summary refs log tree commit diff
path: root/synapse/events/snapshot.py
blob: b700cbbfa197dbf72d4785f2ae4130992d45cf91 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
# 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, Union

import attr
from frozendict import frozendict
from typing_extensions import Literal

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 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``.

        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 ``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.

        partial_state: if True, we may be storing this event with a temporary,
            incomplete state.
    """

    _storage: "StorageControllers"
    rejected: Union[Literal[False], str] = False
    _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})