import React, { PureComponent } from 'react'; import { ScrollContainer } from 'react-router-scroll'; import PropTypes from 'prop-types'; import IntersectionObserverArticleContainer from '../containers/intersection_observer_article_container'; import LoadMore from './load_more'; import IntersectionObserverWrapper from '../features/ui/util/intersection_observer_wrapper'; import { throttle } from 'lodash'; import { List as ImmutableList } from 'immutable'; export default class ScrollableList extends PureComponent { static contextTypes = { router: PropTypes.object, }; static propTypes = { scrollKey: PropTypes.string.isRequired, onScrollToBottom: PropTypes.func, onScrollToTop: PropTypes.func, onScroll: PropTypes.func, trackScroll: PropTypes.bool, shouldUpdateScroll: PropTypes.func, isLoading: PropTypes.bool, hasMore: PropTypes.bool, prepend: PropTypes.node, emptyMessage: PropTypes.node, children: PropTypes.node, }; static defaultProps = { trackScroll: true, }; state = { lastMouseMove: null, }; intersectionObserverWrapper = new IntersectionObserverWrapper(); handleScroll = throttle(() => { if (this.node) { const { scrollTop, scrollHeight, clientHeight } = this.node; const offset = scrollHeight - scrollTop - clientHeight; this._oldScrollPosition = scrollHeight - scrollTop; if (400 > offset && this.props.onScrollToBottom && !this.props.isLoading) { this.props.onScrollToBottom(); } else if (scrollTop < 100 && this.props.onScrollToTop) { this.props.onScrollToTop(); } else if (this.props.onScroll) { this.props.onScroll(); } } }, 150, { trailing: true, }); handleMouseMove = throttle(() => { this._lastMouseMove = new Date(); }, 300); handleMouseLeave = () => { this._lastMouseMove = null; } componentDidMount () { this.attachScrollListener(); this.attachIntersectionObserver(); // Handle initial scroll posiiton this.handleScroll(); } componentDidUpdate (prevProps) { const someItemInserted = React.Children.count(prevProps.children) > 0 && React.Children.count(prevProps.children) < React.Children.count(this.props.children) && this.getFirstChildKey(prevProps) !== this.getFirstChildKey(this.props); // Reset the scroll position when a new child comes in in order not to // jerk the scrollbar around if you're already scrolled down the page. if (someItemInserted && this._oldScrollPosition && this.node.scrollTop > 0) { const newScrollTop = this.node.scrollHeight - this._oldScrollPosition; if (this.node.scrollTop !== newScrollTop) { this.node.scrollTop = newScrollTop; } } else { this._oldScrollPosition = this.node.scrollHeight - this.node.scrollTop; } } componentWillUnmount () { this.detachScrollListener(); this.detachIntersectionObserver(); } attachIntersectionObserver () { this.intersectionObserverWrapper.connect({ root: this.node, rootMargin: '300% 0px', }); } detachIntersectionObserver () { this.intersectionObserverWrapper.disconnect(); } attachScrollListener () { this.node.addEventListener('scroll', this.handleScroll); } detachScrollListener () { this.node.removeEventListener('scroll', this.handleScroll); } getFirstChildKey (props) { const { children } = props; let firstChild = children; if (children instanceof ImmutableList) { firstChild = children.get(0); } else if (Array.isArray(children)) { firstChild = children[0]; } return firstChild && firstChild.key; } setRef = (c) => { this.node = c; } handleLoadMore = (e) => { e.preventDefault(); this.props.onScrollToBottom(); } _recentlyMoved () { return this._lastMouseMove !== null && ((new Date()) - this._lastMouseMove < 600); } handleKeyDown = (e) => { if (['PageDown', 'PageUp'].includes(e.key) || (e.ctrlKey && ['End', 'Home'].includes(e.key))) { const article = (() => { switch (e.key) { case 'PageDown': return e.target.nodeName === 'ARTICLE' && e.target.nextElementSibling; case 'PageUp': return e.target.nodeName === 'ARTICLE' && e.target.previousElementSibling; case 'End': return this.node.querySelector('[role="feed"] > article:last-of-type'); case 'Home': return this.node.querySelector('[role="feed"] > article:first-of-type'); default: return null; } })(); if (article) { e.preventDefault(); article.focus(); article.scrollIntoView(); } } } render () { const { children, scrollKey, trackScroll, shouldUpdateScroll, isLoading, hasMore, prepend, emptyMessage } = this.props; const childrenCount = React.Children.count(children); const loadMore = (hasMore && childrenCount > 0) ? : null; let scrollableArea = null; if (isLoading || childrenCount > 0 || !emptyMessage) { scrollableArea = (
{prepend} {React.Children.map(this.props.children, (child, index) => ( {child} ))} {loadMore}
); } else { scrollableArea = (
{emptyMessage}
); } if (trackScroll) { return ( {scrollableArea} ); } else { return scrollableArea; } } }