@vivliostyle/vfm/lib/plugins/slug.js

Custom Markdown syntax specialized in book authoring.

/**
 * derived from `remark-slug`.
 * original: Copyright (c) 2015 Titus Wormer <tituswormer@gmail.com>
 * modified: 2021 and later is Akabeko
 * @license MIT
 * @see https://github.com/remarkjs/remark-slug
 */
import GithubSlugger from 'github-slugger';
import { toString } from 'mdast-util-to-string';
import { selectAll } from 'unist-util-select';
/**
 * Create slug from `id` or heading children.
 * @param heading Heading.
 * @param slugs Slugger.
 * @returns
 */
const createSlug = (heading, slugger) => {
    if (heading.data && heading.data.hProperties && heading.data.hProperties.id) {
        return slugger.slug(heading.data.hProperties.id, true);
    }
    // Create slug string with footnotes removed
    const children = [...heading.children];
    heading.children = heading.children.filter((child) => child.type !== 'footnote');
    const text = slugger.slug(toString(heading).replace(/<[^<>]*>/g, ''));
    heading.children = children;
    return text;
};
/**
 * Process Markdown AST.
 * @returns Transformer.
 */
export const mdast = () => (tree) => {
    const slugger = new GithubSlugger();
    slugger.reset();
    const headings = selectAll('heading', tree);
    for (const heading of headings) {
        const id = createSlug(heading, slugger);
        if (!heading.data) {
            heading.data = {};
        }
        if (!heading.data.hProperties) {
            heading.data.hProperties = {};
        }
        heading.data.id = id;
        heading.data.hProperties.id = id;
    }
};