From 59b55882e815f45d35acf41be2a166a61815a8c0 Mon Sep 17 00:00:00 2001
From: Adam Kudrna <adam@adamkudrna.cz>
Date: Mon, 9 Nov 2020 23:54:07 +0100
Subject: [PATCH] WIP Add table of contents to articles (#5)

---
 .eslintrc                                     |  3 +-
 assets/js/table-of-contents.js                | 38 +++++++++++++++++
 assets/scss/main.scss                         |  1 +
 .../06-components/_table-of-contents.scss     | 42 +++++++++++++++++++
 partials/external/tocbot.hbs                  |  1 +
 post.hbs                                      | 12 +++++-
 6 files changed, 95 insertions(+), 2 deletions(-)
 create mode 100644 assets/js/table-of-contents.js
 create mode 100644 assets/scss/styles/06-components/_table-of-contents.scss
 create mode 100644 partials/external/tocbot.hbs

diff --git a/.eslintrc b/.eslintrc
index b751bad..361a0c3 100644
--- a/.eslintrc
+++ b/.eslintrc
@@ -5,7 +5,8 @@
   },
   "globals": {
     "gtag": false,
-    "snippetsData": false
+    "snippetsData": false,
+    "tocbot": false
   },
   "parserOptions": {
     "ecmaVersion": 2020,
diff --git a/assets/js/table-of-contents.js b/assets/js/table-of-contents.js
new file mode 100644
index 0000000..1182f2c
--- /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: 'table-of-contents__link',
+    listClass: 'table-of-contents__list',
+    listItemClass: 'table-of-contents__list__item',
+    scrollSmooth: false,
+    tocSelector: `#${TOC_ID}`,
+  });
+
+  document.getElementById(TOC_ID).classList.add('table-of-contents--active');
+};
+
+const destroyToc = () => {
+  document.getElementById(TOC_ID).classList.remove('table-of-contents--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 013bce6..c1bd530 100644
--- a/assets/scss/main.scss
+++ b/assets/scss/main.scss
@@ -63,6 +63,7 @@
 @forward "styles/06-components/members-form";
 @forward "styles/06-components/navigation";
 @forward "styles/06-components/post-card";
+@forward "styles/06-components/table-of-contents";
 @forward "styles/06-components/text-field";
 
 // 7. Editor
diff --git a/assets/scss/styles/06-components/_table-of-contents.scss b/assets/scss/styles/06-components/_table-of-contents.scss
new file mode 100644
index 0000000..1e07a4d
--- /dev/null
+++ b/assets/scss/styles/06-components/_table-of-contents.scss
@@ -0,0 +1,42 @@
+@use '../../settings/container';
+@use '../../tools/breakpoint';
+@use '../../tools/spacing';
+@use '../../tools/transition';
+@use '../../tools/typography';
+
+$_breakpoint: xl;
+
+.table-of-contents {
+    @include breakpoint.up($_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/partials/external/tocbot.hbs b/partials/external/tocbot.hbs
new file mode 100644
index 0000000..0131916
--- /dev/null
+++ b/partials/external/tocbot.hbs
@@ -0,0 +1 @@
+<script src="https://cdnjs.cloudflare.com/ajax/libs/tocbot/4.12.0/tocbot.min.js"></script>
diff --git a/post.hbs b/post.hbs
index 9d355d2..95c64f5 100644
--- a/post.hbs
+++ b/post.hbs
@@ -86,10 +86,16 @@
 
             </header>
 
+            {{^has tag="galerie"}}
+                <div> {{!-- TOC holder for `position: sticky` --}}
+                    <div id="obsah" class="table-of-contents" hidden></div>
+                </div>
+            {{/has}}
+
             <div class="section section--roomy-bottom">
                 <div class="container container--article">
 
-                    <div class="editor editor--long-text js-nbsp js-external-links js-heading-anchors">
+                    <div class="editor editor--long-text js-nbsp js-external-links js-heading-anchors js-table-of-contents-source">
                         {{content}}
                     </div>
 
@@ -179,6 +185,10 @@
 {{/contentFor}}
 
 {{#contentFor "scripts"}}
+    {{> "external/tocbot"}}
+
+    <script src="{{asset "js/table-of-contents.js"}}"></script>
+
     {{> "external/prism-js"}}
 {{/contentFor}}