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import { html, Component } from "../lib/index.js";
let store = new Map();
export default class ScrollManager extends Component {
constructor(props) {
super(props);
this.handleScroll = this.handleScroll.bind(this);
}
isAtBottom() {
let target = this.props.target.current;
return Math.abs(target.scrollHeight - target.clientHeight - target.scrollTop) <= 10;
}
saveScrollPosition(scrollKey) {
let target = this.props.target.current;
let sticky = target.querySelectorAll(this.props.stickTo);
let stickToKey = null;
if (!this.isAtBottom()) {
for (let i = 0; i < sticky.length; i++) {
let el = sticky[i];
if (el.offsetTop >= target.scrollTop + target.offsetTop) {
stickToKey = el.dataset.key;
break;
}
}
}
store.set(scrollKey, stickToKey);
}
restoreScrollPosition() {
let target = this.props.target.current;
if (!target.firstChild) {
return;
}
let stickToKey = store.get(this.props.scrollKey);
if (!stickToKey) {
target.firstChild.scrollIntoView({ block: "end" });
} else {
let stickTo = target.querySelector("[data-key=\"" + stickToKey + "\"]");
if (stickTo) {
stickTo.scrollIntoView();
}
}
if (target.scrollTop == 0) {
this.props.onScrollTop();
}
}
handleScroll() {
if (this.props.target.current.scrollTop == 0) {
this.props.onScrollTop();
}
}
componentDidMount() {
this.restoreScrollPosition();
this.props.target.current.addEventListener("scroll", this.handleScroll);
}
getSnapshotBeforeUpdate(prevProps) {
if (this.props.scrollKey !== prevProps.scrollKey || this.props.children !== prevProps.children) {
this.saveScrollPosition(prevProps.scrollKey);
}
}
componentDidUpdate(prevProps) {
if (!this.props.target.current) {
return;
}
this.restoreScrollPosition();
}
componentWillUnmount() {
this.props.target.current.removeEventListener("scroll", this.handleScroll);
this.saveScrollPosition(this.props.scrollKey);
}
render() {
return this.props.children;
}
}
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