from pathlib import Path

import pytest
import numpy as np

import openmc
from openmc.stats import Discrete, Point
from openmc.utility_funcs import change_directory

from tests.testing_harness import HashedPyAPITestHarness


def build_model(shared_secondary):
    openmc.reset_auto_ids()
    model = openmc.Model()

    # materials (M4 steel alloy)
    m4 = openmc.Material()
    m4.set_density('g/cc', 2.3)
    m4.add_nuclide('H1', 0.168018676)
    m4.add_nuclide("O16", 0.561814465)
    m4.add_nuclide("O17", 0.00021401)
    m4.add_nuclide("Na23", 0.021365)
    m4.add_nuclide("Al27", 0.021343)
    m4.add_nuclide("Si28", 0.187439342)
    m4.add_nuclide("Si29", 0.009517714)
    m4.add_nuclide("Si30", 0.006273944)
    m4.add_nuclide("Ca40", 0.018026179)
    m4.add_nuclide("Ca42", 0.00012031)
    m4.add_nuclide("Ca44", 0.000387892)
    m4.add_nuclide("Fe54", 0.000248179)
    m4.add_nuclide("Fe56", 0.003895875)

    s0 = openmc.Sphere(r=240)
    s1 = openmc.Sphere(r=250, boundary_type='vacuum')

    c0 = openmc.Cell(fill=m4, region=-s0)
    c1 = openmc.Cell(region=+s0 & -s1)

    model.geometry = openmc.Geometry([c0, c1])

    # settings
    settings = model.settings
    settings.run_mode = 'fixed source'
    settings.particles = 500
    settings.batches = 2
    settings.max_history_splits = 200
    settings.photon_transport = True
    settings.shared_secondary_bank = shared_secondary
    settings.weight_window_checkpoints = {'surface': True,
                                          'collision': True}
    space = Point((0.001, 0.001, 0.001))
    energy = Discrete([14E6], [1.0])

    settings.source = openmc.IndependentSource(space=space, energy=energy)

    # tally
    mesh = openmc.RegularMesh()
    mesh.lower_left = (-240, -240, -240)
    mesh.upper_right = (240, 240, 240)
    mesh.dimension = (5, 10, 15)

    mesh_filter = openmc.MeshFilter(mesh)

    e_bnds = [0.0, 0.5, 2E7]
    energy_filter = openmc.EnergyFilter(e_bnds)

    particle_filter = openmc.ParticleFilter(['neutron', 'photon'])

    tally = openmc.Tally()
    tally.filters = [mesh_filter, energy_filter, particle_filter]
    tally.scores = ['flux']

    model.tallies.append(tally)

    # weight windows

    # load pre-generated weight windows from parent directory
    parent_dir = Path(__file__).parent
    ww_n_lower_bnds = np.loadtxt(parent_dir / 'ww_n.txt')
    ww_p_lower_bnds = np.loadtxt(parent_dir / 'ww_p.txt')

    # create a mesh matching the one used
    # to generate the weight windows
    ww_mesh = openmc.RegularMesh()
    ww_mesh.lower_left = (-240, -240, -240)
    ww_mesh.upper_right = (240, 240, 240)
    ww_mesh.dimension = (5, 6, 7)

    ww_n = openmc.WeightWindows(ww_mesh,
                                ww_n_lower_bnds,
                                None,
                                10.0,
                                e_bnds,
                                'neutron',
                                max_lower_bound_ratio=1.5)

    ww_p = openmc.WeightWindows(ww_mesh,
                                ww_p_lower_bnds,
                                None,
                                10.0,
                                e_bnds,
                                'photon',
                                max_lower_bound_ratio=1.5)

    model.settings.weight_windows = [ww_n, ww_p]

    return model


@pytest.mark.parametrize("shared_secondary,subdir", [
    (False, "local"),
    (True, "shared"),
])
def test_weightwindows(shared_secondary, subdir):
    with change_directory(subdir):
        model = build_model(shared_secondary)
        test = HashedPyAPITestHarness('statepoint.2.h5', model)
        test.main()


def test_zero_bound_windows_play_no_game(tmp_path):
    # A weight window lower bound of zero means no weight window information
    # exists there (MCNP wwinp files use zero to turn the game off in a cell),
    # so transport must proceed as if weight windows were disabled. Previously,
    # zero-bound windows demanded a split at every checkpoint (weight/0 ->
    # max_split), multiplying the particle population until terminated by the
    # split or weight cutoff limits.
    model = build_model(False)
    for ww in model.settings.weight_windows:
        ww.lower_ww_bounds = np.zeros_like(ww.lower_ww_bounds)
        ww.upper_ww_bounds = np.zeros_like(ww.upper_ww_bounds)
    sp_zero = model.run(cwd=tmp_path / 'zero_windows')

    model.settings.weight_windows_on = False
    sp_off = model.run(cwd=tmp_path / 'windows_off')

    with openmc.StatePoint(sp_zero) as sp:
        flux_zero = list(sp.tallies.values())[0].mean
    with openmc.StatePoint(sp_off) as sp:
        flux_off = list(sp.tallies.values())[0].mean

    np.testing.assert_allclose(flux_zero, flux_off, rtol=1e-12)


def test_zero_and_negative_bounds_equivalent(tmp_path):
    # Zero and negative lower bounds both mean that no weight window
    # information exists in a cell (generators mark such cells with -1, and
    # MCNP wwinp files use zero), so they must produce identical transport.
    # Unlike the all-zero case above, here particles are born under valid
    # windows and encounter the no-information region in flight; previously a
    # zero lower bound in that situation demanded a split at every checkpoint
    # in the cell (weight/0 -> max_split), multiplying the particle population,
    # while -1 played no game.
    def run_with(bound_value, subdir):
        model = build_model(False)
        for ww in model.settings.weight_windows:
            lb = np.array(ww.lower_ww_bounds, copy=True)
            ub = np.array(ww.upper_ww_bounds, copy=True)
            lb[3:, :, :, :] = bound_value
            ub[3:, :, :, :] = bound_value
            ww.lower_ww_bounds = lb
            ww.upper_ww_bounds = ub
        return model.run(cwd=tmp_path / subdir)

    sp_zero = run_with(0.0, 'zero_region')
    sp_negative = run_with(-1.0, 'negative_region')

    with openmc.StatePoint(sp_zero) as sp:
        flux_zero = list(sp.tallies.values())[0].mean
    with openmc.StatePoint(sp_negative) as sp:
        flux_negative = list(sp.tallies.values())[0].mean

    np.testing.assert_allclose(flux_zero, flux_negative, rtol=1e-12)


def test_wwinp_cylindrical():

    ww = openmc.WeightWindowsList.from_wwinp('ww_n_cyl.txt')[0]

    mesh = ww.mesh

    assert mesh.dimension == (8, 8, 7)

    # make sure that the mesh grids are correct
    exp_r_grid = np.hstack((np.linspace(0.0, 3.02, 3, endpoint=False),
                            np.linspace(3.02, 6.0001, 6))).flatten()

    exp_phi_grid = np.hstack((np.linspace(0.0, 0.25, 2, endpoint=False),
                              np.linspace(0.25, 1.5707, 1, endpoint=False),
                              np.linspace(1.5707, 3.1415, 2, endpoint=False),
                              np.linspace(3.1415, 4.7124, 4))).flatten()

    exp_z_grid = np.hstack((np.linspace(0.0, 8.008, 4, endpoint=False),
                            np.linspace(8.008, 14.002, 4))).flatten()

    assert isinstance(mesh, openmc.CylindricalMesh)

    np.testing.assert_equal(mesh.r_grid, exp_r_grid)
    np.testing.assert_equal(mesh.phi_grid, exp_phi_grid)
    np.testing.assert_equal(mesh.z_grid, exp_z_grid)
    np.testing.assert_equal(mesh.origin, (0, 0, -9.0001))
    assert ww.lower_ww_bounds.flat[0] == 0.0
    assert ww.lower_ww_bounds.flat[-1] == np.prod(mesh.dimension) - 1


def test_wwinp_spherical():

    ww = openmc.WeightWindowsList.from_wwinp('ww_n_sph.txt')[0]

    mesh = ww.mesh

    assert mesh.dimension == (8, 7, 8)

    # make sure that the mesh grids are correct
    exp_r_grid = np.hstack((np.linspace(0.0, 3.02, 3, endpoint=False),
                            np.linspace(3.02, 6.0001, 6))).flatten()

    exp_theta_grid = np.hstack((np.linspace(0.0, 0.25, 2, endpoint=False),
                              np.linspace(0.25, 0.5, 1, endpoint=False),
                              np.linspace(0.5, 0.75, 2, endpoint=False),
                              np.linspace(0.75, 1.5707, 3))).flatten()

    exp_phi_grid = np.hstack((np.linspace(0.0, 0.25, 2, endpoint=False),
                              np.linspace(0.25, 0.5, 1, endpoint=False),
                              np.linspace(0.5, 1.5707, 2, endpoint=False),
                              np.linspace(1.5707, 3.1415, 4))).flatten()

    assert isinstance(mesh, openmc.SphericalMesh)

    np.testing.assert_equal(mesh.r_grid, exp_r_grid)
    np.testing.assert_equal(mesh.theta_grid, exp_theta_grid)
    np.testing.assert_equal(mesh.phi_grid, exp_phi_grid)
    np.testing.assert_equal(mesh.origin, (0, 0, -9.0001))
    assert ww.lower_ww_bounds.flat[0] == 0.0
    assert ww.lower_ww_bounds.flat[-1] == np.prod(mesh.dimension) - 1