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

const ThemeContext = createContext();

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

export const ThemeProvider = ({ children }) => {
  const [isDark, setIsDark] = useState(() => {
    const savedTheme = localStorage.getItem('theme');
    return savedTheme ? savedTheme === 'dark' : 
           window.matchMedia('(prefers-color-scheme: dark)').matches;
  });

  useEffect(() => {
    if (isDark) {
      document.documentElement.classList.add('dark');
    } else {
      document.documentElement.classList.remove('dark');
    }
    localStorage.setItem('theme', isDark ? 'dark' : 'light');
  }, [isDark]);

  const toggleTheme = () => {
    setIsDark(!isDark);
  };

  const value = {
    isDark,
    toggleTheme
  };

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