import numpy as np
from numpy.testing import assert_almost_equal
import pytest

from statsmodels.datasets import get_rdataset
from statsmodels.datasets.tests.test_utils import IGNORED_EXCEPTIONS
import statsmodels.stats.dist_dependence_measures as ddm
from statsmodels.tools.sm_exceptions import HypothesisTestWarning


class TestDistDependenceMeasures:
    @classmethod
    def setup_class(cls):
        """
        Values were obtained via the R `energy` package.

        R code:
        ------
        > dcov.test(x, y, R=200)

            dCov independence test (permutation test)

        data:  index 1, replicates 200
        nV^2 = 45829, p-value = 0.004975
        sample estimates:
            dCov
        47.86925

        > DCOR(x, y)
        $dCov
        [1] 47.86925

        $dCor
        [1] 0.9999704

        $dVarX
        [1] 47.28702

        $dVarY
        [1] 48.46151
        """
        np.random.seed(3)

        cls.x = np.array(range(1, 101)).reshape((20, 5))
        cls.y = cls.x + np.log(cls.x)

        cls.dcor_exp = 0.9999704
        cls.dcov_exp = 47.86925
        cls.dvar_x_exp = 47.28702
        cls.dvar_y_exp = 48.46151
        cls.pval_emp_exp = 0.004975
        cls.test_stat_emp_exp = 45829

        # The values above are functions of the following values, and
        # therefore when the above group of variables is computed correctly
        # it means this group of variables was also correctly calculated.
        cls.S_exp = 5686.03162
        cls.test_stat_asym_exp = 2.8390102
        cls.pval_asym_exp = 0.00452

    def test_input_validation_nobs(self):
        with pytest.raises(ValueError, match="same number of observations"):
            ddm.distance_covariance_test(self.x[:2, :], self.y)

    def test_input_validation_unknown_method(self):
        with pytest.raises(ValueError, match="Unknown 'method' parameter"):
            ddm.distance_covariance_test(self.x, self.y, method="wrong_name")

    def test_statistic_value_asym_method(self):
        statistic, pval, method = ddm.distance_covariance_test(
            self.x, self.y, method="asym")

        assert method == "asym"
        assert_almost_equal(statistic, self.test_stat_asym_exp, 4)
        assert_almost_equal(pval, self.pval_asym_exp, 3)

    def test_statistic_value_emp_method(self):
        with pytest.warns(HypothesisTestWarning):
            statistic, pval, method = ddm.distance_covariance_test(
                self.x, self.y, method="emp"
            )

        assert method == "emp"

        assert_almost_equal(statistic, self.test_stat_emp_exp, 0)
        assert_almost_equal(pval, self.pval_emp_exp, 3)

    def test_fallback_to_asym_method(self):
        match_text = "The asymptotic approximation will be used"
        with pytest.warns(UserWarning, match=match_text):
            statistic, pval, _ = ddm.distance_covariance_test(
                self.x, self.y, method="emp", B=200
            )
        assert_almost_equal(statistic, self.test_stat_emp_exp, 0)
        assert_almost_equal(pval, self.pval_asym_exp, 3)

    def test_statistics_for_2d_input(self):
        stats = ddm.distance_statistics(
            np.asarray(self.x, dtype=float),
            np.asarray(self.y, dtype=float)
        )

        assert_almost_equal(stats.test_statistic, self.test_stat_emp_exp, 0)
        assert_almost_equal(stats.distance_correlation, self.dcor_exp, 4)
        assert_almost_equal(stats.distance_covariance, self.dcov_exp, 4)
        assert_almost_equal(stats.dvar_x, self.dvar_x_exp, 4)
        assert_almost_equal(stats.dvar_y, self.dvar_y_exp, 4)
        assert_almost_equal(stats.S, self.S_exp, 4)

    def test_statistics_for_1d_input(self):
        x = np.array(range(1, 21), dtype=float)
        y = x + np.log(x)

        stats = ddm.distance_statistics(x, y)

        # Values were obtained using the R `energy` package
        assert_almost_equal(stats.test_statistic, 398.94623, 5)
        assert_almost_equal(stats.distance_correlation, 0.9996107, 4)
        assert_almost_equal(stats.distance_covariance, 4.4662414, 4)
        assert_almost_equal(stats.dvar_x, 4.2294799, 4)
        assert_almost_equal(stats.dvar_y, 4.7199304, 4)
        assert_almost_equal(stats.S, 49.880200, 4)

    def test_results_on_the_iris_dataset(self):
        """
        R code example from the `energy` package documentation for
        `energy::distance_covariance.test`:

        > x <- iris[1:50, 1:4]
        > y <- iris[51:100, 1:4]
        > set.seed(1)
        > dcov.test(x, y, R=200)

            dCov independence test (permutation test)

        data:  index 1, replicates 200
        nV^2 = 0.5254, p-value = 0.9552
        sample estimates:
             dCov
        0.1025087
        """
        try:
            iris = get_rdataset("iris").data.values[:, :4]
        except IGNORED_EXCEPTIONS:
            pytest.skip("Failed with HTTPError or URLError, these are random")

        x = np.asarray(iris[:50], dtype=float)
        y = np.asarray(iris[50:100], dtype=float)

        stats = ddm.distance_statistics(x, y)

        assert_almost_equal(stats.test_statistic, 0.5254, 4)
        assert_almost_equal(stats.distance_correlation, 0.3060479, 4)
        assert_almost_equal(stats.distance_covariance, 0.1025087, 4)
        assert_almost_equal(stats.dvar_x, 0.2712927, 4)
        assert_almost_equal(stats.dvar_y, 0.4135274, 4)
        assert_almost_equal(stats.S, 0.667456, 4)

        test_statistic, _, method = ddm.distance_covariance_test(x, y, B=199)

        assert_almost_equal(test_statistic, 0.5254, 4)
        assert method == "emp"

    def test_results_on_the_quakes_dataset(self):
        """
        R code:
        ------

        > data("quakes")
        > x = quakes[1:50, 1:3]
        > y = quakes[51:100, 1:3]
        > dcov.test(x, y, R=200)

            dCov independence test (permutation test)

        data:  index 1, replicates 200
        nV^2 = 45046, p-value = 0.4577
        sample estimates:
            dCov
        30.01526
        """
        try:
            quakes = get_rdataset("quakes").data.values[:, :3]
        except IGNORED_EXCEPTIONS:
            pytest.skip("Failed with HTTPError or URLError, these are random")

        x = np.asarray(quakes[:50], dtype=float)
        y = np.asarray(quakes[50:100], dtype=float)

        stats = ddm.distance_statistics(x, y)

        assert_almost_equal(np.round(stats.test_statistic), 45046, 0)
        assert_almost_equal(stats.distance_correlation, 0.1894193, 4)
        assert_almost_equal(stats.distance_covariance, 30.01526, 4)
        assert_almost_equal(stats.dvar_x, 170.1702, 4)
        assert_almost_equal(stats.dvar_y, 147.5545, 4)
        assert_almost_equal(stats.S, 52265, 0)

        test_statistic, _, method = ddm.distance_covariance_test(x, y, B=199)

        assert_almost_equal(np.round(test_statistic), 45046, 0)
        assert method == "emp"

    def test_dcor(self):
        assert_almost_equal(ddm.distance_correlation(self.x, self.y),
                            self.dcor_exp, 4)

    def test_dcov(self):
        assert_almost_equal(ddm.distance_covariance(self.x, self.y),
                            self.dcov_exp, 4)

    def test_dvar(self):
        assert_almost_equal(ddm.distance_variance(self.x),
                            self.dvar_x_exp, 4)
