Stripe Integration Helper

Assist with Stripe payment gateway integration for SaaS applications.

Quick Reference

Installation

bun add stripe @stripe/stripe-js

Environment Variables

# Server-side (secret)
STRIPE_SECRET_KEY="sk_live_..."
STRIPE_WEBHOOK_SECRET="whsec_..."

# Client-side (publishable)
NEXT_PUBLIC_STRIPE_PUBLISHABLE_KEY="pk_live_..."

# App URL for callbacks
NEXT_PUBLIC_APP_URL="https://your-app.com"

SDK Initialization

Server-side:

// lib/stripe.ts
import Stripe from "stripe";

export const stripe = new Stripe(process.env.STRIPE_SECRET_KEY!, {
  apiVersion: "2025-01-27.acacia",
  typescript: true,
});

Client-side:

// lib/stripe-client.ts
import { loadStripe } from "@stripe/stripe-js";

export const stripePromise = loadStripe(
  process.env.NEXT_PUBLIC_STRIPE_PUBLISHABLE_KEY!
);

Common Tasks

1. Create Checkout Session

// app/api/checkout/route.ts
import { NextRequest, NextResponse } from "next/server";
import { auth } from "@clerk/nextjs/server";
import { stripe } from "@/lib/stripe";

export async function POST(request: NextRequest) {
  const { userId } = await auth();
  if (!userId) {
    return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
  }

  const { priceId } = await request.json();

  const session = await stripe.checkout.sessions.create({
    mode: "subscription",
    payment_method_types: ["card"],
    line_items: [{ price: priceId, quantity: 1 }],
    success_url: `${process.env.NEXT_PUBLIC_APP_URL}/billing/success?session_id={CHECKOUT_SESSION_ID}`,
    cancel_url: `${process.env.NEXT_PUBLIC_APP_URL}/pricing`,
    metadata: { userId },
    customer_email: user.email, // Optional: pre-fill email
  });

  return NextResponse.json({ url: session.url });
}

2. Create Customer Portal Session

// app/api/billing/portal/route.ts
export async function POST(request: NextRequest) {
  const { userId } = await auth();
  if (!userId) {
    return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
  }

  // Get Stripe customer ID from your database
  const user = await db.query.users.findFirst({
    where: eq(users.id, userId),
  });

  if (!user?.stripeCustomerId) {
    return NextResponse.json({ error: "No subscription" }, { status: 400 });
  }

  const session = await stripe.billingPortal.sessions.create({
    customer: user.stripeCustomerId,
    return_url: `${process.env.NEXT_PUBLIC_APP_URL}/dashboard`,
  });

  return NextResponse.json({ url: session.url });
}

3. Webhook Handler

// app/api/webhooks/stripe/route.ts
import { NextRequest, NextResponse } from "next/server";
import { stripe } from "@/lib/stripe";
import Stripe from "stripe";

export async function POST(request: NextRequest) {
  const body = await request.text();
  const signature = request.headers.get("stripe-signature")!;

  let event: Stripe.Event;

  try {
    event = stripe.webhooks.constructEvent(
      body,
      signature,
      process.env.STRIPE_WEBHOOK_SECRET!
    );
  } catch (err) {
    console.error("Webhook signature verification failed");
    return NextResponse.json({ error: "Invalid signature" }, { status: 400 });
  }

  switch (event.type) {
    case "checkout.session.completed": {
      const session = event.data.object as Stripe.Checkout.Session;
      await handleCheckoutComplete(session);
      break;
    }
    case "customer.subscription.updated": {
      const subscription = event.data.object as Stripe.Subscription;
      await handleSubscriptionUpdate(subscription);
      break;
    }
    case "customer.subscription.deleted": {
      const subscription = event.data.object as Stripe.Subscription;
      await handleSubscriptionCancelled(subscription);
      break;
    }
    case "invoice.payment_failed": {
      const invoice = event.data.object as Stripe.Invoice;
      await handlePaymentFailed(invoice);
      break;
    }
  }

  return NextResponse.json({ received: true });
}

Webhook Events

Event	When to Handle
checkout.session.completed	User completes checkout
customer.subscription.created	New subscription starts
customer.subscription.updated	Plan change, renewal
customer.subscription.deleted	Subscription cancelled
invoice.payment_succeeded	Successful payment
invoice.payment_failed	Failed payment attempt
customer.updated	Customer info changed

Subscription Status Values

Status	Description
active	Subscription is current
past_due	Payment failed, retrying
canceled	Subscription ended
unpaid	All retry attempts failed
trialing	In trial period
incomplete	First payment pending

Database Schema

Users Table (add Stripe fields)

stripeCustomerId    TEXT UNIQUE
stripeSubscriptionId TEXT
stripePriceId       TEXT
stripeCurrentPeriodEnd TIMESTAMP

Subscription Sync Pattern

async function syncSubscription(
  userId: string,
  subscription: Stripe.Subscription
) {
  await db
    .update(users)
    .set({
      stripeSubscriptionId: subscription.id,
      stripePriceId: subscription.items.data[0].price.id,
      stripeCurrentPeriodEnd: new Date(subscription.current_period_end * 1000),
    })
    .where(eq(users.id, userId));
}

Feature Gating

async function checkFeatureAccess(userId: string): Promise<boolean> {
  const user = await db.query.users.findFirst({
    where: eq(users.id, userId),
  });

  if (!user?.stripeSubscriptionId) return false;

  // Check if subscription is still valid
  const now = new Date();
  return user.stripeCurrentPeriodEnd > now;
}

Testing

Test Card Numbers

Card	Scenario
4242424242424242	Successful payment
4000000000000002	Card declined
4000002500003155	Requires 3D Secure
4000000000009995	Insufficient funds

Stripe CLI for Local Webhooks

# Install Stripe CLI
brew install stripe/stripe-cli/stripe

# Login
stripe login

# Forward webhooks to local
stripe listen --forward-to localhost:3000/api/webhooks/stripe

# Trigger test events
stripe trigger checkout.session.completed

Pricing Page Pattern

// Get prices from Stripe
const prices = await stripe.prices.list({
  active: true,
  expand: ["data.product"],
});

// Display in component
{prices.data.map((price) => (
  <PriceCard
    key={price.id}
    name={(price.product as Stripe.Product).name}
    price={price.unit_amount! / 100}
    interval={price.recurring?.interval}
    priceId={price.id}
  />
))}

Security Best Practices

1. Never expose secret key - Use STRIPE_SECRET_KEY only server-side
2. Verify webhook signatures - Always use stripe.webhooks.constructEvent
3. Idempotency - Store event IDs to prevent duplicate processing
4. Raw body for webhooks - Don't parse JSON before verification
5. Use metadata - Store userId in checkout session metadata

Common Issues

Issue	Solution
Webhook signature invalid	Use raw body, not parsed JSON
Customer not found	Create customer before checkout
Subscription not syncing	Check webhook event registration
Test cards failing	Ensure using test mode keys
Portal not loading	Verify customer has active subscription

Useful Commands

# List products
stripe products list

# List prices
stripe prices list

# Get subscription
stripe subscriptions retrieve sub_xxx

# Cancel subscription
stripe subscriptions cancel sub_xxx