architex/lib/matrix_server/state_resolution.ex
2021-07-24 00:13:12 +02:00

347 lines
10 KiB
Elixir

defmodule MatrixServer.StateResolution do
import Ecto.Query
alias MatrixServer.{Repo, Event}
def example 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
def resolve(%Event{room_id: room_id} = event, apply_state \\ false) 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, event_id: event_id, prev_events: prev_event_ids},
room_events,
apply_state
) do
state_sets =
prev_event_ids
|> Enum.map(&room_events[&1])
|> Enum.map(&resolve(&1, room_events))
resolved_state = do_resolve(state_sets, room_events)
# TODO: check if state event
if apply_state do
Map.put(resolved_state, {type, state_key}, event_id)
else
resolved_state
end
end
def do_resolve([], _), do: %{}
def do_resolve(state_sets, room_events) do
{unconflicted_state_map, conflicted_state_set} = calculate_conflict(state_sets)
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
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))
conflicted_control_event_ids =
full_conflicted_set
|> Enum.filter(&is_control_event(&1, room_events))
|> MapSet.new()
conflicted_control_events_with_auth_ids =
conflicted_control_event_ids
|> MapSet.to_list()
|> full_auth_chain(room_events)
|> MapSet.intersection(full_conflicted_set)
|> MapSet.union(conflicted_control_event_ids)
sorted_control_events =
conflicted_control_events_with_auth_ids
|> Enum.map(&room_events[&1])
|> Enum.sort(rev_top_pow_order(room_events))
partial_resolved_state =
iterative_auth_checks(sorted_control_events, unconflicted_state_map, room_events)
resolved_power_levels = partial_resolved_state[{"m.room.power_levels", ""}]
conflicted_control_events_with_auth_ids
|> MapSet.difference(full_conflicted_set)
|> Enum.map(&room_events[&1])
|> Enum.sort(mainline_order(resolved_power_levels, room_events))
|> iterative_auth_checks(partial_resolved_state, room_events)
|> Map.merge(unconflicted_state_map)
end
def calculate_conflict(state_sets) do
{unconflicted, conflicted} =
state_sets
|> Enum.flat_map(&Map.keys/1)
|> MapSet.new()
|> Enum.into(%{}, fn state_pair ->
events =
Enum.map(state_sets, &Map.get(&1, state_pair))
|> MapSet.new()
{state_pair, events}
end)
|> Enum.split_with(fn {_, events} ->
MapSet.size(events) == 1
end)
unconflicted_state_map =
Enum.into(unconflicted, %{}, fn {state_pair, events} ->
event = MapSet.to_list(events) |> hd()
{state_pair, event}
end)
conflicted_state_set =
Enum.reduce(conflicted, MapSet.new(), fn {_, events}, acc ->
MapSet.union(acc, events)
end)
|> MapSet.delete(nil)
{unconflicted_state_map, conflicted_state_set}
end
def auth_difference(state_sets, room_events) do
# TODO: memoization possible
full_auth_chains =
Enum.map(state_sets, fn state_set ->
state_set
|> Map.values()
|> full_auth_chain(room_events)
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(event_ids, room_events) do
event_ids
|> Enum.map(&auth_chain(&1, room_events))
|> Enum.reduce(MapSet.new(), &MapSet.union/2)
end
def auth_chain(event_id, room_events) do
# TODO: handle when auth event is not found.
room_events[event_id].auth_events
|> Enum.reduce(MapSet.new(), fn auth_event_id, acc ->
auth_event_id
|> auth_chain(room_events)
|> MapSet.union(acc)
|> MapSet.put(auth_event_id)
end)
end
def is_control_event(event_id, room_events), do: is_control_event(room_events[event_id])
def is_control_event(%Event{type: "m.room.power_levels", state_key: ""}), do: true
def is_control_event(%Event{type: "m.room.join_rules", state_key: ""}), do: true
def is_control_event(%Event{
type: "m.room.member",
state_key: state_key,
sender: sender,
content: %{membership: membership}
})
when sender != state_key and membership in ["leave", "ban"],
do: true
def is_control_event(_), do: false
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)
if power1 == power2 do
if timestamp1 == timestamp2 do
event_id1 <= event_id2
else
timestamp1 < timestamp2
end
else
power1 < power2
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
end
end
def mainline_order(event_id, room_events) do
mainline_map =
room_events[event_id]
|> mainline(room_events)
|> Enum.with_index()
|> Enum.into(%{})
fn %Event{origin_server_ts: timestamp1, event_id: event_id1} = event1,
%Event{origin_server_ts: timestamp2, event_id: event_id2} = event2 ->
mainline_depth1 = get_mainline_depth(mainline_map, event1, room_events)
mainline_depth2 = get_mainline_depth(mainline_map, event2, room_events)
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)
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
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)
case room_events[pl_event_id] do
%Event{} = pl_event -> mainline(pl_event, [event | acc], room_events)
nil -> [event | acc]
end
end
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
def update_state_set(
%Event{type: event_type, state_key: state_key, event_id: event_id},
state_set
) do
Map.put(state_set, {event_type, state_key}, event_id)
end
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, fn %Event{
type: event_type,
state_key: state_key,
event_id: event_id
},
acc ->
Map.put_new(acc, {event_type, state_key}, event_id)
end)
is_authorized(event, state_set, room_events)
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,
room_events
) do
allowed_to_join(user, state_set, room_events)
end
def is_authorized(%Event{sender: sender} = event, state_set, room_events) do
in_room(sender, state_set, room_events) and
has_power_level(
sender,
get_power_levels(state_set, room_events),
get_event_power_level(event)
)
end
def in_room(user, state_set, room_events) when is_map_key(state_set, {"m.room.member", user}) do
event_id = state_set[{"m.room.member", user}]
case room_events[event_id].content["membership"] do
"join" -> true
_ -> false
end
end
def in_room(_, _, _), do: false
def get_power_levels(state_set, room_events)
when is_map_key(state_set, {"m.room.power_levels", ""}) do
event_id = state_set[{"m.room.power_levels", ""}]
room_events[event_id].content
end
def get_power_levels(_, _), do: nil
def has_power_level(user, %{"users" => users}, level) do
Map.get(users, user, 0) >= level
end
def has_power_level(_, _, _) do
true
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, room_events)
when not is_map_key(state_set, {"m.room.join_rules", ""}) do
event_id = state_set[{"m.room.create", ""}]
room_events[event_id].sender == user
end
end