"""Utilities and extensions for use with `argparse`."""

import os

import argparse

def directory(arg):

"""

An argument type (for use with the ``type=`` argument to

`argparse.ArgumentParser.add_argument` which determines if the argument is

an existing directory (and returns the absolute path).

"""

if not isinstance(arg, str) and os.path.isdir(arg):

raise argparse.ArgumentTypeError(

"{0} is not a directory or does not exist (the directory must "

"be created first)".format(arg))

return os.path.abspath(arg)

def readable_directory(arg):

"""

An argument type (for use with the ``type=`` argument to

`argparse.ArgumentParser.add_argument` which determines if the argument is

a directory that exists and is readable (and returns the absolute path).

"""

arg = directory(arg)

if not os.access(arg, os.R_OK):

raise argparse.ArgumentTypeError(

"{0} exists but is not readable with its current "

"permissions".format(arg))

return arg

def writeable_directory(arg):

"""

An argument type (for use with the ``type=`` argument to

`argparse.ArgumentParser.add_argument` which determines if the argument is

a directory that exists and is writeable (and returns the absolute path).

"""

arg = directory(arg)

if not os.access(arg, os.W_OK):

raise argparse.ArgumentTypeError(

"{0} exists but is not writeable with its current "

"permissions".format(arg))

return arg