Adds Next.js App Router example for Webhook signing

examples/webhook-signing/nextjs/app/api/webhooks/route.ts

@@ -0,0 +1,63 @@
+import Stripe from 'stripe';
+import {NextRequest} from 'next/server';
+
+export const config = {
+  api: {
+    bodyParser: false,
+  },
+};
+
+export async function POST(req: NextRequest) {
+  const stripe = new Stripe(process.env.STRIPE_SECRET_KEY);
+  const sig = req.headers.get('stripe-signature');
+  const wh_sec = process.env.STRIPE_WEBHOOK_SECRET;
+  let event: Stripe.Event;
+  if (!sig) {
+    throw new Error('Invalid Signature');
+  }
+  try {
+    const body = Uint8Array.from(await buffer(req)) as Buffer<ArrayBufferLike>;
+    event = stripe.webhooks.constructEvent(body, sig!, wh_sec);
+  } catch (err) {
+    console.log(`❌ Error message: ${err.message}`);
+    return new Response(`Webhook Error: ${err.message}`, {status: 400});
+  }
+  console.log('✅ Success:', event.id);
+
+  // Cast event data to Stripe object
+  if (event.type === 'payment_intent.succeeded') {
+    const stripeObject: Stripe.PaymentIntent = event.data
+      .object as Stripe.PaymentIntent;
+    console.log(`💰 PaymentIntent status: ${stripeObject.status}`);
+  } else if (event.type === 'charge.succeeded') {
+    const charge = event.data.object as Stripe.Charge;
+    console.log(`💵 Charge id: ${charge.id}`);
+  } else {
+    console.warn(`🤷‍♀️ Unhandled event type: ${event.type}`);
+  }
+
+  // Return a response to acknowledge receipt of the event
+  return Response.json({received: true}, {status: 200});
+}
+
+const buffer = async (req: NextRequest) => {
+  const body = req.body;
+  if (!body) {
+    throw new Error('Request body is null');
+  }
+  const reader = body.getReader();
+  const chunks = [];
+  let done, value;
+  while ((({done, value} = await reader.read()), !done)) {
+    chunks.push(value);
+  }
+  const buf = new Uint8Array(
+    chunks.reduce((acc, chunk) => acc + chunk.length, 0)
+  );
+  let offset = 0;
+  for (const chunk of chunks) {
+    buf.set(chunk, offset);
+    offset += chunk.length;
+  }
+  return buf;
+};