PyLink/classes.py

"""
classes.py - Base classes for PyLink IRC Services.

This module contains the base classes used by PyLink, including threaded IRC
connections and objects used to represent IRC servers, users, and channels.

Here be dragons.
"""

import threading
from random import randint
import time
import socket
import threading
import ssl
import hashlib
from copy import deepcopy
import inspect

from log import *
import world
import utils
import structures

### Exceptions

class ProtocolError(Exception):
    pass

class NotAuthenticatedError(Exception):
    """
    Exception raised by checkAuthenticated() when a user fails authentication
    requirements.
    """
    pass

### Internal classes (users, servers, channels)

class Irc():
    """Base IRC object for PyLink."""

    def __init__(self, netname, proto, conf):
        """
        Initializes an IRC object. This takes 3 variables: the network name
        (a string), the name of the protocol module to use for this connection,
        and a configuration object.
        """
        self.loghandlers = []
        self.name = netname
        self.conf = conf
        self.serverdata = conf['servers'][netname]
        self.sid = self.serverdata["sid"]
        self.botdata = conf['bot']
        self.protoname = proto.__name__
        self.proto = proto.Class(self)
        self.pingfreq = self.serverdata.get('pingfreq') or 30
        self.pingtimeout = self.pingfreq * 2

        self.connected = threading.Event()
        self.aborted = threading.Event()

        self.initVars()

        if world.testing:
            # HACK: Don't thread if we're running tests.
            self.connect()
        else:
            self.connection_thread = threading.Thread(target=self.connect,
                                                      name="Listener for %s" %
                                                      self.name)
            self.connection_thread.start()
        self.pingTimer = None

    def logSetup(self):
        """
        Initializes any channel loggers defined for the current network.
        """
        try:
            channels = self.conf['logging']['channels'][self.name]
        except KeyError:  # Not set up; just ignore.
            return

        log.debug('(%s) Setting up channel logging to channels %r', self.name,
                  channels)

        if not self.loghandlers:
            # Only create handlers if they haven't already been set up.

            for channel, chandata in channels.items():
                # Fetch the log level for this channel block.
                level = None
                if chandata is not None:
                    level = chandata.get('loglevel')

                handler = PyLinkChannelLogger(self, channel, level=level)
                self.loghandlers.append(handler)
                log.addHandler(handler)

    def initVars(self):
        """
        (Re)sets an IRC object to its default state. This should be called when
        an IRC object is first created, and on every reconnection to a network.
        """
        self.sid = self.serverdata["sid"]
        self.botdata = self.conf['bot']
        self.pingfreq = self.serverdata.get('pingfreq') or 180
        self.pingtimeout = self.pingfreq * 2

        self.connected.clear()
        self.aborted.clear()
        self.pseudoclient = None
        self.lastping = time.time()

        # Internal variable to set the place the last command was called (in PM
        # or in a channel), used by fantasy command support.
        self.called_by = None

        # Intialize the server, channel, and user indexes to be populated by
        # our protocol module. For the server index, we can add ourselves right
        # now.
        self.servers = {self.sid: IrcServer(None, self.serverdata['hostname'],
                        internal=True, desc=self.serverdata.get('serverdesc')
                        or self.botdata['serverdesc'])}
        self.users = {}
        self.channels = structures.KeyedDefaultdict(IrcChannel)

        # This sets the list of supported channel and user modes: the default
        # RFC1459 modes are implied. Named modes are used here to make
        # protocol-independent code easier to write, as mode chars vary by
        # IRCd.
        # Protocol modules should add to and/or replace this with what their
        # protocol supports. This can be a hardcoded list or something
        # negotiated on connect, depending on the nature of their protocol.
        self.cmodes = {'op': 'o', 'secret': 's', 'private': 'p',
                       'noextmsg': 'n', 'moderated': 'm', 'inviteonly': 'i',
                       'topiclock': 't', 'limit': 'l', 'ban': 'b',
                       'voice': 'v', 'key': 'k',
                       # This fills in the type of mode each mode character is.
                       # A-type modes are list modes (i.e. bans, ban exceptions, etc.),
                       # B-type modes require an argument to both set and unset,
                       #   but there can only be one value at a time
                       #   (i.e. cmode +k).
                       # C-type modes require an argument to set but not to unset
                       #   (one sets "+l limit" and # "-l"),
                       # and D-type modes take no arguments at all.
                       '*A': 'b',
                       '*B': 'k',
                       '*C': 'l',
                       '*D': 'imnpstr'}
        self.umodes = {'invisible': 'i', 'snomask': 's', 'wallops': 'w',
                       'oper': 'o',
                       '*A': '', '*B': '', '*C': 's', '*D': 'iow'}

        # This max nick length starts off as the config value, but may be
        # overwritten later by the protocol module if such information is
        # received. Note that only some IRCds (InspIRCd) give us nick length
        # during link, so it is still required that the config value be set!
        self.maxnicklen = self.serverdata['maxnicklen']

        # Defines a list of supported prefix modes.
        self.prefixmodes = {'o': '@', 'v': '+'}

        # Defines the uplink SID (to be filled in by protocol module).
        self.uplink = None
        self.start_ts = int(time.time())

        # Set up channel logging for the network
        self.logSetup()

    def connect(self):
        """
        Runs the connect loop for the IRC object. This is usually called by
        __init__ in a separate thread to allow multiple concurrent connections.
        """
        while True:
            self.initVars()
            ip = self.serverdata["ip"]
            port = self.serverdata["port"]
            checks_ok = True
            try:
                # Set the socket type (IPv6 or IPv4).
                stype = socket.AF_INET6 if self.serverdata.get("ipv6") else socket.AF_INET

                # Creat the socket.
                self.socket = socket.socket(stype)
                self.socket.setblocking(0)

                # Set the connection timeouts. Initial connection timeout is a
                # lot smaller than the timeout after we've connected; this is
                # intentional.
                self.socket.settimeout(self.pingfreq)

                # Enable SSL if set to do so. This requires a valid keyfile and
                # certfile to be present.
                self.ssl = self.serverdata.get('ssl')
                if self.ssl:
                    log.info('(%s) Attempting SSL for this connection...', self.name)
                    certfile = self.serverdata.get('ssl_certfile')
                    keyfile = self.serverdata.get('ssl_keyfile')
                    if certfile and keyfile:
                        try:
                            self.socket = ssl.wrap_socket(self.socket,
                                                          certfile=certfile,
                                                          keyfile=keyfile)
                        except OSError:
                             log.exception('(%s) Caught OSError trying to '
                                           'initialize the SSL connection; '
                                           'are "ssl_certfile" and '
                                           '"ssl_keyfile" set correctly?',
                                           self.name)
                             checks_ok = False
                    else:  # SSL was misconfigured, abort.
                        log.error('(%s) SSL certfile/keyfile was not set '
                                  'correctly, aborting... ', self.name)
                        checks_ok = False

                log.info("Connecting to network %r on %s:%s", self.name, ip, port)
                self.socket.connect((ip, port))
                self.socket.settimeout(self.pingtimeout)

                # If SSL was enabled, optionally verify the certificate
                # fingerprint for some added security. I don't bother to check
                # the entire certificate for validity, since most IRC networks
                # self-sign their certificates anyways.
                if self.ssl and checks_ok:
                    peercert = self.socket.getpeercert(binary_form=True)

                    # Hash type is configurable using the ssl_fingerprint_type
                    # value, and defaults to sha256.
                    hashtype = self.serverdata.get('ssl_fingerprint_type', 'sha256').lower()

                    try:
                        hashfunc = getattr(hashlib, hashtype)
                    except AttributeError:
                        log.error('(%s) Unsupported SSL certificate fingerprint type %r given, disconnecting...',
                                  self.name, hashtype)
                        checks_ok = False
                    else:
                        fp = hashfunc(peercert).hexdigest()
                        expected_fp = self.serverdata.get('ssl_fingerprint')

                        if expected_fp and checks_ok:
                            if fp != expected_fp:
                                # SSL Fingerprint doesn't match; break.
                                log.error('(%s) Uplink\'s SSL certificate '
                                          'fingerprint (%s) does not match the '
                                          'one configured: expected %r, got %r; '
                                          'disconnecting...', self.name, hashtype,
                                          expected_fp, fp)
                                checks_ok = False
                            else:
                                log.info('(%s) Uplink SSL certificate fingerprint '
                                         '(%s) verified: %r', self.name, hashtype,
                                         fp)
                        else:
                            log.info('(%s) Uplink\'s SSL certificate fingerprint (%s) '
                                     'is %r. You can enhance the security of your '
                                     'link by specifying this in a "ssl_fingerprint"'
                                     ' option in your server block.', self.name,
                                     hashtype, fp)

                if checks_ok:
                    # All our checks passed, get the protocol module to connect
                    # and run the listen loop.
                    self.proto.connect()
                    self.spawnMain()
                    log.info('(%s) Starting ping schedulers....', self.name)
                    self.schedulePing()
                    log.info('(%s) Server ready; listening for data.', self.name)
                    self.run()
                else:  # Configuration error :(
                    log.error('(%s) A configuration error was encountered '
                              'trying to set up this connection. Please check'
                              ' your configuration file and try again.',
                              self.name)
            except (socket.error, ProtocolError, ConnectionError) as e:
                # self.run() or the protocol module it called raised an
                # exception, meaning we've disconnected!
                log.error('(%s) Disconnected from IRC: %s: %s',
                          self.name, type(e).__name__, str(e))

            if not self.aborted.is_set():
                # Only start a disconnection process if one doesn't already
                # exist.
                self.disconnect()

            # Internal hook signifying that a network has disconnected.
            self.callHooks([None, 'PYLINK_DISCONNECT', {}])

            # If autoconnect is enabled, loop back to the start. Otherwise,
            # return and stop.
            autoconnect = self.serverdata.get('autoconnect')
            log.debug('(%s) Autoconnect delay set to %s seconds.', self.name, autoconnect)
            if autoconnect is not None and autoconnect >= 1:
                log.info('(%s) Going to auto-reconnect in %s seconds.', self.name, autoconnect)
                time.sleep(autoconnect)
            else:
                log.info('(%s) Stopping connect loop (autoconnect value %r is < 1).', self.name, autoconnect)
                return

    def disconnect(self):
        """Handle disconnects from the remote server."""

        log.debug('(%s) _disconnect: Clearing self.connected state.', self.name)
        self.connected.clear()

        log.debug('(%s) _disconnect: Setting self.aborted to True.', self.name)
        self.aborted.set()

        log.debug('(%s) disconnect: Clearing state via initVars().', self.name)
        self.initVars()

        log.debug('(%s) Removing channel logging handlers due to disconnect.', self.name)
        while self.loghandlers:
            log.removeHandler(self.loghandlers.pop())

        try:
            log.debug('(%s) _disconnect: Shutting down socket.', self.name)
            self.socket.shutdown(socket.SHUT_RDWR)
        except:  # Socket timed out during creation; ignore
            pass

        self.socket.close()

        if self.pingTimer:
            log.debug('(%s) Canceling pingTimer at %s due to disconnect() call', self.name, time.time())
            self.pingTimer.cancel()

    def run(self):
        """Main IRC loop which listens for messages."""
        # Some magic below cause this to work, though anything that's
        # not encoded in UTF-8 doesn't work very well.
        buf = b""
        data = b""
        while not self.aborted.is_set():

            try:
                data = self.socket.recv(2048)
            except OSError:
                # Suppress socket read warnings from lingering recv() calls if
                # we've been told to shutdown.
                if self.aborted.is_set():
                    return
                raise

            buf += data
            if not data:
                log.error('(%s) No data received, disconnecting!', self.name)
                return
            elif (time.time() - self.lastping) > self.pingtimeout:
                log.error('(%s) Connection timed out.', self.name)
                return
            while b'\n' in buf:
                line, buf = buf.split(b'\n', 1)
                line = line.strip(b'\r')
                # FIXME: respect other encodings?
                line = line.decode("utf-8", "replace")
                self.runline(line)

    def runline(self, line):
        """Sends a command to the protocol module."""
        log.debug("(%s) <- %s", self.name, line)
        try:
            hook_args = self.proto.handle_events(line)
        except Exception:
            log.exception('(%s) Caught error in handle_events, disconnecting!', self.name)
            log.error('(%s) The offending line was: <- %s', self.name, line)
            self.aborted.set()
            return
        # Only call our hooks if there's data to process. Handlers that support
        # hooks will return a dict of parsed arguments, which can be passed on
        # to plugins and the like. For example, the JOIN handler will return
        # something like: {'channel': '#whatever', 'users': ['UID1', 'UID2',
        # 'UID3']}, etc.
        if hook_args is not None:
            self.callHooks(hook_args)

        return hook_args

    def callHooks(self, hook_args):
        """Calls a hook function with the given hook args."""
        numeric, command, parsed_args = hook_args
        # Always make sure TS is sent.
        if 'ts' not in parsed_args:
            parsed_args['ts'] = int(time.time())
        hook_cmd = command
        hook_map = self.proto.hook_map

        # If the hook name is present in the protocol module's hook_map, then we
        # should set the hook name to the name that points to instead.
        # For example, plugins will read SETHOST as CHGHOST, EOS (end of sync)
        # as ENDBURST, etc.
        if command in hook_map:
            hook_cmd = hook_map[command]

        # However, individual handlers can also return a 'parse_as' key to send
        # their payload to a different hook. An example of this is "/join 0"
        # being interpreted as leaving all channels (PART).
        hook_cmd = parsed_args.get('parse_as') or hook_cmd

        log.debug('(%s) Raw hook data: [%r, %r, %r] received from %s handler '
                  '(calling hook %s)', self.name, numeric, hook_cmd, parsed_args,
                  command, hook_cmd)

        # Iterate over registered hook functions, catching errors accordingly.
        for hook_func in world.hooks[hook_cmd]:
            try:
                log.debug('(%s) Calling hook function %s from plugin "%s"', self.name,
                          hook_func, hook_func.__module__)
                hook_func(self, numeric, command, parsed_args)
            except Exception:
                # We don't want plugins to crash our servers...
                log.exception('(%s) Unhandled exception caught in hook %r from plugin "%s"',
                              self.name, hook_func, hook_func.__module__)
                log.error('(%s) The offending hook data was: %s', self.name,
                          hook_args)
                continue

    def send(self, data):
        """Sends raw text to the uplink server."""
        # Safeguard against newlines in input!! Otherwise, each line gets
        # treated as a separate command, which is particularly nasty.
        data = data.replace('\n', ' ')
        data = data.encode("utf-8") + b"\n"
        stripped_data = data.decode("utf-8").strip("\n")
        log.debug("(%s) -> %s", self.name, stripped_data)
        try:
            self.socket.send(data)
        except (OSError, AttributeError):
            log.debug("(%s) Dropping message %r; network isn't connected!", self.name, stripped_data)

    def schedulePing(self):
        """Schedules periodic pings in a loop."""
        self.proto.ping()

        self.pingTimer = threading.Timer(self.pingfreq, self.schedulePing)
        self.pingTimer.daemon = True
        self.pingTimer.name = 'Ping timer loop for %s' % self.name
        self.pingTimer.start()

        log.debug('(%s) Ping scheduled at %s', self.name, time.time())

    def spawnMain(self):
        """Spawns the main PyLink client."""
        nick = self.botdata.get('nick') or 'PyLink'
        ident = self.botdata.get('ident') or 'pylink'
        host = self.serverdata["hostname"]
        log.info('(%s) Connected! Spawning main client %s.', self.name, nick)
        olduserobj = self.pseudoclient
        self.pseudoclient = self.proto.spawnClient(nick, ident, host,
                                                   modes={("+o", None)},
                                                   manipulatable=True,
                                                   opertype="PyLink Service")
        for chan in self.serverdata['channels']:
            self.proto.join(self.pseudoclient.uid, chan)
        # PyLink internal hook called when spawnMain is called and the
        # contents of Irc().pseudoclient change.
        self.callHooks([self.sid, 'PYLINK_SPAWNMAIN', {'olduser': olduserobj}])

    def __repr__(self):
        return "<classes.Irc object for %r>" % self.name

    ### General utility functions
    def callCommand(self, source, text):
        """
        Calls a PyLink bot command. source is the caller's UID, and text is the
        full, unparsed text of the message.
        """
        cmd_args = text.strip().split(' ')
        cmd = cmd_args[0].lower()
        cmd_args = cmd_args[1:]
        if cmd not in world.commands:
            self.msg(self.called_by or source, 'Error: Unknown command %r.' % cmd)
            log.info('(%s) Received unknown command %r from %s', self.name, cmd, self.getHostmask(source))
            return
        log.info('(%s) Calling command %r for %s', self.name, cmd, self.getHostmask(source))
        for func in world.commands[cmd]:
            try:
                func(self, source, cmd_args)
            except NotAuthenticatedError:
                self.msg(self.called_by or source, 'Error: You are not authorized to perform this operation.')
            except Exception as e:
                log.exception('Unhandled exception caught in command %r', cmd)
                self.msg(self.called_by or source, 'Uncaught exception in command %r: %s: %s' % (cmd, type(e).__name__, str(e)))

    def msg(self, target, text, notice=False, source=None):
        """Handy function to send messages/notices to clients. Source
        is optional, and defaults to the main PyLink client if not specified."""
        source = source or self.pseudoclient.uid
        if notice:
            self.proto.notice(source, target, text)
            cmd = 'PYLINK_SELF_NOTICE'
        else:
            self.proto.message(source, target, text)
            cmd = 'PYLINK_SELF_PRIVMSG'
        self.callHooks([source, cmd, {'target': target, 'text': text}])

    def reply(self, text, notice=False, source=None):
        """Replies to the last caller in the right context (channel or PM)."""
        self.msg(self.called_by, text, notice=notice, source=source)

    def toLower(self, text):
        """Returns a lowercase representation of text based on the IRC object's
        casemapping (rfc1459 or ascii)."""
        if self.proto.casemapping == 'rfc1459':
            text = text.replace('{', '[')
            text = text.replace('}', ']')
            text = text.replace('|', '\\')
            text = text.replace('~', '^')
        return text.lower()

    def parseModes(self, target, args):
        """Parses a modestring list into a list of (mode, argument) tuples.
        ['+mitl-o', '3', 'person'] => [('+m', None), ('+i', None), ('+t', None), ('+l', '3'), ('-o', 'person')]
        """
        # http://www.irc.org/tech_docs/005.html
        # A = Mode that adds or removes a nick or address to a list. Always has a parameter.
        # B = Mode that changes a setting and always has a parameter.
        # C = Mode that changes a setting and only has a parameter when set.
        # D = Mode that changes a setting and never has a parameter.
        assert args, 'No valid modes were supplied!'
        usermodes = not utils.isChannel(target)
        prefix = ''
        modestring = args[0]
        args = args[1:]
        if usermodes:
            log.debug('(%s) Using self.umodes for this query: %s', self.name, self.umodes)

            if target not in self.users:
                log.warning('(%s) Possible desync! Mode target %s is not in the users index.', self.name, target)
                return []  # Return an empty mode list

            supported_modes = self.umodes
            oldmodes = self.users[target].modes
        else:
            log.debug('(%s) Using self.cmodes for this query: %s', self.name, self.cmodes)

            if target not in self.channels:
                log.warning('(%s) Possible desync! Mode target %s is not in the channels index.', self.name, target)
                return []

            supported_modes = self.cmodes
            oldmodes = self.channels[target].modes
        res = []
        for mode in modestring:
            if mode in '+-':
                prefix = mode
            else:
                if not prefix:
                    prefix = '+'
                arg = None
                log.debug('Current mode: %s%s; args left: %s', prefix, mode, args)
                try:
                    if mode in (supported_modes['*A'] + supported_modes['*B']):
                        # Must have parameter.
                        log.debug('Mode %s: This mode must have parameter.', mode)
                        arg = args.pop(0)
                        if prefix == '-' and mode in supported_modes['*B'] and arg == '*':
                            # Charybdis allows unsetting +k without actually
                            # knowing the key by faking the argument when unsetting
                            # as a single "*".
                            # We'd need to know the real argument of +k for us to
                            # be able to unset the mode.
                            oldargs = [m[1] for m in oldmodes if m[0] == mode]
                            if oldargs:
                                # Set the arg to the old one on the channel.
                                arg = oldargs[0]
                                log.debug("Mode %s: coersing argument of '*' to %r.", mode, arg)
                    elif mode in self.prefixmodes and not usermodes:
                        # We're setting a prefix mode on someone (e.g. +o user1)
                        log.debug('Mode %s: This mode is a prefix mode.', mode)
                        arg = args.pop(0)
                        # Convert nicks to UIDs implicitly; most IRCds will want
                        # this already.
                        arg = self.nickToUid(arg) or arg
                        if arg not in self.users:  # Target doesn't exist, skip it.
                            log.debug('(%s) Skipping setting mode "%s %s"; the '
                                      'target doesn\'t seem to exist!', self.name,
                                      mode, arg)
                            continue
                    elif prefix == '+' and mode in supported_modes['*C']:
                        # Only has parameter when setting.
                        log.debug('Mode %s: Only has parameter when setting.', mode)
                        arg = args.pop(0)
                except IndexError:
                    log.warning('(%s/%s) Error while parsing mode %r: mode requires an '
                                'argument but none was found. (modestring: %r)',
                                self.name, target, mode, modestring)
                    continue  # Skip this mode; don't error out completely.
                res.append((prefix + mode, arg))
        return res

    def applyModes(self, target, changedmodes):
        """Takes a list of parsed IRC modes, and applies them on the given target.

        The target can be either a channel or a user; this is handled automatically."""
        usermodes = not utils.isChannel(target)
        log.debug('(%s) Using usermodes for this query? %s', self.name, usermodes)

        try:
            if usermodes:
                old_modelist = self.users[target].modes
                supported_modes = self.umodes
            else:
                old_modelist = self.channels[target].modes
                supported_modes = self.cmodes
        except KeyError:
            log.warning('(%s) Possible desync? Mode target %s is unknown.', self.name, target)
            return

        modelist = set(old_modelist)
        log.debug('(%s) Applying modes %r on %s (initial modelist: %s)', self.name, changedmodes, target, modelist)
        for mode in changedmodes:
            # Chop off the +/- part that parseModes gives; it's meaningless for a mode list.
            try:
                real_mode = (mode[0][1], mode[1])
            except IndexError:
                real_mode = mode

            if not usermodes:
                # We only handle +qaohv for now. Iterate over every supported mode:
                # if the IRCd supports this mode and it is the one being set, add/remove
                # the person from the corresponding prefix mode list (e.g. c.prefixmodes['op']
                # for ops).
                for pmode, pmodelist in self.channels[target].prefixmodes.items():
                    if pmode in self.cmodes and real_mode[0] == self.cmodes[pmode]:
                        log.debug('(%s) Initial prefixmodes list: %s', self.name, pmodelist)
                        if mode[0][0] == '+':
                            pmodelist.add(mode[1])
                        else:
                            pmodelist.discard(mode[1])

                        log.debug('(%s) Final prefixmodes list: %s', self.name, pmodelist)

                if real_mode[0] in self.prefixmodes:
                    # Don't add prefix modes to IrcChannel.modes; they belong in the
                    # prefixmodes mapping handled above.
                    log.debug('(%s) Not adding mode %s to IrcChannel.modes because '
                              'it\'s a prefix mode.', self.name, str(mode))
                    continue

            if mode[0][0] == '+':
                # We're adding a mode
                existing = [m for m in modelist if m[0] == real_mode[0] and m[1] != real_mode[1]]
                if existing and real_mode[1] and real_mode[0] not in self.cmodes['*A']:
                    # The mode we're setting takes a parameter, but is not a list mode (like +beI).
                    # Therefore, only one version of it can exist at a time, and we must remove
                    # any old modepairs using the same letter. Otherwise, we'll get duplicates when,
                    # for example, someone sets mode "+l 30" on a channel already set "+l 25".
                    log.debug('(%s) Old modes for mode %r exist on %s, removing them: %s',
                              self.name, real_mode, target, str(existing))
                    [modelist.discard(oldmode) for oldmode in existing]
                modelist.add(real_mode)
                log.debug('(%s) Adding mode %r on %s', self.name, real_mode, target)
            else:
                log.debug('(%s) Removing mode %r on %s', self.name, real_mode, target)
                # We're removing a mode
                if real_mode[1] is None:
                    # We're removing a mode that only takes arguments when setting.
                    # Remove all mode entries that use the same letter as the one
                    # we're unsetting.
                    for oldmode in modelist.copy():
                        if oldmode[0] == real_mode[0]:
                            modelist.discard(oldmode)
                else:
                    # Swap the - for a + and then remove it from the list.
                    modelist.discard(real_mode)
        log.debug('(%s) Final modelist: %s', self.name, modelist)
        if usermodes:
            self.users[target].modes = modelist
        else:
            self.channels[target].modes = modelist

    @staticmethod
    def _flip(mode):
        """Flips a mode character."""
        # Make it a list first, strings don't support item assignment
        mode = list(mode)
        if mode[0] == '-':  # Query is something like "-n"
            mode[0] = '+'  # Change it to "+n"
        elif mode[0] == '+':
            mode[0] = '-'
        else:  # No prefix given, assume +
            mode.insert(0, '-')
        return ''.join(mode)

    def reverseModes(self, target, modes, oldobj=None):
        """Reverses/Inverts the mode string or mode list given.

        Optionally, an oldobj argument can be given to look at an earlier state of
        a channel/user object, e.g. for checking the op status of a mode setter
        before their modes are processed and added to the channel state.

        This function allows both mode strings or mode lists. Example uses:
            "+mi-lk test => "-mi+lk test"
            "mi-k test => "-mi+k test"
            [('+m', None), ('+r', None), ('+l', '3'), ('-o', 'person')
             => {('-m', None), ('-r', None), ('-l', None), ('+o', 'person')})
            {('s', None), ('+o', 'whoever') => {('-s', None), ('-o', 'whoever')})
        """
        origtype = type(modes)
        # If the query is a string, we have to parse it first.
        if origtype == str:
            modes = self.parseModes(target, modes.split(" "))
        # Get the current mode list first.
        if utils.isChannel(target):
            c = oldobj or self.channels[target]
            oldmodes = c.modes.copy()
            possible_modes = self.cmodes.copy()
            # For channels, this also includes the list of prefix modes.
            possible_modes['*A'] += ''.join(self.prefixmodes)
            for name, userlist in c.prefixmodes.items():
                try:
                    oldmodes.update([(self.cmodes[name], u) for u in userlist])
                except KeyError:
                    continue
        else:
            oldmodes = self.users[target].modes
            possible_modes = self.umodes
        newmodes = []
        log.debug('(%s) reverseModes: old/current mode list for %s is: %s', self.name,
                   target, oldmodes)
        for char, arg in modes:
            # Mode types:
            # A = Mode that adds or removes a nick or address to a list. Always has a parameter.
            # B = Mode that changes a setting and always has a parameter.
            # C = Mode that changes a setting and only has a parameter when set.
            # D = Mode that changes a setting and never has a parameter.
            mchar = char[-1]
            if mchar in possible_modes['*B'] + possible_modes['*C']:
                # We need to find the current mode list, so we can reset arguments
                # for modes that have arguments. For example, setting +l 30 on a channel
                # that had +l 50 set should give "+l 30", not "-l".
                oldarg = [m for m in oldmodes if m[0] == mchar]
                if oldarg:  # Old mode argument for this mode existed, use that.
                    oldarg = oldarg[0]
                    mpair = ('+%s' % oldarg[0], oldarg[1])
                else:  # Not found, flip the mode then.
                    # Mode takes no arguments when unsetting.
                    if mchar in possible_modes['*C'] and char[0] != '-':
                        arg = None
                    mpair = (self._flip(char), arg)
            else:
                mpair = (self._flip(char), arg)
            if char[0] != '-' and (mchar, arg) in oldmodes:
                # Mode is already set.
                log.debug("(%s) reverseModes: skipping reversing '%s %s' with %s since we're "
                          "setting a mode that's already set.", self.name, char, arg, mpair)
                continue
            elif char[0] == '-' and (mchar, arg) not in oldmodes and mchar in possible_modes['*A']:
                # We're unsetting a prefixmode that was never set - don't set it in response!
                # Charybdis lacks verification for this server-side.
                log.debug("(%s) reverseModes: skipping reversing '%s %s' with %s since it "
                          "wasn't previously set.", self.name, char, arg, mpair)
                continue
            newmodes.append(mpair)

        log.debug('(%s) reverseModes: new modes: %s', self.name, newmodes)
        if origtype == str:
            # If the original query is a string, send it back as a string.
            return self.joinModes(newmodes)
        else:
            return set(newmodes)

    @staticmethod
    def joinModes(modes):
        """Takes a list of (mode, arg) tuples in parseModes() format, and
        joins them into a string.

        See testJoinModes in tests/test_utils.py for some examples."""
        prefix = '+'  # Assume we're adding modes unless told otherwise
        modelist = ''
        args = []
        for modepair in modes:
            mode, arg = modepair
            assert len(mode) in (1, 2), "Incorrect length of a mode (received %r)" % mode
            try:
                # If the mode has a prefix, use that.
                curr_prefix, mode = mode
            except ValueError:
                # If not, the current prefix stays the same; move on to the next
                # modepair.
                pass
            else:
                # If the prefix of this mode isn't the same as the last one, add
                # the prefix to the modestring. This prevents '+nt-lk' from turning
                # into '+n+t-l-k' or '+ntlk'.
                if prefix != curr_prefix:
                    modelist += curr_prefix
                    prefix = curr_prefix
            modelist += mode
            if arg is not None:
                args.append(arg)
        if not modelist.startswith(('+', '-')):
            # Our starting mode didn't have a prefix with it. Assume '+'.
            modelist = '+' + modelist
        if args:
            # Add the args if there are any.
            modelist += ' %s' % ' '.join(args)
        return modelist

    def version(self):
        """
        Returns a detailed version string including the PyLink daemon version,
        the protocol module in use, and the server hostname.
        """
        fullversion = 'PyLink-%s. %s :[protocol:%s]' % (world.version, self.serverdata['hostname'], self.protoname)
        return fullversion

    ### State checking functions
    def nickToUid(self, nick):
        """Looks up the UID of a user with the given nick, if one is present."""
        nick = self.toLower(nick)
        for k, v in self.users.copy().items():
            if self.toLower(v.nick) == nick:
                return k

    def isInternalClient(self, numeric):
        """
        Checks whether the given numeric is a PyLink Client,
        returning the SID of the server it's on if so.
        """
        for sid in self.servers:
            if self.servers[sid].internal and numeric in self.servers[sid].users:
                return sid
        return False

    def isInternalServer(self, sid):
        """Returns whether the given SID is an internal PyLink server."""
        return (sid in self.servers and self.servers[sid].internal)

    def getServer(self, numeric):
        """Finds the SID of the server a user is on."""
        for server in self.servers:
            if numeric in self.servers[server].users:
                return server

    def isManipulatableClient(self, uid):
        """
        Returns whether the given user is marked as an internal, manipulatable
        client. Usually, automatically spawned services clients should have this
        set True to prevent interactions with opers (like mode changes) from
        causing desyncs.
        """
        return self.isInternalClient(uid) and self.users[uid].manipulatable

    def getHostmask(self, user, realhost=False, ip=False):
        """
        Returns the hostmask of the given user, if present. If the realhost option
        is given, return the real host of the user instead of the displayed host.
        If the ip option is given, return the IP address of the user (this overrides
        realhost)."""
        userobj = self.users.get(user)

        try:
            nick = userobj.nick
        except AttributeError:
            nick = '<unknown-nick>'

        try:
            ident = userobj.ident
        except AttributeError:
            ident = '<unknown-ident>'

        try:
            if ip:
                host = userobj.ip
            elif realhost:
                host = userobj.realhost
            else:
                host = userobj.host
        except AttributeError:
            host = '<unknown-host>'

        return '%s!%s@%s' % (nick, ident, host)

    def isOper(self, uid, allowAuthed=True, allowOper=True):
        """
        Returns whether the given user has operator status on PyLink. This can be achieved
        by either identifying to PyLink as admin (if allowAuthed is True),
        or having user mode +o set (if allowOper is True). At least one of
        allowAuthed or allowOper must be True for this to give any meaningful
        results.
        """
        if uid in self.users:
            if allowOper and ("o", None) in self.users[uid].modes:
                return True
            elif allowAuthed and self.users[uid].identified:
                return True
        return False

    def checkAuthenticated(self, uid, allowAuthed=True, allowOper=True):
        """
        Checks whether the given user has operator status on PyLink, raising
        NotAuthenticatedError and logging the access denial if not.
        """
        lastfunc = inspect.stack()[1][3]
        if not self.isOper(uid, allowAuthed=allowAuthed, allowOper=allowOper):
            log.warning('(%s) Access denied for %s calling %r', self.name,
                        self.getHostmask(uid), lastfunc)
            raise NotAuthenticatedError("You are not authenticated!")
        return True

class IrcUser():
    """PyLink IRC user class."""
    def __init__(self, nick, ts, uid, ident='null', host='null',
                 realname='PyLink dummy client', realhost='null',
                 ip='0.0.0.0', manipulatable=False, opertype='IRC Operator'):
        self.nick = nick
        self.ts = ts
        self.uid = uid
        self.ident = ident
        self.host = host
        self.realhost = realhost
        self.ip = ip
        self.realname = realname
        self.modes = set()  # Tracks user modes

        # Tracks PyLink identification status
        self.identified = ''

        # Tracks oper type (for display only)
        self.opertype = opertype

        # Tracks services identification status
        self.services_account = ''

        # Tracks channels the user is in
        self.channels = set()

        # Tracks away message status
        self.away = ''

        # This sets whether the client should be marked as manipulatable.
        # Plugins like bots.py's commands should take caution against
        # manipulating these "protected" clients, to prevent desyncs and such.
        # For "serious" service clients, this should always be False.
        self.manipulatable = manipulatable

    def __repr__(self):
        return 'IrcUser(%s)' % self.__dict__

class IrcServer():
    """PyLink IRC server class.

    uplink: The SID of this IrcServer instance's uplink. This is set to None
            for the main PyLink PseudoServer!
    name: The name of the server.
    internal: Whether the server is an internal PyLink PseudoServer.
    """

    def __init__(self, uplink, name, internal=False, desc="(None given)"):
        self.uplink = uplink
        self.users = set()
        self.internal = internal
        self.name = name.lower()
        self.desc = desc

    def __repr__(self):
        return 'IrcServer(%s)' % self.__dict__

class IrcChannel():
    """PyLink IRC channel class."""
    def __init__(self, name=None):
        # Initialize variables, such as the topic, user list, TS, who's opped, etc.
        self.users = set()
        self.modes = {('n', None), ('t', None)}
        self.topic = ''
        self.ts = int(time.time())
        self.prefixmodes = {'op': set(), 'halfop': set(), 'voice': set(),
                            'owner': set(), 'admin': set()}

        # Determines whether a topic has been set here or not. Protocol modules
        # should set this.
        self.topicset = False

        # Saves the channel name (may be useful to plugins, etc.)
        self.name = name

    def __repr__(self):
        return 'IrcChannel(%s)' % self.__dict__

    def removeuser(self, target):
        """Removes a user from a channel."""
        for s in self.prefixmodes.values():
            s.discard(target)
        self.users.discard(target)

    def deepcopy(self):
        """Returns a deep copy of the channel object."""
        return deepcopy(self)

    def isVoice(self, uid):
        """Returns whether the given user is voice in the channel."""
        return uid in self.prefixmodes['voice']

    def isHalfop(self, uid):
        """Returns whether the given user is halfop in the channel."""
        return uid in self.prefixmodes['halfop']

    def isOp(self, uid):
        """Returns whether the given user is op in the channel."""
        return uid in self.prefixmodes['op']

    def isAdmin(self, uid):
        """Returns whether the given user is admin (&) in the channel."""
        return uid in self.prefixmodes['admin']

    def isOwner(self, uid):
        """Returns whether the given user is owner (~) in the channel."""
        return uid in self.prefixmodes['owner']

    def isVoicePlus(self, uid):
        """Returns whether the given user is voice or above in the channel."""
        # If the user has any prefix mode, it has to be voice or greater.
        return bool(self.getPrefixModes(uid))

    def isHalfopPlus(self, uid):
        """Returns whether the given user is halfop or above in the channel."""
        for mode in ('halfop', 'op', 'admin', 'owner'):
            if uid in self.prefixmodes[mode]:
                return True
        return False

    def isOpPlus(self, uid):
        """Returns whether the given user is op or above in the channel."""
        for mode in ('op', 'admin', 'owner'):
            if uid in self.prefixmodes[mode]:
                return True
        return False

    def getPrefixModes(self, uid, prefixmodes=None):
        """Returns a list of all named prefix modes the given user has in the channel.

        Optionally, a prefixmodes argument can be given to look at an earlier state of
        the channel's prefix modes mapping, e.g. for checking the op status of a mode
        setter before their modes are processed and added to the channel state.
        """

        if uid not in self.users:
            raise KeyError("User %s does not exist or is not in the channel" % uid)

        result = []
        prefixmodes = prefixmodes or self.prefixmodes

        for mode, modelist in prefixmodes.items():
            if uid in modelist:
                result.append(mode)

        return result

class Protocol():
    """Base Protocol module class for PyLink."""
    def __init__(self, irc):
        self.irc = irc
        self.casemapping = 'rfc1459'
        self.hook_map = {}

    def parseArgs(self, args):
        """Parses a string of RFC1459-style arguments split into a list, where ":" may
        be used for multi-word arguments that last until the end of a line.
        """
        real_args = []
        for idx, arg in enumerate(args):
            real_args.append(arg)
            # If the argument starts with ':' and ISN'T the first argument.
            # The first argument is used for denoting the source UID/SID.
            if arg.startswith(':') and idx != 0:
                # : is used for multi-word arguments that last until the end
                # of the message. We can use list splicing here to turn them all
                # into one argument.
                # Set the last arg to a joined version of the remaining args
                arg = args[idx:]
                arg = ' '.join(arg)[1:]
                # Cut the original argument list right before the multi-word arg,
                # and then append the multi-word arg.
                real_args = args[:idx]
                real_args.append(arg)
                break
        return real_args

    def removeClient(self, numeric):
        """Internal function to remove a client from our internal state."""
        for c, v in self.irc.channels.copy().items():
            v.removeuser(numeric)
            # Clear empty non-permanent channels.
            if not (self.irc.channels[c].users or ((self.irc.cmodes.get('permanent'), None) in self.irc.channels[c].modes)):
                del self.irc.channels[c]
            assert numeric not in v.users, "IrcChannel's removeuser() is broken!"

        sid = self.irc.getServer(numeric)
        log.debug('Removing client %s from self.irc.users', numeric)
        del self.irc.users[numeric]
        log.debug('Removing client %s from self.irc.servers[%s].users', numeric, sid)
        self.irc.servers[sid].users.discard(numeric)

    def updateTS(self, channel, their_ts):
        """
        Compares the current TS of the channel given with the new TS, resetting
        all modes we have if the one given is older.
        """

        our_ts = self.irc.channels[channel].ts

        if their_ts < our_ts:
            # Channel timestamp was reset on burst
            log.debug('(%s) Setting channel TS of %s to %s from %s',
                      self.irc.name, channel, their_ts, our_ts)
            self.irc.channels[channel].ts = their_ts
            # When TS is reset, clear all modes we currently have
            self.irc.channels[channel].modes.clear()
            for p in self.irc.channels[channel].prefixmodes.values():
                p.clear()

    def _getSid(self, sname):
        """Returns the SID of a server with the given name, if present."""
        name = sname.lower()
        for k, v in self.irc.servers.items():
            if v.name.lower() == name:
                return k
        else:
            return sname  # Fall back to given text instead of None

    def _getUid(self, target):
        """Converts a nick argument to its matching UID. This differs from irc.nickToUid()
        in that it returns the original text instead of None, if no matching nick is found."""
        target = self.irc.nickToUid(target) or target
        return target

### FakeIRC classes, used for test cases

class FakeIRC(Irc):
    """Fake IRC object used for unit tests."""
    def connect(self):
        self.messages = []
        self.hookargs = []
        self.hookmsgs = []
        self.socket = None
        self.initVars()
        self.spawnMain()
        self.connected = threading.Event()
        self.connected.set()

    def run(self, data):
        """Queues a message to the fake IRC server."""
        log.debug('<- ' + data)
        hook_args = self.proto.handle_events(data)
        if hook_args is not None:
            self.hookmsgs.append(hook_args)
            self.callHooks(hook_args)

    def send(self, data):
        self.messages.append(data)
        log.debug('-> ' + data)

    def takeMsgs(self):
        """Returns a list of messages sent by the protocol module since
        the last takeMsgs() call, so we can track what has been sent."""
        msgs = self.messages
        self.messages = []
        return msgs

    def takeCommands(self, msgs):
        """Returns a list of commands parsed from the output of takeMsgs()."""
        sidprefix = ':' + self.sid
        commands = []
        for m in msgs:
            args = m.split()
            if m.startswith(sidprefix):
                commands.append(args[1])
            else:
                commands.append(args[0])
        return commands

    def takeHooks(self):
        """Returns a list of hook arguments sent by the protocol module since
        the last takeHooks() call."""
        hookmsgs = self.hookmsgs
        self.hookmsgs = []
        return hookmsgs

class FakeProto(Protocol):
    """Dummy protocol module for testing purposes."""
    def handle_events(self, data):
        pass

    def connect(self):
        pass

    def spawnClient(self, nick, *args, **kwargs):
        uid = str(randint(1, 10000000000))
        ts = int(time.time())
        self.irc.users[uid] = user = IrcUser(nick, ts, uid)
        return user

    def join(self, client, channel):
        self.irc.channels[channel].users.add(client)
        self.irc.users[client].channels.add(channel)

FakeProto.Class = FakeProto