/**
 * Frontend internationalization (i18n) service
 * Provides translation support for client-side JavaScript
 */

class I18nService {
  constructor() {
    this.translations = new Map();
    this.defaultLocale = 'en';
    this.availableLocales = ['en', 'es-MX'];
    this.currentLocale = this.getStoredLocale() || this.detectBrowserLocale();
  }

  /**
   * Load translation data from the server
   */
  async loadTranslations() {
    for (const locale of this.availableLocales) {
      try {
        const response = await fetch(`/api/i18n/${locale}`);
        if (response.ok) {
          const translations = await response.json();
          this.translations.set(locale, translations);
          console.log(`Loaded translations for locale: ${locale}`);
        }
      } catch (error) {
        console.error(`Failed to load translations for locale ${locale}:`, error);
      }
    }
    
    // Trigger translation update after loading
    this.updatePageTranslations();
    
    // Create language selector after translations are loaded
    this.createLanguageSelector('language-selector-container');
  }

  /**
   * Get a translated string by key path
   */
  t(keyPath, locale = null, params = null) {
    const targetLocale = locale || this.currentLocale;
    const translations = this.translations.get(targetLocale) || this.translations.get(this.defaultLocale);
    
    if (!translations) {
      console.warn(`No translations found for locale: ${targetLocale}`);
      return keyPath;
    }

    const keys = keyPath.split('.');
    let value = translations;

    for (const key of keys) {
      value = value?.[key];
      if (value === undefined) {
        // Fallback to default locale if key not found
        if (targetLocale !== this.defaultLocale) {
          return this.t(keyPath, this.defaultLocale, params);
        }
        console.warn(`Translation key not found: ${keyPath} for locale: ${targetLocale}`);
        return keyPath;
      }
    }

    if (typeof value !== 'string') {
      console.warn(`Translation value is not a string for key: ${keyPath}`);
      return keyPath;
    }

    // Replace parameters if provided
    if (params) {
      return this.replaceParams(value, params);
    }

    return value;
  }

  /**
   * Replace parameters in translation strings
   */
  replaceParams(text, params) {
    return text.replace(/\{\{(\w+)\}\}/g, (match, key) => {
      return params[key] || match;
    });
  }

  /**
   * Set the current locale and update the UI
   */
  async setLocale(locale) {
    if (!this.availableLocales.includes(locale)) {
      console.warn(`Unsupported locale: ${locale}`);
      return;
    }

    this.currentLocale = locale;
    this.storeLocale(locale);
    
    // Update HTML lang attribute
    document.documentElement.lang = locale;
    
    // Update page translations
    this.updatePageTranslations();
    
    // Trigger custom event for components to update
    window.dispatchEvent(new CustomEvent('localeChanged', { detail: { locale } }));
  }

  /**
   * Get current locale
   */
  getLocale() {
    return this.currentLocale;
  }

  /**
   * Get available locales
   */
  getAvailableLocales() {
    return [...this.availableLocales];
  }

  /**
   * Get locale display name
   */
  getLocaleDisplayName(locale) {
    const displayNames = {
      'en': 'English',
      'es-MX': 'Español (México)'
    };
    return displayNames[locale] || locale;
  }

  /**
   * Detect browser's preferred locale
   */
  detectBrowserLocale() {
    const browserLang = navigator.language || navigator.languages?.[0];
    
    if (!browserLang) {
      return this.defaultLocale;
    }

    // Check for exact match first
    if (this.availableLocales.includes(browserLang)) {
      return browserLang;
    }
    
    // Check for language match (e.g., "es" matches "es-MX")
    const languageCode = browserLang.split('-')[0];
    const matchingLocale = this.availableLocales.find(locale => 
      locale.startsWith(languageCode)
    );
    
    return matchingLocale || this.defaultLocale;
  }

  /**
   * Store locale preference in localStorage
   */
  storeLocale(locale) {
    try {
      localStorage.setItem('preferredLocale', locale);
    } catch (error) {
      console.warn('Failed to store locale preference:', error);
    }
  }

  /**
   * Get stored locale preference from localStorage
   */
  getStoredLocale() {
    try {
      return localStorage.getItem('preferredLocale');
    } catch (error) {
      console.warn('Failed to get stored locale preference:', error);
      return null;
    }
  }

  /**
   * Update page translations using data-i18n attributes
   */
  updatePageTranslations() {
    // Update elements with data-i18n attribute
    document.querySelectorAll('[data-i18n]').forEach(element => {
      const key = element.getAttribute('data-i18n');
      const translation = this.t(key);
      
      if (element.tagName === 'INPUT' && (element.type === 'text' || element.type === 'password')) {
        element.placeholder = translation;
      } else if (element.hasAttribute('title')) {
        element.title = translation;
      } else {
        element.textContent = translation;
      }
    });

    // Update elements with data-i18n-placeholder attribute
    document.querySelectorAll('[data-i18n-placeholder]').forEach(element => {
      const key = element.getAttribute('data-i18n-placeholder');
      const translation = this.t(key);
      element.placeholder = translation;
    });

    // Update elements with data-i18n-html attribute (for HTML content)
    document.querySelectorAll('[data-i18n-html]').forEach(element => {
      const key = element.getAttribute('data-i18n-html');
      const translation = this.t(key);
      element.innerHTML = translation;
    });

    // Update page title if it has translation
    const titleElement = document.querySelector('title[data-i18n]');
    if (titleElement) {
      const key = titleElement.getAttribute('data-i18n');
      document.title = this.t(key);
    }

    // Update meta description if it has translation
    const metaDescription = document.querySelector('meta[name="description"][data-i18n]');
    if (metaDescription) {
      const key = metaDescription.getAttribute('data-i18n');
      metaDescription.content = this.t(key);
    }
  }

  /**
   * Create language selector dropdown
   */
  createLanguageSelector(containerId) {
    const container = document.getElementById(containerId);
    if (!container) {
      console.warn(`Container with id "${containerId}" not found`);
      return;
    }

    // Clear container first in case it's being recreated
    container.innerHTML = '';

    const select = document.createElement('select');
    select.id = 'language-selector';
    select.className = 'language-selector';
    
    // Use fallback title if translations not loaded yet
    const titleText = this.translations.size > 0 ? this.t('common.selectLanguage') : 'Select language';
    select.title = titleText;

    // Add options for each available locale
    this.availableLocales.forEach(locale => {
      const option = document.createElement('option');
      option.value = locale;
      option.textContent = this.getLocaleDisplayName(locale);
      option.selected = locale === this.currentLocale;
      select.appendChild(option);
    });

    // Add change event listener
    select.addEventListener('change', (event) => {
      this.setLocale(event.target.value);
    });

    container.appendChild(select);
  }
}

// Create global instance
window.i18n = new I18nService();

// Helper function for easier access
window.t = function(keyPath, locale = null, params = null) {
  return window.i18n.t(keyPath, locale, params);
};

// Auto-initialize when DOM is ready
if (document.readyState === 'loading') {
  document.addEventListener('DOMContentLoaded', () => {
    window.i18n.loadTranslations();
  });
} else {
  window.i18n.loadTranslations();
}