Localization

The web interface uses JSON language packs from lang/. Language files are discovered at Rust build time and embedded in the application binary.

English (lang/en.json) is required and is always the fallback language. Polish (lang/pl.json) is included by default.

Add a language

Copy lang/en.json to a file named with the new language code, for example lang/de.json.
Update the meta object.
Translate values inside translations. Do not rename translation keys.
Run ./scripts/dev.sh --check or build the project again.
Start the rebuilt binary. The new language appears automatically in the language selector.

Example structure:

{
  "meta": {
    "code": "de",
    "name": "German",
    "native_name": "Deutsch",
    "locale": "de-DE"
  },
  "translations": {
    "controls.language": "Sprache",
    "controls.theme": "Darstellung"
  }
}

The filename and meta.code must match (de.json -> "code": "de"). File names may contain ASCII letters, digits, - and _ only.

Fallback behavior

A language pack does not have to duplicate every English key while it is being developed. If a key is missing from the selected language, the UI uses the value from en.json. If a key is also missing from English, the translation key itself is shown, which makes incomplete strings visible during development.

Build-time validation

build.rs checks that:

at least one JSON language file exists,
en.json exists,
every language file contains valid JSON,
every file has meta.code, meta.name, meta.native_name and meta.locale,
meta.code matches the filename,
translations is a JSON object.

A malformed language pack fails the Rust build instead of producing a broken selector at runtime.

Runtime endpoints

The embedded language catalog is available at:

GET /lang/index.json

Individual embedded packs are available at:

GET /lang/en.json
GET /lang/pl.json
GET /lang/<code>.json

These endpoints are intentionally public so that localization also works before API authentication is completed.

Browser preference

The selected language code is stored for one year in the gree_controller_language cookie. If the stored language is no longer present in a later build, the UI falls back to English.

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