from io import open

from os import environ

from os.path import isfile

from subprocess import PIPE, Popen

import sys

def _determineMounts():

	# The MSYS shell provides a Unix-like file system by translating paths on

	# the command line to Windows paths. Usually this is transparent, but not

	# for us since we call GCC without going through the shell.

	# Figure out the root directory of MSYS.

	proc = Popen(

		[ msysShell(), '-c', '"%s" -c \'import sys ; print sys.argv[1]\' /'

			% sys.executable.replace('\\', '\\\\') ],

		stdin = None,

		stdout = PIPE,

		stderr = PIPE,

		)

	stdoutdata, stderrdata = proc.communicate()

	if stderrdata or proc.returncode:

		if stderrdata:

			print('Error determining MSYS root:', stderrdata, file=sys.stderr)

		if proc.returncode:

			print('Exit code %d' % proc.returncode, file=sys.stderr)

		raise OSError('Error determining MSYS root')

	msysRoot = stdoutdata.strip()

	# Figure out all mount points of MSYS.

	mounts = {}

	fstab = msysRoot + '/etc/fstab'

	if isfile(fstab):

		try:

			with open(fstab, 'r', encoding='utf-8') as inp:

				for line in inp:

					line = line.strip()

					if line and not line.startswith('#'):

						nativePath, mountPoint = (

							path.rstrip('/') + '/' for path in line.split()[:2]

							)

						if nativePath != 'none':

							mounts[mountPoint] = nativePath

		except OSError as ex:

			print('Failed to read MSYS fstab:', ex, file=sys.stderr)

		except ValueError as ex:

			print('Failed to parse MSYS fstab:', ex, file=sys.stderr)

	mounts['/'] = msysRoot + '/'

	return mounts

def msysPathToNative(path):

	if path.startswith('/'):

		if len(path) == 2 or (len(path) > 2 and path[2] == '/'):

			# Support drive letters as top-level dirs.

			return '%s:/%s' % (path[1], path[3 : ])

		longestMatch = ''

		for mountPoint in msysMounts.keys():

			if path.startswith(mountPoint):

				if len(mountPoint) > len(longestMatch):

					longestMatch = mountPoint

		return msysMounts[longestMatch] + path[len(longestMatch) : ]

	else:

		return path

def msysActive():

	return environ.get('OSTYPE') == 'msys' or 'MSYSCON' in environ

def msysShell():

	return environ.get('SHELL') or 'sh.exe'

if msysActive():

	msysMounts = _determineMounts()

else:

	msysMounts = None

if __name__ == '__main__':

	print('MSYS mounts:', msysMounts)