I want to run a Firebase cloud function everytime a user is charged by Stripe's subscription extension. Is there any event that is generated by that extension that can trigger a cloud function, such as a write to Firestore?
My scenario is that I want to generate a new document in an Orders collection whenever a user is successfully charged that references the corresponding User document.
I was able to solve this myself by borrowing some code from the official repo for Stripe's Firebase extension here: https://github.com/stripe/stripe-firebase-extensions/blob/next/firestore-stripe-subscriptions/functions/src/index.ts
I made my own Firebase function and called it handleInvoiceWebhook that validated and constructed a Stripe Invoice object, mapped it to a custom Invoice interface I made with the fields I cared about, then saved that to an invoices collection.
export const handleInvoiceWebhook = functions.https.onRequest(
async (req: functions.https.Request, resp) => {
let event: Stripe.Event;
try {
event = stripe.webhooks.constructEvent(
req.rawBody,
req.headers['stripe-signature'] || '',
functions.config().stripe.secret
);
} catch (error) {
resp.status(401).send('Webhook Error: Invalid Secret');
return;
}
const invoice = event.data.object as Stripe.Invoice;
const customerId= invoice.customer as string;
await insertInvoiceRecord(invoice, customerId);
resp.status(200).send(invoice.id);
}
);
/**
* Create an Invoice record in Firestore when a customer's monthly subscription payment succeeds.
*/
const insertInvoiceRecord = async (
invoice: Stripe.Invoice,
customerId: string
): Promise<void> => {
// Invoice is an interface with only fields I care about
const invoiceData: Invoice = {
invoiceId: invoice.id,
...map invoice data here
};
await admin
.firestore()
.collection('invoices')
.doc(invoice.id)
.set(invoiceData);
};
Once deployed, I went to the Stripe developer dashboard (https://dashboard.stripe.com/test/webhooks) and added a new Webhook listening for the Event type invoice.payment_succeeded and with the url being the Firebase function I just made.
NOTE: I had to deploy my Stripe API key and Webhook Secret as enviroment variables for my Firebase function with the following command: firebase functions:config:set stripe.key="sk_test_123" stripe.secret="whsec_456"
Unfortunately it doesn't look like the extension handles the ongoing payment events: https://github.com/stripe/stripe-firebase-extensions/blob/master/firestore-stripe-subscriptions/functions/src/index.ts#L419-L432
You'd either need to modify that code to include likely invoice.payment_succeeded - and then handle appropriately - or write a cloud function to handle that yourself (similar to what's shown there).
