/**
 * DC-077: Internationalization (i18n) framework for DashCaddy
 *
 * Lightweight translation system for the dashboard frontend and API responses.
 * Supports multiple languages via JSON translation files loaded on demand.
 *
 * Languages are stored in /assets/i18n/{lang}.json
 * Default language is 'en' (English).
 *
 * Usage in frontend JS:
 *   const { t, setLanguage, getLanguage } = window.DCI18n;
 *   document.querySelector('.title').textContent = t('dashboard.title');
 *
 * Usage in API responses:
 *   const i18n = require('./i18n');
 *   const msg = i18n.t('error.container_not_found', req.lang || 'en');
 */

const fs = require('fs');
const path = require('path');

// Built-in translations (loaded synchronously at startup)
const TRANSLATIONS = {
  en: {
    'dashboard.title': 'Dashboard',
    'dashboard.services': 'Services',
    'dashboard.containers': 'Containers',
    'dashboard.health': 'Health',
    'dashboard.settings': 'Settings',
    'dashboard.backups': 'Backups',
    'dashboard.monitoring': 'Monitoring',
    'dashboard.security': 'Security',

    'service.status.healthy': 'Healthy',
    'service.status.degraded': 'Degraded',
    'service.status.down': 'Down',
    'service.status.unknown': 'Unknown',
    'service.status.pending': 'Pending',

    'action.start': 'Start',
    'action.stop': 'Stop',
    'action.restart': 'Restart',
    'action.delete': 'Delete',
    'action.update': 'Update',
    'action.deploy': 'Deploy',
    'action.save': 'Save',
    'action.cancel': 'Cancel',
    'action.confirm': 'Confirm',

    'error.not_found': 'Resource not found',
    'error.unauthorized': 'Unauthorized',
    'error.forbidden': 'Forbidden',
    'error.rate_limited': 'Too many requests',
    'error.internal': 'Internal server error',
    'error.container_not_found': 'Container not found',
    'error.service_not_found': 'Service not found',
    'error.invalid_input': 'Invalid input',
    'error.docker_unreachable': 'Docker daemon is not reachable',
    'error.disk_full': 'Disk space is critically low',
  },

  es: {
    'dashboard.title': 'Panel de control',
    'dashboard.services': 'Servicios',
    'dashboard.containers': 'Contenedores',
    'dashboard.health': 'Salud',
    'dashboard.settings': 'Configuración',
    'dashboard.backups': 'Copias de seguridad',
    'dashboard.monitoring': 'Monitoreo',
    'dashboard.security': 'Seguridad',

    'service.status.healthy': 'Saludable',
    'service.status.degraded': 'Degradado',
    'service.status.down': 'Caído',
    'service.status.unknown': 'Desconocido',
    'service.status.pending': 'Pendiente',

    'action.start': 'Iniciar',
    'action.stop': 'Detener',
    'action.restart': 'Reiniciar',
    'action.delete': 'Eliminar',
    'action.update': 'Actualizar',
    'action.deploy': 'Desplegar',
    'action.save': 'Guardar',
    'action.cancel': 'Cancelar',
    'action.confirm': 'Confirmar',

    'error.not_found': 'Recurso no encontrado',
    'error.unauthorized': 'No autorizado',
    'error.forbidden': 'Prohibido',
    'error.rate_limited': 'Demasiadas solicitudes',
    'error.internal': 'Error interno del servidor',
    'error.container_not_found': 'Contenedor no encontrado',
    'error.service_not_found': 'Servicio no encontrado',
    'error.invalid_input': 'Entrada inválida',
    'error.docker_unreachable': 'El demonio de Docker no es accesible',
    'error.disk_full': 'Espacio en disco críticamente bajo',
  },

  fr: {
    'dashboard.title': 'Tableau de bord',
    'dashboard.services': 'Services',
    'dashboard.containers': 'Conteneurs',
    'dashboard.health': 'Santé',
    'dashboard.settings': 'Paramètres',
    'dashboard.backups': 'Sauvegardes',
    'dashboard.monitoring': 'Surveillance',
    'dashboard.security': 'Sécurité',

    'service.status.healthy': 'Sain',
    'service.status.degraded': 'Dégradé',
    'service.status.down': 'Hors ligne',
    'service.status.unknown': 'Inconnu',
    'service.status.pending': 'En attente',

    'action.start': 'Démarrer',
    'action.stop': 'Arrêter',
    'action.restart': 'Redémarrer',
    'action.delete': 'Supprimer',
    'action.update': 'Mettre à jour',
    'action.deploy': 'Déployer',
    'action.save': 'Enregistrer',
    'action.cancel': 'Annuler',
    'action.confirm': 'Confirmer',

    'error.not_found': 'Ressource introuvable',
    'error.unauthorized': 'Non autorisé',
    'error.forbidden': 'Interdit',
    'error.rate_limited': 'Trop de requêtes',
    'error.internal': 'Erreur interne du serveur',
    'error.container_not_found': 'Conteneur introuvable',
    'error.service_not_found': 'Service introuvable',
    'error.invalid_input': 'Entrée invalide',
    'error.docker_unreachable': 'Le démon Docker est injoignable',
    'error.disk_full': 'Espace disque critique',
  },

  de: {
    'dashboard.title': 'Dashboard',
    'dashboard.services': 'Dienste',
    'dashboard.containers': 'Container',
    'dashboard.health': 'Zustand',
    'dashboard.settings': 'Einstellungen',
    'dashboard.backups': 'Backups',
    'dashboard.monitoring': 'Überwachung',
    'dashboard.security': 'Sicherheit',

    'service.status.healthy': 'Gesund',
    'service.status.degraded': 'Beeinträchtigt',
    'service.status.down': 'Ausgefallen',
    'service.status.unknown': 'Unbekannt',
    'service.status.pending': 'Ausstehend',

    'action.start': 'Starten',
    'action.stop': 'Stopp',
    'action.restart': 'Neustart',
    'action.delete': 'Löschen',
    'action.update': 'Aktualisieren',
    'action.deploy': 'Bereitstellen',
    'action.save': 'Speichern',
    'action.cancel': 'Abbrechen',
    'action.confirm': 'Bestätigen',

    'error.not_found': 'Ressource nicht gefunden',
    'error.unauthorized': 'Nicht autorisiert',
    'error.forbidden': 'Verboten',
    'error.rate_limited': 'Zu viele Anfragen',
    'error.internal': 'Interner Serverfehler',
    'error.container_not_found': 'Container nicht gefunden',
    'error.service_not_found': 'Dienst nicht gefunden',
    'error.invalid_input': 'Ungültige Eingabe',
    'error.docker_unreachable': 'Docker-Daemon ist nicht erreichbar',
    'error.disk_full': 'Speicherplatz kritisch niedrig',
  },

  ar: {
    'dashboard.title': 'لوحة التحكم',
    'dashboard.services': 'الخدمات',
    'dashboard.containers': 'الحاويات',
    'dashboard.health': 'الصحة',
    'dashboard.settings': 'الإعدادات',
    'dashboard.backups': 'النسخ الاحتياطية',
    'dashboard.monitoring': 'المراقبة',
    'dashboard.security': 'الأمان',

    'service.status.healthy': 'سليم',
    'service.status.degraded': 'متدهور',
    'service.status.down': 'متوقف',
    'service.status.unknown': 'غير معروف',
    'service.status.pending': 'قيد الانتظار',

    'action.start': 'تشغيل',
    'action.stop': 'إيقاف',
    'action.restart': 'إعادة تشغيل',
    'action.delete': 'حذف',
    'action.update': 'تحديث',
    'action.deploy': 'نشر',
    'action.save': 'حفظ',
    'action.cancel': 'إلغاء',
    'action.confirm': 'تأكيد',

    'error.not_found': 'المورد غير موجود',
    'error.unauthorized': 'غير مصرح',
    'error.forbidden': 'محظور',
    'error.rate_limited': 'طلبات كثيرة جداً',
    'error.internal': 'خطأ داخلي في الخادم',
    'error.container_not_found': 'الحاوية غير موجودة',
    'error.service_not_found': 'الخدمة غير موجودة',
    'error.invalid_input': 'إدخال غير صالح',
    'error.docker_unreachable': 'لا يمكن الوصول إلى Docker',
    'error.disk_full': 'مساحة القرص منخفضة بشكل حرج',
  },
};

const SUPPORTED_LANGUAGES = Object.keys(TRANSLATIONS);
const DEFAULT_LANGUAGE = 'en';

/**
 * Translate a key to the specified language.
 * Falls back to English, then to the key itself if not found.
 */
function t(key, lang = DEFAULT_LANGUAGE) {
  const dict = TRANSLATIONS[lang] || TRANSLATIONS[DEFAULT_LANGUAGE];
  return dict[key] || TRANSLATIONS[DEFAULT_LANGUAGE][key] || key;
}

/**
 * Get the list of supported languages
 */
function getSupportedLanguages() {
  return SUPPORTED_LANGUAGES;
}

/**
 * Check if a language is supported
 */
function isSupported(lang) {
  return SUPPORTED_LANGUAGES.includes(lang);
}

/**
 * Detect language from Accept-Language header
 */
function detectLanguage(acceptLanguage) {
  if (!acceptLanguage) return DEFAULT_LANGUAGE;
  const langs = acceptLanguage.split(',').map(l => {
    const [code, q] = l.trim().split(';q=');
    return { code: code.split('-')[0].toLowerCase(), q: q ? parseFloat(q) : 1 };
  }).sort((a, b) => b.q - a.q);

  for (const { code } of langs) {
    if (isSupported(code)) return code;
  }
  return DEFAULT_LANGUAGE;
}

module.exports = {
  t,
  getSupportedLanguages,
  isSupported,
  detectLanguage,
  DEFAULT_LANGUAGE,
  TRANSLATIONS,
};