import { assert } from "./assert.ts";
import { Option, Options, None, Some } from "./option.ts";

type Prime = number;
const toPrime = function (n: number): Option<Prime> {
  if (!Number.isSafeInteger(n) || n < 2) return None;
  if (n % 2 === 0) return (n !== 2) ? None : Some(n);
  if (n % 3 === 0) return (n !== 3) ? None : Some(n);

  const m = Math.sqrt(n);
  for (let i = 5; i <= m; i += 6) {
    if (n % i === 0) return None;
    if (n % (i + 2) === 0) return None;
  }
  return Some(n);
};
const makeRange = function* (start: number, end: number) {
  let cursor = start;
  while (cursor < end) {
    yield cursor;
    cursor += 1;
  }
  return cursor;
};

const maybePrimes: Option<Prime>[] = [...makeRange(9, 19)].map(toPrime);
const firstPrime = Options.any(maybePrimes);

assert(firstPrime.isSome() === true);
assert(firstPrime.unwrap() === 11);