i18n.js

/**
 * Tiny i18n layer shared by popup + content scripts.
 *
 * Source of truth is the existing _locales/<locale>/messages.json files
 * (also used by manifest __MSG__). At runtime we fetch the active locale's
 * JSON from chrome.runtime.getURL and cache it.
 *
 * Active locale resolution:
 *   1. user-selected override in chrome.storage.sync ('cgpt-sidebar-locale')
 *   2. browser UI language (chrome.i18n.getUILanguage), mapped to a
 *      supported locale
 *   3. fall back to 'en'
 *
 * Exposes window.__veilbar = { init, t, locale, setLocale, onChange, SUPPORTED }.
 */
(() => {
  const SUPPORTED = ['en', 'zh_CN', 'ja', 'hi'];
  const STORAGE_KEY = 'cgpt-sidebar-locale';

  let activeLocale = 'en';
  const cache = {};
  const listeners = [];

  function detectFromUI() {
    const ui = (chrome.i18n && chrome.i18n.getUILanguage
      ? chrome.i18n.getUILanguage()
      : 'en'
    ).toLowerCase();
    if (ui.startsWith('zh')) return 'zh_CN';
    if (ui.startsWith('ja')) return 'ja';
    if (ui.startsWith('hi')) return 'hi';
    return 'en';
  }

  async function loadMessages(locale) {
    if (cache[locale]) return cache[locale];
    try {
      const url = chrome.runtime.getURL(`_locales/${locale}/messages.json`);
      const r = await fetch(url);
      if (!r.ok) return null;
      const data = await r.json();
      cache[locale] = data;
      return data;
    } catch {
      return null;
    }
  }

  async function init() {
    try {
      const r = await chrome.storage.sync.get(STORAGE_KEY);
      const stored = r[STORAGE_KEY];
      if (stored && stored !== 'auto' && SUPPORTED.includes(stored)) {
        activeLocale = stored;
      } else {
        activeLocale = detectFromUI();
      }
    } catch {
      activeLocale = detectFromUI();
    }
    await loadMessages(activeLocale);
    if (activeLocale !== 'en') await loadMessages('en');
    return activeLocale;
  }

  function t(key, substitution) {
    const dict = cache[activeLocale];
    let entry = dict && dict[key];
    if (!entry) entry = (cache.en || {})[key];
    if (!entry) return key;
    let msg = entry.message;
    if (substitution != null) {
      msg = msg.replace(/\$[A-Za-z]+\$/g, () => substitution);
    }
    return msg;
  }

  function locale() { return activeLocale; }

  async function setLocale(newLocale) {
    if (newLocale === 'auto') {
      activeLocale = detectFromUI();
      try { await chrome.storage.sync.remove(STORAGE_KEY); } catch {}
    } else if (SUPPORTED.includes(newLocale)) {
      activeLocale = newLocale;
      try { await chrome.storage.sync.set({ [STORAGE_KEY]: newLocale }); } catch {}
    } else {
      return;
    }
    await loadMessages(activeLocale);
    listeners.forEach(cb => { try { cb(activeLocale); } catch {} });
  }

  function onChange(cb) { listeners.push(cb); }

  chrome.storage.onChanged.addListener(async (changes, area) => {
    if (area !== 'sync' || !changes[STORAGE_KEY]) return;
    const newVal = changes[STORAGE_KEY].newValue;
    if (newVal == null || newVal === 'auto') {
      activeLocale = detectFromUI();
    } else if (SUPPORTED.includes(newVal)) {
      activeLocale = newVal;
    }
    await loadMessages(activeLocale);
    listeners.forEach(cb => { try { cb(activeLocale); } catch {} });
  });

  window.__veilbar = { init, t, locale, setLocale, onChange, SUPPORTED };
})();