# Copyright (C) 2003-2022, Stefan Schwarzer <sschwarzer@sschwarzer.net>
# and ftputil contributors (see `doc/contributors.txt`)
# See the file LICENSE for licensing terms.

# Execute tests on a real FTP server (other tests use mock code).
#
# These tests write some files and directories on the local client and the
# remote server. You'll need write access in the login directory. These tests
# can take a few minutes because they have to wait to test the timezone
# calculation.

import datetime
import ftplib
import functools
import gc
import operator
import os
import pathlib
import time
import stat

import pytest

import ftputil.error
import ftputil.file_transfer
import ftputil.path_encoding
import ftputil.session
import ftputil.stat_cache

import test


def expected_time_shift():
    """
    Return the expected time shift in seconds.

    Unfortunately, the calculation may depend on the timezone of the server,
    i. e. the timezone used in directory listings coming from the server.

    So, depending on your test environment, you may need to change this
    function for your environment. _If_ you need an adapted
    `expected_time_shift`, please contact me (my e-mail address is in the
    ftputil documentation).

    In my particular case, I use Pure-FTPd as FTP server for the integration
    tests. At some point, it returned listings in the local timezone of the
    server, later it used UTC time, and now it uses the local timezone again.
    I wasn't able to find out why or how I can control this.
    """
    raw_time_shift = (
        datetime.datetime.now() - datetime.datetime.now(datetime.timezone.utc)
    ).seconds
    # To be safe, round the above value to units of 900 s (1/4 hours).
    return round(raw_time_shift / 900.0) * 900


# The containerized PureFTPd seems to use UTC.
EXPECTED_TIME_SHIFT = 0.0


# Set when starting container
PORT = 2121

DEFAULT_SESSION_FACTORY = ftputil.session.session_factory(
    port=PORT, encrypt_data_channel=False
)


class Cleaner:
    """
    This class helps remove directories and files which might otherwise be left
    behind if a test fails in unexpected ways.
    """

    def __init__(self, host):
        # The test class (probably `RealFTPTest`) and the helper
        # class share the same `FTPHost` object.
        self._host = host
        self._ftp_items = []

    def add_dir(self, path):
        """
        Schedule a directory with path `path` for removal.
        """
        self._ftp_items.append(("d", self._host.path.abspath(path)))

    def add_file(self, path):
        """
        Schedule a file with path `path` for removal.
        """
        self._ftp_items.append(("f", self._host.path.abspath(path)))

    def clean(self):
        """
        Remove the directories and files previously remembered. The removal
        works in reverse order of the scheduling with `add_dir` and `add_file`.

        Errors due to a removal are ignored.
        """
        self._host.chdir("/")
        for type_, path in reversed(self._ftp_items):
            try:
                if type_ == "d":
                    # If something goes wrong in `rmtree` we might leave a mess
                    # behind.
                    self._host.rmtree(path)
                elif type_ == "f":
                    # Minor mess if `remove` fails
                    self._host.remove(path)
            except ftputil.error.FTPError:
                pass


class RealFTPTest:
    def setup_method(self, method):
        # Server, username, password.
        self.login_data = ("localhost", "ftptest", "dummy")
        self.host = ftputil.FTPHost(
            *self.login_data, session_factory=DEFAULT_SESSION_FACTORY
        )
        self.cleaner = Cleaner(self.host)

    def teardown_method(self, method):
        self.cleaner.clean()
        self.host.close()

    #
    # Helper methods
    #
    def make_remote_file(self, path):
        """Create a file on the FTP host."""
        self.cleaner.add_file(path)
        with self.host.open(path, "wb") as file_:
            # Write something. Otherwise the FTP server might not update the
            # time of last modification if the file existed before.
            file_.write(b"\n")

    def make_local_file(self):
        """
        Create a file on the local host (= on the client side).
        """
        with open("_local_file_", "wb") as fobj:
            fobj.write(b"abc\x12\x34def\t")


class TestMkdir(RealFTPTest):
    def test_directory_exists_after_mkdir(self):
        """
        After a `mkdir` call, the directory should exist.
        """
        host = self.host
        dir_name = "_testdir_"
        file_name = host.path.join(dir_name, "_nonempty_")
        self.cleaner.add_dir(dir_name)
        # Make dir and check if the directory is there.
        host.mkdir(dir_name)
        files = host.listdir(host.curdir)
        assert dir_name in files

    def test_makedirs_without_existing_dirs(self):
        """
        If some directories in a `makedirs` call don't exist yet, they should
        be implcitly created.
        """
        host = self.host
        # No `_dir1_` yet
        assert "_dir1_" not in host.listdir(host.curdir)
        # Vanilla case, all should go well.
        host.makedirs("_dir1_/dir2/dir3/dir4")
        self.cleaner.add_dir("_dir1_")
        # Check host.
        assert host.path.isdir("_dir1_")
        assert host.path.isdir("_dir1_/dir2")
        assert host.path.isdir("_dir1_/dir2/dir3")
        assert host.path.isdir("_dir1_/dir2/dir3/dir4")

    def test_makedirs_from_non_root_directory(self):
        # This is a testcase for issue #22, see
        # http://ftputil.sschwarzer.net/trac/ticket/22 .
        host = self.host
        # No `_dir1_` and `_dir2_` yet
        assert "_dir1_" not in host.listdir(host.curdir)
        assert "_dir2_" not in host.listdir(host.curdir)
        # Part 1: Try to make directories starting from `_dir1_` and
        # change to non-root directory.
        self.cleaner.add_dir("_dir1_")
        host.mkdir("_dir1_")
        host.chdir("_dir1_")
        host.makedirs("_dir2_/_dir3_")
        # Test for expected directory hierarchy.
        assert host.path.isdir("/_dir1_")
        assert host.path.isdir("/_dir1_/_dir2_")
        assert host.path.isdir("/_dir1_/_dir2_/_dir3_")
        assert not host.path.isdir("/_dir1_/_dir1_")
        # Remove all but the directory we're in.
        host.rmdir("/_dir1_/_dir2_/_dir3_")
        host.rmdir("/_dir1_/_dir2_")
        # Part 2: Try to make directories starting from root.
        self.cleaner.add_dir("/_dir2_")
        host.makedirs("/_dir2_/_dir3_")
        # Test for expected directory hierarchy
        assert host.path.isdir("/_dir2_")
        assert host.path.isdir("/_dir2_/_dir3_")
        assert not host.path.isdir("/_dir1_/_dir2_")

    def test_makedirs_of_existing_directory(self):
        """
        Calling `makedirs` on an existing directory with `exist_ok` should do
        nothing.
        """
        host = self.host
        # The (chrooted) login directory
        host.makedirs("/", exist_ok=True)

    def test_makedirs_with_file_in_the_way(self):
        """
        If a part of `makedirs`'s path is a file, a `PermanentError` should be
        raised.
        """
        host = self.host
        self.cleaner.add_dir("_dir1_")
        host.mkdir("_dir1_")
        self.make_remote_file("_dir1_/file1")
        # Try it.
        with pytest.raises(ftputil.error.PermanentError):
            host.makedirs("_dir1_/file1")
        with pytest.raises(ftputil.error.PermanentError):
            host.makedirs("_dir1_/file1/dir2")

    def test_makedirs_with_existing_directory(self):
        """
        An already-existent subdirectory in the path of `makedirs` should be
        ignored.
        """
        host = self.host
        self.cleaner.add_dir("_dir1_")
        host.mkdir("_dir1_")
        host.makedirs("_dir1_/dir2")
        # Check
        assert host.path.isdir("_dir1_")
        assert host.path.isdir("_dir1_/dir2")

    def test_makedirs_in_non_writable_directory(self):
        """
        If `makedirs` is asked to create a directory in a non-writable
        directory, a `PermanentError` should be raised.
        """
        host = self.host
        # Preparation: `rootdir1` exists but is only writable by root.
        with pytest.raises(ftputil.error.PermanentError):
            host.makedirs("rootdir1/dir2")

    def test_makedirs_with_writable_directory_at_end(self):
        """
        If `makedirs` is asked to create a directory in a writable directory
        under a non-writable directory, the `makedirs` call should succeed.
        """
        host = self.host
        self.cleaner.add_dir("rootdir2/dir2")
        # Preparation: `rootdir2` exists but is only writable by root. `dir2`
        # is writable by regular ftp users. Both directories below should work.
        host.makedirs("rootdir2/dir2", exist_ok=True)
        host.makedirs("rootdir2/dir2/dir3")
        assert host.path.isdir("rootdir2/dir2")
        assert host.path.isdir("rootdir2/dir2/dir3")


class TestRemoval(RealFTPTest):

    # Tests for `remove`

    def test_remove_existing_file(self):
        """
        Removal of an existing file should succeed.
        """
        self.cleaner.add_file("_testfile_")
        self.make_remote_file("_testfile_")
        host = self.host
        assert host.path.isfile("_testfile_")
        host.remove("_testfile_")
        assert not host.path.exists("_testfile_")

    def test_cache_invalidation_for_remove_exception(self):
        """
        If a file is removed, its stats information should be removed from the
        cache. This should also work if the removal raises an exception.
        """
        # Test for ticket #150
        self.cleaner.add_file("_testfile_")
        self.make_remote_file("_testfile_")
        host = self.host
        assert host.path.isfile("_testfile_")
        # Monkey-patch session `delete` call.
        old_delete = host._session.delete

        def failing_delete(path):
            # Simulate the case where the file is removed on the server, but a
            # proper reply doesn't get through to the client. It doesn't matter
            # whether the exception is `error_temp` or `error_perm`.
            old_delete(path)
            raise ftplib.error_perm("simulated error")

        host._session.delete = failing_delete
        with pytest.raises(ftputil.error.PermanentError):
            host.remove("_testfile_")
        assert not host.path.exists("_testfile_")

    def test_remove_non_existent_item(self):
        """
        If trying to remove a non-existent file system item, a `PermanentError`
        should be raised.
        """
        host = self.host
        with pytest.raises(ftputil.error.PermanentError):
            host.remove("nonexistent")

    def test_remove_on_directory(self):
        """
        Calling `remove` on a directory should raise a `PermanentError`.

        (Directories must be removed with `rmdir`.)
        """
        host = self.host
        dir_name = "_testdir_"
        self.cleaner.add_dir(dir_name)
        host.mkdir(dir_name)
        try:
            try:
                host.remove(dir_name)
            except ftputil.error.PermanentError as exc:
                assert str(exc).startswith("remove/unlink can only delete files")
            else:
                pytest.fail("we shouldn't have come here")
        finally:
            # Delete empty directory.
            host.rmdir(dir_name)
        files = host.listdir(host.curdir)
        assert dir_name not in files

    # Test for `rmdir`

    def test_remove_existing_directory(self):
        """
        If `rmdir` is called on an empty directory, the call should succeed.
        """
        self.cleaner.add_dir("_testdir_")
        host = self.host
        host.mkdir("_testdir_")
        assert host.path.isdir("_testdir_")
        host.rmdir("_testdir_")
        assert not host.path.exists("_testdir_")

    def test_rmdir_on_nonempty_directory(self):
        """
        If a directory exists, but isn't empty, `rmdir` should raise a
        `PermanentError`.
        """
        host = self.host
        dir_name = "_testdir_"
        self.cleaner.add_dir(dir_name)
        host.mkdir(dir_name)
        # Try to remove a non-empty directory.
        file_name = host.path.join(dir_name, "_nonempty_")
        self.cleaner.add_file(file_name)
        non_empty = host.open(file_name, "w")
        non_empty.close()
        with pytest.raises(ftputil.error.PermanentError):
            host.rmdir(dir_name)

    def test_cache_invalidation_for_rmdir_exception(self):
        """
        If a directory is removed, its stats information should be removed from
        the cache. This should also work if the removal raises an exception.
        """
        # Test for ticket #150
        self.cleaner.add_dir("_testdir_")
        host = self.host
        host.mkdir("_testdir_")
        assert host.path.isdir("_testdir_")
        # Monkey-patch session `rmd` call.
        old_rmd = host._session.rmd

        def failing_rmd(path):
            # Simulate the case where the directory is removed on the server,
            # but a proper reply doesn't get through to the client. It doesn't
            # matter whether the exception is `error_temp` or `error_perm`.
            old_rmd(path)
            raise ftplib.error_perm("simulated error")

        host._session.rmd = failing_rmd
        with pytest.raises(ftputil.error.PermanentError):
            host.rmdir("_testdir_")
        assert not host.path.exists("_testdir_")

    # Tests for `rmtree`

    def build_tree(self, host):
        """
        Build a directory tree for tests.
        """
        self.cleaner.add_dir("_dir1_")
        host.makedirs("_dir1_/dir2")
        self.make_remote_file("_dir1_/file1")
        self.make_remote_file("_dir1_/file2")
        self.make_remote_file("_dir1_/dir2/file3")
        self.make_remote_file("_dir1_/dir2/file4")

    def test_rmtree_without_error_handler(self):
        """
        Calling `rmtree` on a directory tree should remove the directory and
        everything under it.
        """
        host = self.host
        self.build_tree(host)
        # Remove `dir2`.
        host.rmtree("_dir1_/dir2")
        assert not host.path.exists("_dir1_/dir2")
        assert host.path.exists("_dir1_/file2")
        # Re-create `dir2` and remove `_dir1_`.
        host.mkdir("_dir1_/dir2")
        self.make_remote_file("_dir1_/dir2/file3")
        self.make_remote_file("_dir1_/dir2/file4")
        host.rmtree("_dir1_")
        assert not host.path.exists("_dir1_")

    def test_rmtree_with_error_handler(self):
        """
        If an `rmtree` call specifies an error handler, it should be used.
        """
        host = self.host
        self.cleaner.add_dir("_dir1_")
        host.mkdir("_dir1_")
        self.make_remote_file("_dir1_/file1")
        # Prepare error "handler"
        log = []

        def error_handler(*args):
            log.append(args)

        # Try to remove a file as root "directory".
        host.rmtree("_dir1_/file1", ignore_errors=True, onerror=error_handler)
        assert log == []
        host.rmtree("_dir1_/file1", ignore_errors=False, onerror=error_handler)
        assert log[0][0] == host.listdir
        assert log[0][1] == "_dir1_/file1"
        assert log[1][0] == host.rmdir
        assert log[1][1] == "_dir1_/file1"
        host.rmtree("_dir1_")
        # Try to remove a non-existent directory.
        del log[:]
        host.rmtree("_dir1_", ignore_errors=False, onerror=error_handler)
        assert log[0][0] == host.listdir
        assert log[0][1] == "_dir1_"
        assert log[1][0] == host.rmdir
        assert log[1][1] == "_dir1_"

    def test_remove_file_with_rmtree(self):
        """
        Calling `rmtree` on a file should raise a `PermanentError`.
        """
        host = self.host
        self.build_tree(host)
        with pytest.raises(ftputil.error.PermanentError):
            host.rmtree("_dir1_/file2")


class TestWalk(RealFTPTest):
    """
    Walk the directory tree

      walk_test
      ├── dir1
      │   ├── dir11
      │   └── dir12
      │       ├── dir123
      │       │   └── file1234
      │       ├── file121
      │       └── file122
      ├── dir2
      ├── dir3
      │   ├── dir31
      │   ├── dir32 -> ../dir1/dir12/dir123
      │   ├── file31
      │   └── file32
      └── file4

    and check if the results are the expected ones.
    """

    def _walk_test(self, expected_result, **walk_kwargs):
        """
        Walk the directory and test results.
        """
        # Collect data using `walk`.
        actual_result = []
        for items in self.host.walk(**walk_kwargs):
            actual_result.append(items)
        # Compare with expected results.
        assert len(actual_result) == len(expected_result)
        for index, _ in enumerate(actual_result):
            assert actual_result[index] == expected_result[index]

    def test_walk_topdown(self):
        # Preparation: build tree in directory `walk_test`.
        expected_result = [
            ("walk_test", ["dir1", "dir2", "dir3"], ["file4"]),
            #
            ("walk_test/dir1", ["dir11", "dir12"], []),
            #
            ("walk_test/dir1/dir11", [], []),
            #
            ("walk_test/dir1/dir12", ["dir123"], ["file121", "file122"]),
            #
            ("walk_test/dir1/dir12/dir123", [], ["file1234"]),
            #
            ("walk_test/dir2", [], []),
            #
            ("walk_test/dir3", ["dir31", "dir32"], ["file31", "file32"]),
            #
            ("walk_test/dir3/dir31", [], []),
        ]
        self._walk_test(expected_result, top="walk_test")

    def test_walk_depth_first(self):
        # Preparation: build tree in directory `walk_test`
        expected_result = [
            ("walk_test/dir1/dir11", [], []),
            #
            ("walk_test/dir1/dir12/dir123", [], ["file1234"]),
            #
            ("walk_test/dir1/dir12", ["dir123"], ["file121", "file122"]),
            #
            ("walk_test/dir1", ["dir11", "dir12"], []),
            #
            ("walk_test/dir2", [], []),
            #
            ("walk_test/dir3/dir31", [], []),
            #
            ("walk_test/dir3", ["dir31", "dir32"], ["file31", "file32"]),
            #
            ("walk_test", ["dir1", "dir2", "dir3"], ["file4"]),
        ]
        self._walk_test(expected_result, top="walk_test", topdown=False)

    def test_walk_following_links(self):
        # Preparation: build tree in directory `walk_test`.
        expected_result = [
            ("walk_test", ["dir1", "dir2", "dir3"], ["file4"]),
            #
            ("walk_test/dir1", ["dir11", "dir12"], []),
            #
            ("walk_test/dir1/dir11", [], []),
            #
            ("walk_test/dir1/dir12", ["dir123"], ["file121", "file122"]),
            #
            ("walk_test/dir1/dir12/dir123", [], ["file1234"]),
            #
            ("walk_test/dir2", [], []),
            #
            ("walk_test/dir3", ["dir31", "dir32"], ["file31", "file32"]),
            #
            ("walk_test/dir3/dir31", [], []),
            #
            ("walk_test/dir3/dir32", [], ["file1234"]),
        ]
        self._walk_test(expected_result, top="walk_test", followlinks=True)


class TestRename(RealFTPTest):
    def test_rename(self):
        """
        If `rename` is called on two paths, the first should disappear and the
        second should exist afterward.

        This test also tests `Path` support.
        """
        host = self.host
        # Make sure both files are gone after the test.
        self.cleaner.add_file("_testfile1_")
        self.cleaner.add_file("_testfile2_")
        self.make_remote_file("_testfile1_")
        host.rename(pathlib.Path("_testfile1_"), "_testfile2_")
        assert not host.path.exists("_testfile1_")
        assert host.path.exists(pathlib.Path("_testfile2_"))

    def test_cache_invalidation_for_rename(self):
        """
        A `rename` call should invalidate the cache entries for both path
        arguments. The purpose of the first invalidation is obvious, but the
        second invalidation is also important in case the path of the target
        existed before the rename and changes according to the new file stat
        information.

        This test also tests `Path` support.
        """
        # Test for ticket #150
        host = self.host
        # Make sure both files are gone after the test.
        self.cleaner.add_file("_testfile1_")
        self.cleaner.add_file("_testfile2_")
        # Case 1: Target file doesn't exist yet.
        self.make_remote_file("_testfile1_")
        file1_stat = host.stat("_testfile1_")
        host.rename(pathlib.Path("_testfile1_"), "_testfile2_")
        assert not host.path.exists("_testfile1_")
        assert host.path.exists(pathlib.Path("_testfile2_"))
        # Case 2: Target file already exists.
        #  Write the source file with a size different from the target file, so
        #  we can check whether we find the old or the new stat information
        #  when stat'ing the target file after the rename.
        with host.open("_testfile1_", "w") as fobj:
            fobj.write("abcdef\n")
        self.make_remote_file("_testfile2_")
        file1_stat = host.stat("_testfile1_")
        file2_stat = host.stat("_testfile2_")
        host.rename(pathlib.Path("_testfile1_"), "_testfile2_")
        assert not host.path.exists("_testfile1_")
        assert host.path.exists(pathlib.Path("_testfile2_"))
        new_file2_stat = host.stat("_testfile2_")
        assert new_file2_stat.st_size > file2_stat.st_size

    def test_cache_invalidation_for_rename_exception(self):
        """
        If a file system item is renamed/moved, its stats information should be
        removed from the cache. This should also work if the rename operation
        raises an exception.
        """
        # Test for ticket #150
        host = self.host
        # Make sure the target of the renaming operation is removed later.
        # Make sure both files are gone after the test.
        self.cleaner.add_file("_testfile1_")
        self.cleaner.add_file("_testfile2_")
        # Write the source file with a size different from the target file, so
        # we can check whether we find the old or the new stat information
        # when stat'ing the target file after the rename.
        with host.open("_testfile1_", "w") as fobj:
            fobj.write("abcdef\n")
        self.make_remote_file("_testfile2_")
        file1_stat = host.stat("_testfile1_")
        file2_stat = host.stat("_testfile2_")
        # Monkey-patch session `rename` call.
        old_rename = host._session.rename

        def failing_rename(source, target):
            # Simulate the case where the rename completely or partially
            # succeeds on the server, but a proper reply doesn't get through to
            # the client. It doesn't matter whether the exception is
            # `error_temp` or `error_perm`.
            old_rename(source, target)
            raise ftplib.error_perm("simulated error")

        host._session.rename = failing_rename
        #
        with pytest.raises(ftputil.error.PermanentError):
            host.rename(pathlib.Path("_testfile1_"), "_testfile2_")
        assert not host.path.exists("_testfile1_")
        assert host.path.exists(pathlib.Path("_testfile2_"))
        new_file2_stat = host.stat("_testfile2_")
        assert new_file2_stat.st_size > file2_stat.st_size

    def test_rename_with_spaces_in_directory(self):
        """
        `rename` should work if source and target contain a directory with
        spaces in its name.

        This test also tests `Path` support.
        """
        host = self.host
        dir_name = "_dir with spaces_"
        self.cleaner.add_dir(dir_name)
        host.mkdir(pathlib.Path(dir_name))
        self.make_remote_file(dir_name + "/testfile1")
        host.rename(dir_name + "/testfile1", pathlib.Path(dir_name + "/testfile2"))
        assert not host.path.exists(dir_name + "/testfile1")
        assert host.path.exists(dir_name + "/testfile2")


class TestStat(RealFTPTest):
    def test_stat(self):
        """
        Test some stat-related calls.
        """
        host = self.host
        dir_name = "_testdir_"
        file_name = host.path.join(dir_name, "_nonempty_")
        # Make a directory and a file in it.
        self.cleaner.add_dir(dir_name)
        host.mkdir(dir_name)
        with host.open(file_name, "wb") as fobj:
            fobj.write(b"abc\x12\x34def\t")
        # Do some stats
        # - dir
        dir_stat = host.stat(dir_name)
        assert isinstance(dir_stat._st_name, str)
        assert host.listdir(dir_name) == ["_nonempty_"]
        assert host.path.isdir(dir_name)
        assert not host.path.isfile(dir_name)
        assert not host.path.islink(dir_name)
        # - file
        file_stat = host.stat(file_name)
        assert isinstance(file_stat._st_name, str)
        assert not host.path.isdir(file_name)
        assert host.path.isfile(file_name)
        assert not host.path.islink(file_name)
        assert host.path.getsize(file_name) == 9
        # - file's modification time
        host.synchronize_times()
        #  The returned server mtime is supposed to be converted to UTC, so
        #  there should be only a small difference between server and client
        #  time. Arbitrarily allow two minutes here to account for limited time
        #  precision from parsing the directory.
        server_mtime = host.path.getmtime(file_name)
        client_mtime = datetime.datetime.now(datetime.timezone.utc).timestamp()
        assert not (client_mtime - server_mtime > 120)

    def test_issomething_for_nonexistent_directory(self):
        """
        If the `is*` methods are called on a path where the base directory
        doesn't exist, all of the methods should return `False`.
        """
        host = self.host
        # Check if we get the right results if even the containing directory
        # doesn't exist (see ticket #66).
        nonexistent_path = "/nonexistent/nonexistent"
        assert not host.path.isdir(nonexistent_path)
        assert not host.path.isfile(nonexistent_path)
        assert not host.path.islink(nonexistent_path)

    def test_special_broken_link(self):
        """
        If `is*` methods are called on a broken link (i.e. the link target
        doesn't exist), `islink` should return `True` and `isdir` and `isfile`
        should return `False`.
        """
        # Test for ticket #39.
        host = self.host
        broken_link_name = os.path.join("dir_with_broken_link", "nonexistent")
        assert host.lstat(broken_link_name)._st_target == "../nonexistent/nonexistent"
        assert not host.path.isdir(broken_link_name)
        assert not host.path.isfile(broken_link_name)
        assert host.path.islink(broken_link_name)

    def test_concurrent_access(self):
        """
        If we have two `FTPHost` instances for the same server directory,
        operations on one `FTPHost` instance shouldn't influence the cache
        entries of the other `FTPHost` instance.
        """
        self.make_remote_file("_testfile_")
        with ftputil.FTPHost(
            *self.login_data, session_factory=DEFAULT_SESSION_FACTORY
        ) as host1:
            with ftputil.FTPHost(
                *self.login_data, session_factory=DEFAULT_SESSION_FACTORY
            ) as host2:
                stat_result1 = host1.stat("_testfile_")
                stat_result2 = host2.stat("_testfile_")
                assert stat_result1 == stat_result2
                host2.remove("_testfile_")
                # Can still get the result via `host1`
                stat_result1 = host1.stat("_testfile_")
                assert stat_result1 == stat_result2
                # Stat'ing on `host2` gives an exception.
                with pytest.raises(ftputil.error.PermanentError):
                    host2.stat("_testfile_")
                # Stat'ing on `host1` after invalidation
                absolute_path = host1.path.join(host1.getcwd(), "_testfile_")
                host1.stat_cache.invalidate(absolute_path)
                with pytest.raises(ftputil.error.PermanentError):
                    host1.stat("_testfile_")

    def test_cache_auto_resizing(self):
        """
        Test if the cache is resized appropriately.
        """
        host = self.host
        cache = host.stat_cache._cache
        # Make sure the cache size isn't adjusted towards smaller values.
        unused_entries = host.listdir("walk_test")
        assert cache.size == ftputil.stat_cache.StatCache._DEFAULT_CACHE_SIZE
        # Make the cache very small initially and see if it gets resized.
        cache.size = 2
        entries = host.listdir("walk_test")
        # The adjusted cache size should be larger or equal to the number of
        # items in `walk_test` and its parent directory. The latter is read
        # implicitly upon `listdir`'s `isdir` call.
        expected_min_cache_size = max(len(host.listdir(host.curdir)), len(entries))
        assert cache.size >= expected_min_cache_size


class TestUploadAndDownload(RealFTPTest):
    """
    Test upload and download (including time shift test).
    """

    def test_time_shift(self):
        self.host.synchronize_times()
        assert self.host.time_shift() == EXPECTED_TIME_SHIFT

    @pytest.mark.slow_test
    def test_upload(self):
        """
        `upload_if_newer` should respect the time difference between client and
        server, including consideration of the time shift.
        """
        host = self.host
        host.synchronize_times()
        local_file = "_local_file_"
        remote_file = "_remote_file_"
        # Make local file to upload.
        self.make_local_file()
        # Wait, else small time differences between client and server actually
        # could trigger the update.
        time.sleep(65)
        try:
            self.cleaner.add_file(remote_file)
            host.upload(local_file, remote_file)
            # Retry; shouldn't be uploaded
            uploaded = host.upload_if_newer(local_file, remote_file)
            assert uploaded is False
            # Rewrite the local file.
            self.make_local_file()
            # Retry; should be uploaded now
            uploaded = host.upload_if_newer(local_file, remote_file)
            assert uploaded is True
        finally:
            # Clean up
            os.unlink(local_file)

    @pytest.mark.slow_test
    def test_download(self):
        """
        `download_if_newer` should respect the time difference between client
        and server, including consideration of the time shift.
        """
        host = self.host
        host.synchronize_times()
        local_file = "_local_file_"
        remote_file = "_remote_file_"
        # Make a remote file.
        self.make_remote_file(remote_file)
        # File should be downloaded as it's not present yet.
        downloaded = host.download_if_newer(remote_file, local_file)
        assert downloaded is True
        try:
            # If the remote file, taking the datetime precision into account,
            # _might_ be newer, the file will be downloaded again. To prevent
            # this, wait a bit over a minute (the remote precision), then
            # "touch" the local file.
            time.sleep(65)
            # Create empty file.
            with open(local_file, "w") as fobj:
                pass
            # Local file is present and newer, so shouldn't download.
            downloaded = host.download_if_newer(remote_file, local_file)
            assert downloaded is False
            # Re-make the remote file.
            self.make_remote_file(remote_file)
            # Local file is present but possibly older (taking the possible
            # deviation because of the precision into account), so should
            # download.
            downloaded = host.download_if_newer(remote_file, local_file)
            assert downloaded is True
        finally:
            # Clean up.
            os.unlink(local_file)

    def test_callback_with_transfer(self):
        """
        A `callback` argument should be called during a file transfer.
        """
        host = self.host
        FILE_NAME = "large_file"
        # Default chunk size as in `FTPHost.copyfileobj`
        MAX_COPY_CHUNK_SIZE = ftputil.file_transfer.MAX_COPY_CHUNK_SIZE
        file_size = host.path.getsize(FILE_NAME)
        chunk_count, _ = divmod(file_size, MAX_COPY_CHUNK_SIZE)
        # Add one chunk for remainder.
        chunk_count += 1
        # Define a callback that just collects all data passed to it.
        transferred_chunks_list = []

        def test_callback(chunk):
            transferred_chunks_list.append(chunk)

        try:
            host.download(FILE_NAME, FILE_NAME, callback=test_callback)
            # Construct a list of data chunks we expect.
            expected_chunks_list = []
            with open(FILE_NAME, "rb") as downloaded_fobj:
                while True:
                    chunk = downloaded_fobj.read(MAX_COPY_CHUNK_SIZE)
                    if not chunk:
                        break
                    expected_chunks_list.append(chunk)
            # Examine data collected by callback function.
            assert len(transferred_chunks_list) == chunk_count
            assert transferred_chunks_list == expected_chunks_list
        finally:
            os.unlink(FILE_NAME)


class TestFTPFiles(RealFTPTest):
    def test_only_closed_children(self):
        """
        If `FTPHost.open` needs an `FTPFile` object, an existing closed
        `FTPFile` should be reused.
        """
        REMOTE_FILE_NAME = "CONTENTS"
        host = self.host
        with host.open(REMOTE_FILE_NAME, "rb") as file_obj1:
            # Create empty file and close it.
            with host.open(REMOTE_FILE_NAME, "rb") as file_obj2:
                pass
            # This should re-use the second child because the first isn't
            # closed but the second is.
            with host.open(REMOTE_FILE_NAME, "rb") as file_obj:
                assert len(host._children) == 2
                assert file_obj._host is host._children[1]

    def test_no_timed_out_children(self):
        """
        `FTPHost.open` shouldn't use an `FTPFile` object that has timed out.
        """
        REMOTE_FILE_NAME = "CONTENTS"
        host = self.host
        # Implicitly create child host object.
        with host.open(REMOTE_FILE_NAME, "rb") as file_obj1:
            pass
        # Monkey-patch file to simulate an FTP server timeout below.
        def timed_out_pwd():
            raise ftplib.error_temp("simulated timeout")

        file_obj1._host._session.pwd = timed_out_pwd
        # Try to get a file - which shouldn't be the timed-out file.
        with host.open(REMOTE_FILE_NAME, "rb") as file_obj2:
            assert file_obj1 is not file_obj2
        # Re-use closed and not timed-out child session.
        with host.open(REMOTE_FILE_NAME, "rb") as file_obj3:
            pass
        assert file_obj2 is file_obj3

    def test_no_delayed_226_children(self):
        """
        `FTPHost.open` shouldn't use an `FTPFile` object that gave an 226 error
        reply.
        """
        REMOTE_FILE_NAME = "CONTENTS"
        host = self.host
        # Implicitly create child host object.
        with host.open(REMOTE_FILE_NAME, "rb") as file_obj1:
            pass
        # Monkey-patch file to simulate an FTP server timeout below.
        def timed_out_pwd():
            raise ftplib.error_reply("delayed 226 reply")

        file_obj1._host._session.pwd = timed_out_pwd
        # Try to get a file - which shouldn't be the timed-out file.
        with host.open(REMOTE_FILE_NAME, "rb") as file_obj2:
            assert file_obj1 is not file_obj2
        # Re-use closed and not timed-out child session.
        with host.open(REMOTE_FILE_NAME, "rb") as file_obj3:
            pass
        assert file_obj2 is file_obj3


class TestChmod(RealFTPTest):
    def assert_mode(self, path, expected_mode):
        """
        Return an integer containing the allowed bits in the mode change
        command.

        The `FTPHost` object to test against is `self.host`.
        """
        full_mode = self.host.stat(path).st_mode
        # Remove flags we can't set via `chmod`. Allowed flags according to
        # Python documentation: https://docs.python.org/library/stat.html
        allowed_flags = [
            stat.S_ISUID,
            stat.S_ISGID,
            stat.S_ENFMT,
            stat.S_ISVTX,
            stat.S_IREAD,
            stat.S_IWRITE,
            stat.S_IEXEC,
            stat.S_IRWXU,
            stat.S_IRUSR,
            stat.S_IWUSR,
            stat.S_IXUSR,
            stat.S_IRWXG,
            stat.S_IRGRP,
            stat.S_IWGRP,
            stat.S_IXGRP,
            stat.S_IRWXO,
            stat.S_IROTH,
            stat.S_IWOTH,
            stat.S_IXOTH,
        ]
        allowed_mask = functools.reduce(operator.or_, allowed_flags)
        mode = full_mode & allowed_mask
        assert mode == expected_mode, "mode {0:o} != {1:o}".format(mode, expected_mode)

    def test_chmod_existing_directory(self):
        """
        A `chmod` operation on a writable existing directory should succeed.
        """
        host = self.host
        host.mkdir("_test dir_")
        self.cleaner.add_dir("_test dir_")
        # Set/get mode of a directory.
        host.chmod("_test dir_", 0o757)
        self.assert_mode("_test dir_", 0o757)
        # Set/get mode in nested directory.
        host.mkdir("_test dir_/nested_dir")
        self.cleaner.add_dir("_test dir_/nested_dir")
        host.chmod("_test dir_/nested_dir", 0o757)
        self.assert_mode("_test dir_/nested_dir", 0o757)

    def test_chmod_existing_file(self):
        """
        A `chmod` operation on a writable existing file should succeed.
        """
        host = self.host
        host.mkdir("_test dir_")
        self.cleaner.add_dir("_test dir_")
        # Set/get mode on a file.
        file_name = host.path.join("_test dir_", "_testfile_")
        self.make_remote_file(file_name)
        host.chmod(file_name, 0o646)
        self.assert_mode(file_name, 0o646)

    def test_chmod_nonexistent_path(self):
        """
        If `chmod` is called on a non-existent path, a `PermanentError` should
        be raised.
        """
        # Set/get mode of a non-existing item.
        with pytest.raises(ftputil.error.PermanentError):
            self.host.chmod("nonexistent", 0o757)

    def test_cache_invalidation(self):
        """
        If the mode of a directory or file is changed, make sure that the cache
        doesn't contain stat entries before the `chmod` call.
        """
        host = self.host
        host.mkdir("_test dir_")
        self.cleaner.add_dir("_test dir_")
        # Make sure the mode is in the cache.
        unused_stat_result = host.stat("_test dir_")
        # Set/get mode of the directory.
        host.chmod("_test dir_", 0o757)
        self.assert_mode("_test dir_", 0o757)
        # Set/get mode on a file.
        file_name = host.path.join("_test dir_", "_testfile_")
        self.make_remote_file(file_name)
        # Make sure the mode is in the cache.
        unused_stat_result = host.stat(file_name)
        host.chmod(file_name, 0o646)
        self.assert_mode(file_name, 0o646)


class TestRestArgument(RealFTPTest):

    TEST_FILE_NAME = "rest_test"

    def setup_method(self, method):
        super().setup_method(method)
        # Write test file.
        with self.host.open(self.TEST_FILE_NAME, "wb") as fobj:
            fobj.write(b"abcdefghijkl")
        self.cleaner.add_file(self.TEST_FILE_NAME)

    def test_for_reading(self):
        """
        If a `rest` argument is passed to `open`, the following read operation
        should start at the byte given by `rest`.
        """
        with self.host.open(self.TEST_FILE_NAME, "rb", rest=3) as fobj:
            data = fobj.read()
        assert data == b"defghijkl"

    def test_for_writing(self):
        """
        If a `rest` argument is passed to `open`, the following write operation
        should start writing at the byte given by `rest`.
        """
        with self.host.open(self.TEST_FILE_NAME, "wb", rest=3) as fobj:
            fobj.write(b"123")
        with self.host.open(self.TEST_FILE_NAME, "rb") as fobj:
            data = fobj.read()
        assert data == b"abc123"

    def test_invalid_read_from_text_file(self):
        """
        If the `rest` argument is used for reading from a text file, a
        `CommandNotImplementedError` should be raised.
        """
        with pytest.raises(ftputil.error.CommandNotImplementedError):
            self.host.open(self.TEST_FILE_NAME, "r", rest=3)

    def test_invalid_write_to_text_file(self):
        """
        If the `rest` argument is used for reading from a text file, a
        `CommandNotImplementedError` should be raised.
        """
        with pytest.raises(ftputil.error.CommandNotImplementedError):
            self.host.open(self.TEST_FILE_NAME, "w", rest=3)

    # There are no tests for reading and writing beyond the end of a file. For
    # example, if the remote file is 10 bytes long and
    # `open(remote_file, "rb", rest=100)` is used, the server may return an
    # error status code or not.
    #
    # The server I use for testing returns a 554 status when attempting to
    # _read_ beyond the end of the file. On the other hand, if attempting to
    # _write_ beyond the end of the file, the server accepts the request, but
    # starts writing after the end of the file, i. e. appends to the file.
    #
    # Instead of expecting certain responses that may differ between server
    # implementations, I leave the bahavior for too large `rest` arguments
    # undefined. In practice, this shouldn't be a problem because the `rest`
    # argument should only be used for error recovery, and in this case a valid
    # byte count for the `rest` argument should be known.


class TestOther(RealFTPTest):
    def test_open_for_reading(self):
        # Test for issues #17 and #51,
        # http://ftputil.sschwarzer.net/trac/ticket/17 and
        # http://ftputil.sschwarzer.net/trac/ticket/51 .
        file1 = self.host.open("large_file", "rb")
        time.sleep(1)
        # Depending on the FTP server, this might return a status code
        # unexpected by `ftplib` or block the socket connection until a
        # server-side timeout.
        file1.close()

    def test_subsequent_reading(self):
        """
        An `FTPHost.open` call should reuse a closed `FTPFile`.
        """
        # Open a file for reading.
        with self.host.open("CONTENTS", "rb") as file1:
            pass
        # Make sure that there are no problems if the connection is reused.
        with self.host.open("CONTENTS", "rb") as file2:
            pass
        assert file1._session is file2._session

    def test_names_with_spaces(self):
        """
        Directory and file names with spaces in them shouldn't cause problems.

        (We've seen problems here with some servers before
        `_robust_ftp_command` was introduced.)
        """
        host = self.host
        assert host.path.isdir("dir with spaces")
        assert host.listdir("dir with spaces") == [
            "second dir",
            "some file",
            "some_file",
        ]
        assert host.path.isdir("dir with spaces/second dir")
        assert host.path.isfile("dir with spaces/some_file")
        assert host.path.isfile("dir with spaces/some file")

    def test_synchronize_times_without_write_access(self):
        """
        If the current directory isn't writable, `synchronize_times` should
        raise a `TimeShiftError`.
        """
        host = self.host
        # This isn't writable by the ftp account the tests are run under.
        host.chdir("rootdir1")
        with pytest.raises(ftputil.error.TimeShiftError):
            host.synchronize_times()

    def test_encoding(self):
        """
        If the session factory is requested with a specific encoding, the
        session from the factory should use this requested encoding.
        """
        for encoding in ["latin-1", "UTF-8"]:
            factory = ftputil.session.session_factory(port=PORT, encoding=encoding)
            session = factory(*self.login_data)
            assert session.encoding == encoding

    def test_listdir_with_non_ascii_byte_string(self):
        """
        `listdir` should accept byte strings with non-ASCII characters and
        return non-ASCII characters in directory or file names.
        """
        host = self.host
        path = "äbc".encode("UTF-8")
        names = host.listdir(path)
        assert names[0] == b"file1"
        assert names[1] == "file1_ö".encode("UTF-8")

    def test_listdir_with_non_ascii_unicode_string(self):
        """
        `listdir` should accept unicode strings with non-ASCII characters and
        return non-ASCII characters in directory or file names.
        """
        host = self.host
        # `ftplib` under Python 3 only works correctly if the unicode strings
        # are decoded from the `ftplib` default encoding. For Python 3.9 and up
        # the `encode`/`decode` combination is a no-op.
        path = "äbc".encode("UTF-8").decode(
            ftputil.path_encoding.FTPLIB_DEFAULT_ENCODING
        )
        names = host.listdir(path)
        assert names[0] == "file1"
        assert names[1] == "file1_ö".encode("UTF-8").decode(
            ftputil.path_encoding.FTPLIB_DEFAULT_ENCODING
        )

    @pytest.mark.skipif(
        ftputil.path_encoding.RUNNING_UNDER_PY39_AND_UP,
        reason="test applies only to `FTPHost` objects using 'latin-1' path encoding",
    )
    def test_path_with_non_latin1_unicode_string_below_python_3_9(self):
        """
        ftputil operations shouldn't accept file paths with non-latin1
        characters.
        """
        # Use some musical symbols. These are certainly not latin1. ;-)
        path = "𝄞𝄢"
        # `UnicodeEncodeError` is also the exception that `ftplib` raises if it
        # gets a non-latin1 path.
        with pytest.raises(UnicodeEncodeError):
            self.host.mkdir(path)

    def test_list_a_option(self):
        """
        If `use_list_a_option` is set to `False`, "hidden" files shouldn't be
        included in the `listdir` result.

        If `use_list_a_option` is set to `True`, "hidden" files should be
        included in the `listdir` result.

        Whether this works as described, depends on the FTP server and its
        configuration.
        """
        # For this test to pass, the server must _not_ list "hidden" files by
        # default but instead only when the `LIST` `-a` option is used.
        host = self.host
        assert not host.use_list_a_option
        directory_entries = host.listdir(host.curdir)
        assert ".hidden" not in directory_entries
        # Switch on showing of hidden paths.
        host.use_list_a_option = True
        directory_entries = host.listdir(host.curdir)
        assert ".hidden" in directory_entries

    def _make_objects_to_be_garbage_collected(self):
        for _ in range(10):
            with ftputil.FTPHost(
                *self.login_data, session_factory=DEFAULT_SESSION_FACTORY
            ) as host:
                for _ in range(10):
                    unused_stat_result = host.stat("CONTENTS")
                    with host.open("CONTENTS") as fobj:
                        unused_data = fobj.read()

    def test_garbage_collection(self):
        """
        Test whether there are cycles which prevent garbage collection.
        """
        gc.collect()
        objects_before_test = len(gc.garbage)
        self._make_objects_to_be_garbage_collected()
        gc.collect()
        objects_after_test = len(gc.garbage)
        assert not objects_after_test - objects_before_test