Limnoria/src/ircdb.py

###
# Copyright (c) 2002-2009, Jeremiah Fincher
# Copyright (c) 2009, James McCoy
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
#
#   * Redistributions of source code must retain the above copyright notice,
#     this list of conditions, and the following disclaimer.
#   * Redistributions in binary form must reproduce the above copyright notice,
#     this list of conditions, and the following disclaimer in the
#     documentation and/or other materials provided with the distribution.
#   * Neither the name of the author of this software nor the name of
#     contributors to this software may be used to endorse or promote products
#     derived from this software without specific prior written consent.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
# POSSIBILITY OF SUCH DAMAGE.
###

import os
import time
import operator

from . import conf, ircutils, log, registry, unpreserve, utils, world
from .utils.iter import imap, ilen, ifilter

def isCapability(capability):
    return len(capability.split(None, 1)) == 1

def fromChannelCapability(capability):
    """Returns a (channel, capability) tuple from a channel capability."""
    assert isChannelCapability(capability), 'got %s' % capability
    return capability.split(',', 1)

def isChannelCapability(capability):
    """Returns True if capability is a channel capability; False otherwise."""
    if ',' in capability:
        (channel, capability) = capability.split(',', 1)
        return ircutils.isChannel(channel) and isCapability(capability)
    else:
        return False

def makeChannelCapability(channel, capability):
    """Makes a channel capability given a channel and a capability."""
    assert isCapability(capability), 'got %s' % capability
    assert ircutils.isChannel(channel), 'got %s' % channel
    return '%s,%s' % (channel, capability)

def isAntiCapability(capability):
    """Returns True if capability is an anticapability; False otherwise."""
    if isChannelCapability(capability):
        (_, capability) = fromChannelCapability(capability)
    return isCapability(capability) and capability[0] == '-'

def makeAntiCapability(capability):
    """Returns the anticapability of a given capability."""
    assert isCapability(capability), 'got %s' % capability
    assert not isAntiCapability(capability), \
           'makeAntiCapability does not work on anticapabilities.  ' \
           'You probably want invertCapability; got %s.' % capability
    if isChannelCapability(capability):
        (channel, capability) = fromChannelCapability(capability)
        return makeChannelCapability(channel, '-' + capability)
    else:
        return '-' + capability

def unAntiCapability(capability):
    """Takes an anticapability and returns the non-anti form."""
    assert isCapability(capability), 'got %s' % capability
    if not isAntiCapability(capability):
        raise ValueError, '%s is not an anti capability' % capability
    if isChannelCapability(capability):
        (channel, capability) = fromChannelCapability(capability)
        return ','.join((channel, capability[1:]))
    else:
        return capability[1:]

def invertCapability(capability):
    """Make a capability into an anticapability and vice versa."""
    assert isCapability(capability), 'got %s' % capability
    if isAntiCapability(capability):
        return unAntiCapability(capability)
    else:
        return makeAntiCapability(capability)

def canonicalCapability(capability):
    if callable(capability):
        capability = capability()
    assert isCapability(capability), 'got %s' % capability
    return capability.lower()

def unWildcardHostmask(hostmask):
    return hostmask.translate(utils.str.chars, '!@*?')

_invert = invertCapability
class CapabilitySet(set):
    """A subclass of set handling basic capability stuff."""
    def __init__(self, capabilities=()):
        self.__parent = super(CapabilitySet, self)
        self.__parent.__init__()
        for capability in capabilities:
            self.add(capability)

    def add(self, capability):
        """Adds a capability to the set."""
        capability = ircutils.toLower(capability)
        inverted = _invert(capability)
        if self.__parent.__contains__(inverted):
            self.__parent.remove(inverted)
        self.__parent.add(capability)

    def remove(self, capability):
        """Removes a capability from the set."""
        capability = ircutils.toLower(capability)
        self.__parent.remove(capability)

    def __contains__(self, capability):
        capability = ircutils.toLower(capability)
        if self.__parent.__contains__(capability):
            return True
        if self.__parent.__contains__(_invert(capability)):
            return True
        else:
            return False

    def check(self, capability):
        """Returns the appropriate boolean for whether a given capability is
        'allowed' given its (or its anticapability's) presence in the set.
        """
        capability = ircutils.toLower(capability)
        if self.__parent.__contains__(capability):
            return True
        elif self.__parent.__contains__(_invert(capability)):
            return False
        else:
            raise KeyError, capability

    def __repr__(self):
        return '%s([%s])' % (self.__class__.__name__,
                             ', '.join(imap(repr, self)))

antiOwner = makeAntiCapability('owner')
class UserCapabilitySet(CapabilitySet):
    """A subclass of CapabilitySet to handle the owner capability correctly."""
    def __init__(self, *args, **kwargs):
        self.__parent = super(UserCapabilitySet, self)
        self.__parent.__init__(*args, **kwargs)

    def __contains__(self, capability):
        capability = ircutils.toLower(capability)
        if capability == 'owner' or capability == antiOwner:
            return True
        elif self.__parent.__contains__('owner'):
            return True
        else:
            return self.__parent.__contains__(capability)

    def check(self, capability):
        """Returns the appropriate boolean for whether a given capability is
        'allowed' given its (or its anticapability's) presence in the set.
        Differs from CapabilitySet in that it handles the 'owner' capability
        appropriately.
        """
        capability = ircutils.toLower(capability)
        if capability == 'owner' or capability == antiOwner:
            if self.__parent.__contains__('owner'):
                return not isAntiCapability(capability)
            else:
                return isAntiCapability(capability)
        elif self.__parent.__contains__('owner'):
            if isAntiCapability(capability):
                return False
            else:
                return True
        else:
            return self.__parent.check(capability)

    def add(self, capability):
        """Adds a capability to the set.  Just make sure it's not -owner."""
        capability = ircutils.toLower(capability)
        assert capability != '-owner', '"-owner" disallowed.'
        self.__parent.add(capability)

class IrcUser(object):
    """This class holds the capabilities and authentications for a user."""
    def __init__(self, ignore=False, password='', name='',
                 capabilities=(), hostmasks=None, secure=False, hashed=False):
        self.id = None
        self.auth = [] # The (time, hostmask) list of auth crap.
        self.name = name # The name of the user.
        self.ignore = ignore # A boolean deciding if the person is ignored.
        self.secure = secure # A boolean describing if hostmasks *must* match.
        self.hashed = hashed # True if the password is hashed on disk.
        self.password = password # password (plaintext? hashed?)
        self.capabilities = UserCapabilitySet()
        for capability in capabilities:
            self.capabilities.add(capability)
        if hostmasks is None:
            self.hostmasks = ircutils.IrcSet() # hostmasks used for recognition
        else:
            self.hostmasks = hostmasks

    def __repr__(self):
        return format('%s(id=%s, ignore=%s, password="", name=%q, hashed=%r, '
                      'capabilities=%r, hostmasks=[], secure=%r)\n',
                      self.__class__.__name__, self.id, self.ignore,
                      self.name, self.hashed, self.capabilities, self.secure)

    def __hash__(self):
        return hash(self.id)

    def addCapability(self, capability):
        """Gives the user the given capability."""
        self.capabilities.add(capability)

    def removeCapability(self, capability):
        """Takes from the user the given capability."""
        self.capabilities.remove(capability)

    def _checkCapability(self, capability):
        """Checks the user for a given capability."""
        if self.ignore:
            if isAntiCapability(capability):
                return True
            else:
                return False
        else:
            return self.capabilities.check(capability)

    def setPassword(self, password, hashed=False):
        """Sets the user's password."""
        if hashed or self.hashed:
            self.hashed = True
            self.password = utils.saltHash(password)
        else:
            self.password = password

    def checkPassword(self, password):
        """Checks the user's password."""
        if password is None:
            return False
        if self.hashed:
            (salt, _) = self.password.split('|')
            return (self.password == utils.saltHash(password, salt=salt))
        else:
            return (self.password == password)

    def checkHostmask(self, hostmask, useAuth=True):
        """Checks a given hostmask against the user's hostmasks or current
        authentication.  If useAuth is False, only checks against the user's
        hostmasks.
        """
        if useAuth:
            timeout = conf.supybot.databases.users.timeoutIdentification()
            removals = []
            try:
                for (when, authmask) in self.auth:
                    if timeout and when+timeout < time.time():
                        removals.append((when, authmask))
                    elif hostmask == authmask:
                        return True
            finally:
                while removals:
                    self.auth.remove(removals.pop())
        for pat in self.hostmasks:
            if ircutils.hostmaskPatternEqual(pat, hostmask):
                return pat
        return False

    def addHostmask(self, hostmask):
        """Adds a hostmask to the user's hostmasks."""
        assert ircutils.isUserHostmask(hostmask), 'got %s' % hostmask
        if len(unWildcardHostmask(hostmask)) < 3:
            raise ValueError, \
                  'Hostmask must contain at least 3 non-wildcard characters.'
        self.hostmasks.add(hostmask)

    def removeHostmask(self, hostmask):
        """Removes a hostmask from the user's hostmasks."""
        self.hostmasks.remove(hostmask)

    def addAuth(self, hostmask):
        """Sets a user's authenticated hostmask.  This times out in 1 hour."""
        if self.checkHostmask(hostmask, useAuth=False) or not self.secure:
            self.auth.append((time.time(), hostmask))
        else:
            raise ValueError, 'secure flag set, unmatched hostmask'

    def clearAuth(self):
        """Unsets a user's authenticated hostmask."""
        for (when, hostmask) in self.auth:
            users.invalidateCache(hostmask=hostmask)
        self.auth = []

    def preserve(self, fd, indent=''):
        def write(s):
            fd.write(indent)
            fd.write(s)
            fd.write(os.linesep)
        write('name %s' % self.name)
        write('ignore %s' % self.ignore)
        write('secure %s' % self.secure)
        write('hashed %s' % self.hashed)
        write('password %s' % self.password)
        for capability in self.capabilities:
            write('capability %s' % capability)
        for hostmask in self.hostmasks:
            write('hostmask %s' % hostmask)
        fd.write(os.linesep)


class IrcChannel(object):
    """This class holds the capabilities, bans, and ignores of a channel."""
    defaultOff = ('op', 'halfop', 'voice', 'protected')
    def __init__(self, bans=None, silences=None, exceptions=None, ignores=None,
                 capabilities=None, lobotomized=False, defaultAllow=True):
        self.defaultAllow = defaultAllow
        self.expiredBans = []
        self.bans = bans or {}
        self.ignores = ignores or {}
        self.silences = silences or []
        self.exceptions = exceptions or []
        self.capabilities = capabilities or CapabilitySet()
        for capability in self.defaultOff:
            if capability not in self.capabilities:
                self.capabilities.add(makeAntiCapability(capability))
        self.lobotomized = lobotomized

    def __repr__(self):
        return '%s(bans=%r, ignores=%r, capabilities=%r, ' \
               'lobotomized=%r, defaultAllow=%s, ' \
               'silences=%r, exceptions=%r)\n' % \
               (self.__class__.__name__, self.bans, self.ignores,
                self.capabilities, self.lobotomized,
                self.defaultAllow, self.silences, self.exceptions)

    def addBan(self, hostmask, expiration=0):
        """Adds a ban to the channel banlist."""
        assert ircutils.isUserHostmask(hostmask), 'got %s' % hostmask
        self.bans[hostmask] = int(expiration)

    def removeBan(self, hostmask):
        """Removes a ban from the channel banlist."""
        assert ircutils.isUserHostmask(hostmask), 'got %s' % hostmask
        return self.bans.pop(hostmask)

    def checkBan(self, hostmask):
        """Checks whether a given hostmask is banned by the channel banlist."""
        assert ircutils.isUserHostmask(hostmask), 'got %s' % hostmask
        now = time.time()
        for (pattern, expiration) in self.bans.items():
            if now < expiration or not expiration:
                if ircutils.hostmaskPatternEqual(pattern, hostmask):
                    return True
            else:
                self.expiredBans.append((pattern, expiration))
                del self.bans[pattern]
        return False

    def addIgnore(self, hostmask, expiration=0):
        """Adds an ignore to the channel ignore list."""
        assert ircutils.isUserHostmask(hostmask), 'got %s' % hostmask
        self.ignores[hostmask] = int(expiration)

    def removeIgnore(self, hostmask):
        """Removes an ignore from the channel ignore list."""
        assert ircutils.isUserHostmask(hostmask), 'got %s' % hostmask
        return self.ignores.pop(hostmask)

    def addCapability(self, capability):
        """Adds a capability to the channel's default capabilities."""
        assert isCapability(capability), 'got %s' % capability
        self.capabilities.add(capability)

    def removeCapability(self, capability):
        """Removes a capability from the channel's default capabilities."""
        assert isCapability(capability), 'got %s' % capability
        self.capabilities.remove(capability)

    def setDefaultCapability(self, b):
        """Sets the default capability in the channel."""
        self.defaultAllow = b

    def _checkCapability(self, capability):
        """Checks whether a certain capability is allowed by the channel."""
        assert isCapability(capability), 'got %s' % capability
        if capability in self.capabilities:
            return self.capabilities.check(capability)
        else:
            if isAntiCapability(capability):
                return not self.defaultAllow
            else:
                return self.defaultAllow

    def checkIgnored(self, hostmask):
        """Checks whether a given hostmask is to be ignored by the channel."""
        if self.lobotomized:
            return True
        if world.testing:
            return False
        assert ircutils.isUserHostmask(hostmask), 'got %s' % hostmask
        if self.checkBan(hostmask):
            return True
        now = time.time()
        for (pattern, expiration) in self.ignores.items():
            if now < expiration or not expiration:
                if ircutils.hostmaskPatternEqual(pattern, hostmask):
                    return True
            else:
                del self.ignores[pattern]
                # Later we may wish to keep expiredIgnores, but not now.
        return False

    def preserve(self, fd, indent=''):
        def write(s):
            fd.write(indent)
            fd.write(s)
            fd.write(os.linesep)
        write('lobotomized %s' % self.lobotomized)
        write('defaultAllow %s' % self.defaultAllow)
        for capability in self.capabilities:
            write('capability ' + capability)
        bans = self.bans.items()
        utils.sortBy(operator.itemgetter(1), bans)
        for (ban, expiration) in bans:
            write('ban %s %d' % (ban, expiration))
        ignores = self.ignores.items()
        utils.sortBy(operator.itemgetter(1), ignores)
        for (ignore, expiration) in ignores:
            write('ignore %s %d' % (ignore, expiration))
        fd.write(os.linesep)


class Creator(object):
    def badCommand(self, command, rest, lineno):
        raise ValueError, 'Invalid command on line %s: %s' % (lineno, command)

class IrcUserCreator(Creator):
    u = None
    def __init__(self, users):
        if self.u is None:
            IrcUserCreator.u = IrcUser()
        self.users = users

    def user(self, rest, lineno):
        if self.u.id is not None:
            raise ValueError, 'Unexpected user command on line %s.' % lineno
        self.u.id = int(rest)

    def _checkId(self):
        if self.u.id is None:
            raise ValueError, 'Unexpected user description without user.'

    def name(self, rest, lineno):
        self._checkId()
        self.u.name = rest

    def ignore(self, rest, lineno):
        self._checkId()
        self.u.ignore = bool(eval(rest))

    def secure(self, rest, lineno):
        self._checkId()
        self.u.secure = bool(eval(rest))

    def hashed(self, rest, lineno):
        self._checkId()
        self.u.hashed = bool(eval(rest))

    def password(self, rest, lineno):
        self._checkId()
        self.u.password = rest

    def hostmask(self, rest, lineno):
        self._checkId()
        self.u.hostmasks.add(rest)

    def capability(self, rest, lineno):
        self._checkId()
        self.u.capabilities.add(rest)

    def finish(self):
        if self.u.name:
            try:
                self.users.setUser(self.u)
            except DuplicateHostmask:
                log.error('Hostmasks for %s collided with another user\'s.  '
                          'Resetting hostmasks for %s.', self.u.name)
                # Some might argue that this is arbitrary, and perhaps it is.
                # But we've got to do *something*, so we'll show some deference
                # to our lower-numbered users.
                self.u.hostmasks.clear()
                self.users.setUser(self.u)
            IrcUserCreator.u = None

class IrcChannelCreator(Creator):
    name = None
    def __init__(self, channels):
        self.c = IrcChannel()
        self.channels = channels
        self.hadChannel = bool(self.name)

    def channel(self, rest, lineno):
        if self.name is not None:
            raise ValueError, 'Unexpected channel command on line %s' % lineno
        IrcChannelCreator.name = rest

    def _checkId(self):
        if self.name is None:
            raise ValueError, 'Unexpected channel description without channel.'

    def lobotomized(self, rest, lineno):
        self._checkId()
        self.c.lobotomized = bool(eval(rest))

    def defaultallow(self, rest, lineno):
        self._checkId()
        self.c.defaultAllow = bool(eval(rest))

    def capability(self, rest, lineno):
        self._checkId()
        self.c.capabilities.add(rest)

    def ban(self, rest, lineno):
        self._checkId()
        (pattern, expiration) = rest.split()
        self.c.bans[pattern] = int(float(expiration))

    def ignore(self, rest, lineno):
        self._checkId()
        (pattern, expiration) = rest.split()
        self.c.ignores[pattern] = int(float(expiration))

    def finish(self):
        if self.hadChannel:
            self.channels.setChannel(self.name, self.c)
            IrcChannelCreator.name = None


class DuplicateHostmask(ValueError):
    pass

class UsersDictionary(utils.IterableMap):
    """A simple serialized-to-file User Database."""
    def __init__(self):
        self.noFlush = False
        self.filename = None
        self.users = {}
        self.nextId = 0
        self._nameCache = utils.structures.CacheDict(1000)
        self._hostmaskCache = utils.structures.CacheDict(1000)

    # This is separate because the Creator has to access our instance.
    def open(self, filename):
        self.filename = filename
        reader = unpreserve.Reader(IrcUserCreator, self)
        try:
            self.noFlush = True
            try:
                reader.readFile(filename)
                self.noFlush = False
                self.flush()
            except EnvironmentError, e:
                log.error('Invalid user dictionary file, resetting to empty.')
                log.error('Exact error: %s', utils.exnToString(e))
            except Exception, e:
                log.exception('Exact error:')
        finally:
            self.noFlush = False

    def reload(self):
        """Reloads the database from its file."""
        self.nextId = 0
        self.users.clear()
        self._nameCache.clear()
        self._hostmaskCache.clear()
        if self.filename is not None:
            try:
                self.open(self.filename)
            except EnvironmentError, e:
                log.warning('UsersDictionary.reload failed: %s', e)
        else:
            log.error('UsersDictionary.reload called with no filename.')

    def flush(self):
        """Flushes the database to its file."""
        if not self.noFlush:
            if self.filename is not None:
                L = self.users.items()
                L.sort()
                fd = utils.file.AtomicFile(self.filename)
                for (id, u) in L:
                    fd.write('user %s' % id)
                    fd.write(os.linesep)
                    u.preserve(fd, indent='  ')
                fd.close()
            else:
                log.error('UsersDictionary.flush called with no filename.')
        else:
            log.debug('Not flushing UsersDictionary because of noFlush.')

    def close(self):
        self.flush()
        if self.flush in world.flushers:
            world.flushers.remove(self.flush)
        self.users.clear()

    def iteritems(self):
        return self.users.iteritems()

    def getUserId(self, s):
        """Returns the user ID of a given name or hostmask."""
        if ircutils.isUserHostmask(s):
            try:
                return self._hostmaskCache[s]
            except KeyError:
                ids = {}
                for (id, user) in self.users.iteritems():
                    x = user.checkHostmask(s)
                    if x:
                        ids[id] = x
                if len(ids) == 1:
                    id = ids.keys()[0]
                    self._hostmaskCache[s] = id
                    try:
                        self._hostmaskCache[id].add(s)
                    except KeyError:
                        self._hostmaskCache[id] = set([s])
                    return id
                elif len(ids) == 0:
                    raise KeyError, s
                else:
                    log.error('Multiple matches found in user database.  '
                              'Removing the offending hostmasks.')
                    for (id, hostmask) in ids.iteritems():
                        log.error('Removing %q from user %s.', hostmask, id)
                        self.users[id].removeHostmask(hostmask)
                    raise DuplicateHostmask, 'Ids %r matched.' % ids
        else: # Not a hostmask, must be a name.
            s = s.lower()
            try:
                return self._nameCache[s]
            except KeyError:
                for (id, user) in self.users.items():
                    if s == user.name.lower():
                        self._nameCache[s] = id
                        self._nameCache[id] = s
                        return id
                else:
                    raise KeyError, s

    def getUser(self, id):
        """Returns a user given its id, name, or hostmask."""
        if not isinstance(id, int):
            # Must be a string.  Get the UserId first.
            id = self.getUserId(id)
        u = self.users[id]
        while isinstance(u, int):
            id = u
            u = self.users[id]
        u.id = id
        return u

    def hasUser(self, id):
        """Returns the database has a user given its id, name, or hostmask."""
        try:
            self.getUser(id)
            return True
        except KeyError:
            return False

    def numUsers(self):
        return len(self.users)

    def invalidateCache(self, id=None, hostmask=None, name=None):
        if hostmask is not None:
            if hostmask in self._hostmaskCache:
                id = self._hostmaskCache.pop(hostmask)
                self._hostmaskCache[id].remove(hostmask)
                if not self._hostmaskCache[id]:
                    del self._hostmaskCache[id]
        if name is not None:
            del self._nameCache[self._nameCache[id]]
            del self._nameCache[id]
        if id is not None:
            if id in self._nameCache:
                del self._nameCache[self._nameCache[id]]
                del self._nameCache[id]
            if id in self._hostmaskCache:
                for hostmask in self._hostmaskCache[id]:
                    del self._hostmaskCache[hostmask]
                del self._hostmaskCache[id]

    def setUser(self, user, flush=True):
        """Sets a user (given its id) to the IrcUser given it."""
        self.nextId = max(self.nextId, user.id)
        try:
            if self.getUserId(user.name) != user.id:
                raise DuplicateHostmask, hostmask
        except KeyError:
            pass
        for hostmask in user.hostmasks:
            for (i, u) in self.iteritems():
                if i == user.id:
                    continue
                elif u.checkHostmask(hostmask):
                    # We used to remove the hostmask here, but it's not
                    # appropriate for us both to remove the hostmask and to
                    # raise an exception.  So instead, we'll raise an
                    # exception, but be nice and give the offending hostmask
                    # back at the same time.
                    raise DuplicateHostmask, hostmask
                for otherHostmask in u.hostmasks:
                    if ircutils.hostmaskPatternEqual(hostmask, otherHostmask):
                        raise DuplicateHostmask, hostmask
        self.invalidateCache(user.id)
        self.users[user.id] = user
        if flush:
            self.flush()

    def delUser(self, id):
        """Removes a user from the database."""
        del self.users[id]
        if id in self._nameCache:
            del self._nameCache[self._nameCache[id]]
            del self._nameCache[id]
        if id in self._hostmaskCache:
            for hostmask in self._hostmaskCache[id]:
                del self._hostmaskCache[hostmask]
            del self._hostmaskCache[id]
        self.flush()

    def newUser(self):
        """Allocates a new user in the database and returns it and its id."""
        user = IrcUser(hashed=True)
        self.nextId += 1
        id = self.nextId
        self.users[id] = user
        self.flush()
        user.id = id
        return user


class ChannelsDictionary(utils.IterableMap):
    def __init__(self):
        self.noFlush = False
        self.filename = None
        self.channels = ircutils.IrcDict()

    def open(self, filename):
        self.noFlush = True
        try:
            self.filename = filename
            reader = unpreserve.Reader(IrcChannelCreator, self)
            try:
                reader.readFile(filename)
                self.noFlush = False
                self.flush()
            except EnvironmentError, e:
                log.error('Invalid channel database, resetting to empty.')
                log.error('Exact error: %s', utils.exnToString(e))
            except Exception, e:
                log.error('Invalid channel database, resetting to empty.')
                log.exception('Exact error:')
        finally:
            self.noFlush = False

    def flush(self):
        """Flushes the channel database to its file."""
        if not self.noFlush:
            if self.filename is not None:
                fd = utils.file.AtomicFile(self.filename)
                for (channel, c) in self.channels.iteritems():
                    fd.write('channel %s' % channel)
                    fd.write(os.linesep)
                    c.preserve(fd, indent='  ')
                fd.close()
            else:
                log.warning('ChannelsDictionary.flush without self.filename.')
        else:
            log.debug('Not flushing ChannelsDictionary because of noFlush.')

    def close(self):
        self.flush()
        if self.flush in world.flushers:
            world.flushers.remove(self.flush)
        self.channels.clear()

    def reload(self):
        """Reloads the channel database from its file."""
        if self.filename is not None:
            self.channels.clear()
            try:
                self.open(self.filename)
            except EnvironmentError, e:
                log.warning('ChannelsDictionary.reload failed: %s', e)
        else:
            log.warning('ChannelsDictionary.reload without self.filename.')

    def getChannel(self, channel):
        """Returns an IrcChannel object for the given channel."""
        channel = channel.lower()
        if channel in self.channels:
            return self.channels[channel]
        else:
            c = IrcChannel()
            self.channels[channel] = c
            return c

    def setChannel(self, channel, ircChannel):
        """Sets a given channel to the IrcChannel object given."""
        channel = channel.lower()
        self.channels[channel] = ircChannel
        self.flush()

    def iteritems(self):
        return self.channels.iteritems()


class IgnoresDB(object):
    def __init__(self):
        self.filename = None
        self.hostmasks = {}

    def open(self, filename):
        self.filename = filename
        fd = file(self.filename)
        for line in utils.file.nonCommentNonEmptyLines(fd):
            try:
                line = line.rstrip('\r\n')
                L = line.split()
                hostmask = L.pop(0)
                if L:
                    expiration = int(float(L.pop(0)))
                else:
                    expiration = 0
                self.add(hostmask, expiration)
            except Exception, e:
                log.error('Invalid line in ignores database: %q', line)
        fd.close()

    def flush(self):
        if self.filename is not None:
            fd = utils.file.AtomicFile(self.filename)
            now = time.time()
            for (hostmask, expiration) in self.hostmasks.items():
                if now < expiration or not expiration:
                    fd.write('%s %s' % (hostmask, expiration))
                    fd.write(os.linesep)
            fd.close()
        else:
            log.warning('IgnoresDB.flush called without self.filename.')

    def close(self):
        if self.flush in world.flushers:
            world.flushers.remove(self.flush)
        self.flush()
        self.hostmasks.clear()

    def reload(self):
        if self.filename is not None:
            oldhostmasks = self.hostmasks.copy()
            self.hostmasks.clear()
            try:
                self.open(self.filename)
            except EnvironmentError, e:
                log.warning('IgnoresDB.reload failed: %s', e)
                # Let's be somewhat transactional.
                self.hostmasks.update(oldhostmasks)
        else:
            log.warning('IgnoresDB.reload called without self.filename.')

    def checkIgnored(self, prefix):
        now = time.time()
        for (hostmask, expiration) in self.hostmasks.items():
            if expiration and now > expiration:
                del self.hostmasks[hostmask]
            else:
                if ircutils.hostmaskPatternEqual(hostmask, prefix):
                    return True
        return False

    def add(self, hostmask, expiration=0):
        assert ircutils.isUserHostmask(hostmask), 'got %s' % hostmask
        self.hostmasks[hostmask] = expiration

    def remove(self, hostmask):
        del self.hostmasks[hostmask]


confDir = conf.supybot.directories.conf()
try:
    userFile = os.path.join(confDir, conf.supybot.databases.users.filename())
    users = UsersDictionary()
    users.open(userFile)
except EnvironmentError, e:
    log.warning('Couldn\'t open user database: %s', e)

try:
    channelFile = os.path.join(confDir,
                               conf.supybot.databases.channels.filename())
    channels = ChannelsDictionary()
    channels.open(channelFile)
except EnvironmentError, e:
    log.warning('Couldn\'t open channel database: %s', e)

try:
    ignoreFile = os.path.join(confDir,
                              conf.supybot.databases.ignores.filename())
    ignores = IgnoresDB()
    ignores.open(ignoreFile)
except EnvironmentError, e:
    log.warning('Couldn\'t open ignore database: %s', e)


world.flushers.append(users.flush)
world.flushers.append(ignores.flush)
world.flushers.append(channels.flush)


###
# Useful functions for checking credentials.
###
def checkIgnored(hostmask, recipient='', users=users, channels=channels):
    """checkIgnored(hostmask, recipient='') -> True/False

    Checks if the user is ignored by the recipient of the message.
    """
    try:
        id = users.getUserId(hostmask)
        user = users.getUser(id)
        if user._checkCapability('owner'):
            # Owners shouldn't ever be ignored.
            return False
        elif user.ignore:
            log.debug('Ignoring %s due to his IrcUser ignore flag.', hostmask)
            return True
    except KeyError:
        # If there's no user...
        if conf.supybot.defaultIgnore():
            log.debug('Ignoring %s due to conf.supybot.defaultIgnore',
                     hostmask)
            return True
    if ignores.checkIgnored(hostmask):
        log.debug('Ignoring %s due to ignore database.', hostmask)
        return True
    if ircutils.isChannel(recipient):
        channel = channels.getChannel(recipient)
        if channel.checkIgnored(hostmask):
            log.debug('Ignoring %s due to the channel ignores.', hostmask)
            return True
    return False

def _x(capability, ret):
    if isAntiCapability(capability):
        return not ret
    else:
        return ret

def _checkCapabilityForUnknownUser(capability, users=users, channels=channels):
    if isChannelCapability(capability):
        (channel, capability) = fromChannelCapability(capability)
        try:
            c = channels.getChannel(channel)
            if capability in c.capabilities:
                return c._checkCapability(capability)
            else:
                return _x(capability, c.defaultAllow)
        except KeyError:
            pass
    defaultCapabilities = conf.supybot.capabilities()
    if capability in defaultCapabilities:
        return defaultCapabilities.check(capability)
    else:
        return _x(capability, conf.supybot.capabilities.default())

def checkCapability(hostmask, capability, users=users, channels=channels):
    """Checks that the user specified by name/hostmask has the capability given.
    """
    if world.testing:
        return _x(capability, True)
    try:
        u = users.getUser(hostmask)
        if u.secure and not u.checkHostmask(hostmask, useAuth=False):
            raise KeyError
    except KeyError:
        # Raised when no hostmasks match.
        return _checkCapabilityForUnknownUser(capability, users=users,
                                              channels=channels)
    except ValueError, e:
        # Raised when multiple hostmasks match.
        log.warning('%s: %s', hostmask, e)
        return _checkCapabilityForUnknownUser(capability, users=users,
                                              channels=channels)
    if capability in u.capabilities:
        return u._checkCapability(capability)
    else:
        if isChannelCapability(capability):
            (channel, capability) = fromChannelCapability(capability)
            try:
                chanop = makeChannelCapability(channel, 'op')
                if u._checkCapability(chanop):
                    return _x(capability, True)
            except KeyError:
                pass
            c = channels.getChannel(channel)
            if capability in c.capabilities:
                return c._checkCapability(capability)
            else:
                return _x(capability, c.defaultAllow)
        defaultCapabilities = conf.supybot.capabilities()
        if capability in defaultCapabilities:
            return defaultCapabilities.check(capability)
        else:
            return _x(capability, conf.supybot.capabilities.default())


def checkCapabilities(hostmask, capabilities, requireAll=False):
    """Checks that a user has capabilities in a list.

    requireAll is True if *all* capabilities in the list must be had, False if
    *any* of the capabilities in the list must be had.
    """
    for capability in capabilities:
        if requireAll:
            if not checkCapability(hostmask, capability):
                return False
        else:
            if checkCapability(hostmask, capability):
                return True
    return requireAll

###
# supybot.capabilities
###

class DefaultCapabilities(registry.SpaceSeparatedListOfStrings):
    List = CapabilitySet
    # We use a keyword argument trick here to prevent eval'ing of code that
    # changes allowDefaultOwner from affecting this.  It's not perfect, but
    # it's still an improvement, raising the bar for potential crackers.
    def setValue(self, v, allowDefaultOwner=conf.allowDefaultOwner):
        registry.SpaceSeparatedListOfStrings.setValue(self, v)
        if '-owner' not in self.value and not allowDefaultOwner:
            print '*** You must run supybot with the --allow-default-owner'
            print '*** option in order to allow a default capability of owner.'
            print '*** Don\'t do that, it\'s dumb.'
            self.value.add('-owner')

conf.registerGlobalValue(conf.supybot, 'capabilities',
    DefaultCapabilities(['-owner', '-admin', '-trusted'], """These are the
    capabilities that are given to everyone by default.  If they are normal
    capabilities, then the user will have to have the appropriate
    anti-capability if you want to override these capabilities; if they are
    anti-capabilities, then the user will have to have the actual capability
    to override these capabilities.  See docs/CAPABILITIES if you don't
    understand why these default to what they do."""))

conf.registerGlobalValue(conf.supybot.capabilities, 'default',
    registry.Boolean(True, """Determines whether the bot by default will allow
    users to have a capability.  If this is disabled, a user must explicitly
    have the capability for whatever command he wishes to run."""))


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