import numpy as np

import pandas as pd
import pandas._testing as tm


def test_isocalendar_returns_correct_values_close_to_new_year_with_tz():
    # GH#6538: Check that DatetimeIndex and its TimeStamp elements
    # return the same weekofyear accessor close to new year w/ tz
    dates = ["2013/12/29", "2013/12/30", "2013/12/31"]
    dates = pd.DatetimeIndex(dates, tz="Europe/Brussels")
    result = dates.isocalendar()
    expected_data_frame = pd.DataFrame(
        [[2013, 52, 7], [2014, 1, 1], [2014, 1, 2]],
        columns=["year", "week", "day"],
        index=dates,
    ).astype({"year": "Int32", "week": "UInt32", "day": "UInt32"})
    tm.assert_frame_equal(result, expected_data_frame)


def test_dti_timestamp_isocalendar_fields():
    idx = pd.date_range("2020-01-01", periods=10)
    expected = tuple(idx.isocalendar().iloc[-1].to_list())
    result = idx[-1].isocalendar()
    assert result == expected


def test_isocalendar_year_before_year_one():
    # GH#66549 the year column was unsigned, so BC years wrapped, e.g. year -100
    #  came out as 4294967196
    dti = pd.DatetimeIndex(np.array(["-0100-03-05", "0001-01-01"], dtype="M8[s]"))
    result = dti.isocalendar()
    expected = pd.DataFrame(
        [[-100, 10, 1], [1, 1, 1]],
        columns=["year", "week", "day"],
        index=dti,
    ).astype({"year": "Int32", "week": "UInt32", "day": "UInt32"})
    tm.assert_frame_equal(result, expected)