'use client';

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

type Theme = 'light' | 'dark';

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

const ThemeContext = createContext<ThemeContextValue>({
  theme: 'light',
  toggleTheme: () => {},
});

export function useTheme() {
  return useContext(ThemeContext);
}

const STORAGE_KEY = 'goodgo-theme';

export function ThemeProvider({ children }: { children: React.ReactNode }) {
  const [theme, setTheme] = useState<Theme>('light');

  useEffect(() => {
    const stored = localStorage.getItem(STORAGE_KEY) as Theme | null;
    if (stored === 'dark' || stored === 'light') {
      setTheme(stored);
      document.documentElement.classList.toggle('dark', stored === 'dark');
    } else if (window.matchMedia('(prefers-color-scheme: dark)').matches) {
      setTheme('dark');
      document.documentElement.classList.add('dark');
    }
  }, []);

  const toggleTheme = useCallback(() => {
    setTheme((prev) => {
      const next = prev === 'light' ? 'dark' : 'light';
      localStorage.setItem(STORAGE_KEY, next);
      document.documentElement.classList.toggle('dark', next === 'dark');
      return next;
    });
  }, []);

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