From 4e79a4aaffc0e832125b07c8c1ce2e979746e8d8 Mon Sep 17 00:00:00 2001
From: Adam Kudrna <adam@adamkudrna.cz>
Date: Mon, 9 Nov 2020 23:54:07 +0100
Subject: [PATCH] Add table of contents to articles (#5)

---
 .eslintrc                                     |  3 +-
 assets/js/table-of-contents.js                | 38 ++++++++++++++++
 assets/scss/main.scss                         |  1 +
 .../04-components/_table-of-contents.scss     | 44 +++++++++++++++++++
 post.hbs                                      | 13 +++++-
 5 files changed, 97 insertions(+), 2 deletions(-)
 create mode 100644 assets/js/table-of-contents.js
 create mode 100644 assets/scss/styles/04-components/_table-of-contents.scss

diff --git a/.eslintrc b/.eslintrc
index c31d933..ee963ca 100644
--- a/.eslintrc
+++ b/.eslintrc
@@ -4,7 +4,8 @@
     "browser": true
   },
   "globals": {
-    "gtag": false
+    "gtag": false,
+    "tocbot": false
   },
   "parserOptions": {
     "ecmaVersion": 10,
diff --git a/assets/js/table-of-contents.js b/assets/js/table-of-contents.js
new file mode 100644
index 0000000..cd87a55
--- /dev/null
+++ b/assets/js/table-of-contents.js
@@ -0,0 +1,38 @@
+const TOC_ID = 'obsah';
+
+const generateToc = () => {
+  tocbot.init({
+    activeLinkClass: 'is-active',
+    collapsibleClass: 'is-collapsible',
+    contentSelector: '.js-table-of-contents-source',
+    headingSelector: 'h1, h2, h3',
+    isCollapsedClass: 'is-collapsed',
+    linkClass: 'toc__link',
+    listClass: 'toc__list',
+    listItemClass: 'toc__list__item',
+    scrollSmooth: false,
+    tocSelector: `#${TOC_ID}`,
+  });
+
+  document.getElementById(TOC_ID).classList.add('toc--active');
+};
+
+const destroyToc = () => {
+  document.getElementById(TOC_ID).classList.remove('toc--active');
+  tocbot.destroy();
+};
+
+const updateToc = () => {
+  const tocEl = document.getElementById(TOC_ID);
+
+  if (window.getComputedStyle(tocEl).display !== 'none') {
+    if (!tocEl.innerHTML) {
+      generateToc();
+    }
+  } else if (tocEl.innerHTML) {
+    destroyToc();
+  }
+};
+
+window.addEventListener('load', () => updateToc());
+window.addEventListener('resize', () => updateToc());
diff --git a/assets/scss/main.scss b/assets/scss/main.scss
index ff16f00..8419a64 100644
--- a/assets/scss/main.scss
+++ b/assets/scss/main.scss
@@ -52,6 +52,7 @@
 @import 'styles/04-components/navigation';
 @import 'styles/04-components/post-card';
 @import 'styles/04-components/share';
+@import 'styles/04-components/table-of-contents';
 @import 'styles/04-components/text-field';
 
 // 5. Editor
diff --git a/assets/scss/styles/04-components/_table-of-contents.scss b/assets/scss/styles/04-components/_table-of-contents.scss
new file mode 100644
index 0000000..565153e
--- /dev/null
+++ b/assets/scss/styles/04-components/_table-of-contents.scss
@@ -0,0 +1,44 @@
+@use '../../settings/container';
+@use '../../tools/breakpoint';
+@use '../../tools/spacing';
+@use '../../tools/transition';
+@use '../../tools/typography';
+
+$_breakpoint: xl;
+
+.table-of-contents {
+    display: none;
+
+    @include breakpoint.up($_breakpoint) {
+        @include transition.add('visibility, opacity');
+
+        position: sticky;
+        top: 0;
+        right: 0;
+        display: block;
+        visibility: hidden;
+        opacity: 0;
+        width: calc((100vw - #{container.$article-width}) / 2);
+        height: 0;
+        padding: spacing.of(2) container.$padding-sm;
+        line-height: typography.line-height(dense);
+        will-change: visibility, opacity;
+    }
+}
+
+.table-of-contents__list {
+    @include breakpoint.up($_breakpoint) {
+        @include typography.style(small);
+    }
+}
+
+.table-of-contents__list .table-of-contents__list {
+    font-size: inherit;
+}
+
+.table-of-contents--active {
+    @include breakpoint.up($_breakpoint) {
+        visibility: visible;
+        opacity: 1;
+    }
+}
diff --git a/post.hbs b/post.hbs
index b769d5f..0ec6276 100644
--- a/post.hbs
+++ b/post.hbs
@@ -76,10 +76,16 @@
 
             </header>
 
+            {{^has tag="galerie"}}
+                <div class="toc__holder">
+                    <div id="obsah" class="toc" hidden></div>
+                </div>
+            {{/has}}
+
             <div class="section section--dense">
                 <div class="container container--article">
 
-                    <div class="editor js-nbsp js-external-links js-heading-anchors">
+                    <div class="editor js-nbsp js-external-links js-heading-anchors js-table-of-contents-source">
                         {{content}}
                     </div>
 
@@ -155,6 +161,11 @@
 {{/contentFor}}
 
 {{#contentFor "scripts"}}
+    {{!-- Table of Contents --}}
+    <script src="https://cdnjs.cloudflare.com/ajax/libs/tocbot/4.12.0/tocbot.min.js"></script>
+    <script src="{{asset "js/table-of-contents.js"}}"></script>
+
+    {{!-- Code syntax highlighting with Prism.js --}}
     <script src="https://cdnjs.cloudflare.com/ajax/libs/prism/1.22.0/prism.min.js"></script>
     <script src="https://cdnjs.cloudflare.com/ajax/libs/prism/1.22.0/plugins/autoloader/prism-autoloader.min.js"></script>