scratch-vm/src/util/scratch-link-websocket.js
2022-02-16 15:02:35 -08:00

133 lines
3.8 KiB
JavaScript

/**
* This class provides a ScratchLinkSocket implementation using WebSockets,
* attempting to connect with the locally installed Scratch-Link.
*
* To connect with ScratchLink without WebSockets, you must implement all of the
* public methods in this class.
* - open()
* - close()
* - setOn[Open|Close|Error]
* - setHandleMessage
* - sendMessage(msgObj)
* - isOpen()
*/
class ScratchLinkWebSocket {
constructor (type) {
this._type = type;
this._onOpen = null;
this._onClose = null;
this._onError = null;
this._handleMessage = null;
this._ws = null;
}
open () {
if (!(this._onOpen && this._onClose && this._onError && this._handleMessage)) {
throw new Error('Must set open, close, message and error handlers before calling open on the socket');
}
let pathname;
switch (this._type) {
case 'BLE':
pathname = 'scratch/ble';
break;
case 'BT':
pathname = 'scratch/bt';
break;
default:
throw new Error(`Unknown ScratchLink socket Type: ${this._type}`);
}
// Try ws:// (the new way) and wss:// (the old way) simultaneously. If either connects, close the other. If we
// were to try one and fall back to the other on failure, that could mean a delay of 30 seconds or more for
// those who need the fallback.
// If both connections fail we should report only one error.
const setSocket = (socketToUse, socketToClose) => {
socketToClose.onopen = socketToClose.onerror = null;
socketToClose.close();
this._ws = socketToUse;
this._ws.onopen = this._onOpen;
this._ws.onclose = this._onClose;
this._ws.onerror = this._onError;
this._ws.onmessage = this._onMessage.bind(this);
};
const ws = new WebSocket(`ws://127.0.0.1:20111/${pathname}`);
const wss = new WebSocket(`wss://device-manager.scratch.mit.edu:20110/${pathname}`);
const connectTimeout = setTimeout(() => {
// neither socket succeeded before the timeout
setSocket(ws, wss);
this._ws.onerror(new Event('timeout'));
}, 15 * 1000);
ws.onopen = openEvent => {
clearTimeout(connectTimeout);
setSocket(ws, wss);
this._ws.onopen(openEvent);
};
wss.onopen = openEvent => {
clearTimeout(connectTimeout);
setSocket(wss, ws);
this._ws.onopen(openEvent);
};
let wsError;
let wssError;
const errorHandler = () => {
// if only one has received an error, we haven't overall failed yet
if (wsError && wssError) {
clearTimeout(connectTimeout);
setSocket(ws, wss);
this._ws.onerror(wsError);
}
};
ws.onerror = errorEvent => {
wsError = errorEvent;
errorHandler();
};
wss.onerror = errorEvent => {
wssError = errorEvent;
errorHandler();
};
}
close () {
this._ws.close();
this._ws = null;
}
sendMessage (message) {
const messageText = JSON.stringify(message);
this._ws.send(messageText);
}
setOnOpen (fn) {
this._onOpen = fn;
}
setOnClose (fn) {
this._onClose = fn;
}
setOnError (fn) {
this._onError = fn;
}
setHandleMessage (fn) {
this._handleMessage = fn;
}
isOpen () {
return this._ws && this._ws.readyState === this._ws.OPEN;
}
_onMessage (e) {
const json = JSON.parse(e.data);
this._handleMessage(json);
}
}
module.exports = ScratchLinkWebSocket;