Stripe processed, now what? - stripe-payments

Question

I'm trying to build a serverless NuxtJS app, utilizing firebase for authentication, netlify for deployment (and functions) and stripe for payment.
This whole payment-process and serverless functions on netlify is all new to me, so this might be a nooby question.
I've followed serveral docs and guides, and accomplished an app with firebase authentication, netlify deployment and serverless functions making me able to process a stripe payment - now I just cant figure out the next step. My stripe success_url leads to a /pages/succes/index.js route containing a success message -> though here I'd need some data response from Stripe, making me able to present the purchased item and also attaching the product id as a "bought-product" entry on the user object in firebase (the products will essentially be an upgrade to the user profile).
Click "buy product" function
async buyProduct(sku, qty) {
const data = {
sku: sku,
quantity: qty,
};
const response = await fetch('/.netlify/functions/create-checkout', {
method: 'POST',
headers: {
'Content-Type': 'application/json',
},
body: JSON.stringify(data),
}).then((res) => res.json());
console.log(response);
const stripe = await loadStripe(response.publishableKey);
const { error } = await stripe.redirectToCheckout({
sessionId: response.sessionId,
});
if (error) {
console.error(error);
}
}
create-checkout Netlify function
const stripe = require('stripe')(process.env.STRIPE_SECRET_KEY);
const inventory = require('./data/products.json');
exports.handler = async (event) => {
const { sku, quantity } = JSON.parse(event.body);
const product = inventory.find((p) => p.sku === sku);
const validatedQuantity = quantity > 0 && quantity < 11 ? quantity : 1;
const session = await stripe.checkout.sessions.create({
payment_method_types: ['card'],
billing_address_collection: 'auto',
shipping_address_collection: {
allowed_countries: ['US', 'CA'],
},
success_url: `${process.env.URL}/success`,
cancel_url: process.env.URL,
line_items: [
{
name: product.name,
description: product.description,
images: [product.image],
amount: product.amount,
currency: product.currency,
quantity: validatedQuantity,
},
],
});
return {
statusCode: 200,
body: JSON.stringify({
sessionId: session.id,
publishableKey: process.env.STRIPE_PUBLISHABLE_KEY,
}),
};
};
Please let me know if you need more information, or something doesnt make sense!
tldr; I've processed a Stripe payment in a serverless app using Netlify function, and would like on the success-page to be able to access the bought item and user information.

Answer 1

When you create your Checkout Session and define your success_url, you can append session_id={CHECKOUT_SESSION_ID} as a template where Stripe will auto-fill in the session ID. See https://stripe.com/docs/payments/checkout/accept-a-payment#create-checkout-session
In your case you'd do:
success_url: `${process.env.URL}/success?session_id={CHECKOUT_SESION_ID}`,
Then when your user is redirected to your success URL you can retrieve the session with the session ID and do any purchase fulfilment.