Split sliding-sync extensions into units.

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

src/api/client/sync/v5/to_device.rs

@@ -0,0 +1,34 @@
+use futures::StreamExt;
+use ruma::api::client::sync::sync_events::v5::response;
+use tuwunel_core::{self, Result};
+use tuwunel_service::Services;
+
+use super::SyncInfo;
+
+#[tracing::instrument(level = "trace", skip_all, fields(globalsince, next_batch))]
+pub(super) async fn collect(
+	services: &Services,
+	(sender_user, sender_device, globalsince, _request): SyncInfo<'_>,
+	next_batch: u64,
+) -> Result<Option<response::ToDevice>> {
+	services
+		.users
+		.remove_to_device_events(sender_user, sender_device, globalsince)
+		.await;
+
+	let events: Vec<_> = services
+		.users
+		.get_to_device_events(sender_user, sender_device, None, Some(next_batch))
+		.collect()
+		.await;
+
+	let to_device = events
+		.is_empty()
+		.eq(&false)
+		.then(|| response::ToDevice {
+			next_batch: next_batch.to_string(),
+			events,
+		});
+
+	Ok(to_device)
+}