How Makerkit handles Stripe Webhooks | Next.js Supabase SaaS Kit

Makerkit handles five webhooks from Stripe and stores "just enough" data into the organization's entity to function correctly.

The Stripe's webhooks topics are defined here at src/core/stripe/stripe-webhooks.enum.ts:

export enum StripeWebhooks {
  Completed = 'checkout.session.completed',
  SubscriptionDeleted = 'customer.subscription.deleted',
  SubscriptionUpdated = 'customer.subscription.updated',
}

To handle webhooks, we created an API route at pages/api/stripe/webhook.ts.

This route is responsible for:

1. Validating that the webhook is coming from Stripe
2. Routing the webhook to its handler

Validating Stripe's Webhooks

To validate the webhook, we do the following:

1. get the header 'stripe-signature'
2. create a Stripe instance
3. get the raw body
4. call constructEvent to validate and build an event object sent by Stripe. When this fails, it will throw an error

const signature = req.headers['stripe-signature'];
// verify signature header is not missing
if (!signature) {
  return throwBadRequestException(res);
}
const rawBody = await getRawBody(req);
const stripe = await getStripeInstance();
const event = stripe.webhooks.constructEvent(
  rawBody,
  signature,
  webhookSecretKey
);

Handling Stripe's Webhooks

After validating the webhook, we can now handle the webhook type relative to its topic:

switch (event.type) {
  case StripeWebhooks.Completed: {
    // handle completed
  }
  case StripeWebhooks.AsyncPaymentSuccess: {
     // handle async payment success
  }
}

As described above, we handle 5 events:

1. Completed: the checkout session was completed (but payment may not have arrived yet if it's asynchronous)
2. SubscriptionDeleted: the subscription was deleted by the customer
3. SubscriptionUpdated: the subscription was updated by the customer

Checkout Completed

When a user completes the checkout session, we create the subscription object on the currently connected user's organization.

The subscription's object has the following interface:

export interface OrganizationSubscription {
  id: string;
  priceId: string;
  status: Stripe.Subscription.Status;
  currency: string | null;
  cancelAtPeriodEnd: boolean;
  interval: string | null;
  intervalCount: number | null;
  createdAt: UnixTimestamp;
  periodStartsAt: UnixTimestamp;
  periodEndsAt: UnixTimestamp;
  trialStartsAt: UnixTimestamp | null;
  trialEndsAt: UnixTimestamp | null;
}

This interface is added to the Organization object.

Subscription Updated

When a subscription is updated, we rebuild the subscription object and update it in the organization's Firestore entity.

Subscription Deleted

When a subscription is deleted, we simply remove it from the organization entity.

Adding additional webhooks

If you want to add additional webhooks, you can do so by adding a new case in the switch statement.

For example, if you want to handle the customer.subscription.trial_will_end event, you can do so by adding the following case:

case 'customer.subscription.trial_will_end': {
  // handle trial will end
}

Adding additional data to the subscription object

If you want to add additional data to the subscription object, you can do so by adding the data to the OrganizationSubscription interface.

For example, if you want to add the quantity property to the subscription object, you can do so by adding the following property to the interface:

export interface OrganizationSubscription {
  // ...
  quantity: number | null;
}

Then, you can add the data to the subscription object using the buildOrganizationSubscription function:

import type { Stripe } from 'stripe';
import type { OrganizationSubscription } from '~/lib/organizations/types/organization-subscription';
export function buildOrganizationSubscription(
 subscription: Stripe.Subscription,
): OrganizationSubscription {
 const lineItem = subscription.items.data[0];
 const price = lineItem.price;
 return {
   // your props
   quantity: lineItem.quantity,
   // default props
   id: subscription.id,
   priceId: price?.id,
   status: subscription.status,
   cancelAtPeriodEnd: subscription.cancel_at_period_end,
   currency: lineItem.price.currency ?? null,
   interval: price?.recurring?.interval ?? null,
   intervalCount: price?.recurring?.interval_count ?? null,
   createdAt: subscription.created,
   periodStartsAt: subscription.current_period_start,
   periodEndsAt: subscription.current_period_end,
   trialStartsAt: subscription.trial_start ?? null,
   trialEndsAt: subscription.trial_end ?? null,
 };
}