59 lines
1.9 KiB
JavaScript
59 lines
1.9 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) try { this._socket.close() } 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}) => this._eventTarget.dispatchEvent(new MessageEvent("message", {data})))
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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) 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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} |