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 with configuration
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);

// Endpoint to create a payment session
app.post('/api/payments/sessions', async (req, res) => {
  try {
    const { amount, currency, reference, returnUrl, countryCode } = req.body;

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

    const paymentSessionRequest = {
      merchantAccount: config.merchantAccount,
      amount: {
        currency: currency,
        value: amount // Amount in minor units (e.g., cents)
      },
      reference: reference,
      returnUrl: returnUrl,
      countryCode: countryCode || 'US',
      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: 'Failed to create payment session', details: error.message });
  }
});

// Webhook endpoint to handle payment notifications
app.post('/api/webhooks/adyen', async (req, res) => {
  try {
    const notificationRequest = req.body;
    const hmacKey = process.env.ADYEN_HMAC_KEY;

    // Verify HMAC signature for security
    const notificationRequestItems = notificationRequest.notificationItems;
    
    if (!notificationRequestItems || notificationRequestItems.length === 0) {
      return res.status(400).json({ error: 'Invalid notification format' });
    }

    const notificationItem = notificationRequestItems[0].NotificationRequestItem;
    const expectedSignature = notificationItem.additionalData['hmacSignature'];
    
    // Calculate HMAC signature
    const signedString = [
      notificationItem.pspReference,
      notificationItem.originalReference,
      notificationItem.merchantAccountCode,
      notificationItem.merchantReference,
      notificationItem.amount.value,
      notificationItem.amount.currency,
      notificationItem.eventCode,
      notificationItem.success
    ].join(':');
    
    const hmac = crypto.createHmac('sha256', Buffer.from(hmacKey, 'hex'));
    hmac.update(signedString);
    const calculatedSignature = hmac.digest('base64');

    if (calculatedSignature !== expectedSignature) {
      console.error('HMAC signature verification failed');
      return res.status(401).json({ error: 'Invalid signature' });
    }

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

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

    // 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' });
  }
});

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