import numpy as np

from engine.worldgen.noise import perlin_noise_2d


def test_same_seed_is_deterministic():
    a = perlin_noise_2d(8, 8, seed=42)
    b = perlin_noise_2d(8, 8, seed=42)
    assert np.array_equal(a, b)


def test_different_seeds_produce_different_noise():
    a = perlin_noise_2d(8, 8, seed=1)
    b = perlin_noise_2d(8, 8, seed=2)
    assert not np.array_equal(a, b)


def test_output_shape_matches_width_and_height():
    result = perlin_noise_2d(5, 9, seed=7)
    assert result.shape == (9, 5)


def test_output_is_roughly_normalized_to_zero_one():
    result = perlin_noise_2d(32, 32, seed=3, octaves=4)
    assert result.min() >= 0.0
    assert result.max() <= 1.0
    # not degenerate/constant
    assert result.max() - result.min() > 0.05


def test_offset_sampling_tiles_seamlessly_with_a_direct_full_field_sample():
    # Sampling two adjacent 4-wide windows via x_offset must match sampling the same 8-wide
    # region directly in one call - this is what lets neighboring chunks share one continuous
    # noise field with no seam at the boundary.
    seed = 99
    whole = perlin_noise_2d(8, 4, seed=seed)
    left = perlin_noise_2d(4, 4, seed=seed, x_offset=0)
    right = perlin_noise_2d(4, 4, seed=seed, x_offset=4)
    assert np.allclose(whole[:, :4], left)
    assert np.allclose(whole[:, 4:], right)


def test_y_offset_also_tiles_seamlessly():
    seed = 7
    whole = perlin_noise_2d(4, 8, seed=seed)
    top = perlin_noise_2d(4, 4, seed=seed, y_offset=0)
    bottom = perlin_noise_2d(4, 4, seed=seed, y_offset=4)
    assert np.allclose(whole[:4, :], top)
    assert np.allclose(whole[4:, :], bottom)