# Backend

Rust backend for Caravel. It manages tenants, relays, invoices, and background workers for relay provisioning and billing.

## Tech Stack

- Rust (Edition 2024)
- Axum (HTTP API)
- SQLx + SQLite
- Tokio (async runtime + workers)
- Nostr SDK (NIP-98 auth, NIP-17 DMs, NIP-47 wallet connect)

## Layout

```
backend/
  migrations/
    0001_init.sql
  src/
    api.rs       # Axum routes + NIP-98 auth checks
    billing.rs   # Invoice generation + collection worker
    infra.rs     # Zooid sync worker
    main.rs      # App bootstrap
    models.rs    # DB models
    repo.rs      # Data access layer
    robot.rs     # Nostr robot identity + DM sending
```

## Configuration

Environment variables:

| Variable | Description | Default |
|---|---|---|
| `DATABASE_URL` | SQLite URL. Relative paths are resolved under `backend/`. | `sqlite://<backend>/data/caravel.db` |
| `HOST` | API bind host (also used for NIP-98 `u` host check) | `127.0.0.1` |
| `PORT` | API bind port | `3000` |
| `ADMINS` | Comma-separated admin pubkeys (hex) | _optional_ |
| `ALLOW_ORIGINS` | Comma-separated CORS origins. If empty, CORS is permissive. | _optional_ |
| `ZOOID_API_URL` | Zooid API base URL used by infra worker | _required for infra sync_ |
| `ZOOID_API_SECRET` | Nostr secret key used for authentication of requests to the zooid API | _required_ |
| `RELAY_DOMAIN` | Base domain appended to relay subdomains | empty |
| `LIVEKIT_URL` | LiveKit URL sent to zooid when relay livekit is enabled | _optional_ |
| `LIVEKIT_API_KEY` | LiveKit API key sent to zooid | _optional_ |
| `LIVEKIT_API_SECRET` | LiveKit API secret sent to zooid | _optional_ |
| `NWC_URL` | Platform NWC URL used to generate BOLT11 invoices | _required for invoice generation_ |
| `ROBOT_SECRET` | Robot Nostr secret key | _required_ |
| `ROBOT_NAME` | Robot display name (kind `0`) | _optional_ |
| `ROBOT_DESCRIPTION` | Robot description (kind `0`) | _optional_ |
| `ROBOT_PICTURE` | Robot picture URL (kind `0`) | _optional_ |
| `ROBOT_OUTBOX_RELAYS` | Comma-separated relays published as kind `10002` | _required_ |
| `ROBOT_INDEXER_RELAYS` | Comma-separated relays used for recipient relay discovery | _required_ |
| `ROBOT_MESSAGING_RELAYS` | Comma-separated relays published as kind `10050` | _required_ |

Relay list env vars are comma-separated and trimmed. If a relay has no `ws://` or `wss://` scheme, `wss://` is prepended.

## Schema and Architecture

See [spec](spec) for more details

## API Routes

All routes are NIP-98 protected.

- `GET /identity` — get auth identity (`pubkey`, `is_admin`)
- `GET /tenants` — list tenants (admin)
- `POST /tenants` — create current auth pubkey as tenant
- `GET /tenants/:pubkey` — get tenant (admin or same tenant)
- `PUT /tenants/:pubkey/billing` — update tenant `nwc_url` (admin or same tenant)
- `GET /relays` — list relays (`?tenant=<pubkey>` allowed for admin only)
- `POST /relays` — create relay (admin or relay tenant)
- `GET /relays/:id` — get relay (admin or relay tenant)
- `PUT /relays/:id` — update relay (admin or relay tenant)
- `POST /relays/:id/deactivate` — deactivate relay (admin or relay tenant)
- `GET /invoices` — list invoices (`?tenant=<pubkey>` allowed for admin only)