# Event Service Overview

## Overview

The Event Service processes inbound webhook notifications from payment processors using the Node.js SDK. Instead of polling for status updates, webhooks deliver real-time notifications when payment states change.

**Business Use Cases:**

* **Payment completion** - Receive instant notification when payments succeed
* **Failed payment handling** - Get notified of declines for retry logic
* **Refund tracking** - Update systems when refunds complete
* **Dispute alerts** - Immediate notification of new chargebacks

## Operations

| Operation                                                                                                                             | Description                                                                                   | Use When                                        |
| ------------------------------------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------- | ----------------------------------------------- |
| [`handleEvent`](https://github.com/juspay/hyperswitch-docs/blob/main/integration-space/prism/sdks/node/event-service/handle-event.md) | Process webhook from payment processor. Verifies and parses incoming connector notifications. | Receiving webhook POST from Stripe, Adyen, etc. |

## SDK Setup

```javascript
const { EventClient } = require('hyperswitch-prism');

const eventClient = new EventClient({
    connector: 'stripe',
    apiKey: 'YOUR_API_KEY',
    environment: 'SANDBOX'
});
```

## Common Patterns

### Webhook Processing Flow

```mermaid
sequenceDiagram
    participant PP as Payment Provider
    participant App as Your Webhook Endpoint
    participant CS as Prism (EventClient)

    Note over PP: Payment state changes
    PP->>App: POST webhook payload
    App->>CS: handleEvent(payload, headers)
    CS->>CS: Verify signature
    CS->>CS: Parse and transform
    CS-->>App: Return structured event
    App->>App: Update order status
    App-->>PP: 200 OK response
```

**Flow Explanation:**

1. **Provider sends** - When a payment updates, the provider sends a webhook to your endpoint.
2. **Verify and parse** - Pass the raw payload to `handleEvent` for verification and transformation.
3. **Process event** - Receive a structured event object with unified format.
4. **Update systems** - Update your database, fulfill orders, or trigger notifications.

## Webhook Security Example

```javascript
const express = require('express');
const { EventClient } = require('hyperswitch-prism');

const app = express();
const eventClient = new EventClient({
    connector: 'stripe',
    apiKey: 'YOUR_API_KEY'
});

app.post('/webhooks/payments', express.raw({ type: 'application/json' }), async (req, res) => {
    try {
        const event = await eventClient.handleEvent({
            payload: req.body,
            headers: req.headers,
            webhookSecret: 'whsec_xxx'
        });

        if (event.type === 'payment.captured') {
            await fulfillOrder(event.data.merchantTransactionId);
        }

        res.json({ received: true });
    } catch (err) {
        res.status(400).json({ error: err.message });
    }
});
```

## Next Steps

* [Payment Service](https://docs.hyperswitch.io/integrations/prism/node/payment-service) - Handle payment webhooks
* [Refund Service](https://docs.hyperswitch.io/integrations/prism/node/refund-service) - Process refund notifications
* [Dispute Service](https://docs.hyperswitch.io/integrations/prism/node/dispute-service) - Handle dispute alerts