mumble-django/pyweb/mumble/models.py

# -*- coding: utf-8 -*-

"""
 *  Copyright © 2009-2010, Michael "Svedrin" Ziegler <diese-addy@funzt-halt.net>
 *
 *  Mumble-Django 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 package 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.
"""

import socket, Ice, re
from sys	import stderr
from urllib	import urlopen
from StringIO	import StringIO
from PIL	import Image

from django.utils.translation	import ugettext_noop, ugettext_lazy as _
from django.contrib.auth.models import User
from django.db			import models
from django.db.models		import signals
from django.conf		import settings

from mumble.mmobjects		import mmChannel, mmPlayer
from mumble.mctl		import MumbleCtlBase


def mk_config_property( field, doc="", get_coerce=None, get_none=None, set_coerce=unicode, set_none='' ):
	""" Create a property for the given config field. """
	
	def get_field( self ):
		if self.id is not None:
			val = self.getConf( field );
			if val is None or val == '':
				return get_none
			if callable(get_coerce):
				return get_coerce( val )
			return val
		return None
	
	def set_field( self, value ):
		if value is None:
			self.setConf( field, set_none )
		elif callable(set_coerce):
			self.setConf( field, set_coerce(value) )
		else:
			self.setConf( field, value )
	
	return property( get_field, set_field, doc=doc )

def mk_config_bool_property( field, doc="" ):
	return mk_config_property( field, doc=doc,
		get_coerce = lambda value: value == "true",
		set_coerce = lambda value: str(value).lower()
		);


class MumbleServer( models.Model ):
	""" Represents a Murmur server installation. """
	
	dbus    = models.CharField( _('DBus or ICE base'), max_length=200, unique=True, default=settings.DEFAULT_CONN, help_text=_(
			"Examples: 'net.sourceforge.mumble.murmur' for DBus or 'Meta:tcp -h 127.0.0.1 -p 6502' for Ice.") );
	secret  = models.CharField( _('Ice Secret'),       max_length=200, blank=True );
	
	class Meta:
		verbose_name        = _('Mumble Server');
		verbose_name_plural = _('Mumble Servers');
	
	def __init__( self, *args, **kwargs ):
		models.Model.__init__( self, *args, **kwargs );
		self._ctl  = None;
		self._conf = None;
		self._version = None;
	
	def __unicode__( self ):
		return self.dbus;
	
	# Ctl instantiation
	def getCtl( self ):
		""" Instantiate and return a MumbleCtl object for this server.
		
		    Only one instance will be created, and reused on subsequent calls.
		"""
		if not self._ctl:
			self._ctl = MumbleCtlBase.newInstance( self.dbus, settings.SLICE, self.secret );
		return self._ctl;
	
	ctl = property( getCtl, doc="Get a Control object for this server. The ctl is cached for later reuse." );
	
	def isMethodDbus(self):
		""" Return true if this instance uses DBus. """
		rd = re.compile( r'^(\w+\.)*\w+$' );
		return bool(rd.match(self.dbus))
	
	method_dbus = property( isMethodDbus )
	method_ice  = property( lambda self: not self.isMethodDbus(), doc="Return true if this instance uses Ice." )
	
	def getDefaultConf( self, field=None ):
		""" Get a field from the default conf dictionary, or None if the field isn't set. """
		if self._conf is None:
			self._conf = self.ctl.getDefaultConf()
		if field is None:
			return self._conf
		if field in self._conf:
			return self._conf[field]
		return None
	
	def isOnline( self ):
		""" Return true if this server process is running. """
		possibleexceptions = []
		try:
			from Ice import ConnectionRefusedException
		except ImportError, err:
			if self.method_ice:
				print >> stderr, err
				return None
		else:
			possibleexceptions.append( ConnectionRefusedException )
		try:
			from dbus import DBusException
		except ImportError, err:
			if self.method_dbus:
				print >> stderr, err
				return None
		else:
			possibleexceptions.append( DBusException )
		
		try:
			self.ctl
		except tuple(possibleexceptions), err:
			print >> stderr, err
			return False
		except (EnvironmentError, RuntimeError), err:
			print >> stderr, err
			return None
		else:
			return True
	
	online = property( isOnline )
	defaultconf = property( getDefaultConf, doc="The default config dictionary." )
	
	def getVersion( self ):
		""" Return the version of Murmur. """
		if self._version is None:
			self._version = self.ctl.getVersion()
		return self._version
	
	version = property( getVersion )
	
	prettyversion = property( lambda self: '.'.join( map( str, self.version[:3] ) ),
		doc="Pretty-Printed version" );


class Mumble( models.Model ):
	""" Represents a Murmur server instance.
	
	    All configurable settings are represented by a field in this model. To change the
	    settings, just update the appropriate field and call the save() method.
	
	    To set up a new server instance, instanciate this Model. The first field you should
	    define is the "dbus" field, which tells the connector subsystem how to connect to
	    the Murmurd master process. Set this to the appropriate DBus service name or the
	    Ice proxy string.
	
	    When an instance of this model is deleted, the according server instance will be
	    deleted as well.
	"""
	
	server  = models.ForeignKey(   MumbleServer, verbose_name=_("Mumble Server") );
	name    = models.CharField(    _('Server Name'),            max_length=200 );
	srvid   = models.IntegerField( _('Server ID'),              editable=False );
	addr    = models.CharField(    _('Server Address'),         max_length=200, blank=True, help_text=_(
			"Hostname or IP address to bind to. You should use a hostname here, because it will appear on the "
			"global server list.") );
	port    = models.IntegerField( _('Server Port'),            blank=True, null=True, help_text=_(
			"Port number to bind to. Leave empty to auto assign one.") );
	display = models.CharField(    _('Server Display Address'), max_length=200, blank=True, help_text=_(
			"This field is only relevant if you are located behind a NAT, and names the Hostname or IP address "
			"to use in the Channel Viewer and for the global server list registration. If not given, the addr "
			"and port fields are used. If display and bind ports are equal, you can omit it here.") );
	
	supw    = property( lambda self: '',
			lambda self, value: ( value and self.ctl.setSuperUserPassword( self.srvid, value ) ) or None,
			doc=_('Superuser Password')
			)
	
	url     = mk_config_property( "registerurl",		ugettext_noop("Website URL") )
	motd    = mk_config_property( "welcometext",		ugettext_noop("Welcome Message") )
	passwd  = mk_config_property( "password",		ugettext_noop("Server Password") )
	users   = mk_config_property( "users",			ugettext_noop("Max. Users"),		get_coerce=int )
	bwidth  = mk_config_property( "bandwidth",		ugettext_noop("Bandwidth [Bps]"),	get_coerce=int )
	sslcrt  = mk_config_property( "certificate",		ugettext_noop("SSL Certificate") )
	sslkey  = mk_config_property( "key",			ugettext_noop("SSL Key") )
	player  = mk_config_property( "username",		ugettext_noop("Player name regex") )
	channel = mk_config_property( "channelname",		ugettext_noop("Channel name regex") )
	defchan = mk_config_property( "defaultchannel", 	ugettext_noop("Default channel"),	get_coerce=int )
	timeout = mk_config_property( "timeout",		ugettext_noop("Timeout"),		get_coerce=int )
	
	obfsc   = mk_config_bool_property( "obfuscate",         ugettext_noop("IP Obfuscation") )
	certreq = mk_config_bool_property( "certrequired",      ugettext_noop("Require Certificate") )
	textlen = mk_config_bool_property( "textmessagelength", ugettext_noop("Maximum length of text messages") )
	html    = mk_config_bool_property( "allowhtml",         ugettext_noop("Allow HTML to be used in messages") )
	bonjour = mk_config_bool_property( "bonjour",           ugettext_noop("Publish this server via Bonjour") )
	autoboot= mk_config_bool_property( "boot",              ugettext_noop("Boot Server when Murmur starts") )
	
	def getBooted( self ):
		if self.id is not None:
			if self.server.online:
				return self.ctl.isBooted( self.srvid )
			else:
				return None
		else:
			return False
	
	def setBooted( self, value ):
		if value != self.getBooted():
			if value:
				self.ctl.start( self.srvid );
			else:
				self.ctl.stop( self.srvid );
	
	booted  = property( getBooted, setBooted, doc=ugettext_noop("Boot Server") )
	online  = property( getBooted, setBooted, doc=ugettext_noop("Boot Server") )
	
	class Meta:
		unique_together     = ( ( 'server', 'srvid' ), );
		verbose_name        = _('Server instance');
		verbose_name_plural = _('Server instances');
	
	def __unicode__( self ):
		if not self.id:
			return u'Murmur "%s" (NOT YET CREATED)' % self.name;
		return u'Murmur "%s" (%d)' % ( self.name, self.srvid );
	
	def save( self, dontConfigureMurmur=False ):
		""" Save the options configured in this model instance not only to Django's database,
		    but to Murmur as well.
		"""
		if dontConfigureMurmur:
			return models.Model.save( self );
		
		if self.id is None:
			self.srvid = self.ctl.newServer();
		
		self.ctl.setConf( self.srvid, 'registername', self.name );
		
		if self.addr and self.addr != '0.0.0.0':
			self.ctl.setConf( self.srvid, 'host', socket.gethostbyname(self.addr) );
		else:
			self.ctl.setConf( self.srvid, 'host', '' );
		
		if self.port and self.port != settings.MUMBLE_DEFAULT_PORT + self.srvid - 1:
			self.ctl.setConf( self.srvid, 'port', str(self.port) );
		else:
			self.ctl.setConf( self.srvid, 'port', '' );
		
		if self.netloc:
			self.ctl.setConf( self.srvid, 'registerhostname', self.netloc );
		else:
			self.ctl.setConf( self.srvid, 'registerhostname', '' );
		
		return models.Model.save( self );
	
	
	def __init__( self, *args, **kwargs ):
		models.Model.__init__( self, *args, **kwargs );
		self._channels = None;
		self._rootchan = None;
	
	
	users_regged = property( lambda self: self.mumbleuser_set.count(),           doc="Number of registered users." );
	users_online = property( lambda self: len(self.ctl.getPlayers(self.srvid)),  doc="Number of online users." );
	channel_cnt  = property( lambda self: len(self.ctl.getChannels(self.srvid)), doc="Number of channels." );
	is_public    = property( lambda self: not self.passwd,
			doc="False if a password is needed to join this server." );
	
	is_server  = True;
	is_channel = False;
	is_player  = False;
	
	ctl = property( lambda self: self.server.ctl );
	
	def getConf( self, field ):
		return self.ctl.getConf( self.srvid, field )
	
	def setConf( self, field, value ):
		return self.ctl.setConf( self.srvid, field, value )
	
	def configureFromMurmur( self ):
		conf = self.ctl.getAllConf( self.srvid );
		
		if "registername" not in conf or not conf["registername"]:
			self.name = "noname";
		else:
			self.name = conf["registername"];
		
		if "registerhostname" in conf and conf["registerhostname"]:
			if ':' in conf["registerhostname"]:
				regname, regport = conf["registerhostname"].split(':')
				regport = int(regport)
			else:
				regname = conf["registerhostname"]
				regport = None
		else:
			regname = None
			regport = None
		
		if "host" in conf and conf["host"]:
			addr = conf["host"]
		else:
			addr = None
		
		if "port" in conf and conf["port"]:
			self.port = int(conf["port"])
		else:
			self.port = None
		
		if regname and addr:
			if regport == self.port:
				if socket.gethostbyname(regname) == socket.gethostbyname(addr):
					self.display = ''
					self.addr = regname
				else:
					self.display = regname
					self.addr = addr
			else:
				self.display = conf["registerhostname"]
				self.addr = addr
		elif regname and not addr:
			self.display = regname
			self.addr    = ''
		elif addr and not regname:
			self.display = ''
			self.addr    = addr
		else:
			self.display = ''
			self.addr    = ''
		
		self.save( dontConfigureMurmur=True );
	
	
	def readUsersFromMurmur( self, verbose=0 ):
		if not self.booted:
			raise SystemError( "This murmur instance is not currently running, can't sync." );
		
		players = self.ctl.getRegisteredPlayers(self.srvid);
		known_ids = [rec["mumbleid"]
			for rec in MumbleUser.objects.filter( server=self ).values( "mumbleid" )
			]
		
		for idx in players:
			playerdata = players[idx];
			
			if playerdata.userid == 0: # Skip SuperUsers
				continue;
			if verbose > 1:
				print "Checking Player with id %d." % playerdata.userid;
			
			if playerdata.userid not in known_ids:
				if verbose:
					print 'Found new Player "%s".' % playerdata.name;
				
				playerinstance = MumbleUser(
					mumbleid = playerdata.userid,
					name     = playerdata.name,
					password = '',
					server   = self,
					owner    = None
					);
			
			else:
				if verbose > 1:
					print "Player '%s' is already known." % playerdata.name;
				playerinstance = MumbleUser.objects.get( server=self, mumbleid=playerdata.userid );
				playerinstance.name = playerdata.name;
			
			playerinstance.save( dontConfigureMurmur=True );

	
	def isUserAdmin( self, user ):
		""" Determine if the given user is an admin on this server. """
		if user.is_authenticated():
			if user.is_superuser:
				return True;
			try:
				return self.mumbleuser_set.get( owner=user ).getAdmin();
			except MumbleUser.DoesNotExist:
				return False;
		return False;
	
	
	# Deletion handler
	def deleteServer( self ):
		""" Delete this server instance from Murmur. """
		self.ctl.deleteServer(self.srvid)
	
	@staticmethod
	def pre_delete_listener( **kwargs ):
		kwargs['instance'].deleteServer();
	
	
	# Channel list
	def getChannels( self ):
		""" Query the channels from Murmur and create a tree structure.
		
		    Again, this will only be done for the first call to this function. Subsequent
		    calls will simply return the list created last time.
		"""
		if self._channels is None:
			self._channels = {};
			chanlist = self.ctl.getChannels(self.srvid).values();
			links = {};
			
			# sometimes, ICE seems to return the Channel list in a weird order.
			# itercount prevents infinite loops.
			itercount = 0;
			maxiter   = len(chanlist) * 3;
			while len(chanlist) and itercount < maxiter:
				itercount += 1;
				for theChan in chanlist:
					# Channels - Fields: 0 = ID, 1 = Name, 2 = Parent-ID, 3 = Links
					if( theChan.parent == -1 ):
						# No parent
						self._channels[theChan.id] = mmChannel( self, theChan );
					elif theChan.parent in self.channels:
						# parent already known
						self._channels[theChan.id] = mmChannel( self, theChan, self.channels[theChan.parent] );
					else:
						continue;
					
					chanlist.remove( theChan );
					
					self._channels[theChan.id].serverId = self.id;
					
					# process links - if the linked channels are known, link; else save their ids to link later
					for linked in theChan.links:
						if linked in self._channels:
							self._channels[theChan.id].linked.append( self._channels[linked] );
						else:
							if linked not in links:
								links[linked] = list();
							links[linked].append( self._channels[theChan.id] );
					
					# check if earlier round trips saved channel ids to be linked to the current channel
					if theChan.id in links:
						for targetChan in links[theChan.id]:
							targetChan.linked.append( self._channels[theChan.id] );
			
			self._channels[0].name = self.name;
			
			self.players = {};
			for thePlayer in self.ctl.getPlayers(self.srvid).values():
				# Players - Fields: 0 = UserID, 6 = ChannelID
				self.players[ thePlayer.session ] = mmPlayer( self, thePlayer, self._channels[ thePlayer.channel ] );
			
			self._channels[0].sort();
		
		return self._channels;
	
	channels = property( getChannels,                       doc="A convenience wrapper for getChannels()."    );
	rootchan = property( lambda self: self.channels[0],     doc="A convenience wrapper for getChannels()[0]." );
	
	def getNetloc( self ):
		""" Return the address from the Display field (if any), or the server address.
		    Users from outside a NAT will need to use the Display address to connect
		    to this server instance.
		"""
		if self.display:
			if ":" in self.display:
				return self.display;
			else:
				daddr = self.display;
		else:
			daddr = self.addr;
		
		if self.port and self.port != settings.MUMBLE_DEFAULT_PORT:
			return "%s:%d" % (daddr, self.port);
		else:
			return daddr;
	
	netloc = property( getNetloc );
	
	def getURL( self, forUser = None ):
		""" Create an URL of the form mumble://username@host:port/ for this server. """
		if not self.netloc:
			return None
		from urlparse import urlunsplit
		versionstr = "version=%s" % self.prettyversion;
		if forUser is not None:
			netloc = "%s@%s" % ( forUser.name, self.netloc );
			return urlunsplit(( "mumble", netloc, "", versionstr, "" ))
		else:
			return urlunsplit(( "mumble", self.netloc, "", versionstr, "" ))
	
	connecturl = property( getURL );
	
	version = property( lambda self: self.server.version, doc="The version of Murmur." );
	prettyversion = property( lambda self: self.server.prettyversion );
	
	def asDict( self ):
		return { 'name':   self.name,
			 'id':     self.id,
			 'root':   self.rootchan.asDict()
			};
	
	def asMvXml( self ):
		""" Return an XML tree for this server suitable for MumbleViewer-ng. """
		from xml.etree.cElementTree import Element
		root = Element("root")
		self.rootchan.asMvXml(root)
		return root
	
	def asMvJson( self ):
		""" Return a Dict for this server suitable for MumbleViewer-ng. """
		return self.rootchan.asMvJson()
	
	# "server" field protection
	def __setattr__( self, name, value ):
		if name == 'server':
			if self.id is not None and self.server != value:
				raise AttributeError( _( "This field must not be updated once the record has been saved." ) );
		
		models.Model.__setattr__( self, name, value );
	
	def kickUser( self, sessionid, reason="" ):
		return self.ctl.kickUser( self.srvid, sessionid, reason );
	
	def banUser( self, sessionid, reason="" ):
		return self.ctl.addBanForSession( self.srvid, sessionid, reason=reason );



def mk_registration_property( field, doc="" ):
	""" Create a property for the given registration field. """
	
	def get_field( self ):
		if field in self.registration:
			return self.registration[field];
		else:
			return None;
	
	return property( get_field, doc=doc )


class MumbleUser( models.Model ):
	""" Represents a User account in Murmur.
	
	    To change an account, simply set the according field in this model and call the save()
	    method to update the account in Murmur and in Django's database. Note that, once saved
	    for the first time, the server field must not be changed. Attempting to do this will
	    result in an AttributeError. To move an account to a new server, recreate it on the
	    new server and delete the old model.
	
	    When you delete an instance of this model, the according user account will be deleted
	    in Murmur as well, after revoking the user's admin privileges.
	"""
	
	mumbleid = models.IntegerField(         _('Mumble player_id'),             editable = False, default = -1 );
	name     = models.CharField(            _('User name and Login'),          max_length = 200 );
	password = models.CharField(            _('Login password'),               max_length = 200, blank=True );
	server   = models.ForeignKey(   Mumble, verbose_name=_('Server instance'), related_name="mumbleuser_set" );
	owner    = models.ForeignKey(   User,   verbose_name=_('Account owner'),   related_name="mumbleuser_set", null=True, blank=True );
	
	comment = mk_registration_property( "comment", doc=ugettext_noop("The user's comment.") );
	hash    = mk_registration_property( "hash",    doc=ugettext_noop("The user's hash.")    );
	
	gravatar256 = property( lambda self: self.gravatarUrl( size=256 ) )
	gravatar128 = property( lambda self: self.gravatarUrl( size=128 ) )
	gravatar64  = property( lambda self: self.gravatarUrl( size=64  ) )
	gravatar    = property( lambda self: self.gravatarUrl() )
	
	class Meta:
		unique_together     = ( ( 'server', 'owner' ), ( 'server', 'mumbleid' ) );
		verbose_name        = _( 'User account'  );
		verbose_name_plural = _( 'User accounts' );
	
	is_server  = False;
	is_channel = False;
	is_player  = True;
	
	def __unicode__( self ):
		return _("Mumble user %(mu)s on %(srv)s owned by Django user %(du)s") % {
			'mu':  self.name,
			'srv': self.server,
			'du':  self.owner
			};
	
	def save( self, dontConfigureMurmur=False ):
		""" Save the settings in this model to Murmur. """
		if dontConfigureMurmur:
			return models.Model.save( self );
		
		ctl = self.server.ctl;
		
		if self.owner:
			email = self.owner.email;
		else:
			email = settings.DEFAULT_FROM_EMAIL;
		
		if self.id is None:
			# This is a new user record, so Murmur doesn't know about it yet
			if len( ctl.getRegisteredPlayers( self.server.srvid, self.name ) ) > 0:
				raise ValueError( _( "Another player already registered that name." ) );
			if not self.password:
				raise ValueError( _( "Cannot register player without a password!" ) );
			
			self.mumbleid = ctl.registerPlayer( self.server.srvid, self.name, email, self.password );
		
		# Update user's registration
		elif self.password:
			ctl.setRegistration(
				self.server.srvid,
				self.mumbleid,
				self.name,
				email,
				self.password
				);
		
		# Don't save the users' passwords, we don't need them anyway
		self.password = '';
		
		# If enabled (and possible), set Gravatar as default Avatar
		if settings.USE_GRAVATAR and self.gravatar:
			self.setTextureFromUrl( self.gravatar )
		
		return models.Model.save( self );
	
	def __init__( self, *args, **kwargs ):
		models.Model.__init__( self, *args, **kwargs );
		self._registration = None;
	
	# Admin handlers
	def getAdmin( self ):
		""" Get ACL of root Channel, get the admin group and see if this user is in it. """
		if self.mumbleid == -1:
			return False;
		else:
			return self.server.rootchan.acl.group_has_member( "admin", self.mumbleid );
	
	def setAdmin( self, value ):
		""" Set or revoke this user's membership in the admin group on the root channel. """
		if self.mumbleid == -1:
			return False;
		if value:
			self.server.rootchan.acl.group_add_member( "admin", self.mumbleid );
		else:
			self.server.rootchan.acl.group_remove_member( "admin", self.mumbleid );
		self.server.rootchan.acl.save();
		return value;
	
	aclAdmin = property( getAdmin, setAdmin, doc=ugettext_noop('Admin on root channel') );
	
	
	# Registration fetching
	def getRegistration( self ):
		""" Retrieve a user's registration from Murmur as a dict. """
		if not self._registration:
			self._registration = self.server.ctl.getRegistration( self.server.srvid, self.mumbleid );
		return self._registration;
	
	registration = property( getRegistration );
	
	# Texture handlers
	def getTexture( self ):
		""" Get the user texture as a PIL Image. """
		return self.server.ctl.getTexture(self.server.srvid, self.mumbleid);
	
	def setTexture( self, image ):
		""" Install the given image as the user's texture. """
		self.server.ctl.setTexture(self.server.srvid, self.mumbleid, image)
	
	def setTextureFromUrl( self, url, transparency=None ):
		""" Retrieve the image at the given URL and set it as my texture. """
		img = Image.open( StringIO( urlopen( url ).read() ) )
		self.setTexture( img )
	
	texture = property( getTexture, setTexture,
		doc="Get the texture as a PIL Image or set the Image as the texture."
		);
	
	def hasTexture( self ):
		""" Check if this user has a texture set. """
		try:
			self.getTexture();
		except ValueError:
			return False;
		else:
			return True;
	
	def gravatarUrl( self, size=80 ):
		""" Get a Gravatar URL for my owner's email adress (if any), or using the User's cert hash.
		    The size parameter is optional, and defaults to 80 pixels (the default used by Gravatar
		    if you omit this parameter in the URL).
		"""
		if self.owner and self.owner.email:
			from hashlib import md5
			return settings.GRAVATAR_URL % { 'hash': md5(self.owner.email).hexdigest(), 'size': size }
		elif self.hash:
			return settings.GRAVATAR_URL % { 'hash': self.hash, 'size': size }
		return None
	
	def getTextureUrl( self ):
		""" Get a URL under which the texture can be retrieved. """
		from views				import showTexture
		from django.core.urlresolvers		import reverse
		return reverse( showTexture, kwargs={ 'server': self.server.id, 'userid': self.id } );
	
	textureUrl = property( getTextureUrl );
	
	
	# Deletion handler
	@staticmethod
	def pre_delete_listener( **kwargs ):
		kwargs['instance'].unregister();
	
	def unregister( self ):
		""" Delete this user account from Murmur. """
		if self.getAdmin():
			self.setAdmin( False );
		self.server.ctl.unregisterPlayer(self.server.srvid, self.mumbleid)
	
	
	# "server" field protection
	def __setattr__( self, name, value ):
		if name == 'server':
			if self.id is not None and self.server != value:
				raise AttributeError( _( "This field must not be updated once the record has been saved." ) );
		
		models.Model.__setattr__( self, name, value );




signals.pre_delete.connect( Mumble.pre_delete_listener,     sender=Mumble     );
signals.pre_delete.connect( MumbleUser.pre_delete_listener, sender=MumbleUser );