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# Copyright 2018 New Vector 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 typing import TYPE_CHECKING, Optional
if TYPE_CHECKING:
from synapse.server import HomeServer
logger = logging.getLogger(__name__)
class StateDeltasHandler:
def __init__(self, hs: "HomeServer"):
self.store = hs.get_datastore()
async def _get_key_change(
self,
prev_event_id: Optional[str],
event_id: Optional[str],
key_name: str,
public_value: str,
) -> Optional[bool]:
"""Given two events check if the `key_name` field in content changed
from not matching `public_value` to doing so.
For example, check if `history_visibility` (`key_name`) changed from
`shared` to `world_readable` (`public_value`).
Returns:
None if the field in the events either both match `public_value`
or if neither do, i.e. there has been no change.
True if it didn't match `public_value` but now does
False if it did match `public_value` but now doesn't
"""
prev_event = None
event = None
if prev_event_id:
prev_event = await self.store.get_event(prev_event_id, allow_none=True)
if event_id:
event = await self.store.get_event(event_id, allow_none=True)
if not event and not prev_event:
logger.debug("Neither event exists: %r %r", prev_event_id, event_id)
return None
prev_value = None
value = None
if prev_event:
prev_value = prev_event.content.get(key_name)
if event:
value = event.content.get(key_name)
logger.debug("prev_value: %r -> value: %r", prev_value, value)
if value == public_value and prev_value != public_value:
return True
elif value != public_value and prev_value == public_value:
return False
else:
return None
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