# Copyright (C) 2005, Giovanni Bajo

# Based on previous work under copyright (c) 2002 McMillan Enterprises, Inc.

#

# This program is free software; you can redistribute it and/or

# modify it under the terms of the GNU General Public License

# as published by the Free Software Foundation; either version 2

# of the License, or (at your option) any later version.

#

# This program is distributed in the hope that it will be useful,

# but WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

# GNU General Public License for more details.

#

# You should have received a copy of the GNU General Public License

# along with this program; if not, write to the Free Software

# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA

_orig_open = open

class _BkFile:

	def __init__(self, file, mode, bufsize):

		import os

		self.__filename = file

		self.__backup = file + '~'

		try:

			os.unlink(self.__backup)

		except os.error:

			pass

		try:

			os.rename(file, self.__backup)

		except os.error:

			self.__backup = None

		self.__file = _orig_open(file, mode, bufsize)

		self.closed = self.__file.closed

		self.fileno = self.__file.fileno

		self.flush = self.__file.flush

		self.isatty = self.__file.isatty

		self.mode = self.__file.mode

		self.name = self.__file.name

		self.read = self.__file.read

		self.readinto = self.__file.readinto

		self.readline = self.__file.readline

		self.readlines = self.__file.readlines

		self.seek = self.__file.seek

		self.softspace = self.__file.softspace

		self.tell = self.__file.tell

		self.truncate = self.__file.truncate

		self.write = self.__file.write

		self.writelines = self.__file.writelines

	def close(self):

		self.__file.close()

		if self.__backup is None:

			return

		try:

			from cmp import do_cmp

		except:

			from filecmp import cmp

			do_cmp = cmp

		# don't use cmp.cmp because of NFS bugs :-( and

		# anyway, the stat mtime values differ so do_cmp will

		# most likely be called anyway

		if do_cmp(self.__backup, self.__filename):

			import os

			os.unlink(self.__filename)

			os.rename(self.__backup, self.__filename)

def open(file, mode = 'r', bufsize = -1):

	if 'w' not in mode:

		return _orig_open(file, mode, bufsize)

	return _BkFile(file, mode, bufsize)