Comprehensive comparison for Payment Processing technology in Software Development applications

const express = require('express');
const { Client, Config, CheckoutAPI } = require('@adyen/api-library');
const crypto = require('crypto');

const app = express();
app.use(express.json());

// Initialize Adyen client
const config = new Config();
config.apiKey = process.env.ADYEN_API_KEY;
config.merchantAccount = process.env.ADYEN_MERCHANT_ACCOUNT;
config.environment = 'TEST'; // Use 'LIVE' for production

const client = new Client({ config });
const checkout = new CheckoutAPI(client);

// Create payment session endpoint
app.post('/api/payments/sessions', async (req, res) => {
  try {
    const { amount, currency, returnUrl, reference, shopperEmail } = req.body;

    // Validate required fields
    if (!amount || !currency || !returnUrl || !reference) {
      return res.status(400).json({ error: 'Missing required fields' });
    }

    // Create payment session
    const paymentSessionRequest = {
      merchantAccount: config.merchantAccount,
      amount: {
        currency: currency,
        value: amount // Amount in minor units (e.g., cents)
      },
      reference: reference,
      returnUrl: returnUrl,
      countryCode: 'US',
      shopperEmail: shopperEmail,
      shopperLocale: 'en-US',
      channel: 'Web',
      lineItems: req.body.lineItems || []
    };

    const response = await checkout.sessions(paymentSessionRequest);
    
    res.json({
      sessionId: response.id,
      sessionData: response.sessionData
    });
  } catch (error) {
    console.error('Payment session creation failed:', error);
    res.status(500).json({ 
      error: 'Payment session creation failed',
      message: error.message 
    });
  }
});

// Handle payment webhook notifications
app.post('/api/webhooks/adyen', async (req, res) => {
  try {
    const notificationRequest = req.body;
    const notificationItems = notificationRequest.notificationItems;

    // Verify webhook signature (HMAC validation)
    const hmacKey = process.env.ADYEN_HMAC_KEY;
    
    for (const item of notificationItems) {
      const notification = item.NotificationRequestItem;
      
      // Validate HMAC signature
      const expectedSign = notification.additionalData?.hmacSignature;
      const payload = `${notification.pspReference}:${notification.originalReference}:${notification.merchantAccountCode}:${notification.merchantReference}:${notification.amount.value}:${notification.amount.currency}:${notification.eventCode}:${notification.success}`;
      const hmac = crypto.createHmac('sha256', hmacKey);
      const calculatedSign = hmac.update(payload).digest('base64');

      if (expectedSign !== calculatedSign) {
        console.error('Invalid HMAC signature');
        return res.status(401).json({ error: 'Invalid signature' });
      }

      // Process notification based on event type
      const { eventCode, success, merchantReference, pspReference } = notification;

      if (eventCode === 'AUTHORISATION') {
        if (success === 'true') {
          // Payment authorized - update order status
          await updateOrderStatus(merchantReference, 'PAID', pspReference);
          console.log(`Payment authorized: ${pspReference}`);
        } else {
          // Payment failed
          await updateOrderStatus(merchantReference, 'FAILED', pspReference);
          console.log(`Payment failed: ${pspReference}`);
        }
      } else if (eventCode === 'REFUND') {
        await updateOrderStatus(merchantReference, 'REFUNDED', pspReference);
        console.log(`Refund processed: ${pspReference}`);
      }
    }

    // Always return [accepted] to acknowledge receipt
    res.status(200).send('[accepted]');
  } catch (error) {
    console.error('Webhook processing error:', error);
    res.status(500).json({ error: 'Webhook processing failed' });
  }
});

// Mock function to update order status
async function updateOrderStatus(orderReference, status, paymentReference) {
  // Implementation would update database
  console.log(`Order ${orderReference} updated to ${status} (Payment: ${paymentReference})`);
  return true;
}

const PORT = process.env.PORT || 3000;
app.listen(PORT, () => {
  console.log(`Payment service running on port ${PORT}`);
});