import { describe, expect, test } from 'bun:test';
import { SeededRng, createSeed, seedFromHex, seedToHex } from './rng';

describe('SeededRng', () => {
  test('is deterministic for the same seed', () => {
    const a = SeededRng.fromSeed([1, 2, 3, 4]);
    const b = SeededRng.fromSeed([1, 2, 3, 4]);
    for (let i = 0; i < 100; i++) expect(a.nextUint32()).toBe(b.nextUint32());
  });

  test('state can be saved and resumed', () => {
    const a = SeededRng.fromSeed([9, 8, 7, 6]);
    a.int(10);
    const resumed = new SeededRng(a.state());
    expect(resumed.int(1000)).toBe(a.int(1000));
  });

  test('int stays in range and is roughly uniform', () => {
    const r = SeededRng.fromSeed([5, 5, 5, 5]);
    const counts = new Array(6).fill(0);
    for (let i = 0; i < 60000; i++) counts[r.int(6)]++;
    for (const c of counts) expect(Math.abs(c - 10000)).toBeLessThan(500);
  });

  test('shuffle is a permutation', () => {
    const r = SeededRng.fromSeed(createSeed());
    const arr = Array.from({ length: 52 }, (_, i) => i);
    const s = r.shuffle(arr);
    expect(s.slice().sort((x, y) => x - y)).toEqual(arr);
  });

  test('hex round trip', () => {
    const seed = createSeed();
    expect(seedFromHex(seedToHex(seed))).toEqual(seed);
  });
});