@better-auth/utils/dist/random.mjs

A collection of utilities for better-auth

import { getRandomValues } from 'uncrypto';

function expandAlphabet(alphabet) {
  switch (alphabet) {
    case "a-z":
      return "abcdefghijklmnopqrstuvwxyz";
    case "A-Z":
      return "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    case "0-9":
      return "0123456789";
    case "-_":
      return "-_";
    default:
      throw new Error(`Unsupported alphabet: ${alphabet}`);
  }
}
function createRandomStringGenerator(...baseAlphabets) {
  const baseCharSet = baseAlphabets.map(expandAlphabet).join("");
  if (baseCharSet.length === 0) {
    throw new Error(
      "No valid characters provided for random string generation."
    );
  }
  const baseCharSetLength = baseCharSet.length;
  return (length, ...alphabets) => {
    if (length <= 0) {
      throw new Error("Length must be a positive integer.");
    }
    let charSet = baseCharSet;
    let charSetLength = baseCharSetLength;
    if (alphabets.length > 0) {
      charSet = alphabets.map(expandAlphabet).join("");
      charSetLength = charSet.length;
    }
    const maxValid = Math.floor(256 / charSetLength) * charSetLength;
    const buf = new Uint8Array(length * 2);
    const bufLength = buf.length;
    let result = "";
    let bufIndex = bufLength;
    let rand;
    while (result.length < length) {
      if (bufIndex >= bufLength) {
        getRandomValues(buf);
        bufIndex = 0;
      }
      rand = buf[bufIndex++];
      if (rand < maxValid) {
        result += charSet[rand % charSetLength];
      }
    }
    return result;
  };
}

export { createRandomStringGenerator };