From ec819d37ea04a6855705f9e9da00fb69dc0d6708 Mon Sep 17 00:00:00 2001
From: Nikita Vilunov <nikita@vilunov.me>
Date: Tue, 14 Feb 2023 01:12:27 +0100
Subject: [PATCH] make room a data structure behind a rwlock instead of an
 actor

---
 src/core/player.rs |   8 ++--
 src/core/room.rs   | 109 ++++++++++++++-------------------------------
 2 files changed, 38 insertions(+), 79 deletions(-)

diff --git a/src/core/player.rs b/src/core/player.rs
index 58a6a50..e31e977 100644
--- a/src/core/player.rs
+++ b/src/core/player.rs
@@ -55,7 +55,7 @@ pub struct PlayerHandle {
     tx: Sender<PlayerCommand>,
 }
 impl PlayerHandle {
-    pub async fn subscribe(&mut self) -> PlayerConnection {
+    pub async fn subscribe(&self) -> PlayerConnection {
         let (sender, receiver) = channel(32);
         let (promise, deferred) = oneshot();
         self.tx
@@ -70,7 +70,7 @@ impl PlayerHandle {
     }
 
     pub async fn send_message(
-        &mut self,
+        &self,
         room_id: RoomId,
         connection_id: ConnectionId,
         body: String,
@@ -84,12 +84,12 @@ impl PlayerHandle {
             .await;
     }
 
-    pub async fn join_room(&mut self, room_id: RoomId) {
+    pub async fn join_room(&self, room_id: RoomId) {
         self.tx.send(PlayerCommand::JoinRoom { room_id }).await;
     }
 
     pub async fn receive_message(
-        &mut self,
+        &self,
         room_id: RoomId,
         author: PlayerId,
         connection_id: ConnectionId,
diff --git a/src/core/room.rs b/src/core/room.rs
index 74c7eea..c725740 100644
--- a/src/core/room.rs
+++ b/src/core/room.rs
@@ -6,7 +6,7 @@ use std::{
 };
 
 use prometheus::{IntGauge, Registry as MetricRegistry};
-use tokio::sync::mpsc::{channel, Sender};
+use tokio::sync::RwLock as AsyncRwLock;
 
 use crate::{
     core::player::{PlayerHandle, PlayerId},
@@ -35,15 +35,16 @@ impl RoomRegistry {
     }
 
     pub fn get_or_create_room(&mut self, room_id: RoomId) -> RoomHandle {
-        let room = Room {
-            subscriptions: HashMap::new(),
-        };
         let mut inner = self.0.write().unwrap();
-        if let Some((room_handle, _)) = inner.rooms.get(&room_id) {
+        if let Some(room_handle) = inner.rooms.get(&room_id) {
             room_handle.clone()
         } else {
-            let (room_handle, fiber) = room.launch(room_id.clone());
-            inner.rooms.insert(room_id, (room_handle.clone(), fiber));
+            let room = Room {
+                room_id: room_id.clone(),
+                subscriptions: HashMap::new(),
+            };
+            let room_handle = RoomHandle(Arc::new(AsyncRwLock::new(room)));
+            inner.rooms.insert(room_id, room_handle.clone());
             inner.metric_active_rooms.inc();
             room_handle
         }
@@ -52,31 +53,21 @@ impl RoomRegistry {
     pub fn get_room(&self, room_id: RoomId) -> Option<RoomHandle> {
         let inner = self.0.read().unwrap();
         let res = inner.rooms.get(&room_id);
-        res.map(|r| r.0.clone())
+        res.map(|r| r.clone())
     }
 }
 
 struct RoomRegistryInner {
-    rooms: HashMap<RoomId, (RoomHandle, JoinHandle<Room>)>,
+    rooms: HashMap<RoomId, RoomHandle>,
     metric_active_rooms: IntGauge,
 }
 
 #[derive(Clone)]
-pub struct RoomHandle {
-    tx: Sender<RoomCommand>,
-}
+pub struct RoomHandle(Arc<AsyncRwLock<Room>>);
 impl RoomHandle {
-    pub async fn subscribe(&mut self, player_id: PlayerId, player: PlayerHandle) {
-        match self
-            .tx
-            .send(RoomCommand::AddSubscriber { player_id, player })
-            .await
-        {
-            Ok(_) => {}
-            Err(_) => {
-                tracing::error!("Room mailbox is closed unexpectedly");
-            }
-        };
+    pub async fn subscribe(&mut self, player_id: PlayerId, player_handle: PlayerHandle) {
+        let mut lock = self.0.write().await;
+        lock.add_subscriber(player_id, player_handle);
     }
 
     pub async fn send_message(
@@ -85,64 +76,32 @@ impl RoomHandle {
         connection_id: ConnectionId,
         body: String,
     ) {
-        self.tx
-            .send(RoomCommand::SendMessage {
-                player_id,
-                connection_id,
-                body,
-            })
-            .await;
+        let lock = self.0.read().await;
+        lock.send_message(player_id, connection_id, body).await;
     }
 }
 
-enum RoomCommand {
-    AddSubscriber {
-        player_id: PlayerId,
-        player: PlayerHandle,
-    },
-    SendMessage {
-        player_id: PlayerId,
-        connection_id: ConnectionId,
-        body: String,
-    },
-}
-
 struct Room {
+    room_id: RoomId,
     subscriptions: HashMap<PlayerId, PlayerHandle>,
 }
 impl Room {
-    fn launch(mut self, room_id: RoomId) -> (RoomHandle, JoinHandle<Room>) {
-        let (tx, mut rx) = channel(32);
-        let fiber = tokio::task::spawn(async move {
-            tracing::info!("Starting room fiber");
-            while let Some(a) = rx.recv().await {
-                match a {
-                    RoomCommand::AddSubscriber { player_id, player } => {
-                        tracing::info!("Adding a subscriber to room");
-                        self.subscriptions.insert(player_id, player);
-                    }
-                    RoomCommand::SendMessage {
-                        player_id,
-                        connection_id,
-                        body,
-                    } => {
-                        tracing::info!("Adding a message to room");
-                        for (_, sub) in &mut self.subscriptions {
-                            log::info!("Sending a message from room to player");
-                            sub.receive_message(
-                                room_id.clone(),
-                                player_id.clone(),
-                                connection_id.clone(),
-                                body.clone(),
-                            )
-                            .await;
-                        }
-                    }
-                }
-            }
-            tracing::info!("Stopping room fiber");
-            self
-        });
-        (RoomHandle { tx }, fiber)
+    fn add_subscriber(&mut self, player_id: PlayerId, player_handle: PlayerHandle) {
+        tracing::info!("Adding a subscriber to room");
+        self.subscriptions.insert(player_id, player_handle);
+    }
+
+    async fn send_message(&self, player_id: PlayerId, connection_id: ConnectionId, body: String) {
+        tracing::info!("Adding a message to room");
+        for (_, sub) in &self.subscriptions {
+            log::info!("Sending a message from room to player");
+            sub.receive_message(
+                self.room_id.clone(),
+                player_id.clone(),
+                connection_id.clone(),
+                body.clone(),
+            )
+            .await;
+        }
     }
 }