66 lines
2.0 KiB
JavaScript
66 lines
2.0 KiB
JavaScript
export default class ReconnectingWebSocket {
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constructor(url) {
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if (url instanceof URL) {
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this.url = url;
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} else {
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this.url = new URL(url);
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}
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this.connected = false;
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this._eventTarget = new EventTarget();
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this._backoff = 250; // milliseconds, doubled before use
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this._lastConnect = 0;
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this._socket = null;
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this._unsent = [];
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this._connect(true);
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}
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_connect(first) {
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if (this._socket)
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try {
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this._socket.close();
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} catch (e) {}
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try {
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this._socket = new WebSocket(this.url.href);
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} catch (e) {
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this._reconnecting = false;
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return this._reconnect();
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}
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this._socket.addEventListener("close", () => this._reconnect());
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this._socket.addEventListener("error", () => this._reconnect());
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this._socket.addEventListener("message", ({ data }) => {
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this._eventTarget.dispatchEvent(new MessageEvent("message", { data }));
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});
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this._socket.addEventListener("open", (e) => {
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if (first) this._eventTarget.dispatchEvent(new Event("open"));
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if (this._reconnecting)
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this._eventTarget.dispatchEvent(new Event("reconnected"));
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this._reconnecting = false;
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this._backoff = 250;
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this.connected = true;
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while (this._unsent.length > 0) this._socket.send(this._unsent.shift());
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});
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}
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_reconnect() {
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if (this._reconnecting) return;
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this._eventTarget.dispatchEvent(new Event("reconnecting"));
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this._reconnecting = true;
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this.connected = false;
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this._backoff *= 2; // exponential backoff
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setTimeout(() => {
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this._connect();
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}, Math.floor(this._backoff + Math.random() * this._backoff * 0.25 - this._backoff * 0.125));
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}
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send(message) {
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if (this.connected) {
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this._socket.send(message);
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} else {
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this._unsent.push(message);
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}
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}
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addEventListener(...a) {
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return this._eventTarget.addEventListener(...a);
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}
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removeEventListener(...a) {
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return this._eventTarget.removeEventListener(...a);
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}
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}
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