split event_handler service

Signed-off-by: Jason Volk <jason@zemos.net>

src/service/rooms/event_handler/fetch_state.rs

@@ -0,0 +1,84 @@
+use std::{
+	collections::{hash_map, HashMap},
+	sync::Arc,
+};
+
+use conduit::{debug, implement, warn, Err, Error, PduEvent, Result};
+use futures::FutureExt;
+use ruma::{
+	api::federation::event::get_room_state_ids, events::StateEventType, EventId, RoomId, RoomVersionId, ServerName,
+};
+
+/// Call /state_ids to find out what the state at this pdu is. We trust the
+/// server's response to some extend (sic), but we still do a lot of checks
+/// on the events
+#[implement(super::Service)]
+#[tracing::instrument(skip(self, create_event, room_version_id))]
+pub(super) async fn fetch_state(
+	&self, origin: &ServerName, create_event: &PduEvent, room_id: &RoomId, room_version_id: &RoomVersionId,
+	event_id: &EventId,
+) -> Result<Option<HashMap<u64, Arc<EventId>>>> {
+	debug!("Fetching state ids");
+	let res = self
+		.services
+		.sending
+		.send_synapse_request(
+			origin,
+			get_room_state_ids::v1::Request {
+				room_id: room_id.to_owned(),
+				event_id: (*event_id).to_owned(),
+			},
+		)
+		.await
+		.inspect_err(|e| warn!("Fetching state for event failed: {e}"))?;
+
+	debug!("Fetching state events");
+	let collect = res
+		.pdu_ids
+		.iter()
+		.map(|x| Arc::from(&**x))
+		.collect::<Vec<_>>();
+
+	let state_vec = self
+		.fetch_and_handle_outliers(origin, &collect, create_event, room_id, room_version_id)
+		.boxed()
+		.await;
+
+	let mut state: HashMap<_, Arc<EventId>> = HashMap::with_capacity(state_vec.len());
+	for (pdu, _) in state_vec {
+		let state_key = pdu
+			.state_key
+			.clone()
+			.ok_or_else(|| Error::bad_database("Found non-state pdu in state events."))?;
+
+		let shortstatekey = self
+			.services
+			.short
+			.get_or_create_shortstatekey(&pdu.kind.to_string().into(), &state_key)
+			.await;
+
+		match state.entry(shortstatekey) {
+			hash_map::Entry::Vacant(v) => {
+				v.insert(Arc::from(&*pdu.event_id));
+			},
+			hash_map::Entry::Occupied(_) => {
+				return Err(Error::bad_database(
+					"State event's type and state_key combination exists multiple times.",
+				))
+			},
+		}
+	}
+
+	// The original create event must still be in the state
+	let create_shortstatekey = self
+		.services
+		.short
+		.get_shortstatekey(&StateEventType::RoomCreate, "")
+		.await?;
+
+	if state.get(&create_shortstatekey).map(AsRef::as_ref) != Some(&create_event.event_id) {
+		return Err!(Database("Incoming event refers to wrong create event."));
+	}
+
+	Ok(Some(state))
+}