chore(sync/v3): Remove unused imports

Also, don't take read receipts into consideration for lazy loading.
Synapse doesn't do this and they're making initial syncs very large.

pkg/conduwuit.service

@@ -63,7 +63,7 @@ Restart=on-failure
 RestartSec=5
 
 TimeoutStopSec=4m
-TimeoutStartSec=4m
+TimeoutStartSec=10m
 
 StartLimitInterval=1m
 StartLimitBurst=5

src/admin/query/account_data.rs

@@ -41,7 +41,7 @@ async fn changes_since(
 	let results: Vec<_> = self
 		.services
 		.account_data
-		.changes_since(room_id.as_deref(), &user_id, since, None)
+		.changes_since(room_id.as_deref(), &user_id, Some(since), None)
 		.collect()
 		.await;
 	let query_time = timer.elapsed();

src/api/client/keys.rs

@@ -389,7 +389,7 @@ pub(crate) async fn get_key_changes_route(
 	device_list_updates.extend(
 		services
 			.users
-			.keys_changed(sender_user, from, Some(to))
+			.keys_changed(sender_user, Some(from), Some(to))
 			.map(ToOwned::to_owned)
 			.collect::<Vec<_>>()
 			.await,
@@ -401,7 +401,7 @@ pub(crate) async fn get_key_changes_route(
 		device_list_updates.extend(
 			services
 				.users
-				.room_keys_changed(room_id, from, Some(to))
+				.room_keys_changed(room_id, Some(from), Some(to))
 				.map(|(user_id, _)| user_id)
 				.map(ToOwned::to_owned)
 				.collect::<Vec<_>>()

src/api/client/membership/knock.rs

@@ -5,7 +5,7 @@ use axum_client_ip::InsecureClientIp;
 use conduwuit::{
 	Err, Result, debug, debug_info, debug_warn, err, info,
 	matrix::{
-		event::{Event, gen_event_id},
+		event::gen_event_id,
 		pdu::{PduBuilder, PduEvent},
 	},
 	result::FlatOk,
@@ -458,7 +458,7 @@ async fn knock_room_helper_local(
 			.await,
 	};
 
-	let send_knock_response = services
+	services
 		.sending
 		.send_federation_request(&remote_server, send_knock_request)
 		.await?;
@@ -477,20 +477,14 @@ async fn knock_room_helper_local(
 		.map_err(|e| err!(BadServerResponse("Invalid knock event PDU: {e:?}")))?;
 
 	info!("Updating membership locally to knock state with provided stripped state events");
+	// TODO: this call does not appear to do anything because `update_membership`
+	// doesn't call `mark_as_knock`. investigate further, ideally with the aim of
+	// removing this call entirely -- Ginger thinks `update_membership` should only
+	// be called from `force_state` and `append_pdu`.
 	services
 		.rooms
 		.state_cache
-		.update_membership(
-			room_id,
-			sender_user,
-			parsed_knock_pdu
-				.get_content::<RoomMemberEventContent>()
-				.expect("we just created this"),
-			sender_user,
-			Some(send_knock_response.knock_room_state),
-			None,
-			false,
-		)
+		.update_membership(room_id, sender_user, &parsed_knock_pdu, false)
 		.await?;
 
 	info!("Appending room knock event locally");
@@ -677,20 +671,11 @@ async fn knock_room_helper_remote(
 		.await?;
 
 	info!("Updating membership locally to knock state with provided stripped state events");
+	// TODO: see TODO on the other call to `update_membership`
 	services
 		.rooms
 		.state_cache
-		.update_membership(
-			room_id,
-			sender_user,
-			parsed_knock_pdu
-				.get_content::<RoomMemberEventContent>()
-				.expect("we just created this"),
-			sender_user,
-			Some(send_knock_response.knock_room_state),
-			None,
-			false,
-		)
+		.update_membership(room_id, sender_user, &parsed_knock_pdu, false)
 		.await?;
 
 	info!("Appending room knock event locally");

src/api/client/membership/leave.rs

@@ -2,12 +2,12 @@ use std::collections::HashSet;
 
 use axum::extract::State;
 use conduwuit::{
-	Err, Result, debug_info, debug_warn, err,
+	Err, Pdu, Result, debug_info, debug_warn, err,
 	matrix::{event::gen_event_id, pdu::PduBuilder},
 	utils::{self, FutureBoolExt, future::ReadyEqExt},
 	warn,
 };
-use futures::{FutureExt, StreamExt, TryFutureExt, pin_mut};
+use futures::{FutureExt, StreamExt, pin_mut};
 use ruma::{
 	CanonicalJsonObject, CanonicalJsonValue, OwnedServerName, RoomId, RoomVersionId, UserId,
 	api::{
@@ -81,42 +81,9 @@ pub async fn leave_room(
 	room_id: &RoomId,
 	reason: Option<String>,
 ) -> Result {
-	let default_member_content = RoomMemberEventContent {
-		membership: MembershipState::Leave,
-		reason: reason.clone(),
-		join_authorized_via_users_server: None,
-		is_direct: None,
-		avatar_url: None,
-		displayname: None,
-		third_party_invite: None,
-		blurhash: None,
-		redact_events: None,
-	};
-
 	let is_banned = services.rooms.metadata.is_banned(room_id);
 	let is_disabled = services.rooms.metadata.is_disabled(room_id);
 
-	pin_mut!(is_banned, is_disabled);
-	if is_banned.or(is_disabled).await {
-		// the room is banned/disabled, the room must be rejected locally since we
-		// cant/dont want to federate with this server
-		services
-			.rooms
-			.state_cache
-			.update_membership(
-				room_id,
-				user_id,
-				default_member_content,
-				user_id,
-				None,
-				None,
-				true,
-			)
-			.await?;
-
-		return Ok(());
-	}
-
 	let dont_have_room = services
 		.rooms
 		.state_cache
@@ -129,44 +96,41 @@ pub async fn leave_room(
 		.is_knocked(user_id, room_id)
 		.eq(&false);
 
-	// Ask a remote server if we don't have this room and are not knocking on it
-	if dont_have_room.and(not_knocked).await {
-		if let Err(e) =
-			remote_leave_room(services, user_id, room_id, reason.clone(), HashSet::new())
-				.boxed()
-				.await
-		{
-			warn!(%user_id, "Failed to leave room {room_id} remotely: {e}");
-			// Don't tell the client about this error
-		}
+	pin_mut!(is_banned, is_disabled);
 
-		let last_state = services
-			.rooms
-			.state_cache
-			.invite_state(user_id, room_id)
-			.or_else(|_| services.rooms.state_cache.knock_state(user_id, room_id))
-			.or_else(|_| services.rooms.state_cache.left_state(user_id, room_id))
+	/*
+	there are three possible cases when leaving a room:
+	1. the room is banned or disabled, so we're not federating with it.
+	2. nobody on the homeserver is in the room, which can happen if the user is rejecting an invite
+	   to a room that we don't have any members in.
+	3. someone else on the homeserver is in the room. in this case we can leave like normal by sending a PDU over federation.
+
+	in cases 1 and 2, we have to update the state cache using `mark_as_left` directly.
+	otherwise `build_and_append_pdu` will take care of updating the state cache for us.
+	*/
+
+	// `leave_pdu` is the outlier `m.room.member` event which will be synced to the
+	// user. if it's None the sync handler will create a dummy PDU.
+	let leave_pdu = if is_banned.or(is_disabled).await {
+		// case 1: the room is banned/disabled. we don't want to federate with another
+		// server to leave, so we can't create an outlier PDU.
+		None
+	} else if dont_have_room.and(not_knocked).await {
+		// case 2: ask a remote server to assist us with leaving
+		// we always mark the room as left locally, regardless of if the federated leave
+		// failed
+
+		remote_leave_room(services, user_id, room_id, reason.clone(), HashSet::new())
 			.await
-			.ok();
-
-		// We always drop the invite, we can't rely on other servers
-		services
-			.rooms
-			.state_cache
-			.update_membership(
-				room_id,
-				user_id,
-				default_member_content,
-				user_id,
-				last_state,
-				None,
-				true,
-			)
-			.await?;
+			.inspect_err(|err| {
+				warn!(%user_id, "Failed to leave room {room_id} remotely: {err}");
+			})
+			.ok()
 	} else {
+		// case 3: we can leave by sending a PDU.
 		let state_lock = services.rooms.state.mutex.lock(room_id).await;
 
-		let Ok(event) = services
+		let user_member_event_content = services
 			.rooms
 			.state_accessor
 			.room_state_get_content::<RoomMemberEventContent>(
@@ -174,44 +138,61 @@ pub async fn leave_room(
 				&StateEventType::RoomMember,
 				user_id.as_str(),
 			)
-			.await
-		else {
-			debug_warn!(
-				"Trying to leave a room you are not a member of, marking room as left locally."
-			);
+			.await;
 
-			return services
-				.rooms
-				.state_cache
-				.update_membership(
-					room_id,
-					user_id,
-					default_member_content,
-					user_id,
-					None,
-					None,
-					true,
-				)
-				.await;
-		};
+		match user_member_event_content {
+			| Ok(content) => {
+				services
+					.rooms
+					.timeline
+					.build_and_append_pdu(
+						PduBuilder::state(user_id.to_string(), &RoomMemberEventContent {
+							membership: MembershipState::Leave,
+							reason,
+							join_authorized_via_users_server: None,
+							is_direct: None,
+							..content
+						}),
+						user_id,
+						Some(room_id),
+						&state_lock,
+					)
+					.await?;
 
-		services
-			.rooms
-			.timeline
-			.build_and_append_pdu(
-				PduBuilder::state(user_id.to_string(), &RoomMemberEventContent {
-					membership: MembershipState::Leave,
-					reason,
-					join_authorized_via_users_server: None,
-					is_direct: None,
-					..event
-				}),
-				user_id,
-				Some(room_id),
-				&state_lock,
-			)
-			.await?;
-	}
+				// `build_and_append_pdu` calls `mark_as_left` internally, so we return early.
+				return Ok(());
+			},
+			| Err(_) => {
+				// an exception to case 3 is if the user isn't even in the room they're trying
+				// to leave. this can happen if the client's caching is wrong.
+				debug_warn!(
+					"Trying to leave a room you are not a member of, marking room as left \
+					 locally."
+				);
+
+				// return the existing leave state, if one exists. `mark_as_left` will then
+				// update the `roomuserid_leftcount` table, making the leave come down sync
+				// again.
+				services
+					.rooms
+					.state_cache
+					.left_state(user_id, room_id)
+					.await?
+			},
+		}
+	};
+
+	services
+		.rooms
+		.state_cache
+		.mark_as_left(user_id, room_id, leave_pdu)
+		.await;
+
+	services
+		.rooms
+		.state_cache
+		.update_joined_count(room_id)
+		.await;
 
 	Ok(())
 }
@@ -222,7 +203,7 @@ pub async fn remote_leave_room<S: ::std::hash::BuildHasher>(
 	room_id: &RoomId,
 	reason: Option<String>,
 	mut servers: HashSet<OwnedServerName, S>,
-) -> Result<()> {
+) -> Result<Pdu> {
 	let mut make_leave_response_and_server =
 		Err!(BadServerResponse("No remote server available to assist in leaving {room_id}."));
 
@@ -393,7 +374,7 @@ pub async fn remote_leave_room<S: ::std::hash::BuildHasher>(
 			&remote_server,
 			federation::membership::create_leave_event::v2::Request {
 				room_id: room_id.to_owned(),
-				event_id,
+				event_id: event_id.clone(),
 				pdu: services
 					.sending
 					.convert_to_outgoing_federation_event(leave_event.clone())
@@ -402,5 +383,14 @@ pub async fn remote_leave_room<S: ::std::hash::BuildHasher>(
 		)
 		.await?;
 
-	Ok(())
+	services
+		.rooms
+		.outlier
+		.add_pdu_outlier(&event_id, &leave_event);
+
+	let leave_pdu = Pdu::from_id_val(&event_id, leave_event).map_err(|e| {
+		err!(BadServerResponse("Invalid leave PDU received during federated leave: {e:?}"))
+	})?;
+
+	Ok(leave_pdu)
 }

src/api/client/message.rs

@@ -16,7 +16,7 @@ use conduwuit_service::{
 	Services,
 	rooms::{
 		lazy_loading,
-		lazy_loading::{Options, Witness},
+		lazy_loading::{MemberSet, Options},
 		timeline::PdusIterItem,
 	},
 };
@@ -162,7 +162,7 @@ pub(crate) async fn get_message_events_route(
 
 	let state = witness
 		.map(Option::into_iter)
-		.map(|option| option.flat_map(Witness::into_iter))
+		.map(|option| option.flat_map(MemberSet::into_iter))
 		.map(IterStream::stream)
 		.into_stream()
 		.flatten()
@@ -192,7 +192,7 @@ pub(crate) async fn lazy_loading_witness<'a, I>(
 	services: &Services,
 	lazy_loading_context: &lazy_loading::Context<'_>,
 	events: I,
-) -> Witness
+) -> MemberSet
 where
 	I: Iterator<Item = &'a PdusIterItem> + Clone + Send,
 {
@@ -213,10 +213,10 @@ where
 	let receipts = services
 		.rooms
 		.read_receipt
-		.readreceipts_since(lazy_loading_context.room_id, oldest.into_unsigned());
+		.readreceipts_since(lazy_loading_context.room_id, Some(oldest.into_unsigned()));
 
 	pin_mut!(receipts);
-	let witness: Witness = events
+	let witness: MemberSet = events
 		.stream()
 		.map(ref_at!(1))
 		.map(Event::sender)
@@ -224,7 +224,7 @@ where
 		.chain(
 			receipts
 				.ready_take_while(|(_, c, _)| *c <= newest.into_unsigned())
-				.map(|(user_id, ..)| user_id.to_owned()),
+				.map(|(user_id, ..)| user_id),
 		)
 		.collect()
 		.await;
@@ -232,7 +232,7 @@ where
 	services
 		.rooms
 		.lazy_loading
-		.witness_retain(witness, lazy_loading_context)
+		.retain_lazy_members(witness, lazy_loading_context)
 		.await
 }
 

src/api/client/sync/mod.rs

@@ -1,65 +1,123 @@
 mod v3;
-mod v4;
 mod v5;
 
+use std::collections::VecDeque;
+
 use conduwuit::{
-	Error, PduCount, Result,
+	Event, PduCount, Result, err,
 	matrix::pdu::PduEvent,
+	ref_at, trace,
 	utils::stream::{BroadbandExt, ReadyExt, TryIgnore},
 };
 use conduwuit_service::Services;
-use futures::{StreamExt, pin_mut};
+use futures::StreamExt;
 use ruma::{
-	RoomId, UserId,
+	OwnedUserId, RoomId, UserId,
 	events::TimelineEventType::{
 		self, Beacon, CallInvite, PollStart, RoomEncrypted, RoomMessage, Sticker,
 	},
 };
 
-pub(crate) use self::{
-	v3::sync_events_route, v4::sync_events_v4_route, v5::sync_events_v5_route,
-};
+pub(crate) use self::{v3::sync_events_route, v5::sync_events_v5_route};
 
 pub(crate) const DEFAULT_BUMP_TYPES: &[TimelineEventType; 6] =
 	&[CallInvite, PollStart, Beacon, RoomEncrypted, RoomMessage, Sticker];
 
+#[derive(Default)]
+pub(crate) struct TimelinePdus {
+	pub pdus: VecDeque<(PduCount, PduEvent)>,
+	pub limited: bool,
+}
+
+impl TimelinePdus {
+	fn senders(&self) -> impl Iterator<Item = OwnedUserId> {
+		self.pdus
+			.iter()
+			.map(ref_at!(1))
+			.map(Event::sender)
+			.map(Into::into)
+	}
+}
+
+/// Load up to `limit` PDUs in the range (starting_count, ending_count].
 async fn load_timeline(
 	services: &Services,
 	sender_user: &UserId,
 	room_id: &RoomId,
-	roomsincecount: PduCount,
-	next_batch: Option<PduCount>,
+	starting_count: Option<PduCount>,
+	ending_count: Option<PduCount>,
 	limit: usize,
-) -> Result<(Vec<(PduCount, PduEvent)>, bool), Error> {
-	let last_timeline_count = services
-		.rooms
-		.timeline
-		.last_timeline_count(Some(sender_user), room_id)
-		.await?;
+) -> Result<TimelinePdus> {
+	let mut pdu_stream = match starting_count {
+		| Some(starting_count) => {
+			let last_timeline_count = services
+				.rooms
+				.timeline
+				.last_timeline_count(Some(sender_user), room_id)
+				.await
+				.map_err(|err| {
+					err!(Database(warn!("Failed to fetch end of room timeline: {}", err)))
+				})?;
 
-	if last_timeline_count <= roomsincecount {
-		return Ok((Vec::new(), false));
-	}
+			if last_timeline_count <= starting_count {
+				// no messages have been sent in this room since `starting_count`
+				return Ok(TimelinePdus::default());
+			}
 
-	let non_timeline_pdus = services
-		.rooms
-		.timeline
-		.pdus_rev(Some(sender_user), room_id, None)
-		.ignore_err()
-		.ready_skip_while(|&(pducount, _)| pducount > next_batch.unwrap_or_else(PduCount::max))
-		.ready_take_while(|&(pducount, _)| pducount > roomsincecount);
+			// for incremental sync, stream from the DB all PDUs which were sent after
+			// `starting_count` but before `ending_count`, including `ending_count` but
+			// not `starting_count`. this code is pretty similar to the initial sync
+			// branch, they're separate to allow for future optimization
+			services
+				.rooms
+				.timeline
+				.pdus_rev(
+					Some(sender_user),
+					room_id,
+					ending_count.map(|count| count.saturating_add(1)),
+				)
+				.ignore_err()
+				.ready_take_while(move |&(pducount, _)| pducount > starting_count)
+				.boxed()
+		},
+		| None => {
+			// For initial sync, stream from the DB all PDUs before and including
+			// `ending_count` in reverse order
+			services
+				.rooms
+				.timeline
+				.pdus_rev(
+					Some(sender_user),
+					room_id,
+					ending_count.map(|count| count.saturating_add(1)),
+				)
+				.ignore_err()
+				.boxed()
+		},
+	};
 
-	// Take the last events for the timeline
-	pin_mut!(non_timeline_pdus);
-	let timeline_pdus: Vec<_> = non_timeline_pdus.by_ref().take(limit).collect().await;
+	// Return at most `limit` PDUs from the stream
+	let pdus = pdu_stream
+		.by_ref()
+		.take(limit)
+		.ready_fold(VecDeque::with_capacity(limit), |mut pdus, item| {
+			pdus.push_front(item);
+			pdus
+		})
+		.await;
 
-	let timeline_pdus: Vec<_> = timeline_pdus.into_iter().rev().collect();
+	// The timeline is limited if there are still more PDUs in the stream
+	let limited = pdu_stream.next().await.is_some();
 
-	// They /sync response doesn't always return all messages, so we say the output
-	// is limited unless there are events in non_timeline_pdus
-	let limited = non_timeline_pdus.next().await.is_some();
+	trace!(
+		"syncing {:?} timeline pdus from {:?} to {:?} (limited = {:?})",
+		pdus.len(),
+		starting_count,
+		ending_count,
+		limited,
+	);
 
-	Ok((timeline_pdus, limited))
+	Ok(TimelinePdus { pdus, limited })
 }
 
 async fn share_encrypted_room(

src/api/client/sync/v3/joined.rs

@@ -0,0 +1,852 @@
+use std::collections::{BTreeMap, HashSet};
+
+use conduwuit::{
+	Result, at, debug_warn, err, extract_variant,
+	matrix::{
+		Event,
+		pdu::{PduCount, PduEvent},
+	},
+	trace,
+	utils::{
+		BoolExt, IterStream, ReadyExt, TryFutureExtExt,
+		math::ruma_from_u64,
+		stream::{TryIgnore, WidebandExt},
+	},
+	warn,
+};
+use conduwuit_service::Services;
+use futures::{
+	FutureExt, StreamExt, TryFutureExt,
+	future::{OptionFuture, join, join3, join4, try_join, try_join3},
+};
+use ruma::{
+	OwnedRoomId, OwnedUserId, RoomId, UserId,
+	api::client::sync::sync_events::{
+		UnreadNotificationsCount,
+		v3::{Ephemeral, JoinedRoom, RoomAccountData, RoomSummary, State as RoomState, Timeline},
+	},
+	events::{
+		AnyRawAccountDataEvent, StateEventType,
+		TimelineEventType::*,
+		room::member::{MembershipState, RoomMemberEventContent},
+	},
+	serde::Raw,
+	uint,
+};
+use service::rooms::short::ShortStateHash;
+
+use super::{load_timeline, share_encrypted_room};
+use crate::client::{
+	TimelinePdus, ignored_filter,
+	sync::v3::{
+		DEFAULT_TIMELINE_LIMIT, DeviceListUpdates, SyncContext, prepare_lazily_loaded_members,
+		state::{build_state_incremental, build_state_initial},
+	},
+};
+
+/// Generate the sync response for a room the user is joined to.
+#[tracing::instrument(
+	name = "joined",
+	level = "debug",
+	skip_all,
+	fields(
+		room_id = ?room_id,
+		syncing_user = ?sync_context.syncing_user,
+	),
+)]
+pub(super) async fn load_joined_room(
+	services: &Services,
+	sync_context: SyncContext<'_>,
+	ref room_id: OwnedRoomId,
+) -> Result<(JoinedRoom, DeviceListUpdates)> {
+	/*
+	Building a sync response involves many steps which all depend on each other.
+	To parallelize the process as much as possible, each step is divided into its own function,
+	and `join*` functions are used to perform steps in parallel which do not depend on each other.
+	*/
+
+	let (
+		account_data,
+		ephemeral,
+		StateAndTimeline {
+			state_events,
+			timeline,
+			summary,
+			notification_counts,
+			device_list_updates,
+		},
+	) = try_join3(
+		build_account_data(services, sync_context, room_id),
+		build_ephemeral(services, sync_context, room_id),
+		build_state_and_timeline(services, sync_context, room_id),
+	)
+	.boxed()
+	.await?;
+
+	if !timeline.is_empty() || !state_events.is_empty() {
+		trace!(
+			"syncing {} timeline events (limited = {}) and {} state events",
+			timeline.events.len(),
+			timeline.limited,
+			state_events.len()
+		);
+	}
+
+	let joined_room = JoinedRoom {
+		account_data,
+		summary: summary.unwrap_or_default(),
+		unread_notifications: notification_counts.unwrap_or_default(),
+		timeline,
+		state: RoomState {
+			events: state_events.into_iter().map(Event::into_format).collect(),
+		},
+		ephemeral,
+		unread_thread_notifications: BTreeMap::new(),
+	};
+
+	Ok((joined_room, device_list_updates))
+}
+
+/// Collect changes to the syncing user's account data events.
+#[tracing::instrument(level = "debug", skip_all)]
+async fn build_account_data(
+	services: &Services,
+	SyncContext {
+		syncing_user,
+		last_sync_end_count,
+		current_count,
+		..
+	}: SyncContext<'_>,
+	room_id: &RoomId,
+) -> Result<RoomAccountData> {
+	let account_data_changes = services
+		.account_data
+		.changes_since(Some(room_id), syncing_user, last_sync_end_count, Some(current_count))
+		.ready_filter_map(|e| extract_variant!(e, AnyRawAccountDataEvent::Room))
+		.collect()
+		.await;
+
+	Ok(RoomAccountData { events: account_data_changes })
+}
+
+/// Collect new ephemeral events.
+#[tracing::instrument(level = "debug", skip_all)]
+async fn build_ephemeral(
+	services: &Services,
+	SyncContext { syncing_user, last_sync_end_count, .. }: SyncContext<'_>,
+	room_id: &RoomId,
+) -> Result<Ephemeral> {
+	// note: some of the futures below are boxed. this is because, without the box,
+	// rustc produces over thirty inscrutable errors in `mod.rs` at the call-site
+	// of `load_joined_room`. I don't know why boxing them fixes this -- it seems
+	// to be related to the async closures and borrowing from the sync context.
+
+	// collect updates to read receipts
+	let receipt_events = services
+		.rooms
+		.read_receipt
+		.readreceipts_since(room_id, last_sync_end_count)
+		.filter_map(async |(read_user, _, edu)| {
+			let is_ignored = services
+				.users
+				.user_is_ignored(&read_user, syncing_user)
+				.await;
+
+			// filter out read receipts for ignored users
+			is_ignored.or_some(edu)
+		})
+		.collect::<Vec<_>>()
+		.boxed();
+
+	// collect the updated list of typing users, if it's changed
+	let typing_event = async {
+		let should_send_typing_event = match last_sync_end_count {
+			| Some(last_sync_end_count) => {
+				match services.rooms.typing.last_typing_update(room_id).await {
+					| Ok(last_typing_update) => {
+						// update the typing list if the users typing have changed since the last
+						// sync
+						last_typing_update > last_sync_end_count
+					},
+					| Err(err) => {
+						warn!("Error checking last typing update: {}", err);
+						return None;
+					},
+				}
+			},
+			// always update the typing list on an initial sync
+			| None => true,
+		};
+
+		if should_send_typing_event {
+			let event = services
+				.rooms
+				.typing
+				.typings_event_for_user(room_id, syncing_user)
+				.await;
+
+			if let Ok(event) = event {
+				return Some(
+					Raw::new(&event)
+						.expect("typing event should be valid")
+						.cast(),
+				);
+			}
+		}
+
+		None
+	};
+
+	// collect the syncing user's private-read marker, if it's changed
+	let private_read_event = async {
+		let should_send_private_read = match last_sync_end_count {
+			| Some(last_sync_end_count) => {
+				let last_privateread_update = services
+					.rooms
+					.read_receipt
+					.last_privateread_update(syncing_user, room_id)
+					.await;
+
+				// update the marker if it's changed since the last sync
+				last_privateread_update > last_sync_end_count
+			},
+			// always update the marker on an initial sync
+			| None => true,
+		};
+
+		if should_send_private_read {
+			services
+				.rooms
+				.read_receipt
+				.private_read_get(room_id, syncing_user)
+				.await
+				.ok()
+		} else {
+			None
+		}
+	};
+
+	let (receipt_events, typing_event, private_read_event) =
+		join3(receipt_events, typing_event, private_read_event).await;
+
+	let mut edus = receipt_events;
+	edus.extend(typing_event);
+	edus.extend(private_read_event);
+
+	Ok(Ephemeral { events: edus })
+}
+
+/// A struct to hold the state events, timeline, and other data which is
+/// computed from them.
+struct StateAndTimeline {
+	state_events: Vec<PduEvent>,
+	timeline: Timeline,
+	summary: Option<RoomSummary>,
+	notification_counts: Option<UnreadNotificationsCount>,
+	device_list_updates: DeviceListUpdates,
+}
+
+/// Compute changes to the room's state and timeline.
+#[tracing::instrument(level = "debug", skip_all)]
+async fn build_state_and_timeline(
+	services: &Services,
+	sync_context: SyncContext<'_>,
+	room_id: &RoomId,
+) -> Result<StateAndTimeline> {
+	let (shortstatehashes, timeline) = try_join(
+		fetch_shortstatehashes(services, sync_context, room_id),
+		build_timeline(services, sync_context, room_id),
+	)
+	.await?;
+
+	let (state_events, notification_counts, joined_since_last_sync) = try_join3(
+		build_state_events(services, sync_context, room_id, shortstatehashes, &timeline),
+		build_notification_counts(services, sync_context, room_id, &timeline),
+		check_joined_since_last_sync(services, shortstatehashes, sync_context),
+	)
+	.await?;
+
+	// the timeline should always include at least one PDU if the syncing user
+	// joined since the last sync, that being the syncing user's join event. if
+	// it's empty something is wrong.
+	if joined_since_last_sync && timeline.pdus.is_empty() {
+		warn!("timeline for newly joined room is empty");
+	}
+
+	let (summary, device_list_updates) = try_join(
+		build_room_summary(
+			services,
+			sync_context,
+			room_id,
+			shortstatehashes,
+			&timeline,
+			&state_events,
+			joined_since_last_sync,
+		),
+		build_device_list_updates(
+			services,
+			sync_context,
+			room_id,
+			shortstatehashes,
+			&state_events,
+			joined_since_last_sync,
+		),
+	)
+	.await?;
+
+	// the token which may be passed to the messages endpoint to backfill room
+	// history
+	let prev_batch = timeline.pdus.front().map(at!(0));
+
+	// note: we always indicate a limited timeline if the syncing user just joined
+	// the room, to indicate to the client that it should request backfill (and to
+	// copy Synapse's behavior). for federated room joins, the `timeline` will
+	// usually only include the syncing user's join event.
+	let limited = timeline.limited || joined_since_last_sync;
+
+	// filter out ignored events from the timeline and convert the PDUs into Ruma's
+	// AnySyncTimelineEvent type
+	let filtered_timeline = timeline
+		.pdus
+		.into_iter()
+		.stream()
+		.wide_filter_map(|item| ignored_filter(services, item, sync_context.syncing_user))
+		.map(at!(1))
+		.map(Event::into_format)
+		.collect::<Vec<_>>()
+		.await;
+
+	Ok(StateAndTimeline {
+		state_events,
+		timeline: Timeline {
+			limited,
+			prev_batch: prev_batch.as_ref().map(ToString::to_string),
+			events: filtered_timeline,
+		},
+		summary,
+		notification_counts,
+		device_list_updates,
+	})
+}
+
+/// Shortstatehashes necessary to compute what state events to sync.
+#[derive(Clone, Copy)]
+struct ShortStateHashes {
+	/// The current state of the syncing room.
+	current_shortstatehash: ShortStateHash,
+	/// The state of the syncing room at the end of the last sync.
+	last_sync_end_shortstatehash: Option<ShortStateHash>,
+}
+
+/// Fetch the current_shortstatehash and last_sync_end_shortstatehash.
+#[tracing::instrument(level = "debug", skip_all)]
+async fn fetch_shortstatehashes(
+	services: &Services,
+	SyncContext { last_sync_end_count, current_count, .. }: SyncContext<'_>,
+	room_id: &RoomId,
+) -> Result<ShortStateHashes> {
+	// the room state currently.
+	// TODO: this should be the room state as of `current_count`, but there's no way
+	// to get that right now.
+	let current_shortstatehash = services
+		.rooms
+		.state
+		.get_room_shortstatehash(room_id)
+		.map_err(|_| err!(Database(error!("Room {room_id} has no state"))));
+
+	// the room state as of the end of the last sync.
+	// this will be None if we are doing an initial sync or if we just joined this
+	// room.
+	let last_sync_end_shortstatehash =
+		OptionFuture::from(last_sync_end_count.map(|last_sync_end_count| {
+			// look up the shortstatehash saved by the last sync's call to
+			// `associate_token_shortstatehash`
+			services
+				.rooms
+				.user
+				.get_token_shortstatehash(room_id, last_sync_end_count)
+				.inspect_err(move |_| {
+					debug_warn!(
+						token = last_sync_end_count,
+						"Room has no shortstatehash for this token"
+					);
+				})
+				.ok()
+		}))
+		.map(Option::flatten)
+		.map(Ok);
+
+	let (current_shortstatehash, last_sync_end_shortstatehash) =
+		try_join(current_shortstatehash, last_sync_end_shortstatehash).await?;
+
+	/*
+	associate the `current_count` with the `current_shortstatehash`, so we can
+	use it on the next sync as the `last_sync_end_shortstatehash`.
+
+	TODO: the table written to by this call grows extremely fast, gaining one new entry for each
+	joined room on _every single sync request_. we need to find a better way to remember the shortstatehash
+	between syncs.
+	*/
+	services
+		.rooms
+		.user
+		.associate_token_shortstatehash(room_id, current_count, current_shortstatehash)
+		.await;
+
+	Ok(ShortStateHashes {
+		current_shortstatehash,
+		last_sync_end_shortstatehash,
+	})
+}
+
+/// Fetch recent timeline events.
+#[tracing::instrument(level = "debug", skip_all)]
+async fn build_timeline(
+	services: &Services,
+	sync_context: SyncContext<'_>,
+	room_id: &RoomId,
+) -> Result<TimelinePdus> {
+	let SyncContext {
+		syncing_user,
+		last_sync_end_count,
+		current_count,
+		filter,
+		..
+	} = sync_context;
+
+	/*
+	determine the maximum number of events to return in this sync.
+	if the sync filter specifies a limit, that will be used, otherwise
+	`DEFAULT_TIMELINE_LIMIT` will be used. `DEFAULT_TIMELINE_LIMIT` will also be
+	used if the limit is somehow greater than usize::MAX.
+	*/
+	let timeline_limit = filter
+		.room
+		.timeline
+		.limit
+		.and_then(|limit| limit.try_into().ok())
+		.unwrap_or(DEFAULT_TIMELINE_LIMIT);
+
+	load_timeline(
+		services,
+		syncing_user,
+		room_id,
+		last_sync_end_count.map(PduCount::Normal),
+		Some(PduCount::Normal(current_count)),
+		timeline_limit,
+	)
+	.await
+}
+
+/// Calculate the state events to sync.
+async fn build_state_events(
+	services: &Services,
+	sync_context: SyncContext<'_>,
+	room_id: &RoomId,
+	shortstatehashes: ShortStateHashes,
+	timeline: &TimelinePdus,
+) -> Result<Vec<PduEvent>> {
+	let SyncContext {
+		syncing_user,
+		last_sync_end_count,
+		full_state,
+		..
+	} = sync_context;
+
+	let ShortStateHashes {
+		current_shortstatehash,
+		last_sync_end_shortstatehash,
+	} = shortstatehashes;
+
+	// the spec states that the `state` property only includes state events up to
+	// the beginning of the timeline, so we determine the state of the syncing room
+	// as of the first timeline event. NOTE: this explanation is not entirely
+	// accurate; see the implementation of `build_state_incremental`.
+	let timeline_start_shortstatehash = async {
+		if let Some((_, pdu)) = timeline.pdus.front() {
+			if let Ok(shortstatehash) = services
+				.rooms
+				.state_accessor
+				.pdu_shortstatehash(&pdu.event_id)
+				.await
+			{
+				return shortstatehash;
+			}
+		}
+
+		current_shortstatehash
+	};
+
+	// the user IDs of members whose membership needs to be sent to the client, if
+	// lazy-loading is enabled.
+	let lazily_loaded_members =
+		prepare_lazily_loaded_members(services, sync_context, room_id, timeline.senders());
+
+	let (timeline_start_shortstatehash, lazily_loaded_members) =
+		join(timeline_start_shortstatehash, lazily_loaded_members).await;
+
+	// compute the state delta between the previous sync and this sync.
+	match (last_sync_end_count, last_sync_end_shortstatehash) {
+		/*
+		if `last_sync_end_count` is Some (meaning this is an incremental sync), and `last_sync_end_shortstatehash`
+		is Some (meaning the syncing user didn't just join this room for the first time ever), and `full_state` is false,
+		then use `build_state_incremental`.
+		*/
+		| (Some(last_sync_end_count), Some(last_sync_end_shortstatehash)) if !full_state =>
+			build_state_incremental(
+				services,
+				syncing_user,
+				room_id,
+				PduCount::Normal(last_sync_end_count),
+				last_sync_end_shortstatehash,
+				timeline_start_shortstatehash,
+				current_shortstatehash,
+				timeline,
+				lazily_loaded_members.as_ref(),
+			)
+			.boxed()
+			.await,
+		/*
+		otherwise use `build_state_initial`. note that this branch will be taken if the user joined this room since the last sync
+		for the first time ever, because in that case we have no `last_sync_end_shortstatehash` and can't correctly calculate
+		the state using the incremental sync algorithm.
+		*/
+		| _ =>
+			build_state_initial(
+				services,
+				syncing_user,
+				timeline_start_shortstatehash,
+				lazily_loaded_members.as_ref(),
+			)
+			.boxed()
+			.await,
+	}
+}
+
+/// Compute the number of unread notifications in this room.
+#[tracing::instrument(level = "debug", skip_all)]
+async fn build_notification_counts(
+	services: &Services,
+	SyncContext { syncing_user, last_sync_end_count, .. }: SyncContext<'_>,
+	room_id: &RoomId,
+	timeline: &TimelinePdus,
+) -> Result<Option<UnreadNotificationsCount>> {
+	// determine whether to actually update the notification counts
+	let should_send_notification_counts = async {
+		// if we're going to sync some timeline events, the notification count has
+		// definitely changed to include them
+		if !timeline.pdus.is_empty() {
+			return true;
+		}
+
+		// if this is an initial sync, we need to send notification counts because the
+		// client doesn't know what they are yet
+		let Some(last_sync_end_count) = last_sync_end_count else {
+			return true;
+		};
+
+		let last_notification_read = services
+			.rooms
+			.user
+			.last_notification_read(syncing_user, room_id)
+			.await;
+
+		// if the syncing user has read the events we sent during the last sync, we need
+		// to send a new notification count on this sync.
+		if last_notification_read > last_sync_end_count {
+			return true;
+		}
+
+		// otherwise, nothing's changed.
+		false
+	};
+
+	if should_send_notification_counts.await {
+		let (notification_count, highlight_count) = join(
+			services
+				.rooms
+				.user
+				.notification_count(syncing_user, room_id)
+				.map(TryInto::try_into)
+				.unwrap_or(uint!(0)),
+			services
+				.rooms
+				.user
+				.highlight_count(syncing_user, room_id)
+				.map(TryInto::try_into)
+				.unwrap_or(uint!(0)),
+		)
+		.await;
+
+		trace!(?notification_count, ?highlight_count, "syncing new notification counts");
+
+		Ok(Some(UnreadNotificationsCount {
+			notification_count: Some(notification_count),
+			highlight_count: Some(highlight_count),
+		}))
+	} else {
+		Ok(None)
+	}
+}
+
+/// Check if the syncing user joined the room since their last incremental sync.
+#[tracing::instrument(level = "debug", skip_all)]
+async fn check_joined_since_last_sync(
+	services: &Services,
+	ShortStateHashes { last_sync_end_shortstatehash, .. }: ShortStateHashes,
+	SyncContext { syncing_user, .. }: SyncContext<'_>,
+) -> Result<bool> {
+	// fetch the syncing user's membership event during the last sync.
+	// this will be None if `previous_sync_end_shortstatehash` is None.
+	let membership_during_previous_sync = match last_sync_end_shortstatehash {
+		| Some(last_sync_end_shortstatehash) => services
+			.rooms
+			.state_accessor
+			.state_get_content(
+				last_sync_end_shortstatehash,
+				&StateEventType::RoomMember,
+				syncing_user.as_str(),
+			)
+			.await
+			.inspect_err(|_| debug_warn!("User has no previous membership"))
+			.ok(),
+		| None => None,
+	};
+
+	// TODO: If the requesting user got state-reset out of the room, this
+	// will be `true` when it shouldn't be. this function should never be called
+	// in that situation, but it may be if the membership cache didn't get updated.
+	// the root cause of this needs to be addressed
+	let joined_since_last_sync =
+		membership_during_previous_sync.is_none_or(|content: RoomMemberEventContent| {
+			content.membership != MembershipState::Join
+		});
+
+	if joined_since_last_sync {
+		trace!("user joined since last sync");
+	}
+
+	Ok(joined_since_last_sync)
+}
+
+/// Build the `summary` field of the room object, which includes
+/// the number of joined and invited users and the room's heroes.
+#[tracing::instrument(level = "debug", skip_all)]
+async fn build_room_summary(
+	services: &Services,
+	SyncContext { syncing_user, .. }: SyncContext<'_>,
+	room_id: &RoomId,
+	ShortStateHashes { current_shortstatehash, .. }: ShortStateHashes,
+	timeline: &TimelinePdus,
+	state_events: &[PduEvent],
+	joined_since_last_sync: bool,
+) -> Result<Option<RoomSummary>> {
+	// determine whether any events in the state or timeline are membership events.
+	let are_syncing_membership_events = timeline
+		.pdus
+		.iter()
+		.map(|(_, pdu)| pdu)
+		.chain(state_events.iter())
+		.any(|event| event.kind == RoomMember);
+
+	/*
+	we only need to send an updated room summary if:
+	1. there are membership events in the state or timeline, because they might have changed the
+	   membership counts or heroes, or
+	2. the syncing user just joined this room, which usually implies #1 because their join event should be in the timeline.
+	*/
+	if !(are_syncing_membership_events || joined_since_last_sync) {
+		return Ok(None);
+	}
+
+	let joined_member_count = services
+		.rooms
+		.state_cache
+		.room_joined_count(room_id)
+		.unwrap_or(0);
+
+	let invited_member_count = services
+		.rooms
+		.state_cache
+		.room_invited_count(room_id)
+		.unwrap_or(0);
+
+	let has_name = services
+		.rooms
+		.state_accessor
+		.state_contains_type(current_shortstatehash, &StateEventType::RoomName);
+
+	let has_canonical_alias = services
+		.rooms
+		.state_accessor
+		.state_contains_type(current_shortstatehash, &StateEventType::RoomCanonicalAlias);
+
+	let (joined_member_count, invited_member_count, has_name, has_canonical_alias) =
+		join4(joined_member_count, invited_member_count, has_name, has_canonical_alias).await;
+
+	// only send heroes if the room has neither a name nor a canonical alias
+	let heroes = if !(has_name || has_canonical_alias) {
+		Some(build_heroes(services, room_id, syncing_user, current_shortstatehash).await)
+	} else {
+		None
+	};
+
+	trace!(
+		?joined_member_count,
+		?invited_member_count,
+		heroes_length = heroes.as_ref().map(HashSet::len),
+		"syncing updated summary"
+	);
+
+	Ok(Some(RoomSummary {
+		heroes: heroes
+			.map(|heroes| heroes.into_iter().collect())
+			.unwrap_or_default(),
+		joined_member_count: Some(ruma_from_u64(joined_member_count)),
+		invited_member_count: Some(ruma_from_u64(invited_member_count)),
+	}))
+}
+
+/// Fetch the user IDs to include in the `m.heroes` property of the room
+/// summary.
+async fn build_heroes(
+	services: &Services,
+	room_id: &RoomId,
+	syncing_user: &UserId,
+	current_shortstatehash: ShortStateHash,
+) -> HashSet<OwnedUserId> {
+	const MAX_HERO_COUNT: usize = 5;
+
+	// fetch joined members from the state cache first
+	let joined_members_stream = services
+		.rooms
+		.state_cache
+		.room_members(room_id)
+		.map(ToOwned::to_owned);
+
+	// then fetch invited members
+	let invited_members_stream = services
+		.rooms
+		.state_cache
+		.room_members_invited(room_id)
+		.map(ToOwned::to_owned);
+
+	// then as a last resort fetch every membership event
+	let all_members_stream = services
+		.rooms
+		.short
+		.multi_get_statekey_from_short(
+			services
+				.rooms
+				.state_accessor
+				.state_full_shortids(current_shortstatehash)
+				.ignore_err()
+				.ready_filter_map(|(key, _)| Some(key)),
+		)
+		.ignore_err()
+		.ready_filter_map(|(event_type, state_key)| {
+			if event_type == StateEventType::RoomMember {
+				state_key.to_string().try_into().ok()
+			} else {
+				None
+			}
+		});
+
+	joined_members_stream
+		.chain(invited_members_stream)
+		.chain(all_members_stream)
+		// the hero list should never include the syncing user
+		.ready_filter(|user_id| user_id != syncing_user)
+		.take(MAX_HERO_COUNT)
+		.collect()
+		.await
+}
+
+/// Collect updates to users' device lists for E2EE.
+#[tracing::instrument(level = "debug", skip_all)]
+async fn build_device_list_updates(
+	services: &Services,
+	SyncContext {
+		syncing_user,
+		last_sync_end_count,
+		current_count,
+		..
+	}: SyncContext<'_>,
+	room_id: &RoomId,
+	ShortStateHashes { current_shortstatehash, .. }: ShortStateHashes,
+	state_events: &Vec<PduEvent>,
+	joined_since_last_sync: bool,
+) -> Result<DeviceListUpdates> {
+	let is_encrypted_room = services
+		.rooms
+		.state_accessor
+		.state_get(current_shortstatehash, &StateEventType::RoomEncryption, "")
+		.is_ok();
+
+	// initial syncs don't include device updates, and rooms which aren't encrypted
+	// don't affect them, so return early in either of those cases
+	if last_sync_end_count.is_none() || !(is_encrypted_room.await) {
+		return Ok(DeviceListUpdates::new());
+	}
+
+	let mut device_list_updates = DeviceListUpdates::new();
+
+	// add users with changed keys to the `changed` list
+	services
+		.users
+		.room_keys_changed(room_id, last_sync_end_count, Some(current_count))
+		.map(at!(0))
+		.map(ToOwned::to_owned)
+		.ready_for_each(|user_id| {
+			device_list_updates.changed.insert(user_id);
+		})
+		.await;
+
+	// add users who now share encrypted rooms to `changed` and
+	// users who no longer share encrypted rooms to `left`
+	for state_event in state_events {
+		if state_event.kind == RoomMember {
+			let Some(content): Option<RoomMemberEventContent> = state_event.get_content().ok()
+			else {
+				continue;
+			};
+
+			let Some(user_id): Option<OwnedUserId> = state_event
+				.state_key
+				.as_ref()
+				.and_then(|key| key.parse().ok())
+			else {
+				continue;
+			};
+
+			{
+				use MembershipState::*;
+
+				if matches!(content.membership, Leave | Join) {
+					let shares_encrypted_room =
+						share_encrypted_room(services, syncing_user, &user_id, Some(room_id))
+							.await;
+					match content.membership {
+						| Leave if !shares_encrypted_room => {
+							device_list_updates.left.insert(user_id);
+						},
+						| Join if joined_since_last_sync || shares_encrypted_room => {
+							device_list_updates.changed.insert(user_id);
+						},
+						| _ => (),
+					}
+				}
+			}
+		}
+	}
+
+	if !device_list_updates.is_empty() {
+		trace!(
+			changed = device_list_updates.changed.len(),
+			left = device_list_updates.left.len(),
+			"syncing device list updates"
+		);
+	}
+
+	Ok(device_list_updates)
+}

src/api/client/sync/v3/left.rs

@@ -0,0 +1,349 @@
+use conduwuit::{
+	Event, PduCount, PduEvent, Result, at, debug_warn,
+	pdu::EventHash,
+	trace,
+	utils::{self, IterStream, future::ReadyEqExt, stream::WidebandExt as _},
+};
+use futures::{StreamExt, future::join};
+use ruma::{
+	EventId, OwnedRoomId, RoomId,
+	api::client::sync::sync_events::v3::{LeftRoom, RoomAccountData, State, Timeline},
+	events::{StateEventType, TimelineEventType},
+	uint,
+};
+use serde_json::value::RawValue;
+use service::{Services, rooms::short::ShortStateHash};
+
+use crate::client::{
+	TimelinePdus, ignored_filter,
+	sync::{
+		load_timeline,
+		v3::{
+			DEFAULT_TIMELINE_LIMIT, SyncContext, prepare_lazily_loaded_members,
+			state::build_state_initial,
+		},
+	},
+};
+
+#[tracing::instrument(
+	name = "left",
+	level = "debug",
+	skip_all,
+	fields(
+		room_id = %room_id,
+	),
+)]
+#[allow(clippy::too_many_arguments)]
+pub(super) async fn load_left_room(
+	services: &Services,
+	sync_context: SyncContext<'_>,
+	ref room_id: OwnedRoomId,
+	leave_membership_event: Option<PduEvent>,
+) -> Result<Option<LeftRoom>> {
+	let SyncContext {
+		syncing_user,
+		last_sync_end_count,
+		current_count,
+		filter,
+		..
+	} = sync_context;
+
+	// the global count as of the moment the user left the room
+	let Some(left_count) = services
+		.rooms
+		.state_cache
+		.get_left_count(room_id, syncing_user)
+		.await
+		.ok()
+	else {
+		// if we get here, the membership cache is incorrect, likely due to a state
+		// reset
+		debug_warn!("attempting to sync left room but no left count exists");
+		return Ok(None);
+	};
+
+	// return early if we haven't gotten to this leave yet.
+	// this can happen if the user leaves while a sync response is being generated
+	if current_count < left_count {
+		return Ok(None);
+	}
+
+	// return early if this is an incremental sync, and we've already synced this
+	// leave to the user, and `include_leave` isn't set on the filter.
+	if !filter.room.include_leave && last_sync_end_count >= Some(left_count) {
+		return Ok(None);
+	}
+
+	if let Some(ref leave_membership_event) = leave_membership_event {
+		debug_assert_eq!(
+			leave_membership_event.kind,
+			TimelineEventType::RoomMember,
+			"leave PDU should be m.room.member"
+		);
+	}
+
+	let does_not_exist = services.rooms.metadata.exists(room_id).eq(&false).await;
+
+	let (timeline, state_events) = match leave_membership_event {
+		| Some(leave_membership_event) if does_not_exist => {
+			/*
+			we have none PDUs with left beef for this room, likely because it was a rejected invite to a room
+			which nobody on this homeserver is in. `leave_pdu` is the remote-assisted outlier leave event for the room,
+			which is all we can send to the client.
+
+			if this is an initial sync, don't include this room at all to keep the client from asking for
+			state that we don't have.
+			*/
+
+			if last_sync_end_count.is_none() {
+				return Ok(None);
+			}
+
+			trace!("syncing remote-assisted leave PDU");
+			(TimelinePdus::default(), vec![leave_membership_event])
+		},
+		| Some(leave_membership_event) => {
+			// we have this room in our DB, and can fetch the state and timeline from when
+			// the user left.
+
+			let leave_state_key = syncing_user;
+			debug_assert_eq!(
+				Some(leave_state_key.as_str()),
+				leave_membership_event.state_key(),
+				"leave PDU should be for the user requesting the sync"
+			);
+
+			// the shortstatehash of the state _immediately before_ the syncing user left
+			// this room. the state represented here _does not_ include
+			// `leave_membership_event`.
+			let leave_shortstatehash = services
+				.rooms
+				.state_accessor
+				.pdu_shortstatehash(&leave_membership_event.event_id)
+				.await?;
+
+			let prev_membership_event = services
+				.rooms
+				.state_accessor
+				.state_get(
+					leave_shortstatehash,
+					&StateEventType::RoomMember,
+					leave_state_key.as_str(),
+				)
+				.await?;
+
+			build_left_state_and_timeline(
+				services,
+				sync_context,
+				room_id,
+				leave_membership_event,
+				leave_shortstatehash,
+				prev_membership_event,
+			)
+			.await?
+		},
+		| None => {
+			/*
+			no leave event was actually sent in this room, but we still need to pretend
+			like the user left it. this is usually because the room was banned by a server admin.
+
+			if this is an incremental sync, generate a fake leave event to make the room vanish from clients.
+			otherwise we don't tell the client about this room at all.
+			*/
+			if last_sync_end_count.is_none() {
+				return Ok(None);
+			}
+
+			trace!("syncing dummy leave event");
+			(TimelinePdus::default(), vec![create_dummy_leave_event(
+				services,
+				sync_context,
+				room_id,
+			)])
+		},
+	};
+
+	let raw_timeline_pdus = timeline
+		.pdus
+		.into_iter()
+		.stream()
+		// filter out ignored events from the timeline
+		.wide_filter_map(|item| ignored_filter(services, item, syncing_user))
+		.map(at!(1))
+		.map(Event::into_format)
+		.collect::<Vec<_>>()
+		.await;
+
+	Ok(Some(LeftRoom {
+		account_data: RoomAccountData { events: Vec::new() },
+		timeline: Timeline {
+			limited: timeline.limited,
+			prev_batch: Some(current_count.to_string()),
+			events: raw_timeline_pdus,
+		},
+		state: State {
+			events: state_events.into_iter().map(Event::into_format).collect(),
+		},
+	}))
+}
+
+async fn build_left_state_and_timeline(
+	services: &Services,
+	sync_context: SyncContext<'_>,
+	room_id: &RoomId,
+	leave_membership_event: PduEvent,
+	leave_shortstatehash: ShortStateHash,
+	prev_membership_event: PduEvent,
+) -> Result<(TimelinePdus, Vec<PduEvent>)> {
+	let SyncContext {
+		syncing_user,
+		last_sync_end_count,
+		filter,
+		..
+	} = sync_context;
+
+	let timeline_start_count = if let Some(last_sync_end_count) = last_sync_end_count {
+		// for incremental syncs, start the timeline after `since`
+		PduCount::Normal(last_sync_end_count)
+	} else {
+		// for initial syncs, start the timeline after the previous membership
+		// event. we don't want to include the membership event itself
+		// because clients get confused when they see a `join`
+		// membership event in a `leave` room.
+		services
+			.rooms
+			.timeline
+			.get_pdu_count(&prev_membership_event.event_id)
+			.await?
+	};
+
+	// end the timeline at the user's leave event
+	let timeline_end_count = services
+		.rooms
+		.timeline
+		.get_pdu_count(leave_membership_event.event_id())
+		.await?;
+
+	// limit the timeline using the same logic as for joined rooms
+	let timeline_limit = filter
+		.room
+		.timeline
+		.limit
+		.and_then(|limit| limit.try_into().ok())
+		.unwrap_or(DEFAULT_TIMELINE_LIMIT);
+
+	let timeline = load_timeline(
+		services,
+		syncing_user,
+		room_id,
+		Some(timeline_start_count),
+		Some(timeline_end_count),
+		timeline_limit,
+	)
+	.await?;
+
+	let timeline_start_shortstatehash = async {
+		if let Some((_, pdu)) = timeline.pdus.front() {
+			if let Ok(shortstatehash) = services
+				.rooms
+				.state_accessor
+				.pdu_shortstatehash(&pdu.event_id)
+				.await
+			{
+				return shortstatehash;
+			}
+		}
+
+		// the timeline generally should not be empty (see the TODO further down),
+		// but in case it is we use `leave_shortstatehash` as the state to
+		// send
+		leave_shortstatehash
+	};
+
+	let lazily_loaded_members =
+		prepare_lazily_loaded_members(services, sync_context, room_id, timeline.senders());
+
+	let (timeline_start_shortstatehash, lazily_loaded_members) =
+		join(timeline_start_shortstatehash, lazily_loaded_members).await;
+
+	// TODO: calculate incremental state for incremental syncs.
+	// always calculating initial state _works_ but returns more data and does
+	// more processing than strictly necessary.
+	let mut state = build_state_initial(
+		services,
+		syncing_user,
+		timeline_start_shortstatehash,
+		lazily_loaded_members.as_ref(),
+	)
+	.await?;
+
+	/*
+	remove membership events for the syncing user from state.
+	usually, `state` should include a `join` membership event and `timeline` should include a `leave` one.
+	however, the matrix-js-sdk gets confused when this happens (see [1]) and doesn't process the room leave,
+	so we have to filter out the membership from `state`.
+
+	NOTE: we are sending more information than synapse does in this scenario, because we always
+	calculate `state` for initial syncs, even when the sync being performed is incremental.
+	however, the specification does not forbid sending extraneous events in `state`.
+
+	TODO: there is an additional bug at play here. sometimes `load_joined_room` syncs the `leave` event
+	before `load_left_room` does, which means the `timeline` we sync immediately after a leave is empty.
+	this shouldn't happen -- `timeline` should always include the `leave` event. this is probably
+	a race condition with the membership state cache.
+
+	[1]: https://github.com/matrix-org/matrix-js-sdk/issues/5071
+	*/
+
+	// `state` should only ever include one membership event for the syncing user
+	let membership_event_index = state.iter().position(|pdu| {
+		*pdu.event_type() == TimelineEventType::RoomMember
+			&& pdu.state_key() == Some(syncing_user.as_str())
+	});
+
+	if let Some(index) = membership_event_index {
+		// the ordering of events in `state` does not matter
+		state.swap_remove(index);
+	}
+
+	trace!(
+		?timeline_start_count,
+		?timeline_end_count,
+		"syncing {} timeline events (limited = {}) and {} state events",
+		timeline.pdus.len(),
+		timeline.limited,
+		state.len()
+	);
+
+	Ok((timeline, state))
+}
+
+fn create_dummy_leave_event(
+	services: &Services,
+	SyncContext { syncing_user, .. }: SyncContext<'_>,
+	room_id: &RoomId,
+) -> PduEvent {
+	// TODO: because this event ID is random, it could cause caching issues with
+	// clients. perhaps a database table could be created to hold these dummy
+	// events, or they could be stored as outliers?
+	PduEvent {
+		event_id: EventId::new(services.globals.server_name()),
+		sender: syncing_user.to_owned(),
+		origin: None,
+		origin_server_ts: utils::millis_since_unix_epoch()
+			.try_into()
+			.expect("Timestamp is valid js_int value"),
+		kind: TimelineEventType::RoomMember,
+		content: RawValue::from_string(r#"{"membership": "leave"}"#.to_owned()).unwrap(),
+		state_key: Some(syncing_user.as_str().into()),
+		unsigned: None,
+		// The following keys are dropped on conversion
+		room_id: Some(room_id.to_owned()),
+		prev_events: vec![],
+		depth: uint!(1),
+		auth_events: vec![],
+		redacts: None,
+		hashes: EventHash { sha256: String::new() },
+		signatures: None,
+	}
+}

src/api/client/sync/v3/mod.rs

@@ -0,0 +1,494 @@
+mod joined;
+mod left;
+mod state;
+
+use std::{
+	cmp::{self},
+	collections::{BTreeMap, HashMap, HashSet},
+	time::Duration,
+};
+
+use axum::extract::State;
+use conduwuit::{
+	Result, extract_variant,
+	utils::{
+		ReadyExt, TryFutureExtExt,
+		stream::{BroadbandExt, Tools, WidebandExt},
+	},
+	warn,
+};
+use conduwuit_service::Services;
+use futures::{
+	FutureExt, StreamExt, TryFutureExt,
+	future::{OptionFuture, join3, join4, join5},
+};
+use ruma::{
+	DeviceId, OwnedUserId, RoomId, UserId,
+	api::client::{
+		filter::FilterDefinition,
+		sync::sync_events::{
+			self, DeviceLists,
+			v3::{
+				Filter, GlobalAccountData, InviteState, InvitedRoom, KnockState, KnockedRoom,
+				Presence, Rooms, ToDevice,
+			},
+		},
+		uiaa::UiaaResponse,
+	},
+	events::{
+		AnyRawAccountDataEvent,
+		presence::{PresenceEvent, PresenceEventContent},
+	},
+	serde::Raw,
+};
+use service::rooms::lazy_loading::{self, MemberSet, Options as _};
+
+use super::{load_timeline, share_encrypted_room};
+use crate::{
+	Ruma, RumaResponse,
+	client::{
+		is_ignored_invite,
+		sync::v3::{joined::load_joined_room, left::load_left_room},
+	},
+};
+
+/// The default maximum number of events to return in the `timeline` key of
+/// joined and left rooms. If the number of events sent since the last sync
+/// exceeds this number, the `timeline` will be `limited`.
+const DEFAULT_TIMELINE_LIMIT: usize = 30;
+
+/// A collection of updates to users' device lists, used for E2EE.
+struct DeviceListUpdates {
+	changed: HashSet<OwnedUserId>,
+	left: HashSet<OwnedUserId>,
+}
+
+impl DeviceListUpdates {
+	fn new() -> Self {
+		Self {
+			changed: HashSet::new(),
+			left: HashSet::new(),
+		}
+	}
+
+	fn merge(&mut self, other: Self) {
+		self.changed.extend(other.changed);
+		self.left.extend(other.left);
+	}
+
+	fn is_empty(&self) -> bool { self.changed.is_empty() && self.left.is_empty() }
+}
+
+impl From<DeviceListUpdates> for DeviceLists {
+	fn from(val: DeviceListUpdates) -> Self {
+		Self {
+			changed: val.changed.into_iter().collect(),
+			left: val.left.into_iter().collect(),
+		}
+	}
+}
+
+/// References to common data needed to calculate the sync response.
+#[derive(Clone, Copy)]
+struct SyncContext<'a> {
+	/// The ID of the user requesting this sync.
+	syncing_user: &'a UserId,
+	/// The ID of the device requesting this sync, which will belong to
+	/// `syncing_user`.
+	syncing_device: &'a DeviceId,
+	/// The global count at the end of the previous sync response.
+	/// The previous sync's `current_count` will become the next sync's
+	/// `last_sync_end_count`. This will be None if no `since` query parameter
+	/// was specified, indicating an initial sync.
+	last_sync_end_count: Option<u64>,
+	/// The global count as of when we started building the sync response.
+	/// This is used as an upper bound when querying the database to ensure the
+	/// response represents a snapshot in time and doesn't include data which
+	/// appeared while the response was being built.
+	current_count: u64,
+	/// The `full_state` query parameter, used when syncing state for joined and
+	/// left rooms.
+	full_state: bool,
+	/// The sync filter, which the client uses to specify what data should be
+	/// included in the sync response.
+	filter: &'a FilterDefinition,
+}
+
+impl<'a> SyncContext<'a> {
+	fn lazy_loading_context(&self, room_id: &'a RoomId) -> lazy_loading::Context<'a> {
+		lazy_loading::Context {
+			user_id: self.syncing_user,
+			device_id: Some(self.syncing_device),
+			room_id,
+			token: self.last_sync_end_count,
+			options: Some(&self.filter.room.state.lazy_load_options),
+		}
+	}
+
+	#[inline]
+	fn lazy_loading_enabled(&self) -> bool {
+		(self.filter.room.state.lazy_load_options.is_enabled()
+			|| self.filter.room.timeline.lazy_load_options.is_enabled())
+			&& !self.full_state
+	}
+}
+
+type PresenceUpdates = HashMap<OwnedUserId, PresenceEventContent>;
+
+/// # `GET /_matrix/client/r0/sync`
+///
+/// Synchronize the client's state with the latest state on the server.
+///
+/// - This endpoint takes a `since` parameter which should be the `next_batch`
+///   value from a previous request for incremental syncs.
+///
+/// Calling this endpoint without a `since` parameter returns:
+/// - Some of the most recent events of each timeline
+/// - Notification counts for each room
+/// - Joined and invited member counts, heroes
+/// - All state events
+///
+/// Calling this endpoint with a `since` parameter from a previous `next_batch`
+/// returns: For joined rooms:
+/// - Some of the most recent events of each timeline that happened after since
+/// - If user joined the room after since: All state events (unless lazy loading
+///   is activated) and all device list updates in that room
+/// - If the user was already in the room: A list of all events that are in the
+///   state now, but were not in the state at `since`
+/// - If the state we send contains a member event: Joined and invited member
+///   counts, heroes
+/// - Device list updates that happened after `since`
+/// - If there are events in the timeline we send or the user send updated his
+///   read mark: Notification counts
+/// - EDUs that are active now (read receipts, typing updates, presence)
+/// - TODO: Allow multiple sync streams to support Pantalaimon
+///
+/// For invited rooms:
+/// - If the user was invited after `since`: A subset of the state of the room
+///   at the point of the invite
+///
+/// For left rooms:
+/// - If the user left after `since`: `prev_batch` token, empty state (TODO:
+///   subset of the state at the point of the leave)
+#[tracing::instrument(
+	name = "sync",
+	level = "debug",
+	skip_all,
+	fields(
+		since = %body.body.since.as_deref().unwrap_or_default(),
+    )
+)]
+pub(crate) async fn sync_events_route(
+	State(services): State<crate::State>,
+	body: Ruma<sync_events::v3::Request>,
+) -> Result<sync_events::v3::Response, RumaResponse<UiaaResponse>> {
+	let (sender_user, sender_device) = body.sender();
+
+	// Presence update
+	if services.config.allow_local_presence {
+		services
+			.presence
+			.ping_presence(sender_user, &body.body.set_presence)
+			.await?;
+	}
+
+	// Setup watchers, so if there's no response, we can wait for them
+	let watcher = services.sync.watch(sender_user, sender_device);
+
+	let response = build_sync_events(&services, &body).await?;
+	if body.body.full_state
+		|| !(response.rooms.is_empty()
+			&& response.presence.is_empty()
+			&& response.account_data.is_empty()
+			&& response.device_lists.is_empty()
+			&& response.to_device.is_empty())
+	{
+		return Ok(response);
+	}
+
+	// Hang a few seconds so requests are not spammed
+	// Stop hanging if new info arrives
+	let default = Duration::from_secs(30);
+	let duration = cmp::min(body.body.timeout.unwrap_or(default), default);
+	_ = tokio::time::timeout(duration, watcher).await;
+
+	// Retry returning data
+	build_sync_events(&services, &body).await
+}
+
+pub(crate) async fn build_sync_events(
+	services: &Services,
+	body: &Ruma<sync_events::v3::Request>,
+) -> Result<sync_events::v3::Response, RumaResponse<UiaaResponse>> {
+	let (syncing_user, syncing_device) = body.sender();
+
+	let current_count = services.globals.current_count()?;
+
+	// the `since` token is the last sync end count stringified
+	let last_sync_end_count = body
+		.body
+		.since
+		.as_ref()
+		.and_then(|string| string.parse().ok());
+
+	let full_state = body.body.full_state;
+
+	// FilterDefinition is very large (0x1000 bytes), let's put it on the heap
+	let filter = Box::new(match body.body.filter.as_ref() {
+		// use the default filter if none was specified
+		| None => FilterDefinition::default(),
+		// use inline filters directly
+		| Some(Filter::FilterDefinition(filter)) => filter.clone(),
+		// look up filter IDs from the database
+		| Some(Filter::FilterId(filter_id)) => services
+			.users
+			.get_filter(syncing_user, filter_id)
+			.await
+			.unwrap_or_default(),
+	});
+
+	let context = SyncContext {
+		syncing_user,
+		syncing_device,
+		last_sync_end_count,
+		current_count,
+		full_state,
+		filter: &filter,
+	};
+
+	let joined_rooms = services
+		.rooms
+		.state_cache
+		.rooms_joined(syncing_user)
+		.map(ToOwned::to_owned)
+		.broad_filter_map(|room_id| async {
+			let joined_room = load_joined_room(services, context, room_id.clone()).await;
+
+			match joined_room {
+				| Ok((room, updates)) => Some((room_id, room, updates)),
+				| Err(err) => {
+					warn!(?err, ?room_id, "error loading joined room {}", room_id);
+					None
+				},
+			}
+		})
+		.ready_fold(
+			(BTreeMap::new(), DeviceListUpdates::new()),
+			|(mut joined_rooms, mut all_updates), (room_id, joined_room, updates)| {
+				all_updates.merge(updates);
+
+				if !joined_room.is_empty() {
+					joined_rooms.insert(room_id, joined_room);
+				}
+
+				(joined_rooms, all_updates)
+			},
+		);
+
+	let left_rooms = services
+		.rooms
+		.state_cache
+		.rooms_left(syncing_user)
+		.broad_filter_map(|(room_id, leave_pdu)| {
+			load_left_room(services, context, room_id.clone(), leave_pdu)
+				.map_ok(move |left_room| (room_id, left_room))
+				.ok()
+		})
+		.ready_filter_map(|(room_id, left_room)| left_room.map(|left_room| (room_id, left_room)))
+		.collect();
+
+	let invited_rooms = services
+		.rooms
+		.state_cache
+		.rooms_invited(syncing_user)
+		.wide_filter_map(async |(room_id, invite_state)| {
+			if is_ignored_invite(services, syncing_user, &room_id).await {
+				None
+			} else {
+				Some((room_id, invite_state))
+			}
+		})
+		.fold_default(|mut invited_rooms: BTreeMap<_, _>, (room_id, invite_state)| async move {
+			let invite_count = services
+				.rooms
+				.state_cache
+				.get_invite_count(&room_id, syncing_user)
+				.await
+				.ok();
+
+			// only sync this invite if it was sent after the last /sync call
+			if last_sync_end_count < invite_count {
+				let invited_room = InvitedRoom {
+					invite_state: InviteState { events: invite_state },
+				};
+
+				invited_rooms.insert(room_id, invited_room);
+			}
+			invited_rooms
+		});
+
+	let knocked_rooms = services
+		.rooms
+		.state_cache
+		.rooms_knocked(syncing_user)
+		.fold_default(|mut knocked_rooms: BTreeMap<_, _>, (room_id, knock_state)| async move {
+			let knock_count = services
+				.rooms
+				.state_cache
+				.get_knock_count(&room_id, syncing_user)
+				.await
+				.ok();
+
+			// only sync this knock if it was sent after the last /sync call
+			if last_sync_end_count < knock_count {
+				let knocked_room = KnockedRoom {
+					knock_state: KnockState { events: knock_state },
+				};
+
+				knocked_rooms.insert(room_id, knocked_room);
+			}
+			knocked_rooms
+		});
+
+	let presence_updates: OptionFuture<_> = services
+		.config
+		.allow_local_presence
+		.then(|| process_presence_updates(services, last_sync_end_count, syncing_user))
+		.into();
+
+	let account_data = services
+		.account_data
+		.changes_since(None, syncing_user, last_sync_end_count, Some(current_count))
+		.ready_filter_map(|e| extract_variant!(e, AnyRawAccountDataEvent::Global))
+		.collect();
+
+	// Look for device list updates of this account
+	let keys_changed = services
+		.users
+		.keys_changed(syncing_user, last_sync_end_count, Some(current_count))
+		.map(ToOwned::to_owned)
+		.collect::<HashSet<_>>();
+
+	let to_device_events = services
+		.users
+		.get_to_device_events(
+			syncing_user,
+			syncing_device,
+			last_sync_end_count,
+			Some(current_count),
+		)
+		.collect::<Vec<_>>();
+
+	let device_one_time_keys_count = services
+		.users
+		.count_one_time_keys(syncing_user, syncing_device);
+
+	// Remove all to-device events the device received *last time*
+	let remove_to_device_events =
+		services
+			.users
+			.remove_to_device_events(syncing_user, syncing_device, last_sync_end_count);
+
+	let rooms = join4(joined_rooms, left_rooms, invited_rooms, knocked_rooms);
+	let ephemeral = join3(remove_to_device_events, to_device_events, presence_updates);
+	let top = join5(account_data, ephemeral, device_one_time_keys_count, keys_changed, rooms)
+		.boxed()
+		.await;
+
+	let (account_data, ephemeral, device_one_time_keys_count, keys_changed, rooms) = top;
+	let ((), to_device_events, presence_updates) = ephemeral;
+	let (joined_rooms, left_rooms, invited_rooms, knocked_rooms) = rooms;
+	let (joined_rooms, mut device_list_updates) = joined_rooms;
+	device_list_updates.changed.extend(keys_changed);
+
+	let response = sync_events::v3::Response {
+		account_data: GlobalAccountData { events: account_data },
+		device_lists: device_list_updates.into(),
+		device_one_time_keys_count,
+		// Fallback keys are not yet supported
+		device_unused_fallback_key_types: None,
+		next_batch: current_count.to_string(),
+		presence: Presence {
+			events: presence_updates
+				.into_iter()
+				.flat_map(IntoIterator::into_iter)
+				.map(|(sender, content)| PresenceEvent { content, sender })
+				.map(|ref event| Raw::new(event))
+				.filter_map(Result::ok)
+				.collect(),
+		},
+		rooms: Rooms {
+			leave: left_rooms,
+			join: joined_rooms,
+			invite: invited_rooms,
+			knock: knocked_rooms,
+		},
+		to_device: ToDevice { events: to_device_events },
+	};
+
+	Ok(response)
+}
+
+#[tracing::instrument(name = "presence", level = "debug", skip_all)]
+async fn process_presence_updates(
+	services: &Services,
+	last_sync_end_count: Option<u64>,
+	syncing_user: &UserId,
+) -> PresenceUpdates {
+	services
+		.presence
+		.presence_since(last_sync_end_count.unwrap_or(0)) // send all presences on initial sync
+		.filter(|(user_id, ..)| {
+			services
+				.rooms
+				.state_cache
+				.user_sees_user(syncing_user, user_id)
+		})
+		.filter_map(|(user_id, _, presence_bytes)| {
+			services
+				.presence
+				.from_json_bytes_to_event(presence_bytes, user_id)
+				.map_ok(move |event| (user_id, event))
+				.ok()
+		})
+		.map(|(user_id, event)| (user_id.to_owned(), event.content))
+		.collect()
+		.await
+}
+
+/// Using the provided sync context and an iterator of user IDs in the
+/// `timeline`, return a HashSet of user IDs whose membership events should be
+/// sent to the client if lazy-loading is enabled.
+#[allow(clippy::let_and_return)]
+async fn prepare_lazily_loaded_members(
+	services: &Services,
+	sync_context: SyncContext<'_>,
+	room_id: &RoomId,
+	timeline_members: impl Iterator<Item = OwnedUserId>,
+) -> Option<MemberSet> {
+	let lazy_loading_context = &sync_context.lazy_loading_context(room_id);
+
+	// reset lazy loading state on initial sync.
+	// do this even if lazy loading is disabled so future lazy loads
+	// will have the correct members.
+	if sync_context.last_sync_end_count.is_none() {
+		services
+			.rooms
+			.lazy_loading
+			.reset(lazy_loading_context)
+			.await;
+	}
+
+	// filter the input members through `retain_lazy_members`, which
+	// contains the actual lazy loading logic.
+	let lazily_loaded_members =
+		OptionFuture::from(sync_context.lazy_loading_enabled().then(|| {
+			services
+				.rooms
+				.lazy_loading
+				.retain_lazy_members(timeline_members.collect(), lazy_loading_context)
+		}))
+		.await;
+
+	lazily_loaded_members
+}

src/api/client/sync/v3/state.rs

@@ -0,0 +1,280 @@
+use std::{collections::BTreeSet, ops::ControlFlow};
+
+use conduwuit::{
+	Result, at, is_equal_to,
+	matrix::{
+		Event,
+		pdu::{PduCount, PduEvent},
+	},
+	utils::{
+		BoolExt, IterStream, ReadyExt, TryFutureExtExt,
+		stream::{BroadbandExt, TryIgnore},
+	},
+};
+use conduwuit_service::{
+	Services,
+	rooms::{lazy_loading::MemberSet, short::ShortStateHash},
+};
+use futures::{FutureExt, StreamExt};
+use itertools::Itertools;
+use ruma::{OwnedEventId, RoomId, UserId, events::StateEventType};
+use service::rooms::short::ShortEventId;
+use tracing::trace;
+
+use crate::client::TimelinePdus;
+
+/// Calculate the state events to include in an initial sync response.
+///
+/// If lazy-loading is enabled (`lazily_loaded_members` is Some), the returned
+/// Vec will include the membership events of exclusively the members in
+/// `lazily_loaded_members`.
+#[tracing::instrument(
+	name = "initial",
+	level = "trace",
+	skip_all,
+	fields(current_shortstatehash)
+)]
+#[allow(clippy::too_many_arguments)]
+pub(super) async fn build_state_initial(
+	services: &Services,
+	sender_user: &UserId,
+	timeline_start_shortstatehash: ShortStateHash,
+	lazily_loaded_members: Option<&MemberSet>,
+) -> Result<Vec<PduEvent>> {
+	// load the keys and event IDs of the state events at the start of the timeline
+	let (shortstatekeys, event_ids): (Vec<_>, Vec<_>) = services
+		.rooms
+		.state_accessor
+		.state_full_ids(timeline_start_shortstatehash)
+		.unzip()
+		.await;
+
+	trace!("performing initial sync of {} state events", event_ids.len());
+
+	services
+		.rooms
+		.short
+		// look up the full state keys
+		.multi_get_statekey_from_short(shortstatekeys.into_iter().stream())
+		.zip(event_ids.into_iter().stream())
+		.ready_filter_map(|item| Some((item.0.ok()?, item.1)))
+		.ready_filter_map(|((event_type, state_key), event_id)| {
+			if let Some(lazily_loaded_members) = lazily_loaded_members {
+				/*
+				if lazy loading is enabled, filter out membership events which aren't for a user
+				included in `lazily_loaded_members` or for the user requesting the sync.
+				*/
+				let event_is_redundant = event_type == StateEventType::RoomMember
+					&& state_key.as_str().try_into().is_ok_and(|user_id: &UserId| {
+						sender_user != user_id && !lazily_loaded_members.contains(user_id)
+					});
+
+				event_is_redundant.or_some(event_id)
+			} else {
+				Some(event_id)
+			}
+		})
+		.broad_filter_map(|event_id: OwnedEventId| async move {
+			services.rooms.timeline.get_pdu(&event_id).await.ok()
+		})
+		.collect()
+		.map(Ok)
+		.await
+}
+
+/// Calculate the state events to include in an incremental sync response.
+///
+/// If lazy-loading is enabled (`lazily_loaded_members` is Some), the returned
+/// Vec will include the membership events of all the members in
+/// `lazily_loaded_members`.
+#[tracing::instrument(name = "incremental", level = "trace", skip_all)]
+#[allow(clippy::too_many_arguments)]
+pub(super) async fn build_state_incremental<'a>(
+	services: &Services,
+	sender_user: &'a UserId,
+	room_id: &RoomId,
+	last_sync_end_count: PduCount,
+	last_sync_end_shortstatehash: ShortStateHash,
+	timeline_start_shortstatehash: ShortStateHash,
+	timeline_end_shortstatehash: ShortStateHash,
+	timeline: &TimelinePdus,
+	lazily_loaded_members: Option<&'a MemberSet>,
+) -> Result<Vec<PduEvent>> {
+	/*
+	NB: a limited sync is one where `timeline.limited == true`. Synapse calls this a "gappy" sync internally.
+
+	The algorithm implemented in this function is, currently, quite different from the algorithm vaguely described
+	by the Matrix specification. This is because the specification's description of the `state` property does not accurately
+	reflect how Synapse behaves, and therefore how client SDKs behave. Notable differences include:
+	1. We do not compute the delta using the naive approach of "every state event from the end of the last sync
+	   up to the start of this sync's timeline". see below for details.
+	2. If lazy-loading is enabled, we include lazily-loaded membership events. The specific users to include are determined
+	   elsewhere and supplied to this function in the `lazily_loaded_members` parameter.
+	*/
+
+	/*
+	the `state` property of an incremental sync which isn't limited are _usually_ empty.
+	(note: the specification says that the `state` property is _always_ empty for limited syncs, which is incorrect.)
+	however, if an event in the timeline (`timeline.pdus`) merges a split in the room's DAG (i.e. has multiple `prev_events`),
+	the state at the _end_ of the timeline may include state events which were merged in and don't exist in the state
+	at the _start_ of the timeline. because this is uncommon, we check here to see if any events in the timeline
+	merged a split in the DAG.
+
+	see: https://github.com/element-hq/synapse/issues/16941
+	*/
+
+	let timeline_is_linear = timeline.pdus.is_empty() || {
+		let last_pdu_of_last_sync = services
+			.rooms
+			.timeline
+			.pdus_rev(Some(sender_user), room_id, Some(last_sync_end_count.saturating_add(1)))
+			.boxed()
+			.next()
+			.await
+			.transpose()
+			.expect("last sync should have had some PDUs")
+			.map(at!(1));
+
+		// make sure the prev_events of each pdu in the timeline refer only to the
+		// previous pdu
+		timeline
+			.pdus
+			.iter()
+			.try_fold(last_pdu_of_last_sync.map(|pdu| pdu.event_id), |prev_event_id, (_, pdu)| {
+				if let Ok(pdu_prev_event_id) = pdu.prev_events.iter().exactly_one() {
+					if prev_event_id
+						.as_ref()
+						.is_none_or(is_equal_to!(pdu_prev_event_id))
+					{
+						return ControlFlow::Continue(Some(pdu_prev_event_id.to_owned()));
+					}
+				}
+
+				trace!(
+					"pdu {:?} has split prev_events (expected {:?}): {:?}",
+					pdu.event_id, prev_event_id, pdu.prev_events
+				);
+				ControlFlow::Break(())
+			})
+			.is_continue()
+	};
+
+	if timeline_is_linear && !timeline.limited {
+		// if there are no splits in the DAG and the timeline isn't limited, then
+		// `state` will always be empty unless lazy loading is enabled.
+
+		if let Some(lazily_loaded_members) = lazily_loaded_members {
+			if !timeline.pdus.is_empty() {
+				// lazy loading is enabled, so we return the membership events which were
+				// requested by the caller.
+				let lazy_membership_events: Vec<_> = lazily_loaded_members
+					.iter()
+					.stream()
+					.broad_filter_map(|user_id| async move {
+						if user_id == sender_user {
+							return None;
+						}
+
+						services
+							.rooms
+							.state_accessor
+							.state_get(
+								timeline_start_shortstatehash,
+								&StateEventType::RoomMember,
+								user_id.as_str(),
+							)
+							.ok()
+							.await
+					})
+					.collect()
+					.await;
+
+				if !lazy_membership_events.is_empty() {
+					trace!(
+						"syncing lazy membership events for members: {:?}",
+						lazy_membership_events
+							.iter()
+							.map(|pdu| pdu.state_key().unwrap())
+							.collect::<Vec<_>>()
+					);
+				}
+				return Ok(lazy_membership_events);
+			}
+		}
+
+		// lazy loading is disabled, `state` is empty.
+		return Ok(vec![]);
+	}
+
+	/*
+	at this point, either the timeline is `limited` or the DAG has a split in it. this necessitates
+	computing the incremental state (which may be empty).
+
+	NOTE: this code path does not use the `lazy_membership_events` parameter. any changes to membership will be included
+	in the incremental state. therefore, the incremental state may include "redundant" membership events,
+	which we do not filter out because A. the spec forbids lazy-load filtering if the timeline is `limited`,
+	and B. DAG splits which require sending extra membership state events are (probably) uncommon enough that
+	the performance penalty is acceptable.
+	*/
+
+	trace!(?timeline_is_linear, ?timeline.limited, "computing state for incremental sync");
+
+	// fetch the shorteventids of state events in the timeline
+	let state_events_in_timeline: BTreeSet<ShortEventId> = services
+		.rooms
+		.short
+		.multi_get_or_create_shorteventid(timeline.pdus.iter().filter_map(|(_, pdu)| {
+			if pdu.state_key().is_some() {
+				Some(pdu.event_id.as_ref())
+			} else {
+				None
+			}
+		}))
+		.collect()
+		.await;
+
+	trace!("{} state events in timeline", state_events_in_timeline.len());
+
+	/*
+	fetch the state events which were added since the last sync.
+
+	specifically we fetch the difference between the state at the last sync and the state at the _end_
+	of the timeline, and then we filter out state events in the timeline itself using the shorteventids we fetched.
+	this is necessary to account for splits in the DAG, as explained above.
+	*/
+	let state_diff = services
+		.rooms
+		.short
+		.multi_get_eventid_from_short::<'_, OwnedEventId, _>(
+			services
+				.rooms
+				.state_accessor
+				.state_added((last_sync_end_shortstatehash, timeline_end_shortstatehash))
+				.await?
+				.stream()
+				.ready_filter_map(|(_, shorteventid)| {
+					if state_events_in_timeline.contains(&shorteventid) {
+						None
+					} else {
+						Some(shorteventid)
+					}
+				}),
+		)
+		.ignore_err();
+
+	// finally, fetch the PDU contents and collect them into a vec
+	let state_diff_pdus = state_diff
+		.broad_filter_map(|event_id| async move {
+			services
+				.rooms
+				.timeline
+				.get_non_outlier_pdu(&event_id)
+				.await
+				.ok()
+		})
+		.collect::<Vec<_>>()
+		.await;
+
+	trace!(?state_diff_pdus, "collected state PDUs for incremental sync");
+	Ok(state_diff_pdus)
+}

src/api/client/sync/v4.rs

@@ -1,848 +0,0 @@
-use std::{
-	cmp::{self, Ordering},
-	collections::{BTreeMap, BTreeSet, HashMap, HashSet},
-	time::Duration,
-};
-
-use axum::extract::State;
-use conduwuit::{
-	Err, Error, Event, PduCount, Result, at, debug, error, extract_variant,
-	matrix::TypeStateKey,
-	utils::{
-		BoolExt, IterStream, ReadyExt, TryFutureExtExt,
-		math::{ruma_from_usize, usize_from_ruma, usize_from_u64_truncated},
-		stream::WidebandExt,
-	},
-	warn,
-};
-use conduwuit_service::{
-	Services,
-	rooms::read_receipt::pack_receipts,
-	sync::{into_db_key, into_snake_key},
-};
-use futures::{FutureExt, StreamExt, TryFutureExt};
-use ruma::{
-	MilliSecondsSinceUnixEpoch, OwnedEventId, OwnedRoomId, RoomId, UInt, UserId,
-	api::client::sync::sync_events::{
-		self, DeviceLists, UnreadNotificationsCount,
-		v4::{SlidingOp, SlidingSyncRoomHero},
-	},
-	directory::RoomTypeFilter,
-	events::{
-		AnyRawAccountDataEvent, AnySyncEphemeralRoomEvent, StateEventType,
-		TimelineEventType::*,
-		room::member::{MembershipState, RoomMemberEventContent},
-	},
-	serde::Raw,
-	uint,
-};
-
-use super::{load_timeline, share_encrypted_room};
-use crate::{
-	Ruma,
-	client::{DEFAULT_BUMP_TYPES, ignored_filter, is_ignored_invite},
-};
-
-type TodoRooms = BTreeMap<OwnedRoomId, (BTreeSet<TypeStateKey>, usize, u64)>;
-const SINGLE_CONNECTION_SYNC: &str = "single_connection_sync";
-
-#[allow(clippy::cognitive_complexity)]
-/// POST `/_matrix/client/unstable/org.matrix.msc3575/sync`
-///
-/// Sliding Sync endpoint (future endpoint: `/_matrix/client/v4/sync`)
-pub(crate) async fn sync_events_v4_route(
-	State(services): State<crate::State>,
-	body: Ruma<sync_events::v4::Request>,
-) -> Result<sync_events::v4::Response> {
-	debug_assert!(DEFAULT_BUMP_TYPES.is_sorted(), "DEFAULT_BUMP_TYPES is not sorted");
-	let sender_user = body.sender_user.as_ref().expect("user is authenticated");
-	let sender_device = body.sender_device.as_ref().expect("user is authenticated");
-	let mut body = body.body;
-
-	// Setup watchers, so if there's no response, we can wait for them
-	let watcher = services.sync.watch(sender_user, sender_device);
-
-	let next_batch = services.globals.next_count()?;
-
-	let conn_id = body
-		.conn_id
-		.clone()
-		.unwrap_or_else(|| SINGLE_CONNECTION_SYNC.to_owned());
-
-	let globalsince = body
-		.pos
-		.as_ref()
-		.and_then(|string| string.parse().ok())
-		.unwrap_or(0);
-
-	let db_key = into_db_key(sender_user, sender_device, conn_id.clone());
-	if globalsince != 0 && !services.sync.remembered(&db_key) {
-		debug!("Restarting sync stream because it was gone from the database");
-		return Err!(Request(UnknownPos("Connection data lost since last time")));
-	}
-
-	if globalsince == 0 {
-		services.sync.forget_sync_request_connection(&db_key);
-	}
-
-	// Get sticky parameters from cache
-	let snake_key = into_snake_key(sender_user, sender_device, conn_id.clone());
-	let known_rooms = services
-		.sync
-		.update_sync_request_with_cache(&snake_key, &mut body);
-
-	let all_joined_rooms: Vec<_> = services
-		.rooms
-		.state_cache
-		.rooms_joined(sender_user)
-		.map(ToOwned::to_owned)
-		.collect()
-		.await;
-
-	let all_invited_rooms: Vec<_> = services
-		.rooms
-		.state_cache
-		.rooms_invited(sender_user)
-		.wide_filter_map(async |(room_id, invite_state)| {
-			if is_ignored_invite(&services, sender_user, &room_id).await {
-				None
-			} else {
-				Some((room_id, invite_state))
-			}
-		})
-		.map(|r| r.0)
-		.collect()
-		.await;
-
-	let all_knocked_rooms: Vec<_> = services
-		.rooms
-		.state_cache
-		.rooms_knocked(sender_user)
-		.map(|r| r.0)
-		.collect()
-		.await;
-
-	let all_invited_rooms: Vec<&RoomId> = all_invited_rooms.iter().map(AsRef::as_ref).collect();
-	let all_knocked_rooms: Vec<&RoomId> = all_knocked_rooms.iter().map(AsRef::as_ref).collect();
-
-	let all_rooms: Vec<&RoomId> = all_joined_rooms
-		.iter()
-		.map(AsRef::as_ref)
-		.chain(all_invited_rooms.iter().map(AsRef::as_ref))
-		.chain(all_knocked_rooms.iter().map(AsRef::as_ref))
-		.collect();
-
-	let all_joined_rooms = all_joined_rooms.iter().map(AsRef::as_ref).collect();
-	let all_invited_rooms = all_invited_rooms.iter().map(AsRef::as_ref).collect();
-
-	if body.extensions.to_device.enabled.unwrap_or(false) {
-		services
-			.users
-			.remove_to_device_events(sender_user, sender_device, globalsince)
-			.await;
-	}
-
-	let mut left_encrypted_users = HashSet::new(); // Users that have left any encrypted rooms the sender was in
-	let mut device_list_changes = HashSet::new();
-	let mut device_list_left = HashSet::new();
-
-	let mut receipts = sync_events::v4::Receipts { rooms: BTreeMap::new() };
-
-	let mut account_data = sync_events::v4::AccountData {
-		global: Vec::new(),
-		rooms: BTreeMap::new(),
-	};
-	if body.extensions.account_data.enabled.unwrap_or(false) {
-		account_data.global = services
-			.account_data
-			.changes_since(None, sender_user, globalsince, Some(next_batch))
-			.ready_filter_map(|e| extract_variant!(e, AnyRawAccountDataEvent::Global))
-			.collect()
-			.await;
-
-		if let Some(rooms) = body.extensions.account_data.rooms {
-			for room in rooms {
-				account_data.rooms.insert(
-					room.clone(),
-					services
-						.account_data
-						.changes_since(Some(&room), sender_user, globalsince, Some(next_batch))
-						.ready_filter_map(|e| extract_variant!(e, AnyRawAccountDataEvent::Room))
-						.collect()
-						.await,
-				);
-			}
-		}
-	}
-
-	if body.extensions.e2ee.enabled.unwrap_or(false) {
-		// Look for device list updates of this account
-		device_list_changes.extend(
-			services
-				.users
-				.keys_changed(sender_user, globalsince, None)
-				.map(ToOwned::to_owned)
-				.collect::<Vec<_>>()
-				.await,
-		);
-
-		for room_id in &all_joined_rooms {
-			let room_id: &&RoomId = room_id;
-			let Ok(current_shortstatehash) =
-				services.rooms.state.get_room_shortstatehash(room_id).await
-			else {
-				error!("Room {room_id} has no state");
-				continue;
-			};
-
-			let since_shortstatehash = services
-				.rooms
-				.user
-				.get_token_shortstatehash(room_id, globalsince)
-				.await
-				.ok();
-
-			let encrypted_room = services
-				.rooms
-				.state_accessor
-				.state_get(current_shortstatehash, &StateEventType::RoomEncryption, "")
-				.await
-				.is_ok();
-
-			if let Some(since_shortstatehash) = since_shortstatehash {
-				// Skip if there are only timeline changes
-				if since_shortstatehash == current_shortstatehash {
-					continue;
-				}
-
-				let since_encryption = services
-					.rooms
-					.state_accessor
-					.state_get(since_shortstatehash, &StateEventType::RoomEncryption, "")
-					.await;
-
-				let since_sender_member: Option<RoomMemberEventContent> = services
-					.rooms
-					.state_accessor
-					.state_get_content(
-						since_shortstatehash,
-						&StateEventType::RoomMember,
-						sender_user.as_str(),
-					)
-					.ok()
-					.await;
-
-				let joined_since_last_sync = since_sender_member
-					.as_ref()
-					.is_none_or(|member| member.membership != MembershipState::Join);
-
-				let new_encrypted_room = encrypted_room && since_encryption.is_err();
-
-				if encrypted_room {
-					let current_state_ids: HashMap<_, OwnedEventId> = services
-						.rooms
-						.state_accessor
-						.state_full_ids(current_shortstatehash)
-						.collect()
-						.await;
-
-					let since_state_ids: HashMap<_, _> = services
-						.rooms
-						.state_accessor
-						.state_full_ids(since_shortstatehash)
-						.collect()
-						.await;
-
-					for (key, id) in current_state_ids {
-						if since_state_ids.get(&key) != Some(&id) {
-							let Ok(pdu) = services.rooms.timeline.get_pdu(&id).await else {
-								error!("Pdu in state not found: {id}");
-								continue;
-							};
-							if pdu.kind == RoomMember {
-								if let Some(Ok(user_id)) =
-									pdu.state_key.as_deref().map(UserId::parse)
-								{
-									if user_id == sender_user {
-										continue;
-									}
-
-									let content: RoomMemberEventContent = pdu.get_content()?;
-									match content.membership {
-										| MembershipState::Join => {
-											// A new user joined an encrypted room
-											if !share_encrypted_room(
-												&services,
-												sender_user,
-												user_id,
-												Some(room_id),
-											)
-											.await
-											{
-												device_list_changes.insert(user_id.to_owned());
-											}
-										},
-										| MembershipState::Leave => {
-											// Write down users that have left encrypted rooms we
-											// are in
-											left_encrypted_users.insert(user_id.to_owned());
-										},
-										| _ => {},
-									}
-								}
-							}
-						}
-					}
-					if joined_since_last_sync || new_encrypted_room {
-						// If the user is in a new encrypted room, give them all joined users
-						device_list_changes.extend(
-							services
-								.rooms
-								.state_cache
-								.room_members(room_id)
-								// Don't send key updates from the sender to the sender
-								.ready_filter(|&user_id| sender_user != user_id)
-								// Only send keys if the sender doesn't share an encrypted room with the target
-								// already
-								.filter_map(|user_id| {
-									share_encrypted_room(&services, sender_user, user_id, Some(room_id))
-										.map(|res| res.or_some(user_id.to_owned()))
-								})
-								.collect::<Vec<_>>()
-								.await,
-						);
-					}
-				}
-			}
-			// Look for device list updates in this room
-			device_list_changes.extend(
-				services
-					.users
-					.room_keys_changed(room_id, globalsince, None)
-					.map(|(user_id, _)| user_id)
-					.map(ToOwned::to_owned)
-					.collect::<Vec<_>>()
-					.await,
-			);
-		}
-
-		for user_id in left_encrypted_users {
-			let dont_share_encrypted_room =
-				!share_encrypted_room(&services, sender_user, &user_id, None).await;
-
-			// If the user doesn't share an encrypted room with the target anymore, we need
-			// to tell them
-			if dont_share_encrypted_room {
-				device_list_left.insert(user_id);
-			}
-		}
-	}
-
-	let mut lists = BTreeMap::new();
-	let mut todo_rooms: TodoRooms = BTreeMap::new(); // and required state
-
-	for (list_id, list) in &body.lists {
-		let active_rooms = match list.filters.clone().and_then(|f| f.is_invite) {
-			| Some(true) => &all_invited_rooms,
-			| Some(false) => &all_joined_rooms,
-			| None => &all_rooms,
-		};
-
-		let active_rooms = match list.filters.clone().map(|f| f.not_room_types) {
-			| Some(filter) if filter.is_empty() => active_rooms.clone(),
-			| Some(value) => filter_rooms(&services, active_rooms, &value, true).await,
-			| None => active_rooms.clone(),
-		};
-
-		let active_rooms = match list.filters.clone().map(|f| f.room_types) {
-			| Some(filter) if filter.is_empty() => active_rooms.clone(),
-			| Some(value) => filter_rooms(&services, &active_rooms, &value, false).await,
-			| None => active_rooms,
-		};
-
-		let mut new_known_rooms: BTreeSet<OwnedRoomId> = BTreeSet::new();
-
-		let ranges = list.ranges.clone();
-		lists.insert(list_id.clone(), sync_events::v4::SyncList {
-			ops: ranges
-				.into_iter()
-				.map(|mut r| {
-					r.0 = r.0.clamp(
-						uint!(0),
-						UInt::try_from(active_rooms.len().saturating_sub(1)).unwrap_or(UInt::MAX),
-					);
-					r.1 = r.1.clamp(
-						r.0,
-						UInt::try_from(active_rooms.len().saturating_sub(1)).unwrap_or(UInt::MAX),
-					);
-
-					let room_ids = if !active_rooms.is_empty() {
-						active_rooms[usize_from_ruma(r.0)..=usize_from_ruma(r.1)].to_vec()
-					} else {
-						Vec::new()
-					};
-
-					new_known_rooms.extend(room_ids.clone().into_iter().map(ToOwned::to_owned));
-					for room_id in &room_ids {
-						let todo_room = todo_rooms.entry((*room_id).to_owned()).or_insert((
-							BTreeSet::new(),
-							0_usize,
-							u64::MAX,
-						));
-
-						let limit: usize = list
-							.room_details
-							.timeline_limit
-							.map(u64::from)
-							.map_or(10, usize_from_u64_truncated)
-							.min(100);
-
-						todo_room.0.extend(
-							list.room_details
-								.required_state
-								.iter()
-								.map(|(ty, sk)| (ty.clone(), sk.as_str().into())),
-						);
-
-						todo_room.1 = todo_room.1.max(limit);
-						// 0 means unknown because it got out of date
-						todo_room.2 = todo_room.2.min(
-							known_rooms
-								.get(list_id.as_str())
-								.and_then(|k| k.get(*room_id))
-								.copied()
-								.unwrap_or(0),
-						);
-					}
-					sync_events::v4::SyncOp {
-						op: SlidingOp::Sync,
-						range: Some(r),
-						index: None,
-						room_ids: room_ids.into_iter().map(ToOwned::to_owned).collect(),
-						room_id: None,
-					}
-				})
-				.collect(),
-			count: ruma_from_usize(active_rooms.len()),
-		});
-
-		if let Some(conn_id) = &body.conn_id {
-			let db_key = into_db_key(sender_user, sender_device, conn_id);
-			services.sync.update_sync_known_rooms(
-				&db_key,
-				list_id.clone(),
-				new_known_rooms,
-				globalsince,
-			);
-		}
-	}
-
-	let mut known_subscription_rooms = BTreeSet::new();
-	for (room_id, room) in &body.room_subscriptions {
-		if !services.rooms.metadata.exists(room_id).await
-			|| services.rooms.metadata.is_disabled(room_id).await
-			|| services.rooms.metadata.is_banned(room_id).await
-		{
-			continue;
-		}
-		let todo_room =
-			todo_rooms
-				.entry(room_id.clone())
-				.or_insert((BTreeSet::new(), 0_usize, u64::MAX));
-
-		let limit: usize = room
-			.timeline_limit
-			.map(u64::from)
-			.map_or(10, usize_from_u64_truncated)
-			.min(100);
-
-		todo_room.0.extend(
-			room.required_state
-				.iter()
-				.map(|(ty, sk)| (ty.clone(), sk.as_str().into())),
-		);
-		todo_room.1 = todo_room.1.max(limit);
-		// 0 means unknown because it got out of date
-		todo_room.2 = todo_room.2.min(
-			known_rooms
-				.get("subscriptions")
-				.and_then(|k| k.get(room_id))
-				.copied()
-				.unwrap_or(0),
-		);
-		known_subscription_rooms.insert(room_id.clone());
-	}
-
-	for r in body.unsubscribe_rooms {
-		known_subscription_rooms.remove(&r);
-		body.room_subscriptions.remove(&r);
-	}
-
-	if let Some(conn_id) = &body.conn_id {
-		let db_key = into_db_key(sender_user, sender_device, conn_id);
-		services.sync.update_sync_known_rooms(
-			&db_key,
-			"subscriptions".to_owned(),
-			known_subscription_rooms,
-			globalsince,
-		);
-	}
-
-	if let Some(conn_id) = body.conn_id.clone() {
-		let db_key = into_db_key(sender_user, sender_device, conn_id);
-		services
-			.sync
-			.update_sync_subscriptions(&db_key, body.room_subscriptions);
-	}
-
-	let mut rooms = BTreeMap::new();
-	for (room_id, (required_state_request, timeline_limit, roomsince)) in &todo_rooms {
-		let roomsincecount = PduCount::Normal(*roomsince);
-
-		let mut timestamp: Option<_> = None;
-		let mut invite_state = None;
-		let (timeline_pdus, limited);
-		let new_room_id: &RoomId = (*room_id).as_ref();
-		if all_invited_rooms.contains(&new_room_id) {
-			// TODO: figure out a timestamp we can use for remote invites
-			invite_state = services
-				.rooms
-				.state_cache
-				.invite_state(sender_user, room_id)
-				.await
-				.ok();
-
-			(timeline_pdus, limited) = (Vec::new(), true);
-		} else {
-			(timeline_pdus, limited) = match load_timeline(
-				&services,
-				sender_user,
-				room_id,
-				roomsincecount,
-				None,
-				*timeline_limit,
-			)
-			.await
-			{
-				| Ok(value) => value,
-				| Err(err) => {
-					warn!("Encountered missing timeline in {}, error {}", room_id, err);
-					continue;
-				},
-			};
-		}
-
-		account_data.rooms.insert(
-			room_id.to_owned(),
-			services
-				.account_data
-				.changes_since(Some(room_id), sender_user, *roomsince, Some(next_batch))
-				.ready_filter_map(|e| extract_variant!(e, AnyRawAccountDataEvent::Room))
-				.collect()
-				.await,
-		);
-
-		let last_privateread_update = services
-			.rooms
-			.read_receipt
-			.last_privateread_update(sender_user, room_id)
-			.await > *roomsince;
-
-		let private_read_event = if last_privateread_update {
-			services
-				.rooms
-				.read_receipt
-				.private_read_get(room_id, sender_user)
-				.await
-				.ok()
-		} else {
-			None
-		};
-
-		let mut vector: Vec<Raw<AnySyncEphemeralRoomEvent>> = services
-			.rooms
-			.read_receipt
-			.readreceipts_since(room_id, *roomsince)
-			.filter_map(|(read_user, _ts, v)| async move {
-				services
-					.users
-					.user_is_ignored(read_user, sender_user)
-					.await
-					.or_some(v)
-			})
-			.collect()
-			.await;
-
-		if let Some(private_read_event) = private_read_event {
-			vector.push(private_read_event);
-		}
-
-		let receipt_size = vector.len();
-		receipts
-			.rooms
-			.insert(room_id.clone(), pack_receipts(Box::new(vector.into_iter())));
-
-		if roomsince != &0
-			&& timeline_pdus.is_empty()
-			&& account_data.rooms.get(room_id).is_some_and(Vec::is_empty)
-			&& receipt_size == 0
-		{
-			continue;
-		}
-
-		let prev_batch = timeline_pdus
-			.first()
-			.map_or(Ok::<_, Error>(None), |(pdu_count, _)| {
-				Ok(Some(match pdu_count {
-					| PduCount::Backfilled(_) => {
-						error!("timeline in backfill state?!");
-						"0".to_owned()
-					},
-					| PduCount::Normal(c) => c.to_string(),
-				}))
-			})?
-			.or_else(|| {
-				if roomsince != &0 {
-					Some(roomsince.to_string())
-				} else {
-					None
-				}
-			});
-
-		let room_events: Vec<_> = timeline_pdus
-			.iter()
-			.stream()
-			.filter_map(|item| ignored_filter(&services, item.clone(), sender_user))
-			.map(at!(1))
-			.map(Event::into_format)
-			.collect()
-			.await;
-
-		for (_, pdu) in timeline_pdus {
-			let ts = MilliSecondsSinceUnixEpoch(pdu.origin_server_ts);
-			if DEFAULT_BUMP_TYPES.binary_search(&pdu.kind).is_ok()
-				&& timestamp.is_none_or(|time| time <= ts)
-			{
-				timestamp = Some(ts);
-			}
-		}
-
-		let required_state = required_state_request
-			.iter()
-			.stream()
-			.filter_map(|state| async move {
-				services
-					.rooms
-					.state_accessor
-					.room_state_get(room_id, &state.0, &state.1)
-					.await
-					.map(Event::into_format)
-					.ok()
-			})
-			.collect()
-			.await;
-
-		// Heroes
-		let heroes: Vec<_> = services
-			.rooms
-			.state_cache
-			.room_members(room_id)
-			.ready_filter(|&member| member != sender_user)
-			.filter_map(|user_id| {
-				services
-					.rooms
-					.state_accessor
-					.get_member(room_id, user_id)
-					.map_ok(|memberevent| SlidingSyncRoomHero {
-						user_id: user_id.into(),
-						name: memberevent.displayname,
-						avatar: memberevent.avatar_url,
-					})
-					.ok()
-			})
-			.take(5)
-			.collect()
-			.await;
-
-		let name = match heroes.len().cmp(&(1_usize)) {
-			| Ordering::Greater => {
-				let firsts = heroes[1..]
-					.iter()
-					.map(|h| h.name.clone().unwrap_or_else(|| h.user_id.to_string()))
-					.collect::<Vec<_>>()
-					.join(", ");
-
-				let last = heroes[0]
-					.name
-					.clone()
-					.unwrap_or_else(|| heroes[0].user_id.to_string());
-
-				Some(format!("{firsts} and {last}"))
-			},
-			| Ordering::Equal => Some(
-				heroes[0]
-					.name
-					.clone()
-					.unwrap_or_else(|| heroes[0].user_id.to_string()),
-			),
-			| Ordering::Less => None,
-		};
-
-		let heroes_avatar = if heroes.len() == 1 {
-			heroes[0].avatar.clone()
-		} else {
-			None
-		};
-
-		rooms.insert(room_id.clone(), sync_events::v4::SlidingSyncRoom {
-			name: services
-				.rooms
-				.state_accessor
-				.get_name(room_id)
-				.await
-				.ok()
-				.or(name),
-			avatar: match heroes_avatar {
-				| Some(heroes_avatar) => ruma::JsOption::Some(heroes_avatar),
-				| _ => match services.rooms.state_accessor.get_avatar(room_id).await {
-					| ruma::JsOption::Some(avatar) => ruma::JsOption::from_option(avatar.url),
-					| ruma::JsOption::Null => ruma::JsOption::Null,
-					| ruma::JsOption::Undefined => ruma::JsOption::Undefined,
-				},
-			},
-			initial: Some(roomsince == &0),
-			is_dm: None,
-			invite_state,
-			unread_notifications: UnreadNotificationsCount {
-				highlight_count: Some(
-					services
-						.rooms
-						.user
-						.highlight_count(sender_user, room_id)
-						.await
-						.try_into()
-						.expect("notification count can't go that high"),
-				),
-				notification_count: Some(
-					services
-						.rooms
-						.user
-						.notification_count(sender_user, room_id)
-						.await
-						.try_into()
-						.expect("notification count can't go that high"),
-				),
-			},
-			timeline: room_events,
-			required_state,
-			prev_batch,
-			limited,
-			joined_count: Some(
-				services
-					.rooms
-					.state_cache
-					.room_joined_count(room_id)
-					.await
-					.unwrap_or(0)
-					.try_into()
-					.unwrap_or_else(|_| uint!(0)),
-			),
-			invited_count: Some(
-				services
-					.rooms
-					.state_cache
-					.room_invited_count(room_id)
-					.await
-					.unwrap_or(0)
-					.try_into()
-					.unwrap_or_else(|_| uint!(0)),
-			),
-			num_live: None, // Count events in timeline greater than global sync counter
-			timestamp,
-			heroes: Some(heroes),
-		});
-	}
-
-	if rooms.iter().all(|(id, r)| {
-		r.timeline.is_empty() && r.required_state.is_empty() && !receipts.rooms.contains_key(id)
-	}) {
-		// Hang a few seconds so requests are not spammed
-		// Stop hanging if new info arrives
-		let default = Duration::from_secs(30);
-		let duration = cmp::min(body.timeout.unwrap_or(default), default);
-		_ = tokio::time::timeout(duration, watcher).await;
-	}
-
-	Ok(sync_events::v4::Response {
-		initial: globalsince == 0,
-		txn_id: body.txn_id.clone(),
-		pos: next_batch.to_string(),
-		lists,
-		rooms,
-		extensions: sync_events::v4::Extensions {
-			to_device: if body.extensions.to_device.enabled.unwrap_or(false) {
-				Some(sync_events::v4::ToDevice {
-					events: services
-						.users
-						.get_to_device_events(
-							sender_user,
-							sender_device,
-							Some(globalsince),
-							Some(next_batch),
-						)
-						.collect()
-						.await,
-					next_batch: next_batch.to_string(),
-				})
-			} else {
-				None
-			},
-			e2ee: sync_events::v4::E2EE {
-				device_lists: DeviceLists {
-					changed: device_list_changes.into_iter().collect(),
-					left: device_list_left.into_iter().collect(),
-				},
-				device_one_time_keys_count: services
-					.users
-					.count_one_time_keys(sender_user, sender_device)
-					.await,
-				// Fallback keys are not yet supported
-				device_unused_fallback_key_types: None,
-			},
-			account_data,
-			receipts,
-			typing: sync_events::v4::Typing { rooms: BTreeMap::new() },
-		},
-		delta_token: None,
-	})
-}
-
-async fn filter_rooms<'a>(
-	services: &Services,
-	rooms: &[&'a RoomId],
-	filter: &[RoomTypeFilter],
-	negate: bool,
-) -> Vec<&'a RoomId> {
-	rooms
-		.iter()
-		.stream()
-		.filter_map(|r| async move {
-			let room_type = services.rooms.state_accessor.get_room_type(r).await;
-
-			if room_type.as_ref().is_err_and(|e| !e.is_not_found()) {
-				return None;
-			}
-
-			let room_type_filter = RoomTypeFilter::from(room_type.ok());
-
-			let include = if negate {
-				!filter.contains(&room_type_filter)
-			} else {
-				filter.is_empty() || filter.contains(&room_type_filter)
-			};
-
-			include.then_some(r)
-		})
-		.collect()
-		.await
-}

src/api/client/sync/v5.rs

@@ -1,6 +1,6 @@
 use std::{
 	cmp::{self, Ordering},
-	collections::{BTreeMap, BTreeSet, HashMap, HashSet},
+	collections::{BTreeMap, BTreeSet, HashMap, HashSet, VecDeque},
 	ops::Deref,
 	time::Duration,
 };
@@ -31,6 +31,7 @@ use ruma::{
 	events::{
 		AnyRawAccountDataEvent, AnySyncEphemeralRoomEvent, StateEventType, TimelineEventType,
 		room::member::{MembershipState, RoomMemberEventContent},
+		typing::TypingEventContent,
 	},
 	serde::Raw,
 	uint,
@@ -39,7 +40,9 @@ use ruma::{
 use super::share_encrypted_room;
 use crate::{
 	Ruma,
-	client::{DEFAULT_BUMP_TYPES, ignored_filter, is_ignored_invite, sync::load_timeline},
+	client::{
+		DEFAULT_BUMP_TYPES, TimelinePdus, ignored_filter, is_ignored_invite, sync::load_timeline,
+	},
 };
 
 type SyncInfo<'a> = (&'a UserId, &'a DeviceId, u64, &'a sync_events::v5::Request);
@@ -210,6 +213,9 @@ pub(crate) async fn sync_events_v5_route(
 		_ = tokio::time::timeout(duration, watcher).await;
 	}
 
+	let typing = collect_typing_events(services, sender_user, &body, &todo_rooms).await?;
+	response.extensions.typing = typing;
+
 	trace!(
 		rooms = ?response.rooms.len(),
 		account_data = ?response.extensions.account_data.rooms.len(),
@@ -293,6 +299,8 @@ where
 	Rooms: Iterator<Item = &'a RoomId> + Clone + Send + 'a,
 	AllRooms: Iterator<Item = &'a RoomId> + Clone + Send + 'a,
 {
+	// TODO MSC4186: Implement remaining list filters: is_dm, is_encrypted,
+	// room_types.
 	for (list_id, list) in &body.lists {
 		let active_rooms: Vec<_> = match list.filters.as_ref().and_then(|f| f.is_invite) {
 			| None => all_rooms.clone().collect(),
@@ -409,13 +417,13 @@ where
 				.await
 				.ok();
 
-			(timeline_pdus, limited) = (Vec::new(), true);
+			(timeline_pdus, limited) = (VecDeque::new(), true);
 		} else {
-			(timeline_pdus, limited) = match load_timeline(
+			TimelinePdus { pdus: timeline_pdus, limited } = match load_timeline(
 				services,
 				sender_user,
 				room_id,
-				roomsincecount,
+				Some(roomsincecount),
 				Some(PduCount::from(next_batch)),
 				*timeline_limit,
 			)
@@ -434,7 +442,7 @@ where
 				room_id.to_owned(),
 				services
 					.account_data
-					.changes_since(Some(room_id), sender_user, *roomsince, Some(next_batch))
+					.changes_since(Some(room_id), sender_user, Some(*roomsince), Some(next_batch))
 					.ready_filter_map(|e| extract_variant!(e, AnyRawAccountDataEvent::Room))
 					.collect()
 					.await,
@@ -460,11 +468,11 @@ where
 		let mut receipts: Vec<Raw<AnySyncEphemeralRoomEvent>> = services
 			.rooms
 			.read_receipt
-			.readreceipts_since(room_id, *roomsince)
+			.readreceipts_since(room_id, Some(*roomsince))
 			.filter_map(|(read_user, _ts, v)| async move {
 				services
 					.users
-					.user_is_ignored(read_user, sender_user)
+					.user_is_ignored(&read_user, sender_user)
 					.await
 					.or_some(v)
 			})
@@ -499,7 +507,7 @@ where
 		}
 
 		let prev_batch = timeline_pdus
-			.first()
+			.front()
 			.map_or(Ok::<_, Error>(None), |(pdu_count, _)| {
 				Ok(Some(match pdu_count {
 					| PduCount::Backfilled(_) => {
@@ -672,6 +680,62 @@ where
 	}
 	Ok(rooms)
 }
+
+async fn collect_typing_events(
+	services: &Services,
+	sender_user: &UserId,
+	body: &sync_events::v5::Request,
+	todo_rooms: &TodoRooms,
+) -> Result<sync_events::v5::response::Typing> {
+	if !body.extensions.typing.enabled.unwrap_or(false) {
+		return Ok(sync_events::v5::response::Typing::default());
+	}
+	let rooms: Vec<_> = body.extensions.typing.rooms.clone().unwrap_or_else(|| {
+		body.room_subscriptions
+			.keys()
+			.map(ToOwned::to_owned)
+			.collect()
+	});
+	let lists: Vec<_> = body
+		.extensions
+		.typing
+		.lists
+		.clone()
+		.unwrap_or_else(|| body.lists.keys().map(ToOwned::to_owned).collect::<Vec<_>>());
+
+	if rooms.is_empty() && lists.is_empty() {
+		return Ok(sync_events::v5::response::Typing::default());
+	}
+
+	let mut typing_response = sync_events::v5::response::Typing::default();
+	for (room_id, (_, _, roomsince)) in todo_rooms {
+		if services.rooms.typing.last_typing_update(room_id).await? <= *roomsince {
+			continue;
+		}
+
+		match services
+			.rooms
+			.typing
+			.typing_users_for_user(room_id, sender_user)
+			.await
+		{
+			| Ok(typing_users) => {
+				typing_response.rooms.insert(
+					room_id.to_owned(), // Already OwnedRoomId
+					Raw::new(&sync_events::v5::response::SyncTypingEvent {
+						content: TypingEventContent::new(typing_users),
+					})?,
+				);
+			},
+			| Err(e) => {
+				warn!(%room_id, "Failed to get typing events for room: {}", e);
+			},
+		}
+	}
+
+	Ok(typing_response)
+}
+
 async fn collect_account_data(
 	services: &Services,
 	(sender_user, _, globalsince, body): (&UserId, &DeviceId, u64, &sync_events::v5::Request),
@@ -687,7 +751,7 @@ async fn collect_account_data(
 
 	account_data.global = services
 		.account_data
-		.changes_since(None, sender_user, globalsince, None)
+		.changes_since(None, sender_user, Some(globalsince), None)
 		.ready_filter_map(|e| extract_variant!(e, AnyRawAccountDataEvent::Global))
 		.collect()
 		.await;
@@ -698,7 +762,7 @@ async fn collect_account_data(
 				room.clone(),
 				services
 					.account_data
-					.changes_since(Some(room), sender_user, globalsince, None)
+					.changes_since(Some(room), sender_user, Some(globalsince), None)
 					.ready_filter_map(|e| extract_variant!(e, AnyRawAccountDataEvent::Room))
 					.collect()
 					.await,
@@ -732,7 +796,7 @@ where
 	device_list_changes.extend(
 		services
 			.users
-			.keys_changed(sender_user, globalsince, None)
+			.keys_changed(sender_user, Some(globalsince), None)
 			.map(ToOwned::to_owned)
 			.collect::<Vec<_>>()
 			.await,
@@ -868,7 +932,7 @@ where
 		device_list_changes.extend(
 			services
 				.users
-				.room_keys_changed(room_id, globalsince, None)
+				.room_keys_changed(room_id, Some(globalsince), None)
 				.map(|(user_id, _)| user_id)
 				.map(ToOwned::to_owned)
 				.collect::<Vec<_>>()

src/api/client/unversioned.rs

@@ -52,7 +52,6 @@ pub(crate) async fn get_supported_versions_route(
 			("org.matrix.msc3026.busy_presence".to_owned(), true), /* busy presence status (https://github.com/matrix-org/matrix-spec-proposals/pull/3026) */
 			("org.matrix.msc3827".to_owned(), true), /* filtering of /publicRooms by room type (https://github.com/matrix-org/matrix-spec-proposals/pull/3827) */
 			("org.matrix.msc3952_intentional_mentions".to_owned(), true), /* intentional mentions (https://github.com/matrix-org/matrix-spec-proposals/pull/3952) */
-			("org.matrix.msc3575".to_owned(), true), /* sliding sync (https://github.com/matrix-org/matrix-spec-proposals/pull/3575/files#r1588877046) */
 			("org.matrix.msc3916.stable".to_owned(), true), /* authenticated media (https://github.com/matrix-org/matrix-spec-proposals/pull/3916) */
 			("org.matrix.msc4180".to_owned(), true), /* stable flag for 3916 (https://github.com/matrix-org/matrix-spec-proposals/pull/4180) */
 			("uk.tcpip.msc4133".to_owned(), true), /* Extending User Profile API with Key:Value Pairs (https://github.com/matrix-org/matrix-spec-proposals/pull/4133) */

src/api/router.rs

@@ -143,7 +143,6 @@ pub fn build(router: Router<State>, server: &Server) -> Router<State> {
 				.put(client::send_state_event_for_empty_key_route),
 		)
 		.ruma_route(&client::sync_events_route)
-		.ruma_route(&client::sync_events_v4_route)
 		.ruma_route(&client::sync_events_v5_route)
 		.ruma_route(&client::get_context_route)
 		.ruma_route(&client::get_message_events_route)

src/api/server/invite.rs

@@ -10,7 +10,6 @@ use conduwuit::{
 use ruma::{
 	CanonicalJsonValue, OwnedUserId, UserId,
 	api::{client::error::ErrorKind, federation::membership::create_invite},
-	events::room::member::{MembershipState, RoomMemberEventContent},
 	serde::JsonObject,
 };
 
@@ -133,17 +132,21 @@ pub(crate) async fn create_invite_route(
 		services
 			.rooms
 			.state_cache
-			.update_membership(
-				&body.room_id,
+			.mark_as_invited(
 				&recipient_user,
-				RoomMemberEventContent::new(MembershipState::Invite),
+				&body.room_id,
 				sender_user,
 				Some(invite_state),
 				body.via.clone(),
-				true,
 			)
 			.await?;
 
+		services
+			.rooms
+			.state_cache
+			.update_joined_count(&body.room_id)
+			.await;
+
 		for appservice in services.appservice.read().await.values() {
 			if appservice.is_user_match(&recipient_user) {
 				services

src/core/matrix/state_res/event_auth.rs

@@ -908,7 +908,7 @@ where
 							false
 						}
 					},
-					| JoinRule::Restricted(_) =>
+					| JoinRule::Restricted(_) => {
 						if membership_allows_join || user_for_join_auth_is_valid {
 							trace!(
 								%sender,
@@ -928,7 +928,8 @@ where
 								 valid authorising user given to permit the join"
 							);
 							false
-						},
+						}
+					},
 					| JoinRule::Public => {
 						trace!(%sender, "join rule is public, allowing join");
 						true

src/core/utils/future/try_ext_ext.rs

@@ -36,7 +36,7 @@ where
 	) -> MapOkOrElse<Self, impl FnOnce(Self::Ok) -> U, impl FnOnce(Self::Error) -> U>
 	where
 		F: FnOnce(Self::Ok) -> U,
-		Self: Send + Sized;
+		Self: Sized;
 
 	fn ok(
 		self,
@@ -100,7 +100,7 @@ where
 	) -> MapOkOrElse<Self, impl FnOnce(Self::Ok) -> U, impl FnOnce(Self::Error) -> U>
 	where
 		F: FnOnce(Self::Ok) -> U,
-		Self: Send + Sized,
+		Self: Sized,
 	{
 		self.map_ok_or_else(|_| default, f)
 	}

src/service/account_data/mod.rs

@@ -129,13 +129,14 @@ pub fn changes_since<'a>(
 	&'a self,
 	room_id: Option<&'a RoomId>,
 	user_id: &'a UserId,
-	since: u64,
+	since: Option<u64>,
 	to: Option<u64>,
 ) -> impl Stream<Item = AnyRawAccountDataEvent> + Send + 'a {
 	type Key<'a> = (Option<&'a RoomId>, &'a UserId, u64, Ignore);
 
 	// Skip the data that's exactly at since, because we sent that last time
-	let first_possible = (room_id, user_id, since.saturating_add(1));
+	// ...unless this is an initial sync, in which case send everything
+	let first_possible = (room_id, user_id, since.map_or(0, |since| since.saturating_add(1)));
 
 	self.db
 		.roomuserdataid_accountdata

src/service/migrations.rs

@@ -1,7 +1,7 @@
-use std::cmp;
+use std::{cmp, collections::HashMap};
 
 use conduwuit::{
-	Err, Result, debug, debug_info, debug_warn, error, info,
+	Err, Pdu, Result, debug, debug_info, debug_warn, error, info,
 	result::NotFound,
 	utils::{
 		IterStream, ReadyExt,
@@ -13,14 +13,16 @@ use database::Json;
 use futures::{FutureExt, StreamExt, TryStreamExt};
 use itertools::Itertools;
 use ruma::{
-	OwnedUserId, RoomId, UserId,
+	OwnedRoomId, OwnedUserId, RoomId, UserId,
 	events::{
-		GlobalAccountDataEventType, push_rules::PushRulesEvent, room::member::MembershipState,
+		GlobalAccountDataEventType, StateEventType, push_rules::PushRulesEvent,
+		room::member::MembershipState,
 	},
 	push::Ruleset,
+	serde::Raw,
 };
 
-use crate::{Services, media};
+use crate::{Services, media, rooms::short::ShortStateHash};
 
 /// The current schema version.
 /// - If database is opened at greater version we reject with error. The
@@ -152,6 +154,14 @@ async fn migrate(services: &Services) -> Result<()> {
 		info!("Migration: Bumped database version to 18");
 	}
 
+	if db["global"]
+		.get(POPULATED_USERROOMID_LEFTSTATE_TABLE_MARKER)
+		.await
+		.is_not_found()
+	{
+		populate_userroomid_leftstate_table(services).await?;
+	}
+
 	assert_eq!(
 		services.globals.db.database_version().await,
 		DATABASE_VERSION,
@@ -456,7 +466,11 @@ async fn retroactively_fix_bad_data_from_roomuserid_joined(services: &Services)
 
 		for user_id in &non_joined_members {
 			debug_info!("User is left or banned, marking as left");
-			services.rooms.state_cache.mark_as_left(user_id, room_id);
+			services
+				.rooms
+				.state_cache
+				.mark_as_left(user_id, room_id, None)
+				.await;
 		}
 	}
 
@@ -624,3 +638,78 @@ async fn fix_corrupt_msc4133_fields(services: &Services) -> Result {
 	db.db.sort()?;
 	Ok(())
 }
+
+const POPULATED_USERROOMID_LEFTSTATE_TABLE_MARKER: &str = "populate_userroomid_leftstate_table";
+async fn populate_userroomid_leftstate_table(services: &Services) -> Result {
+	type KeyVal<'a> = (Key<'a>, Raw<Option<Pdu>>);
+	type Key<'a> = (&'a UserId, &'a RoomId);
+
+	let db = &services.db;
+	let cork = db.cork_and_sync();
+	let userroomid_leftstate = db["userroomid_leftstate"].clone();
+
+	let (total, fixed, _) = userroomid_leftstate
+		.stream()
+		.try_fold(
+			(0_usize, 0_usize, HashMap::<OwnedRoomId, ShortStateHash>::new()),
+			async |(mut total, mut fixed, mut shortstatehash_cache): (
+				usize,
+				usize,
+				HashMap<_, _>,
+			),
+			       ((user_id, room_id), state): KeyVal<'_>|
+			       -> Result<(usize, usize, HashMap<_, _>)> {
+				if state.deserialize().is_err() {
+					let latest_shortstatehash =
+						if let Some(shortstatehash) = shortstatehash_cache.get(room_id) {
+							*shortstatehash
+						} else if let Ok(shortstatehash) =
+							services.rooms.state.get_room_shortstatehash(room_id).await
+						{
+							shortstatehash_cache.insert(room_id.to_owned(), shortstatehash);
+							shortstatehash
+						} else {
+							warn!(?room_id, ?user_id, "room has no shortstatehash");
+							return Ok((total, fixed, shortstatehash_cache));
+						};
+
+					let leave_state_event = services
+						.rooms
+						.state_accessor
+						.state_get(
+							latest_shortstatehash,
+							&StateEventType::RoomMember,
+							user_id.as_str(),
+						)
+						.await;
+
+					match leave_state_event {
+						| Ok(leave_state_event) => {
+							userroomid_leftstate.put((user_id, room_id), Json(leave_state_event));
+							fixed = fixed.saturating_add(1);
+						},
+						| Err(_) => {
+							warn!(
+								?room_id,
+								?user_id,
+								"room cached as left has no leave event for user, removing \
+								 cache entry"
+							);
+							userroomid_leftstate.del((user_id, room_id));
+						},
+					}
+				}
+
+				total = total.saturating_add(1);
+				Ok((total, fixed, shortstatehash_cache))
+			},
+		)
+		.await?;
+
+	drop(cork);
+	info!(?total, ?fixed, "Fixed entries in `userroomid_leftstate`.");
+
+	db["global"].insert(POPULATED_USERROOMID_LEFTSTATE_TABLE_MARKER, []);
+	db.db.sort()?;
+	Ok(())
+}

src/service/rooms/lazy_loading/mod.rs

@@ -39,7 +39,7 @@ pub enum Status {
 	Seen(u64),
 }
 
-pub type Witness = HashSet<OwnedUserId>;
+pub type MemberSet = HashSet<OwnedUserId>;
 type Key<'a> = (&'a UserId, Option<&'a DeviceId>, &'a RoomId, &'a UserId);
 
 impl crate::Service for Service {
@@ -67,9 +67,11 @@ pub async fn reset(&self, ctx: &Context<'_>) {
 		.await;
 }
 
+/// Returns only the subset of `senders` which should be sent to the client
+/// according to the provided lazy loading context.
 #[implement(Service)]
 #[tracing::instrument(name = "retain", level = "debug", skip_all)]
-pub async fn witness_retain(&self, senders: Witness, ctx: &Context<'_>) -> Witness {
+pub async fn retain_lazy_members(&self, senders: MemberSet, ctx: &Context<'_>) -> MemberSet {
 	debug_assert!(
 		ctx.options.is_none_or(Options::is_enabled),
 		"lazy loading should be enabled by your options"
@@ -84,7 +86,7 @@ pub async fn witness_retain(&self, senders: Witness, ctx: &Context<'_>) -> Witne
 
 	pin_mut!(witness);
 	let _cork = self.db.db.cork();
-	let mut senders = Witness::with_capacity(senders.len());
+	let mut senders = MemberSet::with_capacity(senders.len());
 	while let Some((status, sender)) = witness.next().await {
 		if include_redundant || status == Status::Unseen {
 			senders.insert(sender.into());

src/service/rooms/read_receipt/data.rs

@@ -7,7 +7,7 @@ use conduwuit::{
 use database::{Deserialized, Json, Map};
 use futures::{Stream, StreamExt};
 use ruma::{
-	CanonicalJsonObject, RoomId, UserId,
+	CanonicalJsonObject, OwnedUserId, RoomId, UserId,
 	events::{AnySyncEphemeralRoomEvent, receipt::ReceiptEvent},
 	serde::Raw,
 };
@@ -25,7 +25,7 @@ struct Services {
 	globals: Dep<globals::Service>,
 }
 
-pub(super) type ReceiptItem<'a> = (&'a UserId, u64, Raw<AnySyncEphemeralRoomEvent>);
+pub(super) type ReceiptItem = (OwnedUserId, u64, Raw<AnySyncEphemeralRoomEvent>);
 
 impl Data {
 	pub(super) fn new(args: &crate::Args<'_>) -> Self {
@@ -65,7 +65,7 @@ impl Data {
 		&'a self,
 		room_id: &'a RoomId,
 		since: u64,
-	) -> impl Stream<Item = ReceiptItem<'a>> + Send + 'a {
+	) -> impl Stream<Item = ReceiptItem> + Send + 'a {
 		type Key<'a> = (&'a RoomId, u64, &'a UserId);
 		type KeyVal<'a> = (Key<'a>, CanonicalJsonObject);
 
@@ -81,7 +81,7 @@ impl Data {
 
 				let event = serde_json::value::to_raw_value(&json)?;
 
-				Ok((user_id, count, Raw::from_json(event)))
+				Ok((user_id.to_owned(), count, Raw::from_json(event)))
 			})
 			.ignore_err()
 	}

src/service/rooms/read_receipt/mod.rs

@@ -104,16 +104,16 @@ impl Service {
 		Ok(Raw::from_json(event))
 	}
 
-	/// Returns an iterator over the most recent read_receipts in a room that
-	/// happened after the event with id `since`.
+	/// Returns an iterator over the most recent read_receipts in a room,
+	/// optionally after the event with id `since`.
 	#[inline]
 	#[tracing::instrument(skip(self), level = "debug")]
 	pub fn readreceipts_since<'a>(
 		&'a self,
 		room_id: &'a RoomId,
-		since: u64,
-	) -> impl Stream<Item = ReceiptItem<'a>> + Send + 'a {
-		self.db.readreceipts_since(room_id, since)
+		since: Option<u64>,
+	) -> impl Stream<Item = ReceiptItem> + Send + 'a {
+		self.db.readreceipts_since(room_id, since.unwrap_or(0))
 	}
 
 	/// Sets a private read marker at PDU `count`.

src/service/rooms/short/mod.rs

@@ -1,10 +1,18 @@
 use std::{borrow::Borrow, fmt::Debug, mem::size_of_val, sync::Arc};
 
 pub use conduwuit::matrix::pdu::{ShortEventId, ShortId, ShortRoomId, ShortStateKey};
-use conduwuit::{Result, err, implement, matrix::StateKey, utils, utils::IterStream};
+use conduwuit::{
+	Result, err, implement,
+	matrix::StateKey,
+	pair_of,
+	utils::{self, IterStream, ReadyExt},
+};
 use database::{Deserialized, Get, Map, Qry};
-use futures::{Stream, StreamExt};
-use ruma::{EventId, RoomId, events::StateEventType};
+use futures::{
+	Stream, StreamExt,
+	stream::{self},
+};
+use ruma::{EventId, OwnedEventId, RoomId, events::StateEventType};
 use serde::Deserialize;
 
 use crate::{Dep, globals};
@@ -258,3 +266,23 @@ pub async fn get_or_create_shortroomid(&self, room_id: &RoomId) -> ShortRoomId {
 			short
 		})
 }
+
+#[implement(Service)]
+pub async fn multi_get_state_from_short<'a, S>(
+	&'a self,
+	short_state: S,
+) -> impl Stream<Item = Result<((StateEventType, StateKey), OwnedEventId)>> + Send + 'a
+where
+	S: Stream<Item = (ShortStateKey, ShortEventId)> + Send + 'a,
+{
+	let (short_state_keys, short_event_ids): pair_of!(Vec<_>) = short_state.unzip().await;
+
+	StreamExt::zip(
+		self.multi_get_statekey_from_short(stream::iter(short_state_keys.into_iter())),
+		self.multi_get_eventid_from_short(stream::iter(short_event_ids.into_iter())),
+	)
+	.ready_filter_map(|state_event| match state_event {
+		| (Ok(state_key), Ok(event_id)) => Some(Ok((state_key, event_id))),
+		| (Err(e), _) | (_, Err(e)) => Some(Err(e)),
+	})
+}

src/service/rooms/state/mod.rs

@@ -20,7 +20,7 @@ use ruma::{
 	EventId, OwnedEventId, OwnedRoomId, RoomId, RoomVersionId, UserId,
 	events::{
 		AnyStrippedStateEvent, StateEventType, TimelineEventType,
-		room::{create::RoomCreateEventContent, member::RoomMemberEventContent},
+		room::create::RoomCreateEventContent,
 	},
 	serde::Raw,
 };
@@ -126,21 +126,9 @@ impl Service {
 						continue;
 					};
 
-					let Ok(membership_event) = pdu.get_content::<RoomMemberEventContent>() else {
-						continue;
-					};
-
 					self.services
 						.state_cache
-						.update_membership(
-							room_id,
-							user_id,
-							membership_event,
-							&pdu.sender,
-							None,
-							None,
-							false,
-						)
+						.update_membership(room_id, user_id, &pdu, false)
 						.await?;
 				},
 				| TimelineEventType::SpaceChild => {

src/service/rooms/state_accessor/state.rs

@@ -1,7 +1,7 @@
 use std::{borrow::Borrow, ops::Deref, sync::Arc};
 
 use conduwuit::{
-	Result, at, err, implement,
+	Pdu, Result, at, err, implement,
 	matrix::{Event, StateKey},
 	pair_of,
 	utils::{
@@ -10,7 +10,7 @@ use conduwuit::{
 	},
 };
 use database::Deserialized;
-use futures::{FutureExt, Stream, StreamExt, TryFutureExt, future::try_join, pin_mut};
+use futures::{FutureExt, Stream, StreamExt, TryFutureExt, pin_mut};
 use ruma::{
 	EventId, OwnedEventId, UserId,
 	events::{
@@ -125,7 +125,7 @@ pub async fn state_get(
 	shortstatehash: ShortStateHash,
 	event_type: &StateEventType,
 	state_key: &str,
-) -> Result<impl Event> {
+) -> Result<Pdu> {
 	self.state_get_id(shortstatehash, event_type, state_key)
 		.and_then(async |event_id: OwnedEventId| self.services.timeline.get_pdu(&event_id).await)
 		.await
@@ -286,28 +286,28 @@ pub fn state_keys<'a>(
 /// not in .1)
 #[implement(super::Service)]
 #[inline]
-pub fn state_removed(
+pub async fn state_removed(
 	&self,
 	shortstatehash: pair_of!(ShortStateHash),
-) -> impl Stream<Item = (ShortStateKey, ShortEventId)> + Send + '_ {
-	self.state_added((shortstatehash.1, shortstatehash.0))
+) -> Result<Vec<(ShortStateKey, ShortEventId)>> {
+	self.state_added((shortstatehash.1, shortstatehash.0)).await
 }
 
 /// Returns the state events added between the interval (present in .1 but
 /// not in .0)
 #[implement(super::Service)]
-pub fn state_added(
+pub async fn state_added(
 	&self,
 	shortstatehash: pair_of!(ShortStateHash),
-) -> impl Stream<Item = (ShortStateKey, ShortEventId)> + Send + '_ {
-	let a = self.load_full_state(shortstatehash.0);
-	let b = self.load_full_state(shortstatehash.1);
-	try_join(a, b)
-		.map_ok(|(a, b)| b.difference(&a).copied().collect::<Vec<_>>())
-		.map_ok(IterStream::try_stream)
-		.try_flatten_stream()
-		.ignore_err()
+) -> Result<Vec<(ShortStateKey, ShortEventId)>> {
+	let full_state_a = self.load_full_state(shortstatehash.0).await?;
+	let full_state_b = self.load_full_state(shortstatehash.1).await?;
+
+	Ok(full_state_b
+		.difference(&full_state_a)
+		.copied()
 		.map(parse_compressed_state_event)
+		.collect())
 }
 
 #[implement(super::Service)]

src/service/rooms/state_cache/mod.rs

@@ -4,7 +4,7 @@ mod via;
 use std::{collections::HashMap, sync::Arc};
 
 use conduwuit::{
-	Result, SyncRwLock, implement,
+	Pdu, Result, SyncRwLock, implement,
 	result::LogErr,
 	utils::{ReadyExt, stream::TryIgnore},
 	warn,
@@ -13,7 +13,7 @@ use database::{Deserialized, Ignore, Interfix, Map};
 use futures::{Stream, StreamExt, future::join5, pin_mut};
 use ruma::{
 	OwnedRoomId, OwnedUserId, RoomId, ServerName, UserId,
-	events::{AnyStrippedStateEvent, AnySyncStateEvent, room::member::MembershipState},
+	events::{AnyStrippedStateEvent, room::member::MembershipState},
 	serde::Raw,
 };
 
@@ -54,7 +54,6 @@ struct Data {
 
 type AppServiceInRoomCache = SyncRwLock<HashMap<OwnedRoomId, HashMap<String, bool>>>;
 type StrippedStateEventItem = (OwnedRoomId, Vec<Raw<AnyStrippedStateEvent>>);
-type SyncStateEventItem = (OwnedRoomId, Vec<Raw<AnySyncStateEvent>>);
 
 impl crate::Service for Service {
 	fn build(args: crate::Args<'_>) -> Result<Arc<Self>> {
@@ -431,18 +430,9 @@ pub async fn knock_state(
 
 #[implement(Service)]
 #[tracing::instrument(skip(self), level = "trace")]
-pub async fn left_state(
-	&self,
-	user_id: &UserId,
-	room_id: &RoomId,
-) -> Result<Vec<Raw<AnyStrippedStateEvent>>> {
+pub async fn left_state(&self, user_id: &UserId, room_id: &RoomId) -> Result<Option<Pdu>> {
 	let key = (user_id, room_id);
-	self.db
-		.userroomid_leftstate
-		.qry(&key)
-		.await
-		.deserialized()
-		.and_then(|val: Raw<Vec<AnyStrippedStateEvent>>| val.deserialize_as().map_err(Into::into))
+	self.db.userroomid_leftstate.qry(&key).await.deserialized()
 }
 
 /// Returns an iterator over all rooms a user left.
@@ -451,8 +441,8 @@ pub async fn left_state(
 pub fn rooms_left<'a>(
 	&'a self,
 	user_id: &'a UserId,
-) -> impl Stream<Item = SyncStateEventItem> + Send + 'a {
-	type KeyVal<'a> = (Key<'a>, Raw<Vec<Raw<AnySyncStateEvent>>>);
+) -> impl Stream<Item = (OwnedRoomId, Option<Pdu>)> + Send + 'a {
+	type KeyVal<'a> = (Key<'a>, Raw<Option<Pdu>>);
 	type Key<'a> = (&'a UserId, &'a RoomId);
 
 	let prefix = (user_id, Interfix);
@@ -461,7 +451,7 @@ pub fn rooms_left<'a>(
 		.stream_prefix(&prefix)
 		.ignore_err()
 		.map(|((_, room_id), state): KeyVal<'_>| (room_id.to_owned(), state))
-		.map(|(room_id, state)| Ok((room_id, state.deserialize_as()?)))
+		.map(|(room_id, state)| Ok((room_id, state.deserialize()?)))
 		.ignore_err()
 }
 

src/service/rooms/state_cache/update.rs

@@ -1,13 +1,13 @@
 use std::collections::HashSet;
 
-use conduwuit::{Err, Result, implement, is_not_empty, utils::ReadyExt, warn};
+use conduwuit::{Err, Event, Pdu, Result, implement, is_not_empty, utils::ReadyExt, warn};
 use database::{Json, serialize_key};
 use futures::StreamExt;
 use ruma::{
 	OwnedServerName, RoomId, UserId,
 	events::{
-		AnyStrippedStateEvent, AnySyncStateEvent, GlobalAccountDataEventType,
-		RoomAccountDataEventType, StateEventType,
+		AnyStrippedStateEvent, GlobalAccountDataEventType, RoomAccountDataEventType,
+		StateEventType,
 		direct::DirectEvent,
 		invite_permission_config::FilterLevel,
 		room::{
@@ -26,8 +26,7 @@ use ruma::{
 		fields(
 			%room_id,
 			%user_id,
-			%sender,
-			?membership_event,
+			?pdu,
 		),
 	)]
 #[allow(clippy::too_many_arguments)]
@@ -35,13 +34,10 @@ pub async fn update_membership(
 	&self,
 	room_id: &RoomId,
 	user_id: &UserId,
-	membership_event: RoomMemberEventContent,
-	sender: &UserId,
-	last_state: Option<Vec<Raw<AnyStrippedStateEvent>>>,
-	invite_via: Option<Vec<OwnedServerName>>,
+	pdu: &Pdu,
 	update_joined_count: bool,
 ) -> Result {
-	let membership = membership_event.membership;
+	let membership = pdu.get_content::<RoomMemberEventContent>()?;
 
 	// Keep track what remote users exist by adding them as "deactivated" users
 	//
@@ -54,7 +50,7 @@ pub async fn update_membership(
 		}
 	}
 
-	match &membership {
+	match &membership.membership {
 		| MembershipState::Join => {
 			// Check if the user never joined this room
 			if !self.once_joined(user_id, room_id).await {
@@ -122,33 +118,14 @@ pub async fn update_membership(
 			self.mark_as_joined(user_id, room_id);
 		},
 		| MembershipState::Invite => {
-			// return an error for blocked invites. ignored invites aren't handled here
-			// since the recipient's membership should still be changed to `invite`.
-			// they're filtered out in the individual /sync handlers
-			if matches!(
-				self.services
-					.users
-					.invite_filter_level(sender, user_id)
-					.await,
-				FilterLevel::Block
-			) {
-				return Err!(Request(InviteBlocked(
-					"{user_id} has blocked invites from {sender}."
-				)));
-			}
-			self.mark_as_invited(user_id, room_id, sender, last_state, invite_via)
-				.await;
+			// TODO: make sure that passing None for `last_state` is correct behavior.
+			// the call from `append_pdu` used to use `services.state.summary_stripped`
+			// to fill that parameter.
+			self.mark_as_invited(user_id, room_id, pdu.sender(), None, None)
+				.await?;
 		},
 		| MembershipState::Leave | MembershipState::Ban => {
-			self.mark_as_left(user_id, room_id);
-
-			if self.services.globals.user_is_local(user_id)
-				&& (self.services.config.forget_forced_upon_leave
-					|| self.services.metadata.is_banned(room_id).await
-					|| self.services.metadata.is_disabled(room_id).await)
-			{
-				self.forget(room_id, user_id);
-			}
+			self.mark_as_left(user_id, room_id, Some(pdu.clone())).await;
 		},
 		| _ => {},
 	}
@@ -252,24 +229,24 @@ pub fn mark_as_joined(&self, user_id: &UserId, room_id: &RoomId) {
 	self.db.roomid_inviteviaservers.remove(room_id);
 }
 
-/// Direct DB function to directly mark a user as left. It is not
-/// recommended to use this directly. You most likely should use
-/// `update_membership` instead
+/// Mark a user as having left a room.
+///
+/// `leave_pdu` represents the m.room.member event which the user sent to leave
+/// the room. If this is None, no event was actually sent, but we must still
+/// behave as if the user is no longer in the room. This may occur, for example,
+/// if the room being left has been server-banned by an administrator.
 #[implement(super::Service)]
 #[tracing::instrument(skip(self), level = "debug")]
-pub fn mark_as_left(&self, user_id: &UserId, room_id: &RoomId) {
+pub async fn mark_as_left(&self, user_id: &UserId, room_id: &RoomId, leave_pdu: Option<Pdu>) {
 	let userroom_id = (user_id, room_id);
 	let userroom_id = serialize_key(userroom_id).expect("failed to serialize userroom_id");
 
 	let roomuser_id = (room_id, user_id);
 	let roomuser_id = serialize_key(roomuser_id).expect("failed to serialize roomuser_id");
 
-	// (timo) TODO
-	let leftstate = Vec::<Raw<AnySyncStateEvent>>::new();
-
 	self.db
 		.userroomid_leftstate
-		.raw_put(&userroom_id, Json(leftstate));
+		.raw_put(&userroom_id, Json(leave_pdu));
 	self.db
 		.roomuserid_leftcount
 		.raw_aput::<8, _, _>(&roomuser_id, self.services.globals.next_count().unwrap());
@@ -285,6 +262,14 @@ pub fn mark_as_left(&self, user_id: &UserId, room_id: &RoomId) {
 	self.db.roomuserid_knockedcount.remove(&roomuser_id);
 
 	self.db.roomid_inviteviaservers.remove(room_id);
+
+	if self.services.globals.user_is_local(user_id)
+		&& (self.services.config.forget_forced_upon_leave
+			|| self.services.metadata.is_banned(room_id).await
+			|| self.services.metadata.is_disabled(room_id).await)
+	{
+		self.forget(room_id, user_id);
+	}
 }
 
 /// Direct DB function to directly mark a user as knocked. It is not
@@ -351,7 +336,20 @@ pub async fn mark_as_invited(
 	sender_user: &UserId,
 	last_state: Option<Vec<Raw<AnyStrippedStateEvent>>>,
 	invite_via: Option<Vec<OwnedServerName>>,
-) {
+) -> Result<()> {
+	// return an error for blocked invites. ignored invites aren't handled here
+	// since the recipient's membership should still be changed to `invite`.
+	// they're filtered out in the individual /sync handlers
+	if matches!(
+		self.services
+			.users
+			.invite_filter_level(sender_user, user_id)
+			.await,
+		FilterLevel::Block
+	) {
+		return Err!(Request(InviteBlocked("{user_id} has blocked invites from {sender_user}.")));
+	}
+
 	let roomuser_id = (room_id, user_id);
 	let roomuser_id = serialize_key(roomuser_id).expect("failed to serialize roomuser_id");
 
@@ -366,7 +364,7 @@ pub async fn mark_as_invited(
 		.raw_aput::<8, _, _>(&roomuser_id, self.services.globals.next_count().unwrap());
 	self.db
 		.userroomid_invitesender
-		.raw_put(&userroom_id, sender_user);
+		.insert(&userroom_id, sender_user);
 
 	self.db.userroomid_joined.remove(&userroom_id);
 	self.db.roomuserid_joined.remove(&roomuser_id);
@@ -380,4 +378,6 @@ pub async fn mark_as_invited(
 	if let Some(servers) = invite_via.filter(is_not_empty!()) {
 		self.add_servers_invite_via(room_id, servers).await;
 	}
+
+	Ok(())
 }

src/service/rooms/state_compressor/mod.rs

@@ -526,7 +526,7 @@ pub(crate) fn compress_state_event(
 
 #[inline]
 #[must_use]
-pub(crate) fn parse_compressed_state_event(
+pub fn parse_compressed_state_event(
 	compressed_event: CompressedStateEvent,
 ) -> (ShortStateKey, ShortEventId) {
 	use utils::u64_from_u8;

src/service/rooms/timeline/append.rs

@@ -19,9 +19,7 @@ use ruma::{
 		GlobalAccountDataEventType, StateEventType, TimelineEventType,
 		push_rules::PushRulesEvent,
 		room::{
-			encrypted::Relation,
-			member::{MembershipState, RoomMemberEventContent},
-			power_levels::RoomPowerLevelsEventContent,
+			encrypted::Relation, power_levels::RoomPowerLevelsEventContent,
 			redaction::RoomRedactionEventContent,
 		},
 	},
@@ -323,31 +321,12 @@ where
 				let target_user_id =
 					UserId::parse(state_key).expect("This state_key was previously validated");
 
-				let content: RoomMemberEventContent = pdu.get_content()?;
-				let stripped_state = match content.membership {
-					| MembershipState::Invite | MembershipState::Knock => self
-						.services
-						.state
-						.summary_stripped(pdu, room_id)
-						.await
-						.into(),
-					| _ => None,
-				};
-
 				// Update our membership info, we do this here incase a user is invited or
 				// knocked and immediately leaves we need the DB to record the invite or
 				// knock event for auth
 				self.services
 					.state_cache
-					.update_membership(
-						room_id,
-						target_user_id,
-						content,
-						pdu.sender(),
-						stripped_state,
-						None,
-						true,
-					)
+					.update_membership(room_id, target_user_id, pdu, true)
 					.await?;
 			}
 		},

src/service/rooms/timeline/mod.rs

@@ -186,10 +186,8 @@ impl Service {
 	}
 
 	/// Returns the pdu.
-	///
-	/// Checks the `eventid_outlierpdu` Tree if not found in the timeline.
 	#[inline]
-	pub async fn get_non_outlier_pdu(&self, event_id: &EventId) -> Result<impl Event> {
+	pub async fn get_non_outlier_pdu(&self, event_id: &EventId) -> Result<PduEvent> {
 		self.db.get_non_outlier_pdu(event_id).await
 	}
 
@@ -243,7 +241,7 @@ impl Service {
 		self.pdus(Some(user_id), room_id, None).ignore_err()
 	}
 
-	/// Reverse iteration starting at from.
+	/// Reverse iteration starting after `until`.
 	#[tracing::instrument(skip(self), level = "debug")]
 	pub fn pdus_rev<'a>(
 		&'a self,
@@ -255,7 +253,7 @@ impl Service {
 			.pdus_rev(user_id, room_id, until.unwrap_or_else(PduCount::max))
 	}
 
-	/// Forward iteration starting at from.
+	/// Forward iteration starting after `from`.
 	#[tracing::instrument(skip(self), level = "debug")]
 	pub fn pdus<'a>(
 		&'a self,

src/service/rooms/typing/mod.rs

@@ -179,18 +179,15 @@ impl Service {
 			.unwrap_or(0))
 	}
 
-	/// Returns a new typing EDU.
-	pub async fn typings_all(
+	pub async fn typing_users_for_user(
 		&self,
 		room_id: &RoomId,
 		sender_user: &UserId,
-	) -> Result<SyncEphemeralRoomEvent<ruma::events::typing::TypingEventContent>> {
+	) -> Result<Vec<OwnedUserId>> {
 		let room_typing_indicators = self.typing.read().await.get(room_id).cloned();
 
 		let Some(typing_indicators) = room_typing_indicators else {
-			return Ok(SyncEphemeralRoomEvent {
-				content: ruma::events::typing::TypingEventContent { user_ids: Vec::new() },
-			});
+			return Ok(Vec::new());
 		};
 
 		let user_ids: Vec<_> = typing_indicators
@@ -207,8 +204,19 @@ impl Service {
 			.collect()
 			.await;
 
+		Ok(user_ids)
+	}
+
+	/// Returns a new typing EDU.
+	pub async fn typings_event_for_user(
+		&self,
+		room_id: &RoomId,
+		sender_user: &UserId,
+	) -> Result<SyncEphemeralRoomEvent<ruma::events::typing::TypingEventContent>> {
 		Ok(SyncEphemeralRoomEvent {
-			content: ruma::events::typing::TypingEventContent { user_ids },
+			content: ruma::events::typing::TypingEventContent {
+				user_ids: self.typing_users_for_user(room_id, sender_user).await?,
+			},
 		})
 	}
 

src/service/sending/sender.rs

@@ -423,7 +423,7 @@ impl Service {
 			let keys_changed = self
 				.services
 				.users
-				.room_keys_changed(room_id, since.0, None)
+				.room_keys_changed(room_id, Some(since.0), None)
 				.ready_filter(|(user_id, _)| self.services.globals.user_is_local(user_id));
 
 			pin_mut!(keys_changed);
@@ -520,7 +520,7 @@ impl Service {
 		let receipts = self
 			.services
 			.read_receipt
-			.readreceipts_since(room_id, since.0);
+			.readreceipts_since(room_id, Some(since.0));
 
 		pin_mut!(receipts);
 		let mut read = BTreeMap::<OwnedUserId, ReceiptData>::new();
@@ -530,7 +530,7 @@ impl Service {
 			}
 
 			max_edu_count.fetch_max(count, Ordering::Relaxed);
-			if !self.services.globals.user_is_local(user_id) {
+			if !self.services.globals.user_is_local(&user_id) {
 				continue;
 			}
 
@@ -554,7 +554,7 @@ impl Service {
 			let receipt = receipt
 				.remove(&ReceiptType::Read)
 				.expect("our read receipts always set this")
-				.remove(user_id)
+				.remove(&user_id)
 				.expect("our read receipts always have the user here");
 
 			let receipt_data = ReceiptData {
@@ -562,7 +562,7 @@ impl Service {
 				event_ids: vec![event_id.clone()],
 			};
 
-			if read.insert(user_id.to_owned(), receipt_data).is_none() {
+			if read.insert(user_id, receipt_data).is_none() {
 				*num = num.saturating_add(1);
 				if *num >= SELECT_RECEIPT_LIMIT {
 					break;

src/service/users/mod.rs

@@ -790,7 +790,7 @@ impl Service {
 	pub fn keys_changed<'a>(
 		&'a self,
 		user_id: &'a UserId,
-		from: u64,
+		from: Option<u64>,
 		to: Option<u64>,
 	) -> impl Stream<Item = &'a UserId> + Send + 'a {
 		self.keys_changed_user_or_room(user_id.as_str(), from, to)
@@ -801,7 +801,7 @@ impl Service {
 	pub fn room_keys_changed<'a>(
 		&'a self,
 		room_id: &'a RoomId,
-		from: u64,
+		from: Option<u64>,
 		to: Option<u64>,
 	) -> impl Stream<Item = (&'a UserId, u64)> + Send + 'a {
 		self.keys_changed_user_or_room(room_id.as_str(), from, to)
@@ -810,11 +810,12 @@ impl Service {
 	fn keys_changed_user_or_room<'a>(
 		&'a self,
 		user_or_room_id: &'a str,
-		from: u64,
+		from: Option<u64>,
 		to: Option<u64>,
 	) -> impl Stream<Item = (&'a UserId, u64)> + Send + 'a {
 		type KeyVal<'a> = ((&'a str, u64), &'a UserId);
 
+		let from = from.unwrap_or(0);
 		let to = to.unwrap_or(u64::MAX);
 		let start = (user_or_room_id, from.saturating_add(1));
 		self.db