import builtins
from io import StringIO

import numpy as np
import pytest

from pandas.errors import UnsupportedFunctionCall

import pandas as pd
from pandas import (
    DataFrame,
    Index,
    MultiIndex,
    Series,
    Timestamp,
    date_range,
)
import pandas._testing as tm
import pandas.core.nanops as nanops
from pandas.util import _test_decorators as td


@pytest.fixture(
    params=[np.int32, np.int64, np.float32, np.float64, "Int64", "Float64"],
    ids=["np.int32", "np.int64", "np.float32", "np.float64", "Int64", "Float64"],
)
def dtypes_for_minmax(request):
    """
    Fixture of dtypes with min and max values used for testing
    cummin and cummax
    """
    dtype = request.param

    np_type = dtype
    if dtype == "Int64":
        np_type = np.int64
    elif dtype == "Float64":
        np_type = np.float64

    min_val = (
        np.iinfo(np_type).min
        if np.dtype(np_type).kind == "i"
        else np.finfo(np_type).min
    )
    max_val = (
        np.iinfo(np_type).max
        if np.dtype(np_type).kind == "i"
        else np.finfo(np_type).max
    )

    return (dtype, min_val, max_val)


def test_intercept_builtin_sum():
    s = Series([1.0, 2.0, np.nan, 3.0])
    grouped = s.groupby([0, 1, 2, 2])

    result = grouped.agg(builtins.sum)
    result2 = grouped.apply(builtins.sum)
    expected = grouped.sum()
    tm.assert_series_equal(result, expected)
    tm.assert_series_equal(result2, expected)


@pytest.mark.parametrize("f", [max, min, sum])
@pytest.mark.parametrize("keys", ["jim", ["jim", "joe"]])  # Single key  # Multi-key
def test_builtins_apply(keys, f):
    # see gh-8155
    df = DataFrame(np.random.randint(1, 50, (1000, 2)), columns=["jim", "joe"])
    df["jolie"] = np.random.randn(1000)

    gb = df.groupby(keys)

    fname = f.__name__
    result = gb.apply(f)
    ngroups = len(df.drop_duplicates(subset=keys))

    assert_msg = f"invalid frame shape: {result.shape} (expected ({ngroups}, 3))"
    assert result.shape == (ngroups, 3), assert_msg

    npfunc = getattr(np, fname)  # numpy's equivalent function
    if f in [max, min]:
        warn = FutureWarning
    else:
        warn = None
    msg = "scalar (max|min) over the entire DataFrame"
    with tm.assert_produces_warning(warn, match=msg, check_stacklevel=False):
        # stacklevel can be thrown off because (i think) the stack
        #  goes through some of numpy's C code.
        expected = gb.apply(npfunc)
    tm.assert_frame_equal(result, expected)

    with tm.assert_produces_warning(None):
        expected2 = gb.apply(lambda x: npfunc(x, axis=0))
    tm.assert_frame_equal(result, expected2)

    if f != sum:
        expected = gb.agg(fname).reset_index()
        expected.set_index(keys, inplace=True, drop=False)
        tm.assert_frame_equal(result, expected, check_dtype=False)

    tm.assert_series_equal(getattr(result, fname)(), getattr(df, fname)())


class TestNumericOnly:
    # make sure that we are passing thru kwargs to our agg functions

    @pytest.fixture
    def df(self):
        # GH3668
        # GH5724
        df = DataFrame(
            {
                "group": [1, 1, 2],
                "int": [1, 2, 3],
                "float": [4.0, 5.0, 6.0],
                "string": list("abc"),
                "category_string": Series(list("abc")).astype("category"),
                "category_int": [7, 8, 9],
                "datetime": date_range("20130101", periods=3),
                "datetimetz": date_range("20130101", periods=3, tz="US/Eastern"),
                "timedelta": pd.timedelta_range("1 s", periods=3, freq="s"),
            },
            columns=[
                "group",
                "int",
                "float",
                "string",
                "category_string",
                "category_int",
                "datetime",
                "datetimetz",
                "timedelta",
            ],
        )
        return df

    @pytest.mark.parametrize("method", ["mean", "median"])
    def test_averages(self, df, method):
        # mean / median
        expected_columns_numeric = Index(["int", "float", "category_int"])

        gb = df.groupby("group")
        expected = DataFrame(
            {
                "category_int": [7.5, 9],
                "float": [4.5, 6.0],
                "timedelta": [pd.Timedelta("1.5s"), pd.Timedelta("3s")],
                "int": [1.5, 3],
                "datetime": [
                    Timestamp("2013-01-01 12:00:00"),
                    Timestamp("2013-01-03 00:00:00"),
                ],
                "datetimetz": [
                    Timestamp("2013-01-01 12:00:00", tz="US/Eastern"),
                    Timestamp("2013-01-03 00:00:00", tz="US/Eastern"),
                ],
            },
            index=Index([1, 2], name="group"),
            columns=[
                "int",
                "float",
                "category_int",
                "datetime",
                "datetimetz",
                "timedelta",
            ],
        )

        with tm.assert_produces_warning(FutureWarning, match="Dropping invalid"):
            result = getattr(gb, method)(numeric_only=False)
        tm.assert_frame_equal(result.reindex_like(expected), expected)

        expected_columns = expected.columns

        self._check(df, method, expected_columns, expected_columns_numeric)

    @pytest.mark.parametrize("method", ["min", "max"])
    def test_extrema(self, df, method):
        # TODO: min, max *should* handle
        # categorical (ordered) dtype

        expected_columns = Index(
            [
                "int",
                "float",
                "string",
                "category_int",
                "datetime",
                "datetimetz",
                "timedelta",
            ]
        )
        expected_columns_numeric = expected_columns

        self._check(df, method, expected_columns, expected_columns_numeric)

    @pytest.mark.parametrize("method", ["first", "last"])
    def test_first_last(self, df, method):

        expected_columns = Index(
            [
                "int",
                "float",
                "string",
                "category_string",
                "category_int",
                "datetime",
                "datetimetz",
                "timedelta",
            ]
        )
        expected_columns_numeric = expected_columns

        self._check(df, method, expected_columns, expected_columns_numeric)

    @pytest.mark.parametrize("method", ["sum", "cumsum"])
    def test_sum_cumsum(self, df, method):

        expected_columns_numeric = Index(["int", "float", "category_int"])
        expected_columns = Index(
            ["int", "float", "string", "category_int", "timedelta"]
        )
        if method == "cumsum":
            # cumsum loses string
            expected_columns = Index(["int", "float", "category_int", "timedelta"])

        self._check(df, method, expected_columns, expected_columns_numeric)

    @pytest.mark.parametrize("method", ["prod", "cumprod"])
    def test_prod_cumprod(self, df, method):

        expected_columns = Index(["int", "float", "category_int"])
        expected_columns_numeric = expected_columns

        self._check(df, method, expected_columns, expected_columns_numeric)

    @pytest.mark.parametrize("method", ["cummin", "cummax"])
    def test_cummin_cummax(self, df, method):
        # like min, max, but don't include strings
        expected_columns = Index(
            ["int", "float", "category_int", "datetime", "datetimetz", "timedelta"]
        )

        # GH#15561: numeric_only=False set by default like min/max
        expected_columns_numeric = expected_columns

        self._check(df, method, expected_columns, expected_columns_numeric)

    def _check(self, df, method, expected_columns, expected_columns_numeric):
        gb = df.groupby("group")

        # cummin, cummax dont have numeric_only kwarg, always use False
        warn = None
        if method in ["cummin", "cummax"]:
            # these dont have numeric_only kwarg, always use False
            warn = FutureWarning
        elif method in ["min", "max"]:
            # these have numeric_only kwarg, but default to False
            warn = FutureWarning

        with tm.assert_produces_warning(warn, match="Dropping invalid columns"):
            result = getattr(gb, method)()

        tm.assert_index_equal(result.columns, expected_columns_numeric)

        # GH#41475 deprecated silently ignoring nuisance columns
        warn = None
        if len(expected_columns) < len(gb._obj_with_exclusions.columns):
            warn = FutureWarning
        with tm.assert_produces_warning(warn, match="Dropping invalid columns"):
            result = getattr(gb, method)(numeric_only=False)

        tm.assert_index_equal(result.columns, expected_columns)


class TestGroupByNonCythonPaths:
    # GH#5610 non-cython calls should not include the grouper
    # Tests for code not expected to go through cython paths.

    @pytest.fixture
    def df(self):
        df = DataFrame(
            [[1, 2, "foo"], [1, np.nan, "bar"], [3, np.nan, "baz"]],
            columns=["A", "B", "C"],
        )
        return df

    @pytest.fixture
    def gb(self, df):
        gb = df.groupby("A")
        return gb

    @pytest.fixture
    def gni(self, df):
        gni = df.groupby("A", as_index=False)
        return gni

    # TODO: non-unique columns, as_index=False
    @pytest.mark.filterwarnings("ignore:.*Select only valid:FutureWarning")
    def test_idxmax(self, gb):
        # object dtype so idxmax goes through _aggregate_item_by_item
        # GH#5610
        # non-cython calls should not include the grouper
        expected = DataFrame([[0.0], [np.nan]], columns=["B"], index=[1, 3])
        expected.index.name = "A"
        result = gb.idxmax()
        tm.assert_frame_equal(result, expected)

    @pytest.mark.filterwarnings("ignore:.*Select only valid:FutureWarning")
    def test_idxmin(self, gb):
        # object dtype so idxmax goes through _aggregate_item_by_item
        # GH#5610
        # non-cython calls should not include the grouper
        expected = DataFrame([[0.0], [np.nan]], columns=["B"], index=[1, 3])
        expected.index.name = "A"
        result = gb.idxmin()
        tm.assert_frame_equal(result, expected)

    def test_mad(self, gb, gni):
        # mad
        expected = DataFrame([[0], [np.nan]], columns=["B"], index=[1, 3])
        expected.index.name = "A"
        result = gb.mad()
        tm.assert_frame_equal(result, expected)

        expected = DataFrame([[1, 0.0], [3, np.nan]], columns=["A", "B"], index=[0, 1])
        result = gni.mad()
        tm.assert_frame_equal(result, expected)

    def test_describe(self, df, gb, gni):
        # describe
        expected_index = Index([1, 3], name="A")
        expected_col = MultiIndex(
            levels=[["B"], ["count", "mean", "std", "min", "25%", "50%", "75%", "max"]],
            codes=[[0] * 8, list(range(8))],
        )
        expected = DataFrame(
            [
                [1.0, 2.0, np.nan, 2.0, 2.0, 2.0, 2.0, 2.0],
                [0.0, np.nan, np.nan, np.nan, np.nan, np.nan, np.nan, np.nan],
            ],
            index=expected_index,
            columns=expected_col,
        )
        result = gb.describe()
        tm.assert_frame_equal(result, expected)

        expected = pd.concat(
            [
                df[df.A == 1].describe().unstack().to_frame().T,
                df[df.A == 3].describe().unstack().to_frame().T,
            ]
        )
        expected.index = Index([0, 1])
        result = gni.describe()
        tm.assert_frame_equal(result, expected)


def test_cython_api2():

    # this takes the fast apply path

    # cumsum (GH5614)
    df = DataFrame([[1, 2, np.nan], [1, np.nan, 9], [3, 4, 9]], columns=["A", "B", "C"])
    expected = DataFrame([[2, np.nan], [np.nan, 9], [4, 9]], columns=["B", "C"])
    result = df.groupby("A").cumsum()
    tm.assert_frame_equal(result, expected)

    # GH 5755 - cumsum is a transformer and should ignore as_index
    result = df.groupby("A", as_index=False).cumsum()
    tm.assert_frame_equal(result, expected)

    # GH 13994
    result = df.groupby("A").cumsum(axis=1)
    expected = df.cumsum(axis=1)
    tm.assert_frame_equal(result, expected)
    result = df.groupby("A").cumprod(axis=1)
    expected = df.cumprod(axis=1)
    tm.assert_frame_equal(result, expected)


def test_cython_median():
    df = DataFrame(np.random.randn(1000))
    df.values[::2] = np.nan

    labels = np.random.randint(0, 50, size=1000).astype(float)
    labels[::17] = np.nan

    result = df.groupby(labels).median()
    exp = df.groupby(labels).agg(nanops.nanmedian)
    tm.assert_frame_equal(result, exp)

    df = DataFrame(np.random.randn(1000, 5))
    rs = df.groupby(labels).agg(np.median)
    xp = df.groupby(labels).median()
    tm.assert_frame_equal(rs, xp)


def test_median_empty_bins(observed):
    df = DataFrame(np.random.randint(0, 44, 500))

    grps = range(0, 55, 5)
    bins = pd.cut(df[0], grps)

    result = df.groupby(bins, observed=observed).median()
    expected = df.groupby(bins, observed=observed).agg(lambda x: x.median())
    tm.assert_frame_equal(result, expected)


@pytest.mark.parametrize(
    "dtype", ["int8", "int16", "int32", "int64", "float32", "float64", "uint64"]
)
@pytest.mark.parametrize(
    "method,data",
    [
        ("first", {"df": [{"a": 1, "b": 1}, {"a": 2, "b": 3}]}),
        ("last", {"df": [{"a": 1, "b": 2}, {"a": 2, "b": 4}]}),
        ("min", {"df": [{"a": 1, "b": 1}, {"a": 2, "b": 3}]}),
        ("max", {"df": [{"a": 1, "b": 2}, {"a": 2, "b": 4}]}),
        ("nth", {"df": [{"a": 1, "b": 2}, {"a": 2, "b": 4}], "args": [1]}),
        ("count", {"df": [{"a": 1, "b": 2}, {"a": 2, "b": 2}], "out_type": "int64"}),
    ],
)
def test_groupby_non_arithmetic_agg_types(dtype, method, data):
    # GH9311, GH6620
    df = DataFrame(
        [{"a": 1, "b": 1}, {"a": 1, "b": 2}, {"a": 2, "b": 3}, {"a": 2, "b": 4}]
    )

    df["b"] = df.b.astype(dtype)

    if "args" not in data:
        data["args"] = []

    if "out_type" in data:
        out_type = data["out_type"]
    else:
        out_type = dtype

    exp = data["df"]
    df_out = DataFrame(exp)

    df_out["b"] = df_out.b.astype(out_type)
    df_out.set_index("a", inplace=True)

    grpd = df.groupby("a")
    t = getattr(grpd, method)(*data["args"])
    tm.assert_frame_equal(t, df_out)


@pytest.mark.parametrize(
    "i",
    [
        (
            Timestamp("2011-01-15 12:50:28.502376"),
            Timestamp("2011-01-20 12:50:28.593448"),
        ),
        (24650000000000001, 24650000000000002),
    ],
)
def test_groupby_non_arithmetic_agg_int_like_precision(i):
    # see gh-6620, gh-9311
    df = DataFrame([{"a": 1, "b": i[0]}, {"a": 1, "b": i[1]}])

    grp_exp = {
        "first": {"expected": i[0]},
        "last": {"expected": i[1]},
        "min": {"expected": i[0]},
        "max": {"expected": i[1]},
        "nth": {"expected": i[1], "args": [1]},
        "count": {"expected": 2},
    }

    for method, data in grp_exp.items():
        if "args" not in data:
            data["args"] = []

        grouped = df.groupby("a")
        res = getattr(grouped, method)(*data["args"])

        assert res.iloc[0].b == data["expected"]


@pytest.mark.parametrize(
    "func, values",
    [
        ("idxmin", {"c_int": [0, 2], "c_float": [1, 3], "c_date": [1, 2]}),
        ("idxmax", {"c_int": [1, 3], "c_float": [0, 2], "c_date": [0, 3]}),
    ],
)
@pytest.mark.filterwarnings("ignore:.*Select only valid:FutureWarning")
def test_idxmin_idxmax_returns_int_types(func, values):
    # GH 25444
    df = DataFrame(
        {
            "name": ["A", "A", "B", "B"],
            "c_int": [1, 2, 3, 4],
            "c_float": [4.02, 3.03, 2.04, 1.05],
            "c_date": ["2019", "2018", "2016", "2017"],
        }
    )
    df["c_date"] = pd.to_datetime(df["c_date"])
    df["c_date_tz"] = df["c_date"].dt.tz_localize("US/Pacific")
    df["c_timedelta"] = df["c_date"] - df["c_date"].iloc[0]
    df["c_period"] = df["c_date"].dt.to_period("W")
    df["c_Integer"] = df["c_int"].astype("Int64")
    df["c_Floating"] = df["c_float"].astype("Float64")

    result = getattr(df.groupby("name"), func)()

    expected = DataFrame(values, index=Index(["A", "B"], name="name"))
    expected["c_date_tz"] = expected["c_date"]
    expected["c_timedelta"] = expected["c_date"]
    expected["c_period"] = expected["c_date"]
    expected["c_Integer"] = expected["c_int"]
    expected["c_Floating"] = expected["c_float"]

    tm.assert_frame_equal(result, expected)


def test_idxmin_idxmax_axis1():
    df = DataFrame(np.random.randn(10, 4), columns=["A", "B", "C", "D"])
    df["A"] = [1, 2, 3, 1, 2, 3, 1, 2, 3, 4]

    gb = df.groupby("A")

    res = gb.idxmax(axis=1)

    alt = df.iloc[:, 1:].idxmax(axis=1)
    indexer = res.index.get_level_values(1)

    tm.assert_series_equal(alt[indexer], res.droplevel("A"))

    df["E"] = date_range("2016-01-01", periods=10)
    gb2 = df.groupby("A")

    msg = "reduction operation 'argmax' not allowed for this dtype"
    with pytest.raises(TypeError, match=msg):
        gb2.idxmax(axis=1)


def test_groupby_cumprod():
    # GH 4095
    df = DataFrame({"key": ["b"] * 10, "value": 2})

    actual = df.groupby("key")["value"].cumprod()
    expected = df.groupby("key")["value"].apply(lambda x: x.cumprod())
    expected.name = "value"
    tm.assert_series_equal(actual, expected)

    df = DataFrame({"key": ["b"] * 100, "value": 2})
    actual = df.groupby("key")["value"].cumprod()
    # if overflows, groupby product casts to float
    # while numpy passes back invalid values
    df["value"] = df["value"].astype(float)
    expected = df.groupby("key")["value"].apply(lambda x: x.cumprod())
    expected.name = "value"
    tm.assert_series_equal(actual, expected)


def scipy_sem(*args, **kwargs):
    from scipy.stats import sem

    return sem(*args, ddof=1, **kwargs)


@pytest.mark.parametrize(
    "op,targop",
    [
        ("mean", np.mean),
        ("median", np.median),
        ("std", np.std),
        ("var", np.var),
        ("sum", np.sum),
        ("prod", np.prod),
        ("min", np.min),
        ("max", np.max),
        ("first", lambda x: x.iloc[0]),
        ("last", lambda x: x.iloc[-1]),
        ("count", np.size),
        pytest.param("sem", scipy_sem, marks=td.skip_if_no_scipy),
    ],
)
def test_ops_general(op, targop):
    df = DataFrame(np.random.randn(1000))
    labels = np.random.randint(0, 50, size=1000).astype(float)

    result = getattr(df.groupby(labels), op)()
    expected = df.groupby(labels).agg(targop)
    tm.assert_frame_equal(result, expected)


def test_max_nan_bug():
    raw = """,Date,app,File
-04-23,2013-04-23 00:00:00,,log080001.log
-05-06,2013-05-06 00:00:00,,log.log
-05-07,2013-05-07 00:00:00,OE,xlsx"""

    df = pd.read_csv(StringIO(raw), parse_dates=[0])
    gb = df.groupby("Date")
    r = gb[["File"]].max()
    e = gb["File"].max().to_frame()
    tm.assert_frame_equal(r, e)
    assert not r["File"].isna().any()


def test_nlargest():
    a = Series([1, 3, 5, 7, 2, 9, 0, 4, 6, 10])
    b = Series(list("a" * 5 + "b" * 5))
    gb = a.groupby(b)
    r = gb.nlargest(3)
    e = Series(
        [7, 5, 3, 10, 9, 6],
        index=MultiIndex.from_arrays([list("aaabbb"), [3, 2, 1, 9, 5, 8]]),
    )
    tm.assert_series_equal(r, e)

    a = Series([1, 1, 3, 2, 0, 3, 3, 2, 1, 0])
    gb = a.groupby(b)
    e = Series(
        [3, 2, 1, 3, 3, 2],
        index=MultiIndex.from_arrays([list("aaabbb"), [2, 3, 1, 6, 5, 7]]),
    )
    tm.assert_series_equal(gb.nlargest(3, keep="last"), e)


def test_nlargest_mi_grouper():
    # see gh-21411
    npr = np.random.RandomState(123456789)

    dts = date_range("20180101", periods=10)
    iterables = [dts, ["one", "two"]]

    idx = MultiIndex.from_product(iterables, names=["first", "second"])
    s = Series(npr.randn(20), index=idx)

    result = s.groupby("first").nlargest(1)

    exp_idx = MultiIndex.from_tuples(
        [
            (dts[0], dts[0], "one"),
            (dts[1], dts[1], "one"),
            (dts[2], dts[2], "one"),
            (dts[3], dts[3], "two"),
            (dts[4], dts[4], "one"),
            (dts[5], dts[5], "one"),
            (dts[6], dts[6], "one"),
            (dts[7], dts[7], "one"),
            (dts[8], dts[8], "two"),
            (dts[9], dts[9], "one"),
        ],
        names=["first", "first", "second"],
    )

    exp_values = [
        2.2129019979039612,
        1.8417114045748335,
        0.858963679564603,
        1.3759151378258088,
        0.9430284594687134,
        0.5296914208183142,
        0.8318045593815487,
        -0.8476703342910327,
        0.3804446884133735,
        -0.8028845810770998,
    ]

    expected = Series(exp_values, index=exp_idx)
    tm.assert_series_equal(result, expected, check_exact=False, rtol=1e-3)


def test_nsmallest():
    a = Series([1, 3, 5, 7, 2, 9, 0, 4, 6, 10])
    b = Series(list("a" * 5 + "b" * 5))
    gb = a.groupby(b)
    r = gb.nsmallest(3)
    e = Series(
        [1, 2, 3, 0, 4, 6],
        index=MultiIndex.from_arrays([list("aaabbb"), [0, 4, 1, 6, 7, 8]]),
    )
    tm.assert_series_equal(r, e)

    a = Series([1, 1, 3, 2, 0, 3, 3, 2, 1, 0])
    gb = a.groupby(b)
    e = Series(
        [0, 1, 1, 0, 1, 2],
        index=MultiIndex.from_arrays([list("aaabbb"), [4, 1, 0, 9, 8, 7]]),
    )
    tm.assert_series_equal(gb.nsmallest(3, keep="last"), e)


@pytest.mark.parametrize(
    "data, groups",
    [([0, 1, 2, 3], [0, 0, 1, 1]), ([0], [0])],
)
@pytest.mark.parametrize("method", ["nlargest", "nsmallest"])
def test_nlargest_and_smallest_noop(data, groups, method):
    # GH 15272, GH 16345, GH 29129
    # Test nlargest/smallest when it results in a noop,
    # i.e. input is sorted and group size <= n
    if method == "nlargest":
        data = list(reversed(data))
    ser = Series(data, name="a")
    result = getattr(ser.groupby(groups), method)(n=2)
    expected = Series(data, index=MultiIndex.from_arrays([groups, ser.index]), name="a")
    tm.assert_series_equal(result, expected)


@pytest.mark.parametrize("func", ["cumprod", "cumsum"])
def test_numpy_compat(func):
    # see gh-12811
    df = DataFrame({"A": [1, 2, 1], "B": [1, 2, 3]})
    g = df.groupby("A")

    msg = "numpy operations are not valid with groupby"

    with pytest.raises(UnsupportedFunctionCall, match=msg):
        getattr(g, func)(1, 2, 3)
    with pytest.raises(UnsupportedFunctionCall, match=msg):
        getattr(g, func)(foo=1)


def test_cummin(dtypes_for_minmax):
    dtype = dtypes_for_minmax[0]
    min_val = dtypes_for_minmax[1]

    # GH 15048
    base_df = DataFrame({"A": [1, 1, 1, 1, 2, 2, 2, 2], "B": [3, 4, 3, 2, 2, 3, 2, 1]})
    expected_mins = [3, 3, 3, 2, 2, 2, 2, 1]

    df = base_df.astype(dtype)

    expected = DataFrame({"B": expected_mins}).astype(dtype)
    result = df.groupby("A").cummin()
    tm.assert_frame_equal(result, expected)
    result = df.groupby("A").B.apply(lambda x: x.cummin()).to_frame()
    tm.assert_frame_equal(result, expected)

    # Test w/ min value for dtype
    df.loc[[2, 6], "B"] = min_val
    df.loc[[1, 5], "B"] = min_val + 1
    expected.loc[[2, 3, 6, 7], "B"] = min_val
    expected.loc[[1, 5], "B"] = min_val + 1  # should not be rounded to min_val
    result = df.groupby("A").cummin()
    tm.assert_frame_equal(result, expected, check_exact=True)
    expected = df.groupby("A").B.apply(lambda x: x.cummin()).to_frame()
    tm.assert_frame_equal(result, expected, check_exact=True)

    # Test nan in some values
    base_df.loc[[0, 2, 4, 6], "B"] = np.nan
    expected = DataFrame({"B": [np.nan, 4, np.nan, 2, np.nan, 3, np.nan, 1]})
    result = base_df.groupby("A").cummin()
    tm.assert_frame_equal(result, expected)
    expected = base_df.groupby("A").B.apply(lambda x: x.cummin()).to_frame()
    tm.assert_frame_equal(result, expected)

    # GH 15561
    df = DataFrame({"a": [1], "b": pd.to_datetime(["2001"])})
    expected = Series(pd.to_datetime("2001"), index=[0], name="b")

    result = df.groupby("a")["b"].cummin()
    tm.assert_series_equal(expected, result)

    # GH 15635
    df = DataFrame({"a": [1, 2, 1], "b": [1, 2, 2]})
    result = df.groupby("a").b.cummin()
    expected = Series([1, 2, 1], name="b")
    tm.assert_series_equal(result, expected)


@pytest.mark.parametrize("method", ["cummin", "cummax"])
@pytest.mark.parametrize("dtype", ["UInt64", "Int64", "Float64", "float", "boolean"])
def test_cummin_max_all_nan_column(method, dtype):
    base_df = DataFrame({"A": [1, 1, 1, 1, 2, 2, 2, 2], "B": [np.nan] * 8})
    base_df["B"] = base_df["B"].astype(dtype)
    grouped = base_df.groupby("A")

    expected = DataFrame({"B": [np.nan] * 8}, dtype=dtype)
    result = getattr(grouped, method)()
    tm.assert_frame_equal(expected, result)

    result = getattr(grouped["B"], method)().to_frame()
    tm.assert_frame_equal(expected, result)


def test_cummax(dtypes_for_minmax):
    dtype = dtypes_for_minmax[0]
    max_val = dtypes_for_minmax[2]

    # GH 15048
    base_df = DataFrame({"A": [1, 1, 1, 1, 2, 2, 2, 2], "B": [3, 4, 3, 2, 2, 3, 2, 1]})
    expected_maxs = [3, 4, 4, 4, 2, 3, 3, 3]

    df = base_df.astype(dtype)

    expected = DataFrame({"B": expected_maxs}).astype(dtype)
    result = df.groupby("A").cummax()
    tm.assert_frame_equal(result, expected)
    result = df.groupby("A").B.apply(lambda x: x.cummax()).to_frame()
    tm.assert_frame_equal(result, expected)

    # Test w/ max value for dtype
    df.loc[[2, 6], "B"] = max_val
    expected.loc[[2, 3, 6, 7], "B"] = max_val
    result = df.groupby("A").cummax()
    tm.assert_frame_equal(result, expected)
    expected = df.groupby("A").B.apply(lambda x: x.cummax()).to_frame()
    tm.assert_frame_equal(result, expected)

    # Test nan in some values
    base_df.loc[[0, 2, 4, 6], "B"] = np.nan
    expected = DataFrame({"B": [np.nan, 4, np.nan, 4, np.nan, 3, np.nan, 3]})
    result = base_df.groupby("A").cummax()
    tm.assert_frame_equal(result, expected)
    expected = base_df.groupby("A").B.apply(lambda x: x.cummax()).to_frame()
    tm.assert_frame_equal(result, expected)

    # GH 15561
    df = DataFrame({"a": [1], "b": pd.to_datetime(["2001"])})
    expected = Series(pd.to_datetime("2001"), index=[0], name="b")

    result = df.groupby("a")["b"].cummax()
    tm.assert_series_equal(expected, result)

    # GH 15635
    df = DataFrame({"a": [1, 2, 1], "b": [2, 1, 1]})
    result = df.groupby("a").b.cummax()
    expected = Series([2, 1, 2], name="b")
    tm.assert_series_equal(result, expected)


@pytest.mark.parametrize("method", ["cummin", "cummax"])
@pytest.mark.parametrize("dtype", ["float", "Int64", "Float64"])
@pytest.mark.parametrize(
    "groups,expected_data",
    [
        ([1, 1, 1], [1, None, None]),
        ([1, 2, 3], [1, None, 2]),
        ([1, 3, 3], [1, None, None]),
    ],
)
def test_cummin_max_skipna(method, dtype, groups, expected_data):
    # GH-34047
    df = DataFrame({"a": Series([1, None, 2], dtype=dtype)})
    gb = df.groupby(groups)["a"]

    result = getattr(gb, method)(skipna=False)
    expected = Series(expected_data, dtype=dtype, name="a")

    tm.assert_series_equal(result, expected)


@pytest.mark.parametrize("method", ["cummin", "cummax"])
def test_cummin_max_skipna_multiple_cols(method):
    # Ensure missing value in "a" doesn't cause "b" to be nan-filled
    df = DataFrame({"a": [np.nan, 2.0, 2.0], "b": [2.0, 2.0, 2.0]})
    gb = df.groupby([1, 1, 1])[["a", "b"]]

    result = getattr(gb, method)(skipna=False)
    expected = DataFrame({"a": [np.nan, np.nan, np.nan], "b": [2.0, 2.0, 2.0]})

    tm.assert_frame_equal(result, expected)


@td.skip_if_32bit
@pytest.mark.parametrize("method", ["cummin", "cummax"])
@pytest.mark.parametrize(
    "dtype,val", [("UInt64", np.iinfo("uint64").max), ("Int64", 2 ** 53 + 1)]
)
def test_nullable_int_not_cast_as_float(method, dtype, val):
    data = [val, pd.NA]
    df = DataFrame({"grp": [1, 1], "b": data}, dtype=dtype)
    grouped = df.groupby("grp")

    result = grouped.transform(method)
    expected = DataFrame({"b": data}, dtype=dtype)

    tm.assert_frame_equal(result, expected)


@pytest.mark.parametrize(
    "in_vals, out_vals",
    [
        # Basics: strictly increasing (T), strictly decreasing (F),
        # abs val increasing (F), non-strictly increasing (T)
        ([1, 2, 5, 3, 2, 0, 4, 5, -6, 1, 1], [True, False, False, True]),
        # Test with inf vals
        (
            [1, 2.1, np.inf, 3, 2, np.inf, -np.inf, 5, 11, 1, -np.inf],
            [True, False, True, False],
        ),
        # Test with nan vals; should always be False
        (
            [1, 2, np.nan, 3, 2, np.nan, np.nan, 5, -np.inf, 1, np.nan],
            [False, False, False, False],
        ),
    ],
)
def test_is_monotonic_increasing(in_vals, out_vals):
    # GH 17015
    source_dict = {
        "A": ["1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11"],
        "B": ["a", "a", "a", "b", "b", "b", "c", "c", "c", "d", "d"],
        "C": in_vals,
    }
    df = DataFrame(source_dict)
    result = df.groupby("B").C.is_monotonic_increasing
    index = Index(list("abcd"), name="B")
    expected = Series(index=index, data=out_vals, name="C")
    tm.assert_series_equal(result, expected)

    # Also check result equal to manually taking x.is_monotonic_increasing.
    expected = df.groupby(["B"]).C.apply(lambda x: x.is_monotonic_increasing)
    tm.assert_series_equal(result, expected)


@pytest.mark.parametrize(
    "in_vals, out_vals",
    [
        # Basics: strictly decreasing (T), strictly increasing (F),
        # abs val decreasing (F), non-strictly increasing (T)
        ([10, 9, 7, 3, 4, 5, -3, 2, 0, 1, 1], [True, False, False, True]),
        # Test with inf vals
        (
            [np.inf, 1, -np.inf, np.inf, 2, -3, -np.inf, 5, -3, -np.inf, -np.inf],
            [True, True, False, True],
        ),
        # Test with nan vals; should always be False
        (
            [1, 2, np.nan, 3, 2, np.nan, np.nan, 5, -np.inf, 1, np.nan],
            [False, False, False, False],
        ),
    ],
)
def test_is_monotonic_decreasing(in_vals, out_vals):
    # GH 17015
    source_dict = {
        "A": ["1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11"],
        "B": ["a", "a", "a", "b", "b", "b", "c", "c", "c", "d", "d"],
        "C": in_vals,
    }

    df = DataFrame(source_dict)
    result = df.groupby("B").C.is_monotonic_decreasing
    index = Index(list("abcd"), name="B")
    expected = Series(index=index, data=out_vals, name="C")
    tm.assert_series_equal(result, expected)


# describe
# --------------------------------


def test_apply_describe_bug(mframe):
    grouped = mframe.groupby(level="first")
    grouped.describe()  # it works!


def test_series_describe_multikey():
    ts = tm.makeTimeSeries()
    grouped = ts.groupby([lambda x: x.year, lambda x: x.month])
    result = grouped.describe()
    tm.assert_series_equal(result["mean"], grouped.mean(), check_names=False)
    tm.assert_series_equal(result["std"], grouped.std(), check_names=False)
    tm.assert_series_equal(result["min"], grouped.min(), check_names=False)


def test_series_describe_single():
    ts = tm.makeTimeSeries()
    grouped = ts.groupby(lambda x: x.month)
    result = grouped.apply(lambda x: x.describe())
    expected = grouped.describe().stack()
    tm.assert_series_equal(result, expected)


def test_series_index_name(df):
    grouped = df.loc[:, ["C"]].groupby(df["A"])
    result = grouped.agg(lambda x: x.mean())
    assert result.index.name == "A"


def test_frame_describe_multikey(tsframe):
    grouped = tsframe.groupby([lambda x: x.year, lambda x: x.month])
    result = grouped.describe()
    desc_groups = []
    for col in tsframe:
        group = grouped[col].describe()
        # GH 17464 - Remove duplicate MultiIndex levels
        group_col = MultiIndex(
            levels=[[col], group.columns],
            codes=[[0] * len(group.columns), range(len(group.columns))],
        )
        group = DataFrame(group.values, columns=group_col, index=group.index)
        desc_groups.append(group)
    expected = pd.concat(desc_groups, axis=1)
    tm.assert_frame_equal(result, expected)

    groupedT = tsframe.groupby({"A": 0, "B": 0, "C": 1, "D": 1}, axis=1)
    result = groupedT.describe()
    expected = tsframe.describe().T
    tm.assert_frame_equal(result, expected)


def test_frame_describe_tupleindex():

    # GH 14848 - regression from 0.19.0 to 0.19.1
    df1 = DataFrame(
        {
            "x": [1, 2, 3, 4, 5] * 3,
            "y": [10, 20, 30, 40, 50] * 3,
            "z": [100, 200, 300, 400, 500] * 3,
        }
    )
    df1["k"] = [(0, 0, 1), (0, 1, 0), (1, 0, 0)] * 5
    df2 = df1.rename(columns={"k": "key"})
    msg = "Names should be list-like for a MultiIndex"
    with pytest.raises(ValueError, match=msg):
        df1.groupby("k").describe()
    with pytest.raises(ValueError, match=msg):
        df2.groupby("key").describe()


def test_frame_describe_unstacked_format():
    # GH 4792
    prices = {
        Timestamp("2011-01-06 10:59:05", tz=None): 24990,
        Timestamp("2011-01-06 12:43:33", tz=None): 25499,
        Timestamp("2011-01-06 12:54:09", tz=None): 25499,
    }
    volumes = {
        Timestamp("2011-01-06 10:59:05", tz=None): 1500000000,
        Timestamp("2011-01-06 12:43:33", tz=None): 5000000000,
        Timestamp("2011-01-06 12:54:09", tz=None): 100000000,
    }
    df = DataFrame({"PRICE": prices, "VOLUME": volumes})
    result = df.groupby("PRICE").VOLUME.describe()
    data = [
        df[df.PRICE == 24990].VOLUME.describe().values.tolist(),
        df[df.PRICE == 25499].VOLUME.describe().values.tolist(),
    ]
    expected = DataFrame(
        data,
        index=Index([24990, 25499], name="PRICE"),
        columns=["count", "mean", "std", "min", "25%", "50%", "75%", "max"],
    )
    tm.assert_frame_equal(result, expected)


@pytest.mark.filterwarnings(
    "ignore:"
    "indexing past lexsort depth may impact performance:"
    "pandas.errors.PerformanceWarning"
)
@pytest.mark.parametrize("as_index", [True, False])
def test_describe_with_duplicate_output_column_names(as_index):
    # GH 35314
    df = DataFrame(
        {
            "a": [99, 99, 99, 88, 88, 88],
            "b": [1, 2, 3, 4, 5, 6],
            "c": [10, 20, 30, 40, 50, 60],
        },
        columns=["a", "b", "b"],
        copy=False,
    )

    expected = (
        DataFrame.from_records(
            [
                ("a", "count", 3.0, 3.0),
                ("a", "mean", 88.0, 99.0),
                ("a", "std", 0.0, 0.0),
                ("a", "min", 88.0, 99.0),
                ("a", "25%", 88.0, 99.0),
                ("a", "50%", 88.0, 99.0),
                ("a", "75%", 88.0, 99.0),
                ("a", "max", 88.0, 99.0),
                ("b", "count", 3.0, 3.0),
                ("b", "mean", 5.0, 2.0),
                ("b", "std", 1.0, 1.0),
                ("b", "min", 4.0, 1.0),
                ("b", "25%", 4.5, 1.5),
                ("b", "50%", 5.0, 2.0),
                ("b", "75%", 5.5, 2.5),
                ("b", "max", 6.0, 3.0),
                ("b", "count", 3.0, 3.0),
                ("b", "mean", 5.0, 2.0),
                ("b", "std", 1.0, 1.0),
                ("b", "min", 4.0, 1.0),
                ("b", "25%", 4.5, 1.5),
                ("b", "50%", 5.0, 2.0),
                ("b", "75%", 5.5, 2.5),
                ("b", "max", 6.0, 3.0),
            ],
        )
        .set_index([0, 1])
        .T
    )
    expected.columns.names = [None, None]
    expected.index = Index([88, 99], name="a")

    if as_index:
        expected = expected.drop(columns=["a"], level=0)
    else:
        expected = expected.reset_index(drop=True)

    result = df.groupby("a", as_index=as_index).describe()

    tm.assert_frame_equal(result, expected)


def test_groupby_mean_no_overflow():
    # Regression test for (#22487)
    df = DataFrame(
        {
            "user": ["A", "A", "A", "A", "A"],
            "connections": [4970, 4749, 4719, 4704, 18446744073699999744],
        }
    )
    assert df.groupby("user")["connections"].mean()["A"] == 3689348814740003840


@pytest.mark.parametrize(
    "values",
    [
        {
            "a": [1, 1, 1, 2, 2, 2, 3, 3, 3],
            "b": [1, pd.NA, 2, 1, pd.NA, 2, 1, pd.NA, 2],
        },
        {"a": [1, 1, 2, 2, 3, 3], "b": [1, 2, 1, 2, 1, 2]},
    ],
)
@pytest.mark.parametrize("function", ["mean", "median", "var"])
def test_apply_to_nullable_integer_returns_float(values, function):
    # https://github.com/pandas-dev/pandas/issues/32219
    output = 0.5 if function == "var" else 1.5
    arr = np.array([output] * 3, dtype=float)
    idx = Index([1, 2, 3], name="a", dtype="Int64")
    expected = DataFrame({"b": arr}, index=idx).astype("Float64")

    groups = DataFrame(values, dtype="Int64").groupby("a")

    result = getattr(groups, function)()
    tm.assert_frame_equal(result, expected)

    result = groups.agg(function)
    tm.assert_frame_equal(result, expected)

    result = groups.agg([function])
    expected.columns = MultiIndex.from_tuples([("b", function)])
    tm.assert_frame_equal(result, expected)


def test_groupby_sum_below_mincount_nullable_integer():
    # https://github.com/pandas-dev/pandas/issues/32861
    df = DataFrame({"a": [0, 1, 2], "b": [0, 1, 2], "c": [0, 1, 2]}, dtype="Int64")
    grouped = df.groupby("a")
    idx = Index([0, 1, 2], name="a", dtype="Int64")

    result = grouped["b"].sum(min_count=2)
    expected = Series([pd.NA] * 3, dtype="Int64", index=idx, name="b")
    tm.assert_series_equal(result, expected)

    result = grouped.sum(min_count=2)
    expected = DataFrame({"b": [pd.NA] * 3, "c": [pd.NA] * 3}, dtype="Int64", index=idx)
    tm.assert_frame_equal(result, expected)


def test_mean_on_timedelta():
    # GH 17382
    df = DataFrame({"time": pd.to_timedelta(range(10)), "cat": ["A", "B"] * 5})
    result = df.groupby("cat")["time"].mean()
    expected = Series(
        pd.to_timedelta([4, 5]), name="time", index=Index(["A", "B"], name="cat")
    )
    tm.assert_series_equal(result, expected)


def test_groupby_sum_timedelta_with_nat():
    # GH#42659
    df = DataFrame(
        {
            "a": [1, 1, 2, 2],
            "b": [pd.Timedelta("1d"), pd.Timedelta("2d"), pd.Timedelta("3d"), pd.NaT],
        }
    )
    td3 = pd.Timedelta(days=3)

    gb = df.groupby("a")

    res = gb.sum()
    expected = DataFrame({"b": [td3, td3]}, index=Index([1, 2], name="a"))
    tm.assert_frame_equal(res, expected)

    res = gb["b"].sum()
    tm.assert_series_equal(res, expected["b"])

    res = gb["b"].sum(min_count=2)
    expected = Series([td3, pd.NaT], dtype="m8[ns]", name="b", index=expected.index)
    tm.assert_series_equal(res, expected)