// https://github.com/jxnblk/css-box-shadow/blob/master/index.js

const VALUES_REG = /,(?![^\(]*\))/;
const PARTS_REG = /\s(?![^(]*\))/;
const LENGTH_REG = /^[0-9]+[a-zA-Z%]+?$/;

const parseValue = (str: string) => {
  const parts = str.split(PARTS_REG);
  const inset = parts.includes("inset");
  const last = parts.slice(-1)[0];
  const color = !isLength(last) ? last : undefined;

  const nums = parts
    .filter((n) => n !== "inset")
    .filter((n) => n !== color)
    .map(toNum);
  const [x, y, blur, spread] = nums;

  return {
    inset,
    x,
    y,
    blur,
    spread,
    color,
  };
};

const isLength = (v) => v === "0" || LENGTH_REG.test(v);
const toNum = (v) => {
  if (!/px$/.test(v) && v !== "0") return v;
  const n = parseFloat(v);
  return !isNaN(n) ? n : v;
};

export const parseBoxShadow = (str: string) =>
  str
    .split(VALUES_REG)
    .map((s) => s.trim())
    .map(parseValue);