"""
Test scalar buffer interface adheres to PEP 3118
"""
import pytest

import numpy as np
from numpy._core._multiarray_tests import get_buffer_info
from numpy._core._rational_tests import rational, rational2
from numpy.testing import assert_, assert_equal, assert_raises

# PEP3118 format strings for native (standard alignment and byteorder) types
scalars_and_codes = [
    (np.bool, '?'),
    (np.byte, 'b'),
    (np.short, 'h'),
    (np.intc, 'i'),
    (np.long, 'l'),
    (np.longlong, 'q'),
    (np.ubyte, 'B'),
    (np.ushort, 'H'),
    (np.uintc, 'I'),
    (np.ulong, 'L'),
    (np.ulonglong, 'Q'),
    (np.half, 'e'),
    (np.single, 'f'),
    (np.double, 'd'),
    (np.longdouble, 'g'),
    (np.csingle, 'Zf'),
    (np.cdouble, 'Zd'),
    (np.clongdouble, 'Zg'),
]
scalars_only, codes_only = zip(*scalars_and_codes)


class TestScalarPEP3118:

    @pytest.mark.parametrize('scalar', scalars_only, ids=codes_only)
    def test_scalar_match_array(self, scalar):
        x = scalar()
        a = np.array([], dtype=np.dtype(scalar))
        mv_x = memoryview(x)
        mv_a = memoryview(a)
        assert_equal(mv_x.format, mv_a.format)

    @pytest.mark.parametrize('scalar', scalars_only, ids=codes_only)
    def test_scalar_dim(self, scalar):
        x = scalar()
        mv_x = memoryview(x)
        assert_equal(mv_x.itemsize, np.dtype(scalar).itemsize)
        assert_equal(mv_x.ndim, 0)
        assert_equal(mv_x.shape, ())
        assert_equal(mv_x.strides, ())
        assert_equal(mv_x.suboffsets, ())

    @pytest.mark.parametrize('scalar, code', scalars_and_codes, ids=codes_only)
    def test_scalar_code_and_properties(self, scalar, code):
        x = scalar()
        expected = {'strides': (), 'itemsize': x.dtype.itemsize, 'ndim': 0,
                        'shape': (), 'format': code, 'readonly': True}

        mv_x = memoryview(x)
        assert self._as_dict(mv_x) == expected

    @pytest.mark.parametrize('scalar', scalars_only, ids=codes_only)
    def test_scalar_buffers_readonly(self, scalar):
        x = scalar()
        with pytest.raises(BufferError, match="scalar buffer is readonly"):
            get_buffer_info(x, ["WRITABLE"])

    def test_void_scalar_structured_data(self):
        dt = np.dtype([('name', np.str_, 16), ('grades', np.float64, (2,))])
        x = np.array(('ndarray_scalar', (1.2, 3.0)), dtype=dt)[()]
        assert_(isinstance(x, np.void))
        mv_x = memoryview(x)
        expected_size = 16 * np.dtype((np.str_, 1)).itemsize
        expected_size += 2 * np.dtype(np.float64).itemsize
        assert_equal(mv_x.itemsize, expected_size)
        assert_equal(mv_x.ndim, 0)
        assert_equal(mv_x.shape, ())
        assert_equal(mv_x.strides, ())
        assert_equal(mv_x.suboffsets, ())

        # check scalar format string against ndarray format string
        a = np.array([('Sarah', (8.0, 7.0)), ('John', (6.0, 7.0))], dtype=dt)
        assert_(isinstance(a, np.ndarray))
        mv_a = memoryview(a)
        assert_equal(mv_x.itemsize, mv_a.itemsize)
        assert_equal(mv_x.format, mv_a.format)

        # Check that we do not allow writeable buffer export (technically
        # we could allow it sometimes here...)
        with pytest.raises(BufferError, match="scalar buffer is readonly"):
            get_buffer_info(x, ["WRITABLE"])

    def _as_dict(self, m):
        return {'strides': m.strides, 'shape': m.shape, 'itemsize': m.itemsize,
                    'ndim': m.ndim, 'format': m.format, 'readonly': m.readonly}

    def test_datetime_memoryview(self):
        # gh-11656
        # Values verified with v1.13.3, shape is not () as in test_scalar_dim

        dt1 = np.datetime64('2016-01-01')
        dt2 = np.datetime64('2017-01-01')
        expected = {'strides': (1,), 'itemsize': 1, 'ndim': 1, 'shape': (8,),
                        'format': 'B', 'readonly': True}
        v = memoryview(dt1)
        assert self._as_dict(v) == expected

        v = memoryview(dt2 - dt1)
        assert self._as_dict(v) == expected

        dt = np.dtype([('a', 'uint16'), ('b', 'M8[s]')])
        a = np.empty(1, dt)
        # Fails to create a PEP 3118 valid buffer
        assert_raises((ValueError, BufferError), memoryview, a[0])

        # Check that we do not allow writeable buffer export
        with pytest.raises(BufferError, match="scalar buffer is readonly"):
            get_buffer_info(dt1, ["WRITABLE"])

    @pytest.mark.parametrize('s', [
        pytest.param("\x32\x32", id="ascii"),
        pytest.param("\uFE0F\uFE0F", id="basic multilingual"),
        pytest.param("\U0001f4bb\U0001f4bb", id="non-BMP"),
    ])
    def test_str_ucs4(self, s):
        s = np.str_(s)  # only our subclass implements the buffer protocol

        # all the same, characters always encode as ucs4
        expected = {'strides': (), 'itemsize': 8, 'ndim': 0, 'shape': (),
                    'format': '2w', 'readonly': True}

        v = memoryview(s)
        assert self._as_dict(v) == expected

        # integers of the platform-appropriate endianness
        code_points = np.frombuffer(v, dtype='i4')

        assert_equal(code_points, [ord(c) for c in s])

        # Check that we do not allow writeable buffer export
        with pytest.raises(BufferError, match="scalar buffer is readonly"):
            get_buffer_info(s, ["WRITABLE"])

    @pytest.mark.parametrize("rat_cls", [rational, rational2])
    def test_user_scalar_fails_buffer(self, rat_cls):
        r = rat_cls(1)
        with assert_raises(TypeError):
            memoryview(r)

        # Check that we do not allow writeable buffer export
        with pytest.raises(BufferError, match="scalar buffer is readonly"):
            get_buffer_info(r, ["WRITABLE"])
