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

getpass(prompt) - prompt for a password, with echo turned off
getuser() - get the user name from the environment or password database

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)
"""

import sys

def unix_getpass(prompt='Password: '):
	"""Prompt for a password, with echo turned off.

	Restore terminal settings at end.
	"""

	try:
		fd = sys.stdin.fileno()
	except:
		return default_getpass(prompt)

	getpass = default_getpass
	old = termios.tcgetattr(fd)	# a copy to save
	new = old[:]

	new[3] = new[3] & ~TERMIOS.ECHO	# 3 == 'lflags'
	try:
		termios.tcsetattr(fd, TERMIOS.TCSADRAIN, new)
		passwd = _raw_input(prompt)
	finally:
		termios.tcsetattr(fd, TERMIOS.TCSADRAIN, old)

	sys.stdout.write('\n')
	return passwd


def win_getpass(prompt='Password: '):
	"""Prompt for password with echo off, using Windows getch()."""
	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 default_getpass(prompt='Password: '):
	print "Warning: Problem with getpass. Passwords may be echoed."
	return _raw_input(prompt)


def _raw_input(prompt=""):
	# A raw_input() replacement that doesn't save the string in the
	# GNU readline history.
	import sys
	prompt = str(prompt)
	if prompt:
		sys.stdout.write(prompt)
	line = sys.stdin.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, TERMIOS
except ImportError:
	try:
		import msvcrt
	except ImportError:
		try:
			from EasyDialogs import AskPassword
		except ImportError:
			getpass = default_getpass
		else:
			getpass = AskPassword
	else:
		getpass = win_getpass
else:
	getpass = unix_getpass