mirror of
https://github.com/samuelthomas2774/nxapi.git
synced 2026-10-26 19:43:11 -05:00
Add custom EventSource using fetch, automatically upgrade to SSE
This commit is contained in:
Samuel Elliott
279
src/util/eventsource.ts
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279
src/util/eventsource.ts
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@@ -0,0 +1,279 @@
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import { Buffer } from 'node:buffer';
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import { fetch, Headers, Response } from 'undici';
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import createDebug from './debug.js';
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const debug = createDebug('nxapi:util:eventsource');
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export class ErrorEvent extends Event {
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constructor(
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readonly error: Error,
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readonly message = error.message,
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) {
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super('error');
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}
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}
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export enum EventSourceReadyState {
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CONNECTING = 0,
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OPEN = 1,
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CLOSED = 2,
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}
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export interface EventSourceInit extends globalThis.EventSourceInit {
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authorisation?: string | (() => string);
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useragent?: string;
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}
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type Listener<T extends string> =
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T extends 'error' ? [type: T, handler: (error: ErrorEvent) => void] :
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T extends 'open' ? [type: T, handler: (event: Event) => void] :
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[type: T, handler: (event: MessageEvent<string>) => void];
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export default class EventSource {
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protected _response: Response | null = null;
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protected _controller: AbortController | null = null;
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protected _closed = false;
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protected _id: string | null = null;
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protected _retry_after: number | null = null;
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protected readonly _authorisation: string | (() => string) | null = null;
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protected readonly _useragent: string | null = null;
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readonly withCredentials = false;
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onerror?: (error: ErrorEvent) => void;
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onmessage?: (message: MessageEvent<string>) => void;
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onopen?: (event: Event) => void;
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onAnyMessage?: (message: MessageEvent<string>) => void;
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protected readonly _listeners: Listener<string>[] = [];
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constructor(readonly url: string, init?: EventSourceInit) {
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if (init?.withCredentials) debug('init.withCredentials is not supported');
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if (init?.authorisation) this._authorisation = init.authorisation;
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if (init?.useragent) this._useragent = init.useragent;
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this._connect();
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}
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get readyState(): EventSourceReadyState {
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if (this._closed) return EventSourceReadyState.CLOSED;
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if (this._response) return EventSourceReadyState.OPEN;
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return EventSourceReadyState.CONNECTING;
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}
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get response(): Response | null {
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return this._response;
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}
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addEventListener<T extends string>(event: T, handler: Listener<T>[1]) {
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this._listeners.push([event, handler]);
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}
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removeEventListener<T extends string>(event: T, handler?: Listener<T>[1]) {
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let index;
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while ((index = this._listeners.findIndex(listener =>
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listener[0] === event && (!handler || listener[1] === handler)
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)) >= 0) {
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this._listeners.splice(index, 1);
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}
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}
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protected _fetch(signal: AbortSignal) {
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const headers = new Headers({
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'Accept': 'text/event-stream',
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});
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const authorisation = typeof this._authorisation === 'function' ?
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this._authorisation.call(null) : this._authorisation;
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if (authorisation) headers.append('Authorization', authorisation);
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if (this._useragent) headers.append('User-Agent', this._useragent);
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if (typeof this._id === 'string') {
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headers.append('Last-Event-Id', this._id);
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}
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return fetch(this.url, {
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headers,
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signal,
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keepalive: true,
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});
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}
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protected _connect() {
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const controller = new AbortController();
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this._fetch(controller.signal).then(async response => {
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if (this._closed || this._response) {
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controller.abort();
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return;
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}
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this._response = response;
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this._controller = controller;
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if (!response.ok) {
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debug('Non-200 response code', await response.text());
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controller.abort();
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return this._handleConnectionClosed();
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}
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if (!response.headers.get('Content-Type')?.match(/^text\/event-stream($|;)/)) {
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debug('Response type is not text/event-stream', await response.text());
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controller.abort();
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return this._handleConnectionClosed();
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}
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if (!response.body) {
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debug('Response does not include a body');
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controller.abort();
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return this._handleConnectionClosed();
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}
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const url = new URL(this.url);
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url.search = '';
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url.hash = '';
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debug('Connected to %s', url);
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const event = new Event('open');
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this.dispatchEvent(event);
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const reader = response.body.getReader();
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return this._handleResponseStream(reader);
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}).then(() => {
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this._handleConnectionClosed();
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}, err => {
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this._handleConnectionClosed(err);
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});
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}
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protected async _handleResponseStream(reader: ReadableStreamDefaultReader<Uint8Array>) {
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let buffer = Buffer.alloc(0);
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const n = '\n'.charCodeAt(0);
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let value: Uint8Array | undefined;
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let done = false;
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while (!done) {
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({value, done} = await reader.read());
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if (!value) continue;
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let index;
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while ((index = value.findIndex(v => v === n)) >= 0) {
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const line = Buffer.concat([buffer, value.slice(0, index)]);
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if (buffer.length) buffer = Buffer.alloc(0);
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value = value.slice(index + 1);
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this._handleLine(new Uint8Array(line));
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}
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// Move any remaining data
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buffer = Buffer.concat([buffer, value]);
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}
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}
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_message_event: string | null = null;
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_message_data: Uint8Array | null = null;
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_message_id: string | null = null;
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protected _handleLine(line: Uint8Array) {
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if (line.length === 0) {
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const event = new MessageEvent(this._message_event ?? 'message', {
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data: this._message_data ? new TextDecoder().decode(this._message_data) : '',
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lastEventId: this._message_id ?? undefined,
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// source: this as unknown as MessageEventSource,
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});
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this._message_data = null;
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this.onAnyMessage?.call(this, event);
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if (typeof this._message_event === 'string') {
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for (const [type, handler] of this._listeners) {
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if (type !== this._message_event) continue;
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handler.call(this, event);
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}
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this._message_event = null;
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} else {
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this.onmessage?.call(null, event);
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for (const [type, handler] of this._listeners) {
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if (type !== 'message') continue;
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handler.call(this, event);
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}
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}
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if (typeof this._message_id === 'string') {
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this._id = this._message_id;
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this._message_id = null;
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}
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return;
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}
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const index = line.indexOf(':'.charCodeAt(0));
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if (index < 0) return;
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const tag = new TextDecoder().decode(line.slice(0, index));
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const data = line.slice(index + (line[index + 1] === ' '.charCodeAt(0) ? 2 : 1));
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if (tag === 'event') {
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this._message_event = new TextDecoder().decode(data);
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} else if (tag === 'data') {
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this._message_data = this._message_data ?
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new Uint8Array(Buffer.concat([this._message_data, Buffer.from('\n'), data])) :
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data;
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} else if (tag === 'id') {
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this._message_id = new TextDecoder().decode(data);
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} else if (tag === 'retry') {
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const retry = parseInt(new TextDecoder().decode(data));
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if (!isNaN(retry)) this._retry_after = retry;
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} else if (tag) {
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debug('Unknown message type "%s"', tag);
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}
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}
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protected async _handleConnectionClosed(error?: Error) {
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this._response = null;
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if (this._closed) {
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return;
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}
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if (error) {
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const event = new ErrorEvent(error);
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this.dispatchEvent(event);
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}
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const wait = Math.max(1000, this._retry_after ?? 0);
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await new Promise(rs => setTimeout(rs, wait));
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this._connect();
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}
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close() {
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this._closed = true;
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this._controller?.abort();
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}
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dispatchEvent(event: Event) {
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// @ts-expect-error
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this['on' + event.type]?.call(this, event);
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for (const [type, handler] of this._listeners as Listener<string>[]) {
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if (type !== event.type) continue;
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// @ts-expect-error
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handler.call(this, event);
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}
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}
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}
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