src/components/BackToTopButton/index.tsx

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

import React, { useState, useEffect } from 'react';
import styles from './styles.module.css';

const BackToTopButton: React.FC = () => {
  const [isVisible, setIsVisible] = useState(false);

  // Show button when page is scrolled down
  const toggleVisibility = () => {
    if (window.pageYOffset > 300) {
      setIsVisible(true);
    } else {
      setIsVisible(false);
    }
  };

  // Set up scroll event listener
  useEffect(() => {
    window.addEventListener('scroll', toggleVisibility);
    return () => window.removeEventListener('scroll', toggleVisibility);
  }, []);

  // Scroll to top function
  const scrollToTop = () => {
    window.scrollTo({
      top: 0,
      behavior: 'smooth'
    });
  };

  return (
    <>
      {isVisible && (
        <button 
          onClick={scrollToTop} 
          className={styles.backToTop}
          aria-label="Back to top"
          title="Back to top"
        >
          <svg 
            xmlns="http://www.w3.org/2000/svg" 
            width="24" 
            height="24" 
            viewBox="0 0 24 24" 
            fill="none" 
            stroke="currentColor" 
            strokeWidth="2" 
            strokeLinecap="round" 
            strokeLinejoin="round"
          >
            <polyline points="18 15 12 9 6 15"></polyline>
          </svg>
        </button>
      )}
    </>
  );
};

export default BackToTopButton;