"""Pure-geometry tests for :class:`gowelcome.types.RoadInfo` and
:class:`gowelcome.types.Detection` derived properties. No cv2 / SDK / hardware.
"""

from __future__ import annotations

import pytest

from gowelcome.types import Detection, RoadInfo


# --------------------------------------------------------------------------- #
# RoadInfo.clearer_side
# --------------------------------------------------------------------------- #
def test_clearer_side_prefers_right_when_right_has_less_road():
    """Less road on the right (right <= left) -> clearer_side +1 (right is the clear side).

    Note: clearer_side is a *side index* (+1 = right), not a yaw sign; the state
    machine negates it to obtain the CW/right turn that steers away from the road.
    """
    info = RoadInfo(coverage=0.5, left=0.8, center=0.5, right=0.1)
    assert info.clearer_side == 1


def test_clearer_side_prefers_left_when_left_has_less_road():
    """Less road on the left -> -1."""
    info = RoadInfo(coverage=0.5, left=0.1, center=0.5, right=0.8)
    assert info.clearer_side == -1


def test_clearer_side_ties_to_right():
    """Equal coverage is a tie; the contract resolves ties to +1 (right)."""
    info = RoadInfo(coverage=0.4, left=0.4, center=0.4, right=0.4)
    assert info.clearer_side == 1


def test_clearer_side_is_pure_without_mask():
    """clearer_side works with mask=None (no cv2 involvement)."""
    info = RoadInfo(coverage=0.0, left=0.2, center=0.0, right=0.05, mask=None)
    assert info.mask is None
    assert info.clearer_side == 1


# --------------------------------------------------------------------------- #
# Detection geometry
# --------------------------------------------------------------------------- #
def test_detection_centroid_and_dimensions():
    """cx, cy, w, h, area are computed from the corners."""
    det = Detection(label="person", conf=0.9, x1=100, y1=200, x2=300, y2=500)
    assert det.cx == pytest.approx(200.0)   # (100 + 300) / 2
    assert det.cy == pytest.approx(350.0)   # (200 + 500) / 2
    assert det.w == pytest.approx(200.0)
    assert det.h == pytest.approx(300.0)
    assert det.area == pytest.approx(200.0 * 300.0)


def test_detection_height_ratio():
    """height_ratio is box height over frame height."""
    det = Detection(label="person", conf=0.9, x1=0, y1=120, x2=50, y2=360)
    # h = 240, frame_h = 480 -> 0.5
    assert det.height_ratio(480) == pytest.approx(0.5)


def test_detection_height_ratio_guards_zero_frame():
    """A zero/garbage frame height does not divide-by-zero."""
    det = Detection(label="person", conf=0.9, x1=0, y1=0, x2=10, y2=100)
    # max(1, frame_h) guard -> finite result.
    val = det.height_ratio(0)
    assert val == pytest.approx(100.0)


def test_detection_horizontal_offset_centre_is_zero():
    """A box centred in the frame has ~zero horizontal offset."""
    frame_w = 640
    det = Detection(label="person", conf=0.9, x1=300, y1=0, x2=340, y2=10)  # cx=320
    assert det.horizontal_offset(frame_w) == pytest.approx(0.0)


def test_detection_horizontal_offset_sign_right_positive():
    """A box right of centre has a positive (+) offset, left has negative (-)."""
    frame_w = 640
    right = Detection(label="person", conf=0.9, x1=600, y1=0, x2=640, y2=10)
    left = Detection(label="person", conf=0.9, x1=0, y1=0, x2=40, y2=10)
    assert right.horizontal_offset(frame_w) > 0.0
    assert left.horizontal_offset(frame_w) < 0.0


def test_detection_horizontal_offset_full_right_near_one():
    """A box hard against the right edge approaches +1."""
    frame_w = 640
    det = Detection(label="person", conf=0.9, x1=636, y1=0, x2=640, y2=10)  # cx=638
    off = det.horizontal_offset(frame_w)
    assert 0.9 < off <= 1.0