OCR APIとWebhookで買掛金管理の自動化パイプラインを構築する

const express = require('express');
const crypto = require('crypto');

// Middleware to get the raw body for signature verification
const rawBodySaver = (req, res, buf, encoding) => {
  if (buf && buf.length) {
    req.rawBody = buf.toString(encoding || 'utf8');
  }
};

const app = express({ verify: rawBodySaver });
const webhookSecret = process.env.SPACE_OCR_WEBHOOK_SECRET;

app.post('/webhook', (req, res) => {
  const signature = req.get('X-Spaceocr-Signature');
  if (!signature) {
    return res.status(400).send('Missing signature');
  }

  const hmac = crypto.createHmac('sha256', webhookSecret);
  const digest = Buffer.from(hmac.update(req.rawBody).digest('hex'), 'hex');
  const receivedSignature = Buffer.from(signature, 'hex');

  if (!crypto.timingSafeEqual(digest, receivedSignature)) {
    return res.status(400).send('Invalid signature');
  }

  // Signature is valid, now process the event
  const event = JSON.parse(req.rawBody);

  switch (event.event) {
    case 'ocr.completed':
      const { result } = event.data;
      console.log(`OCR successful for ${result.name}:`, result.values);
      // TODO: Add structured data to your accounting system
      break;
    case 'ocr.failed':
      const { error } = event.data;
      console.error(`OCR failed for ${event.data.name}:`, error.message);
      break;
    case 'webhook.test':
      console.log('Webhook test successful!');
      break;
    default:
      console.log(`Unhandled event type: ${event.event}`);
  }

  res.status(200).send({ received: true });
});

app.listen(3000, () => console.log('Webhook receiver listening on port 3000'));