"""n3xd_ocp.measure — the batched face measurement.

Checked against the same per-face reference the Inc 1 gate uses, which is
recorded from the stock wheel: the batched scan has to agree with calling
BRepGProp.SurfaceProperties once per face, in the same MapShapes(FACE) order,
or the anchor path would resolve against different numbers.
"""

from __future__ import annotations

import pytest

np = pytest.importorskip("numpy")

import n3xd_ocp
from OCP.BRepGProp import BRepGProp
from OCP.BRepPrimAPI import BRepPrimAPI_MakeBox
from OCP.GProp import GProp_GProps
from OCP.TopAbs import TopAbs_FACE

from .test_inc1_modeling import sub_shapes


def _per_face(shape, eps=None):
    """The one-call-per-face loop this API exists to replace."""
    rows = []
    for face in sub_shapes(shape, TopAbs_FACE):
        props = GProp_GProps()
        if eps is None:
            BRepGProp.SurfaceProperties_s(face, props)
        else:
            BRepGProp.SurfaceProperties_s(face, props, eps)
        centre = props.CentreOfMass()
        rows.append((props.Mass(), (centre.X(), centre.Y(), centre.Z())))
    return rows


def test_matches_the_stock_reference(inc1_or_skip, fixture_shapes):
    for name, expected in inc1_or_skip["face_props"].items():
        areas, centroids = n3xd_ocp.measure.face_surface_props(fixture_shapes[name])
        assert areas.shape == (len(expected),), name
        assert centroids.shape == (len(expected), 3), name
        for i, row in enumerate(expected):
            assert areas[i] == pytest.approx(row[0], rel=1e-9), f"{name}[{i}].area"
            assert centroids[i] == pytest.approx(row[1:], rel=1e-9, abs=1e-12), (
                f"{name}[{i}].centroid"
            )


def test_matches_the_per_face_loop(fixture_shapes):
    shape = fixture_shapes["cut_cylinder"]
    areas, centroids = n3xd_ocp.measure.face_surface_props(shape)
    for i, (area, centre) in enumerate(_per_face(shape)):
        assert areas[i] == pytest.approx(area, rel=1e-12)
        assert centroids[i] == pytest.approx(centre, rel=1e-12, abs=1e-12)


def test_parallel_and_serial_agree_exactly(fixture_shapes):
    """The parallel path shares one TopoDS_Shape across threads.  If OCCT
    mutated anything reachable from it while measuring, this is where it would
    show — so the comparison is exact, not approximate."""
    shape = fixture_shapes["fused"]
    par = n3xd_ocp.measure.face_surface_props(shape, parallel=True)
    ser = n3xd_ocp.measure.face_surface_props(shape, parallel=False)
    assert np.array_equal(par[0], ser[0])
    assert np.array_equal(par[1], ser[1])


def test_eps_overload_is_reachable(fixture_shapes):
    shape = fixture_shapes["box"]
    areas, _ = n3xd_ocp.measure.face_surface_props(shape, eps=1e-6)
    for i, (area, _centre) in enumerate(_per_face(shape, eps=1e-6)):
        assert areas[i] == pytest.approx(area, rel=1e-12)


def test_empty_shape_returns_empty_arrays(fixture_shapes):
    areas, centroids = n3xd_ocp.measure.face_surface_props(
        fixture_shapes["empty_compound"]
    )
    assert areas.shape == (0,)
    assert centroids.shape == (0, 3)


def test_arrays_own_their_memory(fixture_shapes):
    """The buffers are allocated C++-side and handed over with a capsule
    deleter; the arrays must stay valid once every other reference is gone."""
    import gc

    areas, centroids = n3xd_ocp.measure.face_surface_props(fixture_shapes["box"])
    expected = float(areas.sum())
    gc.collect()
    assert float(areas.sum()) == expected
    assert centroids.base is not None  # the capsule, not the shape


def test_survives_the_shape_being_dropped():
    """Nothing in the result points back into the shape."""
    areas, centroids = n3xd_ocp.measure.face_surface_props(
        BRepPrimAPI_MakeBox(10.0, 20.0, 30.0).Shape()
    )
    assert areas.sum() == pytest.approx(2200.0)
    assert centroids.shape == (6, 3)