# 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. from typing import TYPE_CHECKING, Optional, Union import attr from frozendict import frozendict from synapse.appservice import ApplicationService from synapse.events import EventBase from synapse.logging.context import make_deferred_yieldable, run_in_background from synapse.types import StateMap if TYPE_CHECKING: from synapse.storage.databases.main import DataStore @attr.s(slots=True) class EventContext: """ Holds information relevant to persisting an event Attributes: rejected: A rejection reason if the event was rejected, else False _state_group: The ID of the state group for this event. Note that state events are persisted with a state group which includes the new event, so this is effectively the state *after* the event in question. For a *rejected* state event, where the state of the rejected event is ignored, this state_group should never make it into the event_to_state_groups table. Indeed, inspecting this value for a rejected state event is almost certainly incorrect. For an outlier, where we don't have the state at the event, this will be None. Note that this is a private attribute: it should be accessed via the ``state_group`` property. state_group_before_event: The ID of the state group representing the state of the room before this event. If this is a non-state event, this will be the same as ``state_group``. If it's a state event, it will be the same as ``prev_group``. If ``state_group`` is None (ie, the event is an outlier), ``state_group_before_event`` will always also be ``None``. prev_group: If it is known, ``state_group``'s prev_group. Note that this being None does not necessarily mean that ``state_group`` does not have a prev_group! If the event is a state event, this is normally the same as ``prev_group``. If ``state_group`` is None (ie, the event is an outlier), ``prev_group`` will always also be ``None``. Note that this *not* (necessarily) the state group associated with ``_prev_state_ids``. delta_ids: If ``prev_group`` is not None, the state delta between ``prev_group`` and ``state_group``. app_service: If this event is being sent by a (local) application service, that app service. _current_state_ids: The room state map, including this event - ie, the state in ``state_group``. (type, state_key) -> event_id FIXME: what is this for an outlier? it seems ill-defined. It seems like it could be either {}, or the state we were given by the remote server, depending on $THINGS Note that this is a private attribute: it should be accessed via ``get_current_state_ids``. _AsyncEventContext impl calculates this on-demand: it will be None until that happens. _prev_state_ids: The room state map, excluding this event - ie, the state in ``state_group_before_event``. For a non-state event, this will be the same as _current_state_events. Note that it is a completely different thing to prev_group! (type, state_key) -> event_id FIXME: again, what is this for an outlier? As with _current_state_ids, this is a private attribute. It should be accessed via get_prev_state_ids. """ rejected = attr.ib(default=False, type=Union[bool, str]) _state_group = attr.ib(default=None, type=Optional[int]) state_group_before_event = attr.ib(default=None, type=Optional[int]) prev_group = attr.ib(default=None, type=Optional[int]) delta_ids = attr.ib(default=None, type=Optional[StateMap[str]]) app_service = attr.ib(default=None, type=Optional[ApplicationService]) _current_state_ids = attr.ib(default=None, type=Optional[StateMap[str]]) _prev_state_ids = attr.ib(default=None, type=Optional[StateMap[str]]) @staticmethod def with_state( state_group, state_group_before_event, current_state_ids, prev_state_ids, prev_group=None, delta_ids=None, ): return EventContext( current_state_ids=current_state_ids, prev_state_ids=prev_state_ids, state_group=state_group, state_group_before_event=state_group_before_event, prev_group=prev_group, delta_ids=delta_ids, ) async def serialize(self, event: EventBase, store: "DataStore") -> dict: """Converts self to a type that can be serialized as JSON, and then deserialized by `deserialize` Args: event (FrozenEvent): The event that this context relates to Returns: dict """ # We don't serialize the full state dicts, instead they get pulled out # of the DB on the other side. However, the other side can't figure out # the prev_state_ids, so if we're a state event we include the event # id that we replaced in the state. if event.is_state(): prev_state_ids = await self.get_prev_state_ids() prev_state_id = prev_state_ids.get((event.type, event.state_key)) else: prev_state_id = None return { "prev_state_id": prev_state_id, "event_type": event.type, "event_state_key": event.state_key if event.is_state() else None, "state_group": self._state_group, "state_group_before_event": self.state_group_before_event, "rejected": self.rejected, "prev_group": self.prev_group, "delta_ids": _encode_state_dict(self.delta_ids), "app_service_id": self.app_service.id if self.app_service else None, } @staticmethod def deserialize(storage, input): """Converts a dict that was produced by `serialize` back into a EventContext. Args: storage (Storage): Used to convert AS ID to AS object and fetch state. input (dict): A dict produced by `serialize` Returns: EventContext """ context = _AsyncEventContextImpl( # We use the state_group and prev_state_id stuff to pull the # current_state_ids out of the DB and construct prev_state_ids. storage=storage, prev_state_id=input["prev_state_id"], event_type=input["event_type"], event_state_key=input["event_state_key"], state_group=input["state_group"], state_group_before_event=input["state_group_before_event"], prev_group=input["prev_group"], delta_ids=_decode_state_dict(input["delta_ids"]), rejected=input["rejected"], ) app_service_id = input["app_service_id"] if app_service_id: context.app_service = storage.main.get_app_service_by_id(app_service_id) return context @property def state_group(self) -> Optional[int]: """The ID of the state group for this event. Note that state events are persisted with a state group which includes the new event, so this is effectively the state *after* the event in question. For an outlier, where we don't have the state at the event, this will be None. It is an error to access this for a rejected event, since rejected state should not make it into the room state. Accessing this property will raise an exception if ``rejected`` is set. """ if self.rejected: raise RuntimeError("Attempt to access state_group of rejected event") return self._state_group async def get_current_state_ids(self) -> Optional[StateMap[str]]: """ Gets the room state map, including this event - ie, the state in ``state_group`` It is an error to access this for a rejected event, since rejected state should not make it into the room state. This method will raise an exception if ``rejected`` is set. Returns: Returns None if state_group is None, which happens when the associated event is an outlier. Maps a (type, state_key) to the event ID of the state event matching this tuple. """ if self.rejected: raise RuntimeError("Attempt to access state_ids of rejected event") await self._ensure_fetched() return self._current_state_ids async def get_prev_state_ids(self): """ Gets the room state map, excluding this event. For a non-state event, this will be the same as get_current_state_ids(). Returns: dict[(str, str), str]|None: Returns None if state_group is None, which happens when the associated event is an outlier. Maps a (type, state_key) to the event ID of the state event matching this tuple. """ await self._ensure_fetched() return self._prev_state_ids def get_cached_current_state_ids(self): """Gets the current state IDs if we have them already cached. It is an error to access this for a rejected event, since rejected state should not make it into the room state. This method will raise an exception if ``rejected`` is set. Returns: dict[(str, str), str]|None: Returns None if we haven't cached the state or if state_group is None, which happens when the associated event is an outlier. """ if self.rejected: raise RuntimeError("Attempt to access state_ids of rejected event") return self._current_state_ids async def _ensure_fetched(self): return None @attr.s(slots=True) class _AsyncEventContextImpl(EventContext): """ An implementation of EventContext which fetches _current_state_ids and _prev_state_ids from the database on demand. Attributes: _storage (Storage) _fetching_state_deferred (Deferred|None): Resolves when *_state_ids have been calculated. None if we haven't started calculating yet _event_type (str): The type of the event the context is associated with. _event_state_key (str): The state_key of the event the context is associated with. _prev_state_id (str|None): If the event associated with the context is a state event, then `_prev_state_id` is the event_id of the state that was replaced. """ # This needs to have a default as we're inheriting _storage = attr.ib(default=None) _prev_state_id = attr.ib(default=None) _event_type = attr.ib(default=None) _event_state_key = attr.ib(default=None) _fetching_state_deferred = attr.ib(default=None) async def _ensure_fetched(self): if not self._fetching_state_deferred: self._fetching_state_deferred = run_in_background(self._fill_out_state) return await make_deferred_yieldable(self._fetching_state_deferred) async def _fill_out_state(self): """Called to populate the _current_state_ids and _prev_state_ids attributes by loading from the database. """ if self.state_group is None: return self._current_state_ids = await self._storage.state.get_state_ids_for_group( self.state_group ) if self._event_state_key is not None: self._prev_state_ids = dict(self._current_state_ids) key = (self._event_type, self._event_state_key) if self._prev_state_id: self._prev_state_ids[key] = self._prev_state_id else: self._prev_state_ids.pop(key, None) else: self._prev_state_ids = self._current_state_ids def _encode_state_dict(state_dict): """Since dicts of (type, state_key) -> event_id cannot be serialized in JSON we need to convert them to a form that can. """ if state_dict is None: return None return [(etype, state_key, v) for (etype, state_key), v in state_dict.items()] def _decode_state_dict(input): """Decodes a state dict encoded using `_encode_state_dict` above""" if input is None: return None return frozendict({(etype, state_key): v for etype, state_key, v in input})