client_api: allow player to connect before match has started

planetwars-server/src/modules/client_api.rs

@@ -33,10 +33,26 @@ pub struct ClientApiServer {
     router: PlayerRouter,
 }
 
+type ClientMessages = Streaming<pb::PlayerApiClientMessage>;
+type ServerMessages = mpsc::UnboundedReceiver<Result<pb::PlayerApiServerMessage, Status>>;
+
+enum PlayerConnectionState {
+    Reserved,
+    ClientConnected {
+        tx: oneshot::Sender<ServerMessages>,
+        client_messages: ClientMessages,
+    },
+    ServerConnected {
+        tx: oneshot::Sender<ClientMessages>,
+        server_messages: ServerMessages,
+    },
+    // In connected state, the connection is removed from the PlayerRouter
+}
+
 /// Routes players to their handler
 #[derive(Clone)]
 struct PlayerRouter {
-    routing_table: Arc<Mutex<HashMap<String, SyncThingData>>>,
+    routing_table: Arc<Mutex<HashMap<String, PlayerConnectionState>>>,
 }
 
 impl PlayerRouter {
@@ -55,12 +71,12 @@ impl Default for PlayerRouter {
 
 // TODO: implement a way to expire entries
 impl PlayerRouter {
-    fn put(&self, player_key: String, entry: SyncThingData) {
+    fn put(&self, player_key: String, entry: PlayerConnectionState) {
         let mut routing_table = self.routing_table.lock().unwrap();
         routing_table.insert(player_key, entry);
     }
 
-    fn take(&self, player_key: &str) -> Option<SyncThingData> {
+    fn take(&self, player_key: &str) -> Option<PlayerConnectionState> {
         // TODO: this design does not allow for reconnects. Is this desired?
         let mut routing_table = self.routing_table.lock().unwrap();
         routing_table.remove(player_key)
@@ -81,21 +97,62 @@ impl pb::client_api_service_server::ClientApiService for ClientApiServer {
             .get("player_key")
             .ok_or_else(|| Status::unauthenticated("no player_key provided"))?;
 
-        let player_key_str = player_key
+        let player_key_string = player_key
             .to_str()
-            .map_err(|_| Status::invalid_argument("unreadable string"))?;
+            .map_err(|_| Status::invalid_argument("unreadable string"))?
+            .to_string();
 
-        let sync_data = self
-            .router
-            .take(player_key_str)
+        let client_messages = req.into_inner();
+
+        enum ConnState {
+            Connected {
+                server_messages: ServerMessages,
+            },
+            Awaiting {
+                rx: oneshot::Receiver<ServerMessages>,
+            },
+        }
+
+        let conn_state = {
+            // during this block, a lack is held on the routing table
+
+            let mut routing_table = self.router.routing_table.lock().unwrap();
+            let connection_state = routing_table
+                .remove(&player_key_string)
                 .ok_or_else(|| Status::not_found("player_key not found"))?;
+            match connection_state {
+                PlayerConnectionState::Reserved => {
+                    let (tx, rx) = oneshot::channel();
 
-        let stream = req.into_inner();
+                    routing_table.insert(
+                        player_key_string,
+                        PlayerConnectionState::ClientConnected {
+                            tx,
+                            client_messages,
+                        },
+                    );
 
-        sync_data.tx.send(stream).unwrap();
-        Ok(Response::new(UnboundedReceiverStream::new(
-            sync_data.server_messages,
-        )))
+                    ConnState::Awaiting { rx }
+                }
+                PlayerConnectionState::ServerConnected {
+                    tx,
+                    server_messages,
+                } => {
+                    tx.send(client_messages).unwrap();
+                    ConnState::Connected { server_messages }
+                }
+                PlayerConnectionState::ClientConnected { .. } => panic!("player already connected"),
+            }
+        };
+
+        let server_messages = match conn_state {
+            ConnState::Connected { server_messages } => server_messages,
+            ConnState::Awaiting { rx } => rx
+                .await
+                .map_err(|_| Status::internal("failed to connect player to game"))?,
+        };
+
+        Ok(Response::new(UnboundedReceiverStream::new(server_messages)))
     }
 
     async fn create_match(
@@ -119,6 +176,9 @@ impl pb::client_api_service_server::ClientApiService for ClientApiServer {
             .map_err(|_| Status::not_found("map not found"))?;
 
         let player_key = gen_alphanumeric(32);
+        // ensure that the player key is registered in the router when we send a response
+        self.router
+            .put(player_key.clone(), PlayerConnectionState::Reserved);
 
         let remote_bot_spec = Box::new(RemoteBotSpec {
             player_key: player_key.clone(),
@@ -155,12 +215,6 @@ impl pb::client_api_service_server::ClientApiService for ClientApiServer {
     }
 }
 
-// TODO: please rename me
-struct SyncThingData {
-    tx: oneshot::Sender<Streaming<pb::PlayerApiClientMessage>>,
-    server_messages: mpsc::UnboundedReceiver<Result<pb::PlayerApiServerMessage, Status>>,
-}
-
 struct RemoteBotSpec {
     player_key: String,
     router: PlayerRouter,
@@ -174,31 +228,70 @@ impl runner::BotSpec for RemoteBotSpec {
         event_bus: Arc<Mutex<EventBus>>,
         _match_logger: MatchLogger,
     ) -> Box<dyn PlayerHandle> {
-        let (tx, rx) = oneshot::channel();
         let (server_msg_snd, server_msg_recv) = mpsc::unbounded_channel();
-        self.router.put(
+
+        enum ConnState {
+            Connected {
+                client_messages: ClientMessages,
+            },
+            Awaiting {
+                rx: oneshot::Receiver<ClientMessages>,
+            },
+        }
+
+        let conn_state = {
+            // during this block, we hold a lock on the routing table.
+
+            let mut routing_table = self.router.routing_table.lock().unwrap();
+            let connection_state = routing_table
+                .remove(&self.player_key)
+                .expect("player key not found in routing table");
+
+            match connection_state {
+                PlayerConnectionState::Reserved => {
+                    let (tx, rx) = oneshot::channel();
+                    routing_table.insert(
                         self.player_key.clone(),
-            SyncThingData {
+                        PlayerConnectionState::ServerConnected {
                             tx,
                             server_messages: server_msg_recv,
                         },
                     );
+                    ConnState::Awaiting { rx }
+                }
+                PlayerConnectionState::ClientConnected {
+                    tx,
+                    client_messages,
+                } => {
+                    tx.send(server_msg_recv).unwrap();
+                    ConnState::Connected { client_messages }
+                }
+                PlayerConnectionState::ServerConnected { .. } => panic!("server already connected"),
+            }
+        };
 
+        let maybe_client_messages = match conn_state {
+            ConnState::Connected { client_messages } => Some(client_messages),
+            ConnState::Awaiting { rx } => {
                 let fut = tokio::time::timeout(Duration::from_secs(10), rx);
                 match fut.await {
-            Ok(Ok(client_messages)) => {
-                // let client_messages = rx.await.unwrap();
+                    Ok(Ok(client_messages)) => Some(client_messages),
+                    _ => {
+                        // ensure router cleanup
+                        self.router.take(&self.player_key);
+                        None
+                    }
+                }
+            }
+        };
+
+        if let Some(client_messages) = maybe_client_messages {
             tokio::spawn(handle_bot_messages(
                 player_id,
                 event_bus.clone(),
                 client_messages,
             ));
         }
-            _ => {
-                // ensure router cleanup
-                self.router.take(&self.player_key);
-            }
-        };
 
         // If the player did not connect, the receiving half of `sender`
         // will be dropped here, resulting in a time-out for every turn.
@@ -217,7 +310,7 @@ async fn handle_bot_messages(
     event_bus: Arc<Mutex<EventBus>>,
     mut messages: Streaming<pb::PlayerApiClientMessage>,
 ) {
-    // TODO: can this be writte nmore nicely?
+    // TODO: can this be written more nicely?
     while let Some(message) = messages.message().await.unwrap() {
         match message.client_message {
             Some(pb::PlayerApiClientMessageType::Action(resp)) => {