const HexColor = /^#([A-Fa-f0-9]{6}|[A-Fa-f0-9]{3})$/;
const RgbColor = /^rgb\( *(\d{1,3}), *(\d{1,3}), *(\d{1,3}),? *\)$/;

function expandHexColor(color: string): string {
  if (color.length === 4 && color.charAt(0) === '#') {
    const c = color.split('');
    return `#${c[1]}${c[1]}${c[2]}${c[2]}${c[3]}${c[3]}`;
  }
  return color;
}

function rgbToHex(rgb: string): string {
  if (!RgbColor.test(rgb)) { return rgb; }
  const v = RgbColor.exec(rgb).map(val => parseInt(val).toString(16)).map(hex => hex.length === 1 ? '0' + hex : hex);
  return `#${v[1] + v[2] + v[3]}`;
}

export function ColorEqualityTester(first: string, second: string): boolean | undefined {
  if ((HexColor.test(first) || RgbColor.test(first)) && (HexColor.test(second) || RgbColor.test(second))) {
    return rgbToHex(expandHexColor(first)).toLowerCase() === rgbToHex(expandHexColor(second).toLowerCase());
  }
  return undefined;
}