use grovewright_core::rng::Rng;

#[test]
fn matches_the_splitmix64_reference_values() {
    let mut rng = Rng::new(0);
    assert_eq!(rng.next_u64(), 0xE220_A839_7B1D_CDAF);
    assert_eq!(rng.next_u64(), 0x6E78_9E6A_A1B9_65F4);
    assert_eq!(rng.next_u64(), 0x06C4_5D18_8009_454F);
}

#[test]
fn the_same_seed_gives_the_same_sequence() {
    let mut a = Rng::new(2026);
    let mut b = Rng::new(2026);
    for _ in 0..1_000 {
        assert_eq!(a.next_u64(), b.next_u64());
    }
}

#[test]
fn different_seeds_give_different_sequences() {
    assert_ne!(Rng::new(1).next_u64(), Rng::new(2).next_u64());
}

#[test]
fn below_stays_inside_the_bound() {
    let mut rng = Rng::new(7);
    for bound in [1u32, 2, 3, 10, 100, 1_000_000, u32::MAX] {
        for _ in 0..1_000 {
            assert!(rng.below(bound) < bound);
        }
    }
}

#[test]
fn below_reaches_every_value_of_a_small_bound() {
    let mut rng = Rng::new(99);
    let mut seen = [false; 6];
    for _ in 0..1_000 {
        seen[rng.below(6) as usize] = true;
    }
    assert_eq!(seen, [true; 6]);
}

#[test]
#[should_panic(expected = "bound must be greater than zero")]
fn below_refuses_a_bound_of_zero() {
    Rng::new(1).below(0);
}