wp-calypso/packages/components/src/progress-bar/index.tsx

import clsx from 'clsx';
import * as React from 'react';
import ScreenReaderText from '../screen-reader-text';

import './style.scss';

export interface Props {
	value: number;
	total: number;
	color?: string;
	title?: string;
	compact: boolean;
	className?: string;
	isPulsing: boolean;
	canGoBackwards: boolean;
	style?: React.CSSProperties;
}

interface State {
	allTimeMax: number;
}

export default class ProgressBar extends React.PureComponent< Props, State > {
	static defaultProps = {
		total: 100,
		compact: false,
		isPulsing: false,
		canGoBackwards: false,
	};

	static getDerivedStateFromProps( props: Props, state: State ) {
		return {
			allTimeMax: Math.max( state.allTimeMax, props.value ),
		};
	}

	state: State = {
		allTimeMax: this.props.value,
	};

	getCompletionPercentage() {
		const percentage = Math.ceil(
			( ( this.props.canGoBackwards ? this.props.value : this.state.allTimeMax ) /
				this.props.total ) *
				100
		);

		// The percentage should not be allowed to be more than 100
		return Math.min( percentage, 100 );
	}

	renderBar() {
		const { color, title, total, value, style } = this.props;

		let styles: React.CSSProperties = { width: this.getCompletionPercentage() + '%' };
		if ( color ) {
			styles.backgroundColor = color;
		}
		if ( style ) {
			styles = { ...styles, ...style };
		}

		return (
			<div
				aria-valuemax={ total }
				aria-valuemin={ 0 }
				aria-valuenow={ value }
				aria-label="progress bar"
				className="progress-bar__progress"
				role="progressbar"
				style={ styles }
			>
				{ title && <ScreenReaderText>{ title }</ScreenReaderText> }
			</div>
		);
	}

	render() {
		const classes = clsx( this.props.className, 'progress-bar', {
			'is-compact': this.props.compact,
			'is-pulsing': this.props.isPulsing,
		} );
		return <div className={ classes }>{ this.renderBar() }</div>;
	}
}