# Copyright 2002, 2003 Ben Escoto
#
# This file is part of rdiff-backup.
#
# rdiff-backup is free software; you can redistribute it and/or modify
# 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.
#
# rdiff-backup 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 rdiff-backup; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
# USA

"""This module deal with users and groups

On each connection we may need to map unames and gnames to uids and
gids, and possibly vice-versa.  So maintain a separate dictionary for
this.

On the destination connection only, if necessary have a separate
dictionary of mappings, which specify how to map users/groups on one
connection to the users/groups on the other.  The UserMap and GroupMap
objects should only be used on the destination.

"""

import grp, pwd
import log, Globals

############ "Private" section - don't use outside user_group ###########

# This should be set to the user UserMap class object if using
# user-defined user mapping, and a Map class object otherwise.
UserMap = None

# This should be set to the group UserMap class object if using
# user-defined group mapping, and a Map class object otherwise.
GroupMap = None

# Used to cache by uid2uname and gid2gname below
uid2uname_dict = {}; gid2gname_dict = {}

uname2uid_dict = {}
def uname2uid(uname):
	"""Given uname, return uid or None if cannot find"""
	try: return uname2uid_dict[uname]
	except KeyError:
		try: uid = pwd.getpwnam(uname)[2]
		except KeyError: uid = None
		uname2uid_dict[uname] = uid
		return uid

gname2gid_dict = {}
def gname2gid(gname):
	"""Given gname, return gid or None if cannot find"""
	try: return gname2gid_dict[gname]
	except KeyError:
		try: gid = grp.getgrnam(gname)[2]
		except KeyError: gid = None
		gname2gid_dict[gname] = gid
		return gid


class Map:
	"""Used for mapping names and id on source side to dest side"""
	def __init__(self, is_user):
		"""Initialize, user is true for users, false for groups"""
		self.name2id = (is_user and uname2uid) or gname2gid

	def __call__(self, id, name = None):
		"""Return mapped id from id and, if available, name"""
		if not name: return id
		newid = self.name2id(name)
		if newid is None: return id
		else: return newid

	def map_acl(self, id, name = None):
		"""Like get_id, but use this for ACLs.  Return id or None

		Unlike ordinary user/group ownership, ACLs are not required
		and can be dropped.  If we cannot map the name over, return
		None.

		"""
		if not name: return id
		return self.name2id(name)
		

class DefinedMap(Map):
	"""Map names and ids on source side to appropriate ids on dest side

	Like map, but initialize with user-defined mapping string, which
	supersedes Map.

	"""
	def __init__(self, is_user, mapping_string):
		"""Initialize object with given mapping string

		The mapping_string should consist of a number of lines, each which
		should have the form "source_id_or_name:dest_id_or_name".  Do user
		mapping unless user is false, then do group.

		"""
		Map.__init__(self, is_user)
		self.name_mapping_dict = {}; self.id_mapping_dict = {}

		for line in mapping_string.split('\n'):
			line = line.strip()
			if not line: continue
			comps = line.split(':')
			if not len(comps) == 2:
				log.Log.FatalError("Error parsing mapping file, bad line: "
								   + line)
			old, new = comps

			try: self.id_mapping_dict[int(old)] = self.init_get_new_id(new)
			except ValueError:
				self.name_mapping_dict[old] = self.init_get_new_id(new)

	def init_get_new_id(self, id_or_name):
		"""Return id of id_or_name, failing if cannot.  Used in __init__"""
		try: return int(id_or_name)
		except ValueError:
			try: return self.name2id(id_or_name)
			except KeyError:
				log.Log.FatalError("Cannot get id for user or group name "
								   + id_or_name)

	def __call__(self, id, name = None):
		"""Return new id given old id and name"""
		newid = self.map_acl(id, name)
		if newid is None: return id
		else: return newid

	def map_acl(self, id, name = None):
		"""Return new id or None given old and name (used for ACLs)"""
		if name:
			try: return self.name_mapping_dict[name]
			except KeyError: pass
			newid = self.name2id(name)
			if newid is not None: return newid
		try: return self.id_mapping_dict[id]
		except KeyError: return None


class NumericalMap:
	"""Simple Map replacement that just keeps numerical uid or gid"""
	def __call__(self, id, name = None): return id
	def map_acl(self, id, name = None): return id


############ Public section - can use these outside user_group ###########


def uid2uname(uid):
	"""Given uid, return uname from passwd file, or None if cannot find"""
	try: return uid2uname_dict[uid]
	except KeyError:
		try: uname = pwd.getpwuid(uid)[0]
		except (KeyError, OverflowError), e: uname = None
		uid2uname_dict[uid] = uname
		return uname

def gid2gname(gid):
	"""Given gid, return group name from group file or None if cannot find"""
	try: return gid2gname_dict[gid]
	except KeyError:
		try: gname = grp.getgrgid(gid)[0]
		except (KeyError, OverflowError), e: gname = None
		gid2gname_dict[gid] = gname
		return gname


def init_user_mapping(mapping_string = None, numerical_ids = None):
	"""Initialize user mapping with given mapping string

	If numerical_ids is set, just keep the same uid.  If either
	argument is None, default to preserving uname where possible.

	"""
	global UserMap
	if numerical_ids: UserMap = NumericalMap()
	elif mapping_string: UserMap = DefinedMap(1, mapping_string)
	else: UserMap = Map(1)

def init_group_mapping(mapping_string = None, numerical_ids = None):
	"""Initialize group mapping with given mapping string

	If numerical_ids is set, just keep the same gid.  If either
	argument is None, default to preserving gname where possible.

	"""
	global GroupMap
	if numerical_ids: GroupMap = NumericalMap()
	elif mapping_string: GroupMap = DefinedMap(0, mapping_string)
	else: GroupMap = Map(0)


def map_rpath(rp):
	"""Return mapped (newuid, newgid) from rpath's initial info

	This is the main function exported by the user_group module.  Note
	that it is connection specific.

	"""
	uid, gid = rp.getuidgid()
	uname, gname = rp.getuname(), rp.getgname()
	return (UserMap(uid, uname), GroupMap(gid, gname))

def acl_user_map(uid, uname): return UserMap.map_acl(uid, uname)
def acl_group_map(gid, gname): return GroupMap.map_acl(gid, gname)
