From bcc2d85560c8453d03fef64b17bc5bf4df3cc568 Mon Sep 17 00:00:00 2001
From: Drew Haven <periodic@blazestar.net>
Date: Tue, 26 May 2026 17:10:01 -0700
Subject: [PATCH] Adds table of contents.  Removes now from the top level of
 the sidebar.

---
 src/components/Sidebar.astro             |  1 -
 src/components/TableOfContents.astro     | 31 +++++++++++++++
 src/components/TableOfContentsTree.astro | 15 ++++++++
 src/layouts/BlogPost.astro               |  7 +++-
 src/lib/headings.ts                      | 49 ++++++++++++++++++++++++
 src/pages/blog/[...slug].astro           |  4 +-
 src/pages/notes/[...slug].astro          |  4 +-
 7 files changed, 105 insertions(+), 6 deletions(-)
 create mode 100644 src/components/TableOfContents.astro
 create mode 100644 src/components/TableOfContentsTree.astro
 create mode 100644 src/lib/headings.ts

diff --git a/src/components/Sidebar.astro b/src/components/Sidebar.astro
index 5aea431..597fa15 100644
--- a/src/components/Sidebar.astro
+++ b/src/components/Sidebar.astro
@@ -12,7 +12,6 @@ import SocialLinks from './SocialLinks.astro';
 			<SidebarLink href="/">Home</SidebarLink>
 			<SidebarLink href="/blog">Blog</SidebarLink>
 			<SidebarLink href="/about">About</SidebarLink>
-			<SidebarLink href="/now">Now</SidebarLink>
       <NotesLinks />
 		</div>
 		<div class="social-links">
diff --git a/src/components/TableOfContents.astro b/src/components/TableOfContents.astro
new file mode 100644
index 0000000..e8e1045
--- /dev/null
+++ b/src/components/TableOfContents.astro
@@ -0,0 +1,31 @@
+---
+import TableOfContentsTree from "./TableOfContentsTree.astro";
+import type { MarkdownHeading } from "astro";
+import { makeHeadingsTree, removeEmptyLevels } from "../lib/headings";
+
+type Props = {
+  headings: Array<MarkdownHeading>;
+};
+
+const {headings} = Astro.props;
+const headingsTree = removeEmptyLevels(makeHeadingsTree(headings));
+---
+
+<div class="table-of-contents">
+  <TableOfContentsTree headingsTree={headingsTree}></TableOfContentsTree>
+</div>
+
+<style>
+.table-of-contents {
+  border: 1px solid var(--color-space-blue-light);
+
+  ul {
+    list-style: none;
+  }
+
+  & > ul {
+    padding: 0;
+    margin: 8px 16px;
+  }
+}
+</style>
diff --git a/src/components/TableOfContentsTree.astro b/src/components/TableOfContentsTree.astro
new file mode 100644
index 0000000..b22eb50
--- /dev/null
+++ b/src/components/TableOfContentsTree.astro
@@ -0,0 +1,15 @@
+---
+type Props = {
+  headingsTree: HeadingsTree;
+};
+
+const {headingsTree} = Astro.props;
+---
+
+<ul>
+  {headingsTree.map(node =>
+    Array.isArray(node)
+      ? <Astro.self headingsTree={node} />
+      : <li><a href={`#${node.slug}`}>{node.text}</a></li>
+  )}
+</ul>
diff --git a/src/layouts/BlogPost.astro b/src/layouts/BlogPost.astro
index 40f4f6d..5580888 100644
--- a/src/layouts/BlogPost.astro
+++ b/src/layouts/BlogPost.astro
@@ -1,13 +1,15 @@
 ---
+import type { MarkdownHeading } from "astro";
 import type { CollectionEntry } from 'astro:content';
 import RootLayout from '../layouts/RootLayout.astro';
 import FormattedDate from '../components/FormattedDate.astro';
 import NotchedBox from '../components/NotchedBox.astro';
+import TableOfContents from '../components/TableOfContents.astro';
 import { Image } from 'astro:assets';
 
-type Props = CollectionEntry<'blog'>['data'] & { slug: string; };
+type Props = CollectionEntry<'blog'>['data'] & { slug: string; headings: MarkdownHeading[] };
 
-const { slug, title, description, pubDate, updatedDate, heroImage, tags } = Astro.props;
+const { slug, title, description, pubDate, updatedDate, heroImage, tags, headings } = Astro.props;
 ---
 
 <style>
@@ -77,6 +79,7 @@ const { slug, title, description, pubDate, updatedDate, heroImage, tags } = Astr
           </div>
         }
         <hr />
+        <TableOfContents headings={headings} />
         <div class="e-content">
           <slot />
         </div>
diff --git a/src/lib/headings.ts b/src/lib/headings.ts
new file mode 100644
index 0000000..18c2d34
--- /dev/null
+++ b/src/lib/headings.ts
@@ -0,0 +1,49 @@
+import type { MarkdownHeading } from "astro";
+
+export type HeadingsTree = Array<MarkdownHeading | HeadingsTree>;
+
+// could take a list like [5, 1, 2, 2, 3, 5, 1] and should return
+// [ [ [ [ [ 5 ] ] ] ], 1, [ 2, 2, [3, [[5]]]], 1]
+export function makeHeadingsTree(headings: MarkdownHeading[]): HeadingsTree {
+  let index = 0;
+  let currDepth = 1;
+  const treeStack = [[]] as Array<HeadingsTree>;
+
+  while (index < headings.length) {
+    const currHeading = headings[index];
+
+    // If the next heading is at the current depth, push it into the tree
+    if (currHeading.depth == currDepth) {
+      treeStack[treeStack.length - 1].push(currHeading);
+      index += 1;
+    }
+
+    // If the next heading is deeper, go deeper
+    if (currHeading.depth > currDepth) {
+      const nextLevel = [] as HeadingsTree;
+      treeStack[treeStack.length - 1].push(nextLevel);
+      treeStack.push(nextLevel);
+      currDepth += 1;
+    }
+
+    // If the next heading is shallower, back out
+    if (currHeading.depth < currDepth) {
+      treeStack.pop();
+      currDepth -= 1;
+    }
+  }
+
+  return treeStack[0];
+}
+
+export function removeEmptyLevels(tree: HeadingsTree): HeadingsTree {
+  const newLevel = tree.map((node) =>
+    Array.isArray(node) ? removeEmptyLevels(node) : node,
+  );
+
+  if (tree.every(Array.isArray)) {
+    return tree.flatMap((node) => node);
+  }
+
+  return tree;
+}
diff --git a/src/pages/blog/[...slug].astro b/src/pages/blog/[...slug].astro
index f1df9eb..2f40ee5 100644
--- a/src/pages/blog/[...slug].astro
+++ b/src/pages/blog/[...slug].astro
@@ -14,9 +14,9 @@ type Props = CollectionEntry<'blog'>;
 
 const post = Astro.props;
 const { slug } = Astro.params;
-const { Content } = await render(post);
+const { Content, headings } = await render(post);
 ---
 
-<BlogPost slug={slug} {...post.data} >
+<BlogPost slug={slug} headings={headings} {...post.data} >
 	<Content />
 </BlogPost>
diff --git a/src/pages/notes/[...slug].astro b/src/pages/notes/[...slug].astro
index 18c4900..23901ff 100644
--- a/src/pages/notes/[...slug].astro
+++ b/src/pages/notes/[...slug].astro
@@ -2,6 +2,7 @@
 import RootLayout from '../../layouts/RootLayout.astro';
 import NotchedBox from '../../components/NotchedBox.astro';
 import FormattedDate from '../../components/FormattedDate.astro';
+import TableOfContents from '../../components/TableOfContents.astro';
 import { type CollectionEntry, getCollection } from 'astro:content';
 import { render } from 'astro:content';
 
@@ -15,7 +16,7 @@ export async function getStaticPaths() {
 type Props = CollectionEntry<'notes'>;
 
 const note = Astro.props;
-const { Content } = await render(note);
+const { Content, headings } = await render(note);
 ---
 
 <RootLayout>
@@ -24,6 +25,7 @@ const { Content } = await render(note);
     <div class="last-updated">
       Last updated <FormattedDate date={note.data.updated} />
     </div>
+    <TableOfContents headings={headings}/>
     <Content />
   </NotchedBox>
 </RootLayout>