From cead90253ea43a921e50a71091ea3a33735ff8d0 Mon Sep 17 00:00:00 2001
From: Ivan Enderlin <ivan@mnt.io>
Date: Tue, 28 Apr 2026 11:04:06 +0200
Subject: [PATCH] feat(sdk): Add `LinkedChunk::first_chunk`.

This patch adds `LinkedChunk::first_chunk`, and exposes it to
`EventLinkedChunk` to replace the use of 2 iterators in `RoomPagination`
and `ThreadPagination`, and to remove 2 `unwrap`s.
---
 crates/matrix-sdk-common/src/linked_chunk/mod.rs             | 5 +++++
 .../matrix-sdk/src/event_cache/caches/event_linked_chunk.rs  | 5 +++++
 crates/matrix-sdk/src/event_cache/caches/room/pagination.rs  | 3 +--
 .../matrix-sdk/src/event_cache/caches/thread/pagination.rs   | 3 +--
 4 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/crates/matrix-sdk-common/src/linked_chunk/mod.rs b/crates/matrix-sdk-common/src/linked_chunk/mod.rs
index 31347ba66..b6115b327 100644
--- a/crates/matrix-sdk-common/src/linked_chunk/mod.rs
+++ b/crates/matrix-sdk-common/src/linked_chunk/mod.rs
@@ -1110,6 +1110,11 @@ impl<const CAP: usize, Item, Gap> LinkedChunk<CAP, Item, Gap> {
             .skip(position.index()))
     }
 
+    /// Return the first chunk.
+    pub fn first_chunk(&self) -> &Chunk<CAP, Item, Gap> {
+        self.links.first_chunk()
+    }
+
     /// Get a mutable reference to the `LinkedChunk` updates, aka
     /// [`ObservableUpdates`].
     ///
diff --git a/crates/matrix-sdk/src/event_cache/caches/event_linked_chunk.rs b/crates/matrix-sdk/src/event_cache/caches/event_linked_chunk.rs
index f4265dd8d..edfe17d4d 100644
--- a/crates/matrix-sdk/src/event_cache/caches/event_linked_chunk.rs
+++ b/crates/matrix-sdk/src/event_cache/caches/event_linked_chunk.rs
@@ -177,6 +177,11 @@ impl EventLinkedChunk {
         self.chunks.chunk_identifier(predicate)
     }
 
+    /// Return the first chunk.
+    pub fn first_chunk(&self) -> &Chunk<DEFAULT_CHUNK_CAPACITY, Event, Gap> {
+        self.chunks.first_chunk()
+    }
+
     /// Iterate over the chunks, forward.
     ///
     /// The oldest chunk comes first.
diff --git a/crates/matrix-sdk/src/event_cache/caches/room/pagination.rs b/crates/matrix-sdk/src/event_cache/caches/room/pagination.rs
index b99fe6c7d..66b1089bc 100644
--- a/crates/matrix-sdk/src/event_cache/caches/room/pagination.rs
+++ b/crates/matrix-sdk/src/event_cache/caches/room/pagination.rs
@@ -170,8 +170,7 @@ impl PaginatedCache for Arc<RoomEventCacheInner> {
             });
         }
 
-        let prev_first_chunk =
-            state.room_linked_chunk().chunks().next().expect("a linked chunk is never empty");
+        let prev_first_chunk = state.room_linked_chunk().first_chunk();
 
         // The first chunk is not a gap, we can load its previous chunk.
         let linked_chunk_id = LinkedChunkId::Room(&state.state.room_id);
diff --git a/crates/matrix-sdk/src/event_cache/caches/thread/pagination.rs b/crates/matrix-sdk/src/event_cache/caches/thread/pagination.rs
index e8223db4e..7f28e81f1 100644
--- a/crates/matrix-sdk/src/event_cache/caches/thread/pagination.rs
+++ b/crates/matrix-sdk/src/event_cache/caches/thread/pagination.rs
@@ -112,8 +112,7 @@ impl PaginatedCache for ThreadEventCacheWrapper {
             });
         }
 
-        let prev_first_chunk =
-            state.thread_linked_chunk().chunks().next().expect("a linked chunk is never empty");
+        let prev_first_chunk = state.thread_linked_chunk().first_chunk();
 
         // The first chunk is not a gap, we can load its previous chunk.
         let linked_chunk_id = LinkedChunkId::Thread(&state.room_id, &state.thread_id);