# Licensed to the Apache Software Foundation (ASF) under one
# or more contributor license agreements.  See the NOTICE file
# distributed with this work for additional information
# regarding copyright ownership.  The ASF licenses this file
# to you under the Apache License, Version 2.0 (the
# "License"); you may not use this file except in compliance
# with the License.  You may obtain a copy of the License at
#
#   http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing,
# software distributed under the License is distributed on an
# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
# KIND, either express or implied.  See the License for the
# specific language governing permissions and limitations
# under the License.

import pickle
import weakref
from uuid import uuid4, UUID

import numpy as np
import pyarrow as pa

import pytest


class IntegerType(pa.PyExtensionType):

    def __init__(self):
        pa.PyExtensionType.__init__(self, pa.int64())

    def __reduce__(self):
        return IntegerType, ()


class UuidScalarType(pa.ExtensionScalar):
    def as_py(self):
        return None if self.value is None else UUID(bytes=self.value.as_py())


class UuidType(pa.PyExtensionType):

    def __init__(self):
        pa.PyExtensionType.__init__(self, pa.binary(16))

    def __reduce__(self):
        return UuidType, ()

    def __arrow_ext_scalar_class__(self):
        return UuidScalarType


class UuidType2(pa.PyExtensionType):

    def __init__(self):
        pa.PyExtensionType.__init__(self, pa.binary(16))

    def __reduce__(self):
        return UuidType, ()


class ParamExtType(pa.PyExtensionType):

    def __init__(self, width):
        self._width = width
        pa.PyExtensionType.__init__(self, pa.binary(width))

    @property
    def width(self):
        return self._width

    def __reduce__(self):
        return ParamExtType, (self.width,)


class MyStructType(pa.PyExtensionType):
    storage_type = pa.struct([('left', pa.int64()),
                              ('right', pa.int64())])

    def __init__(self):
        pa.PyExtensionType.__init__(self, self.storage_type)

    def __reduce__(self):
        return MyStructType, ()


class MyListType(pa.PyExtensionType):

    def __init__(self, storage_type):
        pa.PyExtensionType.__init__(self, storage_type)

    def __reduce__(self):
        return MyListType, (self.storage_type,)


class AnnotatedType(pa.PyExtensionType):
    """
    Generic extension type that can store any storage type.
    """

    def __init__(self, storage_type, annotation):
        self.annotation = annotation
        super().__init__(storage_type)

    def __reduce__(self):
        return AnnotatedType, (self.storage_type, self.annotation)


def ipc_write_batch(batch):
    stream = pa.BufferOutputStream()
    writer = pa.RecordBatchStreamWriter(stream, batch.schema)
    writer.write_batch(batch)
    writer.close()
    return stream.getvalue()


def ipc_read_batch(buf):
    reader = pa.RecordBatchStreamReader(buf)
    return reader.read_next_batch()


def test_ext_type_basics():
    ty = UuidType()
    assert ty.extension_name == "arrow.py_extension_type"


def test_ext_type_str():
    ty = IntegerType()
    expected = "extension<arrow.py_extension_type<IntegerType>>"
    assert str(ty) == expected
    assert pa.DataType.__str__(ty) == expected


def test_ext_type_repr():
    ty = IntegerType()
    assert repr(ty) == "IntegerType(DataType(int64))"


def test_ext_type__lifetime():
    ty = UuidType()
    wr = weakref.ref(ty)
    del ty
    assert wr() is None


def test_ext_type__storage_type():
    ty = UuidType()
    assert ty.storage_type == pa.binary(16)
    assert ty.__class__ is UuidType
    ty = ParamExtType(5)
    assert ty.storage_type == pa.binary(5)
    assert ty.__class__ is ParamExtType


def test_ext_type_as_py():
    ty = UuidType()
    expected = uuid4()
    scalar = pa.ExtensionScalar.from_storage(ty, expected.bytes)
    assert scalar.as_py() == expected

    # test array
    uuids = [uuid4() for _ in range(3)]
    storage = pa.array([uuid.bytes for uuid in uuids], type=pa.binary(16))
    arr = pa.ExtensionArray.from_storage(ty, storage)

    # Works for __get_item__
    for i, expected in enumerate(uuids):
        assert arr[i].as_py() == expected

    # Works for __iter__
    for result, expected in zip(arr, uuids):
        assert result.as_py() == expected

    # test chunked array
    data = [
        pa.ExtensionArray.from_storage(ty, storage),
        pa.ExtensionArray.from_storage(ty, storage)
    ]
    carr = pa.chunked_array(data)
    for i, expected in enumerate(uuids + uuids):
        assert carr[i].as_py() == expected

    for result, expected in zip(carr, uuids + uuids):
        assert result.as_py() == expected


def test_uuid_type_pickle():
    for proto in range(0, pickle.HIGHEST_PROTOCOL + 1):
        ty = UuidType()
        ser = pickle.dumps(ty, protocol=proto)
        del ty
        ty = pickle.loads(ser)
        wr = weakref.ref(ty)
        assert ty.extension_name == "arrow.py_extension_type"
        del ty
        assert wr() is None


def test_ext_type_equality():
    a = ParamExtType(5)
    b = ParamExtType(6)
    c = ParamExtType(6)
    assert a != b
    assert b == c
    d = UuidType()
    e = UuidType()
    assert a != d
    assert d == e


def test_ext_array_basics():
    ty = ParamExtType(3)
    storage = pa.array([b"foo", b"bar"], type=pa.binary(3))
    arr = pa.ExtensionArray.from_storage(ty, storage)
    arr.validate()
    assert arr.type is ty
    assert arr.storage.equals(storage)


def test_ext_array_lifetime():
    ty = ParamExtType(3)
    storage = pa.array([b"foo", b"bar"], type=pa.binary(3))
    arr = pa.ExtensionArray.from_storage(ty, storage)

    refs = [weakref.ref(ty), weakref.ref(arr), weakref.ref(storage)]
    del ty, storage, arr
    for ref in refs:
        assert ref() is None


def test_ext_array_to_pylist():
    ty = ParamExtType(3)
    storage = pa.array([b"foo", b"bar", None], type=pa.binary(3))
    arr = pa.ExtensionArray.from_storage(ty, storage)

    assert arr.to_pylist() == [b"foo", b"bar", None]


def test_ext_array_errors():
    ty = ParamExtType(4)
    storage = pa.array([b"foo", b"bar"], type=pa.binary(3))
    with pytest.raises(TypeError, match="Incompatible storage type"):
        pa.ExtensionArray.from_storage(ty, storage)


def test_ext_array_equality():
    storage1 = pa.array([b"0123456789abcdef"], type=pa.binary(16))
    storage2 = pa.array([b"0123456789abcdef"], type=pa.binary(16))
    storage3 = pa.array([], type=pa.binary(16))
    ty1 = UuidType()
    ty2 = ParamExtType(16)

    a = pa.ExtensionArray.from_storage(ty1, storage1)
    b = pa.ExtensionArray.from_storage(ty1, storage2)
    assert a.equals(b)
    c = pa.ExtensionArray.from_storage(ty1, storage3)
    assert not a.equals(c)
    d = pa.ExtensionArray.from_storage(ty2, storage1)
    assert not a.equals(d)
    e = pa.ExtensionArray.from_storage(ty2, storage2)
    assert d.equals(e)
    f = pa.ExtensionArray.from_storage(ty2, storage3)
    assert not d.equals(f)


def test_ext_array_wrap_array():
    ty = ParamExtType(3)
    storage = pa.array([b"foo", b"bar", None], type=pa.binary(3))
    arr = ty.wrap_array(storage)
    arr.validate(full=True)
    assert isinstance(arr, pa.ExtensionArray)
    assert arr.type == ty
    assert arr.storage == storage

    storage = pa.chunked_array([[b"abc", b"def"], [b"ghi"]],
                               type=pa.binary(3))
    arr = ty.wrap_array(storage)
    arr.validate(full=True)
    assert isinstance(arr, pa.ChunkedArray)
    assert arr.type == ty
    assert arr.chunk(0).storage == storage.chunk(0)
    assert arr.chunk(1).storage == storage.chunk(1)

    # Wrong storage type
    storage = pa.array([b"foo", b"bar", None])
    with pytest.raises(TypeError, match="Incompatible storage type"):
        ty.wrap_array(storage)

    # Not an array or chunked array
    with pytest.raises(TypeError, match="Expected array or chunked array"):
        ty.wrap_array(None)


def test_ext_scalar_from_array():
    data = [b"0123456789abcdef", b"0123456789abcdef",
            b"zyxwvutsrqponmlk", None]
    storage = pa.array(data, type=pa.binary(16))
    ty1 = UuidType()
    ty2 = ParamExtType(16)
    ty3 = UuidType2()

    a = pa.ExtensionArray.from_storage(ty1, storage)
    b = pa.ExtensionArray.from_storage(ty2, storage)
    c = pa.ExtensionArray.from_storage(ty3, storage)

    scalars_a = list(a)
    assert len(scalars_a) == 4

    assert ty1.__arrow_ext_scalar_class__() == UuidScalarType
    assert type(a[0]) == UuidScalarType
    assert type(scalars_a[0]) == UuidScalarType

    for s, val in zip(scalars_a, data):
        assert isinstance(s, pa.ExtensionScalar)
        assert s.is_valid == (val is not None)
        assert s.type == ty1
        if val is not None:
            assert s.value == pa.scalar(val, storage.type)
            assert s.as_py() == UUID(bytes=val)
        else:
            assert s.value is None

    scalars_b = list(b)
    assert len(scalars_b) == 4

    for sa, sb in zip(scalars_a, scalars_b):
        assert isinstance(sb, pa.ExtensionScalar)
        assert sa.is_valid == sb.is_valid
        if sa.as_py() is None:
            assert sa.as_py() == sb.as_py()
        else:
            assert sa.as_py().bytes == sb.as_py()
        assert sa != sb

    scalars_c = list(c)
    assert len(scalars_c) == 4

    for s, val in zip(scalars_c, data):
        assert isinstance(s, pa.ExtensionScalar)
        assert s.is_valid == (val is not None)
        assert s.type == ty3
        if val is not None:
            assert s.value == pa.scalar(val, storage.type)
            assert s.as_py() == val
        else:
            assert s.value is None

    assert a.to_pylist() == [UUID(bytes=x) if x else None for x in data]


def test_ext_scalar_from_storage():
    ty = UuidType()

    s = pa.ExtensionScalar.from_storage(ty, None)
    assert isinstance(s, pa.ExtensionScalar)
    assert s.type == ty
    assert s.is_valid is False
    assert s.value is None

    s = pa.ExtensionScalar.from_storage(ty, b"0123456789abcdef")
    assert isinstance(s, pa.ExtensionScalar)
    assert s.type == ty
    assert s.is_valid is True
    assert s.value == pa.scalar(b"0123456789abcdef", ty.storage_type)

    s = pa.ExtensionScalar.from_storage(ty, pa.scalar(None, ty.storage_type))
    assert isinstance(s, pa.ExtensionScalar)
    assert s.type == ty
    assert s.is_valid is False
    assert s.value is None

    s = pa.ExtensionScalar.from_storage(
        ty, pa.scalar(b"0123456789abcdef", ty.storage_type))
    assert isinstance(s, pa.ExtensionScalar)
    assert s.type == ty
    assert s.is_valid is True
    assert s.value == pa.scalar(b"0123456789abcdef", ty.storage_type)


def test_ext_array_pickling():
    for proto in range(0, pickle.HIGHEST_PROTOCOL + 1):
        ty = ParamExtType(3)
        storage = pa.array([b"foo", b"bar"], type=pa.binary(3))
        arr = pa.ExtensionArray.from_storage(ty, storage)
        ser = pickle.dumps(arr, protocol=proto)
        del ty, storage, arr
        arr = pickle.loads(ser)
        arr.validate()
        assert isinstance(arr, pa.ExtensionArray)
        assert arr.type == ParamExtType(3)
        assert arr.type.storage_type == pa.binary(3)
        assert arr.storage.type == pa.binary(3)
        assert arr.storage.to_pylist() == [b"foo", b"bar"]


def test_ext_array_conversion_to_numpy():
    storage1 = pa.array([1, 2, 3], type=pa.int64())
    storage2 = pa.array([b"123", b"456", b"789"], type=pa.binary(3))
    ty1 = IntegerType()
    ty2 = ParamExtType(3)

    arr1 = pa.ExtensionArray.from_storage(ty1, storage1)
    arr2 = pa.ExtensionArray.from_storage(ty2, storage2)

    result = arr1.to_numpy()
    expected = np.array([1, 2, 3], dtype="int64")
    np.testing.assert_array_equal(result, expected)

    with pytest.raises(ValueError, match="zero_copy_only was True"):
        arr2.to_numpy()
    result = arr2.to_numpy(zero_copy_only=False)
    expected = np.array([b"123", b"456", b"789"])
    np.testing.assert_array_equal(result, expected)


@pytest.mark.pandas
def test_ext_array_conversion_to_pandas():
    import pandas as pd

    storage1 = pa.array([1, 2, 3], type=pa.int64())
    storage2 = pa.array([b"123", b"456", b"789"], type=pa.binary(3))
    ty1 = IntegerType()
    ty2 = ParamExtType(3)

    arr1 = pa.ExtensionArray.from_storage(ty1, storage1)
    arr2 = pa.ExtensionArray.from_storage(ty2, storage2)

    result = arr1.to_pandas()
    expected = pd.Series([1, 2, 3], dtype="int64")
    pd.testing.assert_series_equal(result, expected)

    result = arr2.to_pandas()
    expected = pd.Series([b"123", b"456", b"789"], dtype=object)
    pd.testing.assert_series_equal(result, expected)


@pytest.fixture
def struct_w_ext_data():
    storage1 = pa.array([1, 2, 3], type=pa.int64())
    storage2 = pa.array([b"123", b"456", b"789"], type=pa.binary(3))
    ty1 = IntegerType()
    ty2 = ParamExtType(3)

    arr1 = pa.ExtensionArray.from_storage(ty1, storage1)
    arr2 = pa.ExtensionArray.from_storage(ty2, storage2)

    sarr1 = pa.StructArray.from_arrays([arr1], ["f0"])
    sarr2 = pa.StructArray.from_arrays([arr2], ["f1"])

    return [sarr1, sarr2]


def test_struct_w_ext_array_to_numpy(struct_w_ext_data):
    # ARROW-15291
    # Check that we don't segfault when trying to build
    # a numpy array from a StructArray with a field being
    # an ExtensionArray

    result = struct_w_ext_data[0].to_numpy(zero_copy_only=False)
    expected = np.array([{'f0': 1}, {'f0': 2},
                         {'f0': 3}], dtype=object)
    np.testing.assert_array_equal(result, expected)

    result = struct_w_ext_data[1].to_numpy(zero_copy_only=False)
    expected = np.array([{'f1': b'123'}, {'f1': b'456'},
                         {'f1': b'789'}], dtype=object)
    np.testing.assert_array_equal(result, expected)


@pytest.mark.pandas
def test_struct_w_ext_array_to_pandas(struct_w_ext_data):
    # ARROW-15291
    # Check that we don't segfault when trying to build
    # a Pandas dataframe from a StructArray with a field
    # being an ExtensionArray
    import pandas as pd

    result = struct_w_ext_data[0].to_pandas()
    expected = pd.Series([{'f0': 1}, {'f0': 2},
                         {'f0': 3}], dtype=object)
    pd.testing.assert_series_equal(result, expected)

    result = struct_w_ext_data[1].to_pandas()
    expected = pd.Series([{'f1': b'123'}, {'f1': b'456'},
                         {'f1': b'789'}], dtype=object)
    pd.testing.assert_series_equal(result, expected)


def test_cast_kernel_on_extension_arrays():
    # test array casting
    storage = pa.array([1, 2, 3, 4], pa.int64())
    arr = pa.ExtensionArray.from_storage(IntegerType(), storage)

    # test that no allocation happens during identity cast
    allocated_before_cast = pa.total_allocated_bytes()
    casted = arr.cast(pa.int64())
    assert pa.total_allocated_bytes() == allocated_before_cast

    cases = [
        (pa.int64(), pa.Int64Array),
        (pa.int32(), pa.Int32Array),
        (pa.int16(), pa.Int16Array),
        (pa.uint64(), pa.UInt64Array),
        (pa.uint32(), pa.UInt32Array),
        (pa.uint16(), pa.UInt16Array)
    ]
    for typ, klass in cases:
        casted = arr.cast(typ)
        assert casted.type == typ
        assert isinstance(casted, klass)

    # test chunked array casting
    arr = pa.chunked_array([arr, arr])
    casted = arr.cast(pa.int16())
    assert casted.type == pa.int16()
    assert isinstance(casted, pa.ChunkedArray)


def test_casting_to_extension_type_raises():
    arr = pa.array([1, 2, 3, 4], pa.int64())
    with pytest.raises(pa.ArrowNotImplementedError):
        arr.cast(IntegerType())


def test_null_storage_type():
    ext_type = AnnotatedType(pa.null(), {"key": "value"})
    storage = pa.array([None] * 10, pa.null())
    arr = pa.ExtensionArray.from_storage(ext_type, storage)
    assert arr.null_count == 10
    arr.validate(full=True)


def example_batch():
    ty = ParamExtType(3)
    storage = pa.array([b"foo", b"bar"], type=pa.binary(3))
    arr = pa.ExtensionArray.from_storage(ty, storage)
    return pa.RecordBatch.from_arrays([arr], ["exts"])


def check_example_batch(batch):
    arr = batch.column(0)
    assert isinstance(arr, pa.ExtensionArray)
    assert arr.type.storage_type == pa.binary(3)
    assert arr.storage.to_pylist() == [b"foo", b"bar"]
    return arr


def test_ipc():
    batch = example_batch()
    buf = ipc_write_batch(batch)
    del batch

    batch = ipc_read_batch(buf)
    arr = check_example_batch(batch)
    assert arr.type == ParamExtType(3)


def test_ipc_unknown_type():
    batch = example_batch()
    buf = ipc_write_batch(batch)
    del batch

    orig_type = ParamExtType
    try:
        # Simulate the original Python type being unavailable.
        # Deserialization should not fail but return a placeholder type.
        del globals()['ParamExtType']

        batch = ipc_read_batch(buf)
        arr = check_example_batch(batch)
        assert isinstance(arr.type, pa.UnknownExtensionType)

        # Can be serialized again
        buf2 = ipc_write_batch(batch)
        del batch, arr

        batch = ipc_read_batch(buf2)
        arr = check_example_batch(batch)
        assert isinstance(arr.type, pa.UnknownExtensionType)
    finally:
        globals()['ParamExtType'] = orig_type

    # Deserialize again with the type restored
    batch = ipc_read_batch(buf2)
    arr = check_example_batch(batch)
    assert arr.type == ParamExtType(3)


class PeriodArray(pa.ExtensionArray):
    pass


class PeriodType(pa.ExtensionType):
    def __init__(self, freq):
        # attributes need to be set first before calling
        # super init (as that calls serialize)
        self._freq = freq
        pa.ExtensionType.__init__(self, pa.int64(), 'test.period')

    @property
    def freq(self):
        return self._freq

    def __arrow_ext_serialize__(self):
        return "freq={}".format(self.freq).encode()

    @classmethod
    def __arrow_ext_deserialize__(cls, storage_type, serialized):
        serialized = serialized.decode()
        assert serialized.startswith("freq=")
        freq = serialized.split('=')[1]
        return PeriodType(freq)

    def __eq__(self, other):
        if isinstance(other, pa.BaseExtensionType):
            return (type(self) == type(other) and
                    self.freq == other.freq)
        else:
            return NotImplemented


class PeriodTypeWithClass(PeriodType):
    def __init__(self, freq):
        PeriodType.__init__(self, freq)

    def __arrow_ext_class__(self):
        return PeriodArray

    @classmethod
    def __arrow_ext_deserialize__(cls, storage_type, serialized):
        freq = PeriodType.__arrow_ext_deserialize__(
            storage_type, serialized).freq
        return PeriodTypeWithClass(freq)


@pytest.fixture(params=[PeriodType('D'), PeriodTypeWithClass('D')])
def registered_period_type(request):
    # setup
    period_type = request.param
    period_class = period_type.__arrow_ext_class__()
    pa.register_extension_type(period_type)
    yield period_type, period_class
    # teardown
    try:
        pa.unregister_extension_type('test.period')
    except KeyError:
        pass


def test_generic_ext_type():
    period_type = PeriodType('D')
    assert period_type.extension_name == "test.period"
    assert period_type.storage_type == pa.int64()
    # default ext_class expected.
    assert period_type.__arrow_ext_class__() == pa.ExtensionArray


def test_generic_ext_type_ipc(registered_period_type):
    period_type, period_class = registered_period_type
    storage = pa.array([1, 2, 3, 4], pa.int64())
    arr = pa.ExtensionArray.from_storage(period_type, storage)
    batch = pa.RecordBatch.from_arrays([arr], ["ext"])
    # check the built array has exactly the expected clss
    assert type(arr) == period_class

    buf = ipc_write_batch(batch)
    del batch
    batch = ipc_read_batch(buf)

    result = batch.column(0)
    # check the deserialized array class is the expected one
    assert type(result) == period_class
    assert result.type.extension_name == "test.period"
    assert arr.storage.to_pylist() == [1, 2, 3, 4]

    # we get back an actual PeriodType
    assert isinstance(result.type, PeriodType)
    assert result.type.freq == 'D'
    assert result.type == period_type

    # using different parametrization as how it was registered
    period_type_H = period_type.__class__('H')
    assert period_type_H.extension_name == "test.period"
    assert period_type_H.freq == 'H'

    arr = pa.ExtensionArray.from_storage(period_type_H, storage)
    batch = pa.RecordBatch.from_arrays([arr], ["ext"])

    buf = ipc_write_batch(batch)
    del batch
    batch = ipc_read_batch(buf)
    result = batch.column(0)
    assert isinstance(result.type, PeriodType)
    assert result.type.freq == 'H'
    assert type(result) == period_class


def test_generic_ext_type_ipc_unknown(registered_period_type):
    period_type, _ = registered_period_type
    storage = pa.array([1, 2, 3, 4], pa.int64())
    arr = pa.ExtensionArray.from_storage(period_type, storage)
    batch = pa.RecordBatch.from_arrays([arr], ["ext"])

    buf = ipc_write_batch(batch)
    del batch

    # unregister type before loading again => reading unknown extension type
    # as plain array (but metadata in schema's field are preserved)
    pa.unregister_extension_type('test.period')

    batch = ipc_read_batch(buf)
    result = batch.column(0)

    assert isinstance(result, pa.Int64Array)
    ext_field = batch.schema.field('ext')
    assert ext_field.metadata == {
        b'ARROW:extension:metadata': b'freq=D',
        b'ARROW:extension:name': b'test.period'
    }


def test_generic_ext_type_equality():
    period_type = PeriodType('D')
    assert period_type.extension_name == "test.period"

    period_type2 = PeriodType('D')
    period_type3 = PeriodType('H')
    assert period_type == period_type2
    assert not period_type == period_type3


def test_generic_ext_type_register(registered_period_type):
    # test that trying to register other type does not segfault
    with pytest.raises(TypeError):
        pa.register_extension_type(pa.string())

    # register second time raises KeyError
    period_type = PeriodType('D')
    with pytest.raises(KeyError):
        pa.register_extension_type(period_type)


@pytest.mark.parquet
def test_parquet_period(tmpdir, registered_period_type):
    # Parquet support for primitive extension types
    period_type, period_class = registered_period_type
    storage = pa.array([1, 2, 3, 4], pa.int64())
    arr = pa.ExtensionArray.from_storage(period_type, storage)
    table = pa.table([arr], names=["ext"])

    import pyarrow.parquet as pq

    filename = tmpdir / 'period_extension_type.parquet'
    pq.write_table(table, filename)

    # Stored in parquet as storage type but with extension metadata saved
    # in the serialized arrow schema
    meta = pq.read_metadata(filename)
    assert meta.schema.column(0).physical_type == "INT64"
    assert b"ARROW:schema" in meta.metadata

    import base64
    decoded_schema = base64.b64decode(meta.metadata[b"ARROW:schema"])
    schema = pa.ipc.read_schema(pa.BufferReader(decoded_schema))
    # Since the type could be reconstructed, the extension type metadata is
    # absent.
    assert schema.field("ext").metadata == {}

    # When reading in, properly create extension type if it is registered
    result = pq.read_table(filename)
    assert result.schema.field("ext").type == period_type
    assert result.schema.field("ext").metadata == {}
    # Get the exact array class defined by the registered type.
    result_array = result.column("ext").chunk(0)
    assert type(result_array) is period_class

    # When the type is not registered, read in as storage type
    pa.unregister_extension_type(period_type.extension_name)
    result = pq.read_table(filename)
    assert result.schema.field("ext").type == pa.int64()
    # The extension metadata is present for roundtripping.
    assert result.schema.field("ext").metadata == {
        b'ARROW:extension:metadata': b'freq=D',
        b'ARROW:extension:name': b'test.period'
    }


@pytest.mark.parquet
def test_parquet_extension_with_nested_storage(tmpdir):
    # Parquet support for extension types with nested storage type
    import pyarrow.parquet as pq

    struct_array = pa.StructArray.from_arrays(
        [pa.array([0, 1], type="int64"), pa.array([4, 5], type="int64")],
        names=["left", "right"])
    list_array = pa.array([[1, 2, 3], [4, 5]], type=pa.list_(pa.int32()))

    mystruct_array = pa.ExtensionArray.from_storage(MyStructType(),
                                                    struct_array)
    mylist_array = pa.ExtensionArray.from_storage(
        MyListType(list_array.type), list_array)

    orig_table = pa.table({'structs': mystruct_array,
                           'lists': mylist_array})
    filename = tmpdir / 'nested_extension_storage.parquet'
    pq.write_table(orig_table, filename)

    table = pq.read_table(filename)
    assert table.column('structs').type == mystruct_array.type
    assert table.column('lists').type == mylist_array.type
    assert table == orig_table


@pytest.mark.parquet
def test_parquet_nested_extension(tmpdir):
    # Parquet support for extension types nested in struct or list
    import pyarrow.parquet as pq

    ext_type = IntegerType()
    storage = pa.array([4, 5, 6, 7], type=pa.int64())
    ext_array = pa.ExtensionArray.from_storage(ext_type, storage)

    # Struct of extensions
    struct_array = pa.StructArray.from_arrays(
        [storage, ext_array],
        names=['ints', 'exts'])

    orig_table = pa.table({'structs': struct_array})
    filename = tmpdir / 'struct_of_ext.parquet'
    pq.write_table(orig_table, filename)

    table = pq.read_table(filename)
    assert table.column(0).type == struct_array.type
    assert table == orig_table

    # List of extensions
    list_array = pa.ListArray.from_arrays([0, 1, None, 3], ext_array)

    orig_table = pa.table({'lists': list_array})
    filename = tmpdir / 'list_of_ext.parquet'
    pq.write_table(orig_table, filename)

    table = pq.read_table(filename)
    assert table.column(0).type == list_array.type
    assert table == orig_table

    # Large list of extensions
    list_array = pa.LargeListArray.from_arrays([0, 1, None, 3], ext_array)

    orig_table = pa.table({'lists': list_array})
    filename = tmpdir / 'list_of_ext.parquet'
    pq.write_table(orig_table, filename)

    table = pq.read_table(filename)
    assert table.column(0).type == list_array.type
    assert table == orig_table


@pytest.mark.parquet
def test_parquet_extension_nested_in_extension(tmpdir):
    # Parquet support for extension<list<extension>>
    import pyarrow.parquet as pq

    inner_ext_type = IntegerType()
    inner_storage = pa.array([4, 5, 6, 7], type=pa.int64())
    inner_ext_array = pa.ExtensionArray.from_storage(inner_ext_type,
                                                     inner_storage)

    list_array = pa.ListArray.from_arrays([0, 1, None, 3], inner_ext_array)
    mylist_array = pa.ExtensionArray.from_storage(
        MyListType(list_array.type), list_array)

    orig_table = pa.table({'lists': mylist_array})
    filename = tmpdir / 'ext_of_list_of_ext.parquet'
    pq.write_table(orig_table, filename)

    table = pq.read_table(filename)
    assert table.column(0).type == mylist_array.type
    assert table == orig_table


def test_to_numpy():
    period_type = PeriodType('D')
    storage = pa.array([1, 2, 3, 4], pa.int64())
    arr = pa.ExtensionArray.from_storage(period_type, storage)

    expected = storage.to_numpy()
    result = arr.to_numpy()
    np.testing.assert_array_equal(result, expected)

    result = np.asarray(arr)
    np.testing.assert_array_equal(result, expected)

    # chunked array
    a1 = pa.chunked_array([arr, arr])
    a2 = pa.chunked_array([arr, arr], type=period_type)
    expected = np.hstack([expected, expected])

    for charr in [a1, a2]:
        assert charr.type == period_type
        for result in [np.asarray(charr), charr.to_numpy()]:
            assert result.dtype == np.int64
            np.testing.assert_array_equal(result, expected)

    # zero chunks
    charr = pa.chunked_array([], type=period_type)
    assert charr.type == period_type

    for result in [np.asarray(charr), charr.to_numpy()]:
        assert result.dtype == np.int64
        np.testing.assert_array_equal(result, np.array([], dtype='int64'))


def test_empty_take():
    # https://issues.apache.org/jira/browse/ARROW-13474
    ext_type = IntegerType()
    storage = pa.array([], type=pa.int64())
    empty_arr = pa.ExtensionArray.from_storage(ext_type, storage)

    result = empty_arr.filter(pa.array([], pa.bool_()))
    assert len(result) == 0
    assert result.equals(empty_arr)

    result = empty_arr.take(pa.array([], pa.int32()))
    assert len(result) == 0
    assert result.equals(empty_arr)
