import bisect
import copy
import itertools
import operator
import os
import pickle
import string
import sys
import tempfile

import pytest

import numpy as np
from numpy._core.tests._natype import pd_NA
from numpy.dtypes import StringDType
from numpy.testing import assert_array_equal


def random_unicode_string_list():
    """Returns an array of 10 100-character strings containing random text"""
    chars = list(string.ascii_letters + string.digits)
    chars = np.array(chars, dtype="U1")
    ret = np.random.choice(chars, size=100 * 10, replace=True)
    return ret.view("U100")


def get_dtype(na_object, coerce=True):
    """Helper to work around pd_NA boolean behavior"""
    # explicit is check for pd_NA because != with pd_NA returns pd_NA
    if na_object is pd_NA or na_object != "unset":
        return np.dtypes.StringDType(na_object=na_object, coerce=coerce)
    else:
        return np.dtypes.StringDType(coerce=coerce)


@pytest.fixture(params=[True, False])
def coerce(request):
    """Coerce input to strings or raise an error for non-string input"""
    return request.param


@pytest.fixture(
    params=["unset", None, pd_NA, np.nan, float("nan"), "__nan__"],
    ids=["unset", "None", "pandas.NA", "np.nan", "float('nan')", "string nan"],
)
def na_object(request):
    """Possible values for the missing data sentinel"""
    return request.param


@pytest.fixture()
def dtype(na_object, coerce):
    """Cartesian project of missing data sentinel and string coercion options"""
    return get_dtype(na_object, coerce)

@pytest.fixture
def string_list():
    """Mix of short and long strings, some with unicode, some without"""
    return ["abc", "def", "ghi" * 10, "A¢☃€ 😊" * 100, "Abc" * 1000, "DEF"]


@pytest.fixture(params=[True, False])
def coerce2(request):
    """Second copy of the coerce fixture for tests that need two instances"""
    return request.param


@pytest.fixture(
    params=["unset", None, pd_NA, np.nan, float("nan"), "__nan__"],
    ids=["unset", "None", "pandas.NA", "np.nan", "float('nan')", "string nan"],
)
def na_object2(request):
    """Second copy of the na_object fixture for tests that need two instances"""
    return request.param


@pytest.fixture()
def dtype2(na_object2, coerce2):
    """Second copy of the dtype fixture for tests that need two instances"""
    # explicit is check for pd_NA because != with pd_NA returns pd_NA
    if na_object2 is pd_NA or na_object2 != "unset":
        return StringDType(na_object=na_object2, coerce=coerce2)
    else:
        return StringDType(coerce=coerce2)


def test_dtype_creation():
    hashes = set()
    dt = StringDType()
    assert not hasattr(dt, "na_object") and dt.coerce is True
    hashes.add(hash(dt))

    dt = StringDType(na_object=None)
    assert dt.na_object is None and dt.coerce is True
    hashes.add(hash(dt))

    dt = StringDType(coerce=False)
    assert not hasattr(dt, "na_object") and dt.coerce is False
    hashes.add(hash(dt))

    dt = StringDType(na_object=None, coerce=False)
    assert dt.na_object is None and dt.coerce is False
    hashes.add(hash(dt))

    assert len(hashes) == 4

    dt = np.dtype("T")
    assert dt == StringDType()
    assert dt.kind == "T"
    assert dt.char == "T"

    hashes.add(hash(dt))
    assert len(hashes) == 4


def test_dtype_equality(dtype):
    assert dtype == dtype
    for ch in "SU":
        assert dtype != np.dtype(ch)
        assert dtype != np.dtype(f"{ch}8")


def test_dtype_repr(dtype):
    if not hasattr(dtype, "na_object") and dtype.coerce:
        assert repr(dtype) == "StringDType()"
    elif dtype.coerce:
        assert repr(dtype) == f"StringDType(na_object={dtype.na_object!r})"
    elif not hasattr(dtype, "na_object"):
        assert repr(dtype) == "StringDType(coerce=False)"
    else:
        assert (
            repr(dtype)
            == f"StringDType(na_object={dtype.na_object!r}, coerce=False)"
        )


def test_create_with_na(dtype):
    if not hasattr(dtype, "na_object"):
        pytest.skip("does not have an na object")
    na_val = dtype.na_object
    string_list = ["hello", na_val, "world"]
    arr = np.array(string_list, dtype=dtype)
    assert str(arr) == "[" + " ".join([repr(s) for s in string_list]) + "]"
    assert arr[1] is dtype.na_object


@pytest.mark.parametrize("i", list(range(5)))
def test_set_replace_na(i):
    # Test strings of various lengths can be set to NaN and then replaced.
    s_empty = ""
    s_short = "0123456789"
    s_medium = "abcdefghijklmnopqrstuvwxyz"
    s_long = "-=+" * 100
    strings = [s_medium, s_empty, s_short, s_medium, s_long]
    a = np.array(strings, StringDType(na_object=np.nan))
    for s in [a[i], s_medium + s_short, s_short, s_empty, s_long]:
        a[i] = np.nan
        assert np.isnan(a[i])
        a[i] = s
        assert a[i] == s
        assert_array_equal(a, strings[:i] + [s] + strings[i + 1:])


def test_null_roundtripping():
    data = ["hello\0world", "ABC\0DEF\0\0"]
    arr = np.array(data, dtype="T")
    assert data[0] == arr[0]
    assert data[1] == arr[1]


@pytest.mark.parametrize(
    "op, pyop",
    [
        (np.equal, operator.eq),
        (np.not_equal, operator.ne),
        (np.greater, operator.gt),
        (np.greater_equal, operator.ge),
        (np.less, operator.lt),
        (np.less_equal, operator.le),
    ],
)
def test_embedded_null_comparisons(op, pyop):
    lhs = ["a\0b", "a\0b", "a\0c", "\0b", "long\0b"]
    rhs = ["a\0c", "a\0b", "a\0b", "\0a", "long\0c"]

    expected = [pyop(left, right) for left, right in zip(lhs, rhs)]
    result = op(np.array(lhs, dtype="T"), np.array(rhs, dtype="T"))

    assert result.tolist() == expected


def test_embedded_null_sorting_and_search():
    values = [
        "a\0c",
        "a\0b",
        "a",
        "\0b",
        "\0a",
        "long prefix\0c",
        "long prefix\0b",
    ]
    expected_sorted = sorted(values)

    arr = np.array(values, dtype="T")
    assert np.sort(arr).tolist() == expected_sorted
    assert arr[np.argsort(arr)].tolist() == expected_sorted
    assert np.minimum(arr[:2], arr[1::-1]).tolist() == ["a\0b", "a\0b"]
    assert np.maximum(arr[:2], arr[1::-1]).tolist() == ["a\0c", "a\0c"]

    haystack = np.array(expected_sorted, dtype="T")
    needles = ["\0b", "a\0c", "long prefix\0b"]
    expected = [bisect.bisect_left(expected_sorted, needle) for needle in needles]
    result = np.searchsorted(haystack, np.array(needles, dtype="T"))
    assert result.tolist() == expected


@pytest.mark.parametrize("dtype", [object, "U20", "S20", "V20"])
def test_embedded_null_string_like_casts(dtype):
    strings = ["a\0b", "\0leading", "multi\0null\0inside"]
    arr = np.array(strings, dtype="T")
    roundtripped = arr.astype(dtype).astype("T")

    assert roundtripped.tolist() == strings


def test_string_too_large_error():
    arr = np.array(["a", "b", "c"], dtype=StringDType())
    with pytest.raises(OverflowError):
        arr * (sys.maxsize + 1)


@pytest.mark.parametrize(
    "data",
    [
        ["abc", "def", "ghi"],
        ["🤣", "📵", "😰"],
        ["🚜", "🙃", "😾"],
        ["😹", "🚠", "🚌"],
    ],
)
def test_array_creation_utf8(dtype, data):
    arr = np.array(data, dtype=dtype)
    assert str(arr) == "[" + " ".join(["'" + str(d) + "'" for d in data]) + "]"
    assert arr.dtype == dtype


@pytest.mark.parametrize(
    "data",
    [
        [1, 2, 3],
        [b"abc", b"def", b"ghi"],
        [object, object, object],
    ],
)
def test_scalars_string_conversion(data, dtype):
    try:
        str_vals = [str(d.decode('utf-8')) for d in data]
    except AttributeError:
        str_vals = [str(d) for d in data]
    if dtype.coerce:
        assert_array_equal(
            np.array(data, dtype=dtype),
            np.array(str_vals, dtype=dtype),
        )
    else:
        with pytest.raises(ValueError):
            np.array(data, dtype=dtype)


@pytest.mark.parametrize(
    ("strings"),
    [
        ["this", "is", "an", "array"],
        ["€", "", "😊"],
        ["A¢☃€ 😊", " A☃€¢😊", "☃€😊 A¢", "😊☃A¢ €"],
    ],
)
def test_self_casts(dtype, dtype2, strings):
    if hasattr(dtype, "na_object"):
        strings = strings + [dtype.na_object]
    elif hasattr(dtype2, "na_object"):
        strings = strings + [""]
    arr = np.array(strings, dtype=dtype)
    newarr = arr.astype(dtype2)

    if hasattr(dtype, "na_object") and not hasattr(dtype2, "na_object"):
        assert newarr[-1] == str(dtype.na_object)
        with pytest.raises(TypeError):
            arr.astype(dtype2, casting="safe")
    elif hasattr(dtype, "na_object") and hasattr(dtype2, "na_object"):
        assert newarr[-1] is dtype2.na_object
        arr.astype(dtype2, casting="safe")
    elif hasattr(dtype2, "na_object"):
        assert newarr[-1] == ""
        arr.astype(dtype2, casting="safe")
    else:
        arr.astype(dtype2, casting="safe")

    if hasattr(dtype, "na_object") and hasattr(dtype2, "na_object"):
        na1 = dtype.na_object
        na2 = dtype2.na_object
        if (na1 is not na2 and
             # check for pd_NA first because bool(pd_NA) is an error
             ((na1 is pd_NA or na2 is pd_NA) or
              # the second check is a NaN check, spelled this way
              # to avoid errors from math.isnan and np.isnan
              (na1 != na2 and not (na1 != na1 and na2 != na2)))):
            with pytest.raises(TypeError):
                arr[:-1] == newarr[:-1]
            return
    assert_array_equal(arr[:-1], newarr[:-1])


@pytest.mark.parametrize(
    ("strings"),
    [
        ["this", "is", "an", "array"],
        ["€", "", "😊"],
        ["A¢☃€ 😊", " A☃€¢😊", "☃€😊 A¢", "😊☃A¢ €"],
        ["short", "12345678"] * 1000,
    ],
)
class TestStringLikeCasts:
    def test_unicode_casts(self, dtype, strings):
        arr = np.array(strings, dtype=np.str_).astype(dtype)
        expected = np.array(strings, dtype=dtype)
        assert_array_equal(arr, expected)

        arr_as_U8 = expected.astype("U8")
        assert_array_equal(arr_as_U8, np.array(strings, dtype="U8"))
        assert_array_equal(arr_as_U8.astype(dtype), arr)
        arr_as_U3 = expected.astype("U3")
        assert_array_equal(arr_as_U3, np.array(strings, dtype="U3"))
        assert_array_equal(
            arr_as_U3.astype(dtype),
            np.array([s[:3] for s in strings], dtype=dtype),
        )

    def test_void_casts(self, dtype, strings):
        sarr = np.array(strings, dtype=dtype)
        utf8_bytes = [s.encode("utf-8") for s in strings]
        void_dtype = f"V{max(len(s) for s in utf8_bytes)}"
        varr = np.array(utf8_bytes, dtype=void_dtype)
        assert_array_equal(varr, sarr.astype(void_dtype))
        assert_array_equal(varr.astype(dtype), sarr)

    def test_bytes_casts(self, dtype, strings):
        sarr = np.array(strings, dtype=dtype)
        try:
            utf8_bytes = [s.encode("ascii") for s in strings]
            bytes_dtype = f"S{max(len(s) for s in utf8_bytes)}"
            barr = np.array(utf8_bytes, dtype=bytes_dtype)
            assert_array_equal(barr, sarr.astype(bytes_dtype))
            assert_array_equal(barr.astype(dtype), sarr)
            if dtype.coerce:
                barr = np.array(utf8_bytes, dtype=dtype)
                assert_array_equal(barr, sarr)
                barr = np.array(utf8_bytes, dtype="O")
                assert_array_equal(barr.astype(dtype), sarr)
            else:
                with pytest.raises(ValueError):
                    np.array(utf8_bytes, dtype=dtype)
        except UnicodeEncodeError:
            with pytest.raises(UnicodeEncodeError):
                sarr.astype("S20")


def test_additional_unicode_cast(dtype):
    string_list = random_unicode_string_list()
    arr = np.array(string_list, dtype=dtype)
    # test that this short-circuits correctly
    assert_array_equal(arr, arr.astype(arr.dtype))
    # tests the casts via the comparison promoter
    assert_array_equal(arr, arr.astype(string_list.dtype))


@pytest.mark.parametrize(
    "dtype",
    [
        "int64",
        "float16",
        "float32",
        "float64",
        "longdouble",
        "complex64",
        "complex128",
        "clongdouble",
    ],
)
@pytest.mark.parametrize(
    "invalid",
    ["", "spam", "1abc", "1.0abc", "\0", "1\0", "1\0abc"],
)
def test_invalid_numeric_casts_error(dtype, invalid):
    arr = np.array([invalid], dtype="T")

    with pytest.raises(ValueError):
        arr.astype(dtype)


def test_insert_scalar(dtype, string_list):
    """Test that inserting a scalar works."""
    arr = np.array(string_list, dtype=dtype)
    scalar_instance = "what"
    arr[1] = scalar_instance
    assert_array_equal(
        arr,
        np.array(string_list[:1] + ["what"] + string_list[2:], dtype=dtype),
    )


comparison_operators = [
    np.equal,
    np.not_equal,
    np.greater,
    np.greater_equal,
    np.less,
    np.less_equal,
]


@pytest.mark.parametrize("op", comparison_operators)
@pytest.mark.parametrize("o_dtype", [np.str_, object, StringDType()])
def test_comparisons(string_list, dtype, op, o_dtype):
    sarr = np.array(string_list, dtype=dtype)
    oarr = np.array(string_list, dtype=o_dtype)

    # test that comparison operators work
    res = op(sarr, sarr)
    ores = op(oarr, oarr)
    # test that promotion works as well
    orres = op(sarr, oarr)
    olres = op(oarr, sarr)

    assert_array_equal(res, ores)
    assert_array_equal(res, orres)
    assert_array_equal(res, olres)

    # test we get the correct answer for unequal length strings
    sarr2 = np.array([s + "2" for s in string_list], dtype=dtype)
    oarr2 = np.array([s + "2" for s in string_list], dtype=o_dtype)

    res = op(sarr, sarr2)
    ores = op(oarr, oarr2)
    olres = op(oarr, sarr2)
    orres = op(sarr, oarr2)

    assert_array_equal(res, ores)
    assert_array_equal(res, olres)
    assert_array_equal(res, orres)

    res = op(sarr2, sarr)
    ores = op(oarr2, oarr)
    olres = op(oarr2, sarr)
    orres = op(sarr2, oarr)

    assert_array_equal(res, ores)
    assert_array_equal(res, olres)
    assert_array_equal(res, orres)


def test_isnan(dtype, string_list):
    if not hasattr(dtype, "na_object"):
        pytest.skip("no na support")
    sarr = np.array(string_list + [dtype.na_object], dtype=dtype)
    is_nan = isinstance(dtype.na_object, float) and np.isnan(dtype.na_object)
    bool_errors = 0
    try:
        bool(dtype.na_object)
    except TypeError:
        bool_errors = 1
    if is_nan or bool_errors:
        # isnan is only true when na_object is a NaN
        assert_array_equal(
            np.isnan(sarr),
            np.array([0] * len(string_list) + [1], dtype=np.bool),
        )
    else:
        assert not np.any(np.isnan(sarr))


def test_pickle(dtype, string_list):
    arr = np.array(string_list, dtype=dtype)

    with tempfile.NamedTemporaryFile("wb", delete=False) as f:
        pickle.dump([arr, dtype], f)

    with open(f.name, "rb") as f:
        res = pickle.load(f)

    assert_array_equal(res[0], arr)
    assert res[1] == dtype

    os.remove(f.name)


def test_stdlib_copy(dtype, string_list):
    arr = np.array(string_list, dtype=dtype)

    assert_array_equal(copy.copy(arr), arr)
    assert_array_equal(copy.deepcopy(arr), arr)


@pytest.mark.parametrize(
    "strings",
    [
        ["left", "right", "leftovers", "righty", "up", "down"],
        [
            "left" * 10,
            "right" * 10,
            "leftovers" * 10,
            "righty" * 10,
            "up" * 10,
        ],
        ["🤣🤣", "🤣", "📵", "😰"],
        ["🚜", "🙃", "😾"],
        ["😹", "🚠", "🚌"],
        ["A¢☃€ 😊", " A☃€¢😊", "☃€😊 A¢", "😊☃A¢ €"],
    ],
)
def test_sort(dtype, strings):
    """Test that sorting matches python's internal sorting."""

    def test_sort(strings, arr_sorted):
        arr = np.array(strings, dtype=dtype)
        na_object = getattr(arr.dtype, "na_object", "")
        if na_object is None and None in strings:
            with pytest.raises(
                ValueError,
                match="Cannot compare null that is not a nan-like value",
            ):
                np.argsort(arr)
            argsorted = None
        elif na_object is pd_NA or na_object != '':
            argsorted = None
        else:
            argsorted = np.argsort(arr)
        np.random.default_rng().shuffle(arr)
        if na_object is None and None in strings:
            with pytest.raises(
                ValueError,
                match="Cannot compare null that is not a nan-like value",
            ):
                arr.sort()
        else:
            arr.sort()
            assert np.array_equal(arr, arr_sorted, equal_nan=True)
        if argsorted is not None:
            assert np.array_equal(argsorted, np.argsort(strings))

    # make a copy so we don't mutate the lists in the fixture
    strings = strings.copy()
    arr_sorted = np.array(sorted(strings), dtype=dtype)
    test_sort(strings, arr_sorted)

    if not hasattr(dtype, "na_object"):
        return

    # make sure NAs get sorted to the end of the array and string NAs get
    # sorted like normal strings
    strings.insert(0, dtype.na_object)
    strings.insert(2, dtype.na_object)
    # can't use append because doing that with NA converts
    # the result to object dtype
    if not isinstance(dtype.na_object, str):
        arr_sorted = np.array(
            arr_sorted.tolist() + [dtype.na_object, dtype.na_object],
            dtype=dtype,
        )
    else:
        arr_sorted = np.array(sorted(strings), dtype=dtype)

    test_sort(strings, arr_sorted)


def test_searchsorted_gh31533():
    n = 100_000
    # all > 15 bytes -> arena
    values = [f"{i:020d}" for i in range(n)]
    haystack = np.array(values, dtype="T")
    # a handful of needles -> tiny arena
    needle_values = values[:: n // 23]
    expected = np.searchsorted(
        np.array(values, dtype="U20"), np.array(needle_values, dtype="U20")
    )

    needles = np.array(needle_values, dtype="T")
    assert_array_equal(np.searchsorted(haystack, needles), expected)
    assert_array_equal(
        np.searchsorted(haystack, needles, sorter=np.arange(n)), expected
    )


@pytest.mark.parametrize(
    "strings",
    [
        ["A¢☃€ 😊", " A☃€¢😊", "☃€😊 A¢", "😊☃A¢ €"],
        ["A¢☃€ 😊", "", " ", " "],
        ["", "a", "😸", "ááðfáíóåéë"],
    ],
)
def test_nonzero(strings, na_object):
    dtype = get_dtype(na_object)
    arr = np.array(strings, dtype=dtype)
    is_nonzero = np.array(
        [i for i, item in enumerate(strings) if len(item) != 0])
    assert_array_equal(arr.nonzero()[0], is_nonzero)

    if na_object is not pd_NA and na_object == 'unset':
        return

    strings_with_na = np.array(strings + [na_object], dtype=dtype)
    is_nan = np.isnan(np.array([dtype.na_object], dtype=dtype))[0]

    if is_nan:
        assert strings_with_na.nonzero()[0][-1] == 4
    else:
        assert strings_with_na.nonzero()[0][-1] == 3

    # check that the casting to bool and nonzero give consistent results
    assert_array_equal(strings_with_na[strings_with_na.nonzero()],
                       strings_with_na[strings_with_na.astype(bool)])


def test_where(string_list, na_object):
    dtype = get_dtype(na_object)
    a = np.array(string_list, dtype=dtype)
    b = a[::-1]
    res = np.where([True, False, True, False, True, False], a, b)
    assert_array_equal(res, [a[0], b[1], a[2], b[3], a[4], b[5]])


def test_fancy_indexing(string_list):
    sarr = np.array(string_list, dtype="T")
    assert_array_equal(sarr, sarr[np.arange(sarr.shape[0])])

    inds = [
        [True, True],
        [0, 1],
        ...,
        np.array([0, 1], dtype='uint8'),
    ]

    lops = [
        ['a' * 25, 'b' * 25],
        ['', ''],
        ['hello', 'world'],
        ['hello', 'world' * 25],
    ]

    # see gh-27003 and gh-27053
    for ind in inds:
        for lop in lops:
            a = np.array(lop, dtype="T")
            assert_array_equal(a[ind], a)
            rop = ['d' * 25, 'e' * 25]
            for b in [rop, np.array(rop, dtype="T")]:
                a[ind] = b
                assert_array_equal(a, b)
                assert a[0] == 'd' * 25

    # see gh-29279
    data = [
        ["AAAAAAAAAAAAAAAAA"],
        ["BBBBBBBBBBBBBBBBBBBBBBBBBBBBB"],
        ["CCCCCCCCCCCCCCCCC"],
        ["DDDDDDDDDDDDDDDDD"],
    ]
    sarr = np.array(data, dtype=np.dtypes.StringDType())
    uarr = np.array(data, dtype="U30")
    for ind in [[0], [1], [2], [3], [[0, 0]], [[1, 1, 3]], [[1, 1]]]:
        assert_array_equal(sarr[ind], uarr[ind])


def test_flatiter_indexing():
    # see gh-29659
    arr = np.array(['hello', 'world'], dtype='T')
    arr.flat[:] = 9223372036854775
    assert_array_equal(arr, np.array([9223372036854775] * 2, dtype='T'))


def test_creation_functions():
    assert_array_equal(np.zeros(3, dtype="T"), ["", "", ""])
    assert_array_equal(np.empty(3, dtype="T"), ["", "", ""])

    assert np.zeros(3, dtype="T")[0] == ""
    assert np.empty(3, dtype="T")[0] == ""


def test_concatenate(string_list):
    sarr = np.array(string_list, dtype="T")
    sarr_cat = np.array(string_list + string_list, dtype="T")

    assert_array_equal(np.concatenate([sarr], axis=0), sarr)


def test_resize_method(string_list):
    sarr = np.array(string_list, dtype="T")
    sarr.resize(len(string_list) + 3)
    assert_array_equal(sarr, np.array(string_list + [''] * 3,  dtype="T"))


def test_create_with_copy_none(string_list):
    arr = np.array(string_list, dtype=StringDType())
    # create another stringdtype array with an arena that has a different
    # in-memory layout than the first array
    arr_rev = np.array(string_list[::-1], dtype=StringDType())

    # this should create a copy and the resulting array
    # shouldn't share an allocator or arena with arr_rev, despite
    # explicitly passing arr_rev.dtype
    arr_copy = np.array(arr, copy=None, dtype=arr_rev.dtype)
    np.testing.assert_array_equal(arr, arr_copy)
    assert arr_copy.base is None

    with pytest.raises(ValueError, match="Unable to avoid copy"):
        np.array(arr, copy=False, dtype=arr_rev.dtype)

    # because we're using arr's dtype instance, the view is safe
    arr_view = np.array(arr, copy=None, dtype=arr.dtype)
    np.testing.assert_array_equal(arr, arr)
    np.testing.assert_array_equal(arr_view[::-1], arr_rev)
    assert arr_view is arr


def test_astype_copy_false():
    orig_dt = StringDType()
    arr = np.array(["hello", "world"], dtype=StringDType())
    assert not arr.astype(StringDType(coerce=False), copy=False).dtype.coerce

    assert arr.astype(orig_dt, copy=False).dtype is orig_dt

@pytest.mark.parametrize(
    "strings",
    [
        ["left", "right", "leftovers", "righty", "up", "down"],
        ["🤣🤣", "🤣", "📵", "😰"],
        ["🚜", "🙃", "😾"],
        ["😹", "🚠", "🚌"],
        ["A¢☃€ 😊", " A☃€¢😊", "☃€😊 A¢", "😊☃A¢ €"],
    ],
)
def test_argmax(strings):
    """Test that argmax/argmin matches what python calculates."""
    arr = np.array(strings, dtype="T")
    assert np.argmax(arr) == strings.index(max(strings))
    assert np.argmin(arr) == strings.index(min(strings))


@pytest.mark.parametrize(
    "arrfunc,expected",
    [
        [np.sort, None],
        [np.nonzero, (np.array([], dtype=np.int_),)],
        [np.argmax, 0],
        [np.argmin, 0],
    ],
)
def test_arrfuncs_zeros(arrfunc, expected):
    arr = np.zeros(10, dtype="T")
    result = arrfunc(arr)
    if expected is None:
        expected = arr
    assert_array_equal(result, expected, strict=True)


@pytest.mark.parametrize(
    ("strings", "cast_answer", "any_answer", "all_answer"),
    [
        [["hello", "world"], [True, True], True, True],
        [["", ""], [False, False], False, False],
        [["hello", ""], [True, False], True, False],
        [["", "world"], [False, True], True, False],
    ],
)
def test_cast_to_bool(strings, cast_answer, any_answer, all_answer):
    sarr = np.array(strings, dtype="T")
    assert_array_equal(sarr.astype("bool"), cast_answer)

    assert np.any(sarr) == any_answer
    assert np.all(sarr) == all_answer


@pytest.mark.parametrize(
    ("strings", "cast_answer"),
    [
        [[True, True], ["True", "True"]],
        [[False, False], ["False", "False"]],
        [[True, False], ["True", "False"]],
        [[False, True], ["False", "True"]],
    ],
)
def test_cast_from_bool(strings, cast_answer):
    barr = np.array(strings, dtype=bool)
    assert_array_equal(barr.astype("T"), np.array(cast_answer, dtype="T"))


@pytest.mark.parametrize("bitsize", [8, 16, 32, 64])
@pytest.mark.parametrize("signed", [True, False])
def test_sized_integer_casts(bitsize, signed):
    idtype = f"int{bitsize}"
    if signed:
        inp = [-(2**p - 1) for p in reversed(range(bitsize - 1))]
        inp += [2**p - 1 for p in range(1, bitsize - 1)]
    else:
        idtype = "u" + idtype
        inp = [2**p - 1 for p in range(bitsize)]
    ainp = np.array(inp, dtype=idtype)
    assert_array_equal(ainp, ainp.astype("T").astype(idtype))

    # safe casting works
    ainp.astype("T", casting="safe")

    with pytest.raises(TypeError):
        ainp.astype("T").astype(idtype, casting="safe")

    oob = [str(2**bitsize), str(-(2**bitsize))]
    with pytest.raises(OverflowError):
        np.array(oob, dtype="T").astype(idtype)

    with pytest.raises(ValueError):
        np.array(["1", np.nan, "3"],
                 dtype=StringDType(na_object=np.nan)).astype(idtype)


@pytest.mark.parametrize("typename", ["byte", "short", "int", "longlong"])
@pytest.mark.parametrize("signed", ["", "u"])
def test_unsized_integer_casts(typename, signed):
    idtype = f"{signed}{typename}"

    inp = [1, 2, 3, 4]
    ainp = np.array(inp, dtype=idtype)
    assert_array_equal(ainp, ainp.astype("T").astype(idtype))


@pytest.mark.parametrize(
    "typename",
    [
        pytest.param(
            "longdouble",
            marks=pytest.mark.xfail(
                np.dtypes.LongDoubleDType() != np.dtypes.Float64DType(),
                reason="numpy lacks an ld2a implementation",
                strict=True,
            ),
        ),
        "float64",
        "float32",
        "float16",
    ],
)
def test_float_casts(typename):
    inp = [1.1, 2.8, -3.2, 2.7e4]
    ainp = np.array(inp, dtype=typename)
    assert_array_equal(ainp, ainp.astype("T").astype(typename))

    inp = [0.1]
    sres = np.array(inp, dtype=typename).astype("T")
    res = sres.astype(typename)
    assert_array_equal(np.array(inp, dtype=typename), res)
    assert sres[0] == "0.1"

    if typename == "longdouble":
        # let's not worry about platform-dependent rounding of longdouble
        return

    fi = np.finfo(typename)

    inp = [1e-324, fi.smallest_subnormal, -1e-324, -fi.smallest_subnormal]
    eres = [0, fi.smallest_subnormal, -0, -fi.smallest_subnormal]
    res = np.array(inp, dtype=typename).astype("T").astype(typename)
    assert_array_equal(eres, res)

    inp = [2e308, fi.max, -2e308, fi.min]
    eres = [np.inf, fi.max, -np.inf, fi.min]
    res = np.array(inp, dtype=typename).astype("T").astype(typename)
    assert_array_equal(eres, res)


def test_float_nan_cast_na_object():
    # gh-28157
    dt = np.dtypes.StringDType(na_object=np.nan)
    arr1 = np.full((1,), fill_value=np.nan, dtype=dt)
    arr2 = np.full_like(arr1, fill_value=np.nan)

    assert arr1.item() is np.nan
    assert arr2.item() is np.nan

    inp = [1.2, 2.3, np.nan]
    arr = np.array(inp).astype(dt)
    assert arr[2] is np.nan
    assert arr[0] == '1.2'


@pytest.mark.parametrize(
    "typename",
    [
        "csingle",
        "cdouble",
        pytest.param(
            "clongdouble",
            marks=pytest.mark.xfail(
                np.dtypes.CLongDoubleDType() != np.dtypes.Complex128DType(),
                reason="numpy lacks an ld2a implementation",
                strict=True,
            ),
        ),
    ],
)
def test_cfloat_casts(typename):
    inp = [1.1 + 1.1j, 2.8 + 2.8j, -3.2 - 3.2j, 2.7e4 + 2.7e4j]
    ainp = np.array(inp, dtype=typename)
    assert_array_equal(ainp, ainp.astype("T").astype(typename))

    inp = [0.1 + 0.1j]
    sres = np.array(inp, dtype=typename).astype("T")
    res = sres.astype(typename)
    assert_array_equal(np.array(inp, dtype=typename), res)
    assert sres[0] == "(0.1+0.1j)"


@pytest.mark.parametrize("typename", ["csingle", "cdouble", "clongdouble"])
def test_string_to_cfloat_cast_distinct_components(typename):
    inp = np.array(
        ["1.25+0.5j", "2.75-3.5j", "-3.125+4.25j", "27000-8j"],
        dtype="T",
    )
    expected = np.array(
        [1.25 + 0.5j, 2.75 - 3.5j, -3.125 + 4.25j, 2.7e4 - 8j],
        dtype=typename,
    )
    assert_array_equal(inp.astype(typename), expected)


def test_take(string_list):
    sarr = np.array(string_list, dtype="T")
    res = sarr.take(np.arange(len(string_list)))
    assert_array_equal(sarr, res)

    # make sure it also works for out
    out = np.empty(len(string_list), dtype="T")
    out[0] = "hello"
    res = sarr.take(np.arange(len(string_list)), out=out)
    assert res is out
    assert_array_equal(sarr, res)


@pytest.mark.parametrize("use_out", [True, False])
@pytest.mark.parametrize(
    "ufunc_name,func",
    [
        ("min", min),
        ("max", max),
    ],
)
def test_ufuncs_minmax(string_list, ufunc_name, func, use_out):
    """Test that the min/max ufuncs match Python builtin min/max behavior."""
    arr = np.array(string_list, dtype="T")
    uarr = np.array(string_list, dtype=str)
    res = np.array(func(string_list), dtype="T")
    assert_array_equal(getattr(arr, ufunc_name)(), res)

    ufunc = getattr(np, ufunc_name + "imum")

    if use_out:
        res = ufunc(arr, arr, out=arr)
    else:
        res = ufunc(arr, arr)

    assert_array_equal(uarr, res)
    assert_array_equal(getattr(arr, ufunc_name)(), func(string_list))


def test_max_regression():
    arr = np.array(['y', 'y', 'z'], dtype="T")
    assert arr.max() == 'z'


@pytest.mark.parametrize("use_out", [True, False])
@pytest.mark.parametrize(
    "other_strings",
    [
        ["abc", "def" * 500, "ghi" * 16, "🤣" * 100, "📵", "😰"],
        ["🚜", "🙃", "😾", "😹", "🚠", "🚌"],
        ["🥦", "¨", "⨯", "∰ ", "⨌ ", "⎶ "],
    ],
)
def test_ufunc_add(dtype, string_list, other_strings, use_out):
    arr1 = np.array(string_list, dtype=dtype)
    arr2 = np.array(other_strings, dtype=dtype)
    result = np.array([a + b for a, b in zip(arr1, arr2)], dtype=dtype)

    if use_out:
        res = np.add(arr1, arr2, out=arr1)
    else:
        res = np.add(arr1, arr2)

    assert_array_equal(res, result)

    if not hasattr(dtype, "na_object"):
        return

    is_nan = isinstance(dtype.na_object, float) and np.isnan(dtype.na_object)
    is_str = isinstance(dtype.na_object, str)
    bool_errors = 0
    try:
        bool(dtype.na_object)
    except TypeError:
        bool_errors = 1

    arr1 = np.array([dtype.na_object] + string_list, dtype=dtype)
    arr2 = np.array(other_strings + [dtype.na_object], dtype=dtype)

    if is_nan or bool_errors or is_str:
        res = np.add(arr1, arr2)
        assert_array_equal(res[1:-1], arr1[1:-1] + arr2[1:-1])
        if not is_str:
            assert res[0] is dtype.na_object and res[-1] is dtype.na_object
        else:
            assert res[0] == dtype.na_object + arr2[0]
            assert res[-1] == arr1[-1] + dtype.na_object
    else:
        with pytest.raises(ValueError):
            np.add(arr1, arr2)


def test_ufunc_add_reduce(dtype):
    values = ["a", "this is a long string", "c"]
    arr = np.array(values, dtype=dtype)
    out = np.empty((), dtype=dtype)

    expected = np.array("".join(values), dtype=dtype)
    assert_array_equal(np.add.reduce(arr), expected)

    np.add.reduce(arr, out=out)
    assert_array_equal(out, expected)


def test_add_promoter(string_list):
    arr = np.array(string_list, dtype=StringDType())
    lresult = np.array(["hello" + s for s in string_list], dtype=StringDType())
    rresult = np.array([s + "hello" for s in string_list], dtype=StringDType())

    for op in ["hello", np.str_("hello"), np.array(["hello"])]:
        assert_array_equal(op + arr, lresult)
        assert_array_equal(arr + op, rresult)

    # The promoter should be able to handle things if users pass `dtype=`
    res = np.add("hello", string_list, dtype=StringDType)
    assert res.dtype == StringDType()

    # The promoter should not kick in if users override the input,
    # which means arr is cast, this fails because of the unknown length.
    with pytest.raises(TypeError, match="cannot cast dtype"):
        np.add(arr, "add", signature=("U", "U", None), casting="unsafe")

    # But it must simply reject the following:
    with pytest.raises(TypeError, match=".*did not contain a loop"):
        np.add(arr, "add", signature=(None, "U", None))

    with pytest.raises(TypeError, match=".*did not contain a loop"):
        np.add("a", "b", signature=("U", "U", StringDType))


def test_add_no_legacy_promote_with_signature():
    # Possibly misplaced, but useful to test with string DType.  We check that
    # if there is clearly no loop found, a stray `dtype=` doesn't break things
    # Regression test for the bad error in gh-26735
    # (If legacy promotion is gone, this can be deleted...)
    with pytest.raises(TypeError, match=".*did not contain a loop"):
        np.add("3", 6, dtype=StringDType)


def test_add_promoter_reduce():
    # Exact TypeError could change, but ensure StringDtype doesn't match
    with pytest.raises(TypeError, match="the resolved dtypes are not"):
        np.add.reduce(np.array(["a", "b"], dtype="U"))

    # On the other hand, using `dtype=T` in the *ufunc* should work.
    np.add.reduce(np.array(["a", "b"], dtype="U"), dtype=np.dtypes.StringDType)


def test_multiply_reduce():
    # At the time of writing (NumPy 2.0) this is very limited (and rather
    # ridiculous anyway).  But it works and actually makes some sense...
    # (NumPy does not allow non-scalar initial values)
    repeats = np.array([2, 3, 4])
    val = "school-🚌"
    res = np.multiply.reduce(repeats, initial=val, dtype=np.dtypes.StringDType)
    assert res == val * np.prod(repeats)


def test_multiply_two_string_raises():
    arr = np.array(["hello", "world"], dtype="T")
    with pytest.raises(np._core._exceptions._UFuncNoLoopError):
        np.multiply(arr, arr)


@pytest.mark.parametrize("use_out", [True, False])
@pytest.mark.parametrize("other", [2, [2, 1, 3, 4, 1, 3]])
@pytest.mark.parametrize(
    "other_dtype",
    [
        None,
        "int8",
        "int16",
        "int32",
        "int64",
        "uint8",
        "uint16",
        "uint32",
        "uint64",
        "short",
        "int",
        "intp",
        "long",
        "longlong",
        "ushort",
        "uint",
        "uintp",
        "ulong",
        "ulonglong",
    ],
)
def test_ufunc_multiply(dtype, string_list, other, other_dtype, use_out):
    """Test the two-argument ufuncs match python builtin behavior."""
    arr = np.array(string_list, dtype=dtype)
    if other_dtype is not None:
        other_dtype = np.dtype(other_dtype)
    try:
        len(other)
        result = [s * o for s, o in zip(string_list, other)]
        other = np.array(other)
        if other_dtype is not None:
            other = other.astype(other_dtype)
    except TypeError:
        if other_dtype is not None:
            other = other_dtype.type(other)
        result = [s * other for s in string_list]

    if use_out:
        arr_cache = arr.copy()
        lres = np.multiply(arr, other, out=arr)
        assert_array_equal(lres, result)
        arr[:] = arr_cache
        assert lres is arr
        arr *= other
        assert_array_equal(arr, result)
        arr[:] = arr_cache
        rres = np.multiply(other, arr, out=arr)
        assert rres is arr
        assert_array_equal(rres, result)
    else:
        lres = arr * other
        assert_array_equal(lres, result)
        rres = other * arr
        assert_array_equal(rres, result)

    if not hasattr(dtype, "na_object"):
        return

    is_nan = np.isnan(np.array([dtype.na_object], dtype=dtype))[0]
    is_str = isinstance(dtype.na_object, str)
    bool_errors = 0
    try:
        bool(dtype.na_object)
    except TypeError:
        bool_errors = 1

    arr = np.array(string_list + [dtype.na_object], dtype=dtype)

    try:
        len(other)
        other = np.append(other, 3)
        if other_dtype is not None:
            other = other.astype(other_dtype)
    except TypeError:
        pass

    if is_nan or bool_errors or is_str:
        for res in [arr * other, other * arr]:
            assert_array_equal(res[:-1], result)
            if not is_str:
                assert res[-1] is dtype.na_object
            else:
                try:
                    assert res[-1] == dtype.na_object * other[-1]
                except (IndexError, TypeError):
                    assert res[-1] == dtype.na_object * other
    else:
        with pytest.raises(TypeError):
            arr * other
        with pytest.raises(TypeError):
            other * arr


def test_findlike_promoters():
    r = "Wally"
    l = "Where's Wally?"
    s = np.int32(3)
    e = np.int8(13)
    for dtypes in [("T", "U"), ("U", "T")]:
        for function, answer in [
            (np.strings.index, 8),
            (np.strings.endswith, True),
        ]:
            assert answer == function(
                np.array(l, dtype=dtypes[0]), np.array(r, dtype=dtypes[1]), s, e
            )


def test_strip_promoter():
    arg = ["Hello!!!!", "Hello??!!"]
    strip_char = "!"
    answer = ["Hello", "Hello??"]
    for dtypes in [("T", "U"), ("U", "T")]:
        result = np.strings.strip(
            np.array(arg, dtype=dtypes[0]),
            np.array(strip_char, dtype=dtypes[1])
        )
        assert_array_equal(result, answer)
        assert result.dtype.char == "T"


def test_replace_promoter():
    arg = ["Hello, planet!", "planet, Hello!"]
    old = "planet"
    new = "world"
    answer = ["Hello, world!", "world, Hello!"]
    for dtypes in itertools.product("TU", repeat=3):
        if dtypes == ("U", "U", "U"):
            continue
        answer_arr = np.strings.replace(
            np.array(arg, dtype=dtypes[0]),
            np.array(old, dtype=dtypes[1]),
            np.array(new, dtype=dtypes[2]),
        )
        assert_array_equal(answer_arr, answer)
        assert answer_arr.dtype.char == "T"


def test_center_promoter():
    arg = ["Hello", "planet!"]
    fillchar = "/"
    for dtypes in [("T", "U"), ("U", "T")]:
        answer = np.strings.center(
            np.array(arg, dtype=dtypes[0]), 9, np.array(fillchar, dtype=dtypes[1])
        )
        assert_array_equal(answer, ["//Hello//", "/planet!/"])
        assert answer.dtype.char == "T"


DATETIME_INPUT = [
    np.datetime64("1923-04-14T12:43:12"),
    np.datetime64("1994-06-21T14:43:15"),
    np.datetime64("2001-10-15T04:10:32"),
    np.datetime64("NaT", "D"),
    np.datetime64("1995-11-25T16:02:16"),
    np.datetime64("2005-01-04T03:14:12"),
    np.datetime64("2041-12-03T14:05:03"),
]


TIMEDELTA_INPUT = [
    np.timedelta64(12358, "s"),
    np.timedelta64(23, "s"),
    np.timedelta64(74, "s"),
    np.timedelta64("NaT", "s"),
    np.timedelta64(23, "s"),
    np.timedelta64(73, "s"),
    np.timedelta64(7, "s"),
]


@pytest.mark.parametrize(
    "input_data, input_dtype",
    [
        (DATETIME_INPUT, "M8[s]"),
        (TIMEDELTA_INPUT, "m8[s]")
    ]
)
def test_datetime_timedelta_cast(dtype, input_data, input_dtype):

    a = np.array(input_data, dtype=input_dtype)

    has_na = hasattr(dtype, "na_object")
    is_str = isinstance(getattr(dtype, "na_object", None), str)

    if not has_na or is_str:
        a = np.delete(a, 3)

    sa = a.astype(dtype)
    ra = sa.astype(a.dtype)

    if has_na and not is_str:
        assert sa[3] is dtype.na_object
        assert np.isnat(ra[3])

    assert_array_equal(a, ra)

    if has_na and not is_str:
        # don't worry about comparing how NaT is converted
        sa = np.delete(sa, 3)
        a = np.delete(a, 3)

    if input_dtype.startswith("M"):
        assert_array_equal(sa, a.astype("U"))
    else:
        # The timedelta to unicode cast produces strings
        # that aren't round-trippable and we don't want to
        # reproduce that behavior in stringdtype
        assert_array_equal(sa, a.astype("int64").astype("U"))


def test_nat_casts():
    s = 'nat'
    all_nats = itertools.product(*zip(s.upper(), s.lower()))
    all_nats = list(map(''.join, all_nats))
    NaT_dt = np.datetime64('NaT', 'D')
    NaT_td = np.timedelta64('NaT', 's')
    for na_object in [np._NoValue, None, np.nan, 'nat', '']:
        # numpy treats empty string and all case combinations of 'nat' as NaT
        dtype = StringDType(na_object=na_object)
        arr = np.array([''] + all_nats, dtype=dtype)
        dt_array = arr.astype('M8[s]')
        td_array = arr.astype('m8[s]')
        assert_array_equal(dt_array, NaT_dt)
        assert_array_equal(td_array, NaT_td)

        if na_object is np._NoValue:
            output_object = 'NaT'
        else:
            output_object = na_object

        for arr in [dt_array, td_array]:
            assert_array_equal(
                arr.astype(dtype),
                np.array([output_object] * arr.size, dtype=dtype))


def test_nat_conversion():
    for nat in [np.datetime64("NaT", "s"), np.timedelta64("NaT", "s")]:
        with pytest.raises(ValueError, match="string coercion is disabled"):
            np.array(["a", nat], dtype=StringDType(coerce=False))


def test_growing_strings(dtype):
    # growing a string leads to a heap allocation, this tests to make sure
    # we do that bookkeeping correctly for all possible starting cases
    data = [
        "hello",  # a short string
        "abcdefghijklmnopqestuvwxyz",  # a medium heap-allocated string
        "hello" * 200,  # a long heap-allocated string
    ]

    arr = np.array(data, dtype=dtype)
    uarr = np.array(data, dtype=str)

    for _ in range(5):
        arr = arr + arr
        uarr = uarr + uarr

    assert_array_equal(arr, uarr)


def test_assign_medium_strings():
    # see gh-29261
    N = 9
    src = np.array(
        (
            ['0' * 256] * 3 + ['0' * 255] + ['0' * 256] + ['0' * 255] +
            ['0' * 256] * 2 + ['0' * 255]
        ), dtype='T')
    dst = np.array(
        (
            ['0' * 255] + ['0' * 256] * 2 + ['0' * 255] + ['0' * 256] +
            ['0' * 255] + [''] * 5
        ), dtype='T')

    dst[1:N + 1] = src
    assert_array_equal(dst[1:N + 1], src)


UFUNC_TEST_DATA = [
    "hello" * 10,
    "Ae¢☃€ 😊" * 20,
    "entry\nwith\nnewlines",
    "entry\twith\ttabs",
]


@pytest.fixture
def string_array(dtype):
    return np.array(UFUNC_TEST_DATA, dtype=dtype)


@pytest.fixture
def unicode_array():
    return np.array(UFUNC_TEST_DATA, dtype=np.str_)


NAN_PRESERVING_FUNCTIONS = [
    "capitalize",
    "expandtabs",
    "lower",
    "lstrip",
    "rstrip",
    "splitlines",
    "strip",
    "swapcase",
    "title",
    "upper",
]

BOOL_OUTPUT_FUNCTIONS = [
    "isalnum",
    "isalpha",
    "isdigit",
    "islower",
    "isspace",
    "istitle",
    "isupper",
    "isnumeric",
    "isdecimal",
]

UNARY_FUNCTIONS = [
    "str_len",
    "capitalize",
    "expandtabs",
    "isalnum",
    "isalpha",
    "isdigit",
    "islower",
    "isspace",
    "istitle",
    "isupper",
    "lower",
    "lstrip",
    "rstrip",
    "splitlines",
    "strip",
    "swapcase",
    "title",
    "upper",
    "isnumeric",
    "isdecimal",
    "isalnum",
    "islower",
    "istitle",
    "isupper",
]

UNIMPLEMENTED_VEC_STRING_FUNCTIONS = [
    "capitalize",
    "expandtabs",
    "lower",
    "splitlines",
    "swapcase",
    "title",
    "upper",
]

ONLY_IN_NP_CHAR = [
    "join",
    "split",
    "rsplit",
    "splitlines"
]


@pytest.mark.parametrize("function_name", UNARY_FUNCTIONS)
def test_unary(string_array, unicode_array, function_name):
    if function_name in ONLY_IN_NP_CHAR:
        func = getattr(np.char, function_name)
    else:
        func = getattr(np.strings, function_name)
    dtype = string_array.dtype
    sres = func(string_array)
    ures = func(unicode_array)
    if sres.dtype == StringDType():
        ures = ures.astype(StringDType())
    assert_array_equal(sres, ures)

    if not hasattr(dtype, "na_object"):
        return

    is_nan = np.isnan(np.array([dtype.na_object], dtype=dtype))[0]
    is_str = isinstance(dtype.na_object, str)
    na_arr = np.insert(string_array, 0, dtype.na_object)

    if function_name in UNIMPLEMENTED_VEC_STRING_FUNCTIONS:
        if not is_str:
            # to avoid these errors we'd need to add NA support to _vec_string
            with pytest.raises((ValueError, TypeError)):
                func(na_arr)
        elif function_name == "splitlines":
            assert func(na_arr)[0] == func(dtype.na_object)[()]
        else:
            assert func(na_arr)[0] == func(dtype.na_object)
        return
    if function_name == "str_len" and not is_str:
        # str_len always errors for any non-string null, even NA ones because
        # it has an integer result
        with pytest.raises(ValueError):
            func(na_arr)
        return
    if function_name in BOOL_OUTPUT_FUNCTIONS:
        if is_nan:
            assert func(na_arr)[0] is np.False_
        elif is_str:
            assert func(na_arr)[0] == func(dtype.na_object)
        else:
            with pytest.raises(ValueError):
                func(na_arr)
        return
    if not (is_nan or is_str):
        with pytest.raises(ValueError):
            func(na_arr)
        return
    res = func(na_arr)
    if is_nan and function_name in NAN_PRESERVING_FUNCTIONS:
        assert res[0] is dtype.na_object
    elif is_str:
        assert res[0] == func(dtype.na_object)


unicode_bug_fail = pytest.mark.xfail(
    reason="unicode output width is buggy", strict=True
)

# None means that the argument is a string array
BINARY_FUNCTIONS = [
    ("add", (None, None)),
    ("multiply", (None, 2)),
    ("mod", ("format: %s", None)),
    ("center", (None, 25)),
    ("count", (None, "A")),
    ("encode", (None, "UTF-8")),
    ("endswith", (None, "lo")),
    ("find", (None, "A")),
    ("index", (None, "e")),
    ("join", ("-", None)),
    ("ljust", (None, 12)),
    ("lstrip", (None, "A")),
    ("partition", (None, "A")),
    ("replace", (None, "A", "B")),
    ("rfind", (None, "A")),
    ("rindex", (None, "e")),
    ("rjust", (None, 12)),
    ("rsplit", (None, "A")),
    ("rstrip", (None, "A")),
    ("rpartition", (None, "A")),
    ("split", (None, "A")),
    ("strip", (None, "A")),
    ("startswith", (None, "A")),
    ("zfill", (None, 12)),
]

PASSES_THROUGH_NAN_NULLS = [
    "add",
    "center",
    "ljust",
    "multiply",
    "replace",
    "rjust",
    "strip",
    "lstrip",
    "rstrip",
    "replace",
    "zfill",
]

NULLS_ARE_FALSEY = [
    "startswith",
    "endswith",
]

NULLS_ALWAYS_ERROR = [
    "count",
    "find",
    "rfind",
]

SUPPORTS_NULLS = (
    PASSES_THROUGH_NAN_NULLS +
    NULLS_ARE_FALSEY +
    NULLS_ALWAYS_ERROR
)


def call_func(func, args, array, sanitize=True):
    if args == (None, None):
        return func(array, array)
    if args[0] is None:
        if sanitize:
            san_args = tuple(
                np.array(arg, dtype=array.dtype) if isinstance(arg, str) else
                arg for arg in args[1:]
            )
        else:
            san_args = args[1:]
        return func(array, *san_args)
    if args[1] is None:
        return func(args[0], array)
    # shouldn't ever happen
    assert 0


@pytest.mark.parametrize("function_name, args", BINARY_FUNCTIONS)
def test_binary(string_array, unicode_array, function_name, args):
    if function_name in ONLY_IN_NP_CHAR:
        func = getattr(np.char, function_name)
    else:
        func = getattr(np.strings, function_name)
    sres = call_func(func, args, string_array)
    ures = call_func(func, args, unicode_array, sanitize=False)
    if not isinstance(sres, tuple) and sres.dtype == StringDType():
        ures = ures.astype(StringDType())
    assert_array_equal(sres, ures)

    dtype = string_array.dtype
    if function_name not in SUPPORTS_NULLS or not hasattr(dtype, "na_object"):
        return

    na_arr = np.insert(string_array, 0, dtype.na_object)
    is_nan = np.isnan(np.array([dtype.na_object], dtype=dtype))[0]
    is_str = isinstance(dtype.na_object, str)
    should_error = not (is_nan or is_str)

    if (
        (function_name in NULLS_ALWAYS_ERROR and not is_str)
        or (function_name in PASSES_THROUGH_NAN_NULLS and should_error)
        or (function_name in NULLS_ARE_FALSEY and should_error)
    ):
        with pytest.raises((ValueError, TypeError)):
            call_func(func, args, na_arr)
        return

    res = call_func(func, args, na_arr)

    if is_str:
        assert res[0] == call_func(func, args, na_arr[:1])
    elif function_name in NULLS_ARE_FALSEY:
        assert res[0] is np.False_
    elif function_name in PASSES_THROUGH_NAN_NULLS:
        assert res[0] is dtype.na_object
    else:
        # shouldn't ever get here
        assert 0


@pytest.mark.parametrize("function, expected", [
    (np.strings.find, [[2, -1], [1, -1]]),
    (np.strings.startswith, [[False, False], [True, False]])])
@pytest.mark.parametrize("start, stop", [
    (1, 4),
    (np.int8(1), np.int8(4)),
    (np.array([1, 1], dtype='u2'), np.array([4, 4], dtype='u2'))])
def test_non_default_start_stop(function, start, stop, expected):
    a = np.array([["--🐍--", "--🦜--"],
                  ["-🐍---", "-🦜---"]], "T")
    indx = function(a, "🐍", start, stop)
    assert_array_equal(indx, expected)


@pytest.mark.parametrize("count", [2, np.int8(2), np.array([2, 2], 'u2')])
def test_replace_non_default_repeat(count):
    a = np.array(["🐍--", "🦜-🦜-"], "T")
    result = np.strings.replace(a, "🦜-", "🦜†", count)
    assert_array_equal(result, np.array(["🐍--", "🦜†🦜†"], "T"))


def test_trailing_null_is_not_padding():
    arr = np.array(["x\0", "\0", "x\0y\0", "abc"], dtype=StringDType())
    nul = np.array("\0", dtype=StringDType())

    assert_array_equal(np.strings.str_len(arr), [2, 1, 4, 3])
    assert_array_equal(np.strings.find(arr, nul), [1, 0, 1, -1])
    assert_array_equal(np.strings.rfind(arr, nul), [1, 0, 3, -1])
    assert_array_equal(np.strings.count(arr, nul), [1, 1, 2, 0])
    assert_array_equal(np.strings.endswith(arr, nul),
                       [True, True, True, False])
    assert_array_equal(np.strings.slice(arr, -1, None),
                       np.array(["\0", "\0", "\0", "c"],
                                dtype=StringDType()))


def test_trailing_null_is_not_stripped_as_whitespace():
    arr = np.array(["x\0", "\0 ", " \0", "x\0 \t"],
                   dtype=StringDType())

    assert_array_equal(
            np.strings.rstrip(arr),
            np.array(["x\0", "\0", " \0", "x\0"], dtype=StringDType()))
    assert_array_equal(
            np.strings.strip(arr),
            np.array(["x\0", "\0", "\0", "x\0"], dtype=StringDType()))


def test_strip_ljust_rjust_consistency(string_array, unicode_array):
    rjs = np.char.rjust(string_array, 1000)
    rju = np.char.rjust(unicode_array, 1000)

    ljs = np.char.ljust(string_array, 1000)
    lju = np.char.ljust(unicode_array, 1000)

    assert_array_equal(
        np.char.lstrip(rjs),
        np.char.lstrip(rju).astype(StringDType()),
    )

    assert_array_equal(
        np.char.rstrip(ljs),
        np.char.rstrip(lju).astype(StringDType()),
    )

    assert_array_equal(
        np.char.strip(ljs),
        np.char.strip(lju).astype(StringDType()),
    )

    assert_array_equal(
        np.char.strip(rjs),
        np.char.strip(rju).astype(StringDType()),
    )


def test_unset_na_coercion():
    # a dtype instance with an unset na object is compatible
    # with a dtype that has one set

    # this test uses the "add" and "equal" ufunc but all ufuncs that
    # accept more than one string argument and produce a string should
    # behave this way
    # TODO: generalize to more ufuncs
    inp = ["hello", "world"]
    arr = np.array(inp, dtype=StringDType(na_object=None))
    for op_dtype in [None, StringDType(), StringDType(coerce=False),
                     StringDType(na_object=None)]:
        if op_dtype is None:
            op = "2"
        else:
            op = np.array("2", dtype=op_dtype)
        res = arr + op
        assert_array_equal(res, ["hello2", "world2"])

    # dtype instances with distinct explicitly set NA objects are incompatible
    for op_dtype in [StringDType(na_object=pd_NA), StringDType(na_object="")]:
        op = np.array("2", dtype=op_dtype)
        with pytest.raises(TypeError):
            arr + op

    # comparisons only consider the na_object
    for op_dtype in [None, StringDType(), StringDType(coerce=True),
                     StringDType(na_object=None)]:
        if op_dtype is None:
            op = inp
        else:
            op = np.array(inp, dtype=op_dtype)
        assert_array_equal(arr, op)

    for op_dtype in [StringDType(na_object=pd_NA),
                     StringDType(na_object=np.nan)]:
        op = np.array(inp, dtype=op_dtype)
        with pytest.raises(TypeError):
            arr == op


def test_repeat(string_array):
    res = string_array.repeat(1000)
    # Create an empty array with expanded dimension, and fill it.  Then,
    # reshape it to the expected result.
    expected = np.empty_like(string_array, shape=string_array.shape + (1000,))
    expected[...] = string_array[:, np.newaxis]
    expected = expected.reshape(-1)

    assert_array_equal(res, expected, strict=True)


@pytest.mark.parametrize("tile", [1, 6, (2, 5)])
def test_accumulation(string_array, tile):
    """Accumulation is odd for StringDType but tests dtypes with references.
    """
    # Fill with mostly empty strings to not create absurdly big strings
    arr = np.zeros_like(string_array, shape=(100,))
    arr[:len(string_array)] = string_array
    arr[-len(string_array):] = string_array

    # Bloat size a bit (get above thresholds and test >1 ndim).
    arr = np.tile(string_array, tile)

    res = np.add.accumulate(arr, axis=0)
    res_obj = np.add.accumulate(arr.astype(object), axis=0)
    assert_array_equal(res, res_obj.astype(arr.dtype), strict=True)

    if arr.ndim > 1:
        res = np.add.accumulate(arr, axis=-1)
        res_obj = np.add.accumulate(arr.astype(object), axis=-1)

        assert_array_equal(res, res_obj.astype(arr.dtype), strict=True)


class TestImplementation:
    """Check that strings are stored in the arena when possible.

    This tests implementation details, so should be adjusted if
    the implementation changes.
    """

    @classmethod
    def setup_class(cls):
        cls.MISSING = 0x80
        cls.INITIALIZED = 0x40
        cls.OUTSIDE_ARENA = 0x20
        cls.LONG = 0x10
        cls.dtype = StringDType(na_object=np.nan)
        cls.sizeofstr = cls.dtype.itemsize
        sp = cls.dtype.itemsize // 2  # pointer size = sizeof(size_t)
        # Below, size is not strictly correct, since it really uses
        # 7 (or 3) bytes, but good enough for the tests here.
        cls.view_dtype = np.dtype([
            ('offset', f'u{sp}'),
            ('size', f'u{sp // 2}'),
            ('xsiz', f'V{sp // 2 - 1}'),
            ('size_and_flags', 'u1'),
        ] if sys.byteorder == 'little' else [
            ('size_and_flags', 'u1'),
            ('xsiz', f'V{sp // 2 - 1}'),
            ('size', f'u{sp // 2}'),
            ('offset', f'u{sp}'),
        ])
        cls.s_empty = ""
        cls.s_short = "01234"
        cls.s_medium = "abcdefghijklmnopqrstuvwxyz"
        cls.s_long = "-=+" * 100
        cls.a = np.array(
            [cls.s_empty, cls.s_short, cls.s_medium, cls.s_long],
            cls.dtype)

    def get_view(self, a):
        # Cannot view a StringDType as anything else directly, since
        # it has references. So, we use a stride trick hack.
        from numpy.lib._stride_tricks_impl import DummyArray
        interface = dict(a.__array_interface__)
        interface['descr'] = self.view_dtype.descr
        interface['typestr'] = self.view_dtype.str
        return np.asarray(DummyArray(interface, base=a))

    def get_flags(self, a):
        return self.get_view(a)['size_and_flags'] & 0xf0

    def is_short(self, a):
        return self.get_flags(a) == self.INITIALIZED | self.OUTSIDE_ARENA

    def is_on_heap(self, a):
        return self.get_flags(a) == (self.INITIALIZED
                                     | self.OUTSIDE_ARENA
                                     | self.LONG)

    def is_missing(self, a):
        return self.get_flags(a) & self.MISSING == self.MISSING

    def in_arena(self, a):
        return (self.get_flags(a) & (self.INITIALIZED | self.OUTSIDE_ARENA)
                == self.INITIALIZED)

    def test_setup(self):
        is_short = self.is_short(self.a)
        length = np.strings.str_len(self.a)
        assert_array_equal(is_short, (length > 0) & (length <= 15))
        assert_array_equal(self.in_arena(self.a), [False, False, True, True])
        assert_array_equal(self.is_on_heap(self.a), False)
        assert_array_equal(self.is_missing(self.a), False)
        view = self.get_view(self.a)
        sizes = np.where(is_short, view['size_and_flags'] & 0xf,
                         view['size'])
        assert_array_equal(sizes, np.strings.str_len(self.a))
        assert_array_equal(view['xsiz'][2:],
                           np.void(b'\x00' * (self.sizeofstr // 4 - 1)))
        # Check that the medium string uses only 1 byte for its length
        # in the arena, while the long string takes 8 (or 4).
        offsets = view['offset']
        assert offsets[2] == 1
        assert offsets[3] == 1 + len(self.s_medium) + self.sizeofstr // 2

    def test_empty(self):
        e = np.empty((3,), self.dtype)
        assert_array_equal(self.get_flags(e), 0)
        assert_array_equal(e, "")

    def test_zeros(self):
        z = np.zeros((2,), self.dtype)
        assert_array_equal(self.get_flags(z), 0)
        assert_array_equal(z, "")

    def test_copy(self):
        for c in [self.a.copy(), copy.copy(self.a), copy.deepcopy(self.a)]:
            assert_array_equal(self.get_flags(c), self.get_flags(self.a))
            assert_array_equal(c, self.a)
            offsets = self.get_view(c)['offset']
            assert offsets[2] == 1
            assert offsets[3] == 1 + len(self.s_medium) + self.sizeofstr // 2

    def test_arena_use_with_setting(self):
        c = np.zeros_like(self.a)
        assert_array_equal(self.get_flags(c), 0)
        c[:] = self.a
        assert_array_equal(self.get_flags(c), self.get_flags(self.a))
        assert_array_equal(c, self.a)

    def test_arena_reuse_with_setting(self):
        c = self.a.copy()
        c[:] = self.a
        assert_array_equal(self.get_flags(c), self.get_flags(self.a))
        assert_array_equal(c, self.a)

    def test_arena_reuse_after_missing(self):
        c = self.a.copy()
        c[:] = np.nan
        assert np.all(self.is_missing(c))
        # Replacing with the original strings, the arena should be reused.
        c[:] = self.a
        assert_array_equal(self.get_flags(c), self.get_flags(self.a))
        assert_array_equal(c, self.a)

    def test_arena_reuse_after_empty(self):
        c = self.a.copy()
        c[:] = ""
        assert_array_equal(c, "")
        # Replacing with the original strings, the arena should be reused.
        c[:] = self.a
        assert_array_equal(self.get_flags(c), self.get_flags(self.a))
        assert_array_equal(c, self.a)

    def test_arena_reuse_for_shorter(self):
        c = self.a.copy()
        # A string slightly shorter than the shortest in the arena
        # should be used for all strings in the arena.
        c[:] = self.s_medium[:-1]
        assert_array_equal(c, self.s_medium[:-1])
        # first empty string in original was never initialized, so
        # filling it in now leaves it initialized inside the arena.
        # second string started as a short string so it can never live
        # in the arena.
        in_arena = np.array([True, False, True, True])
        assert_array_equal(self.in_arena(c), in_arena)
        # But when a short string is replaced, it will go on the heap.
        assert_array_equal(self.is_short(c), False)
        assert_array_equal(self.is_on_heap(c), ~in_arena)
        # We can put the originals back, and they'll still fit,
        # and short strings are back as short strings
        c[:] = self.a
        assert_array_equal(c, self.a)
        assert_array_equal(self.in_arena(c), in_arena)
        assert_array_equal(self.is_short(c), self.is_short(self.a))
        assert_array_equal(self.is_on_heap(c), False)

    def test_arena_reuse_if_possible(self):
        c = self.a.copy()
        # A slightly longer string will not fit in the arena for
        # the medium string, but will fit for the longer one.
        c[:] = self.s_medium + "±"
        assert_array_equal(c, self.s_medium + "±")
        in_arena_exp = np.strings.str_len(self.a) >= len(self.s_medium) + 1
        # first entry started uninitialized and empty, so filling it leaves
        # it in the arena
        in_arena_exp[0] = True
        assert not np.all(in_arena_exp == self.in_arena(self.a))
        assert_array_equal(self.in_arena(c), in_arena_exp)
        assert_array_equal(self.is_short(c), False)
        assert_array_equal(self.is_on_heap(c), ~in_arena_exp)
        # And once outside arena, it stays outside, since offset is lost.
        # But short strings are used again.
        c[:] = self.a
        is_short_exp = self.is_short(self.a)
        assert_array_equal(c, self.a)
        assert_array_equal(self.in_arena(c), in_arena_exp)
        assert_array_equal(self.is_short(c), is_short_exp)
        assert_array_equal(self.is_on_heap(c), ~in_arena_exp & ~is_short_exp)

    def test_arena_no_reuse_after_short(self):
        c = self.a.copy()
        # If we replace a string with a short string, it cannot
        # go into the arena after because the offset is lost.
        c[:] = self.s_short
        assert_array_equal(c, self.s_short)
        assert_array_equal(self.in_arena(c), False)
        c[:] = self.a
        assert_array_equal(c, self.a)
        assert_array_equal(self.in_arena(c), False)
        assert_array_equal(self.is_on_heap(c), self.in_arena(self.a))


# Tests for operations that mix several StringDType arrays. Independently
# created arrays always have distinct descriptor instances, each owning the
# allocator and arena backing its strings; see _make_distinct_arena_arrays
# for how the test data makes misdirected reads detectable.


def _make_distinct_arena_arrays(n, prefix_a="A", prefix_b="B"):
    """Make two arrays with distinct dtype instances and equal arena layouts.

    All strings are longer than 15 bytes, so every entry lives in its
    descriptor's arena. Lengths match between the two arrays but contents
    differ, so an entry resolved through the wrong descriptor's arena reads
    detectably wrong data.
    """
    a_list = [f"{prefix_a * 10}{i:06d}" for i in range(n)]
    b_list = [f"{prefix_b * 10}{i:06d}" for i in range(n)]
    a = np.array(a_list, dtype="T")
    b = np.array(b_list, dtype="T")
    assert a.dtype is not b.dtype
    return a, b, np.array(a_list, dtype=object), np.array(b_list, dtype=object)


@pytest.mark.parametrize("mode", ["raise", "wrap", "clip"])
def test_put_distinct_allocators(mode):
    a, b, a_obj, b_obj = _make_distinct_arena_arrays(100)
    inds = np.arange(0, 100, 2)
    np.put(a, inds, b[:50], mode=mode)
    np.put(a_obj, inds, b_obj[:50], mode=mode)
    assert_array_equal(a, a_obj)

    # values must cycle when there are fewer of them than indices
    np.put(a, inds, b[:3], mode=mode)
    np.put(a_obj, inds, b_obj[:3], mode=mode)
    assert_array_equal(a, a_obj)

    # all-short-string destination, so its arena is empty
    c = np.array(["x"] * 100, dtype="T")
    np.put(c, inds, b[:50], mode=mode)
    assert_array_equal(c[inds], b_obj[:50])
    assert_array_equal(c[1::2], "x")

    # a non-contiguous destination is written through a writeback copy
    d, _, d_obj, _ = _make_distinct_arena_arrays(100, prefix_a="D")
    np.put(d[::2], np.arange(50), b[:50], mode=mode)
    np.put(d_obj[::2], np.arange(50), b_obj[:50], mode=mode)
    assert_array_equal(d, d_obj)


def test_putmask_distinct_allocators():
    a, b, a_obj, b_obj = _make_distinct_arena_arrays(100)
    mask = np.arange(100) % 3 == 0
    np.putmask(a, mask, b)
    np.putmask(a_obj, mask, b_obj)
    assert_array_equal(a, a_obj)

    # fewer values than mask entries exercises value cycling
    np.putmask(a, ~mask, b[:7])
    np.putmask(a_obj, ~mask, b_obj[:7])
    assert_array_equal(a, a_obj)

    # all-short-string destination, so its arena is empty
    c = np.array(["x"] * 100, dtype="T")
    np.putmask(c, mask, b)
    assert_array_equal(c[mask], b_obj[mask])
    assert_array_equal(c[~mask], "x")

    # a non-contiguous destination is written through a writeback copy
    d, _, d_obj, _ = _make_distinct_arena_arrays(100, prefix_a="D")
    np.putmask(d[::2], mask[::2], b[:50])
    np.putmask(d_obj[::2], mask[::2], b_obj[:50])
    assert_array_equal(d, d_obj)


def test_putmask_distinct_allocators_na(string_list):
    dt_a = get_dtype(None)
    dt_b = get_dtype(None)
    a = np.array(string_list, dtype=dt_a)
    b = np.array([None] + string_list[:0:-1], dtype=dt_b)
    assert a.dtype is not b.dtype
    mask = np.arange(len(string_list)) % 2 == 0
    np.putmask(a, mask, b)
    for i in range(len(string_list)):
        if i == 0:
            assert a[i] is None
        elif mask[i]:
            assert a[i] == string_list[-i]
        else:
            assert a[i] == string_list[i]


@pytest.mark.parametrize("mode", ["raise", "wrap"])
def test_choose_distinct_allocators(mode):
    n = 100
    idx = np.arange(n) % 2
    # an all-short-string choice mixed with arena-string choices
    c0 = np.array(["x"] * n, dtype="T")
    c1, c2, c1_obj, c2_obj = _make_distinct_arena_arrays(n)
    c0_obj = np.array(["x"] * n, dtype=object)

    expected = np.choose(idx, [c0_obj, c1_obj], mode=mode)
    assert_array_equal(np.choose(idx, [c0, c1], mode=mode), expected)

    expected = np.choose(idx, [c1_obj, c2_obj], mode=mode)
    assert_array_equal(np.choose(idx, [c1, c2], mode=mode), expected)

    # out= with its own independently created instance
    out = np.empty(n, dtype="T")
    np.choose(idx, [c1, c2], mode=mode, out=out)
    assert_array_equal(out, expected)


def test_place_distinct_allocators():
    a = np.array(["ab", "cd", "ef"], dtype="T")
    np.place(a, [True, False, True], np.array(["xy", "zw"], dtype="T"))
    assert_array_equal(a, ["xy", "cd", "zw"])

    a, b, a_obj, b_obj = _make_distinct_arena_arrays(100)
    mask = np.arange(100) % 3 == 0
    # fewer values than selected entries exercises value cycling
    np.place(a, mask, b[:7])
    np.place(a_obj, mask, b_obj[:7])
    assert_array_equal(a, a_obj)

    # all-short-string destination, so its arena is empty
    c = np.array(["x"] * 100, dtype="T")
    np.place(c, mask, b)
    assert_array_equal(c[mask], b_obj[: mask.sum()])
    assert_array_equal(c[~mask], "x")


def test_view_distinct_instance():
    a = np.array(["a" * 20, "b" * 20], dtype="T")

    assert_array_equal(a.view(a.dtype), a)

    # a view through any other instance would attach an unrelated allocator,
    # which the generalized reference-safety check rejects
    with pytest.raises(TypeError, match="Cannot change data-type"):
        a.view(StringDType())
    with pytest.raises(TypeError, match="Cannot get/set field"):
        a.getfield(StringDType())
    with pytest.raises(TypeError, match="Cannot change data-type"):
        with pytest.warns(DeprecationWarning, match="Setting the dtype"):
            a.dtype = StringDType()

    res = a.astype(StringDType())
    assert res.dtype is not a.dtype
    assert_array_equal(res, a)


def test_concatenate_distinct_allocators():
    a, b, a_obj, b_obj = _make_distinct_arena_arrays(50)
    expected = np.concatenate([a_obj, b_obj])
    assert_array_equal(np.concatenate([a, b]), expected)
    assert_array_equal(np.concatenate([a, b], axis=None), expected)

    out = np.empty(100, dtype="T")
    np.concatenate([a, b], out=out)
    assert_array_equal(out, expected)

    assert_array_equal(np.stack([a, b]), np.stack([a_obj, b_obj]))
    assert_array_equal(np.vstack([a, b]), np.vstack([a_obj, b_obj]))
    assert_array_equal(np.hstack([a, b]), expected)


def test_where_distinct_allocators():
    a, b, a_obj, b_obj = _make_distinct_arena_arrays(101)
    mask = np.arange(101) % 3 == 0
    assert_array_equal(np.where(mask, a, b), np.where(mask, a_obj, b_obj))


def test_indexing_ops_distinct_allocators():
    a, b, a_obj, b_obj = _make_distinct_arena_arrays(60)
    idx = np.array([5, 3, 50, 7] * 3)

    out = np.empty(len(idx), dtype="T")
    np.take(a, idx, out=out)
    assert_array_equal(out, a_obj[idx])

    assert_array_equal(np.tile(a[:5], 3), np.tile(a_obj[:5], 3))
    assert_array_equal(np.roll(a, 7), np.roll(a_obj, 7))
    assert_array_equal(np.repeat(a[:10], 3), np.repeat(a_obj[:10], 3))
    assert_array_equal(np.delete(a, idx[:4]), np.delete(a_obj, idx[:4]))
    assert_array_equal(
        np.insert(a, 3, b[:4]), np.insert(a_obj, 3, b_obj[:4])
    )
    assert_array_equal(np.append(a, b), np.append(a_obj, b_obj))


def test_setops_distinct_allocators():
    vals = [f"{'v' * 16}{i:04d}" for i in range(90)]
    a = np.array(vals[:60], dtype="T")
    b = np.array(vals[30:], dtype="T")
    assert a.dtype is not b.dtype
    au = np.array(vals[:60], dtype="U20")
    bu = np.array(vals[30:], dtype="U20")

    assert_array_equal(np.isin(a, b), np.isin(au, bu))
    assert_array_equal(np.union1d(a, b), np.union1d(au, bu))
    assert_array_equal(np.intersect1d(a, b), np.intersect1d(au, bu))
    assert_array_equal(np.setdiff1d(a, b), np.setdiff1d(au, bu))
    assert_array_equal(np.setxor1d(a, b), np.setxor1d(au, bu))

    # StringDType has hasobject set, so isin always takes the
    # element-comparison loop and 'table' only supports integers
    assert_array_equal(
        np.isin(a, b, invert=True), np.isin(au, bu, invert=True)
    )
    assert_array_equal(np.isin(a, b[:4]), np.isin(au, bu[:4]))
    with pytest.raises(ValueError, match="table"):
        np.isin(a, b, kind="table")

    assert_array_equal(
        np.intersect1d(a, b, assume_unique=True),
        np.intersect1d(au, bu, assume_unique=True),
    )

    # duplicated entries exercise the sort-based unique path that
    # return_indices uses internally
    a_dup = np.array((vals[:40] * 2)[::-1], dtype="T")
    b_dup = np.array(vals[20:] + vals[60:], dtype="T")
    res = np.intersect1d(a_dup, b_dup, return_indices=True)
    expected = np.intersect1d(
        a_dup.astype("U20"), b_dup.astype("U20"), return_indices=True
    )
    for r, e in zip(res, expected):
        assert_array_equal(r, e)


def test_unique_arena_strings():
    # _unique_hash has a dedicated StringDType loop
    vals = [f"{'u' * 16}{i % 7:04d}" for i in range(50)] + ["ab", "ab", ""]
    arr = np.array(vals, dtype="T")
    arr_u = arr.astype("U20")
    assert_array_equal(np.unique(arr), np.unique(arr_u))
    assert_array_equal(np.sort(np.unique_values(arr)), np.unique(arr_u))

    # index/inverse/counts go through the sort-based path
    res = np.unique(
        arr, return_index=True, return_inverse=True, return_counts=True
    )
    expected = np.unique(
        arr_u, return_index=True, return_inverse=True, return_counts=True
    )
    for r, e in zip(res, expected):
        assert_array_equal(r, e)


def test_lexsort_distinct_allocators():
    n = 40
    # ties in the primary key so the secondary key matters
    prim = np.array([f"{'p' * 20}{i % 5:03d}" for i in range(n)], dtype="T")
    sec = np.array(
        [f"{'s' * 20}{(7 * i) % n:03d}" for i in range(n)], dtype="T"
    )
    assert prim.dtype is not sec.dtype
    expected = np.lexsort((sec.astype("U30"), prim.astype("U30")))
    assert_array_equal(np.lexsort((sec, prim)), expected)


def test_strings_ufuncs_distinct_allocators():
    n = 50
    a_list = [f"{'AB' * 10}{i:06d}" for i in range(n)]
    # equal to a in every other entry, all arena strings
    b_list = [s if i % 2 else s[:-1] + "Z" for i, s in enumerate(a_list)]
    a = np.array(a_list, dtype="T")
    b = np.array(b_list, dtype="T")
    assert a.dtype is not b.dtype
    au = a.astype("U40")
    bu = b.astype("U40")

    expected = np.add(np.array(a_list, dtype=object),
                      np.array(b_list, dtype=object))
    assert_array_equal(np.add(a, b), expected)
    out = np.empty(n, dtype="T")
    np.add(a, b, out=out)
    assert_array_equal(out, expected)

    for op in [
        np.equal, np.not_equal, np.less, np.less_equal, np.greater,
        np.greater_equal,
    ]:
        assert_array_equal(op(a, b), op(au, bu))

    # no fixed-width unicode loops for maximum/minimum, so use object
    a_obj = np.array(a_list, dtype=object)
    b_obj = np.array(b_list, dtype=object)
    assert_array_equal(np.maximum(a, b), np.maximum(a_obj, b_obj))
    assert_array_equal(np.minimum(a, b), np.minimum(a_obj, b_obj))
    np.maximum(a, b, out=out)
    assert_array_equal(out, np.maximum(a_obj, b_obj))

    # needles long enough to live in the arena, found in half the entries
    needles_list = [
        a_list[i][:16] if i % 3 else "Z" * 16 for i in range(n)
    ]
    needles = np.array(needles_list, dtype="T")
    needles_u = needles.astype("U20")
    for func in [
        np.strings.find, np.strings.count, np.strings.startswith,
        np.strings.endswith,
    ]:
        assert_array_equal(func(a, needles), func(au, needles_u))

    # three distinct instances feeding one ufunc
    old = np.array(["AB" * 8] * n, dtype="T")
    new = np.array(["xy" * 9] * n, dtype="T")
    assert_array_equal(
        np.strings.replace(a, old, new),
        np.strings.replace(au, old.astype("U16"), new.astype("U18")),
    )

    chars = np.array(["BA0123456789" + "C" * 8] * n, dtype="T")
    assert_array_equal(
        np.strings.strip(a, chars), np.strings.strip(au, chars.astype("U20"))
    )

    sep = np.array(["AB" * 8] * n, dtype="T")
    for part, part_u in zip(
        np.strings.partition(a, sep),
        np.strings.partition(au, sep.astype("U16")),
    ):
        assert_array_equal(part, part_u)


def test_assignment_distinct_allocators():
    a, b, a_obj, b_obj = _make_distinct_arena_arrays(40)
    mask = np.arange(40) % 4 == 0

    a[mask] = b[mask]
    a_obj[mask] = b_obj[mask]
    assert_array_equal(a, a_obj)

    idx = np.array([1, 2, 3])
    a[idx] = b[:3]
    a_obj[idx] = b_obj[:3]
    assert_array_equal(a, a_obj)

    np.copyto(a, b, where=~mask)
    np.copyto(a_obj, b_obj, where=~mask)
    assert_array_equal(a, a_obj)

    res = np.select([mask, ~mask], [a, b], default="d" * 20)
    expected = np.select([mask, ~mask], [a_obj, b_obj], default="d" * 20)
    assert_array_equal(res, expected)


def test_ufunc_at_distinct_allocators():
    a, b, a_obj, b_obj = _make_distinct_arena_arrays(10)
    idx = np.array([0, 3, 3, 7])

    np.maximum.at(a, idx, b[:4])
    np.maximum.at(a_obj, idx, b_obj[:4])
    assert_array_equal(a, a_obj)

    c, d, c_obj, d_obj = _make_distinct_arena_arrays(10, "C", "D")
    np.add.at(c, idx, d[:4])
    np.add.at(c_obj, idx, d_obj[:4])
    assert_array_equal(c, c_obj)


def test_flatiter_subscript_distinct_allocators():
    a, _, a_obj, _ = _make_distinct_arena_arrays(20)

    assert_array_equal(np.array(a.flat[:1]), a_obj[:1])

    for index in [
        slice(None, 1), slice(1, None), slice(None, None, 3),
        np.array([3, 0, 17]),
        np.arange(20) % 3 == 0,
    ]:
        res = a.flat[index]
        expected = a_obj[index]
        assert_array_equal(res, expected)
        # element reads resolve through res's own descriptor
        for i in range(len(expected)):
            assert res[i] == expected[i]

    assert a.flat[3] == a_obj[3]
    assert_array_equal(np.array(a.flat), a_obj)
    assert_array_equal(a.flat.copy(), a_obj)


def test_flat_assignment_distinct_allocators():
    a, b, a_obj, b_obj = _make_distinct_arena_arrays(20)
    b.flat = a
    b_obj.flat = a_obj
    assert_array_equal(b, b_obj)

    # fewer values than elements exercises value cycling
    c, _, c_obj, _ = _make_distinct_arena_arrays(20, prefix_a="C")
    c.flat = a[:3]
    c_obj.flat = a_obj[:3]
    assert_array_equal(c, c_obj)

    # short (inline) values into an arena-string destination
    d, _, d_obj, _ = _make_distinct_arena_arrays(20, prefix_a="D")
    d.flat = ["xy"]
    d_obj.flat = ["xy"]
    assert_array_equal(d, d_obj)
