"""Unit tests for :func:`esmf_regrid.experimental.unstructured_scheme.regrid_rectilinear_to_unstructured`."""

from iris.coords import AuxCoord, DimCoord
from iris.cube import Cube
import numpy as np
from numpy import ma
import pytest

from esmf_regrid.experimental.unstructured_scheme import (
    regrid_rectilinear_to_unstructured,
)
from esmf_regrid.tests.unit.schemes.test__cube_to_GridInfo import (
    _grid_cube,
)
from esmf_regrid.tests.unit.schemes.test__mesh_to_MeshInfo import (
    _gridlike_mesh_cube,
)
from esmf_regrid.tests.unit.schemes.test__regrid_unstructured_to_rectilinear__prepare import (
    _flat_mesh_cube,
)


def _add_metadata(cube):
    result = cube.copy()
    result.units = "K"
    result.attributes = {"a": 1}
    result.standard_name = "air_temperature"
    scalar_height = AuxCoord([5], units="m", standard_name="height")
    scalar_time = DimCoord([10], units="s", standard_name="time")
    result.add_aux_coord(scalar_height)
    result.add_aux_coord(scalar_time)
    return result


def test_flat_cubes():
    """
    Basic test for :func:`esmf_regrid.experimental.unstructured_scheme.regrid_rectilinear_to_unstructured`.

    Tests with flat cubes as input (a 2D grid cube and a 1D mesh cube).
    """
    tgt = _flat_mesh_cube()

    n_lons = 6
    n_lats = 5
    lon_bounds = (-180, 180)
    lat_bounds = (-90, 90)
    src = _grid_cube(n_lons, n_lats, lon_bounds, lat_bounds, circular=True)
    # Ensure data in the target grid is different to the expected data.
    # i.e. target grid data is all zero, expected data is all one
    tgt.data[:] = 0

    src = _add_metadata(src)
    src.data[:] = 1  # Ensure all data in the source is one.
    result = regrid_rectilinear_to_unstructured(src, tgt)
    src_T = src.copy()
    src_T.transpose()
    result_transposed = regrid_rectilinear_to_unstructured(src_T, tgt)

    expected_data = np.ones_like(tgt.data)
    expected_cube = _add_metadata(tgt)

    # Lenient check for data.
    assert np.allclose(expected_data, result.data)
    assert np.allclose(expected_data, result_transposed.data)

    # Check metadata and scalar coords.
    expected_cube.data = result.data
    assert expected_cube == result
    expected_cube.data = result_transposed.data
    assert expected_cube == result_transposed


@pytest.mark.parametrize("method", ("bilinear", "nearest"))
def test_node_friendly_methods(method):
    """
    Basic test for :func:`esmf_regrid.experimental.unstructured_scheme.regrid_rectilinear_to_unstructured`.

    Tests with the bilinear and nearest method.
    """
    n_lons = 6
    n_lats = 5
    lon_bounds = (-180, 180)
    lat_bounds = (-90, 90)
    tgt = _gridlike_mesh_cube(n_lons, n_lats, location="node")
    src = _grid_cube(n_lons, n_lats, lon_bounds, lat_bounds, circular=True)
    # Ensure data in the target grid is different to the expected data.
    # i.e. target grid data is all zero, expected data is all one
    tgt.data[:] = 0

    src = _add_metadata(src)
    src.data[:] = 1  # Ensure all data in the source is one.
    result = regrid_rectilinear_to_unstructured(src, tgt, method=method)

    expected_data = np.ones_like(tgt.data)
    expected_cube = _add_metadata(tgt)

    # Lenient check for data.
    assert np.allclose(expected_data, result.data)

    # Check metadata and scalar coords.
    expected_cube.data = result.data
    assert expected_cube == result


def test_invalid_args():
    """
    Test for :func:`esmf_regrid.experimental.unstructured_scheme.regrid_rectilinear_to_unstructured`.

    Tests that an appropriate error is raised when arguments are invalid.
    """
    n_lons = 6
    n_lats = 5
    lon_bounds = (-180, 180)
    lat_bounds = (-90, 90)
    node_tgt = _gridlike_mesh_cube(n_lons, n_lats, location="node")
    edge_tgt = _gridlike_mesh_cube(n_lons, n_lats, location="edge")
    face_tgt = _gridlike_mesh_cube(n_lons, n_lats, location="face")
    src = _grid_cube(n_lons, n_lats, lon_bounds, lat_bounds, circular=True)

    with pytest.raises(ValueError):
        _ = regrid_rectilinear_to_unstructured(src, src, method="bilinear")
    with pytest.raises(NotImplementedError):
        _ = regrid_rectilinear_to_unstructured(src, face_tgt, method="other")
    with pytest.raises(ValueError) as excinfo:
        _ = regrid_rectilinear_to_unstructured(src, node_tgt, method="conservative")
    expected_message = (
        "Conservative regridding requires a target cube located on "
        "the face of a cube, target cube had the node location."
    )
    assert expected_message in str(excinfo.value)
    with pytest.raises(ValueError) as excinfo:
        _ = regrid_rectilinear_to_unstructured(src, edge_tgt, method="bilinear")
    expected_message = (
        "bilinear regridding requires a target cube with a node "
        "or face location, target cube had the edge location."
    )
    assert expected_message in str(excinfo.value)
    with pytest.raises(ValueError) as excinfo:
        _ = regrid_rectilinear_to_unstructured(src, edge_tgt, method="nearest")
    expected_message = (
        "nearest regridding requires a target cube with a node "
        "or face location, target cube had the edge location."
    )
    assert expected_message in str(excinfo.value)


def test_multidim_cubes():
    """
    Test for :func:`esmf_regrid.experimental.unstructured_scheme.regrid_rectilinear_to_unstructured`.

    Tests with multidimensional cubes. The source cube contains
    coordinates on the dimensions before and after the grid dimensions.
    """
    tgt = _flat_mesh_cube()
    mesh = tgt.mesh
    mesh_length = mesh.connectivity(contains_face=True).shape[0]
    n_lons = 6
    n_lats = 5
    lon_bounds = (-180, 180)
    lat_bounds = (-90, 90)
    grid = _grid_cube(n_lons, n_lats, lon_bounds, lat_bounds, circular=True)

    h = 2
    p = 4
    t = 3
    height = DimCoord(np.arange(h), standard_name="height")
    pressure = DimCoord(np.arange(p), standard_name="air_pressure")
    time = DimCoord(np.arange(t), standard_name="time")
    spanning = AuxCoord(np.ones([t, p, h]), long_name="spanning dim")
    ignore = AuxCoord(np.ones([n_lats, h]), long_name="ignore")

    src_data = np.empty([t, n_lats, p, n_lons, h])
    src_data[:] = np.arange(t * p * h).reshape([t, p, h])[
        :, np.newaxis, :, np.newaxis, :
    ]
    cube = Cube(src_data)
    cube.add_dim_coord(grid.coord("latitude"), 1)
    cube.add_dim_coord(grid.coord("longitude"), 3)
    cube.add_dim_coord(time, 0)
    cube.add_dim_coord(pressure, 2)
    cube.add_dim_coord(height, 4)
    cube.add_aux_coord(spanning, [0, 2, 4])
    cube.add_aux_coord(ignore, [1, 4])

    result = regrid_rectilinear_to_unstructured(cube, tgt)

    cube_transposed = cube.copy()
    cube_transposed.transpose([0, 3, 2, 1, 4])
    result_transposed = regrid_rectilinear_to_unstructured(cube_transposed, tgt)

    # Lenient check for data.
    expected_data = np.empty([t, mesh_length, p, h])
    expected_data[:] = np.arange(t * p * h).reshape(t, p, h)[:, np.newaxis, :, :]
    assert np.allclose(expected_data, result.data)
    assert np.allclose(expected_data, result_transposed.data)

    mesh_coord_x, mesh_coord_y = mesh.to_MeshCoords("face")
    expected_cube = Cube(expected_data)
    expected_cube.add_dim_coord(time, 0)
    expected_cube.add_aux_coord(mesh_coord_x, 1)
    expected_cube.add_aux_coord(mesh_coord_y, 1)
    expected_cube.add_dim_coord(pressure, 2)
    expected_cube.add_dim_coord(height, 3)
    expected_cube.add_aux_coord(spanning, [0, 2, 3])

    # Check metadata and scalar coords.
    result.data = expected_data
    assert expected_cube == result
    result_transposed.data = expected_data
    assert expected_cube == result_transposed


def test_mask_handling():
    """
    Test masked data handling for :func:`esmf_regrid.experimental.unstructured_scheme.regrid_rectilinear_to_unstructured`.

    Tests masked data handling for multiple valid values for mdtol.
    """
    tgt = _flat_mesh_cube()

    n_lons = 6
    n_lats = 5
    lon_bounds = (-180, 180)
    lat_bounds = (-90, 90)
    src = _grid_cube(n_lons, n_lats, lon_bounds, lat_bounds, circular=True)

    data = np.ones([n_lats, n_lons])
    mask = np.zeros([n_lats, n_lons])
    mask[0, 0] = 1
    masked_data = ma.array(data, mask=mask)
    src.data = masked_data
    result_0 = regrid_rectilinear_to_unstructured(src, tgt, mdtol=0)
    result_05 = regrid_rectilinear_to_unstructured(src, tgt, mdtol=0.05)
    result_1 = regrid_rectilinear_to_unstructured(src, tgt, mdtol=1)

    expected_data = np.ones(tgt.shape)
    expected_0 = ma.array(expected_data)
    expected_05 = ma.array(expected_data, mask=[0, 0, 1, 0, 0, 0])
    expected_1 = ma.array(expected_data, mask=[1, 0, 1, 0, 0, 0])

    assert ma.allclose(expected_0, result_0.data)
    assert ma.allclose(expected_05, result_05.data)
    assert ma.allclose(expected_1, result_1.data)


def test_resolution():
    """
    Basic test for :func:`esmf_regrid.experimental.unstructured_scheme.regrid_rectilinear_to_unstructured`.

    Tests the src_resolution keyword with grids that would otherwise not work.
    """
    tgt = _flat_mesh_cube()

    # The resulting grid has full latitude bounds and cells must be split up.
    n_lons = 1
    n_lats = 4
    lon_bounds = (-180, 180)
    lat_bounds = (-90, 90)
    src = _grid_cube(n_lons, n_lats, lon_bounds, lat_bounds)
    # Ensure data in the target grid is different to the expected data.
    # i.e. target grid data is all zero, expected data is all one
    tgt.data[:] = 0

    src = _add_metadata(src)
    src.data[:] = 1  # Ensure all data in the source is one.
    result = regrid_rectilinear_to_unstructured(src, tgt, src_resolution=8)

    expected_data = np.ones_like(tgt.data)
    expected_cube = _add_metadata(tgt)

    # Lenient check for data.
    # Note that when src_resolution=None, this would be a fully masked array.
    assert np.allclose(expected_data, result.data)

    # Check metadata and scalar coords.
    expected_cube.data = result.data
    assert expected_cube == result
