text: # -*- coding: utf-8 -*-
  # 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.
  
  from __future__ import division
  
  import itertools
  import logging
  from collections import namedtuple
  
  from canonicaljson import json
  
  from twisted.internet import defer
  
  from synapse.api.constants import EventTypes
  from synapse.api.errors import NotFoundError
  from synapse.api.room_versions import EventFormatVersions
  from synapse.events import FrozenEvent, event_type_from_format_version  # noqa: F401
  from synapse.events.snapshot import EventContext  # noqa: F401
  from synapse.events.utils import prune_event
  from synapse.logging.context import LoggingContext, PreserveLoggingContext
  from synapse.metrics.background_process_metrics import run_as_background_process
  from synapse.types import get_domain_from_id
  from synapse.util import batch_iter
  from synapse.util.metrics import Measure
  
  from ._base import SQLBaseStore
  
  logger = logging.getLogger(__name__)
  
  
  # These values are used in the `enqueus_event` and `_do_fetch` methods to
  # control how we batch/bulk fetch events from the database.
  # The values are plucked out of thing air to make initial sync run faster
  # on jki.re
  # TODO: Make these configurable.
  EVENT_QUEUE_THREADS = 3  # Max number of threads that will fetch events
  EVENT_QUEUE_ITERATIONS = 3  # No. times we block waiting for requests for events
  EVENT_QUEUE_TIMEOUT_S = 0.1  # Timeout when waiting for requests for events
  
  
  _EventCacheEntry = namedtuple("_EventCacheEntry", ("event", "redacted_event"))
  
  
  class EventsWorkerStore(SQLBaseStore):
      def get_received_ts(self, event_id):
          """Get received_ts (when it was persisted) for the event.
  
          Raises an exception for unknown events.
  
          Args:
              event_id (str)
  
          Returns:
              Deferred[int|None]: Timestamp in milliseconds, or None for events
              that were persisted before received_ts was implemented.
          """
          return self._simple_select_one_onecol(
              table="events",
              keyvalues={"event_id": event_id},
              retcol="received_ts",
              desc="get_received_ts",
          )
  
      def get_received_ts_by_stream_pos(self, stream_ordering):
          """Given a stream ordering get an approximate timestamp of when it
          happened.
  
          This is done by simply taking the received ts of the first event that
          has a stream ordering greater than or equal to the given stream pos.
          If none exists returns the current time, on the assumption that it must
          have happened recently.
  
          Args:
              stream_ordering (int)
  
          Returns:
              Deferred[int]
          """
  
          def _get_approximate_received_ts_txn(txn):
              sql = """
                  SELECT received_ts FROM events
                  WHERE stream_ordering >= ?
                  LIMIT 1
              """
  
              txn.execute(sql, (stream_ordering,))
              row = txn.fetchone()
              if row and row[0]:
                  ts = row[0]
              else:
                  ts = self.clock.time_msec()
  
              return ts
  
          return self.runInteraction(
              "get_approximate_received_ts", _get_approximate_received_ts_txn
          )
  
      @defer.inlineCallbacks
      def get_event(
          self,
          event_id,
          check_redacted=True,
          get_prev_content=False,
          allow_rejected=False,
          allow_none=False,
          check_room_id=None,
      ):
          """Get an event from the database by event_id.
  
          Args:
              event_id (str): The event_id of the event to fetch
              check_redacted (bool): If True, check if event has been redacted
                  and redact it.
              get_prev_content (bool): If True and event is a state event,
                  include the previous states content in the unsigned field.
              allow_rejected (bool): If True return rejected events.
              allow_none (bool): If True, return None if no event found, if
                  False throw a NotFoundError
              check_room_id (str|None): if not None, check the room of the found event.
                  If there is a mismatch, behave as per allow_none.
  
          Returns:
              Deferred[EventBase|None]
          """
          if not isinstance(event_id, str):
              raise TypeError("Invalid event event_id %r" % (event_id,))
  
          events = yield self.get_events_as_list(
              [event_id],
              check_redacted=check_redacted,
              get_prev_content=get_prev_content,
              allow_rejected=allow_rejected,
          )
  
          event = events[0] if events else None
  
          if event is not None and check_room_id is not None:
              if event.room_id != check_room_id:
                  event = None
  
          if event is None and not allow_none:
              raise NotFoundError("Could not find event %s" % (event_id,))
  
          return event
  
      @defer.inlineCallbacks
      def get_events(
          self,
          event_ids,
          check_redacted=True,
          get_prev_content=False,
          allow_rejected=False,
      ):
          """Get events from the database
  
          Args:
              event_ids (list): The event_ids of the events to fetch
              check_redacted (bool): If True, check if event has been redacted
                  and redact it.
              get_prev_content (bool): If True and event is a state event,
                  include the previous states content in the unsigned field.
              allow_rejected (bool): If True return rejected events.
  
          Returns:
              Deferred : Dict from event_id to event.
          """
          events = yield self.get_events_as_list(
              event_ids,
              check_redacted=check_redacted,
              get_prev_content=get_prev_content,
              allow_rejected=allow_rejected,
          )
  
          return {e.event_id: e for e in events}
  
      @defer.inlineCallbacks
      def get_events_as_list(
          self,
          event_ids,
          check_redacted=True,
          get_prev_content=False,
          allow_rejected=False,
      ):
          """Get events from the database and return in a list in the same order
          as given by `event_ids` arg.
  
          Args:
              event_ids (list): The event_ids of the events to fetch
              check_redacted (bool): If True, check if event has been redacted
                  and redact it.
              get_prev_content (bool): If True and event is a state event,
                  include the previous states content in the unsigned field.
              allow_rejected (bool): If True return rejected events.
  
          Returns:
              Deferred[list[EventBase]]: List of events fetched from the database. The
              events are in the same order as `event_ids` arg.
  
              Note that the returned list may be smaller than the list of event
              IDs if not all events could be fetched.
          """
  
          if not event_ids:
              return []
  
          # there may be duplicates so we cast the list to a set
          event_entry_map = yield self._get_events_from_cache_or_db(
              set(event_ids), allow_rejected=allow_rejected
          )
  
          events = []
          for event_id in event_ids:
              entry = event_entry_map.get(event_id, None)
              if not entry:
                  continue
  
              if not allow_rejected:
                  assert not entry.event.rejected_reason, (
                      "rejected event returned from _get_events_from_cache_or_db despite "
                      "allow_rejected=False"
                  )
  
              # We may not have had the original event when we received a redaction, so
              # we have to recheck auth now.
  
              if not allow_rejected and entry.event.type == EventTypes.Redaction:
                  if not hasattr(entry.event, "redacts"):
                      # A redacted redaction doesn't have a `redacts` key, in
                      # which case lets just withhold the event.
                      #
                      # Note: Most of the time if the redactions has been
                      # redacted we still have the un-redacted event in the DB
                      # and so we'll still see the `redacts` key. However, this
                      # isn't always true e.g. if we have censored the event.
                      logger.debug(
                          "Withholding redaction event %s as we don't have redacts key",
                          event_id,
                      )
                      continue
  
                  redacted_event_id = entry.event.redacts
                  event_map = yield self._get_events_from_cache_or_db([redacted_event_id])
                  original_event_entry = event_map.get(redacted_event_id)
                  if not original_event_entry:
                      # we don't have the redacted event (or it was rejected).
                      #
                      # We assume that the redaction isn't authorized for now; if the
                      # redacted event later turns up, the redaction will be re-checked,
                      # and if it is found valid, the original will get redacted before it
                      # is served to the client.
                      logger.debug(
                          "Withholding redaction event %s since we don't (yet) have the "
                          "original %s",
                          event_id,
                          redacted_event_id,
                      )
                      continue
  
                  original_event = original_event_entry.event
                  if original_event.type == EventTypes.Create:
                      # we never serve redactions of Creates to clients.
                      logger.info(
                          "Withholding redaction %s of create event %s",
                          event_id,
                          redacted_event_id,
                      )
                      continue
  
                  if original_event.room_id != entry.event.room_id:
                      logger.info(
                          "Withholding redaction %s of event %s from a different room",
                          event_id,
                          redacted_event_id,
                      )
                      continue
  
                  if entry.event.internal_metadata.need_to_check_redaction():
                      original_domain = get_domain_from_id(original_event.sender)
                      redaction_domain = get_domain_from_id(entry.event.sender)
                      if original_domain != redaction_domain:
                          # the senders don't match, so this is forbidden
                          logger.info(
                              "Withholding redaction %s whose sender domain %s doesn't "
                              "match that of redacted event %s %s",
                              event_id,
                              redaction_domain,
                              redacted_event_id,
                              original_domain,
                          )
                          continue
  
                      # Update the cache to save doing the checks again.
                      entry.event.internal_metadata.recheck_redaction = False
  
              if check_redacted and entry.redacted_event:
                  event = entry.redacted_event
              else:
                  event = entry.event
  
              events.append(event)
  
              if get_prev_content:
                  if "replaces_state" in event.unsigned:
                      prev = yield self.get_event(
                          event.unsigned["replaces_state"],
                          get_prev_content=False,
                          allow_none=True,
                      )
                      if prev:
                          event.unsigned = dict(event.unsigned)
                          event.unsigned["prev_content"] = prev.content
                          event.unsigned["prev_sender"] = prev.sender
  
          return events
  
      @defer.inlineCallbacks
      def _get_events_from_cache_or_db(self, event_ids, allow_rejected=False):
          """Fetch a bunch of events from the cache or the database.
  
          If events are pulled from the database, they will be cached for future lookups.
  
          Args:
              event_ids (Iterable[str]): The event_ids of the events to fetch
              allow_rejected (bool): Whether to include rejected events
  
          Returns:
              Deferred[Dict[str, _EventCacheEntry]]:
                  map from event id to result
          """
          event_entry_map = self._get_events_from_cache(
              event_ids, allow_rejected=allow_rejected
          )
  
          missing_events_ids = [e for e in event_ids if e not in event_entry_map]
  
          if missing_events_ids:
              log_ctx = LoggingContext.current_context()
              log_ctx.record_event_fetch(len(missing_events_ids))
  
              # Note that _get_events_from_db is also responsible for turning db rows
              # into FrozenEvents (via _get_event_from_row), which involves seeing if
              # the events have been redacted, and if so pulling the redaction event out
              # of the database to check it.
              #
              missing_events = yield self._get_events_from_db(
                  missing_events_ids, allow_rejected=allow_rejected
              )
  
              event_entry_map.update(missing_events)
  
          return event_entry_map
  
      def _invalidate_get_event_cache(self, event_id):
          self._get_event_cache.invalidate((event_id,))
  
      def _get_events_from_cache(self, events, allow_rejected, update_metrics=True):
          """Fetch events from the caches
  
          Args:
              events (Iterable[str]): list of event_ids to fetch
              allow_rejected (bool): Whether to return events that were rejected
              update_metrics (bool): Whether to update the cache hit ratio metrics
  
          Returns:
              dict of event_id -> _EventCacheEntry for each event_id in cache. If
              allow_rejected is `False` then there will still be an entry but it
              will be `None`
          """
          event_map = {}
  
          for event_id in events:
              ret = self._get_event_cache.get(
                  (event_id,), None, update_metrics=update_metrics
              )
              if not ret:
                  continue
  
              if allow_rejected or not ret.event.rejected_reason:
                  event_map[event_id] = ret
              else:
                  event_map[event_id] = None
  
          return event_map
  
      def _do_fetch(self, conn):
          """Takes a database connection and waits for requests for events from
          the _event_fetch_list queue.
          """
          i = 0
          while True:
              with self._event_fetch_lock:
                  event_list = self._event_fetch_list
                  self._event_fetch_list = []
  
                  if not event_list:
                      single_threaded = self.database_engine.single_threaded
                      if single_threaded or i > EVENT_QUEUE_ITERATIONS:
                          self._event_fetch_ongoing -= 1
                          return
                      else:
                          self._event_fetch_lock.wait(EVENT_QUEUE_TIMEOUT_S)
                          i += 1
                          continue
                  i = 0
  
              self._fetch_event_list(conn, event_list)
  
      def _fetch_event_list(self, conn, event_list):
          """Handle a load of requests from the _event_fetch_list queue
  
          Args:
              conn (twisted.enterprise.adbapi.Connection): database connection
  
              event_list (list[Tuple[list[str], Deferred]]):
                  The fetch requests. Each entry consists of a list of event
                  ids to be fetched, and a deferred to be completed once the
                  events have been fetched.
  
                  The deferreds are callbacked with a dictionary mapping from event id
                  to event row. Note that it may well contain additional events that
                  were not part of this request.
          """
          with Measure(self._clock, "_fetch_event_list"):
              try:
                  events_to_fetch = set(
                      event_id for events, _ in event_list for event_id in events
                  )
  
                  row_dict = self._new_transaction(
                      conn, "do_fetch", [], [], self._fetch_event_rows, events_to_fetch
                  )
  
                  # We only want to resolve deferreds from the main thread
                  def fire():
                      for _, d in event_list:
                          d.callback(row_dict)
  
                  with PreserveLoggingContext():
                      self.hs.get_reactor().callFromThread(fire)
              except Exception as e:
                  logger.exception("do_fetch")
  
                  # We only want to resolve deferreds from the main thread
                  def fire(evs, exc):
                      for _, d in evs:
                          if not d.called:
                              with PreserveLoggingContext():
                                  d.errback(exc)
  
                  with PreserveLoggingContext():
                      self.hs.get_reactor().callFromThread(fire, event_list, e)
  
      @defer.inlineCallbacks
      def _get_events_from_db(self, event_ids, allow_rejected=False):
          """Fetch a bunch of events from the database.
  
          Returned events will be added to the cache for future lookups.
  
          Args:
              event_ids (Iterable[str]): The event_ids of the events to fetch
              allow_rejected (bool): Whether to include rejected events
  
          Returns:
              Deferred[Dict[str, _EventCacheEntry]]:
                  map from event id to result. May return extra events which
                  weren't asked for.
          """
          fetched_events = {}
          events_to_fetch = event_ids
  
          while events_to_fetch:
              row_map = yield self._enqueue_events(events_to_fetch)
  
              # we need to recursively fetch any redactions of those events
              redaction_ids = set()
              for event_id in events_to_fetch:
                  row = row_map.get(event_id)
                  fetched_events[event_id] = row
                  if row:
                      redaction_ids.update(row["redactions"])
  
              events_to_fetch = redaction_ids.difference(fetched_events.keys())
              if events_to_fetch:
                  logger.debug("Also fetching redaction events %s", events_to_fetch)
  
          # build a map from event_id to EventBase
          event_map = {}
          for event_id, row in fetched_events.items():
              if not row:
                  continue
              assert row["event_id"] == event_id
  
              rejected_reason = row["rejected_reason"]
  
              if not allow_rejected and rejected_reason:
                  continue
  
              d = json.loads(row["json"])
              internal_metadata = json.loads(row["internal_metadata"])
  
              format_version = row["format_version"]
              if format_version is None:
                  # This means that we stored the event before we had the concept
                  # of a event format version, so it must be a V1 event.
                  format_version = EventFormatVersions.V1
  
              original_ev = event_type_from_format_version(format_version)(
                  event_dict=d,
                  internal_metadata_dict=internal_metadata,
                  rejected_reason=rejected_reason,
              )
  
              event_map[event_id] = original_ev
  
          # finally, we can decide whether each one nededs redacting, and build
          # the cache entries.
          result_map = {}
          for event_id, original_ev in event_map.items():
              redactions = fetched_events[event_id]["redactions"]
              redacted_event = self._maybe_redact_event_row(
                  original_ev, redactions, event_map
              )
  
              cache_entry = _EventCacheEntry(
                  event=original_ev, redacted_event=redacted_event
              )
  
              self._get_event_cache.prefill((event_id,), cache_entry)
              result_map[event_id] = cache_entry
  
          return result_map
  
      @defer.inlineCallbacks
      def _enqueue_events(self, events):
          """Fetches events from the database using the _event_fetch_list. This
          allows batch and bulk fetching of events - it allows us to fetch events
          without having to create a new transaction for each request for events.
  
          Args:
              events (Iterable[str]): events to be fetched.
  
          Returns:
              Deferred[Dict[str, Dict]]: map from event id to row data from the database.
                  May contain events that weren't requested.
          """
  
          events_d = defer.Deferred()
          with self._event_fetch_lock:
              self._event_fetch_list.append((events, events_d))
  
              self._event_fetch_lock.notify()
  
              if self._event_fetch_ongoing < EVENT_QUEUE_THREADS:
                  self._event_fetch_ongoing += 1
                  should_start = True
              else:
                  should_start = False
  
          if should_start:
              run_as_background_process(
                  "fetch_events", self.runWithConnection, self._do_fetch
              )
  
          logger.debug("Loading %d events: %s", len(events), events)
          with PreserveLoggingContext():
              row_map = yield events_d
          logger.debug("Loaded %d events (%d rows)", len(events), len(row_map))
  
          return row_map
  
      def _fetch_event_rows(self, txn, event_ids):
          """Fetch event rows from the database
  
          Events which are not found are omitted from the result.
  
          The returned per-event dicts contain the following keys:
  
           * event_id (str)
  
           * json (str): json-encoded event structure
  
           * internal_metadata (str): json-encoded internal metadata dict
  
           * format_version (int|None): The format of the event. Hopefully one
             of EventFormatVersions. 'None' means the event predates
             EventFormatVersions (so the event is format V1).
  
           * rejected_reason (str|None): if the event was rejected, the reason
             why.
  
           * redactions (List[str]): a list of event-ids which (claim to) redact
             this event.
  
          Args:
              txn (twisted.enterprise.adbapi.Connection):
              event_ids (Iterable[str]): event IDs to fetch
  
          Returns:
              Dict[str, Dict]: a map from event id to event info.
          """
          event_dict = {}
          for evs in batch_iter(event_ids, 200):
              sql = (
                  "SELECT "
                  " e.event_id, "
                  " e.internal_metadata,"
                  " e.json,"
                  " e.format_version, "
                  " rej.reason "
                  " FROM event_json as e"
                  " LEFT JOIN rejections as rej USING (event_id)"
                  " WHERE e.event_id IN (%s)"
              ) % (",".join(["?"] * len(evs)),)
  
              txn.execute(sql, evs)
  
              for row in txn:
                  event_id = row[0]
                  event_dict[event_id] = {
                      "event_id": event_id,
                      "internal_metadata": row[1],
                      "json": row[2],
                      "format_version": row[3],
                      "rejected_reason": row[4],
                      "redactions": [],
                  }
  
              # check for redactions
              redactions_sql = (
                  "SELECT event_id, redacts FROM redactions WHERE redacts IN (%s)"
              ) % (",".join(["?"] * len(evs)),)
  
              txn.execute(redactions_sql, evs)
  
              for (redacter, redacted) in txn:
                  d = event_dict.get(redacted)
                  if d:
                      d["redactions"].append(redacter)
  
          return event_dict
  
      def _maybe_redact_event_row(self, original_ev, redactions, event_map):
          """Given an event object and a list of possible redacting event ids,
          determine whether to honour any of those redactions and if so return a redacted
          event.
  
          Args:
               original_ev (EventBase):
               redactions (iterable[str]): list of event ids of potential redaction events
               event_map (dict[str, EventBase]): other events which have been fetched, in
                   which we can look up the redaaction events. Map from event id to event.
  
          Returns:
              Deferred[EventBase|None]: if the event should be redacted, a pruned
                  event object. Otherwise, None.
          """
          if original_ev.type == "m.room.create":
              # we choose to ignore redactions of m.room.create events.
              return None
  
          for redaction_id in redactions:
              redaction_event = event_map.get(redaction_id)
              if not redaction_event or redaction_event.rejected_reason:
                  # we don't have the redaction event, or the redaction event was not
                  # authorized.
                  logger.debug(
                      "%s was redacted by %s but redaction not found/authed",
                      original_ev.event_id,
                      redaction_id,
                  )
                  continue
  
              if redaction_event.room_id != original_ev.room_id:
                  logger.debug(
                      "%s was redacted by %s but redaction was in a different room!",
                      original_ev.event_id,
                      redaction_id,
                  )
                  continue
  
              # Starting in room version v3, some redactions need to be
              # rechecked if we didn't have the redacted event at the
              # time, so we recheck on read instead.
              if redaction_event.internal_metadata.need_to_check_redaction():
                  expected_domain = get_domain_from_id(original_ev.sender)
                  if get_domain_from_id(redaction_event.sender) == expected_domain:
                      # This redaction event is allowed. Mark as not needing a recheck.
                      redaction_event.internal_metadata.recheck_redaction = False
                  else:
                      # Senders don't match, so the event isn't actually redacted
                      logger.debug(
                          "%s was redacted by %s but the senders don't match",
                          original_ev.event_id,
                          redaction_id,
                      )
                      continue
  
              logger.debug("Redacting %s due to %s", original_ev.event_id, redaction_id)
  
              # we found a good redaction event. Redact!
              redacted_event = prune_event(original_ev)
              redacted_event.unsigned["redacted_by"] = redaction_id
  
              # It's fine to add the event directly, since get_pdu_json
              # will serialise this field correctly
              redacted_event.unsigned["redacted_because"] = redaction_event
  
              return redacted_event
  
          # no valid redaction found for this event
          return None
  
      @defer.inlineCallbacks
      def have_events_in_timeline(self, event_ids):
          """Given a list of event ids, check if we have already processed and
          stored them as non outliers.
          """
          rows = yield self._simple_select_many_batch(
              table="events",
              retcols=("event_id",),
              column="event_id",
              iterable=list(event_ids),
              keyvalues={"outlier": False},
              desc="have_events_in_timeline",
          )
  
          return set(r["event_id"] for r in rows)
  
      @defer.inlineCallbacks
      def have_seen_events(self, event_ids):
          """Given a list of event ids, check if we have already processed them.
  
          Args:
              event_ids (iterable[str]):
  
          Returns:
              Deferred[set[str]]: The events we have already seen.
          """
          results = set()
  
          def have_seen_events_txn(txn, chunk):
              sql = "SELECT event_id FROM events as e WHERE e.event_id IN (%s)" % (
                  ",".join("?" * len(chunk)),
              )
              txn.execute(sql, chunk)
              for (event_id,) in txn:
                  results.add(event_id)
  
          # break the input up into chunks of 100
          input_iterator = iter(event_ids)
          for chunk in iter(lambda: list(itertools.islice(input_iterator, 100)), []):
              yield self.runInteraction("have_seen_events", have_seen_events_txn, chunk)
          return results
  
      def get_seen_events_with_rejections(self, event_ids):
          """Given a list of event ids, check if we rejected them.
  
          Args:
              event_ids (list[str])
  
          Returns:
              Deferred[dict[str, str|None):
                  Has an entry for each event id we already have seen. Maps to
                  the rejected reason string if we rejected the event, else maps
                  to None.
          """
          if not event_ids:
              return defer.succeed({})
  
          def f(txn):
              sql = (
                  "SELECT e.event_id, reason FROM events as e "
                  "LEFT JOIN rejections as r ON e.event_id = r.event_id "
                  "WHERE e.event_id = ?"
              )
  
              res = {}
              for event_id in event_ids:
                  txn.execute(sql, (event_id,))
                  row = txn.fetchone()
                  if row:
                      _, rejected = row
                      res[event_id] = rejected
  
              return res
  
          return self.runInteraction("get_seen_events_with_rejections", f)
  
      def _get_total_state_event_counts_txn(self, txn, room_id):
          """
          See get_total_state_event_counts.
          """
          # We join against the events table as that has an index on room_id
          sql = """
              SELECT COUNT(*) FROM state_events
              INNER JOIN events USING (room_id, event_id)
              WHERE room_id=?
          """
          txn.execute(sql, (room_id,))
          row = txn.fetchone()
          return row[0] if row else 0
  
      def get_total_state_event_counts(self, room_id):
          """
          Gets the total number of state events in a room.
  
          Args:
              room_id (str)
  
          Returns:
              Deferred[int]
          """
          return self.runInteraction(
              "get_total_state_event_counts",
              self._get_total_state_event_counts_txn,
              room_id,
          )
  
      def _get_current_state_event_counts_txn(self, txn, room_id):
          """
          See get_current_state_event_counts.
          """
          sql = "SELECT COUNT(*) FROM current_state_events WHERE room_id=?"
          txn.execute(sql, (room_id,))
          row = txn.fetchone()
          return row[0] if row else 0
  
      def get_current_state_event_counts(self, room_id):
          """
          Gets the current number of state events in a room.
  
          Args:
              room_id (str)
  
          Returns:
              Deferred[int]
          """
          return self.runInteraction(
              "get_current_state_event_counts",
              self._get_current_state_event_counts_txn,
              room_id,
          )
  
      @defer.inlineCallbacks
      def get_room_complexity(self, room_id):
          """
          Get a rough approximation of the complexity of the room. This is used by
          remote servers to decide whether they wish to join the room or not.
          Higher complexity value indicates that being in the room will consume
          more resources.
  
          Args:
              room_id (str)
  
          Returns:
              Deferred[dict[str:int]] of complexity version to complexity.
          """
          state_events = yield self.get_current_state_event_counts(room_id)
  
          # Call this one "v1", so we can introduce new ones as we want to develop
          # it.
          complexity_v1 = round(state_events / 500, 2)
  
          return {"v1": complexity_v1}
  