uuid.ts

function generateByteHexTable(): string[] {
  const table = new Array(256);
  for (let i = 0; i < 256; i++) {
    table[i] = (i + 0x100).toString(16).substr(1);
  }

  return table;
}

function generateQuadHexTable(): string[] {
  const table = new Array(16);

  for (let i = 0; i < 16; i++) {
    table[i] = (i + 0x10).toString(16).substr(1);
  }

  return table;
}

const byteToHex = generateByteHexTable();
const quadToHex = generateQuadHexTable();

function randByte(): number {
  return Math.floor(Math.random() * 256);
}

export function gen(shard?: number): string {
  const shardValue = shard ?? 0;
  const millis = Date.now();
  const secs = Math.floor(millis / 1000);
  const subsecs = millis % 1000;

  return (
    byteToHex[shardValue] +
    "-" +
    byteToHex[(secs >> 28) & 0xff] +
    byteToHex[(secs >> 20) & 0xff] +
    byteToHex[(secs >> 12) & 0xff] +
    byteToHex[(secs >> 4) & 0xff] +
    quadToHex[secs & 0xf] +
    "-" +
    quadToHex[subsecs >> 8 & 0xf] +
    byteToHex[subsecs & 0xff] +
    "-" +
    byteToHex[randByte()] +
    byteToHex[randByte()] +
    byteToHex[randByte()] +
    byteToHex[randByte()] +
    byteToHex[randByte()] +
    byteToHex[randByte()] +
    byteToHex[randByte()] +
    byteToHex[randByte()] +
    byteToHex[randByte()]
  ).toLowerCase();
}