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import type { FunctionalComponent } from 'preact';
import { h } from 'preact';
import { useState, useEffect, useRef } from 'preact/hooks';
import EditOnGithub from './EditOnGithub';
const DocSidebar: FunctionalComponent<{ headers: any[]; editHref: string }> = ({ headers = [], editHref }) => {
const itemOffsets = useRef([]);
const [activeId, setActiveId] = useState<string>(undefined);
useEffect(() => {
const getItemOffsets = () => {
const titles = document.querySelectorAll('article :is(h2, h3, h4)');
itemOffsets.current = Array.from(titles).map((title) => ({
id: title.id,
topOffset: title.getBoundingClientRect().top + window.scrollY,
}));
};
const onScroll = () => {
const itemIndex = itemOffsets.current.findIndex((item) => item.topOffset > window.scrollY + window.innerHeight / 3);
if (itemIndex === 0) {
setActiveId(undefined);
} else if (itemIndex === -1) {
setActiveId(itemOffsets.current[itemOffsets.current.length - 1].id);
} else {
setActiveId(itemOffsets.current[itemIndex - 1].id);
}
};
getItemOffsets();
window.addEventListener('resize', getItemOffsets);
window.addEventListener('scroll', onScroll);
return () => {
window.removeEventListener('resize', getItemOffsets);
window.removeEventListener('scroll', onScroll);
};
}, []);
return (
<nav>
<div>
<h4>Contents</h4>
<ul>
{headers
.filter(({ depth }) => depth > 1 && depth < 5)
.map((header) => (
<li class={`header-link depth-${header.depth} ${activeId === header.slug ? 'active' : ''}`.trim()}>
<a href={`#${header.slug}`}>{header.text}</a>
</li>
))}
</ul>
</div>
<div>
<EditOnGithub href={editHref} />
</div>
</nav>
);
};
export default DocSidebar;
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