feat: Add Stories for o-banner demos.

Destroy Method:

Adds a `destroy` method to o-banner. This is used in the o-banner
Story to clean up the close button when re-rendered, which o-banner
dynamically creates on `init`. This is required to support the
`suppressCloseButton` Story control.

Hidden Controls:

It appears banner headings (headingLong/headingShort) should only
be used with the small/compact layout variants. Not with the default
banner style which is full bleed. However it is possible to use
Story controls to create that view.

`@storybook/addon-knobs` (deprecated) allowed dynamic knobs,
so we could hide the heading controls if the default layout
was selected. That's not possible with `@storybook/addon-controls`:
storybookjs/storybook#11984

I think that's probably a good thing. Support for
dynamic controls was worked on but not merge. It's
a poor experience when controls shift around.
storybookjs/storybook#13890

For now this commit hides the layout control on layout
demos, and hides the heading controls from the default
layout demo, to avoid showing the discouraged
heading + layout combination. However it is still
possible to select the base layout with heading on the
theme specific demos, so that the small/compact layout
can also be selected which is allowed.

This could be resolved by exporting 2 templates, one
for each kind of banner / usecase. This could make
components easier to reason with and maintain. For
now this commit sticks to one banner template as
coming up with a name without history / useage
guidelines is difficult, and we don't know that
users aren't already using headings with the base
layout - though we never intended it as far as I
can tell.

No Custom Theme Demo:

The custom theme demo has not been migrated to a Story
yet.
https://registry.origami.ft.com/components/[email protected]#demo-custom-theme

I'm not sure there is value, and maybe harm, in showing
made up customised styles alongside those with brand/design
approval. Plus it's not clear how to re-create the style
without understanding Sass and inspecting demo code.
We probably want to have stories for customised components
at a later date, with improved guidelines around them
and demo Sass/JS pane. See related issue:
#370

No Custom Call To Action Demo:

https://registry.origami.ft.com/components/[email protected]#demo-custom-call-to-action-layout

The description of the demo starts "Although not recommended for
design consistency..." Let's not recomend it with a demo.

components/o-banner/main.js

@@ -3,6 +3,7 @@ import Banner from './src/js/banner.js';
 
 function constructAll () {
 	Banner.init();
+
 	document.removeEventListener('o.DOMContentLoaded', constructAll);
 }
 

components/o-banner/src/js/banner.js

@@ -270,10 +270,20 @@ class Banner {
 		}, {});
 	}
 
+	/**
+	 * Undo the init method
+	 */
+	destroy() {
+		if(this.closeButtonElement) {
+			this.closeButtonElement.remove();
+			delete this.closeButtonElement;
+		}
+	}
+
 	/**
 	 * Initialise banner components.
 	 *
-	 * @param {(HTMLElement | string)} rootElement - The root element to intialise banners in, or a CSS selector for the root element
+	 * @param {(HTMLElement | string)} [rootElement] - The root element to intialise banners in, or a CSS selector for the root element
 	 * @param {object} [options={}] - An options object for configuring the banners
 	 * @returns {Banner | Banner[]} - The newly instantiated Banner (or Banners, if rootElement was not a banner)
 	 */

components/o-banner/src/tsx/banner.tsx

@@ -0,0 +1,105 @@
+export interface BannerSubmitButton {
+	action: string;
+	encoding: string;
+	method: string;
+	copy: string;
+}
+
+export interface BannerLink {
+	copy: string;
+	url: string;
+}
+
+export interface BannerProps {
+	suppressCloseButton?: boolean;
+	headingLong?: string;
+	headingShort?: string;
+	contentLong: string;
+	contentShort?: string;
+	closeButtonLabel?: string;
+	primaryAction?: BannerLink | BannerSubmitButton;
+	secondaryAction?: BannerLink
+	theme: 'product' | 'marketing' | '';
+	layout: 'small' | 'compact' | '';
+}
+
+function isBannerSubmitButton(action: BannerSubmitButton | BannerLink): action is BannerSubmitButton {
+	return (action as BannerSubmitButton).action !== undefined;
+}
+
+export function Banner({
+	suppressCloseButton = false,
+	headingLong = '',
+	headingShort = '',
+	contentLong = 'Hello!',
+	contentShort = '',
+	closeButtonLabel = 'Close',
+	primaryAction = {
+		copy: 'OK',
+		url: '#',
+	},
+	secondaryAction = undefined,
+	theme = '',
+	layout = '',
+}: BannerProps) {
+	const classNames = ['o-banner'];
+	const dataAttributes = {};
+
+	if(layout) {
+		classNames.push(`o-banner--${layout}`);
+	}
+
+	if(theme) {
+		classNames.push(`o-banner--${theme}`);
+	}
+
+	if(suppressCloseButton) {
+		dataAttributes['data-o-banner-suppress-close-button'] = true;
+	}
+
+	return (
+		<div className={classNames.join(' ')} {...dataAttributes} data-o-component="o-banner">
+			<div className="o-banner__outer">
+				<div className="o-banner__inner" data-o-banner-inner>
+					{contentLong && (
+					<div className="o-banner__content o-banner__content--long">
+						{headingLong && (
+						<header className="o-banner__heading">
+							<h2>{headingLong}</h2>
+						</header>
+						)}
+						<p>{contentLong}</p>
+					</div>
+					)}
+					{contentShort && (
+					<div className="o-banner__content o-banner__content--short">
+						{headingShort && (
+						<header className="o-banner__heading">
+							<h2>{headingShort}</h2>
+						</header>
+						)}
+						<p>{contentShort}</p>
+					</div>
+					)}
+					<div className="o-banner__actions">
+						{primaryAction && !isBannerSubmitButton(primaryAction) && (
+							<div className="o-banner__action">
+								<a href="{primaryAction.url}" className="o-banner__button">{primaryAction.copy}</a>
+							</div>
+						)}
+						{primaryAction && isBannerSubmitButton(primaryAction) && (
+							<form className="o-banner__action" method="{primaryAction.method}" encType="{primaryAction.encoding}" action="{primaryAction.action}">
+								<input className="o-banner__button" type="submit" value="{primaryAction.copy}" />
+							</form>
+						)}
+						{secondaryAction && (
+							<div className="o-banner__action o-banner__action--secondary">
+								<a href="{secondaryAction.url}" className="o-banner__link">{secondaryAction.copy}</a>
+							</div>
+						)}
+					</div>
+				</div>
+			</div>
+		</div>
+		);
+	}

components/o-banner/stories/banner.scss

@@ -0,0 +1,7 @@
+@import "@financial-times/o-fonts/main";
+@import "@financial-times/o-normalise/main";
+@include oFonts();
+@include oNormalise();
+
+@import "@financial-times/o-banner/main";
+@include oBanner();

components/o-banner/stories/banner.stories.tsx

@@ -0,0 +1,143 @@
+import {withDesign} from 'storybook-addon-designs';
+import {Banner} from '../src/tsx/banner';
+import {useEffect} from 'react';
+import javascript from '../main';
+import './banner.scss';
+import withHtml from 'origami-storybook-addon-html';
+
+export default {
+	title: 'Banner',
+	component: Banner,
+	decorators: [withDesign, withHtml],
+	args: {
+	},
+	parameters: {
+		design: {
+			type: 'figma',
+			url: 'https://www.figma.com/file/MyHQ1qdwYyek5IBdhEEaND/FT-UI-Library?node-id=0%3A1489',
+		},
+		guidelines: {
+			notion: '37cdc7ac2cac4d60a4c9f451c47a4647',
+		},
+		html: {},
+	},
+};
+
+const Story = args => {
+	useEffect(() => {
+		let banners = javascript.init();
+		return function cleanup() {
+			banners = Array.isArray(banners) ? banners : [banners];
+			banners.forEach(banner => banner.destroy());
+		}
+	}, [args.suppressCloseButton]);
+	return <Banner {...args} />;
+};
+
+export const Default = Story.bind({});
+Default.args = {
+	suppressCloseButton: false,
+	contentLong: 'Try the new compact homepage. A list view of today\'s homepage with fewer images.',
+	contentShort: 'Try it now',
+	closeButtonLabel: 'Close',
+	primaryAction: {
+		copy: 'Try it now',
+		url: '#',
+	},
+	secondaryAction: {
+		copy: 'Give feedback',
+		url: '#'
+	},
+	theme: '',
+	layout: ''
+};
+// Exclude layout and heading controls to discourage use of the default layout with a heading.
+// https://github.com/Financial-Times/origami/pull/523
+Default.parameters = {controls: { exclude: ['headingLong', 'headingShort', 'layout'] }};
+
+
+export const Small = Story.bind({});
+Small.args = {
+	suppressCloseButton: false,
+	headingLong: 'FT Compact',
+	headingShort: 'FT Compact',
+	contentLong: 'Try the new compact homepage. A list view of today\'s homepage with fewer images.',
+	contentShort: 'Try it now',
+	closeButtonLabel: 'Close',
+	primaryAction: {
+		copy: 'Try it now',
+		url: '#',
+	},
+	secondaryAction: {
+		copy: 'Give feedback',
+		url: '#'
+	},
+	theme: '',
+	layout: 'small'
+};
+// Exclude layout to discourage use of the default layout with a heading.
+// https://github.com/Financial-Times/origami/pull/523
+Small.parameters = {controls: { exclude: ['layout'] }};
+
+export const Compact = Story.bind({});
+Compact.args = {
+	suppressCloseButton: false,
+	headingLong: 'FT Compact',
+	headingShort: 'FT Compact',
+	contentLong: 'Try the new compact homepage. A list view of today\'s homepage with fewer images.',
+	contentShort: 'Try it now',
+	closeButtonLabel: 'Close',
+	primaryAction: {
+		copy: 'Try it now',
+		url: '#',
+	},
+	secondaryAction: {
+		copy: 'Give feedback',
+		url: '#'
+	},
+	theme: '',
+	layout: 'compact'
+};
+// Exclude layout to discourage use of the default layout with a heading.
+// https://github.com/Financial-Times/origami/pull/523
+Compact.parameters = {controls: { exclude: ['layout'] }};
+
+export const Marketing = Story.bind({});
+Marketing.args = {
+	suppressCloseButton: false,
+	headingLong: 'FT Compact',
+	headingShort: 'FT Compact',
+	contentLong: 'Try the new compact homepage. A list view of today\'s homepage with fewer images.',
+	contentShort: 'Try it now',
+	closeButtonLabel: 'Close',
+	primaryAction: {
+		copy: 'Try it now',
+		url: '#',
+	},
+	secondaryAction: {
+		copy: 'Give feedback',
+		url: '#'
+	},
+	theme: 'marketing',
+	layout: 'small'
+};
+
+export const Product = Story.bind({});
+Product.args = {
+	suppressCloseButton: false,
+	headingLong: 'FT Compact',
+	headingShort: 'FT Compact',
+	contentLong: 'Try the new compact homepage. A list view of today\'s homepage with fewer images.',
+	contentShort: 'Try it now',
+	closeButtonLabel: 'Close',
+	primaryAction: {
+		copy: 'Try it now',
+		url: '#',
+	},
+	secondaryAction: {
+		copy: 'Give feedback',
+		url: '#'
+	},
+	theme: 'product',
+	layout: 'small'
+};