"""
Base and utility classes for tseries type pandas objects.
"""
import operator
from typing import Any, List, Optional, Set

import numpy as np

from pandas._libs import NaT, iNaT, join as libjoin, lib
from pandas._libs.algos import unique_deltas
from pandas._libs.tslibs import timezones
from pandas.compat.numpy import function as nv
from pandas.errors import AbstractMethodError
from pandas.util._decorators import Appender, cache_readonly

from pandas.core.dtypes.common import (
    ensure_int64,
    is_bool_dtype,
    is_categorical_dtype,
    is_dtype_equal,
    is_float,
    is_integer,
    is_list_like,
    is_period_dtype,
    is_scalar,
    needs_i8_conversion,
)
from pandas.core.dtypes.concat import concat_compat
from pandas.core.dtypes.generic import ABCIndex, ABCIndexClass, ABCSeries
from pandas.core.dtypes.missing import is_valid_nat_for_dtype, isna

from pandas.core import algorithms
from pandas.core.accessor import PandasDelegate
from pandas.core.arrays import DatetimeArray, ExtensionArray, TimedeltaArray
from pandas.core.arrays.datetimelike import DatetimeLikeArrayMixin
from pandas.core.base import _shared_docs
import pandas.core.indexes.base as ibase
from pandas.core.indexes.base import Index, _index_shared_docs
from pandas.core.indexes.extension import (
    ExtensionIndex,
    inherit_names,
    make_wrapped_arith_op,
)
from pandas.core.indexes.numeric import Int64Index
from pandas.core.ops import get_op_result_name
from pandas.core.tools.timedeltas import to_timedelta

from pandas.tseries.frequencies import DateOffset, to_offset

_index_doc_kwargs = dict(ibase._index_doc_kwargs)


def _join_i8_wrapper(joinf, with_indexers: bool = True):
    """
    Create the join wrapper methods.
    """

    @staticmethod  # type: ignore
    def wrapper(left, right):
        if isinstance(left, (np.ndarray, ABCIndex, ABCSeries, DatetimeLikeArrayMixin)):
            left = left.view("i8")
        if isinstance(right, (np.ndarray, ABCIndex, ABCSeries, DatetimeLikeArrayMixin)):
            right = right.view("i8")

        results = joinf(left, right)
        if with_indexers:
            # dtype should be timedelta64[ns] for TimedeltaIndex
            #  and datetime64[ns] for DatetimeIndex
            dtype = left.dtype.base

            join_index, left_indexer, right_indexer = results
            join_index = join_index.view(dtype)
            return join_index, left_indexer, right_indexer
        return results

    return wrapper


@inherit_names(
    ["inferred_freq", "_isnan", "_resolution", "resolution"],
    DatetimeLikeArrayMixin,
    cache=True,
)
@inherit_names(
    ["__iter__", "mean", "freq", "freqstr", "_ndarray_values", "asi8", "_box_values"],
    DatetimeLikeArrayMixin,
)
class DatetimeIndexOpsMixin(ExtensionIndex):
    """
    Common ops mixin to support a unified interface datetimelike Index.
    """

    _data: ExtensionArray
    freq: Optional[DateOffset]
    freqstr: Optional[str]
    _resolution: int
    _bool_ops: List[str] = []
    _field_ops: List[str] = []

    hasnans = cache_readonly(DatetimeLikeArrayMixin._hasnans.fget)  # type: ignore
    _hasnans = hasnans  # for index / array -agnostic code

    @property
    def is_all_dates(self) -> bool:
        return True

    # ------------------------------------------------------------------------
    # Abstract data attributes

    @property
    def values(self):
        # Note: PeriodArray overrides this to return an ndarray of objects.
        return self._data._data

    def __array_wrap__(self, result, context=None):
        """
        Gets called after a ufunc.
        """
        result = lib.item_from_zerodim(result)
        if is_bool_dtype(result) or lib.is_scalar(result):
            return result

        attrs = self._get_attributes_dict()
        if not is_period_dtype(self) and attrs["freq"]:
            # no need to infer if freq is None
            attrs["freq"] = "infer"
        return Index(result, **attrs)

    # ------------------------------------------------------------------------

    def equals(self, other) -> bool:
        """
        Determines if two Index objects contain the same elements.
        """
        if self.is_(other):
            return True

        if not isinstance(other, ABCIndexClass):
            return False
        elif not isinstance(other, type(self)):
            try:
                other = type(self)(other)
            except (ValueError, TypeError, OverflowError):
                # e.g.
                #  ValueError -> cannot parse str entry, or OutOfBoundsDatetime
                #  TypeError  -> trying to convert IntervalIndex to DatetimeIndex
                #  OverflowError -> Index([very_large_timedeltas])
                return False

        if not is_dtype_equal(self.dtype, other.dtype):
            # have different timezone
            return False

        return np.array_equal(self.asi8, other.asi8)

    @Appender(_index_shared_docs["contains"] % _index_doc_kwargs)
    def __contains__(self, key: Any) -> bool:
        hash(key)
        try:
            res = self.get_loc(key)
        except (KeyError, TypeError, ValueError):
            return False
        return bool(
            is_scalar(res) or isinstance(res, slice) or (is_list_like(res) and len(res))
        )

    # Try to run function on index first, and then on elements of index
    # Especially important for group-by functionality
    def map(self, mapper, na_action=None):
        try:
            result = mapper(self)

            # Try to use this result if we can
            if isinstance(result, np.ndarray):
                result = Index(result)

            if not isinstance(result, Index):
                raise TypeError("The map function must return an Index object")
            return result
        except Exception:
            return self.astype(object).map(mapper)

    def sort_values(self, return_indexer=False, ascending=True):
        """
        Return sorted copy of Index.
        """
        if return_indexer:
            _as = self.argsort()
            if not ascending:
                _as = _as[::-1]
            sorted_index = self.take(_as)
            return sorted_index, _as
        else:
            # NB: using asi8 instead of _ndarray_values matters in numpy 1.18
            #  because the treatment of NaT has been changed to put NaT last
            #  instead of first.
            sorted_values = np.sort(self.asi8)

            freq = self.freq
            if freq is not None and not is_period_dtype(self):
                if freq.n > 0 and not ascending:
                    freq = freq * -1
                elif freq.n < 0 and ascending:
                    freq = freq * -1

            if not ascending:
                sorted_values = sorted_values[::-1]

            arr = type(self._data)._simple_new(
                sorted_values, dtype=self.dtype, freq=freq
            )
            return self._simple_new(arr, name=self.name)

    @Appender(_index_shared_docs["take"] % _index_doc_kwargs)
    def take(self, indices, axis=0, allow_fill=True, fill_value=None, **kwargs):
        nv.validate_take(tuple(), kwargs)
        indices = ensure_int64(indices)

        maybe_slice = lib.maybe_indices_to_slice(indices, len(self))
        if isinstance(maybe_slice, slice):
            return self[maybe_slice]

        return ExtensionIndex.take(
            self, indices, axis, allow_fill, fill_value, **kwargs
        )

    @Appender(_shared_docs["searchsorted"])
    def searchsorted(self, value, side="left", sorter=None):
        if isinstance(value, str):
            raise TypeError(
                "searchsorted requires compatible dtype or scalar, "
                f"not {type(value).__name__}"
            )
        if isinstance(value, Index):
            value = value._data

        return self._data.searchsorted(value, side=side, sorter=sorter)

    _can_hold_na = True

    _na_value = NaT
    """The expected NA value to use with this index."""

    def _convert_tolerance(self, tolerance, target):
        tolerance = np.asarray(to_timedelta(tolerance).to_numpy())

        if target.size != tolerance.size and tolerance.size > 1:
            raise ValueError("list-like tolerance size must match target index size")
        return tolerance

    def tolist(self) -> List:
        """
        Return a list of the underlying data.
        """
        return list(self.astype(object))

    def min(self, axis=None, skipna=True, *args, **kwargs):
        """
        Return the minimum value of the Index or minimum along
        an axis.

        See Also
        --------
        numpy.ndarray.min
        Series.min : Return the minimum value in a Series.
        """
        nv.validate_min(args, kwargs)
        nv.validate_minmax_axis(axis)

        if not len(self):
            return self._na_value

        i8 = self.asi8
        try:
            # quick check
            if len(i8) and self.is_monotonic:
                if i8[0] != iNaT:
                    return self._box_func(i8[0])

            if self.hasnans:
                if skipna:
                    min_stamp = self[~self._isnan].asi8.min()
                else:
                    return self._na_value
            else:
                min_stamp = i8.min()
            return self._box_func(min_stamp)
        except ValueError:
            return self._na_value

    def argmin(self, axis=None, skipna=True, *args, **kwargs):
        """
        Returns the indices of the minimum values along an axis.

        See `numpy.ndarray.argmin` for more information on the
        `axis` parameter.

        See Also
        --------
        numpy.ndarray.argmin
        """
        nv.validate_argmin(args, kwargs)
        nv.validate_minmax_axis(axis)

        i8 = self.asi8
        if self.hasnans:
            mask = self._isnan
            if mask.all() or not skipna:
                return -1
            i8 = i8.copy()
            i8[mask] = np.iinfo("int64").max
        return i8.argmin()

    def max(self, axis=None, skipna=True, *args, **kwargs):
        """
        Return the maximum value of the Index or maximum along
        an axis.

        See Also
        --------
        numpy.ndarray.max
        Series.max : Return the maximum value in a Series.
        """
        nv.validate_max(args, kwargs)
        nv.validate_minmax_axis(axis)

        if not len(self):
            return self._na_value

        i8 = self.asi8
        try:
            # quick check
            if len(i8) and self.is_monotonic:
                if i8[-1] != iNaT:
                    return self._box_func(i8[-1])

            if self.hasnans:
                if skipna:
                    max_stamp = self[~self._isnan].asi8.max()
                else:
                    return self._na_value
            else:
                max_stamp = i8.max()
            return self._box_func(max_stamp)
        except ValueError:
            return self._na_value

    def argmax(self, axis=None, skipna=True, *args, **kwargs):
        """
        Returns the indices of the maximum values along an axis.

        See `numpy.ndarray.argmax` for more information on the
        `axis` parameter.

        See Also
        --------
        numpy.ndarray.argmax
        """
        nv.validate_argmax(args, kwargs)
        nv.validate_minmax_axis(axis)

        i8 = self.asi8
        if self.hasnans:
            mask = self._isnan
            if mask.all() or not skipna:
                return -1
            i8 = i8.copy()
            i8[mask] = 0
        return i8.argmax()

    # --------------------------------------------------------------------
    # Rendering Methods

    def _format_with_header(self, header, na_rep="NaT", **kwargs):
        return header + list(self._format_native_types(na_rep, **kwargs))

    @property
    def _formatter_func(self):
        raise AbstractMethodError(self)

    def _format_attrs(self):
        """
        Return a list of tuples of the (attr,formatted_value).
        """
        attrs = super()._format_attrs()
        for attrib in self._attributes:
            if attrib == "freq":
                freq = self.freqstr
                if freq is not None:
                    freq = repr(freq)
                attrs.append(("freq", freq))
        return attrs

    # --------------------------------------------------------------------

    def _convert_scalar_indexer(self, key, kind=None):
        """
        We don't allow integer or float indexing on datetime-like when using
        loc.

        Parameters
        ----------
        key : label of the slice bound
        kind : {'loc', 'getitem', 'iloc'} or None
        """

        assert kind in ["loc", "getitem", "iloc", None]

        # we don't allow integer/float indexing for loc
        # we don't allow float indexing for ix/getitem
        if is_scalar(key):
            is_int = is_integer(key)
            is_flt = is_float(key)
            if kind in ["loc"] and (is_int or is_flt):
                self._invalid_indexer("index", key)
            elif kind in ["getitem"] and is_flt:
                self._invalid_indexer("index", key)

        return super()._convert_scalar_indexer(key, kind=kind)

    __add__ = make_wrapped_arith_op("__add__")
    __radd__ = make_wrapped_arith_op("__radd__")
    __sub__ = make_wrapped_arith_op("__sub__")
    __rsub__ = make_wrapped_arith_op("__rsub__")
    __pow__ = make_wrapped_arith_op("__pow__")
    __rpow__ = make_wrapped_arith_op("__rpow__")
    __mul__ = make_wrapped_arith_op("__mul__")
    __rmul__ = make_wrapped_arith_op("__rmul__")
    __floordiv__ = make_wrapped_arith_op("__floordiv__")
    __rfloordiv__ = make_wrapped_arith_op("__rfloordiv__")
    __mod__ = make_wrapped_arith_op("__mod__")
    __rmod__ = make_wrapped_arith_op("__rmod__")
    __divmod__ = make_wrapped_arith_op("__divmod__")
    __rdivmod__ = make_wrapped_arith_op("__rdivmod__")
    __truediv__ = make_wrapped_arith_op("__truediv__")
    __rtruediv__ = make_wrapped_arith_op("__rtruediv__")

    def isin(self, values, level=None):
        """
        Compute boolean array of whether each index value is found in the
        passed set of values.

        Parameters
        ----------
        values : set or sequence of values

        Returns
        -------
        is_contained : ndarray (boolean dtype)
        """
        if level is not None:
            self._validate_index_level(level)

        if not isinstance(values, type(self)):
            try:
                values = type(self)(values)
            except ValueError:
                return self.astype(object).isin(values)

        return algorithms.isin(self.asi8, values.asi8)

    @Appender(_index_shared_docs["where"] % _index_doc_kwargs)
    def where(self, cond, other=None):
        values = self.view("i8")

        if is_scalar(other) and isna(other):
            other = NaT.value

        else:
            # Do type inference if necessary up front
            # e.g. we passed PeriodIndex.values and got an ndarray of Periods
            other = Index(other)

            if is_categorical_dtype(other):
                # e.g. we have a Categorical holding self.dtype
                if needs_i8_conversion(other.categories):
                    other = other._internal_get_values()

            if not is_dtype_equal(self.dtype, other.dtype):
                raise TypeError(f"Where requires matching dtype, not {other.dtype}")

            other = other.view("i8")

        result = np.where(cond, values, other).astype("i8")
        return self._shallow_copy(result)

    def _summary(self, name=None):
        """
        Return a summarized representation.

        Parameters
        ----------
        name : str
            Name to use in the summary representation.

        Returns
        -------
        str
            Summarized representation of the index.
        """
        formatter = self._formatter_func
        if len(self) > 0:
            index_summary = f", {formatter(self[0])} to {formatter(self[-1])}"
        else:
            index_summary = ""

        if name is None:
            name = type(self).__name__
        result = f"{name}: {len(self)} entries{index_summary}"
        if self.freq:
            result += f"\nFreq: {self.freqstr}"

        # display as values, not quoted
        result = result.replace("'", "")
        return result

    def _concat_same_dtype(self, to_concat, name):
        """
        Concatenate to_concat which has the same class.
        """

        # do not pass tz to set because tzlocal cannot be hashed
        if len({str(x.dtype) for x in to_concat}) != 1:
            raise ValueError("to_concat must have the same tz")

        new_data = type(self._data)._concat_same_type(to_concat)

        if not is_period_dtype(self.dtype):
            # GH 3232: If the concat result is evenly spaced, we can retain the
            # original frequency
            is_diff_evenly_spaced = len(unique_deltas(new_data.asi8)) == 1
            if is_diff_evenly_spaced:
                new_data._freq = self.freq

        return self._simple_new(new_data, name=name)

    def shift(self, periods=1, freq=None):
        """
        Shift index by desired number of time frequency increments.

        This method is for shifting the values of datetime-like indexes
        by a specified time increment a given number of times.

        Parameters
        ----------
        periods : int, default 1
            Number of periods (or increments) to shift by,
            can be positive or negative.

            .. versionchanged:: 0.24.0

        freq : pandas.DateOffset, pandas.Timedelta or string, optional
            Frequency increment to shift by.
            If None, the index is shifted by its own `freq` attribute.
            Offset aliases are valid strings, e.g., 'D', 'W', 'M' etc.

        Returns
        -------
        pandas.DatetimeIndex
            Shifted index.

        See Also
        --------
        Index.shift : Shift values of Index.
        PeriodIndex.shift : Shift values of PeriodIndex.
        """
        result = self._data._time_shift(periods, freq=freq)
        return type(self)(result, name=self.name)

    # --------------------------------------------------------------------
    # List-like Methods

    def delete(self, loc):
        new_i8s = np.delete(self.asi8, loc)

        freq = None
        if is_period_dtype(self):
            freq = self.freq
        elif is_integer(loc):
            if loc in (0, -len(self), -1, len(self) - 1):
                freq = self.freq
        else:
            if is_list_like(loc):
                loc = lib.maybe_indices_to_slice(ensure_int64(np.array(loc)), len(self))
            if isinstance(loc, slice) and loc.step in (1, None):
                if loc.start in (0, None) or loc.stop in (len(self), None):
                    freq = self.freq

        return self._shallow_copy(new_i8s, freq=freq)


class DatetimeTimedeltaMixin(DatetimeIndexOpsMixin, Int64Index):
    """
    Mixin class for methods shared by DatetimeIndex and TimedeltaIndex,
    but not PeriodIndex
    """

    # Compat for frequency inference, see GH#23789
    _is_monotonic_increasing = Index.is_monotonic_increasing
    _is_monotonic_decreasing = Index.is_monotonic_decreasing
    _is_unique = Index.is_unique

    def _set_freq(self, freq):
        """
        Set the _freq attribute on our underlying DatetimeArray.

        Parameters
        ----------
        freq : DateOffset, None, or "infer"
        """
        # GH#29843
        if freq is None:
            # Always valid
            pass
        elif len(self) == 0 and isinstance(freq, DateOffset):
            # Always valid.  In the TimedeltaIndex case, we assume this
            #  is a Tick offset.
            pass
        else:
            # As an internal method, we can ensure this assertion always holds
            assert freq == "infer"
            freq = to_offset(self.inferred_freq)

        self._data._freq = freq

    def _shallow_copy(self, values=None, **kwargs):
        if values is None:
            values = self._data
        if isinstance(values, type(self)):
            values = values._data

        attributes = self._get_attributes_dict()

        if "freq" not in kwargs and self.freq is not None:
            if isinstance(values, (DatetimeArray, TimedeltaArray)):
                if values.freq is None:
                    del attributes["freq"]

        attributes.update(kwargs)
        return self._simple_new(values, **attributes)

    # --------------------------------------------------------------------
    # Set Operation Methods

    @Appender(Index.difference.__doc__)
    def difference(self, other, sort=None):
        new_idx = super().difference(other, sort=sort)
        new_idx._set_freq(None)
        return new_idx

    def intersection(self, other, sort=False):
        """
        Specialized intersection for DatetimeIndex/TimedeltaIndex.

        May be much faster than Index.intersection

        Parameters
        ----------
        other : Same type as self or array-like
        sort : False or None, default False
            Sort the resulting index if possible.

            .. versionadded:: 0.24.0

            .. versionchanged:: 0.24.1

               Changed the default to ``False`` to match the behaviour
               from before 0.24.0.

            .. versionchanged:: 0.25.0

               The `sort` keyword is added

        Returns
        -------
        y : Index or same type as self
        """
        self._validate_sort_keyword(sort)
        self._assert_can_do_setop(other)

        if self.equals(other):
            return self._get_reconciled_name_object(other)

        if len(self) == 0:
            return self.copy()
        if len(other) == 0:
            return other.copy()

        if not isinstance(other, type(self)):
            result = Index.intersection(self, other, sort=sort)
            if isinstance(result, type(self)):
                if result.freq is None:
                    result._set_freq("infer")
            return result

        elif (
            other.freq is None
            or self.freq is None
            or other.freq != self.freq
            or not other.freq.is_anchored()
            or (not self.is_monotonic or not other.is_monotonic)
        ):
            result = Index.intersection(self, other, sort=sort)

            # Invalidate the freq of `result`, which may not be correct at
            # this point, depending on the values.

            result._set_freq(None)
            result = self._shallow_copy(
                result._data, name=result.name, dtype=result.dtype, freq=None
            )
            if result.freq is None:
                result._set_freq("infer")
            return result

        # to make our life easier, "sort" the two ranges
        if self[0] <= other[0]:
            left, right = self, other
        else:
            left, right = other, self

        # after sorting, the intersection always starts with the right index
        # and ends with the index of which the last elements is smallest
        end = min(left[-1], right[-1])
        start = right[0]

        if end < start:
            return type(self)(data=[])
        else:
            lslice = slice(*left.slice_locs(start, end))
            left_chunk = left.values[lslice]
            return self._shallow_copy(left_chunk)

    def _can_fast_union(self, other) -> bool:
        if not isinstance(other, type(self)):
            return False

        freq = self.freq

        if freq is None or freq != other.freq:
            return False

        if not self.is_monotonic or not other.is_monotonic:
            return False

        if len(self) == 0 or len(other) == 0:
            return True

        # to make our life easier, "sort" the two ranges
        if self[0] <= other[0]:
            left, right = self, other
        else:
            left, right = other, self

        right_start = right[0]
        left_end = left[-1]

        # Only need to "adjoin", not overlap
        try:
            return (right_start == left_end + freq) or right_start in left
        except ValueError:
            # if we are comparing a freq that does not propagate timezones
            # this will raise
            return False

    def _fast_union(self, other, sort=None):
        if len(other) == 0:
            return self.view(type(self))

        if len(self) == 0:
            return other.view(type(self))

        # to make our life easier, "sort" the two ranges
        if self[0] <= other[0]:
            left, right = self, other
        elif sort is False:
            # TDIs are not in the "correct" order and we don't want
            #  to sort but want to remove overlaps
            left, right = self, other
            left_start = left[0]
            loc = right.searchsorted(left_start, side="left")
            right_chunk = right.values[:loc]
            dates = concat_compat((left.values, right_chunk))
            return self._shallow_copy(dates)
        else:
            left, right = other, self

        left_end = left[-1]
        right_end = right[-1]

        # concatenate
        if left_end < right_end:
            loc = right.searchsorted(left_end, side="right")
            right_chunk = right.values[loc:]
            dates = concat_compat((left.values, right_chunk))
            return self._shallow_copy(dates)
        else:
            return left

    def _union(self, other, sort):
        if not len(other) or self.equals(other) or not len(self):
            return super()._union(other, sort=sort)

        # We are called by `union`, which is responsible for this validation
        assert isinstance(other, type(self))

        this, other = self._maybe_utc_convert(other)

        if this._can_fast_union(other):
            return this._fast_union(other, sort=sort)
        else:
            result = Index._union(this, other, sort=sort)
            if isinstance(result, type(self)):
                assert result._data.dtype == this.dtype
                if result.freq is None:
                    result._set_freq("infer")
            return result

    # --------------------------------------------------------------------
    # Join Methods
    _join_precedence = 10

    _inner_indexer = _join_i8_wrapper(libjoin.inner_join_indexer)
    _outer_indexer = _join_i8_wrapper(libjoin.outer_join_indexer)
    _left_indexer = _join_i8_wrapper(libjoin.left_join_indexer)
    _left_indexer_unique = _join_i8_wrapper(
        libjoin.left_join_indexer_unique, with_indexers=False
    )

    def join(
        self, other, how: str = "left", level=None, return_indexers=False, sort=False
    ):
        """
        See Index.join
        """
        if self._is_convertible_to_index_for_join(other):
            try:
                other = type(self)(other)
            except (TypeError, ValueError):
                pass

        this, other = self._maybe_utc_convert(other)
        return Index.join(
            this,
            other,
            how=how,
            level=level,
            return_indexers=return_indexers,
            sort=sort,
        )

    def _maybe_utc_convert(self, other):
        this = self
        if not hasattr(self, "tz"):
            return this, other

        if isinstance(other, type(self)):
            if self.tz is not None:
                if other.tz is None:
                    raise TypeError("Cannot join tz-naive with tz-aware DatetimeIndex")
            elif other.tz is not None:
                raise TypeError("Cannot join tz-naive with tz-aware DatetimeIndex")

            if not timezones.tz_compare(self.tz, other.tz):
                this = self.tz_convert("UTC")
                other = other.tz_convert("UTC")
        return this, other

    @classmethod
    def _is_convertible_to_index_for_join(cls, other: Index) -> bool:
        """
        return a boolean whether I can attempt conversion to a
        DatetimeIndex/TimedeltaIndex
        """
        if isinstance(other, cls):
            return False
        elif len(other) > 0 and other.inferred_type not in (
            "floating",
            "mixed-integer",
            "integer",
            "integer-na",
            "mixed-integer-float",
            "mixed",
        ):
            return True
        return False

    def _wrap_joined_index(self, joined, other):
        name = get_op_result_name(self, other)
        if self._can_fast_union(other):
            joined = self._shallow_copy(joined)
            joined.name = name
            return joined
        else:
            kwargs = {}
            if hasattr(self, "tz"):
                kwargs["tz"] = getattr(other, "tz", None)
            return self._simple_new(joined, name, **kwargs)

    # --------------------------------------------------------------------
    # List-Like Methods

    def insert(self, loc, item):
        """
        Make new Index inserting new item at location
        Parameters
        ----------
        loc : int
        item : object
            if not either a Python datetime or a numpy integer-like, returned
            Index dtype will be object rather than datetime.
        Returns
        -------
        new_index : Index
        """
        if isinstance(item, self._data._recognized_scalars):
            item = self._data._scalar_type(item)
        elif is_valid_nat_for_dtype(item, self.dtype):
            # GH 18295
            item = self._na_value
        elif is_scalar(item) and isna(item):
            raise TypeError(
                f"cannot insert {type(self).__name__} with incompatible label"
            )

        freq = None
        if isinstance(item, self._data._scalar_type) or item is NaT:
            self._data._check_compatible_with(item, setitem=True)

            # check freq can be preserved on edge cases
            if self.size and self.freq is not None:
                if item is NaT:
                    pass
                elif (loc == 0 or loc == -len(self)) and item + self.freq == self[0]:
                    freq = self.freq
                elif (loc == len(self)) and item - self.freq == self[-1]:
                    freq = self.freq
            item = item.asm8

        try:
            new_i8s = np.concatenate(
                (self[:loc].asi8, [item.view(np.int64)], self[loc:].asi8)
            )
            return self._shallow_copy(new_i8s, freq=freq)
        except (AttributeError, TypeError):

            # fall back to object index
            if isinstance(item, str):
                return self.astype(object).insert(loc, item)
            raise TypeError(
                f"cannot insert {type(self).__name__} with incompatible label"
            )


class DatetimelikeDelegateMixin(PandasDelegate):
    """
    Delegation mechanism, specific for Datetime, Timedelta, and Period types.

    Functionality is delegated from the Index class to an Array class. A
    few things can be customized

    * _delegated_methods, delegated_properties : List
        The list of property / method names being delagated.
    * raw_methods : Set
        The set of methods whose results should should *not* be
        boxed in an index, after being returned from the array
    * raw_properties : Set
        The set of properties whose results should should *not* be
        boxed in an index, after being returned from the array
    """

    # raw_methods : dispatch methods that shouldn't be boxed in an Index
    _raw_methods: Set[str] = set()
    # raw_properties : dispatch properties that shouldn't be boxed in an Index
    _raw_properties: Set[str] = set()
    _data: ExtensionArray

    def _delegate_property_get(self, name, *args, **kwargs):
        result = getattr(self._data, name)
        if name not in self._raw_properties:
            result = Index(result, name=self.name)
        return result

    def _delegate_property_set(self, name, value, *args, **kwargs):
        setattr(self._data, name, value)

    def _delegate_method(self, name, *args, **kwargs):
        result = operator.methodcaller(name, *args, **kwargs)(self._data)
        if name not in self._raw_methods:
            result = Index(result, name=self.name)
        return result
