# lnurl-server

A lightweight LNURL-pay / Lightning Address server that creates invoices via a
NIP-47 (NWC / Nostr Wallet Connect) wallet service.

## What it does

Serves `/.well-known/lnurlp/<username>` and
`/.well-known/lnurlp/<username>/callback`. When a wallet requests a payment,
the callback asks the NWC wallet service for a `make_invoice` and returns the
bolt11 invoice to the payer.

## Configuration (env)

- `NWC_URI` (required) - the `nostr+walletconnect://` connection string for the
  wallet service.
- `LNURL_USERNAME` (default `me`)
- `LNURL_DOMAIN` (default `mleku.dev`)
- `PORT` (default `8096`)

## Why this version

The original implementation opened a fresh WebSocket connection to the relay
for every single invoice request (`nostr.RelayConnect` per callback), which
churned TCP/TLS/WebSocket connections and leaked them into CLOSE-WAIT /
FIN-WAIT-2 on the relay under load. This version:

- Keeps a single persistent relay connection, reused across requests, with
  automatic reconnect if it drops.
- Serializes request/response exchanges with a mutex so concurrent callbacks
  cannot cross-talk on the shared connection.
- Subscribes on the request event id (`#e`) so only the response to the
  current request matches.
- Bounds every exchange with a timeout so a hung wallet never strands a
  subscription or goroutine.
- Uses explicit HTTP server timeouts and graceful shutdown.

## Build

```sh
go build -o lnurl-server .
```