text: # -*- coding: utf-8 -*-
  # Copyright 2014 - 2016 OpenMarket 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 logging
  from collections import namedtuple
  from typing import (
      Awaitable,
      Callable,
      Dict,
      Iterable,
      List,
      Optional,
      Set,
      Tuple,
      TypeVar,
      Union,
  )
  
  from prometheus_client import Counter
  
  from twisted.internet import defer
  
  import synapse.server
  from synapse.api.constants import EventTypes, Membership
  from synapse.api.errors import AuthError
  from synapse.events import EventBase
  from synapse.handlers.presence import format_user_presence_state
  from synapse.logging.context import PreserveLoggingContext
  from synapse.logging.utils import log_function
  from synapse.metrics import LaterGauge
  from synapse.metrics.background_process_metrics import run_as_background_process
  from synapse.streams.config import PaginationConfig
  from synapse.types import (
      Collection,
      PersistedEventPosition,
      RoomStreamToken,
      StreamToken,
      UserID,
  )
  from synapse.util.async_helpers import ObservableDeferred, timeout_deferred
  from synapse.util.metrics import Measure
  from synapse.visibility import filter_events_for_client
  
  logger = logging.getLogger(__name__)
  
  notified_events_counter = Counter("synapse_notifier_notified_events", "")
  
  users_woken_by_stream_counter = Counter(
      "synapse_notifier_users_woken_by_stream", "", ["stream"]
  )
  
  T = TypeVar("T")
  
  
  # TODO(paul): Should be shared somewhere
  def count(func: Callable[[T], bool], it: Iterable[T]) -> int:
      """Return the number of items in it for which func returns true."""
      n = 0
      for x in it:
          if func(x):
              n += 1
      return n
  
  
  class _NotificationListener:
      """ This represents a single client connection to the events stream.
      The events stream handler will have yielded to the deferred, so to
      notify the handler it is sufficient to resolve the deferred.
      """
  
      __slots__ = ["deferred"]
  
      def __init__(self, deferred):
          self.deferred = deferred
  
  
  class _NotifierUserStream:
      """This represents a user connected to the event stream.
      It tracks the most recent stream token for that user.
      At a given point a user may have a number of streams listening for
      events.
  
      This listener will also keep track of which rooms it is listening in
      so that it can remove itself from the indexes in the Notifier class.
      """
  
      def __init__(
          self,
          user_id: str,
          rooms: Collection[str],
          current_token: StreamToken,
          time_now_ms: int,
      ):
          self.user_id = user_id
          self.rooms = set(rooms)
          self.current_token = current_token
  
          # The last token for which we should wake up any streams that have a
          # token that comes before it. This gets updated every time we get poked.
          # We start it at the current token since if we get any streams
          # that have a token from before we have no idea whether they should be
          # woken up or not, so lets just wake them up.
          self.last_notified_token = current_token
          self.last_notified_ms = time_now_ms
  
          with PreserveLoggingContext():
              self.notify_deferred = ObservableDeferred(defer.Deferred())
  
      def notify(
          self, stream_key: str, stream_id: Union[int, RoomStreamToken], time_now_ms: int,
      ):
          """Notify any listeners for this user of a new event from an
          event source.
          Args:
              stream_key: The stream the event came from.
              stream_id: The new id for the stream the event came from.
              time_now_ms: The current time in milliseconds.
          """
          self.current_token = self.current_token.copy_and_advance(stream_key, stream_id)
          self.last_notified_token = self.current_token
          self.last_notified_ms = time_now_ms
          noify_deferred = self.notify_deferred
  
          users_woken_by_stream_counter.labels(stream_key).inc()
  
          with PreserveLoggingContext():
              self.notify_deferred = ObservableDeferred(defer.Deferred())
              noify_deferred.callback(self.current_token)
  
      def remove(self, notifier: "Notifier"):
          """ Remove this listener from all the indexes in the Notifier
          it knows about.
          """
  
          for room in self.rooms:
              lst = notifier.room_to_user_streams.get(room, set())
              lst.discard(self)
  
          notifier.user_to_user_stream.pop(self.user_id)
  
      def count_listeners(self) -> int:
          return len(self.notify_deferred.observers())
  
      def new_listener(self, token: StreamToken) -> _NotificationListener:
          """Returns a deferred that is resolved when there is a new token
          greater than the given token.
  
          Args:
              token: The token from which we are streaming from, i.e. we shouldn't
                  notify for things that happened before this.
          """
          # Immediately wake up stream if something has already since happened
          # since their last token.
          if self.last_notified_token != token:
              return _NotificationListener(defer.succeed(self.current_token))
          else:
              return _NotificationListener(self.notify_deferred.observe())
  
  
  class EventStreamResult(namedtuple("EventStreamResult", ("events", "tokens"))):
      def __bool__(self):
          return bool(self.events)
  
  
  class Notifier:
      """ This class is responsible for notifying any listeners when there are
      new events available for it.
  
      Primarily used from the /events stream.
      """
  
      UNUSED_STREAM_EXPIRY_MS = 10 * 60 * 1000
  
      def __init__(self, hs: "synapse.server.HomeServer"):
          self.user_to_user_stream = {}  # type: Dict[str, _NotifierUserStream]
          self.room_to_user_streams = {}  # type: Dict[str, Set[_NotifierUserStream]]
  
          self.hs = hs
          self.storage = hs.get_storage()
          self.event_sources = hs.get_event_sources()
          self.store = hs.get_datastore()
          self.pending_new_room_events = (
              []
          )  # type: List[Tuple[PersistedEventPosition, EventBase, Collection[UserID]]]
  
          # Called when there are new things to stream over replication
          self.replication_callbacks = []  # type: List[Callable[[], None]]
  
          # Called when remote servers have come back online after having been
          # down.
          self.remote_server_up_callbacks = []  # type: List[Callable[[str], None]]
  
          self.clock = hs.get_clock()
          self.appservice_handler = hs.get_application_service_handler()
          self._pusher_pool = hs.get_pusherpool()
  
          self.federation_sender = None
          if hs.should_send_federation():
              self.federation_sender = hs.get_federation_sender()
  
          self.state_handler = hs.get_state_handler()
  
          self.clock.looping_call(
              self.remove_expired_streams, self.UNUSED_STREAM_EXPIRY_MS
          )
  
          # This is not a very cheap test to perform, but it's only executed
          # when rendering the metrics page, which is likely once per minute at
          # most when scraping it.
          def count_listeners():
              all_user_streams = set()  # type: Set[_NotifierUserStream]
  
              for streams in list(self.room_to_user_streams.values()):
                  all_user_streams |= streams
              for stream in list(self.user_to_user_stream.values()):
                  all_user_streams.add(stream)
  
              return sum(stream.count_listeners() for stream in all_user_streams)
  
          LaterGauge("synapse_notifier_listeners", "", [], count_listeners)
  
          LaterGauge(
              "synapse_notifier_rooms",
              "",
              [],
              lambda: count(bool, list(self.room_to_user_streams.values())),
          )
          LaterGauge(
              "synapse_notifier_users", "", [], lambda: len(self.user_to_user_stream)
          )
  
      def add_replication_callback(self, cb: Callable[[], None]):
          """Add a callback that will be called when some new data is available.
          Callback is not given any arguments. It should *not* return a Deferred - if
          it needs to do any asynchronous work, a background thread should be started and
          wrapped with run_as_background_process.
          """
          self.replication_callbacks.append(cb)
  
      def on_new_room_event(
          self,
          event: EventBase,
          event_pos: PersistedEventPosition,
          max_room_stream_token: RoomStreamToken,
          extra_users: Collection[UserID] = [],
      ):
          """ Used by handlers to inform the notifier something has happened
          in the room, room event wise.
  
          This triggers the notifier to wake up any listeners that are
          listening to the room, and any listeners for the users in the
          `extra_users` param.
  
          The events can be peristed out of order. The notifier will wait
          until all previous events have been persisted before notifying
          the client streams.
          """
          self.pending_new_room_events.append((event_pos, event, extra_users))
          self._notify_pending_new_room_events(max_room_stream_token)
  
          self.notify_replication()
  
      def _notify_pending_new_room_events(self, max_room_stream_token: RoomStreamToken):
          """Notify for the room events that were queued waiting for a previous
          event to be persisted.
          Args:
              max_room_stream_token: The highest stream_id below which all
                  events have been persisted.
          """
          pending = self.pending_new_room_events
          self.pending_new_room_events = []
  
          users = set()  # type: Set[UserID]
          rooms = set()  # type: Set[str]
  
          for event_pos, event, extra_users in pending:
              if event_pos.persisted_after(max_room_stream_token):
                  self.pending_new_room_events.append((event_pos, event, extra_users))
              else:
                  if (
                      event.type == EventTypes.Member
                      and event.membership == Membership.JOIN
                  ):
                      self._user_joined_room(event.state_key, event.room_id)
  
                  users.update(extra_users)
                  rooms.add(event.room_id)
  
          if users or rooms:
              self.on_new_event(
                  "room_key", max_room_stream_token, users=users, rooms=rooms,
              )
              self._on_updated_room_token(max_room_stream_token)
  
      def _on_updated_room_token(self, max_room_stream_token: RoomStreamToken):
          """Poke services that might care that the room position has been
          updated.
          """
  
          # poke any interested application service.
          run_as_background_process(
              "_notify_app_services", self._notify_app_services, max_room_stream_token
          )
  
          run_as_background_process(
              "_notify_pusher_pool", self._notify_pusher_pool, max_room_stream_token
          )
  
          if self.federation_sender:
              self.federation_sender.notify_new_events(max_room_stream_token)
  
      async def _notify_app_services(self, max_room_stream_token: RoomStreamToken):
          try:
              await self.appservice_handler.notify_interested_services(
                  max_room_stream_token
              )
          except Exception:
              logger.exception("Error notifying application services of event")
  
      async def _notify_app_services_ephemeral(
          self,
          stream_key: str,
          new_token: Union[int, RoomStreamToken],
          users: Collection[UserID] = [],
      ):
          try:
              stream_token = None
              if isinstance(new_token, int):
                  stream_token = new_token
              await self.appservice_handler.notify_interested_services_ephemeral(
                  stream_key, stream_token, users
              )
          except Exception:
              logger.exception("Error notifying application services of event")
  
      async def _notify_pusher_pool(self, max_room_stream_token: RoomStreamToken):
          try:
              await self._pusher_pool.on_new_notifications(max_room_stream_token)
          except Exception:
              logger.exception("Error pusher pool of event")
  
      def on_new_event(
          self,
          stream_key: str,
          new_token: Union[int, RoomStreamToken],
          users: Collection[Union[str, UserID]] = [],
          rooms: Collection[str] = [],
      ):
          """ Used to inform listeners that something has happened event wise.
  
          Will wake up all listeners for the given users and rooms.
          """
          with PreserveLoggingContext():
              with Measure(self.clock, "on_new_event"):
                  user_streams = set()
  
                  for user in users:
                      user_stream = self.user_to_user_stream.get(str(user))
                      if user_stream is not None:
                          user_streams.add(user_stream)
  
                  for room in rooms:
                      user_streams |= self.room_to_user_streams.get(room, set())
  
                  time_now_ms = self.clock.time_msec()
                  for user_stream in user_streams:
                      try:
                          user_stream.notify(stream_key, new_token, time_now_ms)
                      except Exception:
                          logger.exception("Failed to notify listener")
  
                  self.notify_replication()
  
                  # Notify appservices
                  run_as_background_process(
                      "_notify_app_services_ephemeral",
                      self._notify_app_services_ephemeral,
                      stream_key,
                      new_token,
                      users,
                  )
  
      def on_new_replication_data(self) -> None:
          """Used to inform replication listeners that something has happend
          without waking up any of the normal user event streams"""
          self.notify_replication()
  
      async def wait_for_events(
          self,
          user_id: str,
          timeout: int,
          callback: Callable[[StreamToken, StreamToken], Awaitable[T]],
          room_ids=None,
          from_token=StreamToken.START,
      ) -> T:
          """Wait until the callback returns a non empty response or the
          timeout fires.
          """
          user_stream = self.user_to_user_stream.get(user_id)
          if user_stream is None:
              current_token = self.event_sources.get_current_token()
              if room_ids is None:
                  room_ids = await self.store.get_rooms_for_user(user_id)
              user_stream = _NotifierUserStream(
                  user_id=user_id,
                  rooms=room_ids,
                  current_token=current_token,
                  time_now_ms=self.clock.time_msec(),
              )
              self._register_with_keys(user_stream)
  
          result = None
          prev_token = from_token
          if timeout:
              end_time = self.clock.time_msec() + timeout
  
              while not result:
                  try:
                      now = self.clock.time_msec()
                      if end_time <= now:
                          break
  
                      # Now we wait for the _NotifierUserStream to be told there
                      # is a new token.
                      listener = user_stream.new_listener(prev_token)
                      listener.deferred = timeout_deferred(
                          listener.deferred,
                          (end_time - now) / 1000.0,
                          self.hs.get_reactor(),
                      )
                      with PreserveLoggingContext():
                          await listener.deferred
  
                      current_token = user_stream.current_token
  
                      result = await callback(prev_token, current_token)
                      if result:
                          break
  
                      # Update the prev_token to the current_token since nothing
                      # has happened between the old prev_token and the current_token
                      prev_token = current_token
                  except defer.TimeoutError:
                      break
                  except defer.CancelledError:
                      break
  
          if result is None:
              # This happened if there was no timeout or if the timeout had
              # already expired.
              current_token = user_stream.current_token
              result = await callback(prev_token, current_token)
  
          return result
  
      async def get_events_for(
          self,
          user: UserID,
          pagination_config: PaginationConfig,
          timeout: int,
          is_guest: bool = False,
          explicit_room_id: str = None,
      ) -> EventStreamResult:
          """ For the given user and rooms, return any new events for them. If
          there are no new events wait for up to `timeout` milliseconds for any
          new events to happen before returning.
  
          If explicit_room_id is not set, the user's joined rooms will be polled
          for events.
          If explicit_room_id is set, that room will be polled for events only if
          it is world readable or the user has joined the room.
          """
          if pagination_config.from_token:
              from_token = pagination_config.from_token
          else:
              from_token = self.event_sources.get_current_token()
  
          limit = pagination_config.limit
  
          room_ids, is_joined = await self._get_room_ids(user, explicit_room_id)
          is_peeking = not is_joined
  
          async def check_for_updates(
              before_token: StreamToken, after_token: StreamToken
          ) -> EventStreamResult:
              if after_token == before_token:
                  return EventStreamResult([], (from_token, from_token))
  
              events = []  # type: List[EventBase]
              end_token = from_token
  
              for name, source in self.event_sources.sources.items():
                  keyname = "%s_key" % name
                  before_id = getattr(before_token, keyname)
                  after_id = getattr(after_token, keyname)
                  if before_id == after_id:
                      continue
  
                  new_events, new_key = await source.get_new_events(
                      user=user,
                      from_key=getattr(from_token, keyname),
                      limit=limit,
                      is_guest=is_peeking,
                      room_ids=room_ids,
                      explicit_room_id=explicit_room_id,
                  )
  
                  if name == "room":
                      new_events = await filter_events_for_client(
                          self.storage,
                          user.to_string(),
                          new_events,
                          is_peeking=is_peeking,
                      )
                  elif name == "presence":
                      now = self.clock.time_msec()
                      new_events[:] = [
                          {
                              "type": "m.presence",
                              "content": format_user_presence_state(event, now),
                          }
                          for event in new_events
                      ]
  
                  events.extend(new_events)
                  end_token = end_token.copy_and_replace(keyname, new_key)
  
              return EventStreamResult(events, (from_token, end_token))
  
          user_id_for_stream = user.to_string()
          if is_peeking:
              # Internally, the notifier keeps an event stream per user_id.
              # This is used by both /sync and /events.
              # We want /events to be used for peeking independently of /sync,
              # without polluting its contents. So we invent an illegal user ID
              # (which thus cannot clash with any real users) for keying peeking
              # over /events.
              #
              # I am sorry for what I have done.
              user_id_for_stream = "_PEEKING_%s_%s" % (
                  explicit_room_id,
                  user_id_for_stream,
              )
  
          result = await self.wait_for_events(
              user_id_for_stream,
              timeout,
              check_for_updates,
              room_ids=room_ids,
              from_token=from_token,
          )
  
          return result
  
      async def _get_room_ids(
          self, user: UserID, explicit_room_id: Optional[str]
      ) -> Tuple[Collection[str], bool]:
          joined_room_ids = await self.store.get_rooms_for_user(user.to_string())
          if explicit_room_id:
              if explicit_room_id in joined_room_ids:
                  return [explicit_room_id], True
              if await self._is_world_readable(explicit_room_id):
                  return [explicit_room_id], False
              raise AuthError(403, "Non-joined access not allowed")
          return joined_room_ids, True
  
      async def _is_world_readable(self, room_id: str) -> bool:
          state = await self.state_handler.get_current_state(
              room_id, EventTypes.RoomHistoryVisibility, ""
          )
          if state and "history_visibility" in state.content:
              return state.content["history_visibility"] == "world_readable"
          else:
              return False
  
      @log_function
      def remove_expired_streams(self) -> None:
          time_now_ms = self.clock.time_msec()
          expired_streams = []
          expire_before_ts = time_now_ms - self.UNUSED_STREAM_EXPIRY_MS
          for stream in self.user_to_user_stream.values():
              if stream.count_listeners():
                  continue
              if stream.last_notified_ms < expire_before_ts:
                  expired_streams.append(stream)
  
          for expired_stream in expired_streams:
              expired_stream.remove(self)
  
      @log_function
      def _register_with_keys(self, user_stream: _NotifierUserStream):
          self.user_to_user_stream[user_stream.user_id] = user_stream
  
          for room in user_stream.rooms:
              s = self.room_to_user_streams.setdefault(room, set())
              s.add(user_stream)
  
      def _user_joined_room(self, user_id: str, room_id: str):
          new_user_stream = self.user_to_user_stream.get(user_id)
          if new_user_stream is not None:
              room_streams = self.room_to_user_streams.setdefault(room_id, set())
              room_streams.add(new_user_stream)
              new_user_stream.rooms.add(room_id)
  
      def notify_replication(self) -> None:
          """Notify the any replication listeners that there's a new event"""
          for cb in self.replication_callbacks:
              cb()
  
      def notify_remote_server_up(self, server: str):
          """Notify any replication that a remote server has come back up
          """
          # We call federation_sender directly rather than registering as a
          # callback as a) we already have a reference to it and b) it introduces
          # circular dependencies.
          if self.federation_sender:
              self.federation_sender.wake_destination(server)
  