/**
 * Simple i18n system for Tractatus
 * Supports: en (English), de (German), fr (French), mi (Te Reo Māori - coming soon)
 */

const I18n = {
  currentLang: 'en',
  translations: {},
  supportedLanguages: ['en', 'de', 'fr'],
  
  async init() {
    // 1. Detect language preference
    this.currentLang = this.detectLanguage();
    
    // 2. Load translations
    await this.loadTranslations(this.currentLang);
    
    // 3. Apply to page
    this.applyTranslations();
    
    // 4. Update language selector if present
    this.updateLanguageSelector();
    
    console.log(`[i18n] Initialized with language: ${this.currentLang}`);
  },
  
  detectLanguage() {
    // Check localStorage first
    const saved = localStorage.getItem('tractatus-lang');
    if (saved && this.supportedLanguages.includes(saved)) {
      return saved;
    }
    
    // Check browser language
    const browserLang = (navigator.language || navigator.userLanguage).split('-')[0];
    if (this.supportedLanguages.includes(browserLang)) {
      return browserLang;
    }
    
    // Default to English
    return 'en';
  },
  
  detectPageName() {
    // Try to get page name from data attribute first
    const pageAttr = document.documentElement.getAttribute('data-page');
    if (pageAttr) {
      return pageAttr;
    }

    // Detect from URL path
    const path = window.location.pathname;

    // Map paths to translation file names
    const pageMap = {
      '/': 'homepage',
      '/index.html': 'homepage',
      '/researcher.html': 'researcher',
      '/leader.html': 'leader',
      '/implementer.html': 'implementer',
      '/about.html': 'about',
      '/faq.html': 'faq'
    };

    return pageMap[path] || 'homepage';
  },

  async loadTranslations(lang) {
    try {
      const pageName = this.detectPageName();
      const response = await fetch(`/locales/${lang}/${pageName}.json`);
      if (!response.ok) {
        throw new Error(`Failed to load translations for ${lang}/${pageName}`);
      }
      this.translations = await response.json();
      console.log(`[i18n] Loaded translations for page: ${pageName}`);
    } catch (error) {
      console.error(`[i18n] Error loading translations:`, error);
      // Fallback to English if loading fails
      if (lang !== 'en') {
        this.currentLang = 'en';
        await this.loadTranslations('en');
      }
    }
  },
  
  t(key) {
    const keys = key.split('.');
    let value = this.translations;
    
    for (const k of keys) {
      if (value && typeof value === 'object') {
        value = value[k];
      } else {
        return key; // Return key if translation not found
      }
    }
    
    return value || key;
  },
  
  applyTranslations() {
    // Find all elements with data-i18n attribute
    document.querySelectorAll('[data-i18n]').forEach(el => {
      const key = el.dataset.i18n;
      const translation = this.t(key);
      
      if (typeof translation === 'string') {
        el.textContent = translation;
      }
    });
    
    // Handle data-i18n-html for HTML content
    document.querySelectorAll('[data-i18n-html]').forEach(el => {
      const key = el.dataset.i18nHtml;
      const translation = this.t(key);
      
      if (typeof translation === 'string') {
        el.innerHTML = translation;
      }
    });
  },
  
  async setLanguage(lang) {
    if (!this.supportedLanguages.includes(lang)) {
      console.error(`[i18n] Unsupported language: ${lang}`);
      return;
    }
    
    // Save preference
    localStorage.setItem('tractatus-lang', lang);
    
    // Update current language
    this.currentLang = lang;
    
    // Reload translations
    await this.loadTranslations(lang);
    
    // Reapply to page
    this.applyTranslations();
    
    // Update selector
    this.updateLanguageSelector();
    
    // Update HTML lang attribute
    document.documentElement.lang = lang;

    // Dispatch event for language change
    window.dispatchEvent(new CustomEvent('languageChanged', {
      detail: { language: lang }
    }));

    console.log(`[i18n] Language changed to: ${lang}`);
  },
  
  updateLanguageSelector() {
    const selector = document.getElementById('language-selector');
    if (selector) {
      selector.value = this.currentLang;
    }
  },
  
  getLanguageName(code) {
    const names = {
      'en': 'English',
      'de': 'Deutsch',
      'fr': 'Français',
      'mi': 'Te Reo Māori'
    };
    return names[code] || code;
  }
};

// Auto-initialize when DOM is ready
if (document.readyState === 'loading') {
  document.addEventListener('DOMContentLoaded', () => I18n.init());
} else {
  I18n.init();
}

// Make available globally
window.I18n = I18n;