURL: stripe.String(s.BackendUrl + "/stripe/success?token=" + entry.Id.String()),
		CancelURL:  stripe.String(s.BackendUrl + "/stripe/cancel?token=" + entry.Id.String()),
	}
	result, err := session.New(params)
	if err != nil {
		return database.PaymentEntry{}, "", err
	}
	entry.State = state.StateInitialized
	entry.PaymentIntentId = &result.PaymentIntent.ID

	return entry, result.URL, nil
}

func (s *Service) CompleteTransaction(entry database.PaymentEntry, amount int64) (database.PaymentEntry, error) {
	params := &stripe.PaymentIntentCaptureParams{
		AmountToCapture: stripe.Int64(amount),
	}
	pi, err := paymentintent.Capture(*entry.PaymentIntentId, params)
	if err != nil {
		return database.PaymentEntry{}, err
	}
	log.Printf("received state on completion: %v", pi.Status)
	newState := determineState(pi.Status)
	entry.State = newState
	if newState == state.StateCompleted || newState == state.StatePending {
		entry.Amount = &pi.AmountReceived
	}
	return entry, nil
}

func (s *Service) CancelTransaction(entry database.PaymentEntry) (database.PaymentEntry, error) {
	params := &stripe.PaymentIntentCancelParams{}
	pi, err := paymentintent.Cancel(*entry.PaymentIntentId, params)
	if err != nil {
		return database.PaymentEntry{}, err
	}
	log.Printf("received state on completion: %v", pi.Status)
	if pi.Status == stripe.PaymentIntentStatusCanceled {
		entry.State = state.StateCanceled
	}
	return entry, nil
}

func (s *Service) HandleResponse(c *gin.Context, provider *database.PaymentEntryProvider, paymentState state.PaymentState) (string, error) {
	id := uuid.MustParse(c.Query("token"))
	entry, err := provider.FetchById(id)
	if err != nil {
		return "", err
	}
	entry.State = paymentState
	provider.UpdateEntry(entry)
	return "/entries/" + entry.Id.String(), nil
}