zeropost-web/components/ScrollToTop.js

'use client';
import { useEffect, useState } from 'react';
import { ArrowUp } from 'lucide-react';

export default function ScrollToTop() {
  const [visible, setVisible] = useState(false);

  useEffect(() => {
    const onScroll = () => setVisible(window.scrollY > 800);
    onScroll();
    window.addEventListener('scroll', onScroll, { passive: true });
    return () => window.removeEventListener('scroll', onScroll);
  }, []);

  function scrollUp() {
    window.scrollTo({ top: 0, behavior: 'smooth' });
  }

  return (
    <button
      onClick={scrollUp}
      aria-label="Наверх"
      className={`fixed z-30 right-4 sm:right-6 bottom-4 sm:bottom-6 w-11 h-11 rounded-full flex items-center justify-center shadow-lg transition-all ${visible ? 'opacity-100 translate-y-0' : 'opacity-0 translate-y-4 pointer-events-none'}`}
      style={{
        background: 'rgb(var(--accent))',
        color: 'white',
        marginBottom: 'env(safe-area-inset-bottom)',
      }}
    >
      <ArrowUp className="w-5 h-5" />
    </button>
  );
}