Bindings for the DM peer inbox id (#1197)

* add ffi bindings for the dm peer inbox id

* add a test for it

* fix up the test

* fix up lint

bindings_ffi/src/mls.rs

@@ -1416,6 +1416,10 @@ impl FfiConversation {
             inner: Arc::new(metadata),
         }))
     }
+
+    pub fn dm_peer_inbox_id(&self) -> Result<String, GenericError> {
+        self.inner.dm_inbox_id().map_err(Into::into)
+    }
 }
 
 #[uniffi::export]
@@ -3953,6 +3957,27 @@ mod tests {
         assert_eq!(bo_updated_consent, FfiConsentState::Allowed);
     }
 
+    #[tokio::test(flavor = "multi_thread", worker_threads = 5)]
+    async fn test_get_dm_peer_inbox_id() {
+        let alix = new_test_client().await;
+        let bo = new_test_client().await;
+
+        let alix_dm = alix
+            .conversations()
+            .create_dm(bo.account_address.clone())
+            .await
+            .unwrap();
+
+        let alix_dm_peer_inbox = alix_dm.dm_peer_inbox_id().unwrap();
+        assert_eq!(alix_dm_peer_inbox, bo.inbox_id());
+
+        bo.conversations().sync().await.unwrap();
+        let bo_dm = bo.conversation(alix_dm.id()).unwrap();
+
+        let bo_dm_peer_inbox = bo_dm.dm_peer_inbox_id().unwrap();
+        assert_eq!(bo_dm_peer_inbox, alix.inbox_id());
+    }
+
     #[tokio::test(flavor = "multi_thread", worker_threads = 5)]
     async fn test_set_and_get_member_consent() {
         let alix = new_test_client().await;

xmtp_mls/src/groups/mod.rs

@@ -1002,6 +1002,15 @@ impl<ScopedClient: ScopedGroupClient> MlsGroup<ScopedClient> {
             })
     }
 
+    /// Find the `inbox_id` of the group member who is the peer of this dm
+    pub fn dm_inbox_id(&self) -> Result<String, GroupError> {
+        let conn = self.context().store().conn()?;
+        let group = conn
+            .find_group(self.group_id.clone())?
+            .ok_or(GroupError::GroupNotFound)?;
+        group.dm_inbox_id.ok_or(GroupError::GroupNotFound)
+    }
+
     /// Find the `consent_state` of the group
     pub fn consent_state(&self) -> Result<ConsentState, GroupError> {
         let conn = self.context().store().conn()?;