text: # Copyright 2014 - 2016 OpenMarket Ltd
  # Copyright 2018-2019 New Vector Ltd
  # Copyright 2019 The Matrix.org Foundation C.I.C.
  #
  # 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.
  
  """Contains functions for performing events on rooms."""
  
  import itertools
  import logging
  import math
  import random
  import string
  from collections import OrderedDict
  from typing import TYPE_CHECKING, Any, Awaitable, Dict, List, Optional, Tuple
  
  from synapse.api.constants import (
      EventTypes,
      HistoryVisibility,
      JoinRules,
      Membership,
      RoomCreationPreset,
      RoomEncryptionAlgorithms,
  )
  from synapse.api.errors import (
      AuthError,
      Codes,
      LimitExceededError,
      NotFoundError,
      StoreError,
      SynapseError,
  )
  from synapse.api.filtering import Filter
  from synapse.api.room_versions import KNOWN_ROOM_VERSIONS, RoomVersion
  from synapse.events import EventBase
  from synapse.events.utils import copy_power_levels_contents
  from synapse.rest.admin._base import assert_user_is_admin
  from synapse.storage.state import StateFilter
  from synapse.types import (
      JsonDict,
      MutableStateMap,
      Requester,
      RoomAlias,
      RoomID,
      RoomStreamToken,
      StateMap,
      StreamToken,
      UserID,
      create_requester,
  )
  from synapse.util import stringutils
  from synapse.util.async_helpers import Linearizer
  from synapse.util.caches.response_cache import ResponseCache
  from synapse.util.stringutils import parse_and_validate_server_name
  from synapse.visibility import filter_events_for_client
  
  from ._base import BaseHandler
  
  if TYPE_CHECKING:
      from synapse.server import HomeServer
  
  logger = logging.getLogger(__name__)
  
  id_server_scheme = "https://"
  
  FIVE_MINUTES_IN_MS = 5 * 60 * 1000
  
  
  class RoomCreationHandler(BaseHandler):
      def __init__(self, hs: "HomeServer"):
          super().__init__(hs)
  
          self.spam_checker = hs.get_spam_checker()
          self.event_creation_handler = hs.get_event_creation_handler()
          self.room_member_handler = hs.get_room_member_handler()
          self._event_auth_handler = hs.get_event_auth_handler()
          self.config = hs.config
  
          # Room state based off defined presets
          self._presets_dict = {
              RoomCreationPreset.PRIVATE_CHAT: {
                  "join_rules": JoinRules.INVITE,
                  "history_visibility": HistoryVisibility.SHARED,
                  "original_invitees_have_ops": False,
                  "guest_can_join": True,
                  "power_level_content_override": {"invite": 0},
              },
              RoomCreationPreset.TRUSTED_PRIVATE_CHAT: {
                  "join_rules": JoinRules.INVITE,
                  "history_visibility": HistoryVisibility.SHARED,
                  "original_invitees_have_ops": True,
                  "guest_can_join": True,
                  "power_level_content_override": {"invite": 0},
              },
              RoomCreationPreset.PUBLIC_CHAT: {
                  "join_rules": JoinRules.PUBLIC,
                  "history_visibility": HistoryVisibility.SHARED,
                  "original_invitees_have_ops": False,
                  "guest_can_join": False,
                  "power_level_content_override": {},
              },
          }  # type: Dict[str, Dict[str, Any]]
  
          # Modify presets to selectively enable encryption by default per homeserver config
          for preset_name, preset_config in self._presets_dict.items():
              encrypted = (
                  preset_name
                  in self.config.encryption_enabled_by_default_for_room_presets
              )
              preset_config["encrypted"] = encrypted
  
          self._replication = hs.get_replication_data_handler()
  
          # linearizer to stop two upgrades happening at once
          self._upgrade_linearizer = Linearizer("room_upgrade_linearizer")
  
          # If a user tries to update the same room multiple times in quick
          # succession, only process the first attempt and return its result to
          # subsequent requests
          self._upgrade_response_cache = ResponseCache(
              hs.get_clock(), "room_upgrade", timeout_ms=FIVE_MINUTES_IN_MS
          )  # type: ResponseCache[Tuple[str, str]]
          self._server_notices_mxid = hs.config.server_notices_mxid
  
          self.third_party_event_rules = hs.get_third_party_event_rules()
  
      async def upgrade_room(
          self, requester: Requester, old_room_id: str, new_version: RoomVersion
      ) -> str:
          """Replace a room with a new room with a different version
  
          Args:
              requester: the user requesting the upgrade
              old_room_id: the id of the room to be replaced
              new_version: the new room version to use
  
          Returns:
              the new room id
  
          Raises:
              ShadowBanError if the requester is shadow-banned.
          """
          await self.ratelimit(requester)
  
          user_id = requester.user.to_string()
  
          # Check if this room is already being upgraded by another person
          for key in self._upgrade_response_cache.pending_result_cache:
              if key[0] == old_room_id and key[1] != user_id:
                  # Two different people are trying to upgrade the same room.
                  # Send the second an error.
                  #
                  # Note that this of course only gets caught if both users are
                  # on the same homeserver.
                  raise SynapseError(
                      400, "An upgrade for this room is currently in progress"
                  )
  
          # Upgrade the room
          #
          # If this user has sent multiple upgrade requests for the same room
          # and one of them is not complete yet, cache the response and
          # return it to all subsequent requests
          ret = await self._upgrade_response_cache.wrap(
              (old_room_id, user_id),
              self._upgrade_room,
              requester,
              old_room_id,
              new_version,  # args for _upgrade_room
          )
  
          return ret
  
      async def _upgrade_room(
          self, requester: Requester, old_room_id: str, new_version: RoomVersion
      ):
          """
          Args:
              requester: the user requesting the upgrade
              old_room_id: the id of the room to be replaced
              new_versions: the version to upgrade the room to
  
          Raises:
              ShadowBanError if the requester is shadow-banned.
          """
          user_id = requester.user.to_string()
          assert self.hs.is_mine_id(user_id), "User must be our own: %s" % (user_id,)
  
          # start by allocating a new room id
          r = await self.store.get_room(old_room_id)
          if r is None:
              raise NotFoundError("Unknown room id %s" % (old_room_id,))
          new_room_id = await self._generate_room_id(
              creator_id=user_id,
              is_public=r["is_public"],
              room_version=new_version,
          )
  
          logger.info("Creating new room %s to replace %s", new_room_id, old_room_id)
  
          # we create and auth the tombstone event before properly creating the new
          # room, to check our user has perms in the old room.
          (
              tombstone_event,
              tombstone_context,
          ) = await self.event_creation_handler.create_event(
              requester,
              {
                  "type": EventTypes.Tombstone,
                  "state_key": "",
                  "room_id": old_room_id,
                  "sender": user_id,
                  "content": {
                      "body": "This room has been replaced",
                      "replacement_room": new_room_id,
                  },
              },
          )
          old_room_version = await self.store.get_room_version_id(old_room_id)
          await self._event_auth_handler.check_from_context(
              old_room_version, tombstone_event, tombstone_context
          )
  
          await self.clone_existing_room(
              requester,
              old_room_id=old_room_id,
              new_room_id=new_room_id,
              new_room_version=new_version,
              tombstone_event_id=tombstone_event.event_id,
          )
  
          # now send the tombstone
          await self.event_creation_handler.handle_new_client_event(
              requester=requester,
              event=tombstone_event,
              context=tombstone_context,
          )
  
          old_room_state = await tombstone_context.get_current_state_ids()
  
          # We know the tombstone event isn't an outlier so it has current state.
          assert old_room_state is not None
  
          # update any aliases
          await self._move_aliases_to_new_room(
              requester, old_room_id, new_room_id, old_room_state
          )
  
          # Copy over user push rules, tags and migrate room directory state
          await self.room_member_handler.transfer_room_state_on_room_upgrade(
              old_room_id, new_room_id
          )
  
          # finally, shut down the PLs in the old room, and update them in the new
          # room.
          await self._update_upgraded_room_pls(
              requester,
              old_room_id,
              new_room_id,
              old_room_state,
          )
  
          return new_room_id
  
      async def _update_upgraded_room_pls(
          self,
          requester: Requester,
          old_room_id: str,
          new_room_id: str,
          old_room_state: StateMap[str],
      ) -> None:
          """Send updated power levels in both rooms after an upgrade
  
          Args:
              requester: the user requesting the upgrade
              old_room_id: the id of the room to be replaced
              new_room_id: the id of the replacement room
              old_room_state: the state map for the old room
  
          Raises:
              ShadowBanError if the requester is shadow-banned.
          """
          old_room_pl_event_id = old_room_state.get((EventTypes.PowerLevels, ""))
  
          if old_room_pl_event_id is None:
              logger.warning(
                  "Not supported: upgrading a room with no PL event. Not setting PLs "
                  "in old room."
              )
              return
  
          old_room_pl_state = await self.store.get_event(old_room_pl_event_id)
  
          # we try to stop regular users from speaking by setting the PL required
          # to send regular events and invites to 'Moderator' level. That's normally
          # 50, but if the default PL in a room is 50 or more, then we set the
          # required PL above that.
  
          pl_content = dict(old_room_pl_state.content)
          users_default = int(pl_content.get("users_default", 0))
          restricted_level = max(users_default + 1, 50)
  
          updated = False
          for v in ("invite", "events_default"):
              current = int(pl_content.get(v, 0))
              if current < restricted_level:
                  logger.debug(
                      "Setting level for %s in %s to %i (was %i)",
                      v,
                      old_room_id,
                      restricted_level,
                      current,
                  )
                  pl_content[v] = restricted_level
                  updated = True
              else:
                  logger.debug("Not setting level for %s (already %i)", v, current)
  
          if updated:
              try:
                  await self.event_creation_handler.create_and_send_nonmember_event(
                      requester,
                      {
                          "type": EventTypes.PowerLevels,
                          "state_key": "",
                          "room_id": old_room_id,
                          "sender": requester.user.to_string(),
                          "content": pl_content,
                      },
                      ratelimit=False,
                  )
              except AuthError as e:
                  logger.warning("Unable to update PLs in old room: %s", e)
  
          await self.event_creation_handler.create_and_send_nonmember_event(
              requester,
              {
                  "type": EventTypes.PowerLevels,
                  "state_key": "",
                  "room_id": new_room_id,
                  "sender": requester.user.to_string(),
                  "content": old_room_pl_state.content,
              },
              ratelimit=False,
          )
  
      async def clone_existing_room(
          self,
          requester: Requester,
          old_room_id: str,
          new_room_id: str,
          new_room_version: RoomVersion,
          tombstone_event_id: str,
      ) -> None:
          """Populate a new room based on an old room
  
          Args:
              requester: the user requesting the upgrade
              old_room_id : the id of the room to be replaced
              new_room_id: the id to give the new room (should already have been
                  created with _gemerate_room_id())
              new_room_version: the new room version to use
              tombstone_event_id: the ID of the tombstone event in the old room.
          """
          user_id = requester.user.to_string()
  
          if not await self.spam_checker.user_may_create_room(user_id):
              raise SynapseError(403, "You are not permitted to create rooms")
  
          creation_content = {
              "room_version": new_room_version.identifier,
              "predecessor": {"room_id": old_room_id, "event_id": tombstone_event_id},
          }  # type: JsonDict
  
          # Check if old room was non-federatable
  
          # Get old room's create event
          old_room_create_event = await self.store.get_create_event_for_room(old_room_id)
  
          # Check if the create event specified a non-federatable room
          if not old_room_create_event.content.get("m.federate", True):
              # If so, mark the new room as non-federatable as well
              creation_content["m.federate"] = False
  
          initial_state = {}
  
          # Replicate relevant room events
          types_to_copy = (
              (EventTypes.JoinRules, ""),
              (EventTypes.Name, ""),
              (EventTypes.Topic, ""),
              (EventTypes.RoomHistoryVisibility, ""),
              (EventTypes.GuestAccess, ""),
              (EventTypes.RoomAvatar, ""),
              (EventTypes.RoomEncryption, ""),
              (EventTypes.ServerACL, ""),
              (EventTypes.RelatedGroups, ""),
              (EventTypes.PowerLevels, ""),
          )
  
          old_room_state_ids = await self.store.get_filtered_current_state_ids(
              old_room_id, StateFilter.from_types(types_to_copy)
          )
          # map from event_id to BaseEvent
          old_room_state_events = await self.store.get_events(old_room_state_ids.values())
  
          for k, old_event_id in old_room_state_ids.items():
              old_event = old_room_state_events.get(old_event_id)
              if old_event:
                  initial_state[k] = old_event.content
  
          # deep-copy the power-levels event before we start modifying it
          # note that if frozen_dicts are enabled, `power_levels` will be a frozen
          # dict so we can't just copy.deepcopy it.
          initial_state[
              (EventTypes.PowerLevels, "")
          ] = power_levels = copy_power_levels_contents(
              initial_state[(EventTypes.PowerLevels, "")]
          )
  
          # Resolve the minimum power level required to send any state event
          # We will give the upgrading user this power level temporarily (if necessary) such that
          # they are able to copy all of the state events over, then revert them back to their
          # original power level afterwards in _update_upgraded_room_pls
  
          # Copy over user power levels now as this will not be possible with >100PL users once
          # the room has been created
          # Calculate the minimum power level needed to clone the room
          event_power_levels = power_levels.get("events", {})
          state_default = power_levels.get("state_default", 50)
          ban = power_levels.get("ban", 50)
          needed_power_level = max(state_default, ban, max(event_power_levels.values()))
  
          # Get the user's current power level, this matches the logic in get_user_power_level,
          # but without the entire state map.
          user_power_levels = power_levels.setdefault("users", {})
          users_default = power_levels.get("users_default", 0)
          current_power_level = user_power_levels.get(user_id, users_default)
          # Raise the requester's power level in the new room if necessary
          if current_power_level < needed_power_level:
              user_power_levels[user_id] = needed_power_level
  
          await self._send_events_for_new_room(
              requester,
              new_room_id,
              # we expect to override all the presets with initial_state, so this is
              # somewhat arbitrary.
              preset_config=RoomCreationPreset.PRIVATE_CHAT,
              invite_list=[],
              initial_state=initial_state,
              creation_content=creation_content,
              ratelimit=False,
          )
  
          # Transfer membership events
          old_room_member_state_ids = await self.store.get_filtered_current_state_ids(
              old_room_id, StateFilter.from_types([(EventTypes.Member, None)])
          )
  
          # map from event_id to BaseEvent
          old_room_member_state_events = await self.store.get_events(
              old_room_member_state_ids.values()
          )
          for old_event in old_room_member_state_events.values():
              # Only transfer ban events
              if (
                  "membership" in old_event.content
                  and old_event.content["membership"] == "ban"
              ):
                  await self.room_member_handler.update_membership(
                      requester,
                      UserID.from_string(old_event["state_key"]),
                      new_room_id,
                      "ban",
                      ratelimit=False,
                      content=old_event.content,
                  )
  
          # XXX invites/joins
          # XXX 3pid invites
  
      async def _move_aliases_to_new_room(
          self,
          requester: Requester,
          old_room_id: str,
          new_room_id: str,
          old_room_state: StateMap[str],
      ):
          # check to see if we have a canonical alias.
          canonical_alias_event = None
          canonical_alias_event_id = old_room_state.get((EventTypes.CanonicalAlias, ""))
          if canonical_alias_event_id:
              canonical_alias_event = await self.store.get_event(canonical_alias_event_id)
  
          await self.store.update_aliases_for_room(old_room_id, new_room_id)
  
          if not canonical_alias_event:
              return
  
          # If there is a canonical alias we need to update the one in the old
          # room and set one in the new one.
          old_canonical_alias_content = dict(canonical_alias_event.content)
          new_canonical_alias_content = {}
  
          canonical = canonical_alias_event.content.get("alias")
          if canonical and self.hs.is_mine_id(canonical):
              new_canonical_alias_content["alias"] = canonical
              old_canonical_alias_content.pop("alias", None)
  
          # We convert to a list as it will be a Tuple.
          old_alt_aliases = list(old_canonical_alias_content.get("alt_aliases", []))
          if old_alt_aliases:
              old_canonical_alias_content["alt_aliases"] = old_alt_aliases
              new_alt_aliases = new_canonical_alias_content.setdefault("alt_aliases", [])
              for alias in canonical_alias_event.content.get("alt_aliases", []):
                  try:
                      if self.hs.is_mine_id(alias):
                          new_alt_aliases.append(alias)
                          old_alt_aliases.remove(alias)
                  except Exception:
                      logger.info(
                          "Invalid alias %s in canonical alias event %s",
                          alias,
                          canonical_alias_event_id,
                      )
  
              if not old_alt_aliases:
                  old_canonical_alias_content.pop("alt_aliases")
  
          # If a canonical alias event existed for the old room, fire a canonical
          # alias event for the new room with a copy of the information.
          try:
              await self.event_creation_handler.create_and_send_nonmember_event(
                  requester,
                  {
                      "type": EventTypes.CanonicalAlias,
                      "state_key": "",
                      "room_id": old_room_id,
                      "sender": requester.user.to_string(),
                      "content": old_canonical_alias_content,
                  },
                  ratelimit=False,
              )
          except SynapseError as e:
              # again I'm not really expecting this to fail, but if it does, I'd rather
              # we returned the new room to the client at this point.
              logger.error("Unable to send updated alias events in old room: %s", e)
  
          try:
              await self.event_creation_handler.create_and_send_nonmember_event(
                  requester,
                  {
                      "type": EventTypes.CanonicalAlias,
                      "state_key": "",
                      "room_id": new_room_id,
                      "sender": requester.user.to_string(),
                      "content": new_canonical_alias_content,
                  },
                  ratelimit=False,
              )
          except SynapseError as e:
              # again I'm not really expecting this to fail, but if it does, I'd rather
              # we returned the new room to the client at this point.
              logger.error("Unable to send updated alias events in new room: %s", e)
  
      async def create_room(
          self,
          requester: Requester,
          config: JsonDict,
          ratelimit: bool = True,
          creator_join_profile: Optional[JsonDict] = None,
      ) -> Tuple[dict, int]:
          """Creates a new room.
  
          Args:
              requester:
                  The user who requested the room creation.
              config : A dict of configuration options.
              ratelimit: set to False to disable the rate limiter
  
              creator_join_profile:
                  Set to override the displayname and avatar for the creating
                  user in this room. If unset, displayname and avatar will be
                  derived from the user's profile. If set, should contain the
                  values to go in the body of the 'join' event (typically
                  `avatar_url` and/or `displayname`.
  
          Returns:
                  First, a dict containing the keys `room_id` and, if an alias
                  was, requested, `room_alias`. Secondly, the stream_id of the
                  last persisted event.
          Raises:
              SynapseError if the room ID couldn't be stored, or something went
              horribly wrong.
              ResourceLimitError if server is blocked to some resource being
              exceeded
          """
          user_id = requester.user.to_string()
  
          await self.auth.check_auth_blocking(requester=requester)
  
          if (
              self._server_notices_mxid is not None
              and requester.user.to_string() == self._server_notices_mxid
          ):
              # allow the server notices mxid to create rooms
              is_requester_admin = True
          else:
              is_requester_admin = await self.auth.is_server_admin(requester.user)
  
          # Check whether the third party rules allows/changes the room create
          # request.
          event_allowed = await self.third_party_event_rules.on_create_room(
              requester, config, is_requester_admin=is_requester_admin
          )
          if not event_allowed:
              raise SynapseError(
                  403, "You are not permitted to create rooms", Codes.FORBIDDEN
              )
  
          if not is_requester_admin and not await self.spam_checker.user_may_create_room(
              user_id
          ):
              raise SynapseError(403, "You are not permitted to create rooms")
  
          if ratelimit:
              await self.ratelimit(requester)
  
          room_version_id = config.get(
              "room_version", self.config.default_room_version.identifier
          )
  
          if not isinstance(room_version_id, str):
              raise SynapseError(400, "room_version must be a string", Codes.BAD_JSON)
  
          room_version = KNOWN_ROOM_VERSIONS.get(room_version_id)
          if room_version is None:
              raise SynapseError(
                  400,
                  "Your homeserver does not support this room version",
                  Codes.UNSUPPORTED_ROOM_VERSION,
              )
  
          room_alias = None
          if "room_alias_name" in config:
              for wchar in string.whitespace:
                  if wchar in config["room_alias_name"]:
                      raise SynapseError(400, "Invalid characters in room alias")
  
              room_alias = RoomAlias(config["room_alias_name"], self.hs.hostname)
              mapping = await self.store.get_association_from_room_alias(room_alias)
  
              if mapping:
                  raise SynapseError(400, "Room alias already taken", Codes.ROOM_IN_USE)
  
          invite_3pid_list = config.get("invite_3pid", [])
          invite_list = config.get("invite", [])
          for i in invite_list:
              try:
                  uid = UserID.from_string(i)
                  parse_and_validate_server_name(uid.domain)
              except Exception:
                  raise SynapseError(400, "Invalid user_id: %s" % (i,))
  
          if (invite_list or invite_3pid_list) and requester.shadow_banned:
              # We randomly sleep a bit just to annoy the requester.
              await self.clock.sleep(random.randint(1, 10))
  
              # Allow the request to go through, but remove any associated invites.
              invite_3pid_list = []
              invite_list = []
  
          if invite_list or invite_3pid_list:
              try:
                  # If there are invites in the request, see if the ratelimiting settings
                  # allow that number of invites to be sent from the current user.
                  await self.room_member_handler.ratelimit_multiple_invites(
                      requester,
                      room_id=None,
                      n_invites=len(invite_list) + len(invite_3pid_list),
                      update=False,
                  )
              except LimitExceededError:
                  raise SynapseError(400, "Cannot invite so many users at once")
  
          await self.event_creation_handler.assert_accepted_privacy_policy(requester)
  
          power_level_content_override = config.get("power_level_content_override")
          if (
              power_level_content_override
              and "users" in power_level_content_override
              and user_id not in power_level_content_override["users"]
          ):
              raise SynapseError(
                  400,
                  "Not a valid power_level_content_override: 'users' did not contain %s"
                  % (user_id,),
              )
  
          visibility = config.get("visibility", None)
          is_public = visibility == "public"
  
          room_id = await self._generate_room_id(
              creator_id=user_id,
              is_public=is_public,
              room_version=room_version,
          )
  
          # Check whether this visibility value is blocked by a third party module
          allowed_by_third_party_rules = await (
              self.third_party_event_rules.check_visibility_can_be_modified(
                  room_id, visibility
              )
          )
          if not allowed_by_third_party_rules:
              raise SynapseError(403, "Room visibility value not allowed.")
  
          directory_handler = self.hs.get_directory_handler()
          if room_alias:
              await directory_handler.create_association(
                  requester=requester,
                  room_id=room_id,
                  room_alias=room_alias,
                  servers=[self.hs.hostname],
                  check_membership=False,
              )
  
          if is_public:
              if not self.config.is_publishing_room_allowed(user_id, room_id, room_alias):
                  # Lets just return a generic message, as there may be all sorts of
                  # reasons why we said no. TODO: Allow configurable error messages
                  # per alias creation rule?
                  raise SynapseError(403, "Not allowed to publish room")
  
          preset_config = config.get(
              "preset",
              RoomCreationPreset.PRIVATE_CHAT
              if visibility == "private"
              else RoomCreationPreset.PUBLIC_CHAT,
          )
  
          raw_initial_state = config.get("initial_state", [])
  
          initial_state = OrderedDict()
          for val in raw_initial_state:
              initial_state[(val["type"], val.get("state_key", ""))] = val["content"]
  
          creation_content = config.get("creation_content", {})
  
          # override any attempt to set room versions via the creation_content
          creation_content["room_version"] = room_version.identifier
  
          last_stream_id = await self._send_events_for_new_room(
              requester,
              room_id,
              preset_config=preset_config,
              invite_list=invite_list,
              initial_state=initial_state,
              creation_content=creation_content,
              room_alias=room_alias,
              power_level_content_override=power_level_content_override,
              creator_join_profile=creator_join_profile,
              ratelimit=ratelimit,
          )
  
          if "name" in config:
              name = config["name"]
              (
                  _,
                  last_stream_id,
              ) = await self.event_creation_handler.create_and_send_nonmember_event(
                  requester,
                  {
                      "type": EventTypes.Name,
                      "room_id": room_id,
                      "sender": user_id,
                      "state_key": "",
                      "content": {"name": name},
                  },
                  ratelimit=False,
              )
  
          if "topic" in config:
              topic = config["topic"]
              (
                  _,
                  last_stream_id,
              ) = await self.event_creation_handler.create_and_send_nonmember_event(
                  requester,
                  {
                      "type": EventTypes.Topic,
                      "room_id": room_id,
                      "sender": user_id,
                      "state_key": "",
                      "content": {"topic": topic},
                  },
                  ratelimit=False,
              )
  
          # we avoid dropping the lock between invites, as otherwise joins can
          # start coming in and making the createRoom slow.
          #
          # we also don't need to check the requester's shadow-ban here, as we
          # have already done so above (and potentially emptied invite_list).
          with (await self.room_member_handler.member_linearizer.queue((room_id,))):
              content = {}
              is_direct = config.get("is_direct", None)
              if is_direct:
                  content["is_direct"] = is_direct
  
              for invitee in invite_list:
                  (
                      _,
                      last_stream_id,
                  ) = await self.room_member_handler.update_membership_locked(
                      requester,
                      UserID.from_string(invitee),
                      room_id,
                      "invite",
                      ratelimit=False,
                      content=content,
                  )
  
          for invite_3pid in invite_3pid_list:
              id_server = invite_3pid["id_server"]
              id_access_token = invite_3pid.get("id_access_token")  # optional
              address = invite_3pid["address"]
              medium = invite_3pid["medium"]
              # Note that do_3pid_invite can raise a  ShadowBanError, but this was
              # handled above by emptying invite_3pid_list.
              last_stream_id = await self.hs.get_room_member_handler().do_3pid_invite(
                  room_id,
                  requester.user,
                  medium,
                  address,
                  id_server,
                  requester,
                  txn_id=None,
                  id_access_token=id_access_token,
              )
  
          result = {"room_id": room_id}
  
          if room_alias:
              result["room_alias"] = room_alias.to_string()
  
          # Always wait for room creation to propagate before returning
          await self._replication.wait_for_stream_position(
              self.hs.config.worker.events_shard_config.get_instance(room_id),
              "events",
              last_stream_id,
          )
  
          return result, last_stream_id
  
      async def _send_events_for_new_room(
          self,
          creator: Requester,
          room_id: str,
          preset_config: str,
          invite_list: List[str],
          initial_state: MutableStateMap,
          creation_content: JsonDict,
          room_alias: Optional[RoomAlias] = None,
          power_level_content_override: Optional[JsonDict] = None,
          creator_join_profile: Optional[JsonDict] = None,
          ratelimit: bool = True,
      ) -> int:
          """Sends the initial events into a new room.
  
          `power_level_content_override` doesn't apply when initial state has
          power level state event content.
  
          Returns:
              The stream_id of the last event persisted.
          """
  
          creator_id = creator.user.to_string()
  
          event_keys = {"room_id": room_id, "sender": creator_id, "state_key": ""}
  
          def create(etype: str, content: JsonDict, **kwargs) -> JsonDict:
              e = {"type": etype, "content": content}
  
              e.update(event_keys)
              e.update(kwargs)
  
              return e
  
          async def send(etype: str, content: JsonDict, **kwargs) -> int:
              event = create(etype, content, **kwargs)
              logger.debug("Sending %s in new room", etype)
              # Allow these events to be sent even if the user is shadow-banned to
              # allow the room creation to complete.
              (
                  _,
                  last_stream_id,
              ) = await self.event_creation_handler.create_and_send_nonmember_event(
                  creator,
                  event,
                  ratelimit=False,
                  ignore_shadow_ban=True,
              )
              return last_stream_id
  
          config = self._presets_dict[preset_config]
  
          creation_content.update({"creator": creator_id})
          await send(etype=EventTypes.Create, content=creation_content)
  
          logger.debug("Sending %s in new room", EventTypes.Member)
          await self.room_member_handler.update_membership(
              creator,
              creator.user,
              room_id,
              "join",
              ratelimit=ratelimit,
              content=creator_join_profile,
          )
  
          # We treat the power levels override specially as this needs to be one
          # of the first events that get sent into a room.
          pl_content = initial_state.pop((EventTypes.PowerLevels, ""), None)
          if pl_content is not None:
              last_sent_stream_id = await send(
                  etype=EventTypes.PowerLevels, content=pl_content
              )
          else:
              power_level_content = {
                  "users": {creator_id: 100},
                  "users_default": 0,
                  "events": {
                      EventTypes.Name: 50,
                      EventTypes.PowerLevels: 100,
                      EventTypes.RoomHistoryVisibility: 100,
                      EventTypes.CanonicalAlias: 50,
                      EventTypes.RoomAvatar: 50,
                      EventTypes.Tombstone: 100,
                      EventTypes.ServerACL: 100,
                      EventTypes.RoomEncryption: 100,
                  },
                  "events_default": 0,
                  "state_default": 50,
                  "ban": 50,
                  "kick": 50,
                  "redact": 50,
                  "invite": 50,
              }  # type: JsonDict
  
              if config["original_invitees_have_ops"]:
                  for invitee in invite_list:
                      power_level_content["users"][invitee] = 100
  
              # Power levels overrides are defined per chat preset
              power_level_content.update(config["power_level_content_override"])
  
              if power_level_content_override:
                  power_level_content.update(power_level_content_override)
  
              last_sent_stream_id = await send(
                  etype=EventTypes.PowerLevels, content=power_level_content
              )
  
          if room_alias and (EventTypes.CanonicalAlias, "") not in initial_state:
              last_sent_stream_id = await send(
                  etype=EventTypes.CanonicalAlias,
                  content={"alias": room_alias.to_string()},
              )
  
          if (EventTypes.JoinRules, "") not in initial_state:
              last_sent_stream_id = await send(
                  etype=EventTypes.JoinRules, content={"join_rule": config["join_rules"]}
              )
  
          if (EventTypes.RoomHistoryVisibility, "") not in initial_state:
              last_sent_stream_id = await send(
                  etype=EventTypes.RoomHistoryVisibility,
                  content={"history_visibility": config["history_visibility"]},
              )
  
          if config["guest_can_join"]:
              if (EventTypes.GuestAccess, "") not in initial_state:
                  last_sent_stream_id = await send(
                      etype=EventTypes.GuestAccess, content={"guest_access": "can_join"}
                  )
  
          for (etype, state_key), content in initial_state.items():
              last_sent_stream_id = await send(
                  etype=etype, state_key=state_key, content=content
              )
  
          if config["encrypted"]:
              last_sent_stream_id = await send(
                  etype=EventTypes.RoomEncryption,
                  state_key="",
                  content={"algorithm": RoomEncryptionAlgorithms.DEFAULT},
              )
  
          return last_sent_stream_id
  
      async def _generate_room_id(
          self,
          creator_id: str,
          is_public: bool,
          room_version: RoomVersion,
      ):
          # autogen room IDs and try to create it. We may clash, so just
          # try a few times till one goes through, giving up eventually.
          attempts = 0
          while attempts < 5:
              try:
                  random_string = stringutils.random_string(18)
                  gen_room_id = RoomID(random_string, self.hs.hostname).to_string()
                  await self.store.store_room(
                      room_id=gen_room_id,
                      room_creator_user_id=creator_id,
                      is_public=is_public,
                      room_version=room_version,
                  )
                  return gen_room_id
              except StoreError:
                  attempts += 1
          raise StoreError(500, "Couldn't generate a room ID.")
  
  
  class RoomContextHandler:
      def __init__(self, hs: "HomeServer"):
          self.hs = hs
          self.auth = hs.get_auth()
          self.store = hs.get_datastore()
          self.storage = hs.get_storage()
          self.state_store = self.storage.state
  
      async def get_event_context(
          self,
          requester: Requester,
          room_id: str,
          event_id: str,
          limit: int,
          event_filter: Optional[Filter],
          use_admin_priviledge: bool = False,
      ) -> Optional[JsonDict]:
          """Retrieves events, pagination tokens and state around a given event
          in a room.
  
          Args:
              requester
              room_id
              event_id
              limit: The maximum number of events to return in total
                  (excluding state).
              event_filter: the filter to apply to the events returned
                  (excluding the target event_id)
              use_admin_priviledge: if `True`, return all events, regardless
                  of whether `user` has access to them. To be used **ONLY**
                  from the admin API.
          Returns:
              dict, or None if the event isn't found
          """
          user = requester.user
          if use_admin_priviledge:
              await assert_user_is_admin(self.auth, requester.user)
  
          before_limit = math.floor(limit / 2.0)
          after_limit = limit - before_limit
  
          users = await self.store.get_users_in_room(room_id)
          is_peeking = user.to_string() not in users
  
          async def filter_evts(events):
              if use_admin_priviledge:
                  return events
              return await filter_events_for_client(
                  self.storage, user.to_string(), events, is_peeking=is_peeking
              )
  
          event = await self.store.get_event(
              event_id, get_prev_content=True, allow_none=True
          )
          if not event:
              return None
  
          filtered = await filter_evts([event])
          if not filtered:
              raise AuthError(403, "You don't have permission to access that event.")
  
          results = await self.store.get_events_around(
              room_id, event_id, before_limit, after_limit, event_filter
          )
  
          if event_filter:
              results["events_before"] = event_filter.filter(results["events_before"])
              results["events_after"] = event_filter.filter(results["events_after"])
  
          results["events_before"] = await filter_evts(results["events_before"])
          results["events_after"] = await filter_evts(results["events_after"])
          # filter_evts can return a pruned event in case the user is allowed to see that
          # there's something there but not see the content, so use the event that's in
          # `filtered` rather than the event we retrieved from the datastore.
          results["event"] = filtered[0]
  
          if results["events_after"]:
              last_event_id = results["events_after"][-1].event_id
          else:
              last_event_id = event_id
  
          if event_filter and event_filter.lazy_load_members():
              state_filter = StateFilter.from_lazy_load_member_list(
                  ev.sender
                  for ev in itertools.chain(
                      results["events_before"],
                      (results["event"],),
                      results["events_after"],
                  )
              )
          else:
              state_filter = StateFilter.all()
  
          # XXX: why do we return the state as of the last event rather than the
          # first? Shouldn't we be consistent with /sync?
          # https://github.com/matrix-org/matrix-doc/issues/687
  
          state = await self.state_store.get_state_for_events(
              [last_event_id], state_filter=state_filter
          )
  
          state_events = list(state[last_event_id].values())
          if event_filter:
              state_events = event_filter.filter(state_events)
  
          results["state"] = await filter_evts(state_events)
  
          # We use a dummy token here as we only care about the room portion of
          # the token, which we replace.
          token = StreamToken.START
  
          results["start"] = await token.copy_and_replace(
              "room_key", results["start"]
          ).to_string(self.store)
  
          results["end"] = await token.copy_and_replace(
              "room_key", results["end"]
          ).to_string(self.store)
  
          return results
  
  
  class RoomEventSource:
      def __init__(self, hs: "HomeServer"):
          self.store = hs.get_datastore()
  
      async def get_new_events(
          self,
          user: UserID,
          from_key: RoomStreamToken,
          limit: int,
          room_ids: List[str],
          is_guest: bool,
          explicit_room_id: Optional[str] = None,
      ) -> Tuple[List[EventBase], RoomStreamToken]:
          # We just ignore the key for now.
  
          to_key = self.get_current_key()
  
          if from_key.topological:
              logger.warning("Stream has topological part!!!! %r", from_key)
              from_key = RoomStreamToken(None, from_key.stream)
  
          app_service = self.store.get_app_service_by_user_id(user.to_string())
          if app_service:
              # We no longer support AS users using /sync directly.
              # See https://github.com/matrix-org/matrix-doc/issues/1144
              raise NotImplementedError()
          else:
              room_events = await self.store.get_membership_changes_for_user(
                  user.to_string(), from_key, to_key
              )
  
              room_to_events = await self.store.get_room_events_stream_for_rooms(
                  room_ids=room_ids,
                  from_key=from_key,
                  to_key=to_key,
                  limit=limit or 10,
                  order="ASC",
              )
  
              events = list(room_events)
              events.extend(e for evs, _ in room_to_events.values() for e in evs)
  
              events.sort(key=lambda e: e.internal_metadata.order)
  
              if limit:
                  events[:] = events[:limit]
  
              if events:
                  end_key = events[-1].internal_metadata.after
              else:
                  end_key = to_key
  
          return (events, end_key)
  
      def get_current_key(self) -> RoomStreamToken:
          return self.store.get_room_max_token()
  
      def get_current_key_for_room(self, room_id: str) -> Awaitable[str]:
          return self.store.get_room_events_max_id(room_id)
  
  
  class RoomShutdownHandler:
  
      DEFAULT_MESSAGE = (
          "Sharing illegal content on this server is not permitted and rooms in"
          " violation will be blocked."
      )
      DEFAULT_ROOM_NAME = "Content Violation Notification"
  
      def __init__(self, hs: "HomeServer"):
          self.hs = hs
          self.room_member_handler = hs.get_room_member_handler()
          self._room_creation_handler = hs.get_room_creation_handler()
          self._replication = hs.get_replication_data_handler()
          self.event_creation_handler = hs.get_event_creation_handler()
          self.state = hs.get_state_handler()
          self.store = hs.get_datastore()
  
      async def shutdown_room(
          self,
          room_id: str,
          requester_user_id: str,
          new_room_user_id: Optional[str] = None,
          new_room_name: Optional[str] = None,
          message: Optional[str] = None,
          block: bool = False,
      ) -> dict:
          """
          Shuts down a room. Moves all local users and room aliases automatically
          to a new room if `new_room_user_id` is set. Otherwise local users only
          leave the room without any information.
  
          The new room will be created with the user specified by the
          `new_room_user_id` parameter as room administrator and will contain a
          message explaining what happened. Users invited to the new room will
          have power level `-10` by default, and thus be unable to speak.
  
          The local server will only have the power to move local user and room
          aliases to the new room. Users on other servers will be unaffected.
  
          Args:
              room_id: The ID of the room to shut down.
              requester_user_id:
                  User who requested the action and put the room on the
                  blocking list.
              new_room_user_id:
                  If set, a new room will be created with this user ID
                  as the creator and admin, and all users in the old room will be
                  moved into that room. If not set, no new room will be created
                  and the users will just be removed from the old room.
              new_room_name:
                  A string representing the name of the room that new users will
                  be invited to. Defaults to `Content Violation Notification`
              message:
                  A string containing the first message that will be sent as
                  `new_room_user_id` in the new room. Ideally this will clearly
                  convey why the original room was shut down.
                  Defaults to `Sharing illegal content on this server is not
                  permitted and rooms in violation will be blocked.`
              block:
                  If set to `true`, this room will be added to a blocking list,
                  preventing future attempts to join the room. Defaults to `false`.
  
          Returns: a dict containing the following keys:
              kicked_users: An array of users (`user_id`) that were kicked.
              failed_to_kick_users:
                  An array of users (`user_id`) that that were not kicked.
              local_aliases:
                  An array of strings representing the local aliases that were
                  migrated from the old room to the new.
              new_room_id: A string representing the room ID of the new room.
          """
  
          if not new_room_name:
              new_room_name = self.DEFAULT_ROOM_NAME
          if not message:
              message = self.DEFAULT_MESSAGE
  
          if not RoomID.is_valid(room_id):
              raise SynapseError(400, "%s is not a legal room ID" % (room_id,))
  
          if not await self.store.get_room(room_id):
              raise NotFoundError("Unknown room id %s" % (room_id,))
  
          # This will work even if the room is already blocked, but that is
          # desirable in case the first attempt at blocking the room failed below.
          if block:
              await self.store.block_room(room_id, requester_user_id)
  
          if new_room_user_id is not None:
              if not self.hs.is_mine_id(new_room_user_id):
                  raise SynapseError(
                      400, "User must be our own: %s" % (new_room_user_id,)
                  )
  
              room_creator_requester = create_requester(
                  new_room_user_id, authenticated_entity=requester_user_id
              )
  
              info, stream_id = await self._room_creation_handler.create_room(
                  room_creator_requester,
                  config={
                      "preset": RoomCreationPreset.PUBLIC_CHAT,
                      "name": new_room_name,
                      "power_level_content_override": {"users_default": -10},
                  },
                  ratelimit=False,
              )
              new_room_id = info["room_id"]
  
              logger.info(
                  "Shutting down room %r, joining to new room: %r", room_id, new_room_id
              )
  
              # We now wait for the create room to come back in via replication so
              # that we can assume that all the joins/invites have propagated before
              # we try and auto join below.
              await self._replication.wait_for_stream_position(
                  self.hs.config.worker.events_shard_config.get_instance(new_room_id),
                  "events",
                  stream_id,
              )
          else:
              new_room_id = None
              logger.info("Shutting down room %r", room_id)
  
          users = await self.store.get_users_in_room(room_id)
          kicked_users = []
          failed_to_kick_users = []
          for user_id in users:
              if not self.hs.is_mine_id(user_id):
                  continue
  
              logger.info("Kicking %r from %r...", user_id, room_id)
  
              try:
                  # Kick users from room
                  target_requester = create_requester(
                      user_id, authenticated_entity=requester_user_id
                  )
                  _, stream_id = await self.room_member_handler.update_membership(
                      requester=target_requester,
                      target=target_requester.user,
                      room_id=room_id,
                      action=Membership.LEAVE,
                      content={},
                      ratelimit=False,
                      require_consent=False,
                  )
  
                  # Wait for leave to come in over replication before trying to forget.
                  await self._replication.wait_for_stream_position(
                      self.hs.config.worker.events_shard_config.get_instance(room_id),
                      "events",
                      stream_id,
                  )
  
                  await self.room_member_handler.forget(target_requester.user, room_id)
  
                  # Join users to new room
                  if new_room_user_id:
                      await self.room_member_handler.update_membership(
                          requester=target_requester,
                          target=target_requester.user,
                          room_id=new_room_id,
                          action=Membership.JOIN,
                          content={},
                          ratelimit=False,
                          require_consent=False,
                      )
  
                  kicked_users.append(user_id)
              except Exception:
                  logger.exception(
                      "Failed to leave old room and join new room for %r", user_id
                  )
                  failed_to_kick_users.append(user_id)
  
          # Send message in new room and move aliases
          if new_room_user_id:
              await self.event_creation_handler.create_and_send_nonmember_event(
                  room_creator_requester,
                  {
                      "type": "m.room.message",
                      "content": {"body": message, "msgtype": "m.text"},
                      "room_id": new_room_id,
                      "sender": new_room_user_id,
                  },
                  ratelimit=False,
              )
  
              aliases_for_room = await self.store.get_aliases_for_room(room_id)
  
              await self.store.update_aliases_for_room(
                  room_id, new_room_id, requester_user_id
              )
          else:
              aliases_for_room = []
  
          return {
              "kicked_users": kicked_users,
              "failed_to_kick_users": failed_to_kick_users,
              "local_aliases": aliases_for_room,
              "new_room_id": new_room_id,
          }
  