from decimal import Decimal

import numpy as np
import pytest

from pandas._libs.missing import (
    NA,
    is_matching_na,
)
from pandas.compat import pa_version_under16p0
import pandas.util._test_decorators as td

import pandas as pd
from pandas import Index
import pandas._testing as tm


class TestGetIndexer:
    @pytest.mark.parametrize(
        "method,expected",
        [
            ("pad", np.array([-1, 0, 1, 1], dtype=np.intp)),
            ("backfill", np.array([0, 0, 1, -1], dtype=np.intp)),
        ],
    )
    def test_get_indexer_strings(self, method, expected):
        index = Index(["b", "c"])
        actual = index.get_indexer(["a", "b", "c", "d"], method=method)

        tm.assert_numpy_array_equal(actual, expected)

    def test_get_indexer_strings_raises(self, using_infer_string):
        index = Index(["b", "c"])

        if using_infer_string:
            import pyarrow as pa

            msg = "has no kernel"
            with pytest.raises(pa.lib.ArrowNotImplementedError, match=msg):
                index.get_indexer(["a", "b", "c", "d"], method="nearest")

            with pytest.raises(pa.lib.ArrowNotImplementedError, match=msg):
                index.get_indexer(["a", "b", "c", "d"], method="pad", tolerance=2)

            with pytest.raises(pa.lib.ArrowNotImplementedError, match=msg):
                index.get_indexer(
                    ["a", "b", "c", "d"], method="pad", tolerance=[2, 2, 2, 2]
                )

        else:
            msg = r"unsupported operand type\(s\) for -: 'str' and 'str'"
            with pytest.raises(TypeError, match=msg):
                index.get_indexer(["a", "b", "c", "d"], method="nearest")

            with pytest.raises(TypeError, match=msg):
                index.get_indexer(["a", "b", "c", "d"], method="pad", tolerance=2)

            with pytest.raises(TypeError, match=msg):
                index.get_indexer(
                    ["a", "b", "c", "d"], method="pad", tolerance=[2, 2, 2, 2]
                )

    def test_get_indexer_with_NA_values(
        self, unique_nulls_fixture, unique_nulls_fixture2
    ):
        # GH#22332
        # check pairwise, that no pair of na values
        # is mangled
        if unique_nulls_fixture is unique_nulls_fixture2:
            return  # skip it, values are not unique
        arr = np.array([unique_nulls_fixture, unique_nulls_fixture2], dtype=object)
        index = Index(arr, dtype=object)
        result = index.get_indexer(
            Index(
                [unique_nulls_fixture, unique_nulls_fixture2, "Unknown"], dtype=object
            )
        )
        expected = np.array([0, 1, -1], dtype=np.intp)
        tm.assert_numpy_array_equal(result, expected)


class TestGetIndexerNonUnique:
    def test_get_indexer_non_unique_nas(
        self, nulls_fixture, request, using_infer_string
    ):
        # even though this isn't non-unique, this should still work
        if using_infer_string and (nulls_fixture is None or nulls_fixture is NA):
            request.applymarker(pytest.mark.xfail(reason="NAs are cast to NaN"))
        index = Index(["a", "b", nulls_fixture])
        indexer, missing = index.get_indexer_non_unique([nulls_fixture])

        expected_indexer = np.array([2], dtype=np.intp)
        expected_missing = np.array([], dtype=np.intp)
        tm.assert_numpy_array_equal(indexer, expected_indexer)
        tm.assert_numpy_array_equal(missing, expected_missing)

        # actually non-unique
        index = Index(["a", nulls_fixture, "b", nulls_fixture])
        indexer, missing = index.get_indexer_non_unique([nulls_fixture])

        expected_indexer = np.array([1, 3], dtype=np.intp)
        tm.assert_numpy_array_equal(indexer, expected_indexer)
        tm.assert_numpy_array_equal(missing, expected_missing)

        # matching-but-not-identical nans
        if is_matching_na(nulls_fixture, float("NaN")):
            index = Index(["a", float("NaN"), "b", float("NaN")])
            match_but_not_identical = True
        elif is_matching_na(nulls_fixture, Decimal("NaN")):
            index = Index(["a", Decimal("NaN"), "b", Decimal("NaN")])
            match_but_not_identical = True
        else:
            match_but_not_identical = False

        if match_but_not_identical:
            indexer, missing = index.get_indexer_non_unique([nulls_fixture])

            expected_indexer = np.array([1, 3], dtype=np.intp)
            tm.assert_numpy_array_equal(indexer, expected_indexer)
            tm.assert_numpy_array_equal(missing, expected_missing)

    @pytest.mark.filterwarnings("ignore:elementwise comp:DeprecationWarning")
    def test_get_indexer_non_unique_np_nats(self, np_nat_fixture, np_nat_fixture2):
        expected_missing = np.array([], dtype=np.intp)
        # matching-but-not-identical nats
        if is_matching_na(np_nat_fixture, np_nat_fixture2):
            # ensure nats are different objects
            index = Index(
                np.array(
                    ["2021-10-02", np_nat_fixture.copy(), np_nat_fixture2.copy()],
                    dtype=object,
                ),
                dtype=object,
            )
            # pass as index to prevent target from being casted to DatetimeIndex
            indexer, missing = index.get_indexer_non_unique(
                Index([np_nat_fixture], dtype=object)
            )
            expected_indexer = np.array([1, 2], dtype=np.intp)
            tm.assert_numpy_array_equal(indexer, expected_indexer)
            tm.assert_numpy_array_equal(missing, expected_missing)
        # dt64nat vs td64nat
        else:
            try:
                np_nat_fixture == np_nat_fixture2
            except (TypeError, OverflowError):
                # Numpy will raise on uncomparable types, like
                # np.datetime64('NaT', 'Y') and np.datetime64('NaT', 'ps')
                # https://github.com/numpy/numpy/issues/22762
                return
            index = Index(
                np.array(
                    [
                        "2021-10-02",
                        np_nat_fixture,
                        np_nat_fixture2,
                        np_nat_fixture,
                        np_nat_fixture2,
                    ],
                    dtype=object,
                ),
                dtype=object,
            )
            # pass as index to prevent target from being casted to DatetimeIndex
            indexer, missing = index.get_indexer_non_unique(
                Index([np_nat_fixture], dtype=object)
            )
            expected_indexer = np.array([1, 3], dtype=np.intp)
            tm.assert_numpy_array_equal(indexer, expected_indexer)
            tm.assert_numpy_array_equal(missing, expected_missing)


class TestSliceLocs:
    @pytest.mark.parametrize(
        "dtype",
        [
            "object",
            pytest.param("string[pyarrow_numpy]", marks=td.skip_if_no("pyarrow")),
        ],
    )
    @pytest.mark.parametrize(
        "in_slice,expected",
        [
            # error: Slice index must be an integer or None
            (pd.IndexSlice[::-1], "yxdcb"),
            (pd.IndexSlice["b":"y":-1], ""),  # type: ignore[misc]
            (pd.IndexSlice["b"::-1], "b"),  # type: ignore[misc]
            (pd.IndexSlice[:"b":-1], "yxdcb"),  # type: ignore[misc]
            (pd.IndexSlice[:"y":-1], "y"),  # type: ignore[misc]
            (pd.IndexSlice["y"::-1], "yxdcb"),  # type: ignore[misc]
            (pd.IndexSlice["y"::-4], "yb"),  # type: ignore[misc]
            # absent labels
            (pd.IndexSlice[:"a":-1], "yxdcb"),  # type: ignore[misc]
            (pd.IndexSlice[:"a":-2], "ydb"),  # type: ignore[misc]
            (pd.IndexSlice["z"::-1], "yxdcb"),  # type: ignore[misc]
            (pd.IndexSlice["z"::-3], "yc"),  # type: ignore[misc]
            (pd.IndexSlice["m"::-1], "dcb"),  # type: ignore[misc]
            (pd.IndexSlice[:"m":-1], "yx"),  # type: ignore[misc]
            (pd.IndexSlice["a":"a":-1], ""),  # type: ignore[misc]
            (pd.IndexSlice["z":"z":-1], ""),  # type: ignore[misc]
            (pd.IndexSlice["m":"m":-1], ""),  # type: ignore[misc]
        ],
    )
    def test_slice_locs_negative_step(self, in_slice, expected, dtype, request):
        if (
            not pa_version_under16p0
            and dtype == "string[pyarrow_numpy]"
            and in_slice == slice("a", "a", -1)
        ):
            request.applymarker(
                pytest.mark.xfail(reason="https://github.com/apache/arrow/issues/40642")
            )

        index = Index(list("bcdxy"), dtype=dtype)

        s_start, s_stop = index.slice_locs(in_slice.start, in_slice.stop, in_slice.step)
        result = index[s_start : s_stop : in_slice.step]
        expected = Index(list(expected), dtype=dtype)
        tm.assert_index_equal(result, expected)

    @td.skip_if_no("pyarrow")
    def test_slice_locs_negative_step_oob(self):
        index = Index(list("bcdxy"), dtype="string[pyarrow_numpy]")

        result = index[-10:5:1]
        tm.assert_index_equal(result, index)

        result = index[4:-10:-1]
        expected = Index(list("yxdcb"), dtype="string[pyarrow_numpy]")
        tm.assert_index_equal(result, expected)

    def test_slice_locs_dup(self):
        index = Index(["a", "a", "b", "c", "d", "d"])
        assert index.slice_locs("a", "d") == (0, 6)
        assert index.slice_locs(end="d") == (0, 6)
        assert index.slice_locs("a", "c") == (0, 4)
        assert index.slice_locs("b", "d") == (2, 6)

        index2 = index[::-1]
        assert index2.slice_locs("d", "a") == (0, 6)
        assert index2.slice_locs(end="a") == (0, 6)
        assert index2.slice_locs("d", "b") == (0, 4)
        assert index2.slice_locs("c", "a") == (2, 6)
