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import type { Handlers } from "./types";
const MAX_ATTEMPTS = 6;
/**
* Browser side of the gateway socket.
*
* The cookie is HttpOnly and handled by the browser; this class never reads or
* stores a credential. A transient close reconnects inside the gateway's grace
* window; a deliberate takeover stops for good.
*/
export class Gateway {
private socket: WebSocket | null = null;
private stopped = false;
private replaced = false;
private attempts = 0;
private timer: number | undefined;
constructor(
private readonly url: string,
private readonly handlers: Handlers,
) {}
connect(): void {
if (this.stopped) return;
this.clearTimer();
let socket: WebSocket;
try {
socket = new WebSocket(this.url);
} catch {
const retrying = this.scheduleReconnect();
if (!retrying) this.handlers.onClosed(false);
return;
}
this.socket = socket;
socket.addEventListener("open", () => {
this.attempts = 0;
this.handlers.onOpen();
});
socket.addEventListener("message", (event) => {
let message: any;
try {
message = JSON.parse(String(event.data));
} catch {
return;
}
switch (message.type) {
case "hello":
this.handlers.onHello(message);
break;
case "view":
this.handlers.onView(message.view);
break;
case "notice":
this.handlers.onNotice(String(message.text ?? ""));
break;
case "error":
this.handlers.onError(String(message.text ?? ""));
break;
case "replaced":
this.replaced = true;
this.handlers.onReplaced();
break;
case "pong":
this.handlers.onPong();
break;
}
});
socket.addEventListener("close", () => {
const wasThisSocket = this.socket === socket;
if (wasThisSocket) this.socket = null;
if (this.replaced || this.stopped) {
this.handlers.onClosed(false);
return;
}
const retrying = this.scheduleReconnect();
this.handlers.onClosed(retrying);
});
socket.addEventListener("error", () => {
// The close event follows; reconnect is scheduled there.
});
}
send(command: unknown): void {
if (this.socket?.readyState !== WebSocket.OPEN) return;
this.socket.send(JSON.stringify({ type: "command", command }));
}
ping(): void {
if (this.socket?.readyState === WebSocket.OPEN) {
this.socket.send(JSON.stringify({ type: "ping" }));
}
}
close(): void {
this.stopped = true;
this.clearTimer();
this.socket?.close();
}
private scheduleReconnect(): boolean {
if (this.stopped || this.replaced || this.attempts >= MAX_ATTEMPTS) return false;
this.attempts += 1;
const delay = Math.min(250 * 2 ** (this.attempts - 1), 4000);
this.timer = window.setTimeout(() => this.connect(), delay);
return true;
}
private clearTimer(): void {
if (this.timer !== undefined) {
window.clearTimeout(this.timer);
this.timer = undefined;
}
}
}
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