fission-i18n

Internationalization (i18n) support for Fission applications.

This crate provides a simple, registry-based translation system. It stores locale-specific string bundles and retrieves messages by key and locale at runtime.

Core types

Locale

A newtype wrapper around String representing a BCP 47 locale identifier (e.g., "en-US", "ja-JP"). Defaults to "en-US".

use fission_i18n::Locale;

let locale = Locale::default();          // "en-US"
let locale = Locale::from("fr-FR");      // French
let locale = Locale("de-DE".to_string()); // German

TranslationBundle

A collection of key-value message pairs for a single locale. Load these from JSON, TOML, or construct them programmatically.

use fission_i18n::{TranslationBundle, Locale};
use std::collections::HashMap;

let bundle = TranslationBundle {
    locale: Locale::from("es-ES"),
    messages: HashMap::from([
        ("greeting".to_string(), "Hola".to_string()),
        ("farewell".to_string(), "Adios".to_string()),
    ]),
};

I18nRegistry

The central registry that holds all translation bundles. Supports multiple locales simultaneously and merges bundles for the same locale (later entries overwrite earlier ones for the same key).

use fission_i18n::{I18nRegistry, TranslationBundle, Locale};

let mut registry = I18nRegistry::new();
registry.add_bundle(english_bundle);
registry.add_bundle(spanish_bundle);

let locale = Locale::from("es-ES");
let greeting = registry.get(&locale, "greeting"); // Some("Hola")
let missing = registry.get(&locale, "unknown");   // None

Serialization

All types implement Serialize and Deserialize, so bundles can be loaded from JSON files:

{
  "locale": "ja-JP",
  "messages": {
    "save": "保存",
    "cancel": "キャンセル",
    "delete": "削除"
  }
}

Design notes

• The registry uses HashMap<Locale, HashMap<String, String>> internally.
• Lookups are O(1) per locale and O(1) per key.
• There is no fallback chain (e.g., en-US does not fall back to en). The caller is responsible for implementing fallback logic if needed.
• The registry is not global -- it is owned by the application and passed through the Env or state.