import numpy as np
import pytest

import pandas as pd
from pandas import Timedelta
import pandas._testing as tm
from pandas.core import nanops
from pandas.core.arrays import TimedeltaArray


class TestReductions:
    @pytest.mark.parametrize("name", ["std", "min", "max", "median", "mean"])
    @pytest.mark.parametrize("skipna", [True, False])
    def test_reductions_empty(self, name, skipna):
        tdi = pd.TimedeltaIndex([])
        arr = tdi.array

        result = getattr(tdi, name)(skipna=skipna)
        assert result is pd.NaT

        result = getattr(arr, name)(skipna=skipna)
        assert result is pd.NaT

    @pytest.mark.parametrize("skipna", [True, False])
    def test_sum_empty(self, skipna):
        tdi = pd.TimedeltaIndex([])
        arr = tdi.array

        result = tdi.sum(skipna=skipna)
        assert isinstance(result, Timedelta)
        assert result == Timedelta(0)

        result = arr.sum(skipna=skipna)
        assert isinstance(result, Timedelta)
        assert result == Timedelta(0)

    def test_min_max(self, unit):
        dtype = f"m8[{unit}]"
        arr = TimedeltaArray._from_sequence(
            ["3h", "3h", "NaT", "2h", "5h", "4h"], dtype=dtype
        )

        result = arr.min()
        expected = Timedelta("2h")
        assert result == expected

        result = arr.max()
        expected = Timedelta("5h")
        assert result == expected

        result = arr.min(skipna=False)
        assert result is pd.NaT

        result = arr.max(skipna=False)
        assert result is pd.NaT

    def test_sum(self):
        tdi = pd.TimedeltaIndex(["3h", "3h", "NaT", "2h", "5h", "4h"])
        arr = tdi.array

        result = arr.sum(skipna=True)
        expected = Timedelta(hours=17)
        assert isinstance(result, Timedelta)
        assert result == expected

        result = tdi.sum(skipna=True)
        assert isinstance(result, Timedelta)
        assert result == expected

        result = arr.sum(skipna=False)
        assert result is pd.NaT

        result = tdi.sum(skipna=False)
        assert result is pd.NaT

        result = arr.sum(min_count=9)
        assert result is pd.NaT

        result = tdi.sum(min_count=9)
        assert result is pd.NaT

        result = arr.sum(min_count=1)
        assert isinstance(result, Timedelta)
        assert result == expected

        result = tdi.sum(min_count=1)
        assert isinstance(result, Timedelta)
        assert result == expected

    def test_npsum(self):
        # GH#25282, GH#25335 np.sum should return a Timedelta, not timedelta64
        tdi = pd.TimedeltaIndex(["3h", "3h", "2h", "5h", "4h"])
        arr = tdi.array

        result = np.sum(tdi)
        expected = Timedelta(hours=17)
        assert isinstance(result, Timedelta)
        assert result == expected

        result = np.sum(arr)
        assert isinstance(result, Timedelta)
        assert result == expected

    def test_sum_2d_skipna_false(self):
        arr = np.arange(8).astype(np.int64).view("m8[s]").astype("m8[ns]").reshape(4, 2)
        arr[-1, -1] = "Nat"

        tda = TimedeltaArray._from_sequence(arr)

        result = tda.sum(skipna=False)
        assert result is pd.NaT

        result = tda.sum(axis=0, skipna=False)
        expected = pd.TimedeltaIndex([Timedelta(seconds=12), pd.NaT])._values
        tm.assert_timedelta_array_equal(result, expected)

        result = tda.sum(axis=1, skipna=False)
        expected = pd.TimedeltaIndex(
            [
                Timedelta(seconds=1),
                Timedelta(seconds=5),
                Timedelta(seconds=9),
                pd.NaT,
            ]
        )._values
        tm.assert_timedelta_array_equal(result, expected)

    # Adding a Timestamp makes this a test for DatetimeArray.std
    @pytest.mark.parametrize(
        "add",
        [
            Timedelta(0),
            pd.Timestamp("2021-01-01"),
            pd.Timestamp("2021-01-01", tz="UTC"),
            pd.Timestamp("2021-01-01", tz="Asia/Tokyo"),
        ],
    )
    def test_std(self, add):
        tdi = pd.TimedeltaIndex(["0h", "4h", "NaT", "4h", "0h", "2h"]) + add
        arr = tdi.array

        result = arr.std(skipna=True)
        expected = Timedelta(hours=2)
        assert isinstance(result, Timedelta)
        assert result == expected

        result = tdi.std(skipna=True)
        assert isinstance(result, Timedelta)
        assert result == expected

        if getattr(arr, "tz", None) is None:
            result = nanops.nanstd(np.asarray(arr), skipna=True)
            assert isinstance(result, np.timedelta64)
            assert result == expected

        result = arr.std(skipna=False)
        assert result is pd.NaT

        result = tdi.std(skipna=False)
        assert result is pd.NaT

        if getattr(arr, "tz", None) is None:
            result = nanops.nanstd(np.asarray(arr), skipna=False)
            assert isinstance(result, np.timedelta64)
            assert np.isnat(result)

    def test_median(self):
        tdi = pd.TimedeltaIndex(["0h", "3h", "NaT", "5h06m", "0h", "2h"])
        arr = tdi.array

        result = arr.median(skipna=True)
        expected = Timedelta(hours=2)
        assert isinstance(result, Timedelta)
        assert result == expected

        result = tdi.median(skipna=True)
        assert isinstance(result, Timedelta)
        assert result == expected

        result = arr.median(skipna=False)
        assert result is pd.NaT

        result = tdi.median(skipna=False)
        assert result is pd.NaT

    def test_mean(self):
        tdi = pd.TimedeltaIndex(["0h", "3h", "NaT", "5h06m", "0h", "2h"])
        arr = tdi._data

        # manually verified result
        expected = Timedelta(arr.dropna()._ndarray.mean())

        result = arr.mean()
        assert result == expected
        result = arr.mean(skipna=False)
        assert result is pd.NaT

        result = arr.dropna().mean(skipna=False)
        assert result == expected

        result = arr.mean(axis=0)
        assert result == expected

    def test_mean_2d(self):
        tdi = pd.timedelta_range("14 days", periods=6)
        tda = tdi._data.reshape(3, 2)

        result = tda.mean(axis=0)
        expected = tda[1]
        tm.assert_timedelta_array_equal(result, expected)

        result = tda.mean(axis=1)
        expected = tda[:, 0] + Timedelta(hours=12)
        tm.assert_timedelta_array_equal(result, expected)

        result = tda.mean(axis=None)
        expected = tdi.mean()
        assert result == expected