Get Notified When Someone Views Your Deal Room

import express from 'express'
import crypto from 'node:crypto'

const app = express()
app.use(express.raw({ type: 'application/json' }))

const WEBHOOK_SECRET = process.env.VANTAGEKIT_WEBHOOK_SECRET

app.post('/webhooks/vantagekit', (req, res) => {
  // 1. Verify the signature
  const signature = req.headers['x-vantagekit-signature']
  const timestamp = req.headers['x-vantagekit-timestamp']
  const body = req.body.toString()

  const expected = crypto
    .createHmac('sha256', WEBHOOK_SECRET)
    .update(`${timestamp}.${body}`)
    .digest('hex')

  const isValid = crypto.timingSafeEqual(
    Buffer.from(signature.replace('sha256=', '')),
    Buffer.from(expected)
  )

  if (!isValid) {
    return res.status(401).send('Invalid signature')
  }

  // 2. Reject stale timestamps (> 5 minutes old)
  const age = Math.floor(Date.now() / 1000) - Number(timestamp)
  if (age > 300) {
    return res.status(401).send('Timestamp too old')
  }

  // 3. Process the event
  const event = JSON.parse(body)

  if (event.type === 'deal_room.viewed') {
    const { dealRoomId, viewerEmail, duration, timestamp: viewTime } = event.data
    console.log(`${viewerEmail ?? 'Anonymous'} viewed deal room ${dealRoomId}`)

    // Send to Slack, update CRM, etc.
  }

  res.status(200).send('OK')
})

app.listen(3000)