// Lightweight i18n loader. Translation data lives in `i18n/<lang>.json`, one
// file per language so translators can edit each file independently.

const I18N_AVAILABLE = ["en", "de", "pl", "ru", "fr", "es", "pt"];
const I18N_NAMES = {
  en: "English", de: "Deutsch", pl: "Polski", ru: "Русский",
  fr: "Français", es: "Español", pt: "Português"
};
const I18N_BASE_PATH = "i18n";

const I18N_DATA = {};
const I18N_PENDING = {};
let CURRENT_LANG = "en";

function i18nURL(lang) {
  return `${I18N_BASE_PATH}/${lang}.json`;
}

async function loadLang(lang) {
  if (!I18N_AVAILABLE.includes(lang)) lang = "en";
  if (I18N_DATA[lang]) return I18N_DATA[lang];
  if (I18N_PENDING[lang]) return I18N_PENDING[lang];
  const p = fetch(i18nURL(lang), { cache: "no-cache" })
    .then((r) => r.ok ? r.json() : Promise.reject(new Error("i18n_load_failed")))
    .then((data) => { I18N_DATA[lang] = data; delete I18N_PENDING[lang]; return data; })
    .catch((err) => { delete I18N_PENDING[lang]; throw err; });
  I18N_PENDING[lang] = p;
  return p;
}

async function setLang(lang) {
  if (!I18N_AVAILABLE.includes(lang)) lang = "en";
  // English is the fallback for missing keys, so make sure it is always loaded.
  if (!I18N_DATA.en) {
    try { await loadLang("en"); } catch (e) {}
  }
  if (lang !== "en") {
    try { await loadLang(lang); } catch (e) {}
  }
  CURRENT_LANG = lang;
  document.documentElement.lang = lang;
}

function t(key, vars) {
  const d = I18N_DATA[CURRENT_LANG] || I18N_DATA.en || {};
  const fallback = I18N_DATA.en || {};
  let str = d[key] || fallback[key] || key;
  if (vars) {
    for (const k in vars) {
      str = str.replaceAll("{" + k + "}", vars[k]);
    }
  }
  return str;
}

function detectInitialLang() {
  const navLang = (navigator.language || "en").slice(0, 2);
  return I18N_AVAILABLE.includes(navLang) ? navLang : "en";
}