import pytest
import warnings
import numpy as np
from numpy.testing import assert_array_equal, assert_allclose
from copy import deepcopy
from scipy.stats.sampling import FastGeneratorInversion
from scipy import stats
from scipy._lib._testutils import IS_MUSL


def test_bad_args():
    # loc and scale must be scalar
    with pytest.raises(ValueError, match="loc must be scalar"):
        FastGeneratorInversion(stats.norm(loc=(1.2, 1.3)))
    with pytest.raises(ValueError, match="scale must be scalar"):
        FastGeneratorInversion(stats.norm(scale=[1.5, 5.7]))

    with pytest.raises(ValueError, match="'test' cannot be used to seed"):
        FastGeneratorInversion(stats.norm(), random_state="test")

    msg = "Each of the 1 shape parameters must be a scalar"
    with pytest.raises(ValueError, match=msg):
        FastGeneratorInversion(stats.gamma([1.3, 2.5]))

    with pytest.raises(ValueError, match="`dist` must be a frozen"):
        FastGeneratorInversion("xy")

    with pytest.raises(ValueError, match="Distribution 'truncnorm' is not"):
        FastGeneratorInversion(stats.truncnorm(1.3, 4.5))


def test_random_state():
    # fixed seed
    gen = FastGeneratorInversion(stats.norm(), random_state=68734509)
    x1 = gen.rvs(size=10)
    gen.random_state = 68734509
    x2 = gen.rvs(size=10)
    assert_array_equal(x1, x2)

    # Generator
    urng = np.random.default_rng(20375857)
    gen = FastGeneratorInversion(stats.norm(), random_state=urng)
    x1 = gen.rvs(size=10)
    gen.random_state = np.random.default_rng(20375857)
    x2 = gen.rvs(size=10)
    assert_array_equal(x1, x2)

    # RandomState
    urng = np.random.RandomState(2364)
    gen = FastGeneratorInversion(stats.norm(), random_state=urng)
    x1 = gen.rvs(size=10)
    gen.random_state = np.random.RandomState(2364)
    x2 = gen.rvs(size=10)
    assert_array_equal(x1, x2)

    # if evaluate_error is called, it must not interfere with the random_state
    # used by rvs
    gen = FastGeneratorInversion(stats.norm(), random_state=68734509)
    x1 = gen.rvs(size=10)
    _ = gen.evaluate_error(size=5)  # this will generate 5 uniform rvs
    x2 = gen.rvs(size=10)
    gen.random_state = 68734509
    x3 = gen.rvs(size=20)
    assert_array_equal(x2, x3[10:])


dists_with_params = [
    ("alpha", (3.5,)),
    ("anglit", ()),
    ("argus", (3.5,)),
    ("argus", (5.1,)),
    ("beta", (1.5, 0.9)),
    ("cosine", ()),
    ("betaprime", (2.5, 3.3)),
    ("bradford", (1.2,)),
    ("burr", (1.3, 2.4)),
    ("burr12", (0.7, 1.2)),
    ("cauchy", ()),
    ("chi2", (3.5,)),
    ("chi", (4.5,)),
    ("crystalball", (0.7, 1.2)),
    ("expon", ()),
    ("gamma", (1.5,)),
    ("gennorm", (2.7,)),
    ("gumbel_l", ()),
    ("gumbel_r", ()),
    ("hypsecant", ()),
    ("invgauss", (3.1,)),
    ("invweibull", (1.5,)),
    ("laplace", ()),
    ("logistic", ()),
    ("maxwell", ()),
    ("moyal", ()),
    ("norm", ()),
    ("pareto", (1.3,)),
    ("powerlaw", (7.6,)),
    ("rayleigh", ()),
    ("semicircular", ()),
    ("t", (5.7,)),
    ("wald", ()),
    ("weibull_max", (2.4,)),
    ("weibull_min", (1.2,)),
]


@pytest.mark.parametrize(("distname, args"), dists_with_params)
def test_rvs_and_ppf(distname, args):
    # check sample against rvs generated by rv_continuous
    urng = np.random.default_rng(9807324628097097)
    rng1 = getattr(stats, distname)(*args)
    rvs1 = rng1.rvs(size=500, random_state=urng)
    rng2 = FastGeneratorInversion(rng1, random_state=urng)
    rvs2 = rng2.rvs(size=500)
    assert stats.cramervonmises_2samp(rvs1, rvs2).pvalue > 0.01

    # check ppf
    q = [0.001, 0.1, 0.5, 0.9, 0.999]
    assert_allclose(rng1.ppf(q), rng2.ppf(q), atol=1e-10)


@pytest.mark.parametrize(("distname, args"), dists_with_params)
def test_u_error(distname, args):
    # check sample against rvs generated by rv_continuous
    dist = getattr(stats, distname)(*args)
    with warnings.catch_warnings():
        # filter the warnings thrown by UNU.RAN
        warnings.simplefilter("ignore", RuntimeWarning)
        rng = FastGeneratorInversion(dist)
    u_error, x_error = rng.evaluate_error(
        size=10_000, random_state=9807324628097097, x_error=False
    )
    assert u_error <= 1e-10


@pytest.mark.xslow
@pytest.mark.xfail(reason="geninvgauss CDF is not accurate")
def test_geninvgauss_uerror():
    dist = stats.geninvgauss(3.2, 1.5)
    rng = FastGeneratorInversion(dist)
    err = rng.evaluate_error(size=10_000, random_state=67982)
    assert err[0] < 1e-10


# TODO: add more distributions
@pytest.mark.skipif(IS_MUSL, reason="Hits RecursionError, see gh-23172")
@pytest.mark.fail_slow(5)
@pytest.mark.parametrize(("distname, args"), [("beta", (0.11, 0.11))])
def test_error_extreme_params(distname, args):
    # take extreme parameters where u-error might not be below the tolerance
    # due to limitations of floating point arithmetic
    with warnings.catch_warnings():
        # filter the warnings thrown by UNU.RAN for such extreme parameters
        warnings.simplefilter("ignore", RuntimeWarning)
        dist = getattr(stats, distname)(*args)
        rng = FastGeneratorInversion(dist)
    u_error, x_error = rng.evaluate_error(
        size=10_000, random_state=980732462809709732623, x_error=True
    )
    if u_error >= 2.5 * 1e-10:
        assert x_error < 1e-9


def test_evaluate_error_inputs():
    gen = FastGeneratorInversion(stats.norm())
    with pytest.raises(ValueError, match="size must be an integer"):
        gen.evaluate_error(size=3.5)
    with pytest.raises(ValueError, match="size must be an integer"):
        gen.evaluate_error(size=(3, 3))


def test_rvs_ppf_loc_scale():
    loc, scale = 3.5, 2.3
    dist = stats.norm(loc=loc, scale=scale)
    rng = FastGeneratorInversion(dist, random_state=1234)
    r = rng.rvs(size=1000)
    r_rescaled = (r - loc) / scale
    assert stats.cramervonmises(r_rescaled, "norm").pvalue > 0.01
    q = [0.001, 0.1, 0.5, 0.9, 0.999]
    assert_allclose(rng._ppf(q), rng.ppf(q), atol=1e-10)


def test_domain():
    # only a basic check that the domain argument is passed to the
    # UNU.RAN generators
    rng = FastGeneratorInversion(stats.norm(), domain=(-1, 1))
    r = rng.rvs(size=100)
    assert -1 <= r.min() < r.max() <= 1

    # if loc and scale are used, new domain is loc + scale*domain
    loc, scale = 3.5, 1.3
    dist = stats.norm(loc=loc, scale=scale)
    rng = FastGeneratorInversion(dist, domain=(-1.5, 2))
    r = rng.rvs(size=100)
    lb, ub = loc - scale * 1.5, loc + scale * 2
    assert lb <= r.min() < r.max() <= ub


@pytest.mark.parametrize(("distname, args, expected"),
                         [("beta", (3.5, 2.5), (0, 1)),
                          ("norm", (), (-np.inf, np.inf))])
def test_support(distname, args, expected):
    # test that the support is updated if truncation and loc/scale are applied
    # use beta distribution since it is a transformed betaprime distribution,
    # so it is important that the correct support is considered
    # (i.e., the support of beta is (0,1), while betaprime is (0, inf))
    dist = getattr(stats, distname)(*args)
    rng = FastGeneratorInversion(dist)
    assert_array_equal(rng.support(), expected)
    rng.loc = 1
    rng.scale = 2
    assert_array_equal(rng.support(), 1 + 2*np.array(expected))


@pytest.mark.parametrize(("distname, args"),
                         [("beta", (3.5, 2.5)), ("norm", ())])
def test_support_truncation(distname, args):
    # similar test for truncation
    dist = getattr(stats, distname)(*args)
    rng = FastGeneratorInversion(dist, domain=(0.5, 0.7))
    assert_array_equal(rng.support(), (0.5, 0.7))
    rng.loc = 1
    rng.scale = 2
    assert_array_equal(rng.support(), (1 + 2 * 0.5, 1 + 2 * 0.7))


def test_domain_shift_truncation():
    # center of norm is zero, it should be shifted to the left endpoint of
    # domain. if this was not the case, PINV in UNURAN would raise a warning
    # as the center is not inside the domain
    with warnings.catch_warnings():
        warnings.simplefilter("error")
        rng = FastGeneratorInversion(stats.norm(), domain=(1, 2))
    r = rng.rvs(size=100)
    assert 1 <= r.min() < r.max() <= 2


def test_non_rvs_methods_with_domain():
    # as a first step, compare truncated normal against stats.truncnorm
    rng = FastGeneratorInversion(stats.norm(), domain=(2.3, 3.2))
    trunc_norm = stats.truncnorm(2.3, 3.2)
    # take values that are inside and outside the domain
    x = (2.0, 2.4, 3.0, 3.4)
    p = (0.01, 0.5, 0.99)
    assert_allclose(rng._cdf(x), trunc_norm.cdf(x))
    assert_allclose(rng._ppf(p), trunc_norm.ppf(p))
    loc, scale = 2, 3
    rng.loc = 2
    rng.scale = 3
    trunc_norm = stats.truncnorm(2.3, 3.2, loc=loc, scale=scale)
    x = np.array(x) * scale + loc
    assert_allclose(rng._cdf(x), trunc_norm.cdf(x))
    assert_allclose(rng._ppf(p), trunc_norm.ppf(p))

    # do another sanity check with beta distribution
    # in that case, it is important to use the correct domain since beta
    # is a transformation of betaprime which has a different support
    rng = FastGeneratorInversion(stats.beta(2.5, 3.5), domain=(0.3, 0.7))
    rng.loc = 2
    rng.scale = 2.5
    # the support is 2.75, , 3.75 (2 + 2.5 * 0.3, 2 + 2.5 * 0.7)
    assert_array_equal(rng.support(), (2.75, 3.75))
    x = np.array([2.74, 2.76, 3.74, 3.76])
    # the cdf needs to be zero outside of the domain
    y_cdf = rng._cdf(x)
    assert_array_equal((y_cdf[0], y_cdf[3]), (0, 1))
    assert np.min(y_cdf[1:3]) > 0
    # ppf needs to map 0 and 1 to the boundaries
    assert_allclose(rng._ppf(y_cdf), (2.75, 2.76, 3.74, 3.75))


def test_non_rvs_methods_without_domain():
    norm_dist = stats.norm()
    rng = FastGeneratorInversion(norm_dist)
    x = np.linspace(-3, 3, num=10)
    p = (0.01, 0.5, 0.99)
    assert_allclose(rng._cdf(x), norm_dist.cdf(x))
    assert_allclose(rng._ppf(p), norm_dist.ppf(p))
    loc, scale = 0.5, 1.3
    rng.loc = loc
    rng.scale = scale
    norm_dist = stats.norm(loc=loc, scale=scale)
    assert_allclose(rng._cdf(x), norm_dist.cdf(x))
    assert_allclose(rng._ppf(p), norm_dist.ppf(p))

@pytest.mark.parametrize(("domain, x"),
                         [(None, 0.5),
                         ((0, 1), 0.5),
                         ((0, 1), 1.5)])
def test_scalar_inputs(domain, x):
    """ pdf, cdf etc should map scalar values to scalars. check with and
    w/o domain since domain impacts pdf, cdf etc
    Take x inside and outside of domain """
    rng = FastGeneratorInversion(stats.norm(), domain=domain)
    assert np.isscalar(rng._cdf(x))
    assert np.isscalar(rng._ppf(0.5))


def test_domain_argus_large_chi():
    # for large chi, the Gamma distribution is used and the domain has to be
    # transformed. this is a test to ensure that the transformation works
    chi, lb, ub = 5.5, 0.25, 0.75
    rng = FastGeneratorInversion(stats.argus(chi), domain=(lb, ub))
    rng.random_state = 4574
    r = rng.rvs(size=500)
    assert lb <= r.min() < r.max() <= ub
    # perform goodness of fit test with conditional cdf
    cdf = stats.argus(chi).cdf
    prob = cdf(ub) - cdf(lb)
    assert stats.cramervonmises(r, lambda x: cdf(x) / prob).pvalue > 0.05


def test_setting_loc_scale():
    rng = FastGeneratorInversion(stats.norm(), random_state=765765864)
    r1 = rng.rvs(size=1000)
    rng.loc = 3.0
    rng.scale = 2.5
    r2 = rng.rvs(1000)
    # rescaled r2 should be again standard normal
    assert stats.cramervonmises_2samp(r1, (r2 - 3) / 2.5).pvalue > 0.05
    # reset values to default loc=0, scale=1
    rng.loc = 0
    rng.scale = 1
    r2 = rng.rvs(1000)
    assert stats.cramervonmises_2samp(r1, r2).pvalue > 0.05


def test_ignore_shape_range():
    msg = "No generator is defined for the shape parameters"
    with pytest.raises(ValueError, match=msg):
        rng = FastGeneratorInversion(stats.t(0.03))
    rng = FastGeneratorInversion(stats.t(0.03), ignore_shape_range=True)
    # we can ignore the recommended range of shape parameters
    # but u-error can be expected to be too large in that case
    u_err, _ = rng.evaluate_error(size=1000, random_state=234)
    assert u_err >= 1e-6

@pytest.mark.xfail_on_32bit(
    "NumericalInversePolynomial.qrvs fails for Win 32-bit"
)
class TestQRVS:
    def test_input_validation(self):
        gen = FastGeneratorInversion(stats.norm())

        match = "`qmc_engine` must be an instance of..."
        with pytest.raises(ValueError, match=match):
            gen.qrvs(qmc_engine=0)

        match = "`d` must be consistent with dimension of `qmc_engine`."
        with pytest.raises(ValueError, match=match):
            gen.qrvs(d=3, qmc_engine=stats.qmc.Halton(2))

    qrngs = [None, stats.qmc.Sobol(1, seed=0), stats.qmc.Halton(3, seed=0)]
    # `size=None` should not add anything to the shape, `size=1` should
    sizes = [
        (None, tuple()),
        (1, (1,)),
        (4, (4,)),
        ((4,), (4,)),
        ((2, 4), (2, 4)),
    ]
    # Neither `d=None` nor `d=1` should add anything to the shape
    ds = [(None, tuple()), (1, tuple()), (3, (3,))]

    @pytest.mark.parametrize("qrng", qrngs)
    @pytest.mark.parametrize("size_in, size_out", sizes)
    @pytest.mark.parametrize("d_in, d_out", ds)
    def test_QRVS_shape_consistency(self, qrng, size_in, size_out,
                                    d_in, d_out):
        gen = FastGeneratorInversion(stats.norm())

        # If d and qrng.d are inconsistent, an error is raised
        if d_in is not None and qrng is not None and qrng.d != d_in:
            match = "`d` must be consistent with dimension of `qmc_engine`."
            with pytest.raises(ValueError, match=match):
                gen.qrvs(size_in, d=d_in, qmc_engine=qrng)
            return

        # Sometimes d is really determined by qrng
        if d_in is None and qrng is not None and qrng.d != 1:
            d_out = (qrng.d,)

        shape_expected = size_out + d_out

        qrng2 = deepcopy(qrng)
        qrvs = gen.qrvs(size=size_in, d=d_in, qmc_engine=qrng)
        if size_in is not None:
            assert qrvs.shape == shape_expected

        if qrng2 is not None:
            uniform = qrng2.random(np.prod(size_in) or 1)
            qrvs2 = stats.norm.ppf(uniform).reshape(shape_expected)
            assert_allclose(qrvs, qrvs2, atol=1e-12)

    def test_QRVS_size_tuple(self):
        # QMCEngine samples are always of shape (n, d). When `size` is a tuple,
        # we set `n = prod(size)` in the call to qmc_engine.random, transform
        # the sample, and reshape it to the final dimensions. When we reshape,
        # we need to be careful, because the _columns_ of the sample returned
        # by a QMCEngine are "independent"-ish, but the elements within the
        # columns are not. We need to make sure that this doesn't get mixed up
        # by reshaping: qrvs[..., i] should remain "independent"-ish of
        # qrvs[..., i+1], but the elements within qrvs[..., i] should be
        # transformed from the same low-discrepancy sequence.

        gen = FastGeneratorInversion(stats.norm())

        size = (3, 4)
        d = 5
        qrng = stats.qmc.Halton(d, seed=0)
        qrng2 = stats.qmc.Halton(d, seed=0)

        uniform = qrng2.random(np.prod(size))

        qrvs = gen.qrvs(size=size, d=d, qmc_engine=qrng)
        qrvs2 = stats.norm.ppf(uniform)

        for i in range(d):
            sample = qrvs[..., i]
            sample2 = qrvs2[:, i].reshape(size)
            assert_allclose(sample, sample2, atol=1e-12)


def test_burr_overflow():
    # this case leads to an overflow error if math.exp is used
    # in the definition of the burr pdf instead of np.exp
    # a direct implementation of the PDF as x**(-c-1) / (1+x**(-c))**(d+1)
    # also leads to an overflow error in the setup
    args = (1.89128135, 0.30195177)
    with warnings.catch_warnings():
        # filter potential overflow warning
        warnings.simplefilter("ignore", RuntimeWarning)
        gen = FastGeneratorInversion(stats.burr(*args))
    u_error, _ = gen.evaluate_error(random_state=4326)
    assert u_error <= 1e-10
