Feature/toc and collapse

package.json

@@ -16,7 +16,6 @@
     "@react-spring/web": "^9.7.3",
     "clsx": "^1.2.1",
     "feed": "^4.2.2",
-    "github-slugger": "^2.0.0",
     "next": "^13.5.6",
     "next-mdx-remote": "^4.4.1",
     "next-nprogress-bar": "^2.1.2",

src/app/[lang]/posts/[postId]/__tests__/page.test.tsx

@@ -30,7 +30,6 @@ describe('[postId] page', () => {
     mockData.mockReturnValueOnce({
       id: 'test-id',
       content: <h2>{testText}</h2>,
-      source: `## ${testText}`,
       frontmatter: {
         date: '2023/10/28',
         title: 'test title',

src/app/[lang]/posts/[postId]/page.tsx

@@ -34,8 +34,9 @@ async function PostPage({ params: { postId } }: PostParams) {
 
   if (!post) return notFound();
 
-  const { content, frontmatter, source } = post;
+  const { content, frontmatter } = post;
   const formattedDate = formatDate(frontmatter.date);
+  const id = `article-${postId}`;
 
   return (
     <>
@@ -45,15 +46,21 @@ async function PostPage({ params: { postId } }: PostParams) {
       </Container>
       <Container as="main" className="block py-8 lg:flex lg:px-2">
         <aside className="hidden w-40 shrink-0 lg:block xl:w-60">
-          <nav className="sticky top-[var(--header-height)] px-4">
+          <nav className="top-header-height sticky px-4">
             <h4 className="my-3 text-lg font-semibold text-gray-900 dark:text-gray-100">
               目錄
             </h4>
-            <TableOfContents source={source} />
+            <TableOfContents
+              className="max-h-96 overflow-auto"
+              targetId={`#${id}`}
+            />
           </nav>
         </aside>
         <div>
-          <article className="prose prose-zinc mx-auto px-4 dark:prose-invert">
+          <article
+            id={id}
+            className="prose prose-zinc mx-auto px-4 dark:prose-invert"
+          >
             {content}
           </article>
           <Link href="/">回首頁</Link>

src/components/Collapse/Collapse.tsx

@@ -0,0 +1,29 @@
+'use client';
+
+import { useRef, ReactNode, HTMLAttributes } from 'react';
+import { useSpring, animated } from '@react-spring/web';
+
+type CollapseProps = {
+  isOpen: boolean;
+  children: ReactNode;
+} & HTMLAttributes<HTMLElement>;
+
+export default function Collapse({
+  isOpen,
+  children,
+  ...props
+}: CollapseProps) {
+  const childrenRef = useRef<HTMLDivElement>(null);
+  const styles = useSpring({
+    to: {
+      height: isOpen ? childrenRef.current?.clientHeight : 0,
+      opacity: isOpen ? 1 : 0.6,
+    },
+  });
+
+  return (
+    <animated.div className="overflow-hidden" style={styles} {...props}>
+      <div ref={childrenRef}>{children}</div>
+    </animated.div>
+  );
+}

src/components/Collapse/collapse.test.tsx

@@ -0,0 +1,43 @@
+import { render, screen, waitFor } from '@testing-library/react';
+import { Globals } from '@react-spring/web';
+
+import Collapse from '.';
+
+describe('Collapse component', () => {
+  beforeAll(() => {
+    Globals.assign({
+      skipAnimation: true,
+    });
+  });
+
+  it('should render correct element', async () => {
+    render(
+      <Collapse isOpen data-testid="collapse">
+        Test
+      </Collapse>
+    );
+    const collapse = screen.getByTestId('collapse');
+
+    expect(collapse).toBeInTheDocument();
+    expect(collapse).toHaveTextContent('Test');
+  });
+
+  it('should update Collapse component styles on re-render', async () => {
+    const { rerender } = render(
+      <Collapse isOpen={false} data-testid="collapse">
+        Test
+      </Collapse>
+    );
+    const collapse = screen.getByTestId('collapse');
+
+    await waitFor(() => expect(collapse).toHaveStyle('opacity: 0.6'));
+
+    rerender(
+      <Collapse isOpen={true} data-testid="collapse">
+        Test
+      </Collapse>
+    );
+
+    await waitFor(() => expect(collapse).toHaveStyle('opacity: 1'));
+  });
+});

src/components/Collapse/index.tsx

@@ -0,0 +1,3 @@
+import Collapse from './Collapse';
+
+export default Collapse;

src/components/TableOfContents/TableOfContents.tsx

@@ -1,40 +1,52 @@
 'use client';
 
-import { useEffect, useState } from 'react';
-import GithubSlugger from 'github-slugger';
+import { useEffect, useLayoutEffect, useState } from 'react';
 
 import useIntersectionObserver from '@/hooks/useIntersectionObserver';
 import cn from '@/utils/cn';
+import Collapse from '../Collapse';
 import Link from '../Link';
 
 type TableOfContentsProps = {
-  source: string;
+  targetId: `#${string}`;
+  className?: string;
 };
 
-function TableOfContents({ source }: TableOfContentsProps) {
+type Heading = {
+  id: string;
+  text: string | undefined;
+  children?: Heading[];
+};
+
+function TableOfContents({ className, targetId }: TableOfContentsProps) {
   const [activeId, setActiveId] = useState('');
+  const [headings, setHeadings] = useState<Heading[]>([]);
   const [entry, setElementRef] = useIntersectionObserver();
 
-  const headingLines = source
-    .split('\n')
-    .filter((line) => line.match(/^###?\s/));
-
-  const headings = headingLines.map((raw) => {
-    const text = raw.replace(/^###*\s/, '');
-    const level = raw.slice(0, 3) === '###' ? 3 : 2;
-    const slugger = new GithubSlugger();
-    const id = slugger.slug(text);
-
-    return { text, level, id };
-  });
-
   useEffect(() => {
-    setElementRef(
-      Array.from(document.querySelectorAll('article h2, article h3'))
+    const headingElements = Array.from(
+      document.querySelectorAll(`${targetId} h2, ${targetId} h3`)
     );
-  }, [setElementRef]);
+    setElementRef(headingElements);
+    setHeadings(
+      headingElements.reduce<Heading[]>(
+        (result, { id, tagName, textContent }) => {
+          const heading = { id, text: textContent?.slice(1) };
+          const lastHeading = result.at(-1);
 
-  useEffect(() => {
+          if (tagName === 'H2') {
+            result.push(heading);
+          } else if (lastHeading) {
+            lastHeading.children = (lastHeading.children || []).concat(heading);
+          }
+          return result;
+        },
+        []
+      )
+    );
+  }, [targetId, setElementRef]);
+
+  useLayoutEffect(() => {
     const visibleHeadings = entry.filter(
       ({ isIntersecting }) => isIntersecting
     );
@@ -44,24 +56,41 @@ function TableOfContents({ source }: TableOfContentsProps) {
     }
   }, [entry]);
 
+  const isActive = (id: string, children: Heading[]) =>
+    id === activeId || children.some((child) => child.id === activeId);
+
+  const getLinkClassName = (id: string, children: Heading[] = []) =>
+    cn(
+      'transition-colors mb-0.5 block overflow-hidden text-ellipsis whitespace-nowrap hover:underline',
+      isActive(id, children)
+        ? 'text-primary-500 hover:text-primary-600 dark:hover:text-primary-400'
+        : 'text-gray-500 hover:text-gray-800 dark:text-gray-400 dark:hover:text-gray-200'
+    );
+
   return (
-    <nav aria-label="Table of contents">
-      <ul>
-        {headings.map((heading) => (
-          <li key={heading.id}>
-            <Link
-              href={`#${heading.id}`}
-              title={heading.text}
-              className={cn(
-                'mb-0.5 block overflow-hidden text-ellipsis whitespace-nowrap text-left text-sm hover:underline',
-                heading.id === activeId
-                  ? 'font-medium text-primary-500 hover:text-primary-600 dark:hover:text-primary-400'
-                  : 'font-normal text-gray-500 hover:text-gray-800 dark:text-gray-400 dark:hover:text-gray-200',
-                heading.level === 3 && 'pl-4'
-              )}
-            >
-              {heading.text}
+    <nav aria-label="Table of contents" className={className}>
+      <ul className="text-sm">
+        {headings.map(({ id, text, children }) => (
+          <li key={id}>
+            <Link href={`#${id}`} className={getLinkClassName(id, children)}>
+              {text}
             </Link>
+            {children && (
+              <Collapse isOpen={isActive(id, children)}>
+                <ul className="pb-0.5 pl-4">
+                  {children.map((child) => (
+                    <li key={child.id}>
+                      <Link
+                        href={`#${child.id}`}
+                        className={getLinkClassName(child.id)}
+                      >
+                        {child.text}
+                      </Link>
+                    </li>
+                  ))}
+                </ul>
+              </Collapse>
+            )}
           </li>
         ))}
       </ul>