From e36d7bdde255bb7b48838f06ba196d846b691d62 Mon Sep 17 00:00:00 2001
From: Jordan Orelli <jordanorelli@gmail.com>
Date: Wed, 4 Nov 2020 04:39:22 +0000
Subject: [PATCH] fixing up some outbox race conditions

---
 internal/sim/player.go | 16 +++++++++++++++-
 internal/sim/world.go  |  6 +++---
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/internal/sim/player.go b/internal/sim/player.go
index e07afa0..a45303a 100644
--- a/internal/sim/player.go
+++ b/internal/sim/player.go
@@ -50,7 +50,7 @@ func (p *player) start(c chan Request, conn *websocket.Conn, r *room) {
 		welcome.Players[p.name] = wp
 	}
 	p.Info("sending welcome to outbox")
-	p.outbox <- wire.Response{Re: 1, Body: welcome}
+	p.send(wire.Response{Re: 1, Body: welcome})
 	p.Info("sent welcome, starting loops")
 	p.stop = make(chan bool, 1)
 	go p.readLoop(c, conn)
@@ -115,6 +115,20 @@ func (p *player) runLoop(conn *websocket.Conn) {
 	}
 }
 
+func (p *player) send(res wire.Response) bool {
+	select {
+	case p.outbox <- res:
+		return true
+	default:
+		select {
+		case <-p.outbox:
+			return p.send(res)
+		default:
+			return false
+		}
+	}
+}
+
 func sendResponse(conn *websocket.Conn, res wire.Response) error {
 	payload, err := json.Marshal(res)
 	if err != nil {
diff --git a/internal/sim/world.go b/internal/sim/world.go
index a5435ff..f9bffca 100644
--- a/internal/sim/world.go
+++ b/internal/sim/world.go
@@ -193,9 +193,9 @@ func (w *world) tick(d time.Duration) {
 
 			res := req.Wants.exec(w, r, p, req.Seq)
 			if res.reply != nil {
-				p.outbox <- wire.Response{Re: req.Seq, Body: res.reply}
+				p.send(wire.Response{Re: req.Seq, Body: res.reply})
 			} else {
-				p.outbox <- wire.Response{Re: req.Seq, Body: wire.OK{}}
+				p.send(wire.Response{Re: req.Seq, Body: wire.OK{}})
 			}
 		}
 	}
@@ -214,7 +214,7 @@ func (w *world) tick(d time.Duration) {
 		}
 
 		for _, p := range r.players {
-			p.outbox <- wire.Response{Body: frame}
+			p.send(wire.Response{Body: frame})
 		}
 	}
 }