import os

import sys

__all__ = ('isatty',)

MYPY = False

if MYPY:

from typing import Optional

def isatty(stream=None):

stream = stream or sys.stdout

try:

return stream.isatty()

except Exception:

return False

def env_true(var_name: str, alt: 'Optional[bool]' = None) -> 'Optional[bool]':

env = os.getenv(var_name, None)

if env:

return env.upper() in {'1', 'TRUE'}

else:

return alt

def env_bool(value: 'Optional[bool]', env_name: str, env_default: 'Optional[bool]') -> 'Optional[bool]':

if value is None:

return env_true(env_name, env_default)

else:

return value

def activate_win_color() -> bool: # pragma: no cover

"""

Activate ANSI support on windows consoles.

As of Windows 10, the windows conolse got some support for ANSI escape

sequences. Unfortunately it has to be enabled first using `SetConsoleMode`.

See: https://docs.microsoft.com/en-us/windows/console/console-virtual-terminal-sequences

Code snippet source: https://bugs.python.org/msg291732

"""

import ctypes

import msvcrt

import os

from ctypes import wintypes

def _check_bool(result, func, args):

if not result:

raise ctypes.WinError(ctypes.get_last_error())

return args

ERROR_INVALID_PARAMETER = 0x0057

ENABLE_VIRTUAL_TERMINAL_PROCESSING = 0x0004

LPDWORD = ctypes.POINTER(wintypes.DWORD)

kernel32 = ctypes.WinDLL('kernel32', use_last_error=True)

kernel32.GetConsoleMode.errcheck = _check_bool

kernel32.GetConsoleMode.argtypes = (wintypes.HANDLE, LPDWORD)

kernel32.SetConsoleMode.errcheck = _check_bool

kernel32.SetConsoleMode.argtypes = (wintypes.HANDLE, wintypes.DWORD)

def _set_conout_mode(new_mode, mask=0xFFFFFFFF):

# don't assume StandardOutput is a console.

# open CONOUT$ instead

fdout = os.open('CONOUT$', os.O_RDWR)

try:

hout = msvcrt.get_osfhandle(fdout)

old_mode = wintypes.DWORD()

kernel32.GetConsoleMode(hout, ctypes.byref(old_mode))

mode = (new_mode & mask) | (old_mode.value & ~mask)

kernel32.SetConsoleMode(hout, mode)

return old_mode.value

finally:

os.close(fdout)

mode = mask = ENABLE_VIRTUAL_TERMINAL_PROCESSING

try:

_set_conout_mode(mode, mask)

except WindowsError as e:

if e.winerror == ERROR_INVALID_PARAMETER:

return False

raise

return True

def use_highlight(highlight: 'Optional[bool]' = None, file_=None) -> bool:

highlight = env_bool(highlight, 'PY_DEVTOOLS_HIGHLIGHT', None)

if highlight is not None:

return highlight

if sys.platform == 'win32': # pragma: no cover

return isatty(file_) and activate_win_color()

return isatty(file_)