refactor(sdk): Use a builder pattern to construct Timeline

`Timeline::with_fully_read_tracking` was public although all public
Timeline constructors enable it by default.
It is also meant to be called when constructing the timeline so
using a builder pattern makes sense.

Signed-off-by: Kévin Commaille <zecakeh@tedomum.fr>

crates/matrix-sdk/src/room/common.rs

@@ -270,7 +270,7 @@ impl Common {
     /// independent events.
     #[cfg(feature = "experimental-timeline")]
     pub async fn timeline(&self) -> Timeline {
-        Timeline::new(self).with_fully_read_tracking().await
+        Timeline::builder(self).track_fully_read().build().await
     }
 
     /// Fetch the event with the given `EventId` in this room.

crates/matrix-sdk/src/room/timeline/builder.rs

@@ -0,0 +1,162 @@
+// Copyright 2023 The Matrix.org Foundation C.I.C.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use std::sync::Arc;
+
+use matrix_sdk_base::{
+    deserialized_responses::{EncryptionInfo, SyncTimelineEvent},
+    locks::Mutex,
+};
+use ruma::events::fully_read::FullyReadEventContent;
+use tracing::error;
+
+use super::{
+    inner::TimelineInner,
+    to_device::{handle_forwarded_room_key_event, handle_room_key_event},
+    Timeline,
+};
+use crate::room;
+
+/// Builder that allows creating and configuring various parts of a
+/// [`Timeline`].
+#[must_use]
+#[derive(Debug)]
+pub(crate) struct TimelineBuilder {
+    room: room::Common,
+    prev_token: Option<String>,
+    events: Vec<SyncTimelineEvent>,
+    track_fully_read: bool,
+}
+
+impl TimelineBuilder {
+    pub(super) fn new(room: &room::Common) -> Self {
+        Self {
+            room: room.clone(),
+            prev_token: None,
+            events: Vec::default(),
+            track_fully_read: false,
+        }
+    }
+
+    /// Add initial events to the timeline.
+    #[cfg(feature = "experimental-sliding-sync")]
+    pub(crate) fn events(
+        mut self,
+        prev_token: Option<String>,
+        events: Vec<SyncTimelineEvent>,
+    ) -> Self {
+        self.prev_token = prev_token;
+        self.events = events;
+        self
+    }
+
+    /// Enable tracking of the fully-read marker on the timeline.
+    pub(crate) fn track_fully_read(mut self) -> Self {
+        self.track_fully_read = true;
+        self
+    }
+
+    /// Create a [`Timeline`] with the options set on this builder.
+    pub(crate) async fn build(self) -> Timeline {
+        let Self { room, prev_token, events, track_fully_read } = self;
+        let has_events = !events.is_empty();
+
+        let mut inner = TimelineInner::new(room);
+
+        if has_events {
+            inner.add_initial_events(events).await;
+        }
+
+        let inner = Arc::new(inner);
+        let room = inner.room();
+
+        let timeline_event_handle = room.add_event_handler({
+            let inner = inner.clone();
+            move |event, encryption_info: Option<EncryptionInfo>| {
+                let inner = inner.clone();
+                async move {
+                    inner.handle_live_event(event, encryption_info).await;
+                }
+            }
+        });
+
+        // Not using room.add_event_handler here because RoomKey events are
+        // to-device events that are not received in the context of a room.
+        #[cfg(feature = "e2e-encryption")]
+        let room_key_handle = room
+            .client
+            .add_event_handler(handle_room_key_event(inner.clone(), room.room_id().to_owned()));
+        #[cfg(feature = "e2e-encryption")]
+        let forwarded_room_key_handle = room.client.add_event_handler(
+            handle_forwarded_room_key_event(inner.clone(), room.room_id().to_owned()),
+        );
+
+        let mut event_handler_handles = vec![
+            timeline_event_handle,
+            #[cfg(feature = "e2e-encryption")]
+            room_key_handle,
+            #[cfg(feature = "e2e-encryption")]
+            forwarded_room_key_handle,
+        ];
+
+        if track_fully_read {
+            match room.account_data_static::<FullyReadEventContent>().await {
+                Ok(Some(fully_read)) => match fully_read.deserialize() {
+                    Ok(fully_read) => {
+                        inner.set_fully_read_event(fully_read.content.event_id).await;
+                    }
+                    Err(e) => {
+                        error!("Failed to deserialize fully-read account data: {e}");
+                    }
+                },
+                Err(e) => {
+                    error!("Failed to get fully-read account data from the store: {e}");
+                }
+                _ => {}
+            }
+
+            let fully_read_handle = room.add_event_handler({
+                let inner = inner.clone();
+                move |event| {
+                    let inner = inner.clone();
+                    async move {
+                        inner.handle_fully_read(event).await;
+                    }
+                }
+            });
+            event_handler_handles.push(fully_read_handle);
+        }
+
+        let timeline = Timeline {
+            inner,
+            start_token: Mutex::new(prev_token),
+            _end_token: Mutex::new(None),
+            event_handler_handles,
+        };
+
+        #[cfg(feature = "e2e-encryption")]
+        if has_events {
+            // The events we're injecting might be encrypted events, but we might
+            // have received the room key to decrypt them while nobody was listening to the
+            // `m.room_key` event, let's retry now.
+            //
+            // TODO: We could spawn a task here and put this into the background, though it
+            // might not be worth it depending on the number of events we injected.
+            // Some measuring needs to be done.
+            timeline.retry_decryption_for_all_events().await;
+        }
+
+        timeline
+    }
+}

crates/matrix-sdk/src/room/timeline/inner.rs

@@ -6,11 +6,9 @@ use std::{
 use async_trait::async_trait;
 use futures_signals::signal_vec::{MutableVec, MutableVecLockRef, SignalVec};
 use indexmap::IndexSet;
-#[cfg(any(test, feature = "experimental-sliding-sync"))]
-use matrix_sdk_base::deserialized_responses::SyncTimelineEvent;
 use matrix_sdk_base::{
     crypto::OlmMachine,
-    deserialized_responses::{EncryptionInfo, TimelineEvent},
+    deserialized_responses::{EncryptionInfo, SyncTimelineEvent, TimelineEvent},
     locks::Mutex,
 };
 use ruma::{
@@ -75,7 +73,6 @@ impl<P: ProfileProvider> TimelineInner<P> {
         self.items.signal_vec_cloned()
     }
 
-    #[cfg(any(test, feature = "experimental-sliding-sync"))]
     pub(super) async fn add_initial_events(&mut self, events: Vec<SyncTimelineEvent>) {
         if events.is_empty() {
             return;

crates/matrix-sdk/src/room/timeline/mod.rs

@@ -20,13 +20,9 @@ use std::sync::Arc;
 
 use futures_core::Stream;
 use futures_signals::signal_vec::{SignalVec, SignalVecExt, VecDiff};
-#[cfg(feature = "experimental-sliding-sync")]
-use matrix_sdk_base::deserialized_responses::SyncTimelineEvent;
-use matrix_sdk_base::{deserialized_responses::EncryptionInfo, locks::Mutex};
+use matrix_sdk_base::locks::Mutex;
 use ruma::{
-    assign,
-    events::{fully_read::FullyReadEventContent, AnyMessageLikeEventContent},
-    EventId, MilliSecondsSinceUnixEpoch, TransactionId,
+    assign, events::AnyMessageLikeEventContent, EventId, MilliSecondsSinceUnixEpoch, TransactionId,
 };
 use thiserror::Error;
 use tracing::{error, instrument, warn};
@@ -38,6 +34,7 @@ use crate::{
     Result,
 };
 
+mod builder;
 mod event_handler;
 mod event_item;
 mod inner;
@@ -48,6 +45,8 @@ mod tests;
 mod to_device;
 mod virtual_item;
 
+pub(crate) use self::builder::TimelineBuilder;
+use self::inner::{TimelineInner, TimelineInnerMetadata};
 pub use self::{
     event_item::{
         AnyOtherFullStateEventContent, BundledReactions, EncryptedMessage, EventSendState,
@@ -58,10 +57,6 @@ pub use self::{
     pagination::{PaginationOptions, PaginationOutcome},
     virtual_item::VirtualTimelineItem,
 };
-use self::{
-    inner::{TimelineInner, TimelineInnerMetadata},
-    to_device::{handle_forwarded_room_key_event, handle_room_key_event},
-};
 
 /// A high-level view into a regular¹ room's contents.
 ///
@@ -85,107 +80,14 @@ impl Drop for Timeline {
 }
 
 impl Timeline {
-    pub(super) fn new(room: &room::Common) -> Self {
-        Self::from_inner(Arc::new(TimelineInner::new(room.to_owned())), None)
-    }
-
-    #[cfg(feature = "experimental-sliding-sync")]
-    pub(crate) async fn with_events(
-        room: &room::Common,
-        prev_token: Option<String>,
-        events: Vec<SyncTimelineEvent>,
-    ) -> Self {
-        let mut inner = TimelineInner::new(room.to_owned());
-        inner.add_initial_events(events).await;
-
-        let timeline = Self::from_inner(Arc::new(inner), prev_token);
-
-        // The events we're injecting might be encrypted events, but we might
-        // have received the room key to decrypt them while nobody was listening to the
-        // `m.room_key` event, let's retry now.
-        //
-        // TODO: We could spawn a task here and put this into the background, though it
-        // might not be worth it depending on the number of events we injected.
-        // Some measuring needs to be done.
-        #[cfg(feature = "e2e-encryption")]
-        timeline.retry_decryption_for_all_events().await;
-
-        timeline
-    }
-
-    fn from_inner(inner: Arc<TimelineInner>, prev_token: Option<String>) -> Timeline {
-        let room = inner.room();
-
-        let timeline_event_handle = room.add_event_handler({
-            let inner = inner.clone();
-            move |event, encryption_info: Option<EncryptionInfo>| {
-                let inner = inner.clone();
-                async move {
-                    inner.handle_live_event(event, encryption_info).await;
-                }
-            }
-        });
-
-        // Not using room.add_event_handler here because RoomKey events are
-        // to-device events that are not received in the context of a room.
-        #[cfg(feature = "e2e-encryption")]
-        let room_key_handle = room
-            .client
-            .add_event_handler(handle_room_key_event(inner.clone(), room.room_id().to_owned()));
-        #[cfg(feature = "e2e-encryption")]
-        let forwarded_room_key_handle = room.client.add_event_handler(
-            handle_forwarded_room_key_event(inner.clone(), room.room_id().to_owned()),
-        );
-
-        let event_handler_handles = vec![
-            timeline_event_handle,
-            #[cfg(feature = "e2e-encryption")]
-            room_key_handle,
-            #[cfg(feature = "e2e-encryption")]
-            forwarded_room_key_handle,
-        ];
-
-        Timeline {
-            inner,
-            start_token: Mutex::new(prev_token),
-            _end_token: Mutex::new(None),
-            event_handler_handles,
-        }
+    pub(crate) fn builder(room: &room::Common) -> TimelineBuilder {
+        TimelineBuilder::new(room)
     }
 
     fn room(&self) -> &room::Common {
         self.inner.room()
     }
 
-    /// Enable tracking of the fully-read marker on this `Timeline`.
-    pub async fn with_fully_read_tracking(mut self) -> Self {
-        match self.room().account_data_static::<FullyReadEventContent>().await {
-            Ok(Some(fully_read)) => match fully_read.deserialize() {
-                Ok(fully_read) => {
-                    self.inner.set_fully_read_event(fully_read.content.event_id).await;
-                }
-                Err(e) => {
-                    error!("Failed to deserialize fully-read account data: {e}");
-                }
-            },
-            Err(e) => {
-                error!("Failed to get fully-read account data from the store: {e}");
-            }
-            _ => {}
-        }
-
-        let inner = self.inner.clone();
-        let fully_read_handle = self.room().add_event_handler(move |event| {
-            let inner = inner.clone();
-            async move {
-                inner.handle_fully_read(event).await;
-            }
-        });
-        self.event_handler_handles.push(fully_read_handle);
-
-        self
-    }
-
     /// Clear all timeline items, and reset pagination parameters.
     #[cfg(feature = "experimental-sliding-sync")]
     pub async fn clear(&self) {
@@ -311,7 +213,7 @@ impl Timeline {
             .await;
     }
 
-    #[cfg(all(feature = "experimental-sliding-sync", feature = "e2e-encryption"))]
+    #[cfg(feature = "e2e-encryption")]
     async fn retry_decryption_for_all_events(&self) {
         self.inner
             .retry_event_decryption(

crates/matrix-sdk/src/sliding_sync.rs

@@ -49,7 +49,7 @@ use tracing::{debug, error, instrument, trace, warn};
 use url::Url;
 
 #[cfg(feature = "experimental-timeline")]
-use crate::room::timeline::{EventTimelineItem, Timeline};
+use crate::room::timeline::{EventTimelineItem, Timeline, TimelineBuilder};
 use crate::{config::RequestConfig, Client, Result};
 
 /// Internal representation of errors in Sliding Sync
@@ -241,16 +241,17 @@ impl SlidingSyncRoom {
     /// `Timeline` of this room
     #[cfg(feature = "experimental-timeline")]
     pub async fn timeline(&self) -> Option<Timeline> {
-        Some(self.timeline_no_fully_read_tracking().await?.with_fully_read_tracking().await)
+        Some(self.timeline_builder()?.track_fully_read().build().await)
     }
 
-    async fn timeline_no_fully_read_tracking(&self) -> Option<Timeline> {
+    #[cfg(feature = "experimental-timeline")]
+    fn timeline_builder(&self) -> Option<TimelineBuilder> {
         if let Some(room) = self.client.get_room(&self.room_id) {
             let current_timeline = self.timeline.lock_ref().to_vec();
             let prev_batch = self.prev_batch.lock_ref().clone();
-            Some(Timeline::with_events(&room, prev_batch, current_timeline).await)
+            Some(Timeline::builder(&room).events(prev_batch, current_timeline))
         } else if let Some(invited_room) = self.client.get_invited_room(&self.room_id) {
-            Some(Timeline::with_events(&invited_room, None, vec![]).await)
+            Some(Timeline::builder(&invited_room).events(None, vec![]))
         } else {
             error!(
                 room_id = ?self.room_id,
@@ -266,7 +267,7 @@ impl SlidingSyncRoom {
     /// this `SlidingSyncRoom`.
     #[cfg(feature = "experimental-timeline")]
     pub async fn latest_event(&self) -> Option<EventTimelineItem> {
-        self.timeline_no_fully_read_tracking().await?.latest_event()
+        self.timeline_builder()?.build().await.latest_event()
     }
 
     /// This rooms name as calculated by the server, if any