From a88367f527f6343edf4f0bb2d32ccfb5ec54e4d2 Mon Sep 17 00:00:00 2001
From: James Shore <jshore@jamesshore.com>
Date: Fri, 11 Aug 2017 14:06:03 -0700
Subject: [PATCH] Basic spike to remove ghost pointers after timeout

---
 src/server/real_time_server.js | 30 ++++++++++++++++++++++++++++++
 todo.txt                       |  2 ++
 2 files changed, 32 insertions(+)

diff --git a/src/server/real_time_server.js b/src/server/real_time_server.js
index 238d14d45..a60587290 100644
--- a/src/server/real_time_server.js
+++ b/src/server/real_time_server.js
@@ -21,6 +21,7 @@
 
 		constructor() {
 			this._socketIoConnections = {};
+			this._clientTimeouts = {};
 		}
 
 		start(httpServer) {
@@ -30,6 +31,7 @@
 
 			trackSocketIoConnections(this._socketIoConnections, this._ioServer);
 			handleSocketIoEvents(this, this._ioServer);
+			timeoutInactiveClients(this);
 
 			this._httpServer.on("close", failFastIfHttpServerClosed);
 		}
@@ -55,10 +57,23 @@
 
 	};
 
+	function timeoutInactiveClients(self) {
+		setInterval(() => {
+			const now = Date.now();
+			Object.keys(self._clientTimeouts).forEach((clientId) => {
+				const clientLastActivity = self._clientTimeouts[clientId];
+				if (now - clientLastActivity > 1000) {
+					broadcastAndStoreEvent(self, null, new ServerRemovePointerEvent(clientId));
+				}
+			});
+		}, 100);
+	}
+
 	function handleSocketIoEvents(self, ioServer) {
 		ioServer.on("connect", (socket) => {
 			replayPreviousEvents(self, socket);
 			handleClientEvents(self, socket);
+			trackClientTimeouts(self, socket);
 
 			socket.on("disconnect", () => {
 				broadcastAndStoreEvent(self, socket, new ServerRemovePointerEvent(socket.id));
@@ -66,6 +81,21 @@
 		});
 	}
 
+	function trackClientTimeouts(self, socket) {
+		var clientId = socket.id;
+		refreshClientTimeout(self, socket);
+		socket.on(ClientPointerEvent.EVENT_NAME, () => {
+			refreshClientTimeout(self, socket);
+		});
+		socket.on("disconnect", () => {
+			delete self._clientTimeouts[clientId];
+		});
+	}
+
+	function refreshClientTimeout(self, socket) {
+		self._clientTimeouts[socket.id] = Date.now();
+	}
+
 	function replayPreviousEvents(self, socket) {
 		self._eventRepo.replay().forEach((event) => {
 			socket.emit(event.name(), event.payload());
diff --git a/todo.txt b/todo.txt
index c07543637..f3989e24b 100644
--- a/todo.txt
+++ b/todo.txt
@@ -31,6 +31,7 @@ User Stories to finish current MMF:
 - show disconnection warning / other UX when client is disconnected
 - handle server reset smoothly (clear the drawing? re-sync to browsers? not persistence/DB)
 - handle packet loss (What packet loss is possible? TCP handles this? What about unstable cellular connections?)
+	- at least handle glitches in Socket.IO where we don't receive a message
 
 - version synchronization across client/server
 - collision-handling / conflicts / race conditions
@@ -53,6 +54,7 @@ User Stories to finish current MMF:
 
 Engineering Tasks:
 -
+? Factor out domain logic from Socket.IO handling (in RealTimeServer)
 
 To Do on current task:
 -
\ No newline at end of file