from app.possession import compute_stability


def test_rarity_ordering_holds_magnitude_and_rng_constant():
    # Midpoint rng (0.5) zeroes out jitter, isolating the rarity base.
    rng = lambda: 0.5
    common = compute_stability("common", magnitude=50, rng=rng)
    uncommon = compute_stability("uncommon", magnitude=50, rng=rng)
    rare = compute_stability("rare", magnitude=50, rng=rng)
    mythic = compute_stability("mythic", magnitude=50, rng=rng)

    assert common < uncommon < rare < mythic


def test_unknown_rarity_falls_back_to_common_base():
    rng = lambda: 0.5
    assert compute_stability("legendary???", magnitude=50, rng=rng) == compute_stability(
        "common", magnitude=50, rng=rng
    )


def test_magnitude_bonus_increases_stability_up_to_cap():
    rng = lambda: 0.5
    low = compute_stability("common", magnitude=0, rng=rng)
    mid = compute_stability("common", magnitude=10, rng=rng)
    high = compute_stability("common", magnitude=1000, rng=rng)

    assert low < mid < high
    # Bonus caps at 0.15, so magnitude=15 and magnitude=1000 must land the
    # same once base and jitter are held constant.
    at_cap = compute_stability("common", magnitude=15, rng=rng)
    past_cap = compute_stability("common", magnitude=1000, rng=rng)
    assert at_cap == past_cap


def test_jitter_scaled_to_plus_minus_point_one():
    # rng()=0 -> minimum jitter (-0.1); rng()=1 -> maximum jitter (+0.1).
    base = 0.35  # common base
    low_jitter = compute_stability("common", magnitude=0, rng=lambda: 0.0)
    high_jitter = compute_stability("common", magnitude=0, rng=lambda: 1.0)

    assert low_jitter == max(0.05, base - 0.1)
    assert high_jitter == min(0.98, base + 0.1)


def test_clamped_at_lower_bound():
    # common base 0.35 minus full jitter (0.1) minus nothing else is 0.25,
    # comfortably above the floor -- force the floor with a negative-leaning
    # setup instead: rarity base + jitter alone can't go below 0.05, but the
    # clamp itself must still be exercised directly via a pathological rng.
    stability = compute_stability("common", magnitude=0, rng=lambda: -100.0)
    assert stability == 0.05


def test_clamped_at_upper_bound():
    stability = compute_stability("mythic", magnitude=1000, rng=lambda: 100.0)
    assert stability == 0.98


def test_deterministic_with_injected_rng():
    rng = lambda: 0.73
    first = compute_stability("rare", magnitude=42, rng=rng)
    second = compute_stability("rare", magnitude=42, rng=rng)
    assert first == second


def test_default_rng_produces_value_in_range():
    stability = compute_stability("uncommon", magnitude=25)
    assert 0.05 <= stability <= 0.98