gamma-webhooks-events

# Gamma Webhooks & Events

## Overview
Implement webhook handlers and event processing for real-time Gamma updates.

## Prerequisites
- Public endpoint for webhook delivery
- Webhook secret from Gamma dashboard
- Understanding of event-driven architecture

## Instructions

### Step 1: Register Webhook Endpoint
```typescript
// Register via API
const webhook = await gamma.webhooks.create({
  url: 'https://your-app.com/webhooks/gamma',
  events: [
    'presentation.created',
    'presentation.updated',
    'presentation.exported',
    'presentation.deleted',
  ],
  secret: process.env.GAMMA_WEBHOOK_SECRET,
});

console.log('Webhook registered:', webhook.id);
```

### Step 2: Create Webhook Handler
```typescript
// routes/webhooks/gamma.ts
import express from 'express';
import crypto from 'crypto';

const router = express.Router();

// Verify webhook signature
function verifySignature(payload: string, signature: string): boolean {
  const secret = process.env.GAMMA_WEBHOOK_SECRET!;
  const expected = crypto
    .createHmac('sha256', secret)
    .update(payload)
    .digest('hex');

  return crypto.timingSafeEqual(
    Buffer.from(signature),
    Buffer.from(`sha256=${expected}`)
  );
}

router.post('/gamma',
  express.raw({ type: 'application/json' }),
  async (req, res) => {
    const signature = req.headers['x-gamma-signature'] as string;
    const payload = req.body.toString();

    // Verify signature
    if (!verifySignature(payload, signature)) {
      return res.status(401).json({ error: 'Invalid signature' });
    }

    // Parse event
    const event = JSON.parse(payload);

    // Acknowledge receipt quickly
    res.status(200).json({ received: true });

    // Process event async
    await processEvent(event);
  }
);

export default router;
```

### Step 3: Event Processing
```typescript
// services/gamma-events.ts
interface GammaEvent {
  id: string;
  type: string;
  data: any;
  timestamp: string;
}

type EventHandler = (data: any) => Promise<void>;

const