From a2a2e04fcd623e515d3f106038d8d46f827d4c79 Mon Sep 17 00:00:00 2001
From: lonkaars <loek@pipeframe.xyz>
Date: Sun, 28 Apr 2024 12:28:40 +0200
Subject: fix table of contents

---
 .gitignore         |  1 +
 Gemfile            |  7 ++++++
 _includes/toc.html | 24 ---------------------
 _layouts/post.html |  2 +-
 _plugins/toc.rb    | 62 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 css/navbar.css     |  1 -
 makefile           |  2 +-
 7 files changed, 72 insertions(+), 27 deletions(-)
 create mode 100644 Gemfile
 delete mode 100644 _includes/toc.html
 create mode 100644 _plugins/toc.rb

diff --git a/.gitignore b/.gitignore
index ca77d87..487f1af 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,3 +4,4 @@ _site
 
 .DS_Store
 
+Gemfile.lock
diff --git a/Gemfile b/Gemfile
new file mode 100644
index 0000000..2f7ad5d
--- /dev/null
+++ b/Gemfile
@@ -0,0 +1,7 @@
+ruby '~> 3.0'
+source 'https://rubygems.org'
+
+gem 'jekyll', '~> 4.3'
+gem 'json', '~> 2.7'
+gem 'nokogiri', '~> 1.16'
+
diff --git a/_includes/toc.html b/_includes/toc.html
deleted file mode 100644
index 311864b..0000000
--- a/_includes/toc.html
+++ /dev/null
@@ -1,24 +0,0 @@
-<div class="chapterChildren">
-	<ul>
-		<li class="stub">
-			<details open>
-				<summary><a href="#">1.</a></summary>
-				<ul>
-					<li><a href="#">1.1. a really really really long title here</a></li>
-					<li><a href="#">1.2.</a></li>
-					<li class="stub">
-						<details open>
-							<summary><a href="#">1.3.</a></summary>
-							<ul>
-								<li><a href="#">1.3.1.</a></li>
-								<li><a href="#">1.3.2.</a></li>
-							</ul>
-						</details>
-					</li>
-					<li><a href="#">1.4.</a></li>
-				</ul>
-			</details>
-		</li>
-	</ul>
-</div>
-
diff --git a/_layouts/post.html b/_layouts/post.html
index 7f035af..4597623 100644
--- a/_layouts/post.html
+++ b/_layouts/post.html
@@ -15,7 +15,7 @@
 		<div class='navAreaWrapper'>
 			<div class='sticky'>
 				{% include navbar.html page="post" %}
-				{% include toc.html content=content %}
+				{% toc %}
 			</div>
 		</div>
 		<!-- <MobileNavbar /> -->
diff --git a/_plugins/toc.rb b/_plugins/toc.rb
new file mode 100644
index 0000000..216341d
--- /dev/null
+++ b/_plugins/toc.rb
@@ -0,0 +1,62 @@
+require 'nokogiri'
+
+module Jekyll
+  class TOC < Liquid::Tag
+    def render context
+      # load HTML into nokogiri
+      html = context.registers[:page]['content']
+      doc = Nokogiri::HTML(html)
+
+      # enumerate over all h1-4 headings
+      @els = doc.css("h1, h2, h3, h4")
+      return '<div class="chapterChildren">%s</div>' % [ output_toc ]
+    end
+
+    def output_toc
+      # empty toc (this check prevents crash)
+      return "" if @els.length == 0
+
+      output = '<ul>'
+
+      current_level = el_level(@els[0])
+
+      while @els.length > 0
+        el = @els[0]
+        el_next = @els[1]
+        level = el_level(el)
+        level_next = el_level(el_next || el) # || el to prevent crash on end of list
+
+        if level >= level_next
+          output += '<li>'
+        else
+          output += '<li class="stub"><details open>'
+          output += '<summary>'
+        end
+
+        output += '<a href="#%s">%s</a>' % [ el['id'], el.inner_html ]
+        @els.shift()
+
+        if level >= level_next
+          output += '</li>'
+        else
+          output += '</summary>'
+          output += output_toc
+          output += '</details></li>'
+        end
+
+        break if level_next < level
+      end
+
+      output += '</ul>'
+
+      return output
+    end
+
+    def el_level el
+      return Integer(el.name[1..])
+    end
+  end
+end
+
+Liquid::Template.register_tag('toc', Jekyll::TOC)
+
diff --git a/css/navbar.css b/css/navbar.css
index b6612d5..10933a0 100644
--- a/css/navbar.css
+++ b/css/navbar.css
@@ -143,7 +143,6 @@
 
 .chapterChildren li,
 .chapterChildren summary {
-	display: block;
 	min-height: 24px;
 	padding-left: 32px;
 	position: relative;
diff --git a/makefile b/makefile
index a8578d4..ddbddcd 100644
--- a/makefile
+++ b/makefile
@@ -1,5 +1,5 @@
 build:
-	jekyll build --quiet
+	bundle exec jekyll build --quiet
 
 clean:
 	$(RM) -r _site
-- 
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