import numpy as np
import pytest
from hypothesis import assume, given
from hypothesis.strategies import builds, integers

import lttb


def load_test_data():
    csv = "tests/timeseries.csv"
    data = np.genfromtxt(csv, delimiter=",", names=True)
    xs = data["X"]
    ys = data["Y"]
    return np.array([xs, ys]).T


@given(integers(min_value=3, max_value=5000))
def test_downsampled_test_data_is_correct_shape(n_out):
    data = load_test_data()
    out = lttb.downsample(data, n_out)
    assert out.shape == (n_out, 2)


@given(integers(min_value=3, max_value=5000))
def test_downsampling_test_data_retains_variation(n_out):
    data = load_test_data()
    out = lttb.downsample(data, n_out)
    assert np.var(out[:, 1]) >= 29.5  # var(data) == 30.9968


def gen_valid_data(nrows):
    ys = np.random.standard_normal(nrows) * 1000
    xs = np.linspace(1, nrows, nrows)
    return np.array([xs, ys]).T


@given(
    builds(gen_valid_data, integers(min_value=3, max_value=5000)),
    integers(min_value=3, max_value=5000),
)
def test_downsampled_random_data_is_correct_shape(data, n_out):
    assume(n_out <= len(data))
    out = lttb.downsample(data, n_out)
    assert out.shape == (n_out, 2)


@given(
    builds(gen_valid_data, integers(min_value=3, max_value=5000)),
    integers(min_value=3, max_value=5000),
)
def test_downsampling_random_data_retains_variation(data, n_out):
    assume(n_out <= len(data))
    out = lttb.downsample(data, n_out)
    var_in = np.var(data[:, 1])
    var_out = np.var(out[:, 1])
    assert var_out >= 0.95 * var_in


@pytest.mark.parametrize("n_out", [2, 7])
def test_invalid_n_out_raises_error(n_out):
    data = gen_valid_data(6)

    with pytest.raises(ValueError):
        lttb.downsample(data, n_out)


def test_downsample_with_default_validators_raises_error_with_multiple_messages():
    data = np.random.standard_normal((4, 3))  # 3 columns
    data[:, 0] = [1, 2, 2, 3]  # unsorted x values
    data[2, 1] = np.nan  # missing y value

    with pytest.raises(ValueError) as exc:
        lttb.downsample(data, 3)

    assert exc.match(
        "data does not have 2 columns; "
        "data contains NaN values; "
        "first column is not strictly increasing"
    )