Next.js Server SDK

Installation

Install the SDK via npm:

npm install lancer-next-sdk

---

Getting Started

1. Initialize the Lancer SDK

Create a reusable instance of the Lancer class with your webhookSecret for signature verification. Store this in a shared module for easy access across your API routes.

import Lancer from "lancer-next-sdk";

const lancer = new Lancer({
  webhookSecret: "<your-lancer-webhook-secret>",
});

export default lancer;

Parameter	Type	Required	Description
webhookSecret	string	No	Secret key used to verify webhook signatures.

---

2. Set Up API Routes

Authentication Endpoint

Use the authenticate method to handle session authentication in a Next.js API route. Implement your custom logic within the handler.

import lancer from "@/lib/lancer";

export const POST = lancer.authenticate(async (token, payload) => {
  console.log("Session Payload:", payload);

  // Custom authentication logic
  return {
    ownerId: "<user-id>", // Replace with actual user/owner ID
    status: 200, // HTTP status code
  };
});

Parameter	Type	Description
token	string	Lancer session token from the Authorization header.
payload	SessionRequest	Payload containing session details from Lancer.

Example Request

POST /api/auth
Authorization: Bearer <token>
{
  "file_size": 10485760,     
  "file_name": "example.txt",
  "max_chunk": 2,            
  "chunk_size": 5242880,     
  "provider": "LOCAL"    
}

Example Response

{
  "ownerId": "user123"
}

Webhook Endpoint

Handle webhook events sent by Lancer with the handleWebhook method. Enable verification to ensure payload integrity using your webhookSecret.

import lancer from "@/lib/lancer";

export const POST = lancer.handleWebhook(async (event) => {
  console.log("Webhook Event: ", event.event);

  console.log("Webhook Data: ", event.data);

  // Handle event data
  return Response.json({}, { status: 200 });
}, true);

Parameter	Type	Description
handler	(event: WebhookEvent) => Promise<Response>	Callback function to process webhook events.
verification	boolean	Enables payload verification (default: true).

Verification Workflow

• The SDK verifies the x-timestamp and x-signature headers.
• The payload is signed using HMAC SHA-256 and compared to the provided signature.
• If the verification fails, the SDK responds with 403 Access Restricted.

Example Webhook Payload

{
  "type": "FILE_UPLOAD",
  "data": {
    "id": "session-12345",
    "file_size": 10485760,
    "chunk_size": 5242880,
    "max_chunk": 2,
    "file_name": "example.txt",
    "temp_path": "/tmp/session-12345",
    "owner_id": "user-67890",
    "current_chunk": 0,
    "provider": "LOCAL"
  }
}

Important

Add the authentication endpoints & webhook handling payload to lancer config file as auth-endpoint & webhook-endpoint

---

Security Best Practices

1. Protect Your Webhook Secret: Ensure your webhookSecret is stored securely in environment variables.
2. Verify Signatures: Always enable verification for sensitive webhook endpoints.
3. Rate Limit Your API: Use rate-limiting middleware to prevent abuse.

---

License

MIT License © 2025 Weekend Dev Labs