path: root/lib/ansible/utils/display.py

# (c) 2014, Michael DeHaan <michael.dehaan@gmail.com>
#
# This file is part of Ansible
#
# Ansible is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# Ansible is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with Ansible.  If not, see <http://www.gnu.org/licenses/>.

from __future__ import (absolute_import, division, print_function)
__metaclass__ = type

try:
    import curses
except ImportError:
    HAS_CURSES = False
else:
    # this will be set to False if curses.setupterm() fails
    HAS_CURSES = True

import codecs
import ctypes.util
import fcntl
import getpass
import io
import logging
import os
import random
import subprocess
import sys
import termios
import textwrap
import threading
import time
import tty
import typing as t

from functools import wraps
from struct import unpack, pack

from ansible import constants as C
from ansible.errors import AnsibleError, AnsibleAssertionError, AnsiblePromptInterrupt, AnsiblePromptNoninteractive
from ansible.module_utils._text import to_bytes, to_text
from ansible.module_utils.six import text_type
from ansible.utils.color import stringc
from ansible.utils.multiprocessing import context as multiprocessing_context
from ansible.utils.singleton import Singleton
from ansible.utils.unsafe_proxy import wrap_var

_LIBC = ctypes.cdll.LoadLibrary(ctypes.util.find_library('c'))
# Set argtypes, to avoid segfault if the wrong type is provided,
# restype is assumed to be c_int
_LIBC.wcwidth.argtypes = (ctypes.c_wchar,)
_LIBC.wcswidth.argtypes = (ctypes.c_wchar_p, ctypes.c_int)
# Max for c_int
_MAX_INT = 2 ** (ctypes.sizeof(ctypes.c_int) * 8 - 1) - 1

MOVE_TO_BOL = b'\r'
CLEAR_TO_EOL = b'\x1b[K'


def get_text_width(text):
    """Function that utilizes ``wcswidth`` or ``wcwidth`` to determine the
    number of columns used to display a text string.

    We try first with ``wcswidth``, and fallback to iterating each
    character and using wcwidth individually, falling back to a value of 0
    for non-printable wide characters.
    """
    if not isinstance(text, text_type):
        raise TypeError('get_text_width requires text, not %s' % type(text))

    try:
        width = _LIBC.wcswidth(text, _MAX_INT)
    except ctypes.ArgumentError:
        width = -1
    if width != -1:
        return width

    width = 0
    counter = 0
    for c in text:
        counter += 1
        if c in (u'\x08', u'\x7f', u'\x94', u'\x1b'):
            # A few characters result in a subtraction of length:
            # BS, DEL, CCH, ESC
            # ESC is slightly different in that it's part of an escape sequence, and
            # while ESC is non printable, it's part of an escape sequence, which results
            # in a single non printable length
            width -= 1
            counter -= 1
            continue

        try:
            w = _LIBC.wcwidth(c)
        except ctypes.ArgumentError:
            w = -1
        if w == -1:
            # -1 signifies a non-printable character
            # use 0 here as a best effort
            w = 0
        width += w

    if width == 0 and counter:
        raise EnvironmentError(
            'get_text_width could not calculate text width of %r' % text
        )

    # It doesn't make sense to have a negative printable width
    return width if width >= 0 else 0


class FilterBlackList(logging.Filter):
    def __init__(self, blacklist):
        self.blacklist = [logging.Filter(name) for name in blacklist]

    def filter(self, record):
        return not any(f.filter(record) for f in self.blacklist)


class FilterUserInjector(logging.Filter):
    """
    This is a filter which injects the current user as the 'user' attribute on each record. We need to add this filter
    to all logger handlers so that 3rd party libraries won't print an exception due to user not being defined.
    """

    try:
        username = getpass.getuser()
    except KeyError:
        # people like to make containers w/o actual valid passwd/shadow and use host uids
        username = 'uid=%s' % os.getuid()

    def filter(self, record):
        record.user = FilterUserInjector.username
        return True


logger = None
# TODO: make this a callback event instead
if getattr(C, 'DEFAULT_LOG_PATH'):
    path = C.DEFAULT_LOG_PATH
    if path and (os.path.exists(path) and os.access(path, os.W_OK)) or os.access(os.path.dirname(path), os.W_OK):
        # NOTE: level is kept at INFO to avoid security disclosures caused by certain libraries when using DEBUG
        logging.basicConfig(filename=path, level=logging.INFO,  # DO NOT set to logging.DEBUG
                            format='%(asctime)s p=%(process)d u=%(user)s n=%(name)s | %(message)s')

        logger = logging.getLogger('ansible')
        for handler in logging.root.handlers:
            handler.addFilter(FilterBlackList(getattr(C, 'DEFAULT_LOG_FILTER', [])))
            handler.addFilter(FilterUserInjector())
    else:
        print("[WARNING]: log file at %s is not writeable and we cannot create it, aborting\n" % path, file=sys.stderr)

# map color to log levels
color_to_log_level = {C.COLOR_ERROR: logging.ERROR,
                      C.COLOR_WARN: logging.WARNING,
                      C.COLOR_OK: logging.INFO,
                      C.COLOR_SKIP: logging.WARNING,
                      C.COLOR_UNREACHABLE: logging.ERROR,
                      C.COLOR_DEBUG: logging.DEBUG,
                      C.COLOR_CHANGED: logging.INFO,
                      C.COLOR_DEPRECATE: logging.WARNING,
                      C.COLOR_VERBOSE: logging.INFO}

b_COW_PATHS = (
    b"/usr/bin/cowsay",
    b"/usr/games/cowsay",
    b"/usr/local/bin/cowsay",  # BSD path for cowsay
    b"/opt/local/bin/cowsay",  # MacPorts path for cowsay
)


def _synchronize_textiowrapper(tio, lock):
    # Ensure that a background thread can't hold the internal buffer lock on a file object
    # during a fork, which causes forked children to hang. We're using display's existing lock for
    # convenience (and entering the lock before a fork).
    def _wrap_with_lock(f, lock):
        @wraps(f)
        def locking_wrapper(*args, **kwargs):
            with lock:
                return f(*args, **kwargs)

        return locking_wrapper

    buffer = tio.buffer

    # monkeypatching the underlying file-like object isn't great, but likely safer than subclassing
    buffer.write = _wrap_with_lock(buffer.write, lock)
    buffer.flush = _wrap_with_lock(buffer.flush, lock)


def setraw(fd, when=termios.TCSAFLUSH):
    """Put terminal into a raw mode.

    Copied from ``tty`` from CPython 3.11.0, and modified to not remove OPOST from OFLAG

    OPOST is kept to prevent an issue with multi line prompts from being corrupted now that display
    is proxied via the queue from forks. The problem is a race condition, in that we proxy the display
    over the fork, but before it can be displayed, this plugin will have continued executing, potentially
    setting stdout and stdin to raw which remove output post processing that commonly converts NL to CRLF
    """
    mode = termios.tcgetattr(fd)
    mode[tty.IFLAG] = mode[tty.IFLAG] & ~(termios.BRKINT | termios.ICRNL | termios.INPCK | termios.ISTRIP | termios.IXON)
    mode[tty.OFLAG] = mode[tty.OFLAG] & ~(termios.OPOST)
    mode[tty.CFLAG] = mode[tty.CFLAG] & ~(termios.CSIZE | termios.PARENB)
    mode[tty.CFLAG] = mode[tty.CFLAG] | termios.CS8
    mode[tty.LFLAG] = mode[tty.LFLAG] & ~(termios.ECHO | termios.ICANON | termios.IEXTEN | termios.ISIG)
    mode[tty.CC][termios.VMIN] = 1
    mode[tty.CC][termios.VTIME] = 0
    termios.tcsetattr(fd, when, mode)


def clear_line(stdout):
    stdout.write(b'\x1b[%s' % MOVE_TO_BOL)
    stdout.write(b'\x1b[%s' % CLEAR_TO_EOL)


def setup_prompt(stdin_fd, stdout_fd, seconds, echo):
    # type: (int, int, int, bool) -> None
    setraw(stdin_fd)

    # Only set stdout to raw mode if it is a TTY. This is needed when redirecting
    # stdout to a file since a file cannot be set to raw mode.
    if os.isatty(stdout_fd):
        setraw(stdout_fd)

    if echo:
        new_settings = termios.tcgetattr(stdin_fd)
        new_settings[3] = new_settings[3] | termios.ECHO
        termios.tcsetattr(stdin_fd, termios.TCSANOW, new_settings)


def setupterm():
    # Nest the try except since curses.error is not available if curses did not import
    try:
        curses.setupterm()
    except (curses.error, TypeError, io.UnsupportedOperation):
        global HAS_CURSES
        HAS_CURSES = False
    else:
        global MOVE_TO_BOL
        global CLEAR_TO_EOL
        # curses.tigetstr() returns None in some circumstances
        MOVE_TO_BOL = curses.tigetstr('cr') or MOVE_TO_BOL
        CLEAR_TO_EOL = curses.tigetstr('el') or CLEAR_TO_EOL


class Display(metaclass=Singleton):

    def __init__(self, verbosity=0):

        self._final_q = None

        # NB: this lock is used to both prevent intermingled output between threads and to block writes during forks.
        # Do not change the type of this lock or upgrade to a shared lock (eg multiprocessing.RLock).
        self._lock = threading.RLock()

        self.columns = None
        self.verbosity = verbosity

        # list of all deprecation messages to prevent duplicate display
        self._deprecations = {}
        self._warns = {}
        self._errors = {}

        self.b_cowsay = None
        self.noncow = C.ANSIBLE_COW_SELECTION

        self.set_cowsay_info()

        if self.b_cowsay:
            try:
                cmd = subprocess.Popen([self.b_cowsay, "-l"], stdout=subprocess.PIPE, stderr=subprocess.PIPE)
                (out, err) = cmd.communicate()
                if cmd.returncode:
                    raise Exception
                self.cows_available = {to_text(c) for c in out.split()}  # set comprehension
                if C.ANSIBLE_COW_ACCEPTLIST and any(C.ANSIBLE_COW_ACCEPTLIST):
                    self.cows_available = set(C.ANSIBLE_COW_ACCEPTLIST).intersection(self.cows_available)
            except Exception:
                # could not execute cowsay for some reason
                self.b_cowsay = False

        self._set_column_width()

        try:
            # NB: we're relying on the display singleton behavior to ensure this only runs once
            _synchronize_textiowrapper(sys.stdout, self._lock)
            _synchronize_textiowrapper(sys.stderr, self._lock)
        except Exception as ex:
            self.warning(f"failed to patch stdout/stderr for fork-safety: {ex}")

        codecs.register_error('_replacing_warning_handler', self._replacing_warning_handler)
        try:
            sys.stdout.reconfigure(errors='_replacing_warning_handler')
            sys.stderr.reconfigure(errors='_replacing_warning_handler')
        except Exception as ex:
            self.warning(f"failed to reconfigure stdout/stderr with custom encoding error handler: {ex}")

        self.setup_curses = False

    def _replacing_warning_handler(self, exception):
        # TODO: This should probably be deferred until after the current display is completed
        #       this will require some amount of new functionality
        self.deprecated(
            'Non UTF-8 encoded data replaced with "?" while displaying text to stdout/stderr, this is temporary and will become an error',
            version='2.18',
        )
        return '?', exception.end

    def set_queue(self, queue):
        """Set the _final_q on Display, so that we know to proxy display over the queue
        instead of directly writing to stdout/stderr from forks

        This is only needed in ansible.executor.process.worker:WorkerProcess._run
        """
        if multiprocessing_context.parent_process() is None:
            raise RuntimeError('queue cannot be set in parent process')
        self._final_q = queue

    def set_cowsay_info(self):
        if C.ANSIBLE_NOCOWS:
            return

        if C.ANSIBLE_COW_PATH:
            self.b_cowsay = C.ANSIBLE_COW_PATH
        else:
            for b_cow_path in b_COW_PATHS:
                if os.path.exists(b_cow_path):
                    self.b_cowsay = b_cow_path

    def display(self, msg, color=None, stderr=False, screen_only=False, log_only=False, newline=True):
        """ Display a message to the user

        Note: msg *must* be a unicode string to prevent UnicodeError tracebacks.
        """

        if not isinstance(msg, str):
            raise TypeError(f'Display message must be str, not: {msg.__class__.__name__}')

        if self._final_q:
            # If _final_q is set, that means we are in a WorkerProcess
            # and instead of displaying messages directly from the fork
            # we will proxy them through the queue
            return self._final_q.send_display(msg, color=color, stderr=stderr,
                                              screen_only=screen_only, log_only=log_only, newline=newline)

        nocolor = msg

        if not log_only:

            has_newline = msg.endswith(u'\n')
            if has_newline:
                msg2 = msg[:-1]
            else:
                msg2 = msg

            if color:
                msg2 = stringc(msg2, color)

            if has_newline or newline:
                msg2 = msg2 + u'\n'

            # Note: After Display() class is refactored need to update the log capture
            # code in 'bin/ansible-connection' (and other relevant places).
            if not stderr:
                fileobj = sys.stdout
            else:
                fileobj = sys.stderr

            with self._lock:
                fileobj.write(msg2)

            # With locks, and the fact that we aren't printing from forks
            # just write, and let the system flush. Everything should come out peachy
            # I've left this code for historical purposes, or in case we need to add this
            # back at a later date. For now ``TaskQueueManager.cleanup`` will perform a
            # final flush at shutdown.
            # try:
            #     fileobj.flush()
            # except IOError as e:
            #     # Ignore EPIPE in case fileobj has been prematurely closed, eg.
            #     # when piping to "head -n1"
            #     if e.errno != errno.EPIPE:
            #         raise

        if logger and not screen_only:
            msg2 = nocolor.lstrip('\n')

            lvl = logging.INFO
            if color:
                # set logger level based on color (not great)
                try:
                    lvl = color_to_log_level[color]
                except KeyError:
                    # this should not happen, but JIC
                    raise AnsibleAssertionError('Invalid color supplied to display: %s' % color)
            # actually log
            logger.log(lvl, msg2)

    def v(self, msg, host=None):
        return self.verbose(msg, host=host, caplevel=0)

    def vv(self, msg, host=None):
        return self.verbose(msg, host=host, caplevel=1)

    def vvv(self, msg, host=None):
        return self.verbose(msg, host=host, caplevel=2)

    def vvvv(self, msg, host=None):
        return self.verbose(msg, host=host, caplevel=3)

    def vvvvv(self, msg, host=None):
        return self.verbose(msg, host=host, caplevel=4)

    def vvvvvv(self, msg, host=None):
        return self.verbose(msg, host=host, caplevel=5)

    def debug(self, msg, host=None):
        if C.DEFAULT_DEBUG:
            if host is None:
                self.display("%6d %0.5f: %s" % (os.getpid(), time.time(), msg), color=C.COLOR_DEBUG)
            else:
                self.display("%6d %0.5f [%s]: %s" % (os.getpid(), time.time(), host, msg), color=C.COLOR_DEBUG)

    def verbose(self, msg, host=None, caplevel=2):

        to_stderr = C.VERBOSE_TO_STDERR
        if self.verbosity > caplevel:
            if host is None:
                self.display(msg, color=C.COLOR_VERBOSE, stderr=to_stderr)
            else:
                self.display("<%s> %s" % (host, msg), color=C.COLOR_VERBOSE, stderr=to_stderr)

    def get_deprecation_message(self, msg, version=None, removed=False, date=None, collection_name=None):
        ''' used to print out a deprecation message.'''
        msg = msg.strip()
        if msg and msg[-1] not in ['!', '?', '.']:
            msg += '.'

        if collection_name == 'ansible.builtin':
            collection_name = 'ansible-core'

        if removed:
            header = '[DEPRECATED]: {0}'.format(msg)
            removal_fragment = 'This feature was removed'
            help_text = 'Please update your playbooks.'
        else:
            header = '[DEPRECATION WARNING]: {0}'.format(msg)
            removal_fragment = 'This feature will be removed'
            # FUTURE: make this a standalone warning so it only shows up once?
            help_text = 'Deprecation warnings can be disabled by setting deprecation_warnings=False in ansible.cfg.'

        if collection_name:
            from_fragment = 'from {0}'.format(collection_name)
        else:
            from_fragment = ''

        if date:
            when = 'in a release after {0}.'.format(date)
        elif version:
            when = 'in version {0}.'.format(version)
        else:
            when = 'in a future release.'

        message_text = ' '.join(f for f in [header, removal_fragment, from_fragment, when, help_text] if f)

        return message_text

    def deprecated(self, msg, version=None, removed=False, date=None, collection_name=None):
        if not removed and not C.DEPRECATION_WARNINGS:
            return

        message_text = self.get_deprecation_message(msg, version=version, removed=removed, date=date, collection_name=collection_name)

        if removed:
            raise AnsibleError(message_text)

        wrapped = textwrap.wrap(message_text, self.columns, drop_whitespace=False)
        message_text = "\n".join(wrapped) + "\n"

        if message_text not in self._deprecations:
            self.display(message_text.strip(), color=C.COLOR_DEPRECATE, stderr=True)
            self._deprecations[message_text] = 1

    def warning(self, msg, formatted=False):

        if not formatted:
            new_msg = "[WARNING]: %s" % msg
            wrapped = textwrap.wrap(new_msg, self.columns)
            new_msg = "\n".join(wrapped) + "\n"
        else:
            new_msg = "\n[WARNING]: \n%s" % msg

        if new_msg not in self._warns:
            self.display(new_msg, color=C.COLOR_WARN, stderr=True)
            self._warns[new_msg] = 1

    def system_warning(self, msg):
        if C.SYSTEM_WARNINGS:
            self.warning(msg)

    def banner(self, msg, color=None, cows=True):
        '''
        Prints a header-looking line with cowsay or stars with length depending on terminal width (3 minimum)
        '''
        msg = to_text(msg)

        if self.b_cowsay and cows:
            try:
                self.banner_cowsay(msg)
                return
            except OSError:
                self.warning("somebody cleverly deleted cowsay or something during the PB run.  heh.")

        msg = msg.strip()
        try:
            star_len = self.columns - get_text_width(msg)
        except EnvironmentError:
            star_len = self.columns - len(msg)
        if star_len <= 3:
            star_len = 3
        stars = u"*" * star_len
        self.display(u"\n%s %s" % (msg, stars), color=color)

    def banner_cowsay(self, msg, color=None):
        if u": [" in msg:
            msg = msg.replace(u"[", u"")
            if msg.endswith(u"]"):
                msg = msg[:-1]
        runcmd = [self.b_cowsay, b"-W", b"60"]
        if self.noncow:
            thecow = self.noncow
            if thecow == 'random':
                thecow = random.choice(list(self.cows_available))
            runcmd.append(b'-f')
            runcmd.append(to_bytes(thecow))
        runcmd.append(to_bytes(msg))
        cmd = subprocess.Popen(runcmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
        (out, err) = cmd.communicate()
        self.display(u"%s\n" % to_text(out), color=color)

    def error(self, msg, wrap_text=True):
        if wrap_text:
            new_msg = u"\n[ERROR]: %s" % msg
            wrapped = textwrap.wrap(new_msg, self.columns)
            new_msg = u"\n".join(wrapped) + u"\n"
        else:
            new_msg = u"ERROR! %s" % msg
        if new_msg not in self._errors:
            self.display(new_msg, color=C.COLOR_ERROR, stderr=True)
            self._errors[new_msg] = 1

    @staticmethod
    def prompt(msg, private=False):
        if private:
            return getpass.getpass(msg)
        else:
            return input(msg)

    def do_var_prompt(self, varname, private=True, prompt=None, encrypt=None, confirm=False, salt_size=None, salt=None, default=None, unsafe=None):

        result = None
        if sys.__stdin__.isatty():

            do_prompt = self.prompt

            if prompt and default is not None:
                msg = "%s [%s]: " % (prompt, default)
            elif prompt:
                msg = "%s: " % prompt
            else:
                msg = 'input for %s: ' % varname

            if confirm:
                while True:
                    result = do_prompt(msg, private)
                    second = do_prompt("confirm " + msg, private)
                    if result == second:
                        break
                    self.display("***** VALUES ENTERED DO NOT MATCH ****")
            else:
                result = do_prompt(msg, private)
        else:
            result = None
            self.warning("Not prompting as we are not in interactive mode")

        # if result is false and default is not None
        if not result and default is not None:
            result = default

        if encrypt:
            # Circular import because encrypt needs a display class
            from ansible.utils.encrypt import do_encrypt
            result = do_encrypt(result, encrypt, salt_size, salt)

        # handle utf-8 chars
        result = to_text(result, errors='surrogate_or_strict')

        if unsafe:
            result = wrap_var(result)
        return result

    def _set_column_width(self):
        if os.isatty(1):
            tty_size = unpack('HHHH', fcntl.ioctl(1, termios.TIOCGWINSZ, pack('HHHH', 0, 0, 0, 0)))[1]
        else:
            tty_size = 0
        self.columns = max(79, tty_size - 1)

    def prompt_until(self, msg, private=False, seconds=None, interrupt_input=None, complete_input=None):
        if self._final_q:
            from ansible.executor.process.worker import current_worker
            self._final_q.send_prompt(
                worker_id=current_worker.worker_id, prompt=msg, private=private, seconds=seconds,
                interrupt_input=interrupt_input, complete_input=complete_input
            )
            return current_worker.worker_queue.get()

        if HAS_CURSES and not self.setup_curses:
            setupterm()
            self.setup_curses = True

        if (
            self._stdin_fd is None
            or not os.isatty(self._stdin_fd)
            # Compare the current process group to the process group associated
            # with terminal of the given file descriptor to determine if the process
            # is running in the background.
            or os.getpgrp() != os.tcgetpgrp(self._stdin_fd)
        ):
            raise AnsiblePromptNoninteractive('stdin is not interactive')

        # When seconds/interrupt_input/complete_input are all None, this does mostly the same thing as input/getpass,
        # but self.prompt may raise a KeyboardInterrupt, which must be caught in the main thread.
        # If the main thread handled this, it would also need to send a newline to the tty of any hanging pids.
        # if seconds is None and interrupt_input is None and complete_input is None:
        #     try:
        #         return self.prompt(msg, private=private)
        #     except KeyboardInterrupt:
        #         # can't catch in the results_thread_main daemon thread
        #         raise AnsiblePromptInterrupt('user interrupt')

        self.display(msg)
        result = b''
        with self._lock:
            original_stdin_settings = termios.tcgetattr(self._stdin_fd)
            try:
                setup_prompt(self._stdin_fd, self._stdout_fd, seconds, not private)

                # flush the buffer to make sure no previous key presses
                # are read in below
                termios.tcflush(self._stdin, termios.TCIFLUSH)

                # read input 1 char at a time until the optional timeout or complete/interrupt condition is met
                return self._read_non_blocking_stdin(echo=not private, seconds=seconds, interrupt_input=interrupt_input, complete_input=complete_input)
            finally:
                # restore the old settings for the duped stdin stdin_fd
                termios.tcsetattr(self._stdin_fd, termios.TCSADRAIN, original_stdin_settings)

    def _read_non_blocking_stdin(
        self,
        echo=False,  # type: bool
        seconds=None,  # type: int
        interrupt_input=None,  # type: t.Iterable[bytes]
        complete_input=None,  # type: t.Iterable[bytes]
    ):  # type: (...) -> bytes

        if self._final_q:
            raise NotImplementedError

        if seconds is not None:
            start = time.time()
        if interrupt_input is None:
            try:
                interrupt = termios.tcgetattr(sys.stdin.buffer.fileno())[6][termios.VINTR]
            except Exception:
                interrupt = b'\x03'  # value for Ctrl+C

        try:
            backspace_sequences = [termios.tcgetattr(self._stdin_fd)[6][termios.VERASE]]
        except Exception:
            # unsupported/not present, use default
            backspace_sequences = [b'\x7f', b'\x08']

        result_string = b''
        while seconds is None or (time.time() - start < seconds):
            key_pressed = None
            try:
                os.set_blocking(self._stdin_fd, False)
                while key_pressed is None and (seconds is None or (time.time() - start < seconds)):
                    key_pressed = self._stdin.read(1)
            finally:
                os.set_blocking(self._stdin_fd, True)
                if key_pressed is None:
                    key_pressed = b''

            if (interrupt_input is None and key_pressed == interrupt) or (interrupt_input is not None and key_pressed.lower() in interrupt_input):
                clear_line(self._stdout)
                raise AnsiblePromptInterrupt('user interrupt')
            if (complete_input is None and key_pressed in (b'\r', b'\n')) or (complete_input is not None and key_pressed.lower() in complete_input):
                clear_line(self._stdout)
                break
            elif key_pressed in backspace_sequences:
                clear_line(self._stdout)
                result_string = result_string[:-1]
                if echo:
                    self._stdout.write(result_string)
                self._stdout.flush()
            else:
                result_string += key_pressed
        return result_string

    @property
    def _stdin(self):
        if self._final_q:
            raise NotImplementedError
        try:
            return sys.stdin.buffer
        except AttributeError:
            return None

    @property
    def _stdin_fd(self):
        try:
            return self._stdin.fileno()
        except (ValueError, AttributeError):
            return None

    @property
    def _stdout(self):
        if self._final_q:
            raise NotImplementedError
        return sys.stdout.buffer

    @property
    def _stdout_fd(self):
        try:
            return self._stdout.fileno()
        except (ValueError, AttributeError):
            return None