From 9102a9c84124d0b6bd2fbd4910df38cb33ff6dc3 Mon Sep 17 00:00:00 2001
From: Ivan Enderlin <ivan@mnt.io>
Date: Mon, 18 Mar 2024 14:30:58 +0100
Subject: [PATCH] feat(sdk):
 `RoomEventCachecacherInner::oldest_backpagination_token` uses `RoomEvents`.

---
 crates/matrix-sdk/src/event_cache/mod.rs   | 22 ++++++++++++----------
 crates/matrix-sdk/src/event_cache/store.rs |  7 +++++++
 2 files changed, 19 insertions(+), 10 deletions(-)

diff --git a/crates/matrix-sdk/src/event_cache/mod.rs b/crates/matrix-sdk/src/event_cache/mod.rs
index d1162c1e6..23e44baaf 100644
--- a/crates/matrix-sdk/src/event_cache/mod.rs
+++ b/crates/matrix-sdk/src/event_cache/mod.rs
@@ -62,7 +62,7 @@ use ruma::{
 use tokio::{
     sync::{
         broadcast::{error::RecvError, Receiver, Sender},
-        Mutex, Notify, RwLock,
+        Mutex, Notify, RwLock, RwLockReadGuard,
     },
     time::timeout,
 };
@@ -307,7 +307,7 @@ impl EventCacheInner {
     async fn handle_room_updates(&self, updates: RoomUpdates) -> Result<()> {
         // First, take the lock that indicates we're processing updates, to avoid
         // handling multiple updates concurrently.
-        let lock = self.multiple_room_updates_lock.lock().await;
+        let _lock = self.multiple_room_updates_lock.lock().await;
 
         // Left rooms.
         for (room_id, left_room_update) in updates.leave {
@@ -704,16 +704,19 @@ impl RoomEventCacheInner {
         max_wait: Option<Duration>,
     ) -> Result<Option<PaginationToken>> {
         // Optimistically try to return the backpagination token immediately.
-        todo!();
-        /*
-        if let Some(token) =
-            self.store.lock().await.oldest_backpagination_token(self.room.room_id()).await?
-        {
+        fn get_oldest(room_events: RwLockReadGuard<RoomEvents>) -> Option<PaginationToken> {
+            room_events.chunks().find_map(|chunk| match chunk.content() {
+                ChunkContent::Gap(gap) => Some(gap.prev_token.clone()),
+                ChunkContent::Items(..) => None,
+            })
+        }
+
+        if let Some(token) = get_oldest(self.events.read().await) {
             return Ok(Some(token));
         }
 
         let Some(max_wait) = max_wait else {
-            // We had no token and no time to wait, so... no tokens.
+            // We had no token and no time to wait, so… no tokens.
             return Ok(None);
         };
 
@@ -721,8 +724,7 @@ impl RoomEventCacheInner {
         // Timeouts are fine, per this function's contract.
         let _ = timeout(max_wait, self.pagination_token_notifier.notified()).await;
 
-        self.store.lock().await.oldest_backpagination_token(self.room.room_id()).await
-        */
+        Ok(get_oldest(self.events.read().await))
     }
 }
 
diff --git a/crates/matrix-sdk/src/event_cache/store.rs b/crates/matrix-sdk/src/event_cache/store.rs
index 998b2b655..c0fe3b08e 100644
--- a/crates/matrix-sdk/src/event_cache/store.rs
+++ b/crates/matrix-sdk/src/event_cache/store.rs
@@ -324,6 +324,13 @@ impl RoomEvents {
         self.chunks.rchunks()
     }
 
+    /// Iterate over the chunks, forward.
+    ///
+    /// The oldest chunk comes first.
+    pub fn chunks(&self) -> LinkedChunkIter<'_, SyncTimelineEvent, Gap, DEFAULT_CHUNK_CAPACITY> {
+        self.chunks.chunks()
+    }
+
     /// Iterate over the chunks, starting from `identifier`, backward.
     pub fn rchunks_from(
         &self,