# Translations (i18n)

DriverVault's user interface is translatable. Each surface reads its text from
**per-language files** — nothing hardcodes English in the parts that have been
converted — so adding a language is a matter of dropping in a new file, not
editing screens.

Three languages ship today: **English (`en`)**, **Polish (`pl`)** and
**Danish (`da`)**. English is the base and the fallback: any key missing from
another language renders the English string, so a partial translation is always
safe to ship.

The language is the **language half of the user's BCP-47 locale**
(`locale` = `language-REGION`, e.g. `pl-PL`). The Settings **Language** picker
sets it; the **Region** half keeps steering date, number and currency formatting
independently, so the two can be mixed freely (English text with Polish number
formatting, say). The picker offers every European language because the choice
also drives date/number formatting — the ones without a translation file fall
back to English UI text and say so beneath the picker.

## Where the files live

| Surface | Language files | Loader | Language source |
|---|---|---|---|
| **Web App** (Vue) | `Web App/web/src/i18n/{en,pl,da}.json` | `Web App/web/src/i18n/index.js` | signed-in profile `locale` (reactive `prefs`) |
| **API Server panel** (Vue) | `API Server/panel/src/i18n/{en,pl,da}.json` | `API Server/panel/src/i18n/index.js` | `localStorage` (`dh-panel-lang`) — the panel has no user profile |
| **Phone App** (Flutter) | `Phone App/assets/i18n/{en,pl,da}.json` | `Phone App/lib/i18n.dart` | signed-in profile `locale` (via `AppSettings`) |

All three use the same JSON shape and the same `t()` contract, so a translator
learns one format.

## The `t()` contract

```js
t("settings.appearance.title")                 // simple lookup (dot path = JSON nesting)
t("forms.share.title", { name: car.name })     // {name} placeholder interpolation
t("dashboard.serviceRecords", { n: count })    // plural — see below
```

- **Keys** are dot paths matching the nesting in the JSON.
- **Placeholders** are named (`{name}`), never positional, so a translator can
  reorder them to suit the target grammar.
- **Plurals** are an object keyed by CLDR category, selected for the active
  language by `Intl.PluralRules` (web/panel) or `Intl.plural` (Flutter):

  ```json
  "serviceRecords": {
    "one":  "{n} service record",
    "other": "{n} service records"
  }
  ```

  This is why Polish works: it needs `one` / `few` / `many` where English has
  only `one` / `other`, and a naive `n === 1` check would get "5 samochodów"
  wrong. Polish files therefore carry all four forms.

- The web/panel loaders also expose `tSplit(key, name)` for the few strings that
  wrap one value in its own markup (a monospace URL, a bolded car name). It
  returns `{ before, after }` around the placeholder so the value keeps its
  styling without splitting the sentence into word-order-assuming fragments or
  putting a translated string on a `v-html` path.

## Adding a language

1. **Copy `en.json` to `<code>.json`** in each surface you want to cover
   (`fr.json`, say) and translate the string values. Keep the keys and the
   `{placeholders}` unchanged. For a language with more plural categories than
   English, expand the plural objects (`one`/`few`/`many`/`other` as CLDR
   requires for that language).
2. **Register it** in the loader's `MESSAGES` map / `translatedLanguages` list:
   - Web: `Web App/web/src/i18n/index.js` — add to the `import`s and `MESSAGES`.
   - Panel: `API Server/panel/src/i18n/index.js` — same.
   - Phone: `Phone App/lib/i18n.dart` — add the code to `translatedLanguages`
     (the file is loaded from `assets/i18n/` automatically; it's covered by the
     `assets/i18n/` directory entry in `pubspec.yaml`).
3. The Settings picker already lists every European language, so the new one
   becomes selectable immediately and the "not translated yet" hint disappears
   for it. Untranslated keys still fall back to English.

No screen code changes are needed to add a language.

## Coverage

- **Web App** — fully translated (every view, component, form, and the status
  labels in `lib/format.js`).
- **API Server panel** — UI chrome, cards, login, status, and the API section
  titles are translated. The individual REST endpoint **descriptions** in the
  API reference table are intentionally left in English as developer reference
  documentation.
- **Phone App** — the i18n system plus the core flows are translated: navigation,
  login, lock screen, dashboard, the full Settings panel (including the language
  picker), and all status/badge wording in `lib/format.dart`. The remaining
  detail screens (car detail, record form sheets, admin users, car form sheet,
  attachment field) still render in English via the fallback until their strings
  are extracted — the pattern to follow is identical to the screens already done.