Express

1mkdir seshn-express && cd seshn-express
2npm init -y
3npm install @seshn/sdk express
4npm install -D typescript @types/express tsx

1import { Seshn } from '@seshn/sdk';
2
3export const seshn = new Seshn(process.env.SESHN_API_KEY!, {
4  baseUrl: 'https://api.seshn.net',
5});

1import express from 'express';
2import crypto from 'crypto';
3import { seshn } from './seshn';
4
5const app = express();
6
7// Parse JSON for all routes except webhooks (need raw body there)
8app.use((req, res, next) => {
9  if (req.path === '/webhooks') {
10    express.raw({ type: 'application/json' })(req, res, next);
11  } else {
12    express.json()(req, res, next);
13  }
14});
15
16// ─── GET /availability ──────────────────────────────────────
17app.get('/availability', async (req, res) => {
18  const { serviceId, from, to } = req.query as Record<string, string>;
19
20  const result = await seshn.availability.query({
21    serviceId,
22    from,
23    to,
24  });
25
26  res.json(result.data);
27});
28
29// ─── POST /book ─────────────────────────────────────────────
30app.post('/book', async (req, res) => {
31  const { slotId, contactId, seats } = req.body;
32
33  // Create the booking
34  const { booking } = await seshn.bookings.create({
35    slotId,
36    contactId,
37    seats,
38  });
39
40  // Confirm immediately
41  const { booking: confirmed } = await seshn.bookings.confirm(booking.id);
42
43  res.json(confirmed);
44});
45
46// ─── POST /webhooks ─────────────────────────────────────────
47app.post('/webhooks', (req, res) => {
48  const signature = req.headers['x-webhook-signature'] as string;
49  const event = req.headers['x-webhook-event'] as string;
50  const payload = (req.body as Buffer).toString('utf-8');
51
52  // Verify HMAC signature
53  if (!verifySignature(payload, signature, process.env.SESHN_WEBHOOK_SECRET!)) {
54    res.status(401).json({ error: 'Invalid signature' });
55    return;
56  }
57
58  const data = JSON.parse(payload);
59  console.log(`Received ${event}:`, data);
60
61  // Handle different event types
62  switch (event) {
63    case 'booking.confirmed':
64      // Send confirmation email, sync calendar, etc.
65      break;
66    case 'booking.cancelled':
67      // Process refund, notify staff, etc.
68      break;
69    case 'payment.succeeded':
70      // Update your records
71      break;
72  }
73
74  res.json({ received: true });
75});
76
77// ─── Signature verification ─────────────────────────────────
78function verifySignature(payload: string, header: string, secret: string): boolean {
79  const expected = `sha256=${crypto
80    .createHmac('sha256', secret)
81    .update(payload)
82    .digest('hex')}`;
83
84  return crypto.timingSafeEqual(
85    Buffer.from(header),
86    Buffer.from(expected),
87  );
88}
89
90app.listen(3001, () => {
91  console.log('Server running on http://localhost:3001');
92});

1SESHN_API_KEY=sk_test_... npx tsx src/index.ts

1# Check availability
2curl "http://localhost:3001/availability?serviceId=svc_yoga_class&from=2026-03-20&to=2026-03-27"
3
4# Create a booking
5curl -X POST http://localhost:3001/book \
6  -H "Content-Type: application/json" \
7  -d '{"slotId": "slot_...", "contactId": "ct_jane_doe", "seats": 1}'

1const webhook = await seshn.webhooks.create({
2  url: 'https://your-domain.com/webhooks',
3  events: ['booking.confirmed', 'booking.cancelled', 'payment.succeeded'],
4});
5
6// Save webhook.secret -- it won't be shown again
7console.log('Webhook secret:', webhook.secret);