feat(event cache): automatically request paginations when no receipt has been found when computing unread counts

crates/matrix-sdk/src/event_cache/caches/read_receipts.rs

@@ -108,9 +108,10 @@ use ruma::{
     },
     serde::Raw,
 };
+use tokio::sync::mpsc::Sender;
 use tracing::{debug, instrument, trace, warn};
 
-use crate::event_cache::caches::event_linked_chunk::EventLinkedChunk;
+use crate::event_cache::{caches::event_linked_chunk::EventLinkedChunk, tasks::BackgroundRequest};
 
 trait RoomReadReceiptsExt {
     /// Update the [`RoomReadReceipts`] unread counts according to the new
@@ -363,6 +364,7 @@ pub(crate) fn compute_unread_counts(
     linked_chunk: &EventLinkedChunk,
     read_receipts: &mut RoomReadReceipts,
     with_threading_support: bool,
+    background_request_sender: Option<&Sender<BackgroundRequest>>,
 ) {
     debug!(?read_receipts, "Starting");
 
@@ -375,6 +377,18 @@ pub(crate) fn compute_unread_counts(
         with_threading_support,
     );
 
+    if select_best_receipt_result.request_pagination {
+        trace!("Requesting pagination to find a better receipt");
+        // Note: we use `try_send` here to keep the method sync, as computing the
+        // perfect receipt is best effort.
+        if let Some(sender) = background_request_sender
+            && let Err(err) = sender
+                .try_send(BackgroundRequest::PaginateRoomBackwards { room_id: room_id.to_owned() })
+        {
+            warn!(%err, "Failed to request pagination to find a better receipt");
+        }
+    }
+
     if let Some(event_id) = select_best_receipt_result.receipt {
         // We've found the id of an event to which the receipt attaches. The associated
         // event may either come from the new batch of events associated to

crates/matrix-sdk/src/event_cache/caches/room/state.rs

@@ -1046,9 +1046,8 @@ impl<'a> RoomEventCacheStateLockWriteGuard<'a> {
             return Ok(());
         };
 
-        let state = &mut *self.state;
-        let user_id = &state.own_user_id;
-        let room_id = &state.room_id;
+        let user_id = &self.state.own_user_id;
+        let room_id = &self.state.room_id;
 
         let prev_read_receipts = room.read_receipts().clone();
         let mut read_receipts = prev_read_receipts.clone();
@@ -1057,9 +1056,10 @@ impl<'a> RoomEventCacheStateLockWriteGuard<'a> {
             user_id,
             room_id,
             receipt_event,
-            &state.room_linked_chunk,
+            &self.state.room_linked_chunk,
             &mut read_receipts,
-            state.enabled_thread_support,
+            self.state.enabled_thread_support,
+            self.state.background_request_sender.as_ref(),
         );
 
         if prev_read_receipts != read_receipts {