"""Utilities to get a password and/or the current user name.

getpass(prompt[, stream]) - Prompt for a password, with echo turned off.

getuser() - Get the user name from the environment or password database.

GetPassWarning - This UserWarning is issued when getpass() cannot prevent

                 echoing of the password contents while reading.

On Windows, the msvcrt module will be used.

On the Mac EasyDialogs.AskPassword is used, if available.

"""

# Authors: Piers Lauder (original)

#          Guido van Rossum (Windows support and cleanup)

#          Gregory P. Smith (tty support & GetPassWarning)

import os, sys, warnings

__all__ = ["getpass","getuser","GetPassWarning"]

class GetPassWarning(UserWarning): pass

def unix_getpass(prompt='Password: ', stream=None):

    """Prompt for a password, with echo turned off.

    Args:

      prompt: Written on stream to ask for the input.  Default: 'Password: '

      stream: A writable file object to display the prompt.  Defaults to

              the tty.  If no tty is available defaults to sys.stderr.

    Returns:

      The seKr3t input.

    Raises:

      EOFError: If our input tty or stdin was closed.

      GetPassWarning: When we were unable to turn echo off on the input.

    Always restores terminal settings before returning.

    """

    fd = None

    tty = None

    try:

        # Always try reading and writing directly on the tty first.

        fd = os.open('/dev/tty', os.O_RDWR|os.O_NOCTTY)

        tty = os.fdopen(fd, 'w+', 1)

        input = tty

        if not stream:

            stream = tty

    except EnvironmentError, e:

        # If that fails, see if stdin can be controlled.

        try:

            fd = sys.stdin.fileno()

        except:

            passwd = fallback_getpass(prompt, stream)

        input = sys.stdin

        if not stream:

            stream = sys.stderr

    if fd is not None:

        passwd = None

        try:

            old = termios.tcgetattr(fd)     # a copy to save

            new = old[:]

            new[3] &= ~termios.ECHO  # 3 == 'lflags'

            try:

                termios.tcsetattr(fd, termios.TCSADRAIN, new)

                passwd = _raw_input(prompt, stream, input=input)

            finally:

                termios.tcsetattr(fd, termios.TCSADRAIN, old)

        except termios.error, e:

            if passwd is not None:

                # _raw_input succeeded.  The final tcsetattr failed.  Reraise

                # instead of leaving the terminal in an unknown state.

                raise

            # We can't control the tty or stdin.  Give up and use normal IO.

            # fallback_getpass() raises an appropriate warning.

            del input, tty  # clean up unused file objects before blocking

            passwd = fallback_getpass(prompt, stream)

    stream.write('\n')

    return passwd

def win_getpass(prompt='Password: ', stream=None):

    """Prompt for password with echo off, using Windows getch()."""

    if sys.stdin is not sys.__stdin__:

        return fallback_getpass(prompt, stream)

    import msvcrt

    for c in prompt:

        msvcrt.putch(c)

    pw = ""

    while 1:

        c = msvcrt.getch()

        if c == '\r' or c == '\n':

            break

        if c == '\003':

            raise KeyboardInterrupt

        if c == '\b':

            pw = pw[:-1]

        else:

            pw = pw + c

    msvcrt.putch('\r')

    msvcrt.putch('\n')

    return pw

def fallback_getpass(prompt='Password: ', stream=None):

    warnings.warn("Can not control echo on the terminal.", GetPassWarning,

                  stacklevel=2)

    if not stream:

        stream = sys.stderr

    print >>stream, "Warning: Password input may be echoed."

    return _raw_input(prompt, stream)

def _raw_input(prompt="", stream=None, input=None):

    # A raw_input() replacement that doesn't save the string in the

    # GNU readline history.

    if not stream:

        stream = sys.stderr

    if not input:

        input = sys.stdin

    prompt = str(prompt)

    if prompt:

        stream.write(prompt)

        stream.flush()

    line = input.readline()

    if not line:

        raise EOFError

    if line[-1] == '\n':

        line = line[:-1]

    return line

def getuser():

    """Get the username from the environment or password database.

    First try various environment variables, then the password

    database.  This works on Windows as long as USERNAME is set.

    """

    import os

    for name in ('LOGNAME', 'USER', 'LNAME', 'USERNAME'):

        user = os.environ.get(name)

        if user:

            return user

    # If this fails, the exception will "explain" why

    import pwd

    return pwd.getpwuid(os.getuid())[0]

# Bind the name getpass to the appropriate function

try:

    import termios

    # it's possible there is an incompatible termios from the

    # McMillan Installer, make sure we have a UNIX-compatible termios

    termios.tcgetattr, termios.tcsetattr

except (ImportError, AttributeError):

    try:

        import msvcrt

    except ImportError:

        try:

            from EasyDialogs import AskPassword

        except ImportError:

            getpass = fallback_getpass

        else:

            getpass = AskPassword

    else:

        getpass = win_getpass

else:

    getpass = unix_getpass