# Copyright 2002 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

"""Deal with side effects from traversing trees"""

from __future__ import generators
import types
import Globals, rpath, log


class DSRPPermError(Exception):
	"""Exception used when a DSRPath can't get sufficient permissions"""
	pass

class DSRPath(rpath.RPath):
	"""Destructive Stepping RPath

	Sometimes when we traverse the directory tree, even when we just
	want to read files, we have to change things, like the permissions
	of a file or directory in order to read it, or the file's access
	times.  This class is like an RPath, but the permission and time
	modifications are delayed, so that they can be done at the very
	end when they won't be disturbed later.

	Here are the new class variables:
	delay_perms - true iff future perm changes should be delayed
	newperms - holds the perm values while they are delayed
	delay_atime - true iff some atime change are being delayed
	newatime - holds the new atime
	delay_mtime - true if some mtime change is being delayed
	newmtime - holds the new mtime

	"""
	def __init__(self, source, conn_or_rp, base = 0, index = ()):
		"""Initialize DSRP

		Source should be true iff the DSRPath is taken from the
		"source" partition and thus settings like
		Globals.change_source_perms should be paid attention to.

		If args is [rpath], return the dsrpath equivalent of rpath,
		otherwise use the same arguments as the RPath initializer.

		"""
		if base == 0:
			assert isinstance(conn_or_rp, rpath.RPath)
			rpath.RPath.__init__(self, conn_or_rp.conn,
								 conn_or_rp.base, conn_or_rp.index)
			self.path = conn_or_rp.path # conn_or_rp may be quoted
		else: rpath.RPath.__init__(self, conn_or_rp, base, index)

		if source != "bypass":
			# "bypass" val is used when unpackaging over connection
			assert source is None or source is 1
			self.source = source
			self.set_delays(source)
			self.set_init_perms(source)

	def set_delays(self, source):
		"""Delay writing permissions and times where appropriate"""
		if not source or Globals.change_source_perms:
			self.delay_perms, self.newperms = 1, None
		else: self.delay_perms = None

		if Globals.preserve_atime:
			self.delay_atime = 1
			# Now get atime right away if possible
			if self.data.has_key('atime'): self.newatime = self.data['atime']
			else: self.newatime = None
		else: self.delay_atime = None
		
		if source:
			self.delay_mtime = None # we'll never change mtime of source file
		else:
			self.delay_mtime = 1
			# Save mtime now for a dir, because it might inadvertantly change
			if self.isdir(): self.newmtime = self.data['mtime']
			else: self.newmtime = None

	def set_init_perms(self, source):
		"""If necessary, change permissions to ensure access"""
		if self.isreg() and not self.readable():
			if (source and Globals.change_source_perms or
				not source and Globals.change_mirror_perms):
				self.chmod_bypass(0400)
		elif self.isdir():
			if source and Globals.change_source_perms:
				if not self.readable() or not self.executable():
					self.chmod_bypass(0500)
			elif not source and Globals.change_mirror_perms:
				if not self.hasfullperms(): self.chmod_bypass(0700)

	def warn(self, err):
		log.Log("Received error '%s' when dealing with file %s, skipping..."
				% (err, self.path), 1)
		raise DSRPPermError(self.path)

	def __getstate__(self):
		"""Return picklable state.  See RPath __getstate__."""
		assert self.conn is Globals.local_connection # Can't pickle a conn
		return self.getstatedict()

	def getstatedict(self):
		"""Return dictionary containing the attributes we can save"""
		pickle_dict = {}
		for attrib in ['index', 'data', 'delay_perms', 'newperms',
					   'delay_atime', 'newatime',
					   'delay_mtime', 'newmtime',
					   'path', 'base', 'source']:
			if self.__dict__.has_key(attrib):
				pickle_dict[attrib] = self.__dict__[attrib]
		return pickle_dict

	def __setstate__(self, pickle_dict):
		"""Set state from object produced by getstate"""
		self.conn = Globals.local_connection
		for attrib in pickle_dict.keys():
			self.__dict__[attrib] = pickle_dict[attrib]

	def chmod(self, permissions):
		"""Change permissions, delaying if self.perms_delayed is set"""
		if self.delay_perms: self.newperms = self.data['perms'] = permissions
		else: rpath.RPath.chmod(self, permissions)

	def getperms(self):
		"""Return dsrp's intended permissions"""
		if self.delay_perms and self.newperms is not None:
			return self.newperms
		else: return self.data['perms']

	def chmod_bypass(self, permissions):
		"""Change permissions without updating the data dictionary"""
		self.delay_perms = 1
		if self.newperms is None: self.newperms = self.getperms()
		log.Log("DSRP: Perm bypass %s to %o" % (self.path, permissions), 8)
		self.conn.os.chmod(self.path, permissions)

	def settime(self, accesstime, modtime):
		"""Change times, delaying if self.times_delayed is set"""
		if self.delay_atime: self.newatime = self.data['atime'] = accesstime
		if self.delay_mtime: self.newmtime = self.data['mtime'] = modtime

		if not self.delay_atime or not self.delay_mtime:
			rpath.RPath.settime(self, accesstime, modtime)
		
	def setmtime(self, modtime):
		"""Change mtime, delaying if self.times_delayed is set"""
		if self.delay_mtime: self.newmtime = self.data['mtime'] = modtime
		else: rpath.RPath.setmtime(self, modtime)

	def getmtime(self):
		"""Return dsrp's intended modification time"""
		if self.delay_mtime and self.newmtime is not None:
			return self.newmtime
		else: return self.data['mtime']

	def getatime(self):
		"""Return dsrp's intended access time"""
		if self.delay_atime and self.newatime is not None:
			return self.newatime
		else: return self.data['atime']

	def write_changes(self):
		"""Write saved up permission/time changes"""
		if not self.lstat(): return # File has been deleted in meantime

		if self.delay_perms and self.newperms is not None:
			log.Log("Finalizing permissions of dsrp %s to %s" %
					(self.path, self.newperms), 8)
			rpath.RPath.chmod(self, self.newperms)

		do_atime = self.delay_atime and self.newatime is not None
		do_mtime = self.delay_mtime and self.newmtime is not None
		if do_atime and do_mtime:
			rpath.RPath.settime(self, self.newatime, self.newmtime)
		elif do_atime and not do_mtime:
			rpath.RPath.settime(self, self.newatime, self.getmtime())
		elif not do_atime and do_mtime:
			rpath.RPath.setmtime(self, self.newmtime)

	def newpath(self, newpath, index = ()):
		"""Return similar DSRPath but with new path"""
		return self.__class__(self.source, self.conn, newpath, index)

	def append(self, ext):
		"""Return similar DSRPath with new extension"""
		return self.__class__(self.source, self.conn, self.base,
							  self.index + (ext,))

	def new_index(self, index):
		"""Return similar DSRPath with new index"""
		return self.__class__(self.source, self.conn, self.base, index)