File: collabwrapper.py

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# Copyright (C) 2015 Walter Bender
# Copyright (C) 2015 Sam Parkinson
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this library; if not, write to the Free Software
# Foundation, 51 Franklin Street, Suite 500 Boston, MA 02110-1335 USA

'''
The wrapper module provides an abstraction over the Sugar
collaboration system.

Using CollabWrapper
-------------------
1. Add `get_data` and `set_data` methods to the activity class::

    def get_data(self):
        # return plain python objects - things that can be encoded
        # using the json module
        return dict(
            text=self._entry.get_text()
        )

    def set_data(self, data):
        # data will be the same object returned by get_data
        self._entry.set_text(data.get('text'))

2. Make a CollabWrapper instance::

    def __init__(self, handle):
        sugar3.activity.activity.Activity.__init__(self, handle)
        self._collab = CollabWrapper(self)
        self._collab.connect('message', self.__message_cb)

        # setup your activity here

        self._collab.setup()

3. Post any changes of shared state to the CollabWrapper.  The changes
   will be sent to other buddies if any are connected, for example::

    def __entry_changed_cb(self, *args):
        self._collab.post(dict(
            action='entry_changed',
            new_text=self._entry.get_text()
        ))

4. Handle incoming messages, for example::

    def __message_cb(self, collab, buddy, msg):
        action = msg.get('action')
        if action == 'entry_changed':
            self._entry.set_text(msg.get('new_text'))

'''

import os
import json
import socket
from gettext import gettext as _

from gi.repository import GObject
from gi.repository import Gio
from gi.repository import GLib
import dbus

from telepathy.interfaces import \
    CHANNEL_INTERFACE, \
    CHANNEL_INTERFACE_GROUP, \
    CHANNEL_TYPE_TEXT, \
    CHANNEL_TYPE_FILE_TRANSFER, \
    CONN_INTERFACE_ALIASING, \
    CONNECTION_INTERFACE_REQUESTS, \
    CHANNEL, \
    CLIENT
from telepathy.constants import \
    CHANNEL_GROUP_FLAG_CHANNEL_SPECIFIC_HANDLES, \
    CONNECTION_HANDLE_TYPE_CONTACT, \
    CHANNEL_TEXT_MESSAGE_TYPE_NORMAL, \
    CONNECTION_HANDLE_TYPE_CONTACT, \
    SOCKET_ADDRESS_TYPE_UNIX, \
    SOCKET_ACCESS_CONTROL_LOCALHOST
from telepathy.client import Connection, Channel

from sugar3.presence import presenceservice
from sugar3.activity.activity import SCOPE_PRIVATE
from sugar3.graphics.alert import NotifyAlert, Alert

import logging
_logger = logging.getLogger('text-channel-wrapper')

ACTION_INIT_REQUEST = '!!ACTION_INIT_REQUEST'
ACTION_INIT_RESPONSE = '!!ACTION_INIT_RESPONSE'
ACTIVITY_FT_MIME = 'x-sugar/from-activity'


class CollabWrapper(GObject.GObject):
    '''
    The wrapper provides a high level abstraction over the
    collaboration system.  The wrapper deals with setting up the
    channels, encoding and decoding messages, initialization and
    alerting the caller to the status.

    An activity instance is initially private, but may be shared.  Once
    shared, an instance will remain shared for as long as the activity
    runs.  On stop, the journal will preserve the instance as shared,
    and on resume the instance will be shared again.

    When the caller shares an activity instance, they are the leader,
    and other buddies may join.  The instance is now a shared activity.

    When the caller joins a shared activity, the leader will call
    `get_data`, and the caller's `set_data` will be called with the
    result.

    The `joined` signal is emitted when the caller joins a shared
    activity.  One or more `buddy_joined` signals will be emitted before
    this signal.  The signal is not emitted to the caller who first
    shared the activity.  There are no arguments.

    The `buddy_joined` signal is emitted when another buddy joins the
    shared activity.  At least one will be emitted before the `joined`
    signal.  The caller will never be mentioned, but is assumed to be
    part of the set.  The signal passes a
    :class:`sugar3.presence.buddy.Buddy` as the only argument.

    The `buddy_left` signal is emitted when another user leaves the
    shared activity.  The signal is not emitted during quit.  The signal
    passes a :class:`sugar3.presence.buddy.Buddy` as the only argument.

    Any buddy may call `post` to send a message to all buddies.  Each
    buddy will receive a `message` signal.

    The `message` signal is emitted when a `post` is received from any
    buddy.  The signal has two arguments.  The first is a
    :class:`sugar3.presence.buddy.Buddy`. The second is the message.

    Any buddy may call `send_file_memory` or `send_file_file` to
    transfer a file to all buddies.  A description is to be given.
    Each buddy will receive an `incoming_file` signal.

    The `incoming_file` signal is emitted when a file transfer is
    received.  The signal has two arguments.  The first is a
    :class:`sugar3.presence.filetransfer.IncomingFileTransfer`.  The
    second is the description.
    '''

    message = GObject.Signal('message', arg_types=[object, object])
    joined = GObject.Signal('joined')
    buddy_joined = GObject.Signal('buddy_joined', arg_types=[object])
    buddy_left = GObject.Signal('buddy_left', arg_types=[object])
    incoming_file = GObject.Signal('incoming_file', arg_types=[object, object])

    def __init__(self, activity):
        GObject.GObject.__init__(self)
        self.activity = activity
        self.shared_activity = activity.shared_activity
        self._leader = False
        self._init_waiting = False
        self._text_channel = None

    def setup(self):
        '''
        Setup must be called so that the activity can join or share
        if appropriate.

        .. note::
            As soon as setup is called, any signal, `get_data` or
            `set_data` call may occur.  This means that the activity
            must have set up enough so these functions can work.  For
            example, call setup at the end of the activity
            `__init__` function.
        '''
        # Some glue to know if we are launching, joining, or resuming
        # a shared activity.
        if self.shared_activity:
            # We're joining the activity.
            self.activity.connect("joined", self.__joined_cb)

            if self.activity.get_shared():
                _logger.debug('calling _joined_cb')
                self.__joined_cb(self)
            else:
                _logger.debug('Joining activity...')
                self._alert(_('Joining activity...'),
                            _('Please wait for the connection...'))
        else:
            self._leader = True
            if not self.activity.metadata or self.activity.metadata.get(
                    'share-scope', SCOPE_PRIVATE) == \
                    SCOPE_PRIVATE:
                # We are creating a new activity instance.
                _logger.debug('Off-line')
            else:
                # We are sharing an old activity instance.
                _logger.debug('On-line')
                self._alert(_('Resuming shared activity...'),
                            _('Please wait for the connection...'))
            self.activity.connect('shared', self.__shared_cb)

    def _alert(self, title, msg=None):
        a = NotifyAlert()
        a.props.title = title
        a.props.msg = msg
        self.activity.add_alert(a)
        a.connect('response', lambda a, r: self.activity.remove_alert(a))
        a.show()

    def __shared_cb(self, sender):
        ''' Callback for when activity is shared. '''
        self.shared_activity = self.activity.shared_activity
        self._setup_text_channel()
        self._listen_for_channels()
        _logger.debug('I am sharing...')

    def __joined_cb(self, sender):
        '''Callback for when an activity is joined.'''
        self.shared_activity = self.activity.shared_activity
        if not self.shared_activity:
            return

        self._setup_text_channel()
        self._listen_for_channels()
        self._init_waiting = True
        self.post({'action': ACTION_INIT_REQUEST})

        for buddy in self.shared_activity.get_joined_buddies():
            self.buddy_joined.emit(buddy)

        _logger.debug('I joined a shared activity.')
        self.joined.emit()

    def _setup_text_channel(self):
        ''' Set up a text channel to use for collaboration. '''
        self._text_channel = _TextChannelWrapper(
            self.shared_activity.telepathy_text_chan,
            self.shared_activity.telepathy_conn)

        # Tell the text channel what callback to use for incoming
        # text messages.
        self._text_channel.set_received_callback(self.__received_cb)

        # Tell the text channel what callbacks to use when buddies
        # come and go.
        self.shared_activity.connect('buddy-joined', self.__buddy_joined_cb)
        self.shared_activity.connect('buddy-left', self.__buddy_left_cb)

    def _listen_for_channels(self):
        conn = self.shared_activity.telepathy_conn
        conn.connect_to_signal('NewChannels', self.__new_channels_cb)

    def __new_channels_cb(self, channels):
        conn = self.shared_activity.telepathy_conn
        for path, props in channels:
            if props[CHANNEL + '.Requested']:
                continue  # This channel was requested by me

            channel_type = props[CHANNEL + '.ChannelType']
            if channel_type == CHANNEL_TYPE_FILE_TRANSFER:
                self._handle_ft_channel(conn, path, props)

    def _handle_ft_channel(self, conn, path, props):
        ft = IncomingFileTransfer(conn, path, props)
        if ft.description == ACTION_INIT_RESPONSE:
            ft.connect('notify::state', self.__notify_ft_state_cb)
            ft.accept_to_memory()
        else:
            desc = json.loads(ft.description)
            self.incoming_file.emit(ft, desc)

    def __notify_ft_state_cb(self, ft, pspec):
        if ft.props.state == FT_STATE_COMPLETED and self._init_waiting:
            stream = ft.props.output
            stream.close(None)
            # FIXME:  The data prop seems to just be the raw pointer
            gbytes = stream.steal_as_bytes()
            data = gbytes.get_data()
            logging.debug('Got init data from buddy:  %s', data)
            data = json.loads(data)
            self.activity.set_data(data)
            self._init_waiting = False

    def __received_cb(self, buddy, msg):
        '''Process a message when it is received.'''
        action = msg.get('action')
        if action == ACTION_INIT_REQUEST and self._leader:
            data = self.activity.get_data()
            data = json.dumps(data)
            OutgoingBlobTransfer(
                buddy,
                self.shared_activity.telepathy_conn,
                data,
                self.get_client_name(),
                ACTION_INIT_RESPONSE,
                ACTIVITY_FT_MIME)
            return

        if buddy:
            nick = buddy.props.nick
        else:
            nick = '???'
        _logger.debug('Received message from %s: %r', nick, msg)
        self.message.emit(buddy, msg)

    def send_file_memory(self, buddy, data, description):
        '''
        Send a one to one file transfer from memory to a buddy.  The
        buddy will get the file transfer and description through the
        `incoming_transfer` signal.

        Args:
            buddy (sugar3.presence.buddy.Buddy), buddy to send to.
            data (str), the data to send.
            description (object), a json encodable description for the
                transfer.  This will be given to the
                `incoming_transfer` signal at the buddy.
        '''
        OutgoingBlobTransfer(
            buddy,
            self.shared_activity.telepathy_conn,
            data,
            self.get_client_name(),
            json.dumps(description),
            ACTIVITY_FT_MIME)

    def send_file_file(self, buddy, path, description):
        '''
        Send a one to one file transfer from a filesystem path to a
        given buddy.  The buddy will get the file transfer and
        description through the `incoming_transfer` signal.

        Args:
            buddy (sugar3.presence.buddy.Buddy), buddy to send to.
            path (str), path of the file containing the data to send.
            description (object), a json encodable description for the
                transfer.  This will be given to the
                `incoming_transfer` signal at the buddy.
        '''
        OutgoingFileTransfer(
            buddy,
            self.shared_activity.telepathy_conn,
            path,
            self.get_client_name(),
            json.dumps(description),
            ACTIVITY_FT_MIME)

    def post(self, msg):
        '''
        Send a message to all buddies.  If the activity is not shared,
        no message is sent.

        Args:
            msg (object): json encodable object to send,
                eg. :class:`dict` or :class:`str`.
        '''
        if self._text_channel is not None:
            self._text_channel.post(msg)

    def __buddy_joined_cb(self, sender, buddy):
        '''A buddy joined.'''
        self.buddy_joined.emit(buddy)

    def __buddy_left_cb(self, sender, buddy):
        '''A buddy left.'''
        self.buddy_left.emit(buddy)

    def get_client_name(self):
        '''
        Get the name of the activity's telepathy client.

        Returns: str, telepathy client name
        '''
        return CLIENT + '.' + self.activity.get_bundle_id()

    @GObject.property
    def leader(self):
        '''
        Boolean of if this client is the leader in this activity.  The
        way the leader is decided may change, however there should only
        ever be one leader for an activity.
        '''
        return self._leader


FT_STATE_NONE = 0
FT_STATE_PENDING = 1
FT_STATE_ACCEPTED = 2
FT_STATE_OPEN = 3
FT_STATE_COMPLETED = 4
FT_STATE_CANCELLED = 5

FT_REASON_NONE = 0
FT_REASON_REQUESTED = 1
FT_REASON_LOCAL_STOPPED = 2
FT_REASON_REMOTE_STOPPED = 3
FT_REASON_LOCAL_ERROR = 4
FT_REASON_LOCAL_ERROR = 5
FT_REASON_REMOTE_ERROR = 6


class _BaseFileTransfer(GObject.GObject):
    '''
    The base file transfer should not be used directly.  It is used as a
    base class for the incoming and outgoing file transfers.

    Props:
        filename (str), metadata provided by the buddy
        file_size (str), size of the file being sent/received, in bytes
        description (str), metadata provided by the buddy
        mime_type (str), metadata provided by the buddy
        buddy (:class:`sugar3.presence.buddy.Buddy`), other party
            in the transfer
        reason_last_change (FT_REASON_*), reason for the last state change

    GObject Props:
        state (FT_STATE_*), current state of the transfer
        transferred_bytes (int), number of bytes transfered so far
    '''


    def __init__(self):
        GObject.GObject.__init__(self)
        self._state = FT_STATE_NONE
        self._transferred_bytes = 0

        self.channel = None
        self.buddy = None
        self.filename = None
        self.file_size = None
        self.description = None
        self.mime_type = None
        self.reason_last_change = FT_REASON_NONE

    def set_channel(self, channel):
        '''
        Setup the file transfer to use a given telepathy channel.  This
        should only be used by direct subclasses of the base file transfer.
        '''
        self.channel = channel
        self.channel[CHANNEL_TYPE_FILE_TRANSFER].connect_to_signal(
            'FileTransferStateChanged', self.__state_changed_cb)
        self.channel[CHANNEL_TYPE_FILE_TRANSFER].connect_to_signal(
            'TransferredBytesChanged', self.__transferred_bytes_changed_cb)
        self.channel[CHANNEL_TYPE_FILE_TRANSFER].connect_to_signal(
            'InitialOffsetDefined', self.__initial_offset_defined_cb)

        channel_properties = self.channel[dbus.PROPERTIES_IFACE]

        props = channel_properties.GetAll(CHANNEL_TYPE_FILE_TRANSFER)
        self._state = props['State']
        self.filename = props['Filename']
        self.file_size = props['Size']
        self.description = props['Description']
        self.mime_type = props['ContentType']

    def __transferred_bytes_changed_cb(self, transferred_bytes):
        logging.debug('__transferred_bytes_changed_cb %r', transferred_bytes)
        self.props.transferred_bytes = transferred_bytes

    def _set_transferred_bytes(self, transferred_bytes):
        self._transferred_bytes = transferred_bytes

    def _get_transferred_bytes(self):
        return self._transferred_bytes

    transferred_bytes = GObject.property(type=int,
                                         default=0,
                                         getter=_get_transferred_bytes,
                                         setter=_set_transferred_bytes)

    def __initial_offset_defined_cb(self, offset):
        logging.debug('__initial_offset_defined_cb %r', offset)
        self.initial_offset = offset

    def __state_changed_cb(self, state, reason):
        logging.debug('__state_changed_cb %r %r', state, reason)
        self.reason_last_change = reason
        self.props.state = state

    def _set_state(self, state):
        self._state = state

    def _get_state(self):
        return self._state

    state = GObject.property(type=int, getter=_get_state, setter=_set_state)

    def cancel(self):
        '''
        Request that telepathy close the file transfer channel

        Spec:  http://telepathy.freedesktop.org/spec/Channel.html#Method:Close
        '''
        self.channel[CHANNEL].Close()


class IncomingFileTransfer(_BaseFileTransfer):
    '''
    An incoming file transfer from another buddy.  You need to first accept
    the transfer (either to memory or to a file).  Then you need to listen
    to the state and wait until the transfer is completed.  Then you can
    read the file that it was saved to, or access the
    :class:`Gio.MemoryOutputStream` from the `output` property.

    The `output` property is different depending on how the file was accepted.
    If the file was accepted to a file on the file system, it is a string
    representing the path to the file.  If the file was accepted to memory,
    it is a :class:`Gio.MemoryOutputStream`.
    '''

    def __init__(self, connection, object_path, props):
        _BaseFileTransfer.__init__(self)

        channel = Channel(connection.bus_name, object_path)
        self.set_channel(channel)

        self.connect('notify::state', self.__notify_state_cb)

        self._destination_path = None
        self._output_stream = None
        self._socket_address = None
        self._socket = None
        self._splicer = None

    def accept_to_file(self, destination_path):
        '''
        Accept the file transfer and write it to a new file.  The file must
        already exist.

        Args:
            destination_path (str): the path where a new file will be
                created and saved to
        '''
        if os.path.exists(destination_path):
            raise ValueError('Destination path already exists: %r' %
                             destination_path)

        self._destination_path = destination_path
        self._accept()

    def accept_to_memory(self):
        '''
        Accept the file transfer.  Once the state is FT_STATE_OPEN, a
        :class:`Gio.MemoryOutputStream` accessible via the output prop.
        '''
        self._accept()

    def _accept(self):
        channel_ft = self.channel[CHANNEL_TYPE_FILE_TRANSFER]
        self._socket_address = channel_ft.AcceptFile(
            SOCKET_ADDRESS_TYPE_UNIX,
            SOCKET_ACCESS_CONTROL_LOCALHOST,
            '',
            0,
            byte_arrays=True)

    def __notify_state_cb(self, file_transfer, pspec):
        logging.debug('__notify_state_cb %r', self.props.state)
        if self.props.state == FT_STATE_OPEN:
            # Need to hold a reference to the socket so that python doesn't
            # close the fd when it goes out of scope
            self._socket = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
            self._socket.connect(self._socket_address)
            input_stream = Gio.UnixInputStream.new(self._socket.fileno(), True)

            if self._destination_path is not None:
                destination_file = Gio.File.new_for_path(
                    self._destination_path)
                if self.initial_offset == 0:
                    self._output_stream = destination_file.create(
                        Gio.FileCreateFlags.PRIVATE, None)
                else:
                    self._output_stream = destination_file.append_to()
            else:
                self._output_stream = Gio.MemoryOutputStream.new_resizable()

            self._output_stream.splice_async(
                input_stream,
                Gio.OutputStreamSpliceFlags.CLOSE_SOURCE |
                Gio.OutputStreamSpliceFlags.CLOSE_TARGET,
                GLib.PRIORITY_LOW, None, None, None)

    @GObject.Property
    def output(self):
        return self._destination_path or self._output_stream


class _BaseOutgoingTransfer(_BaseFileTransfer):
    '''
    This class provides the base of an outgoing file transfer.

    You can override the `_get_input_stream` method to return any type of
    Gio input stream.  This will then be used to provide the file if
    requested by the application.  You also need to call `_create_channel`
    with the length of the file in bytes during your `__init__`.

    Args:
        buddy (sugar3.presence.buddy.Buddy), who to send the transfer to
        conn (telepathy.client.conn.Connection), telepathy connection to
            use to send the transfer.  Eg. `shared_activity.telepathy_conn`
        filename (str), metadata sent to the receiver
        description (str), metadata sent to the receiver
        mime (str), metadata sent to the receiver
    '''

    def __init__(self, buddy, conn, filename, description, mime):
        _BaseFileTransfer.__init__(self)
        self.connect('notify::state', self.__notify_state_cb)

        self._socket_address = None
        self._socket = None
        self._splicer = None
        self._conn = conn
        self._filename = filename
        self._description = description
        self._mime = mime
        self.buddy = buddy

    def _create_channel(self, file_size):
        object_path, properties_ = self._conn.CreateChannel(dbus.Dictionary({
            CHANNEL + '.ChannelType': CHANNEL_TYPE_FILE_TRANSFER,
            CHANNEL + '.TargetHandleType': CONNECTION_HANDLE_TYPE_CONTACT,
            CHANNEL + '.TargetHandle': self.buddy.contact_handle,
            CHANNEL_TYPE_FILE_TRANSFER + '.Filename': self._filename,
            CHANNEL_TYPE_FILE_TRANSFER + '.Description': self._description,
            CHANNEL_TYPE_FILE_TRANSFER + '.Size': file_size,
            CHANNEL_TYPE_FILE_TRANSFER + '.ContentType': self._mime,
            CHANNEL_TYPE_FILE_TRANSFER + '.InitialOffset': 0}, signature='sv'))
        self.set_channel(Channel(self._conn.bus_name, object_path))

        channel_file_transfer = self.channel[CHANNEL_TYPE_FILE_TRANSFER]
        self._socket_address = channel_file_transfer.ProvideFile(
            SOCKET_ADDRESS_TYPE_UNIX, SOCKET_ACCESS_CONTROL_LOCALHOST, '',
            byte_arrays=True)

    def _get_input_stream(self):
        raise NotImplementedError()

    def __notify_state_cb(self, file_transfer, pspec):
        if self.props.state == FT_STATE_OPEN:
            # Need to hold a reference to the socket so that python doesn't
            # closes the fd when it goes out of scope
            self._socket = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
            self._socket.connect(self._socket_address)
            output_stream = Gio.UnixOutputStream.new(
                self._socket.fileno(), True)

            input_stream = self._get_input_stream()
            output_stream.splice_async(
                input_stream,
                Gio.OutputStreamSpliceFlags.CLOSE_SOURCE |
                Gio.OutputStreamSpliceFlags.CLOSE_TARGET,
                GLib.PRIORITY_LOW, None, None, None)


class OutgoingFileTransfer(_BaseOutgoingTransfer):
    '''
    An outgoing file transfer to send from a file (on the computer's file
    system).

    Note that the `path` argument is the path for the file that will be
    sent, whereas the `filename` argument is only for metadata.

    Args:
        path (str), path of the file to send
    '''

    def __init__(self, buddy, conn, path, filename, description, mime):
        _BaseOutgoingTransfer.__init__(
            self, buddy, conn, filename, description, mime)

        self._path = path
        file_size = os.stat(path).st_size
        self._create_channel(file_size)

    def _get_input_stream(self):
        input_stream = Gio.File.new_for_path(self._path).read(None)


class OutgoingBlobTransfer(_BaseOutgoingTransfer):
    '''
    An outgoing file transfer to send from a string in memory.

    Args:
        blob (str), data to send
    '''

    def __init__(self, buddy, conn, blob, filename, description, mime):
        _BaseOutgoingTransfer.__init__(
            self, buddy, conn, filename, description, mime)

        self._blob = blob
        self._create_channel(len(self._blob))

    def _get_input_stream(self):
        return Gio.MemoryInputStream.new_from_data(self._blob, None)


class _TextChannelWrapper(object):
    '''Wrapper for a telepathy Text Channel'''

    def __init__(self, text_chan, conn):
        '''Connect to the text channel'''
        self._activity_cb = None
        self._activity_close_cb = None
        self._text_chan = text_chan
        self._conn = conn
        self._signal_matches = []
        m = self._text_chan[CHANNEL_INTERFACE].connect_to_signal(
            'Closed', self._closed_cb)
        self._signal_matches.append(m)

    def post(self, msg):
        if msg is not None:
            _logger.debug('post')
            self._send(json.dumps(msg))

    def _send(self, text):
        '''Send text over the Telepathy text channel.'''
        _logger.debug('sending %s' % text)

        if self._text_chan is not None:
            self._text_chan[CHANNEL_TYPE_TEXT].Send(
                CHANNEL_TEXT_MESSAGE_TYPE_NORMAL, text)

    def close(self):
        '''Close the text channel.'''
        _logger.debug('Closing text channel')
        try:
            self._text_chan[CHANNEL_INTERFACE].Close()
        except Exception:
            _logger.debug('Channel disappeared!')
            self._closed_cb()

    def _closed_cb(self):
        '''Clean up text channel.'''
        for match in self._signal_matches:
            match.remove()
        self._signal_matches = []
        self._text_chan = None
        if self._activity_close_cb is not None:
            self._activity_close_cb()

    def set_received_callback(self, callback):
        '''Connect the function callback to the signal.

        callback -- callback function taking buddy and text args
        '''
        if self._text_chan is None:
            return
        self._activity_cb = callback
        m = self._text_chan[CHANNEL_TYPE_TEXT].connect_to_signal(
            'Received', self._received_cb)
        self._signal_matches.append(m)

    def handle_pending_messages(self):
        '''Get pending messages and show them as received.'''
        for identity, timestamp, sender, type_, flags, text in \
            self._text_chan[
                CHANNEL_TYPE_TEXT].ListPendingMessages(False):
            self._received_cb(identity, timestamp, sender, type_, flags, text)

    def _received_cb(self, identity, timestamp, sender, type_, flags, text):
        '''Handle received text from the text channel.

        Converts sender to a Buddy.
        Calls self._activity_cb which is a callback to the activity.
        '''
        _logger.debug('received_cb %r %s' % (type_, text))
        if type_ != 0:
            # Exclude any auxiliary messages
            return

        msg = json.loads(text)

        if self._activity_cb:
            try:
                self._text_chan[CHANNEL_INTERFACE_GROUP]
            except Exception:
                # One to one XMPP chat
                nick = self._conn[
                    CONN_INTERFACE_ALIASING].RequestAliases([sender])[0]
                buddy = {'nick': nick, 'color': '#000000,#808080'}
                _logger.debug('exception: recieved from sender %r buddy %r' %
                              (sender, buddy))
            else:
                # XXX: cache these
                buddy = self._get_buddy(sender)
                _logger.debug('Else: recieved from sender %r buddy %r' %
                              (sender, buddy))

            self._activity_cb(buddy, msg)
            self._text_chan[
                CHANNEL_TYPE_TEXT].AcknowledgePendingMessages([identity])
        else:
            _logger.debug('Throwing received message on the floor'
                          ' since there is no callback connected. See'
                          ' set_received_callback')

    def set_closed_callback(self, callback):
        '''Connect a callback for when the text channel is closed.

        callback -- callback function taking no args

        '''
        _logger.debug('set closed callback')
        self._activity_close_cb = callback

    def _get_buddy(self, cs_handle):
        '''Get a Buddy from a (possibly channel-specific) handle.'''
        # XXX This will be made redundant once Presence Service
        # provides buddy resolution

        # Get the Presence Service
        pservice = presenceservice.get_instance()

        # Get the Telepathy Connection
        tp_name, tp_path = pservice.get_preferred_connection()
        conn = Connection(tp_name, tp_path)
        group = self._text_chan[CHANNEL_INTERFACE_GROUP]
        my_csh = group.GetSelfHandle()
        if my_csh == cs_handle:
            handle = conn.GetSelfHandle()
        elif (group.GetGroupFlags() &
              CHANNEL_GROUP_FLAG_CHANNEL_SPECIFIC_HANDLES):
            handle = group.GetHandleOwners([cs_handle])[0]
        else:
            handle = cs_handle

            # XXX: deal with failure to get the handle owner
            assert handle != 0

        return pservice.get_buddy_by_telepathy_handle(
            tp_name, tp_path, handle)