From 6b8d6956a3e8a3fcb7ac410a0443b1ed19ab99cc Mon Sep 17 00:00:00 2001
From: Jason Volk <jason@zemos.net>
Date: Sun, 2 Nov 2025 06:32:52 +0000
Subject: [PATCH] Fix timeline events order in /initialSync.

Implement acccount_data for response.

Ensure consistency of revealed events.

Signed-off-by: Jason Volk <jason@zemos.net>
---
 src/api/client/room/initial_sync.rs | 89 +++++++++++++++++------------
 1 file changed, 53 insertions(+), 36 deletions(-)

diff --git a/src/api/client/room/initial_sync.rs b/src/api/client/room/initial_sync.rs
index 58611969..e0c6c9c6 100644
--- a/src/api/client/room/initial_sync.rs
+++ b/src/api/client/room/initial_sync.rs
@@ -1,15 +1,20 @@
 use axum::extract::State;
-use futures::{FutureExt, TryStreamExt, future::try_join4};
-use ruma::api::client::room::initial_sync::v3::{PaginationChunk, Request, Response};
+use futures::{FutureExt, StreamExt, TryFutureExt, TryStreamExt, future::try_join5};
+use ruma::{
+	api::client::room::initial_sync::v3::{PaginationChunk, Request, Response},
+	events::AnyRawAccountDataEvent,
+};
 use tuwunel_core::{
-	Err, Event, Result, at,
-	utils::{BoolExt, stream::TryTools},
+	Err, Event, Result, at, extract_variant,
+	matrix::PduCount,
+	utils::stream::{ReadyExt, TryTools},
 };
 
 use crate::Ruma;
 
-const LIMIT_MAX: usize = 100;
+const LIMIT_MAX: usize = 50;
 
+/// GET `/_matrix/client/v3/rooms/{roomId}/initialSync`
 pub(crate) async fn room_initial_sync_route(
 	State(services): State<crate::State>,
 	body: Ruma<Request>,
@@ -24,13 +29,15 @@ pub(crate) async fn room_initial_sync_route(
 		return Err!(Request(Forbidden("No room preview available.")));
 	}
 
+	let next_batch = services.globals.current_count();
+
+	let visibility = services.directory.visibility(room_id).map(Ok);
+
 	let membership = services
 		.state_cache
 		.user_membership(body.sender_user(), room_id)
 		.map(Ok);
 
-	let visibility = services.directory.visibility(room_id).map(Ok);
-
 	let state = services
 		.state_accessor
 		.room_state_full_pdus(room_id)
@@ -40,42 +47,52 @@ pub(crate) async fn room_initial_sync_route(
 	let limit = LIMIT_MAX;
 	let events = services
 		.timeline
-		.pdus_rev(None, room_id, None)
+		.pdus_rev(None, room_id, Some(PduCount::Normal(next_batch).saturating_add(1)))
 		.try_take(limit)
-		.try_collect::<Vec<_>>();
+		.try_collect()
+		.map_ok(|mut vec: Vec<_>| {
+			vec.reverse();
+			vec
+		});
 
-	let (membership, visibility, state, events) =
-		try_join4(membership, visibility, state, events)
+	let account_data = services
+		.account_data
+		.changes_since(Some(room_id), body.sender_user(), 0, Some(next_batch))
+		.ready_filter_map(|e| extract_variant!(e, AnyRawAccountDataEvent::Room))
+		.collect::<Vec<_>>()
+		.map(Ok);
+
+	let (membership, visibility, state, events, account_data) =
+		try_join5(membership, visibility, state, events, account_data)
 			.boxed()
 			.await?;
 
-	let messages = PaginationChunk {
-		start: events
-			.last()
-			.map(at!(0))
-			.as_ref()
-			.map(ToString::to_string),
-
-		end: events
-			.first()
-			.map(at!(0))
-			.as_ref()
-			.map(ToString::to_string)
-			.unwrap_or_default(),
-
-		chunk: events
-			.into_iter()
-			.map(at!(1))
-			.map(Event::into_format)
-			.collect(),
-	};
-
 	Ok(Response {
 		room_id: room_id.to_owned(),
-		account_data: None,
-		state: state.into(),
-		messages: messages.chunk.is_empty().or_some(messages),
-		visibility: visibility.into(),
 		membership,
+		visibility: visibility.into(),
+		account_data: Some(account_data),
+		state: state.into(),
+		messages: PaginationChunk {
+			start: events
+				.first()
+				.map(at!(0))
+				.as_ref()
+				.map(ToString::to_string),
+
+			end: events
+				.last()
+				.map(at!(0))
+				.as_ref()
+				.map(ToString::to_string)
+				.unwrap_or_default(),
+
+			chunk: events
+				.into_iter()
+				.map(at!(1))
+				.map(Event::into_format)
+				.collect(),
+		}
+		.into(),
 	})
 }