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_)