architex/lib/matrix_server/state_resolution.ex

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Elixir
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defmodule MatrixServer.StateResolution do
import Ecto.Query
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alias MatrixServer.{Repo, Event, Room}
def resolve(event), do: resolve(event, true)
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def resolve(%Event{room_id: room_id} = event, apply_state) do
room_events =
Event
|> where([e], e.room_id == ^room_id)
|> select([e], {e.event_id, e})
|> Repo.all()
|> Enum.into(%{})
resolve(event, room_events, apply_state)
end
def resolve(
%Event{type: type, state_key: state_key, prev_events: prev_event_ids} = event,
room_events,
apply_state
) do
state_sets =
prev_event_ids
|> Enum.map(&room_events[&1])
|> Enum.map(&resolve(&1, room_events, true))
resolved_state = do_resolve(state_sets, room_events)
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if apply_state and Event.is_state_event(event) do
Map.put(resolved_state, {type, state_key}, event)
else
resolved_state
end
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end
def do_resolve([], _), do: %{}
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def do_resolve(state_sets, room_events) do
{unconflicted_state_map, conflicted_state_set} = calculate_conflict(state_sets, room_events)
if MapSet.size(conflicted_state_set) == 0 do
unconflicted_state_map
else
do_resolve(state_sets, room_events, unconflicted_state_map, conflicted_state_set)
end
end
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def do_resolve(state_sets, room_events, unconflicted_state_map, conflicted_state_set) do
full_conflicted_set =
MapSet.union(conflicted_state_set, auth_difference(state_sets, room_events))
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conflicted_control_event_ids =
full_conflicted_set
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|> Enum.filter(&Event.is_control_event(room_events[&1]))
|> MapSet.new()
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conflicted_control_events_with_auth_ids =
conflicted_control_event_ids
|> Enum.map(&room_events[&1])
|> full_auth_chain(room_events)
|> MapSet.intersection(full_conflicted_set)
|> MapSet.union(conflicted_control_event_ids)
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sorted_control_events =
conflicted_control_events_with_auth_ids
|> Enum.map(&room_events[&1])
|> Enum.sort(rev_top_pow_order(room_events))
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partial_resolved_state =
iterative_auth_checks(sorted_control_events, unconflicted_state_map, room_events)
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resolved_power_levels = partial_resolved_state[{"m.room.power_levels", ""}]
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conflicted_control_events_with_auth_ids
|> MapSet.difference(full_conflicted_set)
|> Enum.sort(mainline_order(resolved_power_levels, room_events))
|> Enum.map(&room_events[&1])
|> iterative_auth_checks(partial_resolved_state, room_events)
|> Map.merge(unconflicted_state_map)
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end
def calculate_conflict(state_sets, room_events) do
{unconflicted, conflicted} =
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state_sets
|> Enum.flat_map(&Map.keys/1)
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|> MapSet.new()
|> Enum.into(%{}, fn state_pair ->
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events =
Enum.map(state_sets, fn
state_set when is_map_key(state_set, state_pair) -> state_set[state_pair].event_id
_ -> nil
end)
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|> MapSet.new()
{state_pair, events}
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end)
|> Enum.split_with(fn {_, event_ids} ->
MapSet.size(event_ids) == 1
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end)
unconflicted_state_map =
Enum.into(unconflicted, %{}, fn {state_pair, event_ids} ->
event_id = MapSet.to_list(event_ids) |> hd()
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{state_pair, room_events[event_id]}
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end)
conflicted_state_set =
Enum.reduce(conflicted, MapSet.new(), fn {_, events}, acc ->
MapSet.union(acc, events)
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end)
|> MapSet.delete(nil)
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{unconflicted_state_map, conflicted_state_set}
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end
def auth_difference(state_sets, room_events) do
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full_auth_chains =
Enum.map(state_sets, fn state_set ->
state_set
|> Map.values()
|> full_auth_chain(room_events)
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end)
auth_chain_union = Enum.reduce(full_auth_chains, MapSet.new(), &MapSet.union/2)
auth_chain_intersection = Enum.reduce(full_auth_chains, MapSet.new(), &MapSet.intersection/2)
MapSet.difference(auth_chain_union, auth_chain_intersection)
end
def full_auth_chain(events, room_events) do
events
|> Enum.map(&auth_chain(&1, room_events))
|> Enum.reduce(MapSet.new(), &MapSet.union/2)
end
def auth_chain(%Event{auth_events: auth_events}, room_events) do
auth_events
|> Enum.map(&room_events[&1])
|> Enum.reduce(MapSet.new(), fn %Event{event_id: auth_event_id} = auth_event, acc ->
auth_event
|> auth_chain(room_events)
|> MapSet.union(acc)
|> MapSet.put(auth_event_id)
end)
end
def rev_top_pow_order(room_events) do
fn %Event{origin_server_ts: timestamp1, event_id: event_id1} = event1,
%Event{origin_server_ts: timestamp2, event_id: event_id2} = event2 ->
power1 = get_power_level(event1, room_events)
power2 = get_power_level(event2, room_events)
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if power1 == power2 do
if timestamp1 == timestamp2 do
event_id1 <= event_id2
else
timestamp1 < timestamp2
end
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else
power1 < power2
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end
end
end
def get_power_level(%Event{sender: sender, auth_events: auth_event_ids}, room_events) do
pl_event_id =
Enum.find(auth_event_ids, fn id ->
room_events[id].type == "m.room.power_levels"
end)
case room_events[pl_event_id] do
%Event{content: %{"users" => pl_users}} -> Map.get(pl_users, sender, 0)
nil -> 0
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end
end
def mainline_order(event, room_events) do
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mainline_map =
event
|> mainline(room_events)
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|> Enum.with_index()
|> Enum.into(%{})
fn event_id1, event_id2 ->
%Event{origin_server_ts: timestamp1} = event1 = room_events[event_id1]
%Event{origin_server_ts: timestamp2} = event2 = room_events[event_id2]
mainline_depth1 = get_mainline_depth(mainline_map, event1, room_events)
mainline_depth2 = get_mainline_depth(mainline_map, event2, room_events)
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if mainline_depth1 == mainline_depth2 do
if timestamp1 == timestamp2 do
event_id1 <= event_id2
else
timestamp1 < timestamp2
end
else
mainline_depth1 < mainline_depth2
end
end
end
defp get_mainline_depth(mainline_map, event, room_events) do
mainline = mainline(event, room_events)
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result =
Enum.find_value(mainline, fn mainline_event ->
if Map.has_key?(mainline_map, mainline_event) do
{:ok, mainline_map[mainline_event]}
else
nil
end
end)
case result do
{:ok, index} -> -index
nil -> nil
end
end
def mainline(event, room_events) do
event
|> mainline([], room_events)
|> Enum.reverse()
end
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def mainline(%Event{auth_events: auth_event_ids} = event, acc, room_events) do
pl_event_id =
Enum.find(auth_event_ids, fn id ->
room_events[id].type == "m.room.power_levels"
end)
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case room_events[pl_event_id] do
%Event{} = pl_event -> mainline(pl_event, [event | acc], room_events)
nil -> [event | acc]
end
end
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def iterative_auth_checks(events, state_set, room_events) do
Enum.reduce(events, state_set, fn event, acc ->
if is_authorized2(event, acc, room_events), do: update_state_set(event, acc), else: acc
end)
end
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def update_state_set(
%Event{type: event_type, state_key: state_key} = event,
state_set
) do
Map.put(state_set, {event_type, state_key}, event)
end
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def is_authorized2(%Event{auth_events: auth_event_ids} = event, state_set, room_events) do
state_set =
auth_event_ids
|> Enum.map(&room_events[&1])
|> Enum.reduce(state_set, &update_state_set/2)
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is_authorized(event, state_set)
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end
# TODO: join and power levels events
def is_authorized(%Event{type: "m.room.create", prev_events: prev_events}, _),
do: prev_events == []
def is_authorized(
%Event{type: "m.room.member", content: %{"membership" => "join"}, state_key: user},
state_set
) do
allowed_to_join(user, state_set)
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end
def is_authorized(%Event{sender: sender} = event, state_set) do
in_room(sender, state_set) and
has_power_level(
sender,
get_power_levels(state_set),
get_event_power_level(event)
)
end
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def in_room(user, state_set) when is_map_key(state_set, {"m.room.member", user}) do
case state_set[{"m.room.member", user}].content["membership"] do
"join" -> true
_ -> false
end
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end
def in_room(_, _), do: false
def get_power_levels(state_set)
when is_map_key(state_set, {"m.room.power_levels", ""}) do
state_set[{"m.room.power_levels", ""}].content
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end
def get_power_levels(_), do: nil
def has_power_level(user, %{"users" => users}, level) do
Map.get(users, user, 0) >= level
end
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def has_power_level(_, _, _) do
true
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end
defp get_event_power_level(%Event{state_key: ""}), do: 0
defp get_event_power_level(_), do: 50
# No join rules specified, allow joining for room creator only.
def allowed_to_join(user, state_set)
when not is_map_key(state_set, {"m.room.join_rules", ""}) do
state_set[{"m.room.create", ""}].sender == user
end
def is_authorized_by_auth_events(%Event{auth_events: auth_event_ids} = event) do
# We assume the auth events are validated beforehand.
state_set =
Event
|> where([e], e.event_id in ^auth_event_ids)
|> Repo.all()
|> Enum.reduce(%{}, &update_state_set/2)
is_authorized(event, state_set)
end
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def resolve_forward_extremities(%Event{room_id: room_id}) do
room_events =
Event
|> where([e], e.room_id == ^room_id)
|> select([e], {e.event_id, e})
|> Repo.all()
|> Enum.into(%{})
Event
|> where([e], e.room_id == ^room_id)
|> join(:inner, [e], r in Room, on: e.room_id == r.id)
|> where([e, r], e.event_id == fragment("ANY(?)", r.forward_extremities))
|> Repo.all()
|> Enum.map(&resolve/1)
|> do_resolve(room_events)
end
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def testing do
%Event{content: content} = event = Event.power_levels("room1", "charlie")
event = %Event{event | content: %{content | "ban" => 0}}
event
|> Map.put(:prev_events, ["b", "fork"])
|> Map.put(:auth_events, ["create", "join_charlie", "b"])
end
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end