/**
 * data-i18n 속성 기반 페이지 번역
 */
(function initPageI18n() {
    /**
     * @returns {Promise<string>}
     */
    function getLang() {
        const fromQuery = new URLSearchParams(window.location.search).get('lang');
        if (fromQuery) return fromQuery;
        return localStorage.getItem('lang') || 'ko';
    }

    /**
     * @param {string} lang
     * @returns {Promise<object>}
     */
    async function loadTranslations(lang) {
        try {
            const res = await fetch(`/i18n/translations.${lang}.json`);
            if (!res.ok) return {};
            return await res.json();
        } catch {
            return {};
        }
    }

    let cachedTranslations = {};

    /**
     * @param {string} key
     * @param {string} [fallback]
     * @returns {string}
     */
    function t(key, fallback = '') {
        return cachedTranslations[key] || fallback;
    }

    /**
     * @param {object} translations
     */
    function applyTranslations(translations) {
        document.querySelectorAll('[data-i18n]').forEach((el) => {
            const key = el.dataset.i18n;
            if (translations[key]) el.textContent = translations[key];
        });
        document.querySelectorAll('[data-i18n-html]').forEach((el) => {
            const key = el.dataset.i18nHtml;
            if (translations[key]) el.innerHTML = translations[key];
        });
        document.querySelectorAll('[data-i18n-placeholder]').forEach((el) => {
            const key = el.dataset.i18nPlaceholder;
            if (translations[key]) el.placeholder = translations[key];
        });
        if (window.UaPageHelp?.bindPageHelp) {
            window.UaPageHelp.bindPageHelp(translations);
        }
    }

    async function applyPageI18n() {
        const lang = await getLang();
        cachedTranslations = await loadTranslations(lang);
        applyTranslations(cachedTranslations);
        return cachedTranslations;
    }

    document.addEventListener('DOMContentLoaded', () => {
        applyPageI18n();
    });

    window.UaPageI18n = { applyPageI18n, getLang, loadTranslations, t };
})();