// Who may create an account. The administrator picks one of three settings:
//   open    anyone who can reach the server (the original behaviour)
//   invite  only someone with an unused invite code from the administrator
//   closed  nobody new
// The very first account can always be made, so a fresh install can't lock itself out.
import { randomBytes } from 'crypto';

export const SIGNUP_MODES = ['open', 'invite', 'closed'];
export const isSignupMode = (m) => SIGNUP_MODES.includes(m);

// -> { ok: true } or { ok: false, status, error }. `inviteOk` says whether the code given is a valid unused one.
export function checkSignup({ mode, userCount, inviteOk }) {
  if (userCount === 0 || mode === 'open') return { ok: true };
  if (mode === 'closed') return { ok: false, status: 403, error: 'Sign-up is closed. Ask the administrator for an account.' };
  if (!inviteOk) return { ok: false, status: 403, error: 'Sign-up needs an invite code from the administrator.' };
  return { ok: true };
}

// An easy-to-read invite code (no look-alike characters), e.g. K7QP-4MXD-9TRW.
const ALPHABET = 'ABCDEFGHJKMNPQRSTUVWXYZ23456789';
export function generateInviteCode() {
  const chars = Array.from(randomBytes(12), (b) => ALPHABET[b % ALPHABET.length]).join('');
  return `${chars.slice(0, 4)}-${chars.slice(4, 8)}-${chars.slice(8, 12)}`;
}
export const normalizeInviteCode = (code) => String(code ?? '').toUpperCase().replace(/[^A-Z0-9]/g, '').replace(/^(.{4})(.{4})(.{4})$/, '$1-$2-$3');