split s2s into units

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

src/api/server/backfill.rs

@@ -0,0 +1,69 @@
+use ruma::{
+	api::{client::error::ErrorKind, federation::backfill::get_backfill},
+	uint, user_id, MilliSecondsSinceUnixEpoch,
+};
+
+use crate::{services, Error, PduEvent, Result, Ruma};
+
+/// # `GET /_matrix/federation/v1/backfill/<room_id>`
+///
+/// Retrieves events from before the sender joined the room, if the room's
+/// history visibility allows.
+pub(crate) async fn get_backfill_route(body: Ruma<get_backfill::v1::Request>) -> Result<get_backfill::v1::Response> {
+	let origin = body.origin.as_ref().expect("server is authenticated");
+
+	if !services()
+		.rooms
+		.state_cache
+		.server_in_room(origin, &body.room_id)?
+	{
+		return Err(Error::BadRequest(ErrorKind::forbidden(), "Server is not in room."));
+	}
+
+	services()
+		.rooms
+		.event_handler
+		.acl_check(origin, &body.room_id)?;
+
+	let until = body
+		.v
+		.iter()
+		.map(|event_id| services().rooms.timeline.get_pdu_count(event_id))
+		.filter_map(|r| r.ok().flatten())
+		.max()
+		.ok_or_else(|| Error::BadRequest(ErrorKind::InvalidParam, "Event not found."))?;
+
+	let limit = body
+		.limit
+		.min(uint!(100))
+		.try_into()
+		.expect("UInt could not be converted to usize");
+
+	let all_events = services()
+		.rooms
+		.timeline
+		.pdus_until(user_id!("@doesntmatter:conduit.rs"), &body.room_id, until)?
+		.take(limit);
+
+	let events = all_events
+		.filter_map(Result::ok)
+		.filter(|(_, e)| {
+			matches!(
+				services()
+					.rooms
+					.state_accessor
+					.server_can_see_event(origin, &e.room_id, &e.event_id,),
+				Ok(true),
+			)
+		})
+		.map(|(_, pdu)| services().rooms.timeline.get_pdu_json(&pdu.event_id))
+		.filter_map(|r| r.ok().flatten())
+		.map(PduEvent::convert_to_outgoing_federation_event)
+		.collect();
+
+	Ok(get_backfill::v1::Response {
+		origin: services().globals.server_name().to_owned(),
+		origin_server_ts: MilliSecondsSinceUnixEpoch::now(),
+		pdus: events,
+	})
+}