scripts/calcRgb.js at master · petrosAth/scripts · GitHub

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const process = require("process");

add = (c1, c2) => {
  const octetsRegex = /^([0-9a-f]{2})([0-9a-f]{2})([0-9a-f]{2})$/i;
  const m1 = c1.match(octetsRegex);
  const m2 = c2.match(octetsRegex);
  if (!m1 || !m2) {
    throw new Error(`invalid hex color triplet(s): ${c1} / ${c2}`);
  }
  return [1, 2, 3]
    .map((i) => {
      const sum = parseInt(m1[i], 16) + parseInt(m2[i], 16);
      if (sum > 0xff) {
        throw new Error(
          `octet ${i} overflow: ${m1[i]}+${m2[i]}=${sum.toString(16)}`,
        );
      }
      return sum.toString(16).padStart(2, "0");
    })
    .join("");
};

sub = (c1, c2) => {
  const octetsRegex = /^([0-9a-f]{2})([0-9a-f]{2})([0-9a-f]{2})$/i;
  const m1 = c1.match(octetsRegex);
  const m2 = c2.match(octetsRegex);
  if (!m1 || !m2) {
    throw new Error(`invalid hex color triplet(s): ${c1} / ${c2}`);
  }
  return [1, 2, 3]
    .map((i) => {
      const sum = parseInt(m1[i], 16) - parseInt(m2[i], 16);
      if (sum < 0x00) {
        throw new Error(
          `octet ${i} underflow: ${m1[i]}-${m2[i]}=${sum.toString(16)}`,
        );
      }
      return sum.toString(16).padStart(2, "0");
    })
    .join("");
};

if (process.argv.length === 5 && ["add", "sub"].includes(process.argv[2])) {
  switch (process.argv[2]) {
    case "add":
      console.log(add(process.argv[3], process.argv[4]));
      break;
    case "sub":
      console.log(sub(process.argv[3], process.argv[4]));
      break;
  }
}