LNURL implementation for Breez SDK

Overview

This server application allows mobile apps that use the Breez SDK to register webhooks and exposes an LNURL pay endpoint for that app. It also acts as a bridge between the mobile app and payer.

How it works?

• lnurlpay Registration: A mobile app registers a webhook to be reached by the server. The webhook is registered under a specific node pubkey. The server stores the pubkey and the webhook details in a database.
• LNURL Pay Endpoint: The server exposes an LNURL pay endpoint for the mobile app (lnurlp/pubkey).
• Bridge: When a payer starts the lnurl pay flow, the server receives the request and forwards it to the mobile app's webhook, providing a callback. The mobile app processes the request and responds via the callback. The server matches the response to the request and returns it to the payer.

Getting Started

Installation

1. Clone the repository:

   git clone https://github.com/breez/breez-lnurl.git
   

2. Navigate to the project directory:

   cd breez-lnurl
   

3. Install dependencies:

   go mod tidy
   

Configuration

There are two optional environment variables that can be set:

• SERVER_EXTERNAL_URL: The url this server can be reached from the outside world.
• SERVER_INTERNAL_URL: The internal url the server listens to.
• DATABASE_URL: The database url.

Running the Server

Execute the command below to start the server:

go run .

API Endpoints

• Register LNURL Webhook:

  • Endpoint: /lnurlpay/{pubkey}
  • Method: POST
  • payload: {time: <seconds since epoch>, url: <webhook url>, signature: <signature of "time-url">}
  • Description: Registers a new webhook for the mobile app.

• LNURL Pay Info Endpoint:

  • Endpoint: lnurlp/{pubkey}/
  • Method: GET
  • Description: Handles LNURL pay requests, forwarding them to the corresponding mobile app webhook.

• LNURL Pay Invoice Endpoint:

  • Endpoint: lnurlpay/{pubkey}/invoice?amount=<amount>
  • Method: GET
  • Description: Handles LNURL pay invoice requests, forwarding them to the corresponding mobile app webhook.

• Webhook Callback Endpoint:

  • Endpoint: /response/{responseID}
  • Method: POST
  • Description: Handles webhook callback responses from the node.