const removeHash = (hex: any) => (hex.charAt(0) === '#' ? hex.slice(1) : hex);

const parseHex = (nakedHex: string) => {
  const isShort = nakedHex.length === 3 || nakedHex.length === 4;

  const twoDigitHexR = isShort ? `${nakedHex.slice(0, 1)}${nakedHex.slice(0, 1)}` : nakedHex.slice(0, 2);
  const twoDigitHexG = isShort ? `${nakedHex.slice(1, 2)}${nakedHex.slice(1, 2)}` : nakedHex.slice(2, 4);
  const twoDigitHexB = isShort ? `${nakedHex.slice(2, 3)}${nakedHex.slice(2, 3)}` : nakedHex.slice(4, 6);
  const twoDigitHexA = (isShort ? `${nakedHex.slice(3, 4)}${nakedHex.slice(3, 4)}` : nakedHex.slice(6, 8)) || 'ff';

  // const numericA = +((parseInt(a, 16) / 255).toFixed(2));

  return {
    r: twoDigitHexR,
    g: twoDigitHexG,
    b: twoDigitHexB,
    a: twoDigitHexA,
  };
};

const hexToDecimal = (hex: string) => parseInt(hex, 16);

const hexesToDecimals = ({ r, g, b, a }: { r: string; g: string; b: string; a: string }) => ({
  r: hexToDecimal(r),
  g: hexToDecimal(g),
  b: hexToDecimal(b),
  a: +(hexToDecimal(a) / 255).toFixed(2),
});

const isNumeric = (n: any) => !isNaN(parseFloat(n)) && isFinite(n); // eslint-disable-line no-restricted-globals, max-len

const formatRgb = (decimalObject: { r: number; g: number; b: number; a: number }, parameterA: any) => {
  const { r, g, b, a: parsedA } = decimalObject;
  const a = isNumeric(parameterA) ? parameterA : parsedA;

  return `rgba(${r}, ${g}, ${b}, ${a})`;
};

/**
 * Turns an old-fashioned css hex colour value into a rgb colour value.
 *
 * If you specify an alpha value, you'll get a rgba() value instead.
 *
 * @param The hex value to convert. ('123456'. '#123456', ''123', '#123')
 * @param An alpha value to apply. (optional) ('0.5', '0.25')
 * @return An rgb or rgba value. ('rgb(11, 22, 33)'. 'rgba(11, 22, 33, 0.5)')
 */
const hexToRgba = (hex: any, a: any) => {
  const hashlessHex = removeHash(hex);
  const hexObject = parseHex(hashlessHex);
  const decimalObject = hexesToDecimals(hexObject);

  return formatRgb(decimalObject, a);
};

export default hexToRgba;