/* Given a backgorund color, should you write on it in black or white ?
 Taken from http://stackoverflow.com/questions/3942878/how-to-decide-font-color-in-white-or-black-depending-on-background-color#comment61936401_3943023
*/

export default function(color, simple) {
	let r = hexToR(color),
		g = hexToG(color),
		b = hexToB(color)

	if (simple) { // The YIQ formula
		return ((r * 0.299 + g * 0.587 + b * 0.114) > 128) ?
				'#000000' : '#ffffff'
	} // else complex formula
	let
		uicolors = [ r / 255, g / 255, b / 255 ],
		c = uicolors.map(c =>
			c <= 0.03928 ?
				c / 12.92 :
				Math.pow((c + 0.055) / 1.055, 2.4)
		),
		L = 0.2126 * c[0] + 0.7152 * c[1] + 0.0722 * c[2]

	return (L > 0.179) ? '#000000' : '#ffffff'
}

/* Hex to RGB conversion:
 * http://www.javascripter.net/faq/hextorgb.htm
 */
let cutHex = h => (h.charAt(0) == '#') ? h.substring(1, 7) : h,
	hexToR = h => parseInt((cutHex(h)).substring(0, 2),16),
	hexToG = h => parseInt((cutHex(h)).substring(2, 4),16),
	hexToB = h => parseInt((cutHex(h)).substring(4, 6),16)