from datetime import datetime, timedelta

import numpy as np
import pytest

from pandas._libs.tslibs.ccalendar import DAYS, MONTHS
from pandas._libs.tslibs.period import INVALID_FREQ_ERR_MSG
from pandas.compat import is_platform_windows

from pandas import DatetimeIndex, Index, Series, Timestamp, date_range, period_range
import pandas._testing as tm
from pandas.core.tools.datetimes import to_datetime

import pandas.tseries.frequencies as frequencies
import pandas.tseries.offsets as offsets


def _check_generated_range(start, periods, freq):
    """
    Check the range generated from a given start, frequency, and period count.

    Parameters
    ----------
    start : str
        The start date.
    periods : int
        The number of periods.
    freq : str
        The frequency of the range.
    """
    freq = freq.upper()

    gen = date_range(start, periods=periods, freq=freq)
    index = DatetimeIndex(gen.values)

    if not freq.startswith("Q-"):
        assert frequencies.infer_freq(index) == gen.freqstr
    else:
        inf_freq = frequencies.infer_freq(index)
        is_dec_range = inf_freq == "Q-DEC" and gen.freqstr in (
            "Q",
            "Q-DEC",
            "Q-SEP",
            "Q-JUN",
            "Q-MAR",
        )
        is_nov_range = inf_freq == "Q-NOV" and gen.freqstr in (
            "Q-NOV",
            "Q-AUG",
            "Q-MAY",
            "Q-FEB",
        )
        is_oct_range = inf_freq == "Q-OCT" and gen.freqstr in (
            "Q-OCT",
            "Q-JUL",
            "Q-APR",
            "Q-JAN",
        )
        assert is_dec_range or is_nov_range or is_oct_range


@pytest.fixture(
    params=[
        (timedelta(1), "D"),
        (timedelta(hours=1), "H"),
        (timedelta(minutes=1), "T"),
        (timedelta(seconds=1), "S"),
        (np.timedelta64(1, "ns"), "N"),
        (timedelta(microseconds=1), "U"),
        (timedelta(microseconds=1000), "L"),
    ]
)
def base_delta_code_pair(request):
    return request.param


@pytest.fixture(params=[1, 2, 3, 4])
def count(request):
    return request.param


@pytest.fixture(params=DAYS)
def day(request):
    return request.param


@pytest.fixture(params=MONTHS)
def month(request):
    return request.param


@pytest.fixture(params=[5, 7])
def periods(request):
    return request.param


def test_raise_if_period_index():
    index = period_range(start="1/1/1990", periods=20, freq="M")
    msg = "Check the `freq` attribute instead of using infer_freq"

    with pytest.raises(TypeError, match=msg):
        frequencies.infer_freq(index)


def test_raise_if_too_few():
    index = DatetimeIndex(["12/31/1998", "1/3/1999"])
    msg = "Need at least 3 dates to infer frequency"

    with pytest.raises(ValueError, match=msg):
        frequencies.infer_freq(index)


def test_business_daily():
    index = DatetimeIndex(["01/01/1999", "1/4/1999", "1/5/1999"])
    assert frequencies.infer_freq(index) == "B"


def test_business_daily_look_alike():
    # see gh-16624
    #
    # Do not infer "B when "weekend" (2-day gap) in wrong place.
    index = DatetimeIndex(["12/31/1998", "1/3/1999", "1/4/1999"])
    assert frequencies.infer_freq(index) is None


def test_day_corner():
    index = DatetimeIndex(["1/1/2000", "1/2/2000", "1/3/2000"])
    assert frequencies.infer_freq(index) == "D"


def test_non_datetime_index():
    dates = to_datetime(["1/1/2000", "1/2/2000", "1/3/2000"])
    assert frequencies.infer_freq(dates) == "D"


def test_fifth_week_of_month_infer():
    # see gh-9425
    #
    # Only attempt to infer up to WOM-4.
    index = DatetimeIndex(["2014-03-31", "2014-06-30", "2015-03-30"])
    assert frequencies.infer_freq(index) is None


def test_week_of_month_fake():
    # All of these dates are on same day
    # of week and are 4 or 5 weeks apart.
    index = DatetimeIndex(["2013-08-27", "2013-10-01", "2013-10-29", "2013-11-26"])
    assert frequencies.infer_freq(index) != "WOM-4TUE"


def test_fifth_week_of_month():
    # see gh-9425
    #
    # Only supports freq up to WOM-4.
    msg = (
        "Of the four parameters: start, end, periods, "
        "and freq, exactly three must be specified"
    )

    with pytest.raises(ValueError, match=msg):
        date_range("2014-01-01", freq="WOM-5MON")


def test_monthly_ambiguous():
    rng = DatetimeIndex(["1/31/2000", "2/29/2000", "3/31/2000"])
    assert rng.inferred_freq == "M"


def test_annual_ambiguous():
    rng = DatetimeIndex(["1/31/2000", "1/31/2001", "1/31/2002"])
    assert rng.inferred_freq == "A-JAN"


def test_infer_freq_delta(base_delta_code_pair, count):
    b = Timestamp(datetime.now())
    base_delta, code = base_delta_code_pair

    inc = base_delta * count
    index = DatetimeIndex([b + inc * j for j in range(3)])

    exp_freq = f"{count:d}{code}" if count > 1 else code
    assert frequencies.infer_freq(index) == exp_freq


@pytest.mark.parametrize(
    "constructor",
    [
        lambda now, delta: DatetimeIndex(
            [now + delta * 7] + [now + delta * j for j in range(3)]
        ),
        lambda now, delta: DatetimeIndex(
            [now + delta * j for j in range(3)] + [now + delta * 7]
        ),
    ],
)
def test_infer_freq_custom(base_delta_code_pair, constructor):
    b = Timestamp(datetime.now())
    base_delta, _ = base_delta_code_pair

    index = constructor(b, base_delta)
    assert frequencies.infer_freq(index) is None


def test_weekly_infer(periods, day):
    _check_generated_range("1/1/2000", periods, f"W-{day}")


def test_week_of_month_infer(periods, day, count):
    _check_generated_range("1/1/2000", periods, f"WOM-{count}{day}")


@pytest.mark.parametrize("freq", ["M", "BM", "BMS"])
def test_monthly_infer(periods, freq):
    _check_generated_range("1/1/2000", periods, "M")


def test_quarterly_infer(month, periods):
    _check_generated_range("1/1/2000", periods, f"Q-{month}")


@pytest.mark.parametrize("annual", ["A", "BA"])
def test_annually_infer(month, periods, annual):
    _check_generated_range("1/1/2000", periods, f"{annual}-{month}")


@pytest.mark.parametrize(
    "freq,expected", [("Q", "Q-DEC"), ("Q-NOV", "Q-NOV"), ("Q-OCT", "Q-OCT")]
)
def test_infer_freq_index(freq, expected):
    rng = period_range("1959Q2", "2009Q3", freq=freq)
    rng = Index(rng.to_timestamp("D", how="e").astype(object))

    assert rng.inferred_freq == expected


@pytest.mark.parametrize(
    "expected,dates",
    list(
        {
            "AS-JAN": ["2009-01-01", "2010-01-01", "2011-01-01", "2012-01-01"],
            "Q-OCT": ["2009-01-31", "2009-04-30", "2009-07-31", "2009-10-31"],
            "M": ["2010-11-30", "2010-12-31", "2011-01-31", "2011-02-28"],
            "W-SAT": ["2010-12-25", "2011-01-01", "2011-01-08", "2011-01-15"],
            "D": ["2011-01-01", "2011-01-02", "2011-01-03", "2011-01-04"],
            "H": [
                "2011-12-31 22:00",
                "2011-12-31 23:00",
                "2012-01-01 00:00",
                "2012-01-01 01:00",
            ],
        }.items()
    ),
)
def test_infer_freq_tz(tz_naive_fixture, expected, dates):
    # see gh-7310
    tz = tz_naive_fixture
    idx = DatetimeIndex(dates, tz=tz)
    assert idx.inferred_freq == expected


@pytest.mark.parametrize(
    "date_pair",
    [
        ["2013-11-02", "2013-11-5"],  # Fall DST
        ["2014-03-08", "2014-03-11"],  # Spring DST
        ["2014-01-01", "2014-01-03"],  # Regular Time
    ],
)
@pytest.mark.parametrize(
    "freq", ["3H", "10T", "3601S", "3600001L", "3600000001U", "3600000000001N"]
)
def test_infer_freq_tz_transition(tz_naive_fixture, date_pair, freq):
    # see gh-8772
    tz = tz_naive_fixture
    idx = date_range(date_pair[0], date_pair[1], freq=freq, tz=tz)
    assert idx.inferred_freq == freq


def test_infer_freq_tz_transition_custom():
    index = date_range("2013-11-03", periods=5, freq="3H").tz_localize(
        "America/Chicago"
    )
    assert index.inferred_freq is None


@pytest.mark.parametrize(
    "data,expected",
    [
        # Hourly freq in a day must result in "H"
        (
            [
                "2014-07-01 09:00",
                "2014-07-01 10:00",
                "2014-07-01 11:00",
                "2014-07-01 12:00",
                "2014-07-01 13:00",
                "2014-07-01 14:00",
            ],
            "H",
        ),
        (
            [
                "2014-07-01 09:00",
                "2014-07-01 10:00",
                "2014-07-01 11:00",
                "2014-07-01 12:00",
                "2014-07-01 13:00",
                "2014-07-01 14:00",
                "2014-07-01 15:00",
                "2014-07-01 16:00",
                "2014-07-02 09:00",
                "2014-07-02 10:00",
                "2014-07-02 11:00",
            ],
            "BH",
        ),
        (
            [
                "2014-07-04 09:00",
                "2014-07-04 10:00",
                "2014-07-04 11:00",
                "2014-07-04 12:00",
                "2014-07-04 13:00",
                "2014-07-04 14:00",
                "2014-07-04 15:00",
                "2014-07-04 16:00",
                "2014-07-07 09:00",
                "2014-07-07 10:00",
                "2014-07-07 11:00",
            ],
            "BH",
        ),
        (
            [
                "2014-07-04 09:00",
                "2014-07-04 10:00",
                "2014-07-04 11:00",
                "2014-07-04 12:00",
                "2014-07-04 13:00",
                "2014-07-04 14:00",
                "2014-07-04 15:00",
                "2014-07-04 16:00",
                "2014-07-07 09:00",
                "2014-07-07 10:00",
                "2014-07-07 11:00",
                "2014-07-07 12:00",
                "2014-07-07 13:00",
                "2014-07-07 14:00",
                "2014-07-07 15:00",
                "2014-07-07 16:00",
                "2014-07-08 09:00",
                "2014-07-08 10:00",
                "2014-07-08 11:00",
                "2014-07-08 12:00",
                "2014-07-08 13:00",
                "2014-07-08 14:00",
                "2014-07-08 15:00",
                "2014-07-08 16:00",
            ],
            "BH",
        ),
    ],
)
def test_infer_freq_business_hour(data, expected):
    # see gh-7905
    idx = DatetimeIndex(data)
    assert idx.inferred_freq == expected


def test_not_monotonic():
    rng = DatetimeIndex(["1/31/2000", "1/31/2001", "1/31/2002"])
    rng = rng[::-1]

    assert rng.inferred_freq == "-1A-JAN"


def test_non_datetime_index2():
    rng = DatetimeIndex(["1/31/2000", "1/31/2001", "1/31/2002"])
    vals = rng.to_pydatetime()

    result = frequencies.infer_freq(vals)
    assert result == rng.inferred_freq


@pytest.mark.parametrize(
    "idx", [tm.makeIntIndex(10), tm.makeFloatIndex(10), tm.makePeriodIndex(10)]
)
def test_invalid_index_types(idx):
    msg = (
        "(cannot infer freq from a non-convertible)|"
        "(Check the `freq` attribute instead of using infer_freq)"
    )

    with pytest.raises(TypeError, match=msg):
        frequencies.infer_freq(idx)


@pytest.mark.skipif(is_platform_windows(), reason="see gh-10822: Windows issue")
@pytest.mark.parametrize("idx", [tm.makeStringIndex(10), tm.makeUnicodeIndex(10)])
def test_invalid_index_types_unicode(idx):
    # see gh-10822
    #
    # Odd error message on conversions to datetime for unicode.
    msg = "Unknown string format"

    with pytest.raises(ValueError, match=msg):
        frequencies.infer_freq(idx)


def test_string_datetime_like_compat():
    # see gh-6463
    data = ["2004-01", "2004-02", "2004-03", "2004-04"]

    expected = frequencies.infer_freq(data)
    result = frequencies.infer_freq(Index(data))

    assert result == expected


def test_series():
    # see gh-6407
    s = Series(date_range("20130101", "20130110"))
    inferred = frequencies.infer_freq(s)
    assert inferred == "D"


@pytest.mark.parametrize("end", [10, 10.0])
def test_series_invalid_type(end):
    # see gh-6407
    msg = "cannot infer freq from a non-convertible dtype on a Series"
    s = Series(np.arange(end))

    with pytest.raises(TypeError, match=msg):
        frequencies.infer_freq(s)


def test_series_inconvertible_string():
    # see gh-6407
    msg = "Unknown string format"

    with pytest.raises(ValueError, match=msg):
        frequencies.infer_freq(Series(["foo", "bar"]))


@pytest.mark.parametrize("freq", [None, "L"])
def test_series_period_index(freq):
    # see gh-6407
    #
    # Cannot infer on PeriodIndex
    msg = "cannot infer freq from a non-convertible dtype on a Series"
    s = Series(period_range("2013", periods=10, freq=freq))

    with pytest.raises(TypeError, match=msg):
        frequencies.infer_freq(s)


@pytest.mark.parametrize("freq", ["M", "L", "S"])
def test_series_datetime_index(freq):
    s = Series(date_range("20130101", periods=10, freq=freq))
    inferred = frequencies.infer_freq(s)
    assert inferred == freq


@pytest.mark.parametrize(
    "offset_func",
    [
        frequencies._get_offset,
        lambda freq: date_range("2011-01-01", periods=5, freq=freq),
    ],
)
@pytest.mark.parametrize(
    "freq",
    [
        "WEEKDAY",
        "EOM",
        "W@MON",
        "W@TUE",
        "W@WED",
        "W@THU",
        "W@FRI",
        "W@SAT",
        "W@SUN",
        "Q@JAN",
        "Q@FEB",
        "Q@MAR",
        "A@JAN",
        "A@FEB",
        "A@MAR",
        "A@APR",
        "A@MAY",
        "A@JUN",
        "A@JUL",
        "A@AUG",
        "A@SEP",
        "A@OCT",
        "A@NOV",
        "A@DEC",
        "Y@JAN",
        "WOM@1MON",
        "WOM@2MON",
        "WOM@3MON",
        "WOM@4MON",
        "WOM@1TUE",
        "WOM@2TUE",
        "WOM@3TUE",
        "WOM@4TUE",
        "WOM@1WED",
        "WOM@2WED",
        "WOM@3WED",
        "WOM@4WED",
        "WOM@1THU",
        "WOM@2THU",
        "WOM@3THU",
        "WOM@4THU",
        "WOM@1FRI",
        "WOM@2FRI",
        "WOM@3FRI",
        "WOM@4FRI",
    ],
)
def test_legacy_offset_warnings(offset_func, freq):
    with pytest.raises(ValueError, match=INVALID_FREQ_ERR_MSG):
        offset_func(freq)


def test_ms_vs_capital_ms():
    left = frequencies._get_offset("ms")
    right = frequencies._get_offset("MS")

    assert left == offsets.Milli()
    assert right == offsets.MonthBegin()