import * as crypto from "crypto";
import basex from "base-x";

/**
 * Generates a random, cryptographically secure token using uppercase, readable characters.
 * Characters that are used: ABCDEFGHJKMNPQRSTUVWXYZ23456789
 * @param {number} length - length of the token
 * @returns {string}
 */
export function generateSessionToken(length: number): string {
    if (length < 1) throw new Error("invalid length. length must be greater than 0");
    const base31Tokens = "ABCDEFGHJKMNPQRSTUVWXYZ23456789";
    const base31 = basex(base31Tokens);

    const byteLength = Math.ceil((length * Math.log(256)) / Math.log(base31Tokens.length)) + 2;

    const buffer = crypto.randomBytes(Math.ceil(byteLength));
    const token = base31.encode(buffer);

    return token.substring(0, length);
}