549 lines
17 KiB
Python
549 lines
17 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright 2018 New Vector Ltd
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import heapq
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import itertools
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import logging
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from six import iteritems, itervalues
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from twisted.internet import defer
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from synapse import event_auth
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from synapse.api.constants import EventTypes
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from synapse.api.errors import AuthError
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logger = logging.getLogger(__name__)
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@defer.inlineCallbacks
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def resolve_events_with_store(room_version, state_sets, event_map, state_res_store):
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"""Resolves the state using the v2 state resolution algorithm
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Args:
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room_version (str): The room version
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state_sets(list): List of dicts of (type, state_key) -> event_id,
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which are the different state groups to resolve.
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event_map(dict[str,FrozenEvent]|None):
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a dict from event_id to event, for any events that we happen to
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have in flight (eg, those currently being persisted). This will be
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used as a starting point fof finding the state we need; any missing
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events will be requested via state_res_store.
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If None, all events will be fetched via state_res_store.
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state_res_store (StateResolutionStore)
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Returns
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Deferred[dict[(str, str), str]]:
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a map from (type, state_key) to event_id.
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"""
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logger.debug("Computing conflicted state")
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# We use event_map as a cache, so if its None we need to initialize it
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if event_map is None:
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event_map = {}
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# First split up the un/conflicted state
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unconflicted_state, conflicted_state = _seperate(state_sets)
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if not conflicted_state:
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return unconflicted_state
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logger.debug("%d conflicted state entries", len(conflicted_state))
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logger.debug("Calculating auth chain difference")
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# Also fetch all auth events that appear in only some of the state sets'
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# auth chains.
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auth_diff = yield _get_auth_chain_difference(state_sets, event_map, state_res_store)
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full_conflicted_set = set(
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itertools.chain(
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itertools.chain.from_iterable(itervalues(conflicted_state)), auth_diff
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)
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)
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events = yield state_res_store.get_events(
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[eid for eid in full_conflicted_set if eid not in event_map],
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allow_rejected=True,
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)
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event_map.update(events)
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full_conflicted_set = set(eid for eid in full_conflicted_set if eid in event_map)
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logger.debug("%d full_conflicted_set entries", len(full_conflicted_set))
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# Get and sort all the power events (kicks/bans/etc)
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power_events = (
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eid for eid in full_conflicted_set if _is_power_event(event_map[eid])
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)
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sorted_power_events = yield _reverse_topological_power_sort(
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power_events, event_map, state_res_store, full_conflicted_set
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)
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logger.debug("sorted %d power events", len(sorted_power_events))
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# Now sequentially auth each one
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resolved_state = yield _iterative_auth_checks(
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room_version,
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sorted_power_events,
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unconflicted_state,
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event_map,
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state_res_store,
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)
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logger.debug("resolved power events")
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# OK, so we've now resolved the power events. Now sort the remaining
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# events using the mainline of the resolved power level.
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leftover_events = [
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ev_id for ev_id in full_conflicted_set if ev_id not in sorted_power_events
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]
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logger.debug("sorting %d remaining events", len(leftover_events))
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pl = resolved_state.get((EventTypes.PowerLevels, ""), None)
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leftover_events = yield _mainline_sort(
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leftover_events, pl, event_map, state_res_store
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)
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logger.debug("resolving remaining events")
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resolved_state = yield _iterative_auth_checks(
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room_version, leftover_events, resolved_state, event_map, state_res_store
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)
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logger.debug("resolved")
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# We make sure that unconflicted state always still applies.
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resolved_state.update(unconflicted_state)
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logger.debug("done")
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return resolved_state
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@defer.inlineCallbacks
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def _get_power_level_for_sender(event_id, event_map, state_res_store):
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"""Return the power level of the sender of the given event according to
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their auth events.
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Args:
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event_id (str)
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event_map (dict[str,FrozenEvent])
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state_res_store (StateResolutionStore)
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Returns:
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Deferred[int]
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"""
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event = yield _get_event(event_id, event_map, state_res_store)
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pl = None
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for aid in event.auth_event_ids():
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aev = yield _get_event(aid, event_map, state_res_store)
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if (aev.type, aev.state_key) == (EventTypes.PowerLevels, ""):
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pl = aev
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break
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if pl is None:
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# Couldn't find power level. Check if they're the creator of the room
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for aid in event.auth_event_ids():
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aev = yield _get_event(aid, event_map, state_res_store)
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if (aev.type, aev.state_key) == (EventTypes.Create, ""):
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if aev.content.get("creator") == event.sender:
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return 100
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break
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return 0
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level = pl.content.get("users", {}).get(event.sender)
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if level is None:
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level = pl.content.get("users_default", 0)
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if level is None:
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return 0
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else:
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return int(level)
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@defer.inlineCallbacks
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def _get_auth_chain_difference(state_sets, event_map, state_res_store):
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"""Compare the auth chains of each state set and return the set of events
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that only appear in some but not all of the auth chains.
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Args:
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state_sets (list)
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event_map (dict[str,FrozenEvent])
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state_res_store (StateResolutionStore)
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Returns:
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Deferred[set[str]]: Set of event IDs
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"""
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common = set(itervalues(state_sets[0])).intersection(
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*(itervalues(s) for s in state_sets[1:])
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)
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auth_sets = []
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for state_set in state_sets:
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auth_ids = set(
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eid
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for key, eid in iteritems(state_set)
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if (
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key[0] in (EventTypes.Member, EventTypes.ThirdPartyInvite)
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or key
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in (
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(EventTypes.PowerLevels, ""),
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(EventTypes.Create, ""),
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(EventTypes.JoinRules, ""),
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)
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)
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and eid not in common
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)
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auth_chain = yield state_res_store.get_auth_chain(auth_ids)
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auth_ids.update(auth_chain)
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auth_sets.append(auth_ids)
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intersection = set(auth_sets[0]).intersection(*auth_sets[1:])
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union = set().union(*auth_sets)
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return union - intersection
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def _seperate(state_sets):
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"""Return the unconflicted and conflicted state. This is different than in
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the original algorithm, as this defines a key to be conflicted if one of
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the state sets doesn't have that key.
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Args:
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state_sets (list)
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Returns:
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tuple[dict, dict]: A tuple of unconflicted and conflicted state. The
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conflicted state dict is a map from type/state_key to set of event IDs
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"""
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unconflicted_state = {}
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conflicted_state = {}
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for key in set(itertools.chain.from_iterable(state_sets)):
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event_ids = set(state_set.get(key) for state_set in state_sets)
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if len(event_ids) == 1:
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unconflicted_state[key] = event_ids.pop()
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else:
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event_ids.discard(None)
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conflicted_state[key] = event_ids
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return unconflicted_state, conflicted_state
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def _is_power_event(event):
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"""Return whether or not the event is a "power event", as defined by the
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v2 state resolution algorithm
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Args:
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event (FrozenEvent)
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Returns:
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boolean
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"""
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if (event.type, event.state_key) in (
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(EventTypes.PowerLevels, ""),
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(EventTypes.JoinRules, ""),
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(EventTypes.Create, ""),
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):
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return True
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if event.type == EventTypes.Member:
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if event.membership in ("leave", "ban"):
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return event.sender != event.state_key
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return False
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@defer.inlineCallbacks
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def _add_event_and_auth_chain_to_graph(
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graph, event_id, event_map, state_res_store, auth_diff
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):
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"""Helper function for _reverse_topological_power_sort that add the event
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and its auth chain (that is in the auth diff) to the graph
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Args:
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graph (dict[str, set[str]]): A map from event ID to the events auth
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event IDs
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event_id (str): Event to add to the graph
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event_map (dict[str,FrozenEvent])
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state_res_store (StateResolutionStore)
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auth_diff (set[str]): Set of event IDs that are in the auth difference.
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"""
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state = [event_id]
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while state:
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eid = state.pop()
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graph.setdefault(eid, set())
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event = yield _get_event(eid, event_map, state_res_store)
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for aid in event.auth_event_ids():
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if aid in auth_diff:
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if aid not in graph:
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state.append(aid)
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graph.setdefault(eid, set()).add(aid)
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@defer.inlineCallbacks
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def _reverse_topological_power_sort(event_ids, event_map, state_res_store, auth_diff):
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"""Returns a list of the event_ids sorted by reverse topological ordering,
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and then by power level and origin_server_ts
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Args:
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event_ids (list[str]): The events to sort
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event_map (dict[str,FrozenEvent])
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state_res_store (StateResolutionStore)
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auth_diff (set[str]): Set of event IDs that are in the auth difference.
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Returns:
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Deferred[list[str]]: The sorted list
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"""
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graph = {}
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for event_id in event_ids:
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yield _add_event_and_auth_chain_to_graph(
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graph, event_id, event_map, state_res_store, auth_diff
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)
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event_to_pl = {}
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for event_id in graph:
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pl = yield _get_power_level_for_sender(event_id, event_map, state_res_store)
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event_to_pl[event_id] = pl
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def _get_power_order(event_id):
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ev = event_map[event_id]
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pl = event_to_pl[event_id]
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return -pl, ev.origin_server_ts, event_id
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# Note: graph is modified during the sort
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it = lexicographical_topological_sort(graph, key=_get_power_order)
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sorted_events = list(it)
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return sorted_events
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@defer.inlineCallbacks
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def _iterative_auth_checks(
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room_version, event_ids, base_state, event_map, state_res_store
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):
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"""Sequentially apply auth checks to each event in given list, updating the
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state as it goes along.
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Args:
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room_version (str)
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event_ids (list[str]): Ordered list of events to apply auth checks to
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base_state (dict[tuple[str, str], str]): The set of state to start with
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event_map (dict[str,FrozenEvent])
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state_res_store (StateResolutionStore)
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Returns:
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Deferred[dict[tuple[str, str], str]]: Returns the final updated state
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"""
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resolved_state = base_state.copy()
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for event_id in event_ids:
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event = event_map[event_id]
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auth_events = {}
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for aid in event.auth_event_ids():
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ev = yield _get_event(aid, event_map, state_res_store)
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if ev.rejected_reason is None:
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auth_events[(ev.type, ev.state_key)] = ev
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for key in event_auth.auth_types_for_event(event):
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if key in resolved_state:
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ev_id = resolved_state[key]
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ev = yield _get_event(ev_id, event_map, state_res_store)
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if ev.rejected_reason is None:
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auth_events[key] = event_map[ev_id]
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try:
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event_auth.check(
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room_version,
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event,
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auth_events,
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do_sig_check=False,
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do_size_check=False,
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)
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resolved_state[(event.type, event.state_key)] = event_id
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except AuthError:
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pass
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return resolved_state
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@defer.inlineCallbacks
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def _mainline_sort(event_ids, resolved_power_event_id, event_map, state_res_store):
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"""Returns a sorted list of event_ids sorted by mainline ordering based on
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the given event resolved_power_event_id
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Args:
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event_ids (list[str]): Events to sort
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resolved_power_event_id (str): The final resolved power level event ID
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event_map (dict[str,FrozenEvent])
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state_res_store (StateResolutionStore)
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Returns:
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Deferred[list[str]]: The sorted list
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"""
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mainline = []
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pl = resolved_power_event_id
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while pl:
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mainline.append(pl)
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pl_ev = yield _get_event(pl, event_map, state_res_store)
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auth_events = pl_ev.auth_event_ids()
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pl = None
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for aid in auth_events:
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ev = yield _get_event(aid, event_map, state_res_store)
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if (ev.type, ev.state_key) == (EventTypes.PowerLevels, ""):
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pl = aid
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break
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mainline_map = {ev_id: i + 1 for i, ev_id in enumerate(reversed(mainline))}
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event_ids = list(event_ids)
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order_map = {}
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for ev_id in event_ids:
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depth = yield _get_mainline_depth_for_event(
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event_map[ev_id], mainline_map, event_map, state_res_store
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)
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order_map[ev_id] = (depth, event_map[ev_id].origin_server_ts, ev_id)
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event_ids.sort(key=lambda ev_id: order_map[ev_id])
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return event_ids
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@defer.inlineCallbacks
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def _get_mainline_depth_for_event(event, mainline_map, event_map, state_res_store):
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"""Get the mainline depths for the given event based on the mainline map
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Args:
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event (FrozenEvent)
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mainline_map (dict[str, int]): Map from event_id to mainline depth for
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events in the mainline.
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event_map (dict[str,FrozenEvent])
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state_res_store (StateResolutionStore)
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Returns:
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Deferred[int]
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"""
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# We do an iterative search, replacing `event with the power level in its
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# auth events (if any)
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while event:
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depth = mainline_map.get(event.event_id)
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if depth is not None:
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return depth
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auth_events = event.auth_event_ids()
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event = None
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for aid in auth_events:
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aev = yield _get_event(aid, event_map, state_res_store)
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if (aev.type, aev.state_key) == (EventTypes.PowerLevels, ""):
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event = aev
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break
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# Didn't find a power level auth event, so we just return 0
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return 0
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@defer.inlineCallbacks
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def _get_event(event_id, event_map, state_res_store):
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"""Helper function to look up event in event_map, falling back to looking
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it up in the store
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Args:
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event_id (str)
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event_map (dict[str,FrozenEvent])
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state_res_store (StateResolutionStore)
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Returns:
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Deferred[FrozenEvent]
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"""
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if event_id not in event_map:
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events = yield state_res_store.get_events([event_id], allow_rejected=True)
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event_map.update(events)
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return event_map[event_id]
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def lexicographical_topological_sort(graph, key):
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"""Performs a lexicographic reverse topological sort on the graph.
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This returns a reverse topological sort (i.e. if node A references B then B
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appears before A in the sort), with ties broken lexicographically based on
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return value of the `key` function.
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NOTE: `graph` is modified during the sort.
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Args:
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graph (dict[str, set[str]]): A representation of the graph where each
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node is a key in the dict and its value are the nodes edges.
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key (func): A function that takes a node and returns a value that is
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comparable and used to order nodes
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Yields:
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str: The next node in the topological sort
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"""
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# Note, this is basically Kahn's algorithm except we look at nodes with no
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# outgoing edges, c.f.
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# https://en.wikipedia.org/wiki/Topological_sorting#Kahn's_algorithm
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outdegree_map = graph
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reverse_graph = {}
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# Lists of nodes with zero out degree. Is actually a tuple of
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# `(key(node), node)` so that sorting does the right thing
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zero_outdegree = []
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for node, edges in iteritems(graph):
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if len(edges) == 0:
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zero_outdegree.append((key(node), node))
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reverse_graph.setdefault(node, set())
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for edge in edges:
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reverse_graph.setdefault(edge, set()).add(node)
|
|
|
|
# heapq is a built in implementation of a sorted queue.
|
|
heapq.heapify(zero_outdegree)
|
|
|
|
while zero_outdegree:
|
|
_, node = heapq.heappop(zero_outdegree)
|
|
|
|
for parent in reverse_graph[node]:
|
|
out = outdegree_map[parent]
|
|
out.discard(node)
|
|
if len(out) == 0:
|
|
heapq.heappush(zero_outdegree, (key(parent), parent))
|
|
|
|
yield node
|