import numpy as np
import pytest

from pandas._libs import lib, writers as libwriters

from pandas import Index
import pandas._testing as tm


class TestMisc:
    def test_max_len_string_array(self):

        arr = a = np.array(["foo", "b", np.nan], dtype="object")
        assert libwriters.max_len_string_array(arr) == 3

        # unicode
        arr = a.astype("U").astype(object)
        assert libwriters.max_len_string_array(arr) == 3

        # bytes for python3
        arr = a.astype("S").astype(object)
        assert libwriters.max_len_string_array(arr) == 3

        # raises
        with pytest.raises(TypeError):
            libwriters.max_len_string_array(arr.astype("U"))

    def test_fast_unique_multiple_list_gen_sort(self):
        keys = [["p", "a"], ["n", "d"], ["a", "s"]]

        gen = (key for key in keys)
        expected = np.array(["a", "d", "n", "p", "s"])
        out = lib.fast_unique_multiple_list_gen(gen, sort=True)
        tm.assert_numpy_array_equal(np.array(out), expected)

        gen = (key for key in keys)
        expected = np.array(["p", "a", "n", "d", "s"])
        out = lib.fast_unique_multiple_list_gen(gen, sort=False)
        tm.assert_numpy_array_equal(np.array(out), expected)


class TestIndexing:
    def test_maybe_indices_to_slice_left_edge(self):
        target = np.arange(100)

        # slice
        indices = np.array([], dtype=np.int64)
        maybe_slice = lib.maybe_indices_to_slice(indices, len(target))

        assert isinstance(maybe_slice, slice)
        tm.assert_numpy_array_equal(target[indices], target[maybe_slice])

        for end in [1, 2, 5, 20, 99]:
            for step in [1, 2, 4]:
                indices = np.arange(0, end, step, dtype=np.int64)
                maybe_slice = lib.maybe_indices_to_slice(indices, len(target))

                assert isinstance(maybe_slice, slice)
                tm.assert_numpy_array_equal(target[indices], target[maybe_slice])

                # reverse
                indices = indices[::-1]
                maybe_slice = lib.maybe_indices_to_slice(indices, len(target))

                assert isinstance(maybe_slice, slice)
                tm.assert_numpy_array_equal(target[indices], target[maybe_slice])

        # not slice
        for case in [[2, 1, 2, 0], [2, 2, 1, 0], [0, 1, 2, 1], [-2, 0, 2], [2, 0, -2]]:
            indices = np.array(case, dtype=np.int64)
            maybe_slice = lib.maybe_indices_to_slice(indices, len(target))

            assert not isinstance(maybe_slice, slice)
            tm.assert_numpy_array_equal(maybe_slice, indices)
            tm.assert_numpy_array_equal(target[indices], target[maybe_slice])

    def test_maybe_indices_to_slice_right_edge(self):
        target = np.arange(100)

        # slice
        for start in [0, 2, 5, 20, 97, 98]:
            for step in [1, 2, 4]:
                indices = np.arange(start, 99, step, dtype=np.int64)
                maybe_slice = lib.maybe_indices_to_slice(indices, len(target))

                assert isinstance(maybe_slice, slice)
                tm.assert_numpy_array_equal(target[indices], target[maybe_slice])

                # reverse
                indices = indices[::-1]
                maybe_slice = lib.maybe_indices_to_slice(indices, len(target))

                assert isinstance(maybe_slice, slice)
                tm.assert_numpy_array_equal(target[indices], target[maybe_slice])

        # not slice
        indices = np.array([97, 98, 99, 100], dtype=np.int64)
        maybe_slice = lib.maybe_indices_to_slice(indices, len(target))

        assert not isinstance(maybe_slice, slice)
        tm.assert_numpy_array_equal(maybe_slice, indices)

        with pytest.raises(IndexError):
            target[indices]
        with pytest.raises(IndexError):
            target[maybe_slice]

        indices = np.array([100, 99, 98, 97], dtype=np.int64)
        maybe_slice = lib.maybe_indices_to_slice(indices, len(target))

        assert not isinstance(maybe_slice, slice)
        tm.assert_numpy_array_equal(maybe_slice, indices)

        with pytest.raises(IndexError):
            target[indices]
        with pytest.raises(IndexError):
            target[maybe_slice]

        for case in [[99, 97, 99, 96], [99, 99, 98, 97], [98, 98, 97, 96]]:
            indices = np.array(case, dtype=np.int64)
            maybe_slice = lib.maybe_indices_to_slice(indices, len(target))

            assert not isinstance(maybe_slice, slice)
            tm.assert_numpy_array_equal(maybe_slice, indices)
            tm.assert_numpy_array_equal(target[indices], target[maybe_slice])

    def test_maybe_indices_to_slice_both_edges(self):
        target = np.arange(10)

        # slice
        for step in [1, 2, 4, 5, 8, 9]:
            indices = np.arange(0, 9, step, dtype=np.int64)
            maybe_slice = lib.maybe_indices_to_slice(indices, len(target))
            assert isinstance(maybe_slice, slice)
            tm.assert_numpy_array_equal(target[indices], target[maybe_slice])

            # reverse
            indices = indices[::-1]
            maybe_slice = lib.maybe_indices_to_slice(indices, len(target))
            assert isinstance(maybe_slice, slice)
            tm.assert_numpy_array_equal(target[indices], target[maybe_slice])

        # not slice
        for case in [[4, 2, 0, -2], [2, 2, 1, 0], [0, 1, 2, 1]]:
            indices = np.array(case, dtype=np.int64)
            maybe_slice = lib.maybe_indices_to_slice(indices, len(target))
            assert not isinstance(maybe_slice, slice)
            tm.assert_numpy_array_equal(maybe_slice, indices)
            tm.assert_numpy_array_equal(target[indices], target[maybe_slice])

    def test_maybe_indices_to_slice_middle(self):
        target = np.arange(100)

        # slice
        for start, end in [(2, 10), (5, 25), (65, 97)]:
            for step in [1, 2, 4, 20]:
                indices = np.arange(start, end, step, dtype=np.int64)
                maybe_slice = lib.maybe_indices_to_slice(indices, len(target))

                assert isinstance(maybe_slice, slice)
                tm.assert_numpy_array_equal(target[indices], target[maybe_slice])

                # reverse
                indices = indices[::-1]
                maybe_slice = lib.maybe_indices_to_slice(indices, len(target))

                assert isinstance(maybe_slice, slice)
                tm.assert_numpy_array_equal(target[indices], target[maybe_slice])

        # not slice
        for case in [[14, 12, 10, 12], [12, 12, 11, 10], [10, 11, 12, 11]]:
            indices = np.array(case, dtype=np.int64)
            maybe_slice = lib.maybe_indices_to_slice(indices, len(target))

            assert not isinstance(maybe_slice, slice)
            tm.assert_numpy_array_equal(maybe_slice, indices)
            tm.assert_numpy_array_equal(target[indices], target[maybe_slice])

    def test_maybe_booleans_to_slice(self):
        arr = np.array([0, 0, 1, 1, 1, 0, 1], dtype=np.uint8)
        result = lib.maybe_booleans_to_slice(arr)
        assert result.dtype == np.bool_

        result = lib.maybe_booleans_to_slice(arr[:0])
        assert result == slice(0, 0)

    def test_get_reverse_indexer(self):
        indexer = np.array([-1, -1, 1, 2, 0, -1, 3, 4], dtype=np.int64)
        result = lib.get_reverse_indexer(indexer, 5)
        expected = np.array([4, 2, 3, 6, 7], dtype=np.int64)
        tm.assert_numpy_array_equal(result, expected)


def test_cache_readonly_preserve_docstrings():
    # GH18197
    assert Index.hasnans.__doc__ is not None
