airbnb/caravel

/**
 * 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 { useEffect, useRef, useState, RefObject } from 'react';

export function useElementOnScreen<T extends Element>(
  options: IntersectionObserverInit,
): [RefObject<T>, boolean] {
  const containerRef = useRef<T>(null);
  const [isSticky, setIsSticky] = useState(false);

  const callback = (entries: IntersectionObserverEntry[]) => {
    const [entry] = entries;
    setIsSticky(entry.intersectionRatio < 1);
  };

  useEffect(() => {
    const observer = new IntersectionObserver(callback, options);
    const element = containerRef.current;
    if (element) {
      observer.observe(element);
    }
    return () => {
      if (element) {
        observer.unobserve(element);
      }
    };
  }, [containerRef, options]);

  return [containerRef, isSticky];
}