fix: generate an id for each headings in the page main contents

Since #be4d907 the ids was no longer addded to headings in
useHeadingsTree hook. It was a bad practice to manipulate the DOM
that way. However, I did not move the implementation elsewhere...
To fix this, I now use rehype-slug on both markdown contents and
html string coming from WordPress.
I'm not sure the dynamic imports are really useful here since the
table of contents is on almost all pages but Jest was failing with
regular import because of ESM. It is the only thing that makes the
tests functional again so... However if we want to test the
`updateContentTree` function, Jest fails for the same reason. So I
decided to not test this function. I've already spend too much time
on this issue.
Another problem: the ToC on projects page. Currently we use the ref
on the body but the page contents are imported dynamically so the
hook is executed before the contents are loaded. It makes the ToC
empty... We should refactor the pages so we can use the ref
directly on the imported contents.

8 files changed, 99 insertions, 49 deletions

diff --git a/src/utils/helpers/index.ts b/src/utils/helpers/index.ts
index 79077de..92f9424 100644
--- a/src/utils/helpers/index.ts
+++ b/src/utils/helpers/index.ts
@@ -3,6 +3,7 @@ export * from './images';
 export * from './pages';
 export * from './reading-time';
 export * from './refs';
+export * from './rehype';
 export * from './rss';
 export * from './schema-org';
 export * from './strings';
diff --git a/src/utils/helpers/pages.tsx b/src/utils/helpers/pages.tsx
index 62a582f..7b6bdca 100644
--- a/src/utils/helpers/pages.tsx
+++ b/src/utils/helpers/pages.tsx
@@ -109,9 +109,9 @@ export const getPostsWithUrl = (posts: Article[]): PostData[] =>
  * @param {EdgesResponse<RawArticle>[]} rawData - The raw data.
  * @returns {PostData[]} An array of posts.
  */
-export const getPostsList = (
+export const getPostsList = async (
   rawData: EdgesResponse<RawArticle>[]
-): PostData[] => {
+): Promise<PostData[]> => {
   const articlesList: RawArticle[] = [];
   rawData.forEach((articleData) => {
     articleData.edges.forEach((edge) => {
@@ -120,6 +120,8 @@ export const getPostsList = (
   });
 
   return getPostsWithUrl(
-    articlesList.map((article) => getArticleFromRawData(article))
+    await Promise.all(
+      articlesList.map(async (article) => getArticleFromRawData(article))
+    )
   );
 };
diff --git a/src/utils/helpers/rehype.ts b/src/utils/helpers/rehype.ts
new file mode 100644
index 0000000..2716c62
--- /dev/null
+++ b/src/utils/helpers/rehype.ts
@@ -0,0 +1,23 @@
+/**
+ * Update a stringified HTML tree using unified plugins.
+ *
+ * It will parse the provided content to add id to each headings.
+ *
+ * @param {string} content - The page contents.
+ * @returns {string} The updated page contents.
+ */
+export const updateContentTree = async (content: string): Promise<string> => {
+  const { unified } = await import('unified');
+  const rehypeParse = (await import('rehype-parse')).default;
+  const rehypeSanitize = (await import('rehype-sanitize')).default;
+  const rehypeSlug = (await import('rehype-slug')).default;
+  const rehypeStringify = (await import('rehype-stringify')).default;
+
+  return unified()
+    .use(rehypeParse, { fragment: true })
+    .use(rehypeSlug)
+    .use(() => rehypeSanitize({ clobberPrefix: 'h-' }))
+    .use(rehypeStringify)
+    .processSync(content)
+    .toString();
+};
diff --git a/src/utils/helpers/rss.ts b/src/utils/helpers/rss.ts
index 6de60cc..d9c3b1e 100644
--- a/src/utils/helpers/rss.ts
+++ b/src/utils/helpers/rss.ts
@@ -18,8 +18,8 @@ const getAllArticles = async (): Promise<Article[]> => {
   const rawArticles = await getArticles({ first: totalArticles });
   const articles: Article[] = [];
 
-  rawArticles.edges.forEach((edge) => {
-    articles.push(getArticleFromRawData(edge.node));
+  rawArticles.edges.forEach(async (edge) => {
+    articles.push(await getArticleFromRawData(edge.node));
   });
 
   return articles;
diff --git a/src/utils/hooks/use-article.ts b/src/utils/hooks/use-article.ts
index 5cf0e51..f339f7f 100644
--- a/src/utils/hooks/use-article.ts
+++ b/src/utils/hooks/use-article.ts
@@ -1,10 +1,11 @@
+import { useEffect, useState } from 'react';
 import useSWR from 'swr';
 import {
   articleBySlugQuery,
   fetchAPI,
   getArticleFromRawData,
 } from '../../services/graphql';
-import type { Article, RawArticle } from '../../types';
+import type { Article, Maybe, RawArticle } from '../../types';
 
 export type UseArticleConfig = {
   /**
@@ -32,6 +33,19 @@ export const useArticle = ({
     fetchAPI<RawArticle, typeof articleBySlugQuery>,
     {}
   );
+  const [article, setArticle] = useState<Maybe<Article>>();
 
-  return data ? getArticleFromRawData(data.post) : fallback;
+  useEffect(() => {
+    const getArticle = async () => {
+      if (data) {
+        setArticle(await getArticleFromRawData(data.post));
+      } else {
+        setArticle(fallback);
+      }
+    };
+
+    getArticle();
+  }, [data, fallback]);
+
+  return article;
 };
diff --git a/src/utils/hooks/use-headings-tree/use-headings-tree.test.ts b/src/utils/hooks/use-headings-tree/use-headings-tree.test.ts
index ad30a4f..2c8ff2d 100644
--- a/src/utils/hooks/use-headings-tree/use-headings-tree.test.ts
+++ b/src/utils/hooks/use-headings-tree/use-headings-tree.test.ts
@@ -1,5 +1,5 @@
 import { describe, expect, it } from '@jest/globals';
-import { renderHook } from '@testing-library/react';
+import { act, renderHook } from '@testing-library/react';
 import { useHeadingsTree } from './use-headings-tree';
 
 const labels = {
@@ -9,7 +9,7 @@ const labels = {
 };
 
 describe('useHeadingsTree', () => {
-  it('returns a ref object and the headings tree', () => {
+  it('returns a ref callback and the headings tree', () => {
     const wrapper = document.createElement('div');
 
     wrapper.innerHTML = `
@@ -19,12 +19,13 @@ describe('useHeadingsTree', () => {
 <h2>${labels.secondH2}</h2>
 <p>Totam cumque aut ipsum. Necessitatibus magnam necessitatibus. Qui illo nulla non ab. Accusamus voluptatem ab fugiat voluptas aspernatur velit dolore reprehenderit. Voluptatem quod minima asperiores voluptatum distinctio cumque quo.</p>`;
 
-    const wrapperRef = { current: wrapper };
-    const { result } = renderHook(() => useHeadingsTree(wrapperRef));
+    const { result } = renderHook(() => useHeadingsTree());
 
-    expect(result.current.length).toBe(1);
-    expect(result.current[0].label).toBe(labels.h1);
-    expect(result.current[0].children.length).toBe(2);
+    act(() => result.current.ref(wrapper));
+
+    expect(result.current.tree.length).toBe(1);
+    expect(result.current.tree[0].label).toBe(labels.h1);
+    expect(result.current.tree[0].children.length).toBe(2);
   });
 
   it('can return a headings tree starting at the specified level', () => {
@@ -37,14 +38,13 @@ describe('useHeadingsTree', () => {
 <h2>${labels.secondH2}</h2>
 <p>Totam cumque aut ipsum. Necessitatibus magnam necessitatibus. Qui illo nulla non ab. Accusamus voluptatem ab fugiat voluptas aspernatur velit dolore reprehenderit. Voluptatem quod minima asperiores voluptatum distinctio cumque quo.</p>`;
 
-    const wrapperRef = { current: wrapper };
-    const { result } = renderHook(() =>
-      useHeadingsTree(wrapperRef, { fromLevel: 2 })
-    );
+    const { result } = renderHook(() => useHeadingsTree({ fromLevel: 2 }));
+
+    act(() => result.current.ref(wrapper));
 
-    expect(result.current.length).toBe(2);
-    expect(result.current[0].label).toBe(labels.firstH2);
-    expect(result.current[1].label).toBe(labels.secondH2);
+    expect(result.current.tree.length).toBe(2);
+    expect(result.current.tree[0].label).toBe(labels.firstH2);
+    expect(result.current.tree[1].label).toBe(labels.secondH2);
   });
 
   it('can return a headings tree stopping at the specified level', () => {
@@ -57,22 +57,17 @@ describe('useHeadingsTree', () => {
 <h2>${labels.secondH2}</h2>
 <p>Totam cumque aut ipsum. Necessitatibus magnam necessitatibus. Qui illo nulla non ab. Accusamus voluptatem ab fugiat voluptas aspernatur velit dolore reprehenderit. Voluptatem quod minima asperiores voluptatum distinctio cumque quo.</p>`;
 
-    const wrapperRef = { current: wrapper };
-    const { result } = renderHook(() =>
-      useHeadingsTree(wrapperRef, { toLevel: 1 })
-    );
+    const { result } = renderHook(() => useHeadingsTree({ toLevel: 1 }));
+
+    act(() => result.current.ref(wrapper));
 
-    expect(result.current.length).toBe(1);
-    expect(result.current[0].label).toBe(labels.h1);
-    expect(result.current[0].children).toStrictEqual([]);
+    expect(result.current.tree.length).toBe(1);
+    expect(result.current.tree[0].label).toBe(labels.h1);
+    expect(result.current.tree[0].children).toStrictEqual([]);
   });
 
   it('throws an error if the options are invalid', () => {
-    const wrapperRef = { current: null };
-
-    expect(() =>
-      useHeadingsTree(wrapperRef, { fromLevel: 2, toLevel: 1 })
-    ).toThrowError(
+    expect(() => useHeadingsTree({ fromLevel: 2, toLevel: 1 })).toThrowError(
       'Invalid options: `fromLevel` must be lower or equal to `toLevel`.'
     );
   });
diff --git a/src/utils/hooks/use-headings-tree/use-headings-tree.ts b/src/utils/hooks/use-headings-tree/use-headings-tree.ts
index 6a081e7..68bdde8 100644
--- a/src/utils/hooks/use-headings-tree/use-headings-tree.ts
+++ b/src/utils/hooks/use-headings-tree/use-headings-tree.ts
@@ -1,4 +1,4 @@
-import { useEffect, useState, type RefObject } from 'react';
+import { useState, useCallback, type RefCallback } from 'react';
 import type { HeadingLevel } from '../../../components';
 
 export type HeadingsTreeNode = {
@@ -111,17 +111,26 @@ const buildHeadingsTreeFrom = (
   return treeNodes;
 };
 
+export type UseHeadingsTreeReturn<T extends HTMLElement> = {
+  /**
+   * A callback function to set a ref.
+   */
+  ref: RefCallback<T>;
+  /**
+   * The headings tree.
+   */
+  tree: HeadingsTreeNode[];
+};
+
 /**
  * React hook to retrieve the headings tree in a document or in a given wrapper.
  *
- * @param {RefObject<T>} ref - A ref to the element where to look for headings.
  * @param {UseHeadingsTreeOptions} options - The headings tree config.
- * @returns {HeadingsTreeNode[]} The headings tree.
+ * @returns {UseHeadingsTreeReturn<T>} The headings tree and a ref callback.
  */
 export const useHeadingsTree = <T extends HTMLElement = HTMLElement>(
-  ref: RefObject<T>,
   options?: UseHeadingsTreeOptions
-): HeadingsTreeNode[] => {
+): UseHeadingsTreeReturn<T> => {
   if (
     options?.fromLevel &&
     options.toLevel &&
@@ -134,15 +143,14 @@ export const useHeadingsTree = <T extends HTMLElement = HTMLElement>(
   const [tree, setTree] = useState<HeadingsTreeNode[]>([]);
   const requestedHeadingTags = getHeadingTagsList(options);
   const query = requestedHeadingTags.join(', ');
+  const ref: RefCallback<T> = useCallback(
+    (el) => {
+      const headingNodes = el?.querySelectorAll<HTMLHeadingElement>(query);
 
-  useEffect(() => {
-    if (typeof window === 'undefined') return;
-
-    const headingNodes =
-      ref.current?.querySelectorAll<HTMLHeadingElement>(query);
-
-    if (headingNodes) setTree(buildHeadingsTreeFrom(headingNodes));
-  }, [query, ref]);
+      if (headingNodes) setTree(buildHeadingsTreeFrom(headingNodes));
+    },
+    [query]
+  );
 
-  return tree;
+  return { ref, tree };
 };
diff --git a/src/utils/hooks/use-posts-list/use-posts-list.ts b/src/utils/hooks/use-posts-list/use-posts-list.ts
index 661727f..980d531 100644
--- a/src/utils/hooks/use-posts-list/use-posts-list.ts
+++ b/src/utils/hooks/use-posts-list/use-posts-list.ts
@@ -1,4 +1,4 @@
-import { useCallback, useState } from 'react';
+import { useCallback, useEffect, useState } from 'react';
 import type { PostData } from '../../../components';
 import type { Maybe, RawArticle } from '../../../types';
 import { getPostsList } from '../../helpers';
@@ -40,8 +40,15 @@ export const usePostsList = (
   } = usePagination(config);
   const [firstNewResultIndex, setFirstNewResultIndex] =
     useState<Maybe<number>>(undefined);
+  const [posts, setPosts] = useState<Maybe<PostData[]>>(undefined);
 
-  const posts = data ? getPostsList(data) : undefined;
+  useEffect(() => {
+    const getPosts = async () => {
+      if (data) setPosts(await getPostsList(data));
+    };
+
+    getPosts();
+  }, [data]);
 
   const handleLoadMore = useCallback(async () => {
     setFirstNewResultIndex(size * config.perPage + 1);