# Copyright 2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License"). You
# may not use this file except in compliance with the License. A copy of
# the License is located at
#
# http://aws.amazon.com/apache2.0/
#
# or in the "license" file accompanying this file. This file 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 copy
import os
import shutil
import tempfile
from io import BytesIO

from s3transfer.bandwidth import BandwidthLimiter
from s3transfer.compat import SOCKET_ERROR
from s3transfer.download import (
    CompleteDownloadNOOPTask,
    DeferQueue,
    DownloadChunkIterator,
    DownloadFilenameOutputManager,
    DownloadNonSeekableOutputManager,
    DownloadSeekableOutputManager,
    DownloadSpecialFilenameOutputManager,
    DownloadSubmissionTask,
    GetObjectTask,
    ImmediatelyWriteIOGetObjectTask,
    IOCloseTask,
    IORenameFileTask,
    IOStreamingWriteTask,
    IOWriteTask,
)
from s3transfer.exceptions import RetriesExceededError
from s3transfer.futures import IN_MEMORY_DOWNLOAD_TAG, BoundedExecutor
from s3transfer.utils import CallArgs, OSUtils
from tests import (
    BaseSubmissionTaskTest,
    BaseTaskTest,
    FileCreator,
    NonSeekableWriter,
    RecordingExecutor,
    StreamWithError,
    mock,
    unittest,
)


class DownloadException(Exception):
    pass


class WriteCollector:
    """A utility to collect information about writes and seeks"""

    def __init__(self):
        self._pos = 0
        self.writes = []

    def seek(self, pos, whence=0):
        self._pos = pos

    def write(self, data):
        self.writes.append((self._pos, data))
        self._pos += len(data)


class AlwaysIndicatesSpecialFileOSUtils(OSUtils):
    """OSUtil that always returns True for is_special_file"""

    def is_special_file(self, filename):
        return True


class CancelledStreamWrapper:
    """A wrapper to trigger a cancellation while stream reading

    Forces the transfer coordinator to cancel after a certain amount of reads
    :param stream: The underlying stream to read from
    :param transfer_coordinator: The coordinator for the transfer
    :param num_reads: On which read to signal a cancellation. 0 is the first
        read.
    """

    def __init__(self, stream, transfer_coordinator, num_reads=0):
        self._stream = stream
        self._transfer_coordinator = transfer_coordinator
        self._num_reads = num_reads
        self._count = 0

    def read(self, *args, **kwargs):
        if self._num_reads == self._count:
            self._transfer_coordinator.cancel()
        self._stream.read(*args, **kwargs)
        self._count += 1


class BaseDownloadOutputManagerTest(BaseTaskTest):
    def setUp(self):
        super().setUp()
        self.osutil = OSUtils()

        # Create a file to write to
        self.tempdir = tempfile.mkdtemp()
        self.filename = os.path.join(self.tempdir, 'myfile')

        self.call_args = CallArgs(fileobj=self.filename)
        self.future = self.get_transfer_future(self.call_args)
        self.io_executor = BoundedExecutor(1000, 1)

    def tearDown(self):
        super().tearDown()
        shutil.rmtree(self.tempdir)


class TestDownloadFilenameOutputManager(BaseDownloadOutputManagerTest):
    def setUp(self):
        super().setUp()
        self.download_output_manager = DownloadFilenameOutputManager(
            self.osutil,
            self.transfer_coordinator,
            io_executor=self.io_executor,
        )

    def test_is_compatible(self):
        self.assertTrue(
            self.download_output_manager.is_compatible(
                self.filename, self.osutil
            )
        )

    def test_get_download_task_tag(self):
        self.assertIsNone(self.download_output_manager.get_download_task_tag())

    def test_get_fileobj_for_io_writes(self):
        with self.download_output_manager.get_fileobj_for_io_writes(
            self.future
        ) as f:
            # Ensure it is a file like object returned
            self.assertTrue(hasattr(f, 'read'))
            self.assertTrue(hasattr(f, 'seek'))
            # Make sure the name of the file returned is not the same as the
            # final filename as we should be writing to a temporary file.
            self.assertNotEqual(f.name, self.filename)

    def test_get_final_io_task(self):
        ref_contents = b'my_contents'
        with self.download_output_manager.get_fileobj_for_io_writes(
            self.future
        ) as f:
            temp_filename = f.name
            # Write some data to test that the data gets moved over to the
            # final location.
            f.write(ref_contents)
            final_task = self.download_output_manager.get_final_io_task()
            # Make sure it is the appropriate task.
            self.assertIsInstance(final_task, IORenameFileTask)
            final_task()
            # Make sure the temp_file gets removed
            self.assertFalse(os.path.exists(temp_filename))
        # Make sure what ever was written to the temp file got moved to
        # the final filename
        with open(self.filename, 'rb') as f:
            self.assertEqual(f.read(), ref_contents)

    def test_can_queue_file_io_task(self):
        fileobj = WriteCollector()
        self.download_output_manager.queue_file_io_task(
            fileobj=fileobj, data='foo', offset=0
        )
        self.download_output_manager.queue_file_io_task(
            fileobj=fileobj, data='bar', offset=3
        )
        self.io_executor.shutdown()
        self.assertEqual(fileobj.writes, [(0, 'foo'), (3, 'bar')])

    def test_get_file_io_write_task(self):
        fileobj = WriteCollector()
        io_write_task = self.download_output_manager.get_io_write_task(
            fileobj=fileobj, data='foo', offset=3
        )
        self.assertIsInstance(io_write_task, IOWriteTask)

        io_write_task()
        self.assertEqual(fileobj.writes, [(3, 'foo')])


class TestDownloadSpecialFilenameOutputManager(BaseDownloadOutputManagerTest):
    def setUp(self):
        super().setUp()
        self.osutil = AlwaysIndicatesSpecialFileOSUtils()
        self.download_output_manager = DownloadSpecialFilenameOutputManager(
            self.osutil,
            self.transfer_coordinator,
            io_executor=self.io_executor,
        )

    def test_is_compatible_for_special_file(self):
        self.assertTrue(
            self.download_output_manager.is_compatible(
                self.filename, AlwaysIndicatesSpecialFileOSUtils()
            )
        )

    def test_is_not_compatible_for_non_special_file(self):
        self.assertFalse(
            self.download_output_manager.is_compatible(
                self.filename, OSUtils()
            )
        )

    def test_get_fileobj_for_io_writes(self):
        with self.download_output_manager.get_fileobj_for_io_writes(
            self.future
        ) as f:
            # Ensure it is a file like object returned
            self.assertTrue(hasattr(f, 'read'))
            # Make sure the name of the file returned is the same as the
            # final filename as we should not be writing to a temporary file.
            self.assertEqual(f.name, self.filename)

    def test_get_final_io_task(self):
        self.assertIsInstance(
            self.download_output_manager.get_final_io_task(), IOCloseTask
        )

    def test_can_queue_file_io_task(self):
        fileobj = WriteCollector()
        self.download_output_manager.queue_file_io_task(
            fileobj=fileobj, data='foo', offset=0
        )
        self.download_output_manager.queue_file_io_task(
            fileobj=fileobj, data='bar', offset=3
        )
        self.io_executor.shutdown()
        self.assertEqual(fileobj.writes, [(0, 'foo'), (3, 'bar')])


class TestDownloadSeekableOutputManager(BaseDownloadOutputManagerTest):
    def setUp(self):
        super().setUp()
        self.download_output_manager = DownloadSeekableOutputManager(
            self.osutil,
            self.transfer_coordinator,
            io_executor=self.io_executor,
        )

        # Create a fileobj to write to
        self.fileobj = open(self.filename, 'wb')

        self.call_args = CallArgs(fileobj=self.fileobj)
        self.future = self.get_transfer_future(self.call_args)

    def tearDown(self):
        self.fileobj.close()
        super().tearDown()

    def test_is_compatible(self):
        self.assertTrue(
            self.download_output_manager.is_compatible(
                self.fileobj, self.osutil
            )
        )

    def test_is_compatible_bytes_io(self):
        self.assertTrue(
            self.download_output_manager.is_compatible(BytesIO(), self.osutil)
        )

    def test_not_compatible_for_non_filelike_obj(self):
        self.assertFalse(
            self.download_output_manager.is_compatible(object(), self.osutil)
        )

    def test_get_download_task_tag(self):
        self.assertIsNone(self.download_output_manager.get_download_task_tag())

    def test_get_fileobj_for_io_writes(self):
        self.assertIs(
            self.download_output_manager.get_fileobj_for_io_writes(
                self.future
            ),
            self.fileobj,
        )

    def test_get_final_io_task(self):
        self.assertIsInstance(
            self.download_output_manager.get_final_io_task(),
            CompleteDownloadNOOPTask,
        )

    def test_can_queue_file_io_task(self):
        fileobj = WriteCollector()
        self.download_output_manager.queue_file_io_task(
            fileobj=fileobj, data='foo', offset=0
        )
        self.download_output_manager.queue_file_io_task(
            fileobj=fileobj, data='bar', offset=3
        )
        self.io_executor.shutdown()
        self.assertEqual(fileobj.writes, [(0, 'foo'), (3, 'bar')])

    def test_get_file_io_write_task(self):
        fileobj = WriteCollector()
        io_write_task = self.download_output_manager.get_io_write_task(
            fileobj=fileobj, data='foo', offset=3
        )
        self.assertIsInstance(io_write_task, IOWriteTask)

        io_write_task()
        self.assertEqual(fileobj.writes, [(3, 'foo')])


class TestDownloadNonSeekableOutputManager(BaseDownloadOutputManagerTest):
    def setUp(self):
        super().setUp()
        self.download_output_manager = DownloadNonSeekableOutputManager(
            self.osutil, self.transfer_coordinator, io_executor=None
        )

    def test_is_compatible_with_seekable_stream(self):
        with open(self.filename, 'wb') as f:
            self.assertTrue(
                self.download_output_manager.is_compatible(f, self.osutil)
            )

    def test_not_compatible_with_filename(self):
        self.assertFalse(
            self.download_output_manager.is_compatible(
                self.filename, self.osutil
            )
        )

    def test_compatible_with_non_seekable_stream(self):
        class NonSeekable:
            def write(self, data):
                pass

        f = NonSeekable()
        self.assertTrue(
            self.download_output_manager.is_compatible(f, self.osutil)
        )

    def test_is_compatible_with_bytesio(self):
        self.assertTrue(
            self.download_output_manager.is_compatible(BytesIO(), self.osutil)
        )

    def test_get_download_task_tag(self):
        self.assertIs(
            self.download_output_manager.get_download_task_tag(),
            IN_MEMORY_DOWNLOAD_TAG,
        )

    def test_submit_writes_from_internal_queue(self):
        class FakeQueue:
            def request_writes(self, offset, data):
                return [
                    {'offset': 0, 'data': 'foo'},
                    {'offset': 3, 'data': 'bar'},
                ]

        q = FakeQueue()
        io_executor = BoundedExecutor(1000, 1)
        manager = DownloadNonSeekableOutputManager(
            self.osutil,
            self.transfer_coordinator,
            io_executor=io_executor,
            defer_queue=q,
        )
        fileobj = WriteCollector()
        manager.queue_file_io_task(fileobj=fileobj, data='foo', offset=1)
        io_executor.shutdown()
        self.assertEqual(fileobj.writes, [(0, 'foo'), (3, 'bar')])

    def test_get_file_io_write_task(self):
        fileobj = WriteCollector()
        io_write_task = self.download_output_manager.get_io_write_task(
            fileobj=fileobj, data='foo', offset=1
        )
        self.assertIsInstance(io_write_task, IOStreamingWriteTask)

        io_write_task()
        self.assertEqual(fileobj.writes, [(0, 'foo')])


class TestDownloadSubmissionTask(BaseSubmissionTaskTest):
    def setUp(self):
        super().setUp()
        self.tempdir = tempfile.mkdtemp()
        self.filename = os.path.join(self.tempdir, 'myfile')

        self.bucket = 'mybucket'
        self.key = 'mykey'
        self.extra_args = {}
        self.subscribers = []

        # Create a stream to read from
        self.content = b'my content'
        self.stream = BytesIO(self.content)

        # A list to keep track of all of the bodies sent over the wire
        # and their order.

        self.call_args = self.get_call_args()
        self.transfer_future = self.get_transfer_future(self.call_args)
        self.io_executor = BoundedExecutor(1000, 1)
        self.submission_main_kwargs = {
            'client': self.client,
            'config': self.config,
            'osutil': self.osutil,
            'request_executor': self.executor,
            'io_executor': self.io_executor,
            'transfer_future': self.transfer_future,
        }
        self.submission_task = self.get_download_submission_task()

    def tearDown(self):
        super().tearDown()
        shutil.rmtree(self.tempdir)

    def get_call_args(self, **kwargs):
        default_call_args = {
            'fileobj': self.filename,
            'bucket': self.bucket,
            'key': self.key,
            'extra_args': self.extra_args,
            'subscribers': self.subscribers,
        }
        default_call_args.update(kwargs)
        return CallArgs(**default_call_args)

    def wrap_executor_in_recorder(self):
        self.executor = RecordingExecutor(self.executor)
        self.submission_main_kwargs['request_executor'] = self.executor

    def use_fileobj_in_call_args(self, fileobj):
        self.call_args = self.get_call_args(fileobj=fileobj)
        self.transfer_future = self.get_transfer_future(self.call_args)
        self.submission_main_kwargs['transfer_future'] = self.transfer_future

    def assert_tag_for_get_object(self, tag_value):
        submissions_to_compare = self.executor.submissions
        if len(submissions_to_compare) > 1:
            # If it was ranged get, make sure we do not include the join task.
            submissions_to_compare = submissions_to_compare[:-1]
        for submission in submissions_to_compare:
            self.assertEqual(submission['tag'], tag_value)

    def add_head_object_response(self):
        self.stubber.add_response(
            'head_object', {'ContentLength': len(self.content)}
        )

    def add_get_responses(self):
        chunksize = self.config.multipart_chunksize
        for i in range(0, len(self.content), chunksize):
            if i + chunksize > len(self.content):
                stream = BytesIO(self.content[i:])
                self.stubber.add_response('get_object', {'Body': stream})
            else:
                stream = BytesIO(self.content[i : i + chunksize])
                self.stubber.add_response('get_object', {'Body': stream})

    def configure_for_ranged_get(self):
        self.config.multipart_threshold = 1
        self.config.multipart_chunksize = 4

    def get_download_submission_task(self):
        return self.get_task(
            DownloadSubmissionTask, main_kwargs=self.submission_main_kwargs
        )

    def wait_and_assert_completed_successfully(self, submission_task):
        submission_task()
        self.transfer_future.result()
        self.stubber.assert_no_pending_responses()

    def test_submits_no_tag_for_get_object_filename(self):
        self.wrap_executor_in_recorder()
        self.add_head_object_response()
        self.add_get_responses()

        self.submission_task = self.get_download_submission_task()
        self.wait_and_assert_completed_successfully(self.submission_task)

        # Make sure no tag to limit that task specifically was not associated
        # to that task submission.
        self.assert_tag_for_get_object(None)

    def test_submits_no_tag_for_ranged_get_filename(self):
        self.wrap_executor_in_recorder()
        self.configure_for_ranged_get()
        self.add_head_object_response()
        self.add_get_responses()

        self.submission_task = self.get_download_submission_task()
        self.wait_and_assert_completed_successfully(self.submission_task)

        # Make sure no tag to limit that task specifically was not associated
        # to that task submission.
        self.assert_tag_for_get_object(None)

    def test_submits_no_tag_for_get_object_fileobj(self):
        self.wrap_executor_in_recorder()
        self.add_head_object_response()
        self.add_get_responses()

        with open(self.filename, 'wb') as f:
            self.use_fileobj_in_call_args(f)
            self.submission_task = self.get_download_submission_task()
            self.wait_and_assert_completed_successfully(self.submission_task)

        # Make sure no tag to limit that task specifically was not associated
        # to that task submission.
        self.assert_tag_for_get_object(None)

    def test_submits_no_tag_for_ranged_get_object_fileobj(self):
        self.wrap_executor_in_recorder()
        self.configure_for_ranged_get()
        self.add_head_object_response()
        self.add_get_responses()

        with open(self.filename, 'wb') as f:
            self.use_fileobj_in_call_args(f)
            self.submission_task = self.get_download_submission_task()
            self.wait_and_assert_completed_successfully(self.submission_task)

        # Make sure no tag to limit that task specifically was not associated
        # to that task submission.
        self.assert_tag_for_get_object(None)

    def tests_submits_tag_for_get_object_nonseekable_fileobj(self):
        self.wrap_executor_in_recorder()
        self.add_head_object_response()
        self.add_get_responses()

        with open(self.filename, 'wb') as f:
            self.use_fileobj_in_call_args(NonSeekableWriter(f))
            self.submission_task = self.get_download_submission_task()
            self.wait_and_assert_completed_successfully(self.submission_task)

        # Make sure no tag to limit that task specifically was not associated
        # to that task submission.
        self.assert_tag_for_get_object(IN_MEMORY_DOWNLOAD_TAG)

    def tests_submits_tag_for_ranged_get_object_nonseekable_fileobj(self):
        self.wrap_executor_in_recorder()
        self.configure_for_ranged_get()
        self.add_head_object_response()
        self.add_get_responses()

        with open(self.filename, 'wb') as f:
            self.use_fileobj_in_call_args(NonSeekableWriter(f))
            self.submission_task = self.get_download_submission_task()
            self.wait_and_assert_completed_successfully(self.submission_task)

        # Make sure no tag to limit that task specifically was not associated
        # to that task submission.
        self.assert_tag_for_get_object(IN_MEMORY_DOWNLOAD_TAG)


class TestGetObjectTask(BaseTaskTest):
    def setUp(self):
        super().setUp()
        self.bucket = 'mybucket'
        self.key = 'mykey'
        self.extra_args = {}
        self.callbacks = []
        self.max_attempts = 5
        self.io_executor = BoundedExecutor(1000, 1)
        self.content = b'my content'
        self.stream = BytesIO(self.content)
        self.fileobj = WriteCollector()
        self.osutil = OSUtils()
        self.io_chunksize = 64 * (1024**2)
        self.task_cls = GetObjectTask
        self.download_output_manager = DownloadSeekableOutputManager(
            self.osutil, self.transfer_coordinator, self.io_executor
        )

    def get_download_task(self, **kwargs):
        default_kwargs = {
            'client': self.client,
            'bucket': self.bucket,
            'key': self.key,
            'fileobj': self.fileobj,
            'extra_args': self.extra_args,
            'callbacks': self.callbacks,
            'max_attempts': self.max_attempts,
            'download_output_manager': self.download_output_manager,
            'io_chunksize': self.io_chunksize,
        }
        default_kwargs.update(kwargs)
        self.transfer_coordinator.set_status_to_queued()
        return self.get_task(self.task_cls, main_kwargs=default_kwargs)

    def assert_io_writes(self, expected_writes):
        # Let the io executor process all of the writes before checking
        # what writes were sent to it.
        self.io_executor.shutdown()
        self.assertEqual(self.fileobj.writes, expected_writes)

    def test_main(self):
        self.stubber.add_response(
            'get_object',
            service_response={'Body': self.stream},
            expected_params={'Bucket': self.bucket, 'Key': self.key},
        )
        task = self.get_download_task()
        task()

        self.stubber.assert_no_pending_responses()
        self.assert_io_writes([(0, self.content)])

    def test_extra_args(self):
        self.stubber.add_response(
            'get_object',
            service_response={'Body': self.stream},
            expected_params={
                'Bucket': self.bucket,
                'Key': self.key,
                'Range': 'bytes=0-',
            },
        )
        self.extra_args['Range'] = 'bytes=0-'
        task = self.get_download_task()
        task()

        self.stubber.assert_no_pending_responses()
        self.assert_io_writes([(0, self.content)])

    def test_control_chunk_size(self):
        self.stubber.add_response(
            'get_object',
            service_response={'Body': self.stream},
            expected_params={'Bucket': self.bucket, 'Key': self.key},
        )
        task = self.get_download_task(io_chunksize=1)
        task()

        self.stubber.assert_no_pending_responses()
        expected_contents = []
        for i in range(len(self.content)):
            expected_contents.append((i, bytes(self.content[i : i + 1])))

        self.assert_io_writes(expected_contents)

    def test_start_index(self):
        self.stubber.add_response(
            'get_object',
            service_response={'Body': self.stream},
            expected_params={'Bucket': self.bucket, 'Key': self.key},
        )
        task = self.get_download_task(start_index=5)
        task()

        self.stubber.assert_no_pending_responses()
        self.assert_io_writes([(5, self.content)])

    def test_uses_bandwidth_limiter(self):
        bandwidth_limiter = mock.Mock(BandwidthLimiter)

        self.stubber.add_response(
            'get_object',
            service_response={'Body': self.stream},
            expected_params={'Bucket': self.bucket, 'Key': self.key},
        )
        task = self.get_download_task(bandwidth_limiter=bandwidth_limiter)
        task()

        self.stubber.assert_no_pending_responses()
        self.assertEqual(
            bandwidth_limiter.get_bandwith_limited_stream.call_args_list,
            [mock.call(mock.ANY, self.transfer_coordinator)],
        )

    def test_retries_succeeds(self):
        self.stubber.add_response(
            'get_object',
            service_response={
                'Body': StreamWithError(self.stream, SOCKET_ERROR)
            },
            expected_params={'Bucket': self.bucket, 'Key': self.key},
        )
        self.stubber.add_response(
            'get_object',
            service_response={'Body': self.stream},
            expected_params={'Bucket': self.bucket, 'Key': self.key},
        )
        task = self.get_download_task()
        task()

        # Retryable error should have not affected the bytes placed into
        # the io queue.
        self.stubber.assert_no_pending_responses()
        self.assert_io_writes([(0, self.content)])

    def test_retries_failure(self):
        for _ in range(self.max_attempts):
            self.stubber.add_response(
                'get_object',
                service_response={
                    'Body': StreamWithError(self.stream, SOCKET_ERROR)
                },
                expected_params={'Bucket': self.bucket, 'Key': self.key},
            )

        task = self.get_download_task()
        task()
        self.transfer_coordinator.announce_done()

        # Should have failed out on a RetriesExceededError
        with self.assertRaises(RetriesExceededError):
            self.transfer_coordinator.result()
        self.stubber.assert_no_pending_responses()

    def test_retries_in_middle_of_streaming(self):
        # After the first read a retryable error will be thrown
        self.stubber.add_response(
            'get_object',
            service_response={
                'Body': StreamWithError(
                    copy.deepcopy(self.stream), SOCKET_ERROR, 1
                )
            },
            expected_params={'Bucket': self.bucket, 'Key': self.key},
        )
        self.stubber.add_response(
            'get_object',
            service_response={'Body': self.stream},
            expected_params={'Bucket': self.bucket, 'Key': self.key},
        )
        task = self.get_download_task(io_chunksize=1)
        task()

        self.stubber.assert_no_pending_responses()
        expected_contents = []
        # This is the content initially read in before the retry hit on the
        # second read()
        expected_contents.append((0, bytes(self.content[0:1])))

        # The rest of the content should be the entire set of data partitioned
        # out based on the one byte stream chunk size. Note the second
        # element in the list should be a copy of the first element since
        # a retryable exception happened in between.
        for i in range(len(self.content)):
            expected_contents.append((i, bytes(self.content[i : i + 1])))
        self.assert_io_writes(expected_contents)

    def test_cancels_out_of_queueing(self):
        self.stubber.add_response(
            'get_object',
            service_response={
                'Body': CancelledStreamWrapper(
                    self.stream, self.transfer_coordinator
                )
            },
            expected_params={'Bucket': self.bucket, 'Key': self.key},
        )
        task = self.get_download_task()
        task()

        self.stubber.assert_no_pending_responses()
        # Make sure that no contents were added to the queue because the task
        # should have been canceled before trying to add the contents to the
        # io queue.
        self.assert_io_writes([])

    def test_handles_callback_on_initial_error(self):
        # We can't use the stubber for this because we need to raise
        # a S3_RETRYABLE_DOWNLOAD_ERRORS, and the stubber only allows
        # you to raise a ClientError.
        self.client.get_object = mock.Mock(side_effect=SOCKET_ERROR())
        task = self.get_download_task()
        task()
        self.transfer_coordinator.announce_done()
        # Should have failed out on a RetriesExceededError because
        # get_object keeps raising a socket error.
        with self.assertRaises(RetriesExceededError):
            self.transfer_coordinator.result()


class TestImmediatelyWriteIOGetObjectTask(TestGetObjectTask):
    def setUp(self):
        super().setUp()
        self.task_cls = ImmediatelyWriteIOGetObjectTask
        # When data is written out, it should not use the io executor at all
        # if it does use the io executor that is a deviation from expected
        # behavior as the data should be written immediately to the file
        # object once downloaded.
        self.io_executor = None
        self.download_output_manager = DownloadSeekableOutputManager(
            self.osutil, self.transfer_coordinator, self.io_executor
        )

    def assert_io_writes(self, expected_writes):
        self.assertEqual(self.fileobj.writes, expected_writes)


class BaseIOTaskTest(BaseTaskTest):
    def setUp(self):
        super().setUp()
        self.files = FileCreator()
        self.osutil = OSUtils()
        self.temp_filename = os.path.join(self.files.rootdir, 'mytempfile')
        self.final_filename = os.path.join(self.files.rootdir, 'myfile')

    def tearDown(self):
        super().tearDown()
        self.files.remove_all()


class TestIOStreamingWriteTask(BaseIOTaskTest):
    def test_main(self):
        with open(self.temp_filename, 'wb') as f:
            task = self.get_task(
                IOStreamingWriteTask,
                main_kwargs={'fileobj': f, 'data': b'foobar'},
            )
            task()
            task2 = self.get_task(
                IOStreamingWriteTask,
                main_kwargs={'fileobj': f, 'data': b'baz'},
            )
            task2()
        with open(self.temp_filename, 'rb') as f:
            # We should just have written to the file in the order
            # the tasks were executed.
            self.assertEqual(f.read(), b'foobarbaz')


class TestIOWriteTask(BaseIOTaskTest):
    def test_main(self):
        with open(self.temp_filename, 'wb') as f:
            # Write once to the file
            task = self.get_task(
                IOWriteTask,
                main_kwargs={'fileobj': f, 'data': b'foo', 'offset': 0},
            )
            task()

            # Write again to the file
            task = self.get_task(
                IOWriteTask,
                main_kwargs={'fileobj': f, 'data': b'bar', 'offset': 3},
            )
            task()

        with open(self.temp_filename, 'rb') as f:
            self.assertEqual(f.read(), b'foobar')


class TestIORenameFileTask(BaseIOTaskTest):
    def test_main(self):
        with open(self.temp_filename, 'wb') as f:
            task = self.get_task(
                IORenameFileTask,
                main_kwargs={
                    'fileobj': f,
                    'final_filename': self.final_filename,
                    'osutil': self.osutil,
                },
            )
            task()
        self.assertTrue(os.path.exists(self.final_filename))
        self.assertFalse(os.path.exists(self.temp_filename))


class TestIOCloseTask(BaseIOTaskTest):
    def test_main(self):
        with open(self.temp_filename, 'w') as f:
            task = self.get_task(IOCloseTask, main_kwargs={'fileobj': f})
            task()
            self.assertTrue(f.closed)


class TestDownloadChunkIterator(unittest.TestCase):
    def test_iter(self):
        content = b'my content'
        body = BytesIO(content)
        ref_chunks = []
        for chunk in DownloadChunkIterator(body, len(content)):
            ref_chunks.append(chunk)
        self.assertEqual(ref_chunks, [b'my content'])

    def test_iter_chunksize(self):
        content = b'1234'
        body = BytesIO(content)
        ref_chunks = []
        for chunk in DownloadChunkIterator(body, 3):
            ref_chunks.append(chunk)
        self.assertEqual(ref_chunks, [b'123', b'4'])

    def test_empty_content(self):
        body = BytesIO(b'')
        ref_chunks = []
        for chunk in DownloadChunkIterator(body, 3):
            ref_chunks.append(chunk)
        self.assertEqual(ref_chunks, [b''])


class TestDeferQueue(unittest.TestCase):
    def setUp(self):
        self.q = DeferQueue()

    def test_no_writes_when_not_lowest_block(self):
        writes = self.q.request_writes(offset=1, data='bar')
        self.assertEqual(writes, [])

    def test_writes_returned_in_order(self):
        self.assertEqual(self.q.request_writes(offset=3, data='d'), [])
        self.assertEqual(self.q.request_writes(offset=2, data='c'), [])
        self.assertEqual(self.q.request_writes(offset=1, data='b'), [])

        # Everything at this point has been deferred, but as soon as we
        # send offset=0, that will unlock offsets 0-3.
        writes = self.q.request_writes(offset=0, data='a')
        self.assertEqual(
            writes,
            [
                {'offset': 0, 'data': 'a'},
                {'offset': 1, 'data': 'b'},
                {'offset': 2, 'data': 'c'},
                {'offset': 3, 'data': 'd'},
            ],
        )

    def test_unlocks_partial_range(self):
        self.assertEqual(self.q.request_writes(offset=5, data='f'), [])
        self.assertEqual(self.q.request_writes(offset=1, data='b'), [])

        # offset=0 unlocks 0-1, but offset=5 still needs to see 2-4 first.
        writes = self.q.request_writes(offset=0, data='a')
        self.assertEqual(
            writes,
            [
                {'offset': 0, 'data': 'a'},
                {'offset': 1, 'data': 'b'},
            ],
        )

    def test_data_can_be_any_size(self):
        self.q.request_writes(offset=5, data='hello world')
        writes = self.q.request_writes(offset=0, data='abcde')
        self.assertEqual(
            writes,
            [
                {'offset': 0, 'data': 'abcde'},
                {'offset': 5, 'data': 'hello world'},
            ],
        )

    def test_data_queued_in_order(self):
        # This immediately gets returned because offset=0 is the
        # next range we're waiting on.
        writes = self.q.request_writes(offset=0, data='hello world')
        self.assertEqual(writes, [{'offset': 0, 'data': 'hello world'}])
        # Same thing here but with offset
        writes = self.q.request_writes(offset=11, data='hello again')
        self.assertEqual(writes, [{'offset': 11, 'data': 'hello again'}])

    def test_writes_below_min_offset_are_ignored(self):
        self.q.request_writes(offset=0, data='a')
        self.q.request_writes(offset=1, data='b')
        self.q.request_writes(offset=2, data='c')

        # At this point we're expecting offset=3, so if a write
        # comes in below 3, we ignore it.
        self.assertEqual(self.q.request_writes(offset=0, data='a'), [])
        self.assertEqual(self.q.request_writes(offset=1, data='b'), [])

        self.assertEqual(
            self.q.request_writes(offset=3, data='d'),
            [{'offset': 3, 'data': 'd'}],
        )

    def test_duplicate_writes_are_ignored(self):
        self.q.request_writes(offset=2, data='c')
        self.q.request_writes(offset=1, data='b')

        # We're still waiting for offset=0, but if
        # a duplicate write comes in for offset=2/offset=1
        # it's ignored.  This gives "first one wins" behavior.
        self.assertEqual(self.q.request_writes(offset=2, data='X'), [])
        self.assertEqual(self.q.request_writes(offset=1, data='Y'), [])

        self.assertEqual(
            self.q.request_writes(offset=0, data='a'),
            [
                {'offset': 0, 'data': 'a'},
                # Note we're seeing 'b' 'c', and not 'X', 'Y'.
                {'offset': 1, 'data': 'b'},
                {'offset': 2, 'data': 'c'},
            ],
        )
