src/app/hooks/useTheme.ts

import { useState, useEffect } from 'react';

type Theme = 'light' | 'dark';

const THEME_STORAGE_KEY = 'app-theme';

export const useTheme = () => {
  const [theme, setTheme] = useState(() => {
    // Get theme from localStorage or default to 'dark'
    if (typeof window !== 'undefined') {
      const stored = localStorage.getItem(THEME_STORAGE_KEY) as Theme | null;
      return stored || 'dark';
    }
    return 'dark';
  }) as [Theme, (value: Theme | ((prev: Theme) => Theme)) => void];

  useEffect(() => {
    // Apply theme to document
    const root = document.documentElement;
    if (theme === 'dark') {
      root.classList.add('dark');
    } else {
      root.classList.remove('dark');
    }
    // Save to localStorage
    localStorage.setItem(THEME_STORAGE_KEY, theme);
  }, [theme]);

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

  return { theme, toggleTheme, setTheme };
};