nuntius/README.md

# Nuntius — A Small, Opinionated Contact Form Backend

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> Latin *nuntius* = "messenger" — the service that carries messages from visitors to you.

**nuntius** is a small, modular contact form backend written in Go. It serves multiple JSON endpoints (contact, feedback, newsletter, generic) over a single static binary, delivers submissions via SMTP, optionally persists newsletter signups to a JSONL log, and is designed to sit behind nginx on a tiny Linux server. Only the first-party `interpres` TOML module, no external third-party Go modules, ~6 MB binary.

## Features

- **Single static binary** — `go build -ldflags="-s -w"` produces ≈ 6 MB; no Node, no Python, no Redis, no Postgres, no third-party Go packages.
- **Four form kinds out of the box** — `contact`, `feedback`, `newsletter`, and `generic`. Each gets its own endpoint, rate limit, CORS allowlist, and honeypot field.
- **SMTP delivery** — Go stdlib `net/smtp` with `PLAIN` auth. Works with any provider that exposes SMTP.
- **Newsletter subscribers on disk** — append-only JSONL log under `data_dir/`. No database, no double opt-in. One `{email, ip, form, created_at}` line per signup.
- **Server-side validation** — `pkg/contactform.Validate` is reusable; name, email (RFC 5322), service allow-list (for `contact`), and message length.
- **Reusable package** — `pkg/contactform` exports typed `Request` / `Response` / `ErrorResponse` plus a `Validate` function you can drop into any Go project.
- **Structured logging** — `log/slog` with JSON output to stdout; plays well with journald, Loki, Datadog…
- **Graceful shutdown** — SIGINT/SIGTERM close in-flight requests within 15 s.
- **Rate limiting** — token-bucket per IP, configurable per hour, in-memory (no Redis required).
- **Honeypot field** — invisible to humans, required for spam bots. Silently accepts and drops.
- **Config validation** — unknown fields and unknown form types are rejected at startup, so typos fail loudly instead of silently disabling a form.
- **Env-var secrets** — `${VAR_NAME}` / `$VAR_NAME` expansion in the TOML file keeps SMTP passwords out of disk.

## Quick Start

```bash
# 1. Clone
git clone https://codeberg.org/petrbalvin/nuntius.git
cd nuntius

# 2. Build
just build
# → ./bin/nuntius

# 3. Run (auto-creates /etc/nuntius/config.toml with a 3-form template on first start)
sudo mkdir -p /etc/nuntius
just run
# → "nuntius starting" addr=:8080 forms=3

# 4. Edit the generated config to point at your SMTP and recipient
sudo $EDITOR /etc/nuntius/config.toml
just run   # restart to pick up changes
```

A default `config.toml` is auto-generated at `/etc/nuntius/config.toml` on first run with three sample forms (contact, feedback, newsletter). Edit it before exposing the service.

The full schema lives in [`docs/configuration.md`](docs/configuration.md); the deploy guide is in [`docs/deployment.md`](docs/deployment.md).

## Usage

### Test the endpoints

```bash
# Contact form
curl -X POST http://localhost:8080/api/nuntius/contact \
  -H "Content-Type: application/json" \
  -H "Origin: https://petrbalvin.org" \
  -d '{
    "name": "Jane Doe",
    "email": "jane@example.com",
    "service": "architecture",
    "message": "Hello, I would like to discuss an engagement."
  }'

# Feedback (no service field)
curl -X POST http://localhost:8080/api/nuntius/feedback \
  -H "Content-Type: application/json" \
  -H "Origin: https://petrbalvin.org" \
  -d '{
    "name": "Jane Doe",
    "email": "jane@example.com",
    "message": "I love how the site uses Vue.js with zero runtime deps."
  }'

# Newsletter (email only)
curl -X POST http://localhost:8080/api/nuntius/newsletter \
  -H "Content-Type: application/json" \
  -H "Origin: https://petrbalvin.org" \
  -d '{ "email": "jane@example.com" }'
```

Successful response (all three):

```json
{ "ok": true }
```

Validation error (e.g. newsletter with bad email):

```json
{
  "error": "validation",
  "details": [
    { "field": "email", "message": "email is invalid" }
  ]
}
```

### Frontend integration

If you proxy `/api/nuntius/*` through nginx (recommended, see [`docs/deployment.md`](docs/deployment.md)), no frontend config is needed — the form posts to the same origin as the page. Otherwise, set `VITE_NUNTIUS_URL` to the upstream origin:

```js
await fetch(`${import.meta.env.VITE_NUNTIUS_URL || ''}/api/nuntius/contact`, {
  method: 'POST',
  headers: { 'Content-Type': 'application/json' },
  body: JSON.stringify({
    name: name.value,
    email: email.value,
    service: service.value,
    message: message.value,
  }),
});
```

### Use the package in your own project

`pkg/contactform` is a small, dependency-free Go package that you can import into any project:

```go
import "codeberg.org/petrbalvin/nuntius/pkg/contactform"

req := &contactform.Request{
    Name:    "Jane",
    Email:   "jane@example.com",
    Service: "architecture",
    Message: "Hello!",
}

if errs := contactform.Validate(req, "contact"); len(errs) > 0 {
    // handle validation errors
}
```

Full library example: [`docs/library-usage.md`](docs/library-usage.md). Full HTTP API: [`docs/api-reference.md`](docs/api-reference.md).

## Configuration (TL;DR)

Default path: `/etc/nuntius/config.toml`. A starter file is written automatically on first start.

```toml
data_dir = "./data"

[server]
port = 8080

[[forms]]
name = "contact"
type = "contact"
path = "/api/nuntius/contact"
to = "you@example.com"
from = "noreply@example.com"
rate_limit_per_hour = 10
honeypot_field = "website"
allowed_origins = ["https://example.com"]

  [forms.smtp]
  host = "smtp.example.com"
  port = 587
  user = "noreply@example.com"
  password = "${NUNTIUS_SMTP_PASSWORD}"
```

Form types and full schema: [`docs/configuration.md`](docs/configuration.md). Secrets via env vars, CORS, honeypot, rate limit, and validation rules are all documented there.

## Requirements

- **Go 1.26+** (uses Go 1.22+ `http.ServeMux` method patterns and `log/slog`)
- An **SMTP** account (Yandex, Mailgun, Postmark, your own Postfix, …)
- **No other runtime dependencies.** No Node, no Python, no Redis, no Postgres. Configuration is TOML parsed via the first-party [`interpres`](https://codeberg.org/petrbalvin/interpres) library; newsletter storage is an append-only JSONL file via `bufio`.

## Development

```bash
just install        # go mod tidy + go mod download (no-op for this project, kept for symmetry)
just build          # → ./bin/nuntius (with -s -w)
just test           # go test ./...
just run            # go run ./cmd/server
just uninstall      # rm -rf ./bin
```

All four `just` recipes are mandatory per the project conventions and produce zero errors and zero warnings.

## Documentation

- [`docs/architecture.md`](docs/architecture.md) — layers, request flow, design decisions
- [`docs/configuration.md`](docs/configuration.md) — full config schema, form types, secrets, newsletter log
- [`docs/api-reference.md`](docs/api-reference.md) — HTTP verbs, status codes, `GET /health`
- [`docs/deployment.md`](docs/deployment.md) — production systemd, nginx, updates
- [`docs/security.md`](docs/security.md) — threat model, CORS, rate limiting, secret handling
- [`docs/library-usage.md`](docs/library-usage.md) — `pkg/contactform` API and standalone use

## Contributing

See [`CONTRIBUTING.md`](CONTRIBUTING.md) for development setup, code style, commit conventions, and the pull request flow.

## Security

For a full threat model, see [`docs/security.md`](docs/security.md). The short version: every form has its own per-IP rate limit, CORS allowlist, and honeypot field; SMTP credentials never touch the log; unknown config fields are rejected at startup.

If you find a security issue, please email **opensource@petrbalvin.org** rather than opening a public issue.

## License

MIT — see [LICENSE](./LICENSE).  
Copyright © 2026 [Petr Balvín](https://petrbalvin.org)