import pytest
import sympy as sp
import numpy as np
import pystencils as ps
from pystencils.fast_approximation import fast_division


@pytest.mark.parametrize('dtype', ["float64", "float32"])
@pytest.mark.parametrize('func', [sp.Pow, sp.atan2])
@pytest.mark.parametrize('target', [ps.Target.CPU, ps.Target.GPU])
def test_two_arguments(dtype, func, target):
    if target == ps.Target.GPU:
        pytest.importorskip("cupy")
    dh = ps.create_data_handling(domain_size=(10, 10), periodicity=True, default_target=target)

    x = dh.add_array('x', values_per_cell=1, dtype=dtype)
    dh.fill("x", 0.0, ghost_layers=True)
    y = dh.add_array('y', values_per_cell=1, dtype=dtype)
    dh.fill("y", 1.0, ghost_layers=True)
    z = dh.add_array('z', values_per_cell=1, dtype=dtype)
    dh.fill("z", 2.0, ghost_layers=True)

    config = ps.CreateKernelConfig(target=target)

    # test sp.Max with one argument
    up = ps.Assignment(x.center, func(y.center, z.center))
    ast = ps.create_kernel(up, config=config)
    code = ps.get_code_str(ast)
    if dtype == 'float32':
        assert func.__name__.lower() in code
    kernel = ast.compile()

    dh.all_to_gpu()
    dh.run_kernel(kernel)
    dh.all_to_cpu()

    np.testing.assert_allclose(dh.gather_array("x")[0, 0], float(func(1.0, 2.0).evalf()),
                               13 if dtype == 'float64' else 5)


@pytest.mark.parametrize('dtype', ["float64", "float32"])
@pytest.mark.parametrize('func', [sp.sin, sp.cos, sp.sinh, sp.cosh, sp.atan, sp.floor, sp.ceiling])
@pytest.mark.parametrize('target', [ps.Target.CPU, ps.Target.GPU])
def test_single_arguments(dtype, func, target):
    if target == ps.Target.GPU:
        pytest.importorskip("cupy")
    dh = ps.create_data_handling(domain_size=(10, 10), periodicity=True, default_target=target)

    x = dh.add_array('x', values_per_cell=1, dtype=dtype)
    dh.fill("x", 0.0, ghost_layers=True)
    y = dh.add_array('y', values_per_cell=1, dtype=dtype)
    dh.fill("y", 1.0, ghost_layers=True)

    config = ps.CreateKernelConfig(target=target)

    # test sp.Max with one argument
    up = ps.Assignment(x.center, func(y.center))
    ast = ps.create_kernel(up, config=config)
    code = ps.get_code_str(ast)
    if dtype == 'float32':
        func_name = func.__name__.lower() if func is not sp.ceiling else "ceil"
        assert func_name in code
    kernel = ast.compile()

    dh.all_to_gpu()
    dh.run_kernel(kernel)
    dh.all_to_cpu()

    np.testing.assert_allclose(dh.gather_array("x")[0, 0], float(func(1.0).evalf()),
                               rtol=10**-3 if dtype == 'float32' else 10**-5)


@pytest.mark.parametrize('a', [sp.Symbol('a'), ps.fields('a:  float64[2d]').center])
def test_avoid_pow(a):
    x = ps.fields('x:  float64[2d]')

    up = ps.Assignment(x.center_vector[0], 2 * a ** 2 / 3)
    ast = ps.create_kernel(up)

    code = ps.get_code_str(ast)

    assert "pow" not in code


def test_avoid_pow_fast_div():
    x = ps.fields('x:  float64[2d]')
    a = ps.fields('a:  float64[2d]').center

    up = ps.Assignment(x.center_vector[0], fast_division(1, (a**2)))
    ast = ps.create_kernel(up, config=ps.CreateKernelConfig(target=ps.Target.GPU))
    # ps.show_code(ast)

    code = ps.get_code_str(ast)

    assert "pow" not in code


def test_avoid_pow_move_constants():
    # At the end of the kernel creation the function move_constants_before_loop will be called
    # This function additionally contains substitutions for symbols with the same value
    # Thus it simplifies the equations again
    x = ps.fields('x:  float64[2d]')
    a, b, c = sp.symbols("a, b, c")

    up = [ps.Assignment(a, 0.0),
          ps.Assignment(b, 0.0),
          ps.Assignment(c, 0.0),
          ps.Assignment(x.center_vector[0], a**2/18 - a*b/6 - a/18 + b**2/18 + b/18 - c**2/36)]
    ast = ps.create_kernel(up)

    code = ps.get_code_str(ast)
    ps.show_code(ast)

    assert "pow" not in code