Clerk

// Next.js route handler: sends your Clerk emails (verification codes, magic links, invitations) through SendSend.
//
// 1. Clerk Dashboard -> Customization -> Emails: turn OFF "Delivered by Clerk" for the templates you want to send yourself.
// 2. Clerk Dashboard -> Webhooks -> Add endpoint -> https://your-app.com/api/clerk-email, and subscribe to the email event listed in the
//    Event Catalog tab (Clerk's docs call it `emails.created`; the handler accepts that and `email.created`). Copy its signing secret.
// 3. Set CLERK_EMAIL_WEBHOOK_SECRET (whsec_...), SENDSEND_API_KEY and SENDSEND_FROM in your environment.
// 4. npm install svix        (put this file at app/api/clerk-email/route.ts)
//
// Clerk fills in the subject and the HTML for each template, so what you design in Clerk is what is sent.
// The field names below (to_email_address, subject, body, body_plain) are what Clerk's email event carries at the time of writing;
// check the Event Catalog for your instance, and adjust here if yours differ. Not tested against a live Clerk instance.
// Leave click tracking OFF for this domain: these emails carry sign-in links.
import { Webhook } from 'svix';

interface ClerkEmail { to_email_address: string; subject: string; body: string; body_plain?: string | null; from_email_name?: string; delivered_by_clerk?: boolean }

export async function POST(req: Request) {
  const body = await req.text();
  let event: { type: string; data: ClerkEmail };
  try {
    event = new Webhook(process.env.CLERK_EMAIL_WEBHOOK_SECRET!).verify(body, {
      'svix-id': req.headers.get('svix-id') ?? '', 'svix-timestamp': req.headers.get('svix-timestamp') ?? '', 'svix-signature': req.headers.get('svix-signature') ?? '',
    }) as typeof event;
  } catch { return new Response('Invalid signature', { status: 400 }); }

  if (!['email.created', 'emails.created'].includes(event.type) || event.data.delivered_by_clerk) return new Response('ignored');
  const e = event.data;
  if (!e.to_email_address || !e.subject || !e.body) return new Response('Unexpected payload: check the field names in the Event Catalog', { status: 422 });
  const res = await fetch('https://api.sendsend.email/v1/emails', {
    method: 'POST',
    headers: {
      Authorization: `Bearer ${process.env.SENDSEND_API_KEY}`, 'Content-Type': 'application/json',
      // The svix-id is the same on every retry of the same webhook, so Clerk retries can never send twice.
      'Idempotency-Key': `clerk-${req.headers.get('svix-id')}`,
    },
    body: JSON.stringify({ from: process.env.SENDSEND_FROM, to: [e.to_email_address], subject: e.subject, html: e.body, ...(e.body_plain ? { text: e.body_plain } : {}) }),
  });
  // A non-2xx makes Clerk retry; the idempotency key keeps the retry safe.
  return new Response(res.ok ? 'sent' : 'failed', { status: res.ok ? 200 : 502 });
}