From 0df80d30e776ea9ecd149da61c96932a39786386 Mon Sep 17 00:00:00 2001
From: Toby Zerner <toby.zerner@gmail.com>
Date: Fri, 17 Mar 2023 09:22:41 +1030
Subject: [PATCH] feat: add Disclosure and Accordion elements

---
 index.html                   | 44 ++++++++++++++++-
 src/accordion/README.md      | 45 ++++++++++++++++++
 src/accordion/accordion.ts   | 26 ++++++++++
 src/disclosure/README.md     | 57 ++++++++++++++++++++++
 src/disclosure/disclosure.ts | 92 ++++++++++++++++++++++++++++++++++++
 src/index.ts                 |  2 +
 6 files changed, 265 insertions(+), 1 deletion(-)
 create mode 100644 src/accordion/README.md
 create mode 100644 src/accordion/accordion.ts
 create mode 100644 src/disclosure/README.md
 create mode 100644 src/disclosure/disclosure.ts

diff --git a/index.html b/index.html
index ef7c81b..0cb4b3a 100644
--- a/index.html
+++ b/index.html
@@ -203,10 +203,29 @@
         }
       }
 
-      ui-toolbar {
+      ui-toolbar,
+      ui-accordion {
         display: block;
         border: 2px solid #ccc;
         padding: 10px;
+        margin-top: 10px;
+      }
+
+      ui-accordion h5 {
+        margin: 0;
+      }
+
+      ui-accordion button {
+        width: 100%;
+      }
+
+      .panel.enter-active {
+        transition: opacity 0.2s, transform 0.2s;
+      }
+
+      .panel.enter-from {
+        opacity: 0;
+        transform: translateY(-10px);
       }
     </style>
   </head>
@@ -291,6 +310,25 @@ <h2 id="your-dialog-title-id">Your dialog title</h2>
       <button>Five</button>
     </ui-toolbar>
 
+    <ui-accordion>
+      <ui-disclosure>
+        <h5><button>Section A</button></h5>
+        <div class="panel">
+          <p>Section A content</p>
+          <p>Section A content</p>
+          <p>Section A content</p>
+        </div>
+      </ui-disclosure>
+      <ui-disclosure>
+        <h5><button>Section B</button></h5>
+        <div class="panel">
+          <p>Section B content</p>
+          <p>Section B content</p>
+          <p>Section B content</p>
+        </div>
+      </ui-disclosure>
+    </ui-accordion>
+
     <script type="module">
       import {
         PopupElement,
@@ -299,6 +337,8 @@ <h2 id="your-dialog-title-id">Your dialog title</h2>
         ModalElement,
         AlertsElement,
         ToolbarElement,
+        AccordionElement,
+        DisclosureElement,
       } from 'https://unpkg.com/inclusive-elements?module';
       // } from './src/index.ts';
 
@@ -308,6 +348,8 @@ <h2 id="your-dialog-title-id">Your dialog title</h2>
       window.customElements.define('ui-modal', ModalElement);
       window.customElements.define('ui-alerts', AlertsElement);
       window.customElements.define('ui-toolbar', ToolbarElement);
+      window.customElements.define('ui-accordion', AccordionElement);
+      window.customElements.define('ui-disclosure', DisclosureElement);
     </script>
 
     <script>
diff --git a/src/accordion/README.md b/src/accordion/README.md
new file mode 100644
index 0000000..b28e685
--- /dev/null
+++ b/src/accordion/README.md
@@ -0,0 +1,45 @@
+# Accordion
+
+**A custom element for building accessible accordions.**
+
+The accordion element wraps multiple disclosure elements, and ensures only one of these is expanded at a time.
+
+## Example
+
+```js
+import { AccordionElement } from 'inclusive-elements';
+
+window.customElements.define('ui-accordion', AccordionElement);
+```
+
+```html
+<ui-accordion>
+    <ui-disclosure>
+        <h2>
+            <button type="button">Section A</button>
+        </h2>
+        <div>
+            Details
+        </div>
+    </ui-disclosure>
+    
+    <ui-disclosure>
+        <h2>
+            <button type="button">Section B</button>
+        </h2>
+        <div>
+            Details
+        </div>
+    </ui-disclosure>
+</ui-accordion>
+```
+
+## Behavior
+
+-   Whenever a direct child `<ui-disclosure>` element is opened, sibling `<ui-disclosure>` elements will be closed.
+
+-   If the `required` attribute is present, the `<ui-disclosure>` element that is currently open will be `disabled`.
+
+## Further Reading
+
+-   [WAI-ARIA Authoring Practices: Accordion](https://www.w3.org/WAI/ARIA/apg/patterns/accordion/)
diff --git a/src/accordion/accordion.ts b/src/accordion/accordion.ts
new file mode 100644
index 0000000..ff0963b
--- /dev/null
+++ b/src/accordion/accordion.ts
@@ -0,0 +1,26 @@
+import DisclosureElement from '../disclosure/disclosure';
+
+export default class AccordionElement extends HTMLElement {
+    public connectedCallback(): void {
+        this.addEventListener('open', this.onOpen, { capture: true });
+    }
+
+    public disconnectedCallback(): void {
+        this.removeEventListener('open', this.onOpen, { capture: true });
+    }
+
+    private onOpen = (e: Event) => {
+        this.querySelectorAll<DisclosureElement>(
+            ':scope > ui-disclosure'
+        ).forEach((el) => {
+            el.open = el === e.target;
+            if (this.required) {
+                el.toggleAttribute('disabled', el === e.target);
+            }
+        });
+    };
+
+    get required() {
+        return this.hasAttribute('required');
+    }
+}
diff --git a/src/disclosure/README.md b/src/disclosure/README.md
new file mode 100644
index 0000000..453be5a
--- /dev/null
+++ b/src/disclosure/README.md
@@ -0,0 +1,57 @@
+# Disclosure Widget
+
+**A custom element for building accessible disclosure widgets.**
+
+## Example
+
+```js
+import { DisclosureElement } from 'inclusive-elements';
+
+window.customElements.define('ui-disclosure', DisclosureElement);
+```
+
+```html
+<ui-disclosure>
+    <button type="button">Summary</button>
+    <div>Details</div>
+</ui-disclosure>
+```
+
+## Behavior
+
+-   The first descendant that is a `<button>` or has `role="button"` will be given the `aria-expanded` attribute, which will reflect the open state of the disclosure widget.
+
+-   Clicking the button will toggle the disclosure widget. The `hidden` attribute will be toggled on the content element.
+
+## API
+
+```js
+const disclosure = document.querySelector('ui-disclosure');
+
+// Programatically open and close the widget.
+disclosure.open = true;
+
+disclosure.addEventListener('open', callback);
+disclosure.addEventListener('close', callback);
+```
+
+```css
+/* Transitions can be applied to the content using hello-goodbye */
+@media (prefers-reduced-motion: no-preference) {
+    ui-disclosure > .enter-active,
+    ui-disclosure > .leave-active {
+        transition: all 0.5s;
+    }
+
+    ui-disclosure > .enter-from,
+    ui-disclosure > .leave-to {
+        opacity: 0;
+        transform: scale(0.5);
+    }
+}
+```
+
+## Further Reading
+
+-   [WAI-ARIA Authoring Practices: Disclosure](https://www.w3.org/WAI/ARIA/apg/patterns/disclosure/)
+-   [Scott O'Hara: The details and summary elements, again](https://www.scottohara.me/blog/2022/09/12/details-summary.html)
diff --git a/src/disclosure/disclosure.ts b/src/disclosure/disclosure.ts
new file mode 100644
index 0000000..388be72
--- /dev/null
+++ b/src/disclosure/disclosure.ts
@@ -0,0 +1,92 @@
+import { cancel, goodbye, hello } from 'hello-goodbye';
+import { shouldOpenInNewTab } from '../utils';
+
+export default class DisclosureElement extends HTMLElement {
+    static get observedAttributes() {
+        return ['open'];
+    }
+
+    public connectedCallback(): void {
+        this.content.hidden = !this.open;
+
+        this.button.setAttribute('aria-expanded', String(this.open));
+
+        this.button.addEventListener('click', this.onButtonClick);
+    }
+
+    public disconnectedCallback(): void {
+        cancel(this.content);
+
+        this.button.removeAttribute('aria-expanded');
+        this.button.removeEventListener('click', this.onButtonClick);
+    }
+
+    private onButtonClick = (e: MouseEvent) => {
+        if (!shouldOpenInNewTab(e) && !this.disabled) {
+            this.open = !this.open;
+            e.preventDefault();
+        }
+    };
+
+    get open() {
+        return this.hasAttribute('open');
+    }
+
+    set open(val) {
+        if (val) {
+            this.setAttribute('open', '');
+        } else {
+            this.removeAttribute('open');
+        }
+    }
+
+    get disabled() {
+        return this.hasAttribute('disabled');
+    }
+
+    public attributeChangedCallback(
+        name: string,
+        oldValue: string,
+        newValue: string
+    ): void {
+        if (name !== 'open') return;
+
+        if (newValue !== null) {
+            this.wasOpened();
+        } else {
+            this.wasClosed();
+        }
+    }
+
+    private wasOpened() {
+        if (!this.content.hidden) return;
+
+        this.content.hidden = false;
+
+        hello(this.content);
+
+        this.button.setAttribute('aria-expanded', 'true');
+
+        this.dispatchEvent(new Event('open'));
+    }
+
+    private wasClosed() {
+        if (this.content.hidden) return;
+
+        this.button.setAttribute('aria-expanded', 'false');
+
+        goodbye(this.content, {
+            finish: () => (this.content.hidden = true),
+        });
+
+        this.dispatchEvent(new Event('close'));
+    }
+
+    private get button(): HTMLElement {
+        return this.querySelector('button, [role=button]')!;
+    }
+
+    private get content(): HTMLElement {
+        return this.children[1] as HTMLElement;
+    }
+}
diff --git a/src/index.ts b/src/index.ts
index 183420a..ea64c01 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,4 +1,6 @@
+export { default as AccordionElement } from './accordion/accordion';
 export { default as AlertsElement } from './alerts/alerts';
+export { default as DisclosureElement } from './disclosure/disclosure';
 export { default as MenuElement } from './menu/menu';
 export { default as ModalElement } from './modal/modal';
 export { default as PopupElement } from './popup/popup';