import fcntl
import os
import select
import sys
import termios
from contextlib import contextmanager


@contextmanager
def setup_term(*args, **kwargs):
    fd = sys.stdin.fileno()
    oldterm = termios.tcgetattr(fd)
    newattr = termios.tcgetattr(fd)
    newattr[3] = newattr[3] & ~termios.ICANON & ~termios.ECHO
    termios.tcsetattr(fd, termios.TCSANOW, newattr)
    oldflags = fcntl.fcntl(fd, fcntl.F_GETFL)
    fcntl.fcntl(fd, fcntl.F_SETFL, oldflags | os.O_NONBLOCK)
    try:
        yield
    finally:
        # restore terminal settings
        termios.tcsetattr(fd, termios.TCSAFLUSH, oldterm)
        fcntl.fcntl(fd, fcntl.F_SETFL, oldflags)


def getch(timeout):
    # sys.stdin.read is blocking, use select instead
    # NOTE: this will not work on windows as select only accepts sockets, not all file descriptors
    # TODO: use python selectors module?
    o, _, _ = select.select([sys.stdin], [], [], timeout)
    if o != []:
        assert len(o) == 1
        return o[0].read(1)
    return None