import { randomBytes } from "@/worker/auth/bytes";
import { HOST_WORDS } from "@/worker/auth/host-wordlist";

const wordSet = new Set<string>(HOST_WORDS);
const hostLabelRe = /^[a-z]+(-[a-z]+){4}$/;

function randomWordIndex(): number {
  const length = HOST_WORDS.length;
  const max = 65_536 - (65_536 % length);

  while (true) {
    const bytes = randomBytes(2);
    const value = (bytes[0] << 8) | bytes[1];
    if (value < max) return value % length;
  }
}

export function isValidHostLabel(label: string): boolean {
  if (label.length > 63 || !hostLabelRe.test(label)) return false;
  return label.split("-").every((word) => wordSet.has(word));
}

export function generateHostLabel(): string {
  for (let attempt = 0; attempt < 100; attempt += 1) {
    const words = Array.from({ length: 5 }, () => HOST_WORDS[randomWordIndex()]);
    const label = words.join("-");
    if (label.length <= 63) return label;
  }

  throw new Error("Unable to generate a host label under 64 characters");
}