"""测距计算与有效性判定测试（规格 §3.2/§6.4/§6.6/§7.1/§11.4）。"""

import math

import pytest

from stereo_ranger import (
    Detection,
    StereoConfig,
    confidence_from_cost,
    evaluate_validity,
    forward_distance_m,
    range_error_abs_m,
    range_error_rel,
    solve_range,
    virtual_center_px,
)

CFG = StereoConfig()


def _boxes_for_point(x_m: float, y_m: float, z_m: float, width_px: float = 50.0, height_px: float = 40.0):
    """由左目系 (X, Y, Z) 反推左右目框（同宽，边缘视差 = 中心视差 = F·B/Z）。"""
    d_px = CFG.focal_baseline_px_m / z_m
    x_l = CFG.cx_px + CFG.fx_px * x_m / z_m
    y_l = CFG.cy_px + CFG.fy_px * y_m / z_m
    left = Detection(x_l - width_px / 2, y_l - height_px / 2, x_l + width_px / 2, y_l + height_px / 2)
    right = Detection(
        x_l - width_px / 2 - d_px, y_l - height_px / 2, x_l + width_px / 2 - d_px, y_l + height_px / 2
    )
    return left, right, d_px


def test_solve_range_recovers_ground_truth():
    # §11.4：已知 Z 反推 D 构造框对，断言 Z = F·B/D 回收
    left, right, d_px = _boxes_for_point(0.6, 0.3, 6.0)
    solution = solve_range(left, right, d_px, CFG)
    assert solution.z_m == pytest.approx(6.0)
    assert solution.x_m == pytest.approx(0.6)
    assert solution.y_m == pytest.approx(0.3)
    assert solution.r_m == pytest.approx(math.sqrt(0.6**2 + 0.3**2 + 6.0**2))


def test_forward_distance_rejects_non_positive_disparity():
    with pytest.raises(ValueError):
        forward_distance_m(0.0, CFG)
    with pytest.raises(ValueError):
        forward_distance_m(-2.0, CFG)


def test_virtual_center_equals_midline_camera_projection():
    # §6.6 恒等式：xL = cx + F(X_C + B/2)/Z，xR = cx + F(X_C − B/2)/Z ⇒ c_mid = cx + F·X_C/Z
    z_m = 5.0
    x_center_m = 0.57
    x_l = CFG.cx_px + CFG.fx_px * (x_center_m + CFG.baseline_m / 2.0) / z_m
    x_r = CFG.cx_px + CFG.fx_px * (x_center_m - CFG.baseline_m / 2.0) / z_m
    left = Detection(x_l - 30.0, 480.0, x_l + 30.0, 520.0)
    right = Detection(x_r - 30.0, 480.0, x_r + 30.0, 520.0)
    center_mid = virtual_center_px(left, right)
    assert center_mid[0] == pytest.approx(CFG.cx_px + CFG.fx_px * x_center_m / z_m)
    assert center_mid[1] == pytest.approx(500.0)


def test_error_model_is_quadratic_in_z():
    assert range_error_abs_m(10.0, CFG) == pytest.approx(10.0**2 / CFG.focal_baseline_px_m)
    assert range_error_rel(10.0, CFG) == pytest.approx(10.0 / CFG.focal_baseline_px_m)
    assert range_error_abs_m(20.0, CFG) == pytest.approx(4.0 * range_error_abs_m(10.0, CFG))


def test_validity_gate_1_out_of_domain():
    decision = evaluate_validity(CFG.disparity_min_px - 0.1, 30.0, CFG)
    assert not decision.in_domain and not decision.valid


def test_validity_gate_2_error_budget_blocks_far_field():
    # 域内（D = 4.8 px → Z = 12 m）但 δZ = 2.5 m > 2 m，预算门拦截
    d_px = 4.8
    z_m = CFG.focal_baseline_px_m / d_px
    decision = evaluate_validity(d_px, z_m, CFG)
    assert decision.in_domain and not decision.budget_ok and not decision.valid


def test_validity_gate_2_boundary_sides():
    z_limit = CFG.z_error_budget_max_m
    assert evaluate_validity(CFG.focal_baseline_px_m / z_limit, z_limit * 0.999, CFG).budget_ok
    assert not evaluate_validity(CFG.focal_baseline_px_m / z_limit, z_limit * 1.001, CFG).budget_ok


def test_validity_requires_finite_z():
    assert not evaluate_validity(5.0, None, CFG).valid
    assert not evaluate_validity(5.0, float("inf"), CFG).valid


def test_domain_boundaries_are_inclusive():
    assert evaluate_validity(CFG.disparity_min_px, 19.2, CFG).in_domain
    assert evaluate_validity(CFG.disparity_max_px, 1.0, CFG).in_domain


def test_confidence_from_cost_linear_clamped():
    assert confidence_from_cost(0.0) == pytest.approx(1.0)
    assert confidence_from_cost(0.4) == pytest.approx(0.6)
    assert confidence_from_cost(1.0) == pytest.approx(0.0)
    assert confidence_from_cost(1.5) == pytest.approx(0.0)