from datetime import datetime, timedelta

import numpy as np
import pytest

from pandas import Timedelta, Timestamp
import pandas.util.testing as tm

from pandas.tseries import offsets
from pandas.tseries.frequencies import to_offset


class TestTimestampArithmetic:
    def test_overflow_offset(self):
        # no overflow expected

        stamp = Timestamp("2000/1/1")
        offset_no_overflow = to_offset("D") * 100

        expected = Timestamp("2000/04/10")
        assert stamp + offset_no_overflow == expected

        assert offset_no_overflow + stamp == expected

        expected = Timestamp("1999/09/23")
        assert stamp - offset_no_overflow == expected

    def test_overflow_offset_raises(self):
        # xref https://github.com/statsmodels/statsmodels/issues/3374
        # ends up multiplying really large numbers which overflow

        stamp = Timestamp("2017-01-13 00:00:00", freq="D")
        offset_overflow = 20169940 * offsets.Day(1)
        msg = (
            "the add operation between "
            r"\<-?\d+ \* Days\> and \d{4}-\d{2}-\d{2} \d{2}:\d{2}:\d{2} "
            "will overflow"
        )

        with pytest.raises(OverflowError, match=msg):
            stamp + offset_overflow

        with pytest.raises(OverflowError, match=msg):
            offset_overflow + stamp

        with pytest.raises(OverflowError, match=msg):
            stamp - offset_overflow

        # xref https://github.com/pandas-dev/pandas/issues/14080
        # used to crash, so check for proper overflow exception

        stamp = Timestamp("2000/1/1")
        offset_overflow = to_offset("D") * 100 ** 25

        with pytest.raises(OverflowError, match=msg):
            stamp + offset_overflow

        with pytest.raises(OverflowError, match=msg):
            offset_overflow + stamp

        with pytest.raises(OverflowError, match=msg):
            stamp - offset_overflow

    def test_delta_preserve_nanos(self):
        val = Timestamp(1337299200000000123)
        result = val + timedelta(1)
        assert result.nanosecond == val.nanosecond

    def test_timestamp_sub_datetime(self):
        dt = datetime(2013, 10, 12)
        ts = Timestamp(datetime(2013, 10, 13))
        assert (ts - dt).days == 1
        assert (dt - ts).days == -1

    def test_addition_subtraction_types(self):
        # Assert on the types resulting from Timestamp +/- various date/time
        # objects
        dt = datetime(2014, 3, 4)
        td = timedelta(seconds=1)
        # build a timestamp with a frequency, since then it supports
        # addition/subtraction of integers
        ts = Timestamp(dt, freq="D")

        with tm.assert_produces_warning(FutureWarning):
            # GH#22535 add/sub with integers is deprecated
            assert type(ts + 1) == Timestamp
            assert type(ts - 1) == Timestamp

        # Timestamp + datetime not supported, though subtraction is supported
        # and yields timedelta more tests in tseries/base/tests/test_base.py
        assert type(ts - dt) == Timedelta
        assert type(ts + td) == Timestamp
        assert type(ts - td) == Timestamp

        # Timestamp +/- datetime64 not supported, so not tested (could possibly
        # assert error raised?)
        td64 = np.timedelta64(1, "D")
        assert type(ts + td64) == Timestamp
        assert type(ts - td64) == Timestamp

    @pytest.mark.parametrize(
        "freq, td, td64",
        [
            ("S", timedelta(seconds=1), np.timedelta64(1, "s")),
            ("min", timedelta(minutes=1), np.timedelta64(1, "m")),
            ("H", timedelta(hours=1), np.timedelta64(1, "h")),
            ("D", timedelta(days=1), np.timedelta64(1, "D")),
            ("W", timedelta(weeks=1), np.timedelta64(1, "W")),
            ("M", None, np.timedelta64(1, "M")),
        ],
    )
    def test_addition_subtraction_preserve_frequency(self, freq, td, td64):
        ts = Timestamp("2014-03-05 00:00:00", freq=freq)
        original_freq = ts.freq

        with tm.assert_produces_warning(FutureWarning):
            # GH#22535 add/sub with integers is deprecated
            assert (ts + 1).freq == original_freq
            assert (ts - 1).freq == original_freq

        assert (ts + 1 * original_freq).freq == original_freq
        assert (ts - 1 * original_freq).freq == original_freq

        if td is not None:
            # timedelta does not support months as unit
            assert (ts + td).freq == original_freq
            assert (ts - td).freq == original_freq

        assert (ts + td64).freq == original_freq
        assert (ts - td64).freq == original_freq

    @pytest.mark.parametrize(
        "td", [Timedelta(hours=3), np.timedelta64(3, "h"), timedelta(hours=3)]
    )
    def test_radd_tdscalar(self, td):
        # GH#24775 timedelta64+Timestamp should not raise
        ts = Timestamp.now()
        assert td + ts == ts + td

    @pytest.mark.parametrize(
        "other,expected_difference",
        [
            (np.timedelta64(-123, "ns"), -123),
            (np.timedelta64(1234567898, "ns"), 1234567898),
            (np.timedelta64(-123, "us"), -123000),
            (np.timedelta64(-123, "ms"), -123000000),
        ],
    )
    def test_timestamp_add_timedelta64_unit(self, other, expected_difference):
        ts = Timestamp(datetime.utcnow())
        result = ts + other
        valdiff = result.value - ts.value
        assert valdiff == expected_difference
