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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, List, Optional, Tuple
- import attr
- from frozendict import frozendict
- from synapse.appservice import ApplicationService
- from synapse.events import EventBase
- from synapse.types import JsonDict, StateMap
- if TYPE_CHECKING:
- from synapse.storage.controllers import StorageControllers
- from synapse.storage.databases.main import DataStore
- from synapse.storage.state import StateFilter
- @attr.s(slots=True, auto_attribs=True)
- class EventContext:
- """
- Holds information relevant to persisting an event
- Attributes:
- rejected: A rejection reason if the event was rejected, else None
- _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``.
- state_delta_due_to_event: If `state_group` and `state_group_before_event` are not None
- then this is the delta of the state between the two groups.
- 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
- ``state_group_before_event``.
- 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.
- partial_state: if True, we may be storing this event with a temporary,
- incomplete state.
- """
- _storage: "StorageControllers"
- rejected: Optional[str] = None
- _state_group: Optional[int] = None
- state_group_before_event: Optional[int] = None
- _state_delta_due_to_event: Optional[StateMap[str]] = None
- prev_group: Optional[int] = None
- delta_ids: Optional[StateMap[str]] = None
- app_service: Optional[ApplicationService] = None
- partial_state: bool = False
- @staticmethod
- def with_state(
- storage: "StorageControllers",
- state_group: Optional[int],
- state_group_before_event: Optional[int],
- state_delta_due_to_event: Optional[StateMap[str]],
- partial_state: bool,
- prev_group: Optional[int] = None,
- delta_ids: Optional[StateMap[str]] = None,
- ) -> "EventContext":
- return EventContext(
- storage=storage,
- state_group=state_group,
- state_group_before_event=state_group_before_event,
- state_delta_due_to_event=state_delta_due_to_event,
- prev_group=prev_group,
- delta_ids=delta_ids,
- partial_state=partial_state,
- )
- @staticmethod
- def for_outlier(
- storage: "StorageControllers",
- ) -> "EventContext":
- """Return an EventContext instance suitable for persisting an outlier event"""
- return EventContext(storage=storage)
- async def serialize(self, event: EventBase, store: "DataStore") -> JsonDict:
- """Converts self to a type that can be serialized as JSON, and then
- deserialized by `deserialize`
- Args:
- event: The event that this context relates to
- Returns:
- The serialized event.
- """
- return {
- "state_group": self._state_group,
- "state_group_before_event": self.state_group_before_event,
- "rejected": self.rejected,
- "prev_group": self.prev_group,
- "state_delta_due_to_event": _encode_state_dict(
- self._state_delta_due_to_event
- ),
- "delta_ids": _encode_state_dict(self.delta_ids),
- "app_service_id": self.app_service.id if self.app_service else None,
- "partial_state": self.partial_state,
- }
- @staticmethod
- def deserialize(storage: "StorageControllers", input: JsonDict) -> "EventContext":
- """Converts a dict that was produced by `serialize` back into a
- EventContext.
- Args:
- storage: Used to convert AS ID to AS object and fetch state.
- input: A dict produced by `serialize`
- Returns:
- The event context.
- """
- context = EventContext(
- # 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,
- state_group=input["state_group"],
- state_group_before_event=input["state_group_before_event"],
- prev_group=input["prev_group"],
- state_delta_due_to_event=_decode_state_dict(
- input["state_delta_due_to_event"]
- ),
- delta_ids=_decode_state_dict(input["delta_ids"]),
- rejected=input["rejected"],
- partial_state=input.get("partial_state", False),
- )
- 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, state_filter: Optional["StateFilter"] = None
- ) -> 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.
- Arg:
- state_filter: specifies the type of state event to fetch from DB, example: EventTypes.JoinRules
- 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")
- assert self._state_delta_due_to_event is not None
- prev_state_ids = await self.get_prev_state_ids(state_filter)
- if self._state_delta_due_to_event:
- prev_state_ids = dict(prev_state_ids)
- prev_state_ids.update(self._state_delta_due_to_event)
- return prev_state_ids
- async def get_prev_state_ids(
- self, state_filter: Optional["StateFilter"] = None
- ) -> StateMap[str]:
- """
- Gets the room state map, excluding this event.
- For a non-state event, this will be the same as get_current_state_ids().
- Args:
- state_filter: specifies the type of state event to fetch from DB, example: EventTypes.JoinRules
- Returns:
- Returns {} 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.
- """
- assert self.state_group_before_event is not None
- return await self._storage.state.get_state_ids_for_group(
- self.state_group_before_event, state_filter
- )
- def _encode_state_dict(
- state_dict: Optional[StateMap[str]],
- ) -> Optional[List[Tuple[str, str, str]]]:
- """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: Optional[List[Tuple[str, str, str]]]
- ) -> Optional[StateMap[str]]:
- """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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