"""n3xd_ocp.helix — OCCT 8.0's TKHelix builder.

The toolkit is new in 8.0 and has no upstream binding to compare against, so
these are property checks rather than a parity gate: the wire has to be a real
helix of the requested pitch and turn count, and the failure modes have to
surface as Python exceptions rather than a silently empty shape.
"""

from __future__ import annotations

import math

import pytest

import n3xd_ocp
from OCP.BRepGProp import BRepGProp
from OCP.GeomAbs import GeomAbs_C1, GeomAbs_C2
from OCP.gp import gp_Ax3, gp_Dir, gp_Pnt
from OCP.GProp import GProp_GProps
from OCP.TopAbs import TopAbs_EDGE
from OCP.TopExp import TopExp
from OCP.TopTools import TopTools_IndexedMapOfShape

AXIS = gp_Ax3(gp_Pnt(0, 0, 0), gp_Dir(0, 0, 1), gp_Dir(1, 0, 0))


def _length(shape) -> float:
    props = GProp_GProps()
    BRepGProp.LinearProperties_s(shape, props)
    return props.Mass()


def _edge_count(shape) -> int:
    edges = TopTools_IndexedMapOfShape()
    TopExp.MapShapes_s(shape, TopAbs_EDGE, edges)
    return edges.Extent()


def test_single_segment_has_the_right_arc_length():
    """One turn of a helix is sqrt(circumference^2 + pitch^2) long."""
    diameter, pitch, turns = 8.0, 1.25, 1.0
    wire, reached = n3xd_ocp.helix.pure_helix(AXIS, diameter, [pitch], [turns])
    expected = turns * math.hypot(math.pi * diameter, pitch)
    assert _length(wire) == pytest.approx(expected, rel=1e-4)
    assert reached > 0.0
    assert _edge_count(wire) >= 1


@pytest.mark.parametrize("turns", [0.5, 3.0, 24.0])
def test_arc_length_scales_with_the_turn_count(turns):
    diameter, pitch = 8.0, 1.25
    wire, _reached = n3xd_ocp.helix.pure_helix(AXIS, diameter, [pitch], [turns])
    expected = turns * math.hypot(math.pi * diameter, pitch)
    assert _length(wire) == pytest.approx(expected, rel=1e-4)


def test_variable_pitch_segments_compose():
    """The array form is the reason this is bound at all — a spring whose
    pitch changes partway is one wire, not two."""
    diameter = 10.0
    wire, _reached = n3xd_ocp.helix.pure_helix(
        AXIS, diameter, [2.0, 5.0], [3.0, 2.0]
    )
    expected = 3.0 * math.hypot(math.pi * diameter, 2.0) + 2.0 * math.hypot(
        math.pi * diameter, 5.0
    )
    assert _length(wire) == pytest.approx(expected, rel=1e-3)


def test_tapered_diameters_via_the_builder():
    """Two segments, so three boundary diameters: 10 -> 8 tapering, then 8 -> 8
    straight.  A tapered thread (NPT) is the reason the array form is bound."""
    builder = n3xd_ocp.helix.BuilderHelix()
    builder.set_parameters(AXIS, [10.0, 8.0, 8.0], [2.0, 2.0], [2.0, 2.0])
    builder.set_approx_parameters(1.0e-4, 8, GeomAbs_C1)
    builder.perform()
    assert builder.error_status() == 0
    # The straight half is exact; the tapered half is longer than a cylinder of
    # its smaller diameter and shorter than one of its larger.
    straight = 2.0 * math.hypot(math.pi * 8.0, 2.0)
    largest = 2.0 * math.hypot(math.pi * 10.0, 2.0)
    total = _length(builder.shape())
    assert straight * 2 < total < straight + largest


def test_the_n_plus_one_diameter_rule_is_enforced():
    """OCCT wants N+1 diameters for N segments and raises
    Standard_ConstructionError otherwise; the binding checks it first so the
    message names the shape it wanted."""
    builder = n3xd_ocp.helix.BuilderHelix()
    with pytest.raises(ValueError, match="N\\+1 diameters"):
        builder.set_parameters(AXIS, [8.0], [1.25], [1.0])
    builder.set_parameters(AXIS, [8.0, 8.0], [1.25], [1.0])  # accepted


def test_continuity_is_selectable():
    wire_c1, _ = n3xd_ocp.helix.pure_helix(
        AXIS, 8.0, [1.25], [2.0], continuity=GeomAbs_C1
    )
    wire_c2, _ = n3xd_ocp.helix.pure_helix(
        AXIS, 8.0, [1.25], [2.0], continuity=GeomAbs_C2
    )
    assert _length(wire_c1) == pytest.approx(_length(wire_c2), rel=1e-3)


def test_mismatched_segment_arrays_are_rejected():
    with pytest.raises(ValueError):
        n3xd_ocp.helix.pure_helix(AXIS, 8.0, [1.0, 2.0], [1.0])
    with pytest.raises(ValueError):
        n3xd_ocp.helix.pure_helix(AXIS, 8.0, [], [])


def test_builder_rejects_ragged_parameters():
    builder = n3xd_ocp.helix.BuilderHelix()
    with pytest.raises(ValueError):
        builder.set_parameters(AXIS, [8.0, 8.0], [1.0], [1.0, 2.0])
    with pytest.raises(ValueError):
        builder.set_parameters(AXIS, [8.0, 8.0], [], [])