From 9a2bb558fd3721f72395e99d8008618fd5db0b30 Mon Sep 17 00:00:00 2001
From: John Factotum <50942278+johnfactotum@users.noreply.github.com>
Date: Thu, 20 Oct 2022 12:50:37 +0000
Subject: [PATCH] Reader: add sidebar and TOC

---
 reader.html | 136 +++++++++++++++++++++++++++++++++++++-----
 reader.js   |  30 +++++++++-
 ui/tree.js  | 169 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 320 insertions(+), 15 deletions(-)
 create mode 100644 ui/tree.js

diff --git a/reader.html b/reader.html
index 9e101f2..5913067 100644
--- a/reader.html
+++ b/reader.html
@@ -4,9 +4,6 @@
 <meta name="viewport" content="width=device-width, initial-scale=1">
 <meta http-equiv="Content-Security-Policy" content="default-src 'self' blob:; script-src 'self'; style-src 'self' blob: 'unsafe-inline'; img-src 'self' blob: data:; connect-src 'self' blob: data:; frame-src blob: data:; object-src 'none'; form-action 'none';">
 <style>
-* {
-    box-sizing: border-box;
-}
 body {
     margin: 0;
     font-family: system-ui, sans-serif;
@@ -17,10 +14,15 @@ body {
     align-items: center;
     justify-content: center;
 }
-#nav-bar {
-    visibility: hidden;
+.icon {
+    display: block;
+    fill: none;
+    stroke: currentcolor;
+    stroke-width: 2px;
+}
+.toolbar {
+    box-sizing: border-box;
     position: absolute;
-    bottom: 0;
     z-index: 1;
     display: flex;
     align-items: center;
@@ -30,33 +32,139 @@ body {
     padding: 6px;
     opacity: .25;
     transition: opacity 250ms ease;
+    visibility: hidden;
 }
-#nav-bar:hover {
+.toolbar:hover {
     opacity: 1;
 }
-#nav-bar button {
+.toolbar button {
     padding: 3px;
     border-radius: 6px;
     background: none;
     border: 0;
 }
-#nav-bar button:hover {
+.toolbar button:hover {
     background: rgba(0, 0, 0, .1);
 }
+#header-bar {
+    top: 0;
+}
+#nav-bar {
+    bottom: 0;
+}
 #progress-label {
     font-size: small;
     font-variant-numeric: tabular-nums;
 }
-.icon {
+#side-bar {
+    visibility: hidden;
+    box-sizing: border-box;
+    position: absolute;
+    z-index: 2;
+    top: 0;
+    left: 0;
+    height: 100%;
+    width: 320px;
+    transform: translateX(-320px);
+    display: flex;
+    flex-direction: column;
+    background: Canvas;
+    color: CanvasText;
+    box-shadow: 0 0 0 1px rgba(0, 0, 0, .2), 0 0 40px rgba(0, 0, 0, .2);
+    transition: visibility 0s linear 300ms, transform 300ms ease;
+}
+#side-bar.show {
+    visibility: visible;
+    transform: translateX(0);
+    transition-delay: 0s;
+}
+#dimming-overlay {
+    visibility: hidden;
+    position: fixed;
+    z-index: 2;
+    top: 0;
+    left: 0;
+    width: 100%;
+    height: 100%;
+    background: rgba(0, 0, 0, .2);
+    opacity: 0;
+    transition: visibility 0s linear 300ms, opacity 300ms ease;
+}
+#dimming-overlay.show {
+    visibility: visible;
+    opacity: 1;
+    transition-delay: 0s;
+}
+#toc-view {
+    padding: .5rem;
+    overflow-y: scroll;
+    --active-bg: rgba(0, 0, 0, .05);
+}
+@supports (color-scheme: light dark) {
+    @media (prefers-color-scheme: dark) {
+        #toc-view {
+            --active-bg: rgba(255, 255, 255, .1);
+        }
+    }
+}
+#toc-view li, #toc-view ol {
+    margin: 0;
+    padding: 0;
+    list-style: none;
+}
+#toc-view a, #toc-view span {
     display: block;
-    fill: none;
-    stroke: currentcolor;
-    stroke-width: 2px;
+    border-radius: 6px;
+    padding: 8px;
+    margin: 2px 0;
+}
+#toc-view a {
+    color: CanvasText;
+    text-decoration: none;
+}
+#toc-view a:hover {
+    background: var(--active-bg);
+}
+#toc-view span {
+    color: GrayText;
+}
+#toc-view svg {
+    margin-inline-start: -24px;
+    padding-inline-start: 5px;
+    padding-inline-end: 6px;
+    fill: CanvasText;
+    cursor: default;
+    transition: transform .2s ease;
+    opacity: .5;
+}
+#toc-view svg:hover {
+    opacity: 1;
+}
+#toc-view [aria-current] {
+    font-weight: bold;
+    background: var(--active-bg);
+}
+#toc-view [aria-expanded="false"] svg {
+    transform: rotate(-90deg);
+}
+#toc-view [aria-expanded="false"] + [role="group"] {
+    display: none;
 }
 </style>
 <input type="file" id="file-input" hidden>
 <div id="drop-target" class="filter">Drop a file here to open it.</div>
-<div id="nav-bar">
+<div id="dimming-overlay" aria-hidden="true"></div>
+<div id="side-bar">
+    <div id="toc-view"></div>
+</div>
+<div id="header-bar" class="toolbar">
+    <button id="side-bar-button" aria-label="Show sidebar">
+        <svg class="icon" width="24" height="24" aria-hidden="true">
+            <path d="M 4 6 h 16 M 4 12 h 16 M 4 18 h 16"/>
+        </svg>
+    </button>
+</div>
+<div id="nav-bar" class="toolbar">
     <button id="left-button" aria-label="Turn left page">
         <svg class="icon" width="24" height="24" aria-hidden="true">
             <path d="M 15 6 L 9 12 L 15 18"/>
diff --git a/reader.js b/reader.js
index 7405c27..d45272d 100644
--- a/reader.js
+++ b/reader.js
@@ -1,5 +1,6 @@
 /* global zip: false, fflate: false */
 import { View } from './view.js'
+import { createTOCView } from './ui/tree.js'
 
 const { ZipReader, BlobReader, TextWriter, BlobWriter } = zip
 zip.configure({ useWebWorkers: false })
@@ -102,16 +103,19 @@ const $ = document.querySelector.bind(document)
 const locales = 'en'
 const percentFormat = new Intl.NumberFormat(locales, { style: 'percent' })
 
+let setCurrentHref
+
 const emit = obj => {
     console.debug(obj)
     switch (obj.type) {
         case 'relocated': {
-            const { fraction, location, pageItem } = obj
+            const { fraction, location, tocItem, pageItem } = obj
             const percent = percentFormat.format(fraction)
             const loc = pageItem
                 ? `Page ${pageItem.label}`
                 : `Loc ${location.current}`
             $('#progress-label').innerText = `${percent} · ${loc}`
+            if (tocItem?.href) setCurrentHref?.(tocItem.href)
             break
         }
     }
@@ -133,6 +137,30 @@ const dropHandler = e => {
                 }
                 view.setAppearance({ css: getCSS(style) })
                 view.renderer.next()
+
+                const closeSideBar = () => {
+                    $('#dimming-overlay').classList.remove('show')
+                    $('#side-bar').classList.remove('show')
+                }
+
+                const toc = view.book.toc
+                if (toc) {
+                    const onclick = href => {
+                        view.goTo(href).catch(e => console.error(e))
+                        closeSideBar()
+                    }
+                    const tocView = createTOCView(toc, onclick)
+                    setCurrentHref = tocView.setCurrentHref
+                    $('#toc-view').append(tocView.element)
+                }
+
+                $('#header-bar').style.visibility = 'visible'
+                $('#side-bar-button').addEventListener('click', () => {
+                    $('#dimming-overlay').classList.add('show')
+                    $('#side-bar').classList.add('show')
+                })
+                $('#dimming-overlay').addEventListener('click', closeSideBar)
+
                 $('#nav-bar').style.visibility = 'visible'
                 $('#left-button').addEventListener('click', () => view.goLeft())
                 $('#right-button').addEventListener('click', () => view.goRight())
diff --git a/ui/tree.js b/ui/tree.js
new file mode 100644
index 0000000..7ee85b4
--- /dev/null
+++ b/ui/tree.js
@@ -0,0 +1,169 @@
+const createSVGElement = tag =>
+    document.createElementNS('http://www.w3.org/2000/svg', tag)
+
+const createExpanderIcon = () => {
+    const svg = createSVGElement('svg')
+    svg.setAttribute('viewBox', '0 0 13 10')
+    svg.setAttribute('width', '13')
+    svg.setAttribute('height', '13')
+    const polygon = createSVGElement('polygon')
+    polygon.setAttribute('points', '2 1, 12 1, 7 9')
+    svg.append(polygon)
+    return svg
+}
+
+const createTOCItemElement = (list, map, onclick) => {
+    let count = 0
+    const makeID = () => `toc-element-${count++}`
+    const createItem = ({ label, href, subitems }, depth = 0) => {
+        const a = document.createElement(href ? 'a' : 'span')
+        a.innerText = label
+        a.setAttribute('role', 'treeitem')
+        a.tabIndex = -1
+        a.style.paddingInlineStart = `${(depth + 1) * 24}px`
+        list.push(a)
+        if (href) {
+            if (!map.has(href)) map.set(href, a)
+            a.href = href
+            a.onclick = event => {
+                event.preventDefault()
+                onclick(href)
+            }
+        } else a.onclick = event => a.firstElementChild?.onclick(event)
+
+        const li = document.createElement('li')
+        li.setAttribute('role', 'none')
+        li.append(a)
+        if (subitems?.length) {
+            a.setAttribute('aria-expanded', 'false')
+            const expander = createExpanderIcon()
+            expander.onclick = event => {
+                event.preventDefault()
+                event.stopPropagation()
+                const expanded = a.getAttribute('aria-expanded')
+                a.setAttribute('aria-expanded', expanded === 'true' ? 'false' : 'true')
+            }
+            a.prepend(expander)
+            const ol = document.createElement('ol')
+            ol.id = makeID()
+            ol.setAttribute('role', 'group')
+            a.setAttribute('aria-owns', ol.id)
+            ol.replaceChildren(...subitems.map(item => createItem(item, depth + 1)))
+            li.append(ol)
+        }
+        return li
+    }
+    return createItem
+}
+
+// https://www.w3.org/TR/wai-aria-practices-1.2/examples/treeview/treeview-navigation.html
+export const createTOCView = (toc, onclick) => {
+    const $toc = document.createElement('ol')
+    $toc.setAttribute('role', 'tree')
+    const list = []
+    const map = new Map()
+    const createItem = createTOCItemElement(list, map, onclick)
+    $toc.replaceChildren(...toc.map(item => createItem(item)))
+
+    const isTreeItem = item => item?.getAttribute('role') === 'treeitem'
+    const getParents = function* (el) {
+        for (let parent = el.parentNode; parent !== $toc; parent = parent.parentNode) {
+            const item = parent.previousElementSibling
+            if (isTreeItem(item)) yield item
+        }
+    }
+
+    let currentItem, currentVisibleParent
+    $toc.addEventListener('focusout', () => {
+        if (!currentItem) return
+        // reset parent focus from last time
+        if (currentVisibleParent) currentVisibleParent.tabIndex = -1
+        // if current item is visible, let it have the focus
+        if (currentItem.offsetParent) {
+            currentItem.tabIndex = 0
+            return
+        }
+        // current item is hidden; give focus to the nearest visible parent
+        for (const item of getParents(currentItem)) {
+            if (item.offsetParent) {
+                item.tabIndex = 0
+                currentVisibleParent = item
+                break
+            }
+        }
+    })
+
+    const setCurrentHref = href => {
+        if (currentItem) {
+            currentItem.removeAttribute('aria-current')
+            currentItem.tabIndex = -1
+        }
+        const el = map.get(href)
+        if (!el) {
+            currentItem = list[0]
+            currentItem.tabIndex = 0
+            return
+        }
+        for (const item of getParents(el))
+            item.setAttribute('aria-expanded', 'true')
+        el.setAttribute('aria-current', 'page')
+        el.tabIndex = 0
+        el.scrollIntoView({ behavior: 'smooth', block: 'center' })
+        currentItem = el
+    }
+
+    const acceptNode = node => isTreeItem(node) && node.offsetParent
+        ? NodeFilter.FILTER_ACCEPT : NodeFilter.FILTER_SKIP
+    const iter = document.createTreeWalker($toc, 1, { acceptNode })
+    const getIter = current => (iter.currentNode = current, iter)
+
+    for (const el of list) el.addEventListener('keydown', event => {
+        let stop = false
+        const { currentTarget, key } = event
+        switch (key) {
+            case ' ':
+            case 'Enter':
+                currentTarget.click()
+                stop = true
+                break
+            case 'ArrowDown':
+                getIter(currentTarget).nextNode()?.focus()
+                stop = true
+                break
+            case 'ArrowUp':
+                getIter(currentTarget).previousNode()?.focus()
+                stop = true
+                break
+            case 'ArrowLeft':
+                if (currentTarget.getAttribute('aria-expanded') === 'true')
+                    currentTarget.setAttribute('aria-expanded', 'false')
+                else getParents(currentTarget).next()?.value?.focus()
+                stop = true
+                break
+            case 'ArrowRight':
+                if (currentTarget.getAttribute('aria-expanded') === 'true')
+                    getIter(currentTarget).nextNode()?.focus()
+                else if (currentTarget.getAttribute('aria-owns'))
+                    currentTarget.setAttribute('aria-expanded', 'true')
+                stop = true
+                break
+            case 'Home':
+                list[0].focus()
+                stop = true
+                break
+            case 'End': {
+                const last = list[list.length - 1]
+                if (last.offsetParent) last.focus()
+                else getIter(last).previousNode()?.focus()
+                stop = true
+                break
+            }
+        }
+        if (stop) {
+            event.preventDefault()
+            event.stopPropagation()
+        }
+    })
+
+    return { element: $toc, setCurrentHref }
+}