import numpy as np

from utils.curve import compute_letterbox, sample_lane_at_ys
from utils.mask_to_lanes import mask_to_lanes


def test_letterbox_roundtrip():
    lb = compute_letterbox(src_w=1280, src_h=720, out_w=640, out_h=360)
    pts = np.array([[100.0, 200.0], [1000.0, 500.0]], dtype=np.float32)
    warped = lb.apply_points(pts)
    restored = lb.invert_points(warped)
    assert np.allclose(pts, restored, atol=1e-3)


def test_letterbox_stays_in_bounds():
    lb = compute_letterbox(src_w=1280, src_h=720, out_w=640, out_h=360)
    corners = np.array([[0, 0], [1279, 719]], dtype=np.float32)
    warped = lb.apply_points(corners)
    assert (warped[:, 0] >= -1).all() and (warped[:, 0] <= 641).all()
    assert (warped[:, 1] >= -1).all() and (warped[:, 1] <= 361).all()


def test_sample_lane_at_ys_interpolates_and_masks():
    lane = [(0.0, 0.0), (10.0, 1.0)]  # x = 10*y
    sample_ys = np.array([0.0, 0.5, 1.0, 1.5], dtype=np.float32)
    xs, valid = sample_lane_at_ys(lane, sample_ys)
    assert valid.tolist() == [True, True, True, False]
    assert np.allclose(xs[:3], [0.0, 5.0, 10.0], atol=1e-4)


def test_mask_to_lanes_separates_instances():
    mask = np.zeros((100, 200), dtype=np.uint8)
    mask[:, 20:24] = 255   # vertical strip -> one lane instance
    mask[:, 150:154] = 255  # another, far apart -> separate instance
    lanes = mask_to_lanes(mask)
    assert len(lanes) == 2
    for lane in lanes:
        assert len(lane) >= 5


def test_mask_to_lanes_drops_small_noise_blobs():
    mask = np.zeros((100, 200), dtype=np.uint8)
    mask[10:12, 10:12] = 255  # tiny 2x2 JPEG-noise-like blob, below MIN_BLOB_AREA
    lanes = mask_to_lanes(mask)
    assert lanes == []