113 lines
3.2 KiB
TypeScript
113 lines
3.2 KiB
TypeScript
import { Transport } from "../shared/transport.js";
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import { JSONRPCMessage, JSONRPCMessageSchema } from "../types.js";
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/**
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* Client transport for SSE: this will connect to a server using Server-Sent Events for receiving
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* messages and make separate POST requests for sending messages.
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*
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* This uses the EventSource API in browsers. You can install the `eventsource` package for Node.js.
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*/
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export class SSEClientTransport implements Transport {
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private _eventSource?: EventSource;
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private _endpoint?: URL;
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private _abortController?: AbortController;
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private _url: URL;
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onclose?: () => void;
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onerror?: (error: Error) => void;
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onmessage?: (message: JSONRPCMessage) => void;
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constructor(url: URL) {
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this._url = url;
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}
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start(): Promise<void> {
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if (this._eventSource) {
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throw new Error(
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"SSEClientTransport already started! If using Client class, note that connect() calls start() automatically.",
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);
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}
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return new Promise((resolve, reject) => {
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this._eventSource = new EventSource(this._url.href);
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this._abortController = new AbortController();
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this._eventSource.onerror = (event) => {
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const error = new Error(`SSE error: ${JSON.stringify(event)}`);
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reject(error);
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this.onerror?.(error);
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};
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this._eventSource.onopen = () => {
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// The connection is open, but we need to wait for the endpoint to be received.
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};
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this._eventSource.addEventListener("endpoint", (event: Event) => {
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const messageEvent = event as MessageEvent;
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try {
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this._endpoint = new URL(messageEvent.data, this._url);
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if (this._endpoint.origin !== this._url.origin) {
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throw new Error(
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`Endpoint origin does not match connection origin: ${this._endpoint.origin}`,
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);
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}
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} catch (error) {
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reject(error);
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this.onerror?.(error as Error);
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void this.close();
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return;
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}
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resolve();
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});
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this._eventSource.onmessage = (event: Event) => {
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const messageEvent = event as MessageEvent;
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let message: JSONRPCMessage;
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try {
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message = JSONRPCMessageSchema.parse(JSON.parse(messageEvent.data));
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} catch (error) {
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this.onerror?.(error as Error);
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return;
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}
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this.onmessage?.(message);
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};
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});
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}
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async close(): Promise<void> {
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this._abortController?.abort();
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this._eventSource?.close();
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this.onclose?.();
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}
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async send(message: JSONRPCMessage): Promise<void> {
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if (!this._endpoint) {
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throw new Error("Not connected");
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}
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try {
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const response = await fetch(this._endpoint, {
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method: "POST",
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headers: {
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"Content-Type": "application/json",
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},
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body: JSON.stringify(message),
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signal: this._abortController?.signal,
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});
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if (!response.ok) {
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const text = await response.text().catch(() => null);
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throw new Error(
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`Error POSTing to endpoint (HTTP ${response.status}): ${text}`,
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);
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}
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} catch (error) {
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this.onerror?.(error as Error);
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throw error;
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}
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}
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}
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