From 1e3084d7604dbe725d57d227921f3b4290c16265 Mon Sep 17 00:00:00 2001
From: Luciano Iam <lucianito@gmail.com>
Date: Sun, 12 Apr 2020 15:36:51 +0200
Subject: WebSockets: detect channel drop in ardour.js

---
 share/web_surfaces/shared/ardour.js  | 40 +++++++++++++++++++++++++++---------
 share/web_surfaces/shared/channel.js | 20 ++++++++++--------
 2 files changed, 42 insertions(+), 18 deletions(-)

diff --git a/share/web_surfaces/shared/ardour.js b/share/web_surfaces/shared/ardour.js
index b5ce9b1c1d..770881b4c4 100644
--- a/share/web_surfaces/shared/ardour.js
+++ b/share/web_surfaces/shared/ardour.js
@@ -21,17 +21,27 @@ import { MessageChannel, Message, ANode } from './channel.js';
 export class Ardour {
 
 	constructor () {
-		this.channel = new MessageChannel(location.host);
-		this.channel.messageCallback = (msg) => this._onChannelMessage(msg);
-		this.pendingRequest = null;
+		this._channel = new MessageChannel(location.host);
+		this._channel.errorCallback = (error) => this.errorCallback();
+		this._channel.messageCallback = (msg) => this._onChannelMessage(msg);
+		this._pendingRequest = null;
 	}
 
 	async open () {
-		await this.channel.open();
+		this._channel.closeCallback = () => {
+			this.errorCallback(new Error('Message channel unexpectedly closed'));
+		};
+
+		await this._channel.open();
 	}
 
 	close () {
-		this.channel.close();
+		this._channel.closeCallback = () => {};
+		this._channel.close();
+	}
+	
+	errorCallback (error) {
+		// empty
 	}
 
 	messageCallback (msg) {
@@ -120,21 +130,21 @@ export class Ardour {
 
 	_send (node, addr, val) {
 		const msg = new Message(node, addr, val);
-		this.channel.send(msg);
+		this._channel.send(msg);
 		return msg;
 	}
 
 	async _sendAndReceive (node, addr, val) {
 		return new Promise((resolve, reject) => {
 			const hash = this._send(node, addr, val).hash;
-			this.pendingRequest = {resolve: resolve, hash: hash};
+			this._pendingRequest = {resolve: resolve, hash: hash};
 		});
 	}
 
 	_onChannelMessage (msg) {
-		if (this.pendingRequest && (this.pendingRequest.hash == msg.hash)) {
-			this.pendingRequest.resolve(msg.val);
-			this.pendingRequest = null;
+		if (this._pendingRequest && (this._pendingRequest.hash == msg.hash)) {
+			this._pendingRequest.resolve(msg.val);
+			this._pendingRequest = null;
 		} else {
 			this.messageCallback(msg);
 		}
@@ -145,3 +155,13 @@ export class Ardour {
 	}
 
 }
+
+async function main() {
+	const ard = new Ardour();
+	ard.errorCallback = (error) => {
+		alert(error);
+	};
+	await ard.open();
+}
+
+main();
diff --git a/share/web_surfaces/shared/channel.js b/share/web_surfaces/shared/channel.js
index 03b87979d2..8c6f8afdcd 100644
--- a/share/web_surfaces/shared/channel.js
+++ b/share/web_surfaces/shared/channel.js
@@ -41,28 +41,32 @@ export class MessageChannel {
 
 	constructor (host) {
 		// https://developer.mozilla.org/en-US/docs/Web/API/URL/host
-		this.host = host;
+		this._host = host;
 	}
 
 	async open () {
 		return new Promise((resolve, reject) => {
-			this.socket = new WebSocket(`ws://${this.host}`);
+			this._socket = new WebSocket(`ws://${this._host}`);
 
-			this.socket.onclose = () => this.closeCallback();
+			this._socket.onclose = () => this.closeCallback();
 
-			this.socket.onerror = (error) => this.errorCallback(error);
+			this._socket.onerror = (error) => this.errorCallback(error);
 
-			this.socket.onmessage = (event) => {
+			this._socket.onmessage = (event) => {
 				this.messageCallback (Message.fromJsonText(event.data));
 			};
 
-			this.socket.onopen = resolve;
+			this._socket.onopen = resolve;
 		});
 	}
 
+	async close () {
+		this._socket.close();
+	}
+
 	send (msg) {
-		if (this.socket) {
-			this.socket.send(msg.toJsonText());
+		if (this._socket) {
+			this._socket.send(msg.toJsonText());
 		} else {
 			throw Error('MessageChannel: cannot call send() before open()');
 		}
-- 
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