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import { slugify } from '@utils/helpers/slugify';
import { useCallback, useEffect, useMemo, useState } from 'react';
type Heading = {
depth: number;
id: string;
children: Heading[];
title: string;
};
const useHeadingsTree = (wrapper: string) => {
const [headingsTree, setHeadingsTree] = useState<Heading[]>([]);
const depths = useMemo(() => ['h2', 'h3', 'h4', 'h5', 'h6'], []);
const getElementDepth = useCallback(
(el: HTMLHeadingElement) => {
const elDepth = depths.findIndex((depth) => depth === el.localName);
return elDepth;
},
[depths]
);
const formatHeadings = useCallback(
(headings: NodeListOf<HTMLHeadingElement>): Heading[] => {
const formattedHeadings: Heading[] = [];
Array.from(headings).forEach((heading) => {
const title: string = heading.textContent!;
const id = slugify(title);
const depth = getElementDepth(heading);
const children: Heading[] = [];
heading.id = id;
formattedHeadings.push({
depth,
id,
children,
title,
});
});
return formattedHeadings;
},
[getElementDepth]
);
const buildSubTree = useCallback(
(parent: Heading, currentHeading: Heading): void => {
if (parent.depth === currentHeading.depth - 1) {
parent.children.push(currentHeading);
} else {
const lastItem = parent.children[parent.children.length - 1];
buildSubTree(lastItem, currentHeading);
}
},
[]
);
const buildTree = useCallback(
(headings: Heading[]): Heading[] => {
const tree: Heading[] = [];
headings.forEach((heading) => {
if (heading.depth === 0) {
tree.push(heading);
} else {
const lastItem = tree[tree.length - 1];
buildSubTree(lastItem, heading);
}
});
return tree;
},
[buildSubTree]
);
const getHeadingsList = useCallback(
(headings: NodeListOf<HTMLHeadingElement>): Heading[] => {
const formattedHeadings = formatHeadings(headings);
const headingsList = buildTree(formattedHeadings);
return headingsList;
},
[formatHeadings, buildTree]
);
useEffect(() => {
const query = depths.map((depth) => `${wrapper} ${depth}`).join(', ');
const headings: NodeListOf<HTMLHeadingElement> =
document.querySelectorAll(query);
const headingsList = getHeadingsList(headings);
setHeadingsTree(headingsList);
}, [depths, wrapper, getHeadingsList]);
return headingsTree;
};
export default useHeadingsTree;
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