frontend/src/components/layout/AppShell.tsx

import { type ReactNode, useEffect } from 'react';
import { NavLink } from 'react-router-dom';
import { useTranslation } from 'react-i18next';
import { useUIStore } from '../../store/uiStore';
import './AppShell.css';

interface Props {
  children: ReactNode;
}

const NAV_ITEMS = [
  { path: '/', translationKey: 'appshell.nav.home', icon: <img src="/favicon.svg" alt="HTP" style={{ width: '1.2em', height: '1.2em', display: 'block' }} /> },
  { path: '/data-collection', translationKey: 'appshell.nav.data_collection', icon: '📊' },
  { path: '/potential-analysis', translationKey: 'appshell.nav.potential_analysis', icon: '📈' },
];

export default function AppShell({ children }: Props) {
  const { t, i18n } = useTranslation();
  const theme = useUIStore((s) => s.theme);
  const toggleTheme = useUIStore((s) => s.toggleTheme);

  const toggleLanguage = () => {
    const nextLang = i18n.language === 'en' ? 'de' : 'en';
    i18n.changeLanguage(nextLang);
    localStorage.setItem('i18nextLng', nextLang);

    // Trigger Google Translate widget
    try {
      const selectField = document.querySelector('.goog-te-combo') as HTMLSelectElement;
      if (selectField) {
        selectField.value = nextLang;
        selectField.dispatchEvent(new Event('change'));
      }
    } catch (e) {
      console.error('Google Translate trigger failed:', e);
    }
  };

  // Sync dark mode class to HTML element
  useEffect(() => {
    console.log('[HeatTransPlan] Current Theme:', theme);
    if (theme === 'dark') {
      document.documentElement.classList.add('dark');
    } else {
      document.documentElement.classList.remove('dark');
    }
  }, [theme]);

  return (
    <div className="app-shell">
      {/* Top Navigation */}
      <header className="top-nav">
        <div className="nav-brand">
          <span className="brand-text notranslate">HeatTransPlan</span>
          <span className="brand-version notranslate">v2.1.0</span>
        </div>

        <nav className="nav-links">
          {NAV_ITEMS.map((item) => (
            <NavLink
              key={item.path}
              to={item.path}
              className={({ isActive }) =>
                `nav-item ${isActive ? 'active' : ''}`
              }
              end={item.path === '/'}
              title={t(item.translationKey)}
            >
              <span className="nav-icon">{item.icon}</span>
              <span className="nav-label">{t(item.translationKey)}</span>
            </NavLink>
          ))}
        </nav>

        <div className="nav-actions">
          <button className="theme-toggle" onClick={toggleLanguage} title={i18n.language === 'en' ? 'Switch to German' : 'Switch to English'}>
            {i18n.language === 'en' ? '🇩🇪' : '🇬🇧'}
          </button>
          <button className="theme-toggle" onClick={toggleTheme} title={theme === 'dark' ? t('appshell.theme.light') : t('appshell.theme.dark')}>
            {theme === 'dark' ? '☀️' : '🌙'}
          </button>
        </div>
      </header>

      {/* Main content */}
      <main className="main-content">
        {children}
      </main>
    </div>
  );
}