How to Integrate Stripe for Subscription Payments in FlutterFlow

1// Cloud Function: createCheckoutSession
2const functions = require('firebase-functions');
3const admin = require('firebase-admin');
4const stripe = require('stripe')(functions.config().stripe.secret);
5admin.initializeApp();
6
7exports.createCheckoutSession = functions.https
8  .onCall(async (data, context) => {
9    const uid = context.auth.uid;
10    const priceId = data.priceId;
11    const userDoc = await admin.firestore()
12      .collection('users').doc(uid).get();
13    let customerId = userDoc.data()?.stripeCustomerId;
14
15    if (!customerId) {
16      const customer = await stripe.customers.create({
17        email: context.auth.token.email,
18        metadata: { firebaseUID: uid },
19      });
20      customerId = customer.id;
21      await admin.firestore().collection('users')
22        .doc(uid).update({ stripeCustomerId: customerId });
23    }
24
25    const session = await stripe.checkout.sessions.create({
26      mode: 'subscription',
27      customer: customerId,
28      line_items: [{ price: priceId, quantity: 1 }],
29      success_url: 'https://yourapp.com/success?session_id={CHECKOUT_SESSION_ID}',
30      cancel_url: 'https://yourapp.com/pricing',
31    });
32
33    return { url: session.url };
34  });

1// Cloud Function: stripeWebhook
2exports.stripeWebhook = functions.https
3  .onRequest(async (req, res) => {
4    const sig = req.headers['stripe-signature'];
5    const endpointSecret = functions.config().stripe.webhook_secret;
6    let event;
7    try {
8      event = stripe.webhooks.constructEvent(
9        req.rawBody, sig, endpointSecret
10      );
11    } catch (err) {
12      return res.status(400).send(`Webhook Error: ${err.message}`);
13    }
14
15    const db = admin.firestore();
16    switch (event.type) {
17      case 'checkout.session.completed': {
18        const session = event.data.object;
19        const sub = await stripe.subscriptions
20          .retrieve(session.subscription);
21        const userSnap = await db.collection('users')
22          .where('stripeCustomerId', '==', session.customer)
23          .limit(1).get();
24        if (!userSnap.empty) {
25          await userSnap.docs[0].ref.update({
26            stripeSubscriptionId: sub.id,
27            subscriptionTier: mapPriceToTier(sub.items.data[0].price.id),
28            currentPeriodEnd: admin.firestore.Timestamp
29              .fromMillis(sub.current_period_end * 1000),
30          });
31        }
32        break;
33      }
34      case 'invoice.paid': {
35        const invoice = event.data.object;
36        const sub = await stripe.subscriptions
37          .retrieve(invoice.subscription);
38        const userSnap = await db.collection('users')
39          .where('stripeCustomerId', '==', invoice.customer)
40          .limit(1).get();
41        if (!userSnap.empty) {
42          await userSnap.docs[0].ref.update({
43            currentPeriodEnd: admin.firestore.Timestamp
44              .fromMillis(sub.current_period_end * 1000),
45          });
46        }
47        break;
48      }
49      case 'customer.subscription.deleted': {
50        const sub = event.data.object;
51        const userSnap = await db.collection('users')
52          .where('stripeSubscriptionId', '==', sub.id)
53          .limit(1).get();
54        if (!userSnap.empty) {
55          await userSnap.docs[0].ref.update({
56            subscriptionTier: 'free',
57            stripeSubscriptionId: null,
58            currentPeriodEnd: null,
59          });
60        }
61        break;
62      }
63    }
64    res.status(200).send('OK');
65  });