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- # 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})
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