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

from sklearn.manifold import _mds as mds


def test_smacof():
    # test metric smacof using the data of "Modern Multidimensional Scaling",
    # Borg & Groenen, p 154
    sim = np.array([[0, 5, 3, 4], [5, 0, 2, 2], [3, 2, 0, 1], [4, 2, 1, 0]])
    Z = np.array([[-0.266, -0.539], [0.451, 0.252], [0.016, -0.238], [-0.200, 0.524]])
    X, _ = mds.smacof(sim, init=Z, n_components=2, max_iter=1, n_init=1)
    X_true = np.array(
        [[-1.415, -2.471], [1.633, 1.107], [0.249, -0.067], [-0.468, 1.431]]
    )
    assert_array_almost_equal(X, X_true, decimal=3)


def test_smacof_error():
    # Not symmetric similarity matrix:
    sim = np.array([[0, 5, 9, 4], [5, 0, 2, 2], [3, 2, 0, 1], [4, 2, 1, 0]])

    with pytest.raises(ValueError):
        mds.smacof(sim)

    # Not squared similarity matrix:
    sim = np.array([[0, 5, 9, 4], [5, 0, 2, 2], [4, 2, 1, 0]])

    with pytest.raises(ValueError):
        mds.smacof(sim)

    # init not None and not correct format:
    sim = np.array([[0, 5, 3, 4], [5, 0, 2, 2], [3, 2, 0, 1], [4, 2, 1, 0]])

    Z = np.array([[-0.266, -0.539], [0.016, -0.238], [-0.200, 0.524]])
    with pytest.raises(ValueError):
        mds.smacof(sim, init=Z, n_init=1)


def test_MDS():
    sim = np.array([[0, 5, 3, 4], [5, 0, 2, 2], [3, 2, 0, 1], [4, 2, 1, 0]])
    mds_clf = mds.MDS(metric=False, n_jobs=3, dissimilarity="precomputed")
    mds_clf.fit(sim)