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import { sleep } from '@decky/ui';
import Logger from './logger';
declare global {
export var DeckyBackend: WSRouter;
}
enum MessageType {
ERROR = -1,
// Call-reply, Frontend -> Backend -> Frontend
CALL = 0,
REPLY = 1,
// Pub/Sub, Backend -> Frontend
EVENT = 3,
}
interface CallMessage {
type: MessageType.CALL;
args: any[];
route: string;
id: number;
}
interface ReplyMessage {
type: MessageType.REPLY;
result: any;
id: number;
}
interface ErrorMessage {
type: MessageType.ERROR;
error: { name: string; error: string; traceback: string | null };
id: number;
}
/**
* An error from a python call
*/
export class PyError extends Error {
pythonTraceback: string | null;
constructor(name: string, error: string, traceback: string | null) {
super(error);
this.name = `Python ${name}`;
if (traceback) {
// traceback will always start with `Traceback (most recent call last):`
// so this will make it say `Python Traceback (most recent call last):` after the JS callback
this.stack = this.stack + '\n\nPython ' + traceback;
}
this.pythonTraceback = traceback;
}
}
interface EventMessage {
type: MessageType.EVENT;
event: string;
args: any;
}
type Message = CallMessage | ReplyMessage | ErrorMessage | EventMessage;
// Helper to resolve a promise from the outside
interface PromiseResolver<T> {
resolve: (res: T) => void;
reject: (error: PyError) => void;
promise: Promise<T>;
}
export class WSRouter extends Logger {
runningCalls: Map<number, PromiseResolver<any>> = new Map();
eventListeners: Map<string, Set<(...args: any) => any>> = new Map();
ws?: WebSocket;
connectPromise?: Promise<void>;
// Used to map results and errors to calls
reqId: number = 0;
constructor() {
super('WSRouter');
}
connect() {
return (this.connectPromise = new Promise<void>((resolve) => {
// Auth is a query param as JS WebSocket doesn't support headers
this.ws = new WebSocket(`ws://127.0.0.1:1337/ws?auth=${deckyAuthToken}`);
this.ws.addEventListener('open', () => {
this.debug('WS Connected');
resolve();
delete this.connectPromise;
});
this.ws.addEventListener('message', this.onMessage.bind(this));
this.ws.addEventListener('close', this.onError.bind(this));
// this.ws.addEventListener('error', this.onError.bind(this));
}));
}
createPromiseResolver<T>(): PromiseResolver<T> {
let resolver: Partial<PromiseResolver<T>> = {};
const promise = new Promise<T>((resolve, reject) => {
resolver.resolve = resolve;
resolver.reject = reject;
});
resolver.promise = promise;
return resolver as PromiseResolver<T>;
}
async write(data: Message) {
if (this.connectPromise) await this.connectPromise;
this.ws?.send(JSON.stringify(data));
}
addEventListener(event: string, listener: (...args: any) => any) {
if (!this.eventListeners.has(event)) {
this.eventListeners.set(event, new Set([listener]));
} else {
this.eventListeners.get(event)?.add(listener);
}
return listener;
}
removeEventListener(event: string, listener: (...args: any) => any) {
if (this.eventListeners.has(event)) {
const set = this.eventListeners.get(event);
set?.delete(listener);
if (set?.size === 0) {
this.eventListeners.delete(event);
}
}
}
async onMessage(msg: MessageEvent) {
try {
const data = JSON.parse(msg.data) as Message;
switch (data.type) {
case MessageType.REPLY:
if (this.runningCalls.has(data.id)) {
this.runningCalls.get(data.id)!.resolve(data.result);
this.runningCalls.delete(data.id);
this.debug(`Resolved PY call ${data.id} with value`, data.result);
}
break;
case MessageType.ERROR:
if (this.runningCalls.has(data.id)) {
let err = new PyError(data.error.name, data.error.error, data.error.traceback);
this.runningCalls.get(data.id)!.reject(err);
this.runningCalls.delete(data.id);
this.debug(`Rejected PY call ${data.id} with error`, data.error);
}
break;
case MessageType.EVENT:
this.debug(`Recieved event ${data.event} with args`, data.args);
if (this.eventListeners.has(data.event)) {
for (const listener of this.eventListeners.get(data.event)!) {
(async () => {
try {
await listener(...data.args);
} catch (e) {
this.error(`error in event ${data.event}`, e, listener);
}
})();
}
} else {
this.warn(`event ${data.event} has no listeners`);
}
break;
default:
this.error('Unknown message type', data);
break;
}
} catch (e) {
this.error('Error parsing WebSocket message', e);
}
}
// this.call<[number, number], string>('methodName', 1, 2);
call<Args extends any[] = [], Return = void>(route: string, ...args: Args): Promise<Return> {
const resolver = this.createPromiseResolver<Return>();
const id = ++this.reqId;
this.runningCalls.set(id, resolver);
this.debug(`Calling PY method ${route} with args`, args);
this.write({ type: MessageType.CALL, route, args, id });
return resolver.promise;
}
callable<Args extends any[] = [], Return = void>(route: string): (...args: Args) => Promise<Return> {
return (...args) => this.call<Args, Return>(route, ...args);
}
async onError(error: any) {
this.error('WS DISCONNECTED', error);
// TODO queue up lost messages and send them once we connect again
await sleep(5000);
await this.connect();
}
}
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