basil/packages/web/src/contexts/ThemeContext.tsx

import { createContext, useContext, useState, useEffect, ReactNode } from 'react';

type Theme = 'light' | 'dark';

interface ThemeContextType {
  theme: Theme;
  toggleTheme: () => void;
}

const ThemeContext = createContext<ThemeContextType | undefined>(undefined);

const THEME_STORAGE_KEY = 'basil_theme';

export function ThemeProvider({ children }: { children: ReactNode }) {
  const [theme, setTheme] = useState<Theme>(() => {
    // Load theme from localStorage safely
    try {
      const saved = localStorage.getItem(THEME_STORAGE_KEY);
      return (saved === 'dark' ? 'dark' : 'light') as Theme;
    } catch (e) {
      return 'light';
    }
  });

  useEffect(() => {
    // Apply theme to document
    document.documentElement.setAttribute('data-theme', theme);
    // Save to localStorage safely
    try {
      localStorage.setItem(THEME_STORAGE_KEY, theme);
    } catch (e) {
      console.warn('Failed to save theme preference:', e);
    }
  }, [theme]);

  const toggleTheme = () => {
    setTheme(prev => prev === 'light' ? 'dark' : 'light');
  };

  return (
    <ThemeContext.Provider value={{ theme, toggleTheme }}>
      {children}
    </ThemeContext.Provider>
  );
}

export function useTheme() {
  const context = useContext(ThemeContext);
  if (context === undefined) {
    throw new Error('useTheme must be used within a ThemeProvider');
  }
  return context;
}