Comprehensive comparison for Payment Processing technology in Software Development applications

const express = require('express');
const axios = require('axios');
const crypto = require('crypto');

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

// Klarna API Configuration
const KLARNA_API_URL = process.env.KLARNA_API_URL || 'https://api.playground.klarna.com';
const KLARNA_USERNAME = process.env.KLARNA_USERNAME;
const KLARNA_PASSWORD = process.env.KLARNA_PASSWORD;

// Create base64 encoded authorization header
const getAuthHeader = () => {
  const credentials = Buffer.from(`${KLARNA_USERNAME}:${KLARNA_PASSWORD}`).toString('base64');
  return `Basic ${credentials}`;
};

// Create Klarna payment session
app.post('/api/payments/klarna/session', async (req, res) => {
  try {
    const { order_amount, order_lines, purchase_country, purchase_currency, locale } = req.body;

    // Validate required fields
    if (!order_amount || !order_lines || !purchase_country || !purchase_currency) {
      return res.status(400).json({ error: 'Missing required fields' });
    }

    // Create Klarna session payload
    const sessionPayload = {
      purchase_country: purchase_country,
      purchase_currency: purchase_currency,
      locale: locale || 'en-US',
      order_amount: order_amount,
      order_tax_amount: Math.round(order_amount * 0.1),
      order_lines: order_lines,
      merchant_urls: {
        terms: `${process.env.BASE_URL}/terms`,
        checkout: `${process.env.BASE_URL}/checkout`,
        confirmation: `${process.env.BASE_URL}/confirmation?order_id={checkout.order.id}`,
        push: `${process.env.BASE_URL}/api/payments/klarna/push?order_id={checkout.order.id}`
      }
    };

    // Call Klarna API to create session
    const response = await axios.post(
      `${KLARNA_API_URL}/payments/v1/sessions`,
      sessionPayload,
      {
        headers: {
          'Authorization': getAuthHeader(),
          'Content-Type': 'application/json'
        },
        timeout: 10000
      }
    );

    res.json({
      session_id: response.data.session_id,
      client_token: response.data.client_token
    });

  } catch (error) {
    console.error('Klarna session creation error:', error.response?.data || error.message);
    res.status(error.response?.status || 500).json({
      error: 'Failed to create Klarna session',
      details: error.response?.data || error.message
    });
  }
});

// Create order after authorization
app.post('/api/payments/klarna/order', async (req, res) => {
  try {
    const { authorization_token } = req.body;

    if (!authorization_token) {
      return res.status(400).json({ error: 'Authorization token required' });
    }

    // Create order with Klarna
    const orderResponse = await axios.post(
      `${KLARNA_API_URL}/payments/v1/authorizations/${authorization_token}/order`,
      {
        purchase_country: 'US',
        purchase_currency: 'USD',
        locale: 'en-US',
        merchant_reference1: `order-${Date.now()}`,
        merchant_reference2: crypto.randomBytes(8).toString('hex')
      },
      {
        headers: {
          'Authorization': getAuthHeader(),
          'Content-Type': 'application/json'
        },
        timeout: 10000
      }
    );

    // Store order details in database (pseudo code)
    // await saveOrderToDatabase(orderResponse.data);

    res.json({
      order_id: orderResponse.data.order_id,
      redirect_url: orderResponse.data.redirect_url
    });

  } catch (error) {
    console.error('Klarna order creation error:', error.response?.data || error.message);
    res.status(error.response?.status || 500).json({
      error: 'Failed to create Klarna order',
      details: error.response?.data || error.message
    });
  }
});

// Webhook endpoint for Klarna push notifications
app.post('/api/payments/klarna/push', async (req, res) => {
  try {
    const { order_id } = req.query;

    if (!order_id) {
      return res.status(400).json({ error: 'Order ID required' });
    }

    // Acknowledge receipt immediately
    res.status(200).send('OK');

    // Process order asynchronously
    // await updateOrderStatus(order_id, 'completed');
    // await sendConfirmationEmail(order_id);

  } catch (error) {
    console.error('Klarna webhook error:', error.message);
    res.status(500).json({ error: 'Webhook processing failed' });
  }
});

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