Payment Gateway Integration

Dokumentasi lengkap integrasi payment gateway di MStore Backend dengan support multi-provider (Xendit & Midtrans).

🎯 Overview

Sistem payment gateway MStore mendukung:

✅ Multi-Provider: Xendit (primary), Midtrans (secondary)
✅ Multi-Channel: QRIS, E-Wallet, Virtual Account, Credit Card
✅ Webhook Integration: Real-time payment notification
✅ Offline-First: Sync payment saat online kembali
✅ Idempotent: Retry-safe operations
✅ Audit Trail: Full payment lifecycle tracking

🏗️ Architecture

💳 Supported Payment Methods

Xendit (Primary Provider)

Method	Channel	Status	Notes
QRIS	QR_CODE	✅ Production	Dynamic QR via QR Codes API
GoPay	EWALLET	✅ Production	E-Wallet Payment API
OVO	EWALLET	✅ Production	E-Wallet Payment API
DANA	EWALLET	✅ Production	E-Wallet Payment API
ShopeePay	EWALLET	✅ Production	E-Wallet Payment API
VA BCA	VIRTUAL_ACCOUNT	✅ Production	Virtual Account API
VA BNI	VIRTUAL_ACCOUNT	✅ Production	Virtual Account API
VA BRI	VIRTUAL_ACCOUNT	✅ Production	Virtual Account API
VA Mandiri	VIRTUAL_ACCOUNT	✅ Production	Virtual Account API
Credit Card	CARDS	✅ Production	Cards API

Midtrans (Secondary Provider)

Method	Channel	Status	Notes
QRIS	QR_CODE	🚧 Development	Snap API
GoPay	EWALLET	🚧 Development	Snap API
Credit Card	CARDS	🚧 Development	Snap API

📡 Payment API Endpoints

1. Create Payment Request

Membuat payment request untuk transaksi.

curl -X POST https://api.mushola-store.com/api/v1/pos/payments \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer YOUR_TOKEN" \
  -d '{
    "order_code": "TRX-MC01-BRN-MST-OSK00001-251013-5UJW-6SWG-7",
    "method": "qris",
    "amount": 33000,
    "currency": "IDR",
    "customer_email": "[email protected]",
    "success_url": "https://pos.mushola-store.com/payment/success",
    "failure_url": "https://pos.mushola-store.com/payment/failed"
  }'

Response (QRIS):

{
  "code": 200,
  "data": {
    "qr_url": "https://api.xendit.co/qr_codes/qr_abc123xyz.png",
    "qr_string": "00020101021126...",
    "reference_id": "qr_abc123xyz",
    "transaction_id": "qr_abc123xyz",
    "external_id": "TRX-MC01-BRN-MST-OSK00001-251013-5UJW-6SWG-7",
    "status": "pending",
    "order_code": "TRX-MC01-BRN-MST-OSK00001-251013-5UJW-6SWG-7",
    "method": "qris",
    "amount": 33000,
    "currency": "IDR",
    "channel_code": "QR_CODE",
    "expires_at": "2025-10-13T10:35:00Z",
    "extra": {
      "provider": "xendit",
      "qr_string": "00020101021126..."
    }
  }
}

Response (E-Wallet):

{
  "code": 200,
  "data": {
    "checkout_url": "https://ewallet.gopay.com/checkout/abc123",
    "reference_id": "ewc_abc123xyz",
    "transaction_id": "ewc_abc123xyz",
    "external_id": "TRX-MC01-BRN-MST-OSK00001-251013-5UJW-6SWG-7",
    "status": "pending",
    "order_code": "TRX-MC01-BRN-MST-OSK00001-251013-5UJW-6SWG-7",
    "method": "gopay",
    "amount": 33000,
    "currency": "IDR",
    "channel_code": "EWALLET",
    "expires_at": "2025-10-13T10:35:00Z"
  }
}

2. Get Payment Status

Mengecek status payment request.

curl -X GET https://api.mushola-store.com/api/v1/pos/payments/qr_abc123xyz \
  -H "Authorization: Bearer YOUR_TOKEN"

Response:

{
  "code": 200,
  "data": {
    "reference_id": "qr_abc123xyz",
    "status": "paid",
    "amount": 33000,
    "currency": "IDR",
    "paid_at": "2025-10-13T10:32:15Z",
    "payment_method": "QRIS",
    "channel_code": "QR_CODE"
  }
}

3. Webhook Handler

Endpoint untuk menerima notifikasi dari payment provider.

curl -X POST https://api.mushola-store.com/api/v1/webhook/xendit \
  -H "Content-Type: application/json" \
  -H "X-Callback-Token: YOUR_WEBHOOK_TOKEN" \
  -d '{
    "id": "qr_abc123xyz",
    "external_id": "TRX-MC01-BRN-MST-OSK00001-251013-5UJW-6SWG-7",
    "status": "PAID",
    "amount": 33000,
    "paid_at": "2025-10-13T10:32:15Z"
  }'

Response:

{
  "code": 200,
  "message": "Webhook processed successfully"
}

4. Simulate Payment (Testing)

Endpoint untuk simulasi pembayaran di environment testing.

curl -X POST https://api.mushola-store.com/api/v1/pos/payments/qr_abc123xyz/simulate \
  -H "Authorization: Bearer YOUR_TOKEN" \
  -d '{
    "amount": 33000
  }'

Response:

{
  "code": 200,
  "data": {
    "status": "SUCCEEDED",
    "message": "Payment simulated successfully"
  }
}

🔧 Implementation Details

Xendit Integration

1. QR Codes API (QRIS)

// xendit_service.go
func (c *XenditClient) CreateQRCode(ctx context.Context, req dto.CreatePaymentRequest) (*dto.CreatePaymentResponse, error) {
    payload := xenditQRReq{
        ReferenceID: req.OrderCode,
        Type:        "DYNAMIC",
        Currency:    "IDR",
        Amount:      req.Amount,
        Metadata:    map[string]any{"external_order_code": req.OrderCode},
    }
    
    url := c.BaseURL + "/qr_codes"
    var qr xenditQRResp
    resp, err := c.Resty.R().
        SetContext(ctx).
        SetBasicAuth(c.SecretKey, "").
        SetHeader("Content-Type", "application/json").
        SetBody(payload).
        SetResult(&qr).
        Post(url)
    
    if err != nil {
        return nil, err
    }
    
    return &dto.CreatePaymentResponse{
        QRURL:       qr.ImageURL,
        ReferenceID: qr.ID,
        Status:      "pending",
        Extra: map[string]any{
            "provider":  "xendit",
            "qr_string": qr.QrString,
        },
    }, nil
}

2. Payment Request API (E-Wallet, VA, Cards)

func (c *XenditClient) CreatePaymentRequest(ctx context.Context, req dto.CreatePaymentRequest) (*dto.CreatePaymentResponse, error) {
    // Map method -> channel_code
    channelCode := ""
    switch req.Method {
    case "qris":
        channelCode = "QRIS"
    case "gopay", "ovo", "dana", "shopeepay":
        channelCode = "EWALLET"
    case "va_bca", "va_bni", "va_bri", "va_mandiri":
        channelCode = "VIRTUAL_ACCOUNT"
    case "credit_card":
        channelCode = "CARDS"
    }
    
    payload := xenditPaymentReq{
        ReferenceID:       req.OrderCode,
        Amount:            req.Amount,
        Currency:          "IDR",
        ChannelCode:       channelCode,
        ChannelProperties: buildChannelProperties(req),
        Metadata:          map[string]any{"order_code": req.OrderCode},
    }
    
    url := c.BaseURL + "/payment_requests"
    var pr xenditPaymentResp
    resp, err := c.Resty.R().
        SetContext(ctx).
        SetBasicAuth(c.SecretKey, "").
        SetHeader("Content-Type": "application/json").
        SetBody(payload).
        SetResult(&pr).
        Post(url)
    
    return mapToPaymentResponse(pr), err
}

3. Webhook Handler

func (s *service) HandleNotification(ctx context.Context, payload map[string]any) error {
    invoiceID := payload["id"].(string)
    externalID := payload["external_id"].(string)
    status := payload["status"].(string)
    
    // Map status Xendit -> internal
    statusMapped := mapXenditStatus(status)
    
    // Update payment record
    merchID, branchID, txID, _ := s.trxService.ResolveByTransactionCode(ctx, externalID)
    _ = s.payRepo.UpsertFromWebhook(ctx, invoiceID, externalID, statusMapped, payload, merchID, branchID, txID)
    
    // Update transaction status via state machine
    if txID != nil && statusMapped == "paid" {
        verifyPayload := transaction.PayloadVerifyPayment{
            PaymentGatewayRef: invoiceID,
        }
        _, err := s.trxService.VerifyPayment(ctx, int64(*txID), verifyPayload)
        if err != nil {
            // Log error tapi jangan fail webhook
            log.Printf("[webhook] failed to verify payment: %v", err)
        }
    }
    
    return nil
}

Payment Model (Database)

// payment_model.go
type Payment struct {
    ID                 uint           `gorm:"primaryKey"`
    MerchantID         uint           `gorm:"not null"`
    BranchID           *uint
    TransactionID      *uint
    PaymentCode        *string
    ReferenceID        *string
    IdempotencyKey     *string
    Provider           string         `gorm:"not null"` // xendit, midtrans
    Channel            *string        // QR_CODE, EWALLET, VIRTUAL_ACCOUNT, CARDS
    Method             *string        // qris, gopay, ovo, dana, va_bca, etc
    Amount             float64        `gorm:"type:decimal(18,2)"`
    Currency           string         `gorm:"not null"`
    Status             string         `gorm:"not null"` // pending, success, failed, expired, canceled
    ExternalPaymentID  *string
    ExternalInvoiceID  *string
    QRString           *string
    PaidAt             *time.Time
    ExpiresAt          *time.Time
    LastErrorCode      *string
    LastErrorMessage   *string
    WebhookStatus      *string
    WebhookReceivedAt  *time.Time
    IsOffline          bool
    DeviceID           *string
    OfflineReference   *string
    SyncStatus         string         // pending, synced, failed
    SyncAttempts       *int
    LastSyncAt         *time.Time
    RequestPayload     datatypes.JSON
    ResponsePayload    datatypes.JSON
    CallbackPayload    datatypes.JSON
    CreatedAt          *time.Time
    UpdatedAt          *time.Time
    DeletedAt          gorm.DeletedAt
}

🔒 Security

1. Webhook Verification

// Verify Xendit webhook signature
func verifyXenditWebhook(payload []byte, signature string, token string) bool {
    mac := hmac.New(sha256.New, []byte(token))
    mac.Write(payload)
    expectedSignature := hex.EncodeToString(mac.Sum(nil))
    return hmac.Equal([]byte(signature), []byte(expectedSignature))
}

2. API Key Management

# Environment variables
XENDIT_SECRET_KEY=xnd_development_...
XENDIT_WEBHOOK_TOKEN=your_webhook_verification_token
MIDTRANS_SERVER_KEY=SB-Mid-server-...
MIDTRANS_CLIENT_KEY=SB-Mid-client-...

3. Idempotency

// Generate idempotency key
idempotencyKey := fmt.Sprintf("%s-%s-%d", 
    merchantID, 
    transactionCode, 
    time.Now().Unix())

🧪 Testing

Unit Test Example

func TestCreateQRCode(t *testing.T) {
    client := NewXenditClient("test_key", "https://api.xendit.co")
    
    req := dto.CreatePaymentRequest{
        OrderCode: "TRX-TEST-001",
        Method:    "qris",
        Amount:    50000,
        Currency:  "IDR",
    }
    
    resp, err := client.CreateQRCode(context.Background(), req)
    
    assert.NoError(t, err)
    assert.NotEmpty(t, resp.QRURL)
    assert.Equal(t, "pending", resp.Status)
}

Integration Test with Godog

Feature: Payment Gateway Integration
  
  Scenario: Create QRIS payment
    Given I have a transaction "TRX-TEST-001" with amount 50000
    When I create a QRIS payment request
    Then I should receive a QR code URL
    And payment status should be "pending"
  
  Scenario: Handle payment webhook
    Given I have a pending payment "qr_abc123"
    When Xendit sends a webhook with status "PAID"
    Then payment status should be updated to "success"
    And transaction status should be "paid"

📊 Monitoring

Payment Metrics

// Metrics to track
type PaymentMetrics struct {
    TotalRequests       int64
    SuccessCount        int64
    FailedCount         int64
    PendingCount        int64
    AverageResponseTime time.Duration
    WebhookReceived     int64
    WebhookFailed       int64
}

Grafana Dashboard

Payment Success Rate: success_count / total_requests * 100
Payment Latency: P50, P95, P99 response time
Webhook Delivery: Success vs Failed
Provider Availability: Uptime per provider

💡 Best Practices

DO ✅

Simpan full request/response payload untuk audit
Gunakan idempotency key untuk retry safety
Verify webhook signature sebelum process
Handle webhook idempotent (cek duplicate)
Set proper timeout untuk external API calls
Monitor payment success rate per provider
Implement circuit breaker untuk provider failures

DON’T ❌

Jangan hardcode API keys di source code
Jangan skip webhook verification
Jangan block webhook response (process async)
Jangan expose payment details di client-side
Jangan retry webhook infinitely
Jangan ignore payment expiration

🆘 Troubleshooting

Problem: Payment Stuck in Pending

Symptoms: Status tidak update setelah customer bayar Solution:

Check webhook logs di Xendit dashboard
Verify webhook URL accessible dari internet
Manual check payment status via API
Re-send webhook dari Xendit dashboard

Problem: QR Code Not Generated

Symptoms: Error saat create QR code Solution:

Verify Xendit API key valid
Check amount minimum (Rp 1.500)
Verify currency = “IDR”
Check Xendit API status

Problem: Webhook Signature Invalid

Symptoms: Webhook rejected dengan error signature Solution:

Verify webhook token di environment
Check payload format (raw body)
Verify HMAC calculation
Check Xendit webhook settings

Transaction Flow

Alur transaksi lengkap dengan state machine dan offline-first

Xendit API Reference

Official Xendit documentation

Midtrans API Reference

Official Midtrans documentation

Need Help? Contact backend team atau check GitHub Issues

Business Features

Offline-First Architecture

Real-time Sync

​Payment Gateway Integration

​🎯 Overview

​🏗️ Architecture

​💳 Supported Payment Methods

​Xendit (Primary Provider)

​Midtrans (Secondary Provider)

​📡 Payment API Endpoints

​1. Create Payment Request

​2. Get Payment Status

​3. Webhook Handler

​4. Simulate Payment (Testing)

​🔧 Implementation Details

​Xendit Integration

​1. QR Codes API (QRIS)

​2. Payment Request API (E-Wallet, VA, Cards)

​3. Webhook Handler

​Payment Model (Database)

​🔒 Security

​1. Webhook Verification

​2. API Key Management

​3. Idempotency

​🧪 Testing

​Unit Test Example

​Integration Test with Godog

​📊 Monitoring

​Payment Metrics

​Grafana Dashboard

​💡 Best Practices

​DO ✅

​DON’T ❌

​🆘 Troubleshooting

​Problem: Payment Stuck in Pending

​Problem: QR Code Not Generated

​Problem: Webhook Signature Invalid

​📚 Related Documentation

Transaction Flow

Xendit API Reference

Midtrans API Reference

Payment Gateway Integration

🎯 Overview

🏗️ Architecture

💳 Supported Payment Methods

Xendit (Primary Provider)

Midtrans (Secondary Provider)

📡 Payment API Endpoints

1. Create Payment Request

2. Get Payment Status

3. Webhook Handler

4. Simulate Payment (Testing)

🔧 Implementation Details

Xendit Integration

1. QR Codes API (QRIS)

2. Payment Request API (E-Wallet, VA, Cards)

3. Webhook Handler

Payment Model (Database)

🔒 Security

1. Webhook Verification

2. API Key Management

3. Idempotency

🧪 Testing

Unit Test Example

Integration Test with Godog

📊 Monitoring

Payment Metrics

Grafana Dashboard

💡 Best Practices

DO ✅

DON’T ❌

🆘 Troubleshooting

Problem: Payment Stuck in Pending

Problem: QR Code Not Generated

Problem: Webhook Signature Invalid

📚 Related Documentation