refactor spaces

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

src/api/client/space.rs

@@ -1,18 +1,25 @@
-use std::{collections::VecDeque, str::FromStr};
+use std::{
+	collections::{BTreeSet, VecDeque},
+	str::FromStr,
+};
 
 use axum::extract::State;
-use conduwuit::{checked, pdu::ShortRoomId, utils::stream::IterStream};
-use futures::{StreamExt, TryFutureExt};
+use conduwuit::{
+	utils::{future::TryExtExt, stream::IterStream},
+	Err, Result,
+};
+use futures::{future::OptionFuture, StreamExt, TryFutureExt};
 use ruma::{
-	api::client::{error::ErrorKind, space::get_hierarchy},
-	OwnedRoomId, OwnedServerName, RoomId, UInt, UserId,
+	api::client::space::get_hierarchy, OwnedRoomId, OwnedServerName, RoomId, UInt, UserId,
 };
 use service::{
-	rooms::spaces::{get_parent_children_via, summary_to_chunk, SummaryAccessibility},
+	rooms::spaces::{
+		get_parent_children_via, summary_to_chunk, PaginationToken, SummaryAccessibility,
+	},
 	Services,
 };
 
-use crate::{service::rooms::spaces::PaginationToken, Error, Result, Ruma};
+use crate::Ruma;
 
 /// # `GET /_matrix/client/v1/rooms/{room_id}/hierarchy`
 ///
@@ -40,10 +47,9 @@ pub(crate) async fn get_hierarchy_route(
 	// Should prevent unexpeded behaviour in (bad) clients
 	if let Some(ref token) = key {
 		if token.suggested_only != body.suggested_only || token.max_depth != max_depth {
-			return Err(Error::BadRequest(
-				ErrorKind::InvalidParam,
-				"suggested_only and max_depth cannot change on paginated requests",
-			));
+			return Err!(Request(InvalidParam(
+				"suggested_only and max_depth cannot change on paginated requests"
+			)));
 		}
 	}
 
@@ -52,58 +58,70 @@ pub(crate) async fn get_hierarchy_route(
 		body.sender_user(),
 		&body.room_id,
 		limit.try_into().unwrap_or(10),
-		key.map_or(vec![], |token| token.short_room_ids),
-		max_depth.into(),
+		max_depth.try_into().unwrap_or(usize::MAX),
 		body.suggested_only,
+		key.as_ref()
+			.into_iter()
+			.flat_map(|t| t.short_room_ids.iter()),
 	)
 	.await
 }
 
-async fn get_client_hierarchy(
+async fn get_client_hierarchy<'a, ShortRoomIds>(
 	services: &Services,
 	sender_user: &UserId,
 	room_id: &RoomId,
 	limit: usize,
-	short_room_ids: Vec<ShortRoomId>,
-	max_depth: u64,
+	max_depth: usize,
 	suggested_only: bool,
-) -> Result<get_hierarchy::v1::Response> {
-	let mut parents = VecDeque::new();
+	short_room_ids: ShortRoomIds,
+) -> Result<get_hierarchy::v1::Response>
+where
+	ShortRoomIds: Iterator<Item = &'a u64> + Clone + Send + Sync + 'a,
+{
+	type Via = Vec<OwnedServerName>;
+	type Entry = (OwnedRoomId, Via);
+	type Rooms = VecDeque<Entry>;
 
-	// Don't start populating the results if we have to start at a specific room.
-	let mut populate_results = short_room_ids.is_empty();
+	let mut queue: Rooms = [(
+		room_id.to_owned(),
+		room_id
+			.server_name()
+			.map(ToOwned::to_owned)
+			.into_iter()
+			.collect(),
+	)]
+	.into();
 
-	let mut stack = vec![vec![(room_id.to_owned(), match room_id.server_name() {
-		| Some(server_name) => vec![server_name.into()],
-		| None => vec![],
-	})]];
+	let mut rooms = Vec::with_capacity(limit);
+	let mut parents = BTreeSet::new();
+	while let Some((current_room, via)) = queue.pop_front() {
+		let summary = services
+			.rooms
+			.spaces
+			.get_summary_and_children_client(&current_room, suggested_only, sender_user, &via)
+			.await?;
 
-	let mut results = Vec::with_capacity(limit);
-
-	while let Some((current_room, via)) = { next_room_to_traverse(&mut stack, &mut parents) } {
-		if results.len() >= limit {
-			break;
-		}
-
-		match (
-			services
-				.rooms
-				.spaces
-				.get_summary_and_children_client(&current_room, suggested_only, sender_user, &via)
-				.await?,
-			current_room == room_id,
-		) {
+		match (summary, current_room == room_id) {
+			| (None | Some(SummaryAccessibility::Inaccessible), false) => {
+				// Just ignore other unavailable rooms
+			},
+			| (None, true) => {
+				return Err!(Request(Forbidden("The requested room was not found")));
+			},
+			| (Some(SummaryAccessibility::Inaccessible), true) => {
+				return Err!(Request(Forbidden("The requested room is inaccessible")));
+			},
 			| (Some(SummaryAccessibility::Accessible(summary)), _) => {
-				let mut children: Vec<(OwnedRoomId, Vec<OwnedServerName>)> =
-					get_parent_children_via(&summary, suggested_only)
-						.into_iter()
-						.filter(|(room, _)| parents.iter().all(|parent| parent != room))
-						.rev()
-						.collect();
+				let populate = parents.len() >= short_room_ids.clone().count();
 
-				if populate_results {
-					results.push(summary_to_chunk(*summary.clone()));
-				} else {
+				let mut children: Vec<Entry> = get_parent_children_via(&summary, suggested_only)
+					.filter(|(room, _)| !parents.contains(room))
+					.rev()
+					.map(|(key, val)| (key, val.collect()))
+					.collect();
+
+				if !populate {
 					children = children
 						.iter()
 						.rev()
@@ -113,97 +131,69 @@ async fn get_client_hierarchy(
 								.rooms
 								.short
 								.get_shortroomid(room)
-								.map_ok(|short| Some(&short) != short_room_ids.get(parents.len()))
+								.map_ok(|short| {
+									Some(&short) != short_room_ids.clone().nth(parents.len())
+								})
 								.unwrap_or_else(|_| false)
 						})
 						.map(Clone::clone)
-						.collect::<Vec<(OwnedRoomId, Vec<OwnedServerName>)>>()
+						.collect::<Vec<Entry>>()
 						.await
 						.into_iter()
 						.rev()
 						.collect();
-
-					if children.is_empty() {
-						return Err(Error::BadRequest(
-							ErrorKind::InvalidParam,
-							"Room IDs in token were not found.",
-						));
-					}
-
-					// We have reached the room after where we last left off
-					let parents_len = parents.len();
-					if checked!(parents_len + 1)? == short_room_ids.len() {
-						populate_results = true;
-					}
 				}
 
-				let parents_len: u64 = parents.len().try_into()?;
-				if !children.is_empty() && parents_len < max_depth {
-					parents.push_back(current_room.clone());
-					stack.push(children);
+				if populate {
+					rooms.push(summary_to_chunk(summary.clone()));
+				} else if queue.is_empty() && children.is_empty() {
+					return Err!(Request(InvalidParam("Room IDs in token were not found.")));
 				}
-				// Root room in the space hierarchy, we return an error
-				// if this one fails.
+
+				parents.insert(current_room.clone());
+				if rooms.len() >= limit {
+					break;
+				}
+
+				if children.is_empty() {
+					break;
+				}
+
+				if parents.len() >= max_depth {
+					continue;
+				}
+
+				queue.extend(children);
 			},
-			| (Some(SummaryAccessibility::Inaccessible), true) => {
-				return Err(Error::BadRequest(
-					ErrorKind::forbidden(),
-					"The requested room is inaccessible",
-				));
-			},
-			| (None, true) => {
-				return Err(Error::BadRequest(
-					ErrorKind::forbidden(),
-					"The requested room was not found",
-				));
-			},
-			// Just ignore other unavailable rooms
-			| (None | Some(SummaryAccessibility::Inaccessible), false) => (),
 		}
 	}
 
-	Ok(get_hierarchy::v1::Response {
-		next_batch: if let Some((room, _)) = next_room_to_traverse(&mut stack, &mut parents) {
-			parents.pop_front();
-			parents.push_back(room);
+	let next_batch: OptionFuture<_> = queue
+		.pop_front()
+		.map(|(room, _)| async move {
+			parents.insert(room);
 
 			let next_short_room_ids: Vec<_> = parents
 				.iter()
 				.stream()
-				.filter_map(|room_id| async move {
-					services.rooms.short.get_shortroomid(room_id).await.ok()
-				})
+				.filter_map(|room_id| services.rooms.short.get_shortroomid(room_id).ok())
 				.collect()
 				.await;
 
-			(next_short_room_ids != short_room_ids && !next_short_room_ids.is_empty()).then(
-				|| {
-					PaginationToken {
-						short_room_ids: next_short_room_ids,
-						limit: UInt::new(max_depth)
-							.expect("When sent in request it must have been valid UInt"),
-						max_depth: UInt::new(max_depth)
-							.expect("When sent in request it must have been valid UInt"),
-						suggested_only,
-					}
-					.to_string()
-				},
-			)
-		} else {
-			None
-		},
-		rooms: results,
+			(next_short_room_ids.iter().ne(short_room_ids) && !next_short_room_ids.is_empty())
+				.then_some(PaginationToken {
+					short_room_ids: next_short_room_ids,
+					limit: max_depth.try_into().ok()?,
+					max_depth: max_depth.try_into().ok()?,
+					suggested_only,
+				})
+				.as_ref()
+				.map(PaginationToken::to_string)
+		})
+		.into();
+
+	Ok(get_hierarchy::v1::Response {
+		next_batch: next_batch.await.flatten(),
+		rooms,
 	})
 }
-
-fn next_room_to_traverse(
-	stack: &mut Vec<Vec<(OwnedRoomId, Vec<OwnedServerName>)>>,
-	parents: &mut VecDeque<OwnedRoomId>,
-) -> Option<(OwnedRoomId, Vec<OwnedServerName>)> {
-	while stack.last().is_some_and(Vec::is_empty) {
-		stack.pop();
-		parents.pop_back();
-	}
-
-	stack.last_mut().and_then(Vec::pop)
-}

src/api/server/hierarchy.rs

@@ -1,10 +1,11 @@
 use axum::extract::State;
-use conduwuit::{Err, Result};
-use ruma::{api::federation::space::get_hierarchy, RoomId, ServerName};
-use service::{
-	rooms::spaces::{get_parent_children_via, Identifier, SummaryAccessibility},
-	Services,
+use conduwuit::{
+	utils::stream::{BroadbandExt, IterStream},
+	Err, Result,
 };
+use futures::{FutureExt, StreamExt};
+use ruma::api::federation::space::get_hierarchy;
+use service::rooms::spaces::{get_parent_children_via, Identifier, SummaryAccessibility};
 
 use crate::Ruma;
 
@@ -20,54 +21,51 @@ pub(crate) async fn get_hierarchy_route(
 		return Err!(Request(NotFound("Room does not exist.")));
 	}
 
-	get_hierarchy(&services, &body.room_id, body.origin(), body.suggested_only).await
-}
-
-/// Gets the response for the space hierarchy over federation request
-///
-/// Errors if the room does not exist, so a check if the room exists should
-/// be done
-async fn get_hierarchy(
-	services: &Services,
-	room_id: &RoomId,
-	server_name: &ServerName,
-	suggested_only: bool,
-) -> Result<get_hierarchy::v1::Response> {
+	let room_id = &body.room_id;
+	let suggested_only = body.suggested_only;
+	let ref identifier = Identifier::ServerName(body.origin());
 	match services
 		.rooms
 		.spaces
-		.get_summary_and_children_local(&room_id.to_owned(), Identifier::ServerName(server_name))
+		.get_summary_and_children_local(room_id, identifier)
 		.await?
 	{
-		| Some(SummaryAccessibility::Accessible(room)) => {
-			let mut children = Vec::new();
-			let mut inaccessible_children = Vec::new();
+		| None => Err!(Request(NotFound("The requested room was not found"))),
 
-			for (child, _via) in get_parent_children_via(&room, suggested_only) {
-				match services
-					.rooms
-					.spaces
-					.get_summary_and_children_local(&child, Identifier::ServerName(server_name))
-					.await?
-				{
-					| Some(SummaryAccessibility::Accessible(summary)) => {
-						children.push((*summary).into());
-					},
-					| Some(SummaryAccessibility::Inaccessible) => {
-						inaccessible_children.push(child);
-					},
-					| None => (),
-				}
-			}
-
-			Ok(get_hierarchy::v1::Response {
-				room: *room,
-				children,
-				inaccessible_children,
-			})
-		},
 		| Some(SummaryAccessibility::Inaccessible) =>
 			Err!(Request(NotFound("The requested room is inaccessible"))),
-		| None => Err!(Request(NotFound("The requested room was not found"))),
+
+		| Some(SummaryAccessibility::Accessible(room)) => {
+			let (children, inaccessible_children) =
+				get_parent_children_via(&room, suggested_only)
+					.stream()
+					.broad_filter_map(|(child, _via)| async move {
+						match services
+							.rooms
+							.spaces
+							.get_summary_and_children_local(&child, identifier)
+							.await
+							.ok()?
+						{
+							| None => None,
+
+							| Some(SummaryAccessibility::Inaccessible) =>
+								Some((None, Some(child))),
+
+							| Some(SummaryAccessibility::Accessible(summary)) =>
+								Some((Some(summary), None)),
+						}
+					})
+					.unzip()
+					.map(|(children, inaccessible_children): (Vec<_>, Vec<_>)| {
+						(
+							children.into_iter().flatten().map(Into::into).collect(),
+							inaccessible_children.into_iter().flatten().collect(),
+						)
+					})
+					.await;
+
+			Ok(get_hierarchy::v1::Response { room, children, inaccessible_children })
+		},
 	}
 }

src/service/rooms/spaces/mod.rs

@@ -1,14 +1,24 @@
 mod pagination_token;
+#[cfg(test)]
 mod tests;
 
-use std::{collections::HashMap, sync::Arc};
+use std::sync::Arc;
 
-use conduwuit::{debug_info, err, utils::math::usize_from_f64, Error, Result};
-use futures::StreamExt;
+use conduwuit::{
+	implement,
+	utils::{
+		future::BoolExt,
+		math::usize_from_f64,
+		stream::{BroadbandExt, ReadyExt},
+		IterStream,
+	},
+	Err, Error, Result,
+};
+use futures::{pin_mut, stream::FuturesUnordered, FutureExt, Stream, StreamExt, TryFutureExt};
 use lru_cache::LruCache;
 use ruma::{
 	api::{
-		client::{error::ErrorKind, space::SpaceHierarchyRoomsChunk},
+		client::space::SpaceHierarchyRoomsChunk,
 		federation::{
 			self,
 			space::{SpaceHierarchyChildSummary, SpaceHierarchyParentSummary},
@@ -21,46 +31,46 @@ use ruma::{
 	},
 	serde::Raw,
 	space::SpaceRoomJoinRule,
-	OwnedRoomId, OwnedServerName, RoomId, ServerName, UserId,
+	OwnedEventId, OwnedRoomId, OwnedServerName, RoomId, ServerName, UserId,
 };
-use tokio::sync::Mutex;
+use tokio::sync::{Mutex, MutexGuard};
 
 pub use self::pagination_token::PaginationToken;
-use crate::{rooms, sending, Dep};
-
-pub struct CachedSpaceHierarchySummary {
-	summary: SpaceHierarchyParentSummary,
-}
-
-pub enum SummaryAccessibility {
-	Accessible(Box<SpaceHierarchyParentSummary>),
-	Inaccessible,
-}
-
-/// Identifier used to check if rooms are accessible
-///
-/// None is used if you want to return the room, no matter if accessible or not
-pub enum Identifier<'a> {
-	UserId(&'a UserId),
-	ServerName(&'a ServerName),
-}
+use crate::{conduwuit::utils::TryFutureExtExt, rooms, sending, Dep};
 
 pub struct Service {
 	services: Services,
-	pub roomid_spacehierarchy_cache:
-		Mutex<LruCache<OwnedRoomId, Option<CachedSpaceHierarchySummary>>>,
+	pub roomid_spacehierarchy_cache: Mutex<Cache>,
 }
 
 struct Services {
 	state_accessor: Dep<rooms::state_accessor::Service>,
 	state_cache: Dep<rooms::state_cache::Service>,
 	state: Dep<rooms::state::Service>,
-	short: Dep<rooms::short::Service>,
 	event_handler: Dep<rooms::event_handler::Service>,
 	timeline: Dep<rooms::timeline::Service>,
 	sending: Dep<sending::Service>,
 }
 
+pub struct CachedSpaceHierarchySummary {
+	summary: SpaceHierarchyParentSummary,
+}
+
+#[allow(clippy::large_enum_variant)]
+pub enum SummaryAccessibility {
+	Accessible(SpaceHierarchyParentSummary),
+	Inaccessible,
+}
+
+/// Identifier used to check if rooms are accessible. None is used if you want
+/// to return the room, no matter if accessible or not
+pub enum Identifier<'a> {
+	UserId(&'a UserId),
+	ServerName(&'a ServerName),
+}
+
+type Cache = LruCache<OwnedRoomId, Option<CachedSpaceHierarchySummary>>;
+
 impl crate::Service for Service {
 	fn build(args: crate::Args<'_>) -> Result<Arc<Self>> {
 		let config = &args.server.config;
@@ -72,7 +82,6 @@ impl crate::Service for Service {
 					.depend::<rooms::state_accessor::Service>("rooms::state_accessor"),
 				state_cache: args.depend::<rooms::state_cache::Service>("rooms::state_cache"),
 				state: args.depend::<rooms::state::Service>("rooms::state"),
-				short: args.depend::<rooms::short::Service>("rooms::short"),
 				event_handler: args
 					.depend::<rooms::event_handler::Service>("rooms::event_handler"),
 				timeline: args.depend::<rooms::timeline::Service>("rooms::timeline"),
@@ -85,370 +94,407 @@ impl crate::Service for Service {
 	fn name(&self) -> &str { crate::service::make_name(std::module_path!()) }
 }
 
-impl Service {
-	/// Gets the summary of a space using solely local information
-	pub async fn get_summary_and_children_local(
-		&self,
-		current_room: &OwnedRoomId,
-		identifier: Identifier<'_>,
-	) -> Result<Option<SummaryAccessibility>> {
-		if let Some(cached) = self
-			.roomid_spacehierarchy_cache
-			.lock()
-			.await
-			.get_mut(&current_room.to_owned())
-			.as_ref()
-		{
-			return Ok(if let Some(cached) = cached {
+/// Gets the summary of a space using solely local information
+#[implement(Service)]
+pub async fn get_summary_and_children_local(
+	&self,
+	current_room: &RoomId,
+	identifier: &Identifier<'_>,
+) -> Result<Option<SummaryAccessibility>> {
+	match self
+		.roomid_spacehierarchy_cache
+		.lock()
+		.await
+		.get_mut(current_room)
+		.as_ref()
+	{
+		| None => (), // cache miss
+		| Some(None) => return Ok(None),
+		| Some(Some(cached)) =>
+			return Ok(Some(
 				if self
 					.is_accessible_child(
 						current_room,
 						&cached.summary.join_rule,
-						&identifier,
+						identifier,
 						&cached.summary.allowed_room_ids,
 					)
 					.await
 				{
-					Some(SummaryAccessibility::Accessible(Box::new(cached.summary.clone())))
+					SummaryAccessibility::Accessible(cached.summary.clone())
 				} else {
-					Some(SummaryAccessibility::Inaccessible)
-				}
-			} else {
-				None
-			});
-		}
+					SummaryAccessibility::Inaccessible
+				},
+			)),
+	};
 
-		if let Some(children_pdus) = self.get_stripped_space_child_events(current_room).await? {
-			let summary = self
-				.get_room_summary(current_room, children_pdus, &identifier)
-				.await;
-			if let Ok(summary) = summary {
-				self.roomid_spacehierarchy_cache.lock().await.insert(
-					current_room.clone(),
-					Some(CachedSpaceHierarchySummary { summary: summary.clone() }),
-				);
+	let children_pdus: Vec<_> = self
+		.get_stripped_space_child_events(current_room)
+		.collect()
+		.await;
 
-				Ok(Some(SummaryAccessibility::Accessible(Box::new(summary))))
-			} else {
-				Ok(None)
-			}
-		} else {
-			Ok(None)
-		}
-	}
+	let summary = self
+		.get_room_summary(current_room, children_pdus, identifier)
+		.boxed()
+		.await;
 
-	/// Gets the summary of a space using solely federation
-	#[tracing::instrument(level = "debug", skip(self))]
-	async fn get_summary_and_children_federation(
-		&self,
-		current_room: &OwnedRoomId,
-		suggested_only: bool,
-		user_id: &UserId,
-		via: &[OwnedServerName],
-	) -> Result<Option<SummaryAccessibility>> {
-		for server in via {
-			debug_info!("Asking {server} for /hierarchy");
-			let Ok(response) = self
-				.services
+	let Ok(summary) = summary else {
+		return Ok(None);
+	};
+
+	self.roomid_spacehierarchy_cache.lock().await.insert(
+		current_room.to_owned(),
+		Some(CachedSpaceHierarchySummary { summary: summary.clone() }),
+	);
+
+	Ok(Some(SummaryAccessibility::Accessible(summary)))
+}
+
+/// Gets the summary of a space using solely federation
+#[implement(Service)]
+#[tracing::instrument(level = "debug", skip(self))]
+async fn get_summary_and_children_federation(
+	&self,
+	current_room: &RoomId,
+	suggested_only: bool,
+	user_id: &UserId,
+	via: &[OwnedServerName],
+) -> Result<Option<SummaryAccessibility>> {
+	let request = federation::space::get_hierarchy::v1::Request {
+		room_id: current_room.to_owned(),
+		suggested_only,
+	};
+
+	let mut requests: FuturesUnordered<_> = via
+		.iter()
+		.map(|server| {
+			self.services
 				.sending
-				.send_federation_request(server, federation::space::get_hierarchy::v1::Request {
-					room_id: current_room.to_owned(),
-					suggested_only,
-				})
-				.await
-			else {
-				continue;
-			};
-
-			debug_info!("Got response from {server} for /hierarchy\n{response:?}");
-			let summary = response.room.clone();
-
-			self.roomid_spacehierarchy_cache.lock().await.insert(
-				current_room.clone(),
-				Some(CachedSpaceHierarchySummary { summary: summary.clone() }),
-			);
-
-			for child in response.children {
-				let mut guard = self.roomid_spacehierarchy_cache.lock().await;
-				if !guard.contains_key(current_room) {
-					guard.insert(
-						current_room.clone(),
-						Some(CachedSpaceHierarchySummary {
-							summary: {
-								let SpaceHierarchyChildSummary {
-									canonical_alias,
-									name,
-									num_joined_members,
-									room_id,
-									topic,
-									world_readable,
-									guest_can_join,
-									avatar_url,
-									join_rule,
-									room_type,
-									allowed_room_ids,
-								} = child;
-
-								SpaceHierarchyParentSummary {
-									canonical_alias,
-									name,
-									num_joined_members,
-									room_id: room_id.clone(),
-									topic,
-									world_readable,
-									guest_can_join,
-									avatar_url,
-									join_rule,
-									room_type,
-									children_state: self
-										.get_stripped_space_child_events(&room_id)
-										.await?
-										.unwrap(),
-									allowed_room_ids,
-								}
-							},
-						}),
-					);
-				}
-			}
-			if self
-				.is_accessible_child(
-					current_room,
-					&response.room.join_rule,
-					&Identifier::UserId(user_id),
-					&response.room.allowed_room_ids,
-				)
-				.await
-			{
-				return Ok(Some(SummaryAccessibility::Accessible(Box::new(summary.clone()))));
-			}
-
-			return Ok(Some(SummaryAccessibility::Inaccessible));
-		}
+				.send_federation_request(server, request.clone())
+		})
+		.collect();
 
+	let Some(Ok(response)) = requests.next().await else {
 		self.roomid_spacehierarchy_cache
 			.lock()
 			.await
-			.insert(current_room.clone(), None);
+			.insert(current_room.to_owned(), None);
 
-		Ok(None)
-	}
+		return Ok(None);
+	};
 
-	/// Gets the summary of a space using either local or remote (federation)
-	/// sources
-	pub async fn get_summary_and_children_client(
-		&self,
-		current_room: &OwnedRoomId,
-		suggested_only: bool,
-		user_id: &UserId,
-		via: &[OwnedServerName],
-	) -> Result<Option<SummaryAccessibility>> {
-		if let Ok(Some(response)) = self
-			.get_summary_and_children_local(current_room, Identifier::UserId(user_id))
-			.await
-		{
-			Ok(Some(response))
-		} else {
-			self.get_summary_and_children_federation(current_room, suggested_only, user_id, via)
-				.await
-		}
-	}
+	let summary = response.room;
+	self.roomid_spacehierarchy_cache.lock().await.insert(
+		current_room.to_owned(),
+		Some(CachedSpaceHierarchySummary { summary: summary.clone() }),
+	);
 
-	async fn get_room_summary(
-		&self,
-		current_room: &OwnedRoomId,
-		children_state: Vec<Raw<HierarchySpaceChildEvent>>,
-		identifier: &Identifier<'_>,
-	) -> Result<SpaceHierarchyParentSummary, Error> {
-		let room_id: &RoomId = current_room;
-
-		let join_rule = self
-			.services
-			.state_accessor
-			.room_state_get_content(room_id, &StateEventType::RoomJoinRules, "")
-			.await
-			.map_or(JoinRule::Invite, |c: RoomJoinRulesEventContent| c.join_rule);
-
-		let allowed_room_ids = self
-			.services
-			.state_accessor
-			.allowed_room_ids(join_rule.clone());
-
-		if !self
-			.is_accessible_child(
-				current_room,
-				&join_rule.clone().into(),
-				identifier,
-				&allowed_room_ids,
-			)
-			.await
-		{
-			debug_info!("User is not allowed to see room {room_id}");
-			// This error will be caught later
-			return Err(Error::BadRequest(
-				ErrorKind::forbidden(),
-				"User is not allowed to see the room",
-			));
-		}
-
-		Ok(SpaceHierarchyParentSummary {
-			canonical_alias: self
-				.services
-				.state_accessor
-				.get_canonical_alias(room_id)
-				.await
-				.ok(),
-			name: self.services.state_accessor.get_name(room_id).await.ok(),
-			num_joined_members: self
-				.services
-				.state_cache
-				.room_joined_count(room_id)
-				.await
-				.unwrap_or(0)
-				.try_into()
-				.expect("user count should not be that big"),
-			room_id: room_id.to_owned(),
-			topic: self
-				.services
-				.state_accessor
-				.get_room_topic(room_id)
-				.await
-				.ok(),
-			world_readable: self
-				.services
-				.state_accessor
-				.is_world_readable(room_id)
-				.await,
-			guest_can_join: self.services.state_accessor.guest_can_join(room_id).await,
-			avatar_url: self
-				.services
-				.state_accessor
-				.get_avatar(room_id)
-				.await
-				.into_option()
-				.unwrap_or_default()
-				.url,
-			join_rule: join_rule.into(),
-			room_type: self
-				.services
-				.state_accessor
-				.get_room_type(room_id)
-				.await
-				.ok(),
-			children_state,
-			allowed_room_ids,
+	response
+		.children
+		.into_iter()
+		.stream()
+		.then(|child| {
+			self.roomid_spacehierarchy_cache
+				.lock()
+				.map(|lock| (child, lock))
 		})
+		.ready_filter_map(|(child, mut cache)| {
+			(!cache.contains_key(current_room)).then_some((child, cache))
+		})
+		.for_each(|(child, cache)| self.cache_insert(cache, current_room, child))
+		.await;
+
+	let identifier = Identifier::UserId(user_id);
+	let is_accessible_child = self
+		.is_accessible_child(
+			current_room,
+			&summary.join_rule,
+			&identifier,
+			&summary.allowed_room_ids,
+		)
+		.await;
+
+	if is_accessible_child {
+		return Ok(Some(SummaryAccessibility::Accessible(summary)));
 	}
 
-	/// Simply returns the stripped m.space.child events of a room
-	async fn get_stripped_space_child_events(
-		&self,
-		room_id: &RoomId,
-	) -> Result<Option<Vec<Raw<HierarchySpaceChildEvent>>>, Error> {
-		let Ok(current_shortstatehash) =
-			self.services.state.get_room_shortstatehash(room_id).await
-		else {
-			return Ok(None);
-		};
-
-		let state: HashMap<_, Arc<_>> = self
-			.services
-			.state_accessor
-			.state_full_ids(current_shortstatehash)
-			.collect()
-			.await;
-
-		let mut children_pdus = Vec::with_capacity(state.len());
-		for (key, id) in state {
-			let (event_type, state_key) =
-				self.services.short.get_statekey_from_short(key).await?;
-
-			if event_type != StateEventType::SpaceChild {
-				continue;
-			}
-
-			let pdu =
-				self.services.timeline.get_pdu(&id).await.map_err(|e| {
-					err!(Database("Event {id:?} in space state not found: {e:?}"))
-				})?;
+	Ok(Some(SummaryAccessibility::Inaccessible))
+}
 
+/// Simply returns the stripped m.space.child events of a room
+#[implement(Service)]
+fn get_stripped_space_child_events<'a>(
+	&'a self,
+	room_id: &'a RoomId,
+) -> impl Stream<Item = Raw<HierarchySpaceChildEvent>> + 'a {
+	self.services
+		.state
+		.get_room_shortstatehash(room_id)
+		.map_ok(|current_shortstatehash| {
+			self.services
+				.state_accessor
+				.state_keys_with_ids(current_shortstatehash, &StateEventType::SpaceChild)
+		})
+		.map(Result::into_iter)
+		.map(IterStream::stream)
+		.map(StreamExt::flatten)
+		.flatten_stream()
+		.broad_filter_map(move |(state_key, event_id): (_, OwnedEventId)| async move {
+			self.services
+				.timeline
+				.get_pdu(&event_id)
+				.map_ok(move |pdu| (state_key, pdu))
+				.await
+				.ok()
+		})
+		.ready_filter_map(move |(state_key, pdu)| {
 			if let Ok(content) = pdu.get_content::<SpaceChildEventContent>() {
 				if content.via.is_empty() {
-					continue;
+					return None;
 				}
 			}
 
-			if OwnedRoomId::try_from(state_key).is_ok() {
-				children_pdus.push(pdu.to_stripped_spacechild_state_event());
+			if RoomId::parse(&state_key).is_ok() {
+				return Some(pdu.to_stripped_spacechild_state_event());
 			}
-		}
 
-		Ok(Some(children_pdus))
+			None
+		})
+}
+
+/// Gets the summary of a space using either local or remote (federation)
+/// sources
+#[implement(Service)]
+pub async fn get_summary_and_children_client(
+	&self,
+	current_room: &OwnedRoomId,
+	suggested_only: bool,
+	user_id: &UserId,
+	via: &[OwnedServerName],
+) -> Result<Option<SummaryAccessibility>> {
+	let identifier = Identifier::UserId(user_id);
+
+	if let Ok(Some(response)) = self
+		.get_summary_and_children_local(current_room, &identifier)
+		.await
+	{
+		return Ok(Some(response));
 	}
 
-	/// With the given identifier, checks if a room is accessable
-	async fn is_accessible_child(
-		&self,
-		current_room: &OwnedRoomId,
-		join_rule: &SpaceRoomJoinRule,
-		identifier: &Identifier<'_>,
-		allowed_room_ids: &Vec<OwnedRoomId>,
-	) -> bool {
-		match identifier {
-			| Identifier::ServerName(server_name) => {
-				// Checks if ACLs allow for the server to participate
-				if self
-					.services
-					.event_handler
-					.acl_check(server_name, current_room)
-					.await
-					.is_err()
-				{
-					return false;
-				}
-			},
-			| Identifier::UserId(user_id) => {
-				if self
-					.services
-					.state_cache
-					.is_joined(user_id, current_room)
-					.await || self
-					.services
-					.state_cache
-					.is_invited(user_id, current_room)
-					.await
-				{
-					return true;
-				}
-			},
+	self.get_summary_and_children_federation(current_room, suggested_only, user_id, via)
+		.await
+}
+
+#[implement(Service)]
+async fn get_room_summary(
+	&self,
+	room_id: &RoomId,
+	children_state: Vec<Raw<HierarchySpaceChildEvent>>,
+	identifier: &Identifier<'_>,
+) -> Result<SpaceHierarchyParentSummary, Error> {
+	let join_rule = self
+		.services
+		.state_accessor
+		.room_state_get_content(room_id, &StateEventType::RoomJoinRules, "")
+		.await
+		.map_or(JoinRule::Invite, |c: RoomJoinRulesEventContent| c.join_rule);
+
+	let allowed_room_ids = self
+		.services
+		.state_accessor
+		.allowed_room_ids(join_rule.clone());
+
+	let join_rule = join_rule.clone().into();
+	let is_accessible_child = self
+		.is_accessible_child(room_id, &join_rule, identifier, &allowed_room_ids)
+		.await;
+
+	if !is_accessible_child {
+		return Err!(Request(Forbidden("User is not allowed to see the room",)));
+	}
+
+	let name = self.services.state_accessor.get_name(room_id).ok();
+
+	let topic = self.services.state_accessor.get_room_topic(room_id).ok();
+
+	let room_type = self.services.state_accessor.get_room_type(room_id).ok();
+
+	let world_readable = self.services.state_accessor.is_world_readable(room_id);
+
+	let guest_can_join = self.services.state_accessor.guest_can_join(room_id);
+
+	let num_joined_members = self
+		.services
+		.state_cache
+		.room_joined_count(room_id)
+		.unwrap_or(0);
+
+	let canonical_alias = self
+		.services
+		.state_accessor
+		.get_canonical_alias(room_id)
+		.ok();
+
+	let avatar_url = self
+		.services
+		.state_accessor
+		.get_avatar(room_id)
+		.map(|res| res.into_option().unwrap_or_default().url);
+
+	let (
+		canonical_alias,
+		name,
+		num_joined_members,
+		topic,
+		world_readable,
+		guest_can_join,
+		avatar_url,
+		room_type,
+	) = futures::join!(
+		canonical_alias,
+		name,
+		num_joined_members,
+		topic,
+		world_readable,
+		guest_can_join,
+		avatar_url,
+		room_type
+	);
+
+	Ok(SpaceHierarchyParentSummary {
+		canonical_alias,
+		name,
+		topic,
+		world_readable,
+		guest_can_join,
+		avatar_url,
+		room_type,
+		children_state,
+		allowed_room_ids,
+		join_rule,
+		room_id: room_id.to_owned(),
+		num_joined_members: num_joined_members
+			.try_into()
+			.expect("user count should not be that big"),
+	})
+}
+
+/// With the given identifier, checks if a room is accessable
+#[implement(Service)]
+async fn is_accessible_child(
+	&self,
+	current_room: &RoomId,
+	join_rule: &SpaceRoomJoinRule,
+	identifier: &Identifier<'_>,
+	allowed_room_ids: &[OwnedRoomId],
+) -> bool {
+	if let Identifier::ServerName(server_name) = identifier {
+		// Checks if ACLs allow for the server to participate
+		if self
+			.services
+			.event_handler
+			.acl_check(server_name, current_room)
+			.await
+			.is_err()
+		{
+			return false;
 		}
-		match &join_rule {
-			| SpaceRoomJoinRule::Public
-			| SpaceRoomJoinRule::Knock
-			| SpaceRoomJoinRule::KnockRestricted => true,
-			| SpaceRoomJoinRule::Restricted => {
-				for room in allowed_room_ids {
+	}
+
+	if let Identifier::UserId(user_id) = identifier {
+		let is_joined = self.services.state_cache.is_joined(user_id, current_room);
+
+		let is_invited = self.services.state_cache.is_invited(user_id, current_room);
+
+		pin_mut!(is_joined, is_invited);
+		if is_joined.or(is_invited).await {
+			return true;
+		}
+	}
+
+	match join_rule {
+		| SpaceRoomJoinRule::Public
+		| SpaceRoomJoinRule::Knock
+		| SpaceRoomJoinRule::KnockRestricted => true,
+		| SpaceRoomJoinRule::Restricted =>
+			allowed_room_ids
+				.iter()
+				.stream()
+				.any(|room| async {
 					match identifier {
-						| Identifier::UserId(user) => {
-							if self.services.state_cache.is_joined(user, room).await {
-								return true;
-							}
-						},
-						| Identifier::ServerName(server) => {
-							if self.services.state_cache.server_in_room(server, room).await {
-								return true;
-							}
-						},
+						| Identifier::UserId(user) =>
+							self.services.state_cache.is_joined(user, room).await,
+						| Identifier::ServerName(server) =>
+							self.services.state_cache.server_in_room(server, room).await,
 					}
-				}
-				false
-			},
-			// Invite only, Private, or Custom join rule
-			| _ => false,
-		}
+				})
+				.await,
+
+		// Invite only, Private, or Custom join rule
+		| _ => false,
 	}
 }
 
+/// Returns the children of a SpaceHierarchyParentSummary, making use of the
+/// children_state field
+pub fn get_parent_children_via(
+	parent: &SpaceHierarchyParentSummary,
+	suggested_only: bool,
+) -> impl DoubleEndedIterator<Item = (OwnedRoomId, impl Iterator<Item = OwnedServerName>)> + Send + '_
+{
+	parent
+		.children_state
+		.iter()
+		.map(Raw::deserialize)
+		.filter_map(Result::ok)
+		.filter_map(move |ce| {
+			(!suggested_only || ce.content.suggested)
+				.then_some((ce.state_key, ce.content.via.into_iter()))
+		})
+}
+
+#[implement(Service)]
+async fn cache_insert(
+	&self,
+	mut cache: MutexGuard<'_, Cache>,
+	current_room: &RoomId,
+	child: SpaceHierarchyChildSummary,
+) {
+	let SpaceHierarchyChildSummary {
+		canonical_alias,
+		name,
+		num_joined_members,
+		room_id,
+		topic,
+		world_readable,
+		guest_can_join,
+		avatar_url,
+		join_rule,
+		room_type,
+		allowed_room_ids,
+	} = child;
+
+	let summary = SpaceHierarchyParentSummary {
+		canonical_alias,
+		name,
+		num_joined_members,
+		topic,
+		world_readable,
+		guest_can_join,
+		avatar_url,
+		join_rule,
+		room_type,
+		allowed_room_ids,
+		room_id: room_id.clone(),
+		children_state: self
+			.get_stripped_space_child_events(&room_id)
+			.collect()
+			.await,
+	};
+
+	cache.insert(current_room.to_owned(), Some(CachedSpaceHierarchySummary { summary }));
+}
+
 // Here because cannot implement `From` across ruma-federation-api and
 // ruma-client-api types
 impl From<CachedSpaceHierarchySummary> for SpaceHierarchyRoomsChunk {
@@ -517,25 +563,3 @@ pub fn summary_to_chunk(summary: SpaceHierarchyParentSummary) -> SpaceHierarchyR
 		children_state,
 	}
 }
-
-/// Returns the children of a SpaceHierarchyParentSummary, making use of the
-/// children_state field
-#[must_use]
-pub fn get_parent_children_via(
-	parent: &SpaceHierarchyParentSummary,
-	suggested_only: bool,
-) -> Vec<(OwnedRoomId, Vec<OwnedServerName>)> {
-	parent
-		.children_state
-		.iter()
-		.filter_map(|raw_ce| {
-			raw_ce.deserialize().map_or(None, |ce| {
-				if suggested_only && !ce.content.suggested {
-					None
-				} else {
-					Some((ce.state_key, ce.content.via))
-				}
-			})
-		})
-		.collect()
-}

src/service/rooms/spaces/tests.rs

@@ -1,5 +1,3 @@
-#![cfg(test)]
-
 use std::str::FromStr;
 
 use ruma::{
@@ -69,15 +67,22 @@ fn get_summary_children() {
 	}
 	.into();
 
-	assert_eq!(get_parent_children_via(&summary, false), vec![
-		(owned_room_id!("!foo:example.org"), vec![owned_server_name!("example.org")]),
-		(owned_room_id!("!bar:example.org"), vec![owned_server_name!("example.org")]),
-		(owned_room_id!("!baz:example.org"), vec![owned_server_name!("example.org")])
-	]);
-	assert_eq!(get_parent_children_via(&summary, true), vec![(
-		owned_room_id!("!bar:example.org"),
-		vec![owned_server_name!("example.org")]
-	)]);
+	assert_eq!(
+		get_parent_children_via(&summary, false)
+			.map(|(k, v)| (k, v.collect::<Vec<_>>()))
+			.collect::<Vec<_>>(),
+		vec![
+			(owned_room_id!("!foo:example.org"), vec![owned_server_name!("example.org")]),
+			(owned_room_id!("!bar:example.org"), vec![owned_server_name!("example.org")]),
+			(owned_room_id!("!baz:example.org"), vec![owned_server_name!("example.org")])
+		]
+	);
+	assert_eq!(
+		get_parent_children_via(&summary, true)
+			.map(|(k, v)| (k, v.collect::<Vec<_>>()))
+			.collect::<Vec<_>>(),
+		vec![(owned_room_id!("!bar:example.org"), vec![owned_server_name!("example.org")])]
+	);
 }
 
 #[test]