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

type Theme = 'dark' | 'light';

const STORAGE_KEY = 'sz_theme';

function getInitial(): Theme {
  try {
    const saved = localStorage.getItem(STORAGE_KEY);
    if (saved === 'light' || saved === 'dark') return saved;
  } catch { /* localStorage unavailable */ }
  return window.matchMedia?.('(prefers-color-scheme: light)').matches ? 'light' : 'dark';
}

function applyTheme(theme: Theme) {
  document.documentElement.setAttribute('data-theme', theme);
  const metaTheme = document.querySelector('meta[name="theme-color"]');
  if (metaTheme) {
    metaTheme.setAttribute('content', theme === 'dark' ? '#0c1c22' : '#f8f9fa');
  }
}

export function useTheme() {
  const [theme, setTheme] = useState<Theme>(getInitial);

  useEffect(() => {
    applyTheme(theme);
    try { localStorage.setItem(STORAGE_KEY, theme); } catch { /* ignore */ }
  }, [theme]);

  const toggleTheme = useCallback(() => {
    setTheme(t => t === 'dark' ? 'light' : 'dark');
  }, []);

  return { theme, toggleTheme };
}