import pytest
from aarecommon.math.diffraction_geometry import DiffractionGeometry


@pytest.fixture
def sample_dg():
    return DiffractionGeometry(
        energy_keV=12.4,
        dtz_mm=100.0,
        pixel_size_mm=0.172,
        beam_center_pxl=(1000.0, 1000.0),
        detector_size_pxl=(2000, 2000),
        detector_description="Eiger 16M",
        detector_serial_number="E-123",
        poni_rot1_rad=0.0,
        poni_rot2_rad=0.0,
    )


def test_detector_max_radius_pxl(sample_dg):
    # center (1000, 1000), size (2000, 2000)
    # x0 = 2000-1000 = 1000
    # x1 = 1000
    # y0 = 2000-1000 = 1000
    # y1 = 1000
    # max = 1000
    assert sample_dg.detector_max_radius_pxl == 1000.0


def test_detector_radius_mm(sample_dg):
    # 1000 * 0.172 = 172.0
    assert sample_dg.detector_radius_mm == 172.0


def test_wavelength_angstrom(sample_dg):
    # 12.398 / 12.4 = 0.9998387...
    assert sample_dg.wavelength_angstrom == pytest.approx(0.9998387)


def test_resolution_angstrom(sample_dg):
    # dtz = 100
    # radius = 172
    # theta = atan(172/100) * 0.5 = atan(1.72) * 0.5 = 1.044 * 0.5 = 0.522 rad
    # res = 0.9998 / (2 * sin(0.522)) = 0.9998 / (2 * 0.498) = 1.003
    res = sample_dg.resolution_angstrom(100.0)
    assert res > 0
    assert res == pytest.approx(1.002469, abs=1e-5)

    with pytest.raises(ValueError):
        sample_dg.resolution_angstrom(0)


def test_max_resolution_angstrom(sample_dg):
    assert sample_dg.max_resolution_angstrom == sample_dg.resolution_angstrom(sample_dg.dtz_mm)


def test_calc_dtz_mm(sample_dg):
    res = sample_dg.resolution_angstrom(100.0)
    dtz = sample_dg.calc_dtz_mm(res)
    assert dtz == pytest.approx(100.0)

    with pytest.raises(ValueError):
        sample_dg.calc_dtz_mm(-1)

    # test x >= 1.0 case: wavelength / (2*res) >= 1.0 -> res <= wavelength / 2
    assert sample_dg.calc_dtz_mm(0.0001) == 0.0