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

type Theme = 'light' | 'dark';

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

export const ThemeContext = createContext<ThemeContextValue | null>(null);

interface ThemeProviderProps {
  children: ReactNode;
}

const getInitialTheme = (): Theme => {
  const stored = localStorage.getItem('theme');
  if (stored === 'light' || stored === 'dark') {
    return stored;
  }
  return window.matchMedia('(prefers-color-scheme: dark)').matches ? 'dark' : 'light';
};

const ThemeProvider = ({ children }: ThemeProviderProps) => {
  const [theme, setTheme] = useState<Theme>(getInitialTheme);

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

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

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

export default ThemeProvider;