remarkHeadingIdsToSectionIds.ts

import type { Root, Parent, Data } from "mdast";
import { visit } from "unist-util-visit";

import { mdastHeadingToString } from "app/lib/headingToString";
import slugify from "app/lib/slugify";

export default function remarkHeadingIdsToSectionIds() {
  return (tree: Root) => {
    visit(tree, "heading", (node: Parent, _index, parent: Parent) => {
      if (parent.type === "section") {
        const data: Data = parent.data || (parent.data = {});
        const props: { id?: string } =
          data.hProperties || (data.hProperties = {});

        props.id = slugify(mdastHeadingToString(node));
      }
    });
  };
}