# -*- coding: utf-8 -*-
# Copyright 2016 OpenMarket Ltd
# Copyright 2018 New Vector Ltd
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import abc
import logging

from six.moves import http_client

from signedjson.key import decode_verify_key_bytes
from signedjson.sign import verify_signed_json
from unpaddedbase64 import decode_base64

from twisted.internet import defer

import synapse.server
import synapse.types
from synapse.api.constants import EventTypes, Membership
from synapse.api.errors import AuthError, Codes, SynapseError
from synapse.types import RoomID, UserID
from synapse.util.async import Linearizer
from synapse.util.distributor import user_joined_room, user_left_room

logger = logging.getLogger(__name__)

id_server_scheme = "https://"


class RoomMemberHandler(object):
    # TODO(paul): This handler currently contains a messy conflation of
    #   low-level API that works on UserID objects and so on, and REST-level
    #   API that takes ID strings and returns pagination chunks. These concerns
    #   ought to be separated out a lot better.

    __metaclass__ = abc.ABCMeta

    def __init__(self, hs):
        """

        Args:
            hs (synapse.server.HomeServer):
        """
        self.hs = hs
        self.store = hs.get_datastore()
        self.auth = hs.get_auth()
        self.state_handler = hs.get_state_handler()
        self.config = hs.config
        self.simple_http_client = hs.get_simple_http_client()

        self.federation_handler = hs.get_handlers().federation_handler
        self.directory_handler = hs.get_handlers().directory_handler
        self.registration_handler = hs.get_handlers().registration_handler
        self.profile_handler = hs.get_profile_handler()
        self.event_creation_hander = hs.get_event_creation_handler()

        self.member_linearizer = Linearizer(name="member")

        self.clock = hs.get_clock()
        self.spam_checker = hs.get_spam_checker()
        self._server_notices_mxid = self.config.server_notices_mxid

    @abc.abstractmethod
    def _remote_join(self, requester, remote_room_hosts, room_id, user, content):
        """Try and join a room that this server is not in

        Args:
            requester (Requester)
            remote_room_hosts (list[str]): List of servers that can be used
                to join via.
            room_id (str): Room that we are trying to join
            user (UserID): User who is trying to join
            content (dict): A dict that should be used as the content of the
                join event.

        Returns:
            Deferred
        """
        raise NotImplementedError()

    @abc.abstractmethod
    def _remote_reject_invite(self, remote_room_hosts, room_id, target):
        """Attempt to reject an invite for a room this server is not in. If we
        fail to do so we locally mark the invite as rejected.

        Args:
            requester (Requester)
            remote_room_hosts (list[str]): List of servers to use to try and
                reject invite
            room_id (str)
            target (UserID): The user rejecting the invite

        Returns:
            Deferred[dict]: A dictionary to be returned to the client, may
            include event_id etc, or nothing if we locally rejected
        """
        raise NotImplementedError()

    @abc.abstractmethod
    def get_or_register_3pid_guest(self, requester, medium, address, inviter_user_id):
        """Get a guest access token for a 3PID, creating a guest account if
        one doesn't already exist.

        Args:
            requester (Requester)
            medium (str)
            address (str)
            inviter_user_id (str): The user ID who is trying to invite the
                3PID

        Returns:
            Deferred[(str, str)]: A 2-tuple of `(user_id, access_token)` of the
            3PID guest account.
        """
        raise NotImplementedError()

    @abc.abstractmethod
    def _user_joined_room(self, target, room_id):
        """Notifies distributor on master process that the user has joined the
        room.

        Args:
            target (UserID)
            room_id (str)

        Returns:
            Deferred|None
        """
        raise NotImplementedError()

    @abc.abstractmethod
    def _user_left_room(self, target, room_id):
        """Notifies distributor on master process that the user has left the
        room.

        Args:
            target (UserID)
            room_id (str)

        Returns:
            Deferred|None
        """
        raise NotImplementedError()

    @defer.inlineCallbacks
    def _local_membership_update(
        self, requester, target, room_id, membership,
        prev_events_and_hashes,
        txn_id=None,
        ratelimit=True,
        content=None,
    ):
        if content is None:
            content = {}

        content["membership"] = membership
        if requester.is_guest:
            content["kind"] = "guest"

        event, context = yield self.event_creation_hander.create_event(
            requester,
            {
                "type": EventTypes.Member,
                "content": content,
                "room_id": room_id,
                "sender": requester.user.to_string(),
                "state_key": target.to_string(),

                # For backwards compatibility:
                "membership": membership,
            },
            token_id=requester.access_token_id,
            txn_id=txn_id,
            prev_events_and_hashes=prev_events_and_hashes,
        )

        # Check if this event matches the previous membership event for the user.
        duplicate = yield self.event_creation_hander.deduplicate_state_event(
            event, context,
        )
        if duplicate is not None:
            # Discard the new event since this membership change is a no-op.
            defer.returnValue(duplicate)

        yield self.event_creation_hander.handle_new_client_event(
            requester,
            event,
            context,
            extra_users=[target],
            ratelimit=ratelimit,
        )

        prev_member_event_id = context.prev_state_ids.get(
            (EventTypes.Member, target.to_string()),
            None
        )

        if event.membership == Membership.JOIN:
            # Only fire user_joined_room if the user has acutally joined the
            # room. Don't bother if the user is just changing their profile
            # info.
            newly_joined = True
            if prev_member_event_id:
                prev_member_event = yield self.store.get_event(prev_member_event_id)
                newly_joined = prev_member_event.membership != Membership.JOIN
            if newly_joined:
                yield self._user_joined_room(target, room_id)
        elif event.membership == Membership.LEAVE:
            if prev_member_event_id:
                prev_member_event = yield self.store.get_event(prev_member_event_id)
                if prev_member_event.membership == Membership.JOIN:
                    yield self._user_left_room(target, room_id)

        defer.returnValue(event)

    @defer.inlineCallbacks
    def update_membership(
            self,
            requester,
            target,
            room_id,
            action,
            txn_id=None,
            remote_room_hosts=None,
            third_party_signed=None,
            ratelimit=True,
            content=None,
    ):
        key = (room_id,)

        with (yield self.member_linearizer.queue(key)):
            result = yield self._update_membership(
                requester,
                target,
                room_id,
                action,
                txn_id=txn_id,
                remote_room_hosts=remote_room_hosts,
                third_party_signed=third_party_signed,
                ratelimit=ratelimit,
                content=content,
            )

        defer.returnValue(result)

    @defer.inlineCallbacks
    def _update_membership(
            self,
            requester,
            target,
            room_id,
            action,
            txn_id=None,
            remote_room_hosts=None,
            third_party_signed=None,
            ratelimit=True,
            content=None,
    ):
        content_specified = bool(content)
        if content is None:
            content = {}
        else:
            # We do a copy here as we potentially change some keys
            # later on.
            content = dict(content)

        effective_membership_state = action
        if action in ["kick", "unban"]:
            effective_membership_state = "leave"

        # if this is a join with a 3pid signature, we may need to turn a 3pid
        # invite into a normal invite before we can handle the join.
        if third_party_signed is not None:
            yield self.federation_handler.exchange_third_party_invite(
                third_party_signed["sender"],
                target.to_string(),
                room_id,
                third_party_signed,
            )

        if not remote_room_hosts:
            remote_room_hosts = []

        if effective_membership_state not in ("leave", "ban",):
            is_blocked = yield self.store.is_room_blocked(room_id)
            if is_blocked:
                raise SynapseError(403, "This room has been blocked on this server")

        if effective_membership_state == Membership.INVITE:
            # block any attempts to invite the server notices mxid
            if target.to_string() == self._server_notices_mxid:
                raise SynapseError(
                    http_client.FORBIDDEN,
                    "Cannot invite this user",
                )

            block_invite = False

            if (self._server_notices_mxid is not None and
                    requester.user.to_string() == self._server_notices_mxid):
                # allow the server notices mxid to send invites
                is_requester_admin = True

            else:
                is_requester_admin = yield self.auth.is_server_admin(
                    requester.user,
                )

            if not is_requester_admin:
                if self.config.block_non_admin_invites:
                    logger.info(
                        "Blocking invite: user is not admin and non-admin "
                        "invites disabled"
                    )
                    block_invite = True

                if not self.spam_checker.user_may_invite(
                    requester.user.to_string(), target.to_string(), room_id,
                ):
                    logger.info("Blocking invite due to spam checker")
                    block_invite = True

            if block_invite:
                raise SynapseError(
                    403, "Invites have been disabled on this server",
                )

        prev_events_and_hashes = yield self.store.get_prev_events_for_room(
            room_id,
        )
        latest_event_ids = (
            event_id for (event_id, _, _) in prev_events_and_hashes
        )
        current_state_ids = yield self.state_handler.get_current_state_ids(
            room_id, latest_event_ids=latest_event_ids,
        )

        old_state_id = current_state_ids.get((EventTypes.Member, target.to_string()))
        if old_state_id:
            old_state = yield self.store.get_event(old_state_id, allow_none=True)
            old_membership = old_state.content.get("membership") if old_state else None
            if action == "unban" and old_membership != "ban":
                raise SynapseError(
                    403,
                    "Cannot unban user who was not banned"
                    " (membership=%s)" % old_membership,
                    errcode=Codes.BAD_STATE
                )
            if old_membership == "ban" and action != "unban":
                raise SynapseError(
                    403,
                    "Cannot %s user who was banned" % (action,),
                    errcode=Codes.BAD_STATE
                )

            if old_state:
                same_content = content == old_state.content
                same_membership = old_membership == effective_membership_state
                same_sender = requester.user.to_string() == old_state.sender
                if same_sender and same_membership and same_content:
                    defer.returnValue(old_state)

            # we don't allow people to reject invites to the server notice
            # room, but they can leave it once they are joined.
            if (
                old_membership == Membership.INVITE and
                effective_membership_state == Membership.LEAVE
            ):
                is_blocked = yield self._is_server_notice_room(room_id)
                if is_blocked:
                    raise SynapseError(
                        http_client.FORBIDDEN,
                        "You cannot reject this invite",
                        errcode=Codes.CANNOT_LEAVE_SERVER_NOTICE_ROOM,
                    )

        is_host_in_room = yield self._is_host_in_room(current_state_ids)

        if effective_membership_state == Membership.JOIN:
            if requester.is_guest:
                guest_can_join = yield self._can_guest_join(current_state_ids)
                if not guest_can_join:
                    # This should be an auth check, but guests are a local concept,
                    # so don't really fit into the general auth process.
                    raise AuthError(403, "Guest access not allowed")

            if not is_host_in_room:
                inviter = yield self._get_inviter(target.to_string(), room_id)
                if inviter and not self.hs.is_mine(inviter):
                    remote_room_hosts.append(inviter.domain)

                content["membership"] = Membership.JOIN

                profile = self.profile_handler
                if not content_specified:
                    content["displayname"] = yield profile.get_displayname(target)
                    content["avatar_url"] = yield profile.get_avatar_url(target)

                if requester.is_guest:
                    content["kind"] = "guest"

                ret = yield self._remote_join(
                    requester, remote_room_hosts, room_id, target, content
                )
                defer.returnValue(ret)

        elif effective_membership_state == Membership.LEAVE:
            if not is_host_in_room:
                # perhaps we've been invited
                inviter = yield self._get_inviter(target.to_string(), room_id)
                if not inviter:
                    raise SynapseError(404, "Not a known room")

                if self.hs.is_mine(inviter):
                    # the inviter was on our server, but has now left. Carry on
                    # with the normal rejection codepath.
                    #
                    # This is a bit of a hack, because the room might still be
                    # active on other servers.
                    pass
                else:
                    # send the rejection to the inviter's HS.
                    remote_room_hosts = remote_room_hosts + [inviter.domain]
                    res = yield self._remote_reject_invite(
                        requester, remote_room_hosts, room_id, target,
                    )
                    defer.returnValue(res)

        res = yield self._local_membership_update(
            requester=requester,
            target=target,
            room_id=room_id,
            membership=effective_membership_state,
            txn_id=txn_id,
            ratelimit=ratelimit,
            prev_events_and_hashes=prev_events_and_hashes,
            content=content,
        )
        defer.returnValue(res)

    @defer.inlineCallbacks
    def send_membership_event(
            self,
            requester,
            event,
            context,
            remote_room_hosts=None,
            ratelimit=True,
    ):
        """
        Change the membership status of a user in a room.

        Args:
            requester (Requester): The local user who requested the membership
                event. If None, certain checks, like whether this homeserver can
                act as the sender, will be skipped.
            event (SynapseEvent): The membership event.
            context: The context of the event.
            is_guest (bool): Whether the sender is a guest.
            room_hosts ([str]): Homeservers which are likely to already be in
                the room, and could be danced with in order to join this
                homeserver for the first time.
            ratelimit (bool): Whether to rate limit this request.
        Raises:
            SynapseError if there was a problem changing the membership.
        """
        remote_room_hosts = remote_room_hosts or []

        target_user = UserID.from_string(event.state_key)
        room_id = event.room_id

        if requester is not None:
            sender = UserID.from_string(event.sender)
            assert sender == requester.user, (
                "Sender (%s) must be same as requester (%s)" %
                (sender, requester.user)
            )
            assert self.hs.is_mine(sender), "Sender must be our own: %s" % (sender,)
        else:
            requester = synapse.types.create_requester(target_user)

        prev_event = yield self.event_creation_hander.deduplicate_state_event(
            event, context,
        )
        if prev_event is not None:
            return

        if event.membership == Membership.JOIN:
            if requester.is_guest:
                guest_can_join = yield self._can_guest_join(context.prev_state_ids)
                if not guest_can_join:
                    # This should be an auth check, but guests are a local concept,
                    # so don't really fit into the general auth process.
                    raise AuthError(403, "Guest access not allowed")

        if event.membership not in (Membership.LEAVE, Membership.BAN):
            is_blocked = yield self.store.is_room_blocked(room_id)
            if is_blocked:
                raise SynapseError(403, "This room has been blocked on this server")

        yield self.event_creation_hander.handle_new_client_event(
            requester,
            event,
            context,
            extra_users=[target_user],
            ratelimit=ratelimit,
        )

        prev_member_event_id = context.prev_state_ids.get(
            (EventTypes.Member, event.state_key),
            None
        )

        if event.membership == Membership.JOIN:
            # Only fire user_joined_room if the user has acutally joined the
            # room. Don't bother if the user is just changing their profile
            # info.
            newly_joined = True
            if prev_member_event_id:
                prev_member_event = yield self.store.get_event(prev_member_event_id)
                newly_joined = prev_member_event.membership != Membership.JOIN
            if newly_joined:
                yield self._user_joined_room(target_user, room_id)
        elif event.membership == Membership.LEAVE:
            if prev_member_event_id:
                prev_member_event = yield self.store.get_event(prev_member_event_id)
                if prev_member_event.membership == Membership.JOIN:
                    yield self._user_left_room(target_user, room_id)

    @defer.inlineCallbacks
    def _can_guest_join(self, current_state_ids):
        """
        Returns whether a guest can join a room based on its current state.
        """
        guest_access_id = current_state_ids.get((EventTypes.GuestAccess, ""), None)
        if not guest_access_id:
            defer.returnValue(False)

        guest_access = yield self.store.get_event(guest_access_id)

        defer.returnValue(
            guest_access
            and guest_access.content
            and "guest_access" in guest_access.content
            and guest_access.content["guest_access"] == "can_join"
        )

    @defer.inlineCallbacks
    def lookup_room_alias(self, room_alias):
        """
        Get the room ID associated with a room alias.

        Args:
            room_alias (RoomAlias): The alias to look up.
        Returns:
            A tuple of:
                The room ID as a RoomID object.
                Hosts likely to be participating in the room ([str]).
        Raises:
            SynapseError if room alias could not be found.
        """
        directory_handler = self.directory_handler
        mapping = yield directory_handler.get_association(room_alias)

        if not mapping:
            raise SynapseError(404, "No such room alias")

        room_id = mapping["room_id"]
        servers = mapping["servers"]

        defer.returnValue((RoomID.from_string(room_id), servers))

    @defer.inlineCallbacks
    def _get_inviter(self, user_id, room_id):
        invite = yield self.store.get_invite_for_user_in_room(
            user_id=user_id,
            room_id=room_id,
        )
        if invite:
            defer.returnValue(UserID.from_string(invite.sender))

    @defer.inlineCallbacks
    def do_3pid_invite(
            self,
            room_id,
            inviter,
            medium,
            address,
            id_server,
            requester,
            txn_id
    ):
        if self.config.block_non_admin_invites:
            is_requester_admin = yield self.auth.is_server_admin(
                requester.user,
            )
            if not is_requester_admin:
                raise SynapseError(
                    403, "Invites have been disabled on this server",
                    Codes.FORBIDDEN,
                )

        invitee = yield self._lookup_3pid(
            id_server, medium, address
        )

        if invitee:
            yield self.update_membership(
                requester,
                UserID.from_string(invitee),
                room_id,
                "invite",
                txn_id=txn_id,
            )
        else:
            yield self._make_and_store_3pid_invite(
                requester,
                id_server,
                medium,
                address,
                room_id,
                inviter,
                txn_id=txn_id
            )

    @defer.inlineCallbacks
    def _lookup_3pid(self, id_server, medium, address):
        """Looks up a 3pid in the passed identity server.

        Args:
            id_server (str): The server name (including port, if required)
                of the identity server to use.
            medium (str): The type of the third party identifier (e.g. "email").
            address (str): The third party identifier (e.g. "foo@example.com").

        Returns:
            str: the matrix ID of the 3pid, or None if it is not recognized.
        """
        try:
            data = yield self.simple_http_client.get_json(
                "%s%s/_matrix/identity/api/v1/lookup" % (id_server_scheme, id_server,),
                {
                    "medium": medium,
                    "address": address,
                }
            )

            if "mxid" in data:
                if "signatures" not in data:
                    raise AuthError(401, "No signatures on 3pid binding")
                yield self._verify_any_signature(data, id_server)
                defer.returnValue(data["mxid"])

        except IOError as e:
            logger.warn("Error from identity server lookup: %s" % (e,))
            defer.returnValue(None)

    @defer.inlineCallbacks
    def _verify_any_signature(self, data, server_hostname):
        if server_hostname not in data["signatures"]:
            raise AuthError(401, "No signature from server %s" % (server_hostname,))
        for key_name, signature in data["signatures"][server_hostname].items():
            key_data = yield self.simple_http_client.get_json(
                "%s%s/_matrix/identity/api/v1/pubkey/%s" %
                (id_server_scheme, server_hostname, key_name,),
            )
            if "public_key" not in key_data:
                raise AuthError(401, "No public key named %s from %s" %
                                (key_name, server_hostname,))
            verify_signed_json(
                data,
                server_hostname,
                decode_verify_key_bytes(key_name, decode_base64(key_data["public_key"]))
            )
            return

    @defer.inlineCallbacks
    def _make_and_store_3pid_invite(
            self,
            requester,
            id_server,
            medium,
            address,
            room_id,
            user,
            txn_id
    ):
        room_state = yield self.state_handler.get_current_state(room_id)

        inviter_display_name = ""
        inviter_avatar_url = ""
        member_event = room_state.get((EventTypes.Member, user.to_string()))
        if member_event:
            inviter_display_name = member_event.content.get("displayname", "")
            inviter_avatar_url = member_event.content.get("avatar_url", "")

        canonical_room_alias = ""
        canonical_alias_event = room_state.get((EventTypes.CanonicalAlias, ""))
        if canonical_alias_event:
            canonical_room_alias = canonical_alias_event.content.get("alias", "")

        room_name = ""
        room_name_event = room_state.get((EventTypes.Name, ""))
        if room_name_event:
            room_name = room_name_event.content.get("name", "")

        room_join_rules = ""
        join_rules_event = room_state.get((EventTypes.JoinRules, ""))
        if join_rules_event:
            room_join_rules = join_rules_event.content.get("join_rule", "")

        room_avatar_url = ""
        room_avatar_event = room_state.get((EventTypes.RoomAvatar, ""))
        if room_avatar_event:
            room_avatar_url = room_avatar_event.content.get("url", "")

        token, public_keys, fallback_public_key, display_name = (
            yield self._ask_id_server_for_third_party_invite(
                requester=requester,
                id_server=id_server,
                medium=medium,
                address=address,
                room_id=room_id,
                inviter_user_id=user.to_string(),
                room_alias=canonical_room_alias,
                room_avatar_url=room_avatar_url,
                room_join_rules=room_join_rules,
                room_name=room_name,
                inviter_display_name=inviter_display_name,
                inviter_avatar_url=inviter_avatar_url
            )
        )

        yield self.event_creation_hander.create_and_send_nonmember_event(
            requester,
            {
                "type": EventTypes.ThirdPartyInvite,
                "content": {
                    "display_name": display_name,
                    "public_keys": public_keys,

                    # For backwards compatibility:
                    "key_validity_url": fallback_public_key["key_validity_url"],
                    "public_key": fallback_public_key["public_key"],
                },
                "room_id": room_id,
                "sender": user.to_string(),
                "state_key": token,
            },
            txn_id=txn_id,
        )

    @defer.inlineCallbacks
    def _ask_id_server_for_third_party_invite(
            self,
            requester,
            id_server,
            medium,
            address,
            room_id,
            inviter_user_id,
            room_alias,
            room_avatar_url,
            room_join_rules,
            room_name,
            inviter_display_name,
            inviter_avatar_url
    ):
        """
        Asks an identity server for a third party invite.

        Args:
            requester (Requester)
            id_server (str): hostname + optional port for the identity server.
            medium (str): The literal string "email".
            address (str): The third party address being invited.
            room_id (str): The ID of the room to which the user is invited.
            inviter_user_id (str): The user ID of the inviter.
            room_alias (str): An alias for the room, for cosmetic notifications.
            room_avatar_url (str): The URL of the room's avatar, for cosmetic
                notifications.
            room_join_rules (str): The join rules of the email (e.g. "public").
            room_name (str): The m.room.name of the room.
            inviter_display_name (str): The current display name of the
                inviter.
            inviter_avatar_url (str): The URL of the inviter's avatar.

        Returns:
            A deferred tuple containing:
                token (str): The token which must be signed to prove authenticity.
                public_keys ([{"public_key": str, "key_validity_url": str}]):
                    public_key is a base64-encoded ed25519 public key.
                fallback_public_key: One element from public_keys.
                display_name (str): A user-friendly name to represent the invited
                    user.
        """

        is_url = "%s%s/_matrix/identity/api/v1/store-invite" % (
            id_server_scheme, id_server,
        )

        invite_config = {
            "medium": medium,
            "address": address,
            "room_id": room_id,
            "room_alias": room_alias,
            "room_avatar_url": room_avatar_url,
            "room_join_rules": room_join_rules,
            "room_name": room_name,
            "sender": inviter_user_id,
            "sender_display_name": inviter_display_name,
            "sender_avatar_url": inviter_avatar_url,
        }

        if self.config.invite_3pid_guest:
            guest_access_token, guest_user_id = yield self.get_or_register_3pid_guest(
                requester=requester,
                medium=medium,
                address=address,
                inviter_user_id=inviter_user_id,
            )

            invite_config.update({
                "guest_access_token": guest_access_token,
                "guest_user_id": guest_user_id,
            })

        data = yield self.simple_http_client.post_urlencoded_get_json(
            is_url,
            invite_config
        )
        # TODO: Check for success
        token = data["token"]
        public_keys = data.get("public_keys", [])
        if "public_key" in data:
            fallback_public_key = {
                "public_key": data["public_key"],
                "key_validity_url": "%s%s/_matrix/identity/api/v1/pubkey/isvalid" % (
                    id_server_scheme, id_server,
                ),
            }
        else:
            fallback_public_key = public_keys[0]

        if not public_keys:
            public_keys.append(fallback_public_key)
        display_name = data["display_name"]
        defer.returnValue((token, public_keys, fallback_public_key, display_name))

    @defer.inlineCallbacks
    def _is_host_in_room(self, current_state_ids):
        # Have we just created the room, and is this about to be the very
        # first member event?
        create_event_id = current_state_ids.get(("m.room.create", ""))
        if len(current_state_ids) == 1 and create_event_id:
            defer.returnValue(self.hs.is_mine_id(create_event_id))

        for etype, state_key in current_state_ids:
            if etype != EventTypes.Member or not self.hs.is_mine_id(state_key):
                continue

            event_id = current_state_ids[(etype, state_key)]
            event = yield self.store.get_event(event_id, allow_none=True)
            if not event:
                continue

            if event.membership == Membership.JOIN:
                defer.returnValue(True)

        defer.returnValue(False)

    @defer.inlineCallbacks
    def _is_server_notice_room(self, room_id):
        if self._server_notices_mxid is None:
            defer.returnValue(False)
        user_ids = yield self.store.get_users_in_room(room_id)
        defer.returnValue(self._server_notices_mxid in user_ids)


class RoomMemberMasterHandler(RoomMemberHandler):
    def __init__(self, hs):
        super(RoomMemberMasterHandler, self).__init__(hs)

        self.distributor = hs.get_distributor()
        self.distributor.declare("user_joined_room")
        self.distributor.declare("user_left_room")

    @defer.inlineCallbacks
    def _remote_join(self, requester, remote_room_hosts, room_id, user, content):
        """Implements RoomMemberHandler._remote_join
        """
        # filter ourselves out of remote_room_hosts: do_invite_join ignores it
        # and if it is the only entry we'd like to return a 404 rather than a
        # 500.

        remote_room_hosts = [
            host for host in remote_room_hosts if host != self.hs.hostname
        ]

        if len(remote_room_hosts) == 0:
            raise SynapseError(404, "No known servers")

        # We don't do an auth check if we are doing an invite
        # join dance for now, since we're kinda implicitly checking
        # that we are allowed to join when we decide whether or not we
        # need to do the invite/join dance.
        yield self.federation_handler.do_invite_join(
            remote_room_hosts,
            room_id,
            user.to_string(),
            content,
        )
        yield self._user_joined_room(user, room_id)

    @defer.inlineCallbacks
    def _remote_reject_invite(self, requester, remote_room_hosts, room_id, target):
        """Implements RoomMemberHandler._remote_reject_invite
        """
        fed_handler = self.federation_handler
        try:
            ret = yield fed_handler.do_remotely_reject_invite(
                remote_room_hosts,
                room_id,
                target.to_string(),
            )
            defer.returnValue(ret)
        except Exception as e:
            # if we were unable to reject the exception, just mark
            # it as rejected on our end and plough ahead.
            #
            # The 'except' clause is very broad, but we need to
            # capture everything from DNS failures upwards
            #
            logger.warn("Failed to reject invite: %s", e)

            yield self.store.locally_reject_invite(
                target.to_string(), room_id
            )
            defer.returnValue({})

    def get_or_register_3pid_guest(self, requester, medium, address, inviter_user_id):
        """Implements RoomMemberHandler.get_or_register_3pid_guest
        """
        rg = self.registration_handler
        return rg.get_or_register_3pid_guest(medium, address, inviter_user_id)

    def _user_joined_room(self, target, room_id):
        """Implements RoomMemberHandler._user_joined_room
        """
        return user_joined_room(self.distributor, target, room_id)

    def _user_left_room(self, target, room_id):
        """Implements RoomMemberHandler._user_left_room
        """
        return user_left_room(self.distributor, target, room_id)

    @defer.inlineCallbacks
    def forget(self, user, room_id):
        user_id = user.to_string()

        member = yield self.state_handler.get_current_state(
            room_id=room_id,
            event_type=EventTypes.Member,
            state_key=user_id
        )
        membership = member.membership if member else None

        if membership is not None and membership not in [
            Membership.LEAVE, Membership.BAN
        ]:
            raise SynapseError(400, "User %s in room %s" % (
                user_id, room_id
            ))

        if membership:
            yield self.store.forget(user_id, room_id)
