const pad = (num: string, totalChars: number): string => {
	while (num.length < totalChars) {
		num = '0' + num;
	}
	return num;
};

// Ratio is between 0 and 1
const changeColor = (color: string, ratio: number, darker: boolean): string => {
	// Trim trailing/leading whitespace
	color = color.replace(/^\s*|\s*$/, '');

	// Expand three-digit hex
	color = color.replace(/^#?([a-f0-9])([a-f0-9])([a-f0-9])$/i, '#$1$1$2$2$3$3');

	// Calculate ratio
	const difference = Math.round(ratio * 256) * (darker ? -1 : 1);
	// Determine if input is RGB(A)
	const rgb = color.match(
		new RegExp(
			'^rgba?\\(\\s*' +
				'(\\d|[1-9]\\d|1\\d{2}|2[0-4][0-9]|25[0-5])' +
				'\\s*,\\s*' +
				'(\\d|[1-9]\\d|1\\d{2}|2[0-4][0-9]|25[0-5])' +
				'\\s*,\\s*' +
				'(\\d|[1-9]\\d|1\\d{2}|2[0-4][0-9]|25[0-5])' +
				'(?:\\s*,\\s*' +
				'(0|1|0?\\.\\d+))?' +
				'\\s*\\)$',
			'i',
		),
	);
	const alpha = !!rgb && rgb[4] != null ? rgb[4] : null;
	// Convert hex to decimal
	const decimal = !!rgb
		? [rgb[1], rgb[2], rgb[3]]
		: color
				.replace(/^#?([a-f0-9][a-f0-9])([a-f0-9][a-f0-9])([a-f0-9][a-f0-9])/i, (...args) => {
					return parseInt(args[1], 16) + ',' + parseInt(args[2], 16) + ',' + parseInt(args[3], 16);
				})
				.split(/,/);

	// Return RGB(A)
	return !!rgb
		? 'rgb' +
				(alpha !== null ? 'a' : '') +
				'(' +
				Math[darker ? 'max' : 'min'](parseInt(decimal[0], 10) + difference, darker ? 0 : 255) +
				', ' +
				Math[darker ? 'max' : 'min'](parseInt(decimal[1], 10) + difference, darker ? 0 : 255) +
				', ' +
				Math[darker ? 'max' : 'min'](parseInt(decimal[2], 10) + difference, darker ? 0 : 255) +
				(alpha !== null ? ', ' + alpha : '') +
				')'
		: // Return hex
		  [
				'#',
				pad(
					Math[darker ? 'max' : 'min'](parseInt(decimal[0], 10) + difference, darker ? 0 : 255).toString(16),
					2,
				),
				pad(
					Math[darker ? 'max' : 'min'](parseInt(decimal[1], 10) + difference, darker ? 0 : 255).toString(16),
					2,
				),
				pad(
					Math[darker ? 'max' : 'min'](parseInt(decimal[2], 10) + difference, darker ? 0 : 255).toString(16),
					2,
				),
		  ].join('');
};

export const lighterColor = (color: string, ratio?: number): string => {
	if (color && ratio) {
		return changeColor(color, ratio, false);
	}
	return color;
};
export const darkerColor = (color: string, ratio?: number): string => {
	if (color && ratio) {
		return changeColor(color, ratio, true);
	}
	return color;
};