feat(ffi): add support for MSC4036 thread subscriptions

Author: bnjbvr

bindings/matrix-sdk-ffi/CHANGELOG.md

@@ -8,6 +8,10 @@ All notable changes to this project will be documented in this file.
 
 ### Features:
 
+- Add experimental support for
+  [MSC4306](https://github.com/matrix-org/matrix-spec-proposals/pull/4306), with the
+  `Room::fetch_thread_subscription()` and `Room::toggle_thread_subscription()` methods.
+  ([#5442](https://github.com/matrix-org/matrix-rust-sdk/pull/5442))
 - [**breaking**] [`GalleryUploadParameters::reply`] and [`UploadParameters::reply`] have been both
   replaced with a new optional `in_reply_to` field, that's a string which will be parsed into an
   `OwnedEventId` when sending the event. The thread relationship will be automatically filled in,

bindings/matrix-sdk-ffi/src/room/mod.rs

@@ -1139,6 +1139,59 @@ impl Room {
 
         Ok(Arc::new(RoomPreview::new(AsyncRuntimeDropped::new(client), room_preview)))
     }
+
+    /// Toggle a MSC4306 subscription to a thread in this room, based on the
+    /// thread root event id.
+    ///
+    /// If `subscribed` is `true`, it will subscribe to the thread, with a
+    /// precision that the subscription was manually requested by the user
+    /// (i.e. not automatic).
+    ///
+    /// If the thread was already subscribed to (resp. unsubscribed from), while
+    /// trying to subscribe to it (resp. unsubscribe from it), it will do
+    /// nothing, i.e. subscribing (resp. unsubscribing) to a thread is an
+    /// idempotent operation.
+    pub async fn toggle_thread_subscription(
+        &self,
+        thread_root_event_id: String,
+        subscribed: bool,
+    ) -> Result<(), ClientError> {
+        let thread_root = EventId::parse(thread_root_event_id)?;
+        if subscribed {
+            // This is a manual subscription.
+            let automatic = false;
+            self.inner.subscribe_thread(thread_root, automatic).await?;
+        } else {
+            self.inner.unsubscribe_thread(thread_root).await?;
+        }
+        Ok(())
+    }
+
+    /// Return the current MSC4306 thread subscription for the given thread root
+    /// in this room.
+    ///
+    /// Returns `None` if the thread doesn't exist, or isn't subscribed to, or
+    /// the server can't handle MSC4306; otherwise, returns the thread
+    /// subscription status.
+    pub async fn fetch_thread_subscription(
+        &self,
+        thread_root_event_id: String,
+    ) -> Result<Option<ThreadSubscription>, ClientError> {
+        let thread_root = EventId::parse(thread_root_event_id)?;
+        Ok(self
+            .inner
+            .fetch_thread_subscription(thread_root)
+            .await?
+            .map(|sub| ThreadSubscription { automatic: sub.automatic }))
+    }
+}
+
+/// Status of a thread subscription (MSC4306).
+#[derive(uniffi::Record)]
+pub struct ThreadSubscription {
+    /// Whether the thread subscription happened automatically (e.g. after a
+    /// mention) or if it was manually requested by the user.
+    automatic: bool,
 }
 
 /// A listener for receiving new live location shares in a room.