Created
June 17, 2022 09:23
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// Server-Sent Events | |
type RequestEvent = Deno.RequestEvent; | |
type Connection = Deno.Conn; | |
type StreamController = ReadableStreamDefaultController<Uint8Array>; | |
const encoder = new TextEncoder(); | |
export class EventConnection { | |
request: RequestEvent; | |
controller: StreamController | undefined; | |
constructor(request: RequestEvent) { | |
this.request = request; | |
} | |
write(text: string) { | |
try { | |
if (this.controller === undefined) { | |
console.log("dropped write", text); | |
return; | |
} | |
this.controller.enqueue(encoder.encode(text)); | |
} catch (e) { | |
// TODO | |
console.log(e); | |
throw e; | |
} | |
} | |
connect_(controller: StreamController) { | |
console.log("connect_"); | |
this.controller = controller; | |
} | |
cancel_(reason: string) { | |
console.log("cancel_"); | |
} | |
async connect() { | |
const self = this; | |
const body = new ReadableStream<Uint8Array>({ | |
start: (controller) => { | |
self.connect_(controller); | |
}, | |
// pull(controller) { | |
// console.log("PULL"); | |
// }, | |
cancel: (reason) => { | |
self.cancel_(reason); | |
} | |
}); | |
const headers = { | |
"Connection": "keep-alive", | |
"Cache-control": "no-cache", | |
"Content-type": "text/event-stream", | |
"Keep-Alive": `timeout=${Number.MAX_SAFE_INTEGER}` | |
}; | |
const response = new Response(body, { headers, status: 200, statusText: "OK" }); | |
await this.request.respondWith(Promise.resolve(response)); | |
} | |
async sendMessage( | |
data: string | object, | |
eventName?: string | undefined, | |
id?: string | undefined | |
) { | |
const text = (typeof data === "string") ? data : JSON.stringify(data, null, 2); | |
if (eventName !== undefined) { | |
this.write(`event: ${eventName}\n`); | |
} | |
if (id !== undefined) { | |
this.write(`id: ${eventName}\n`); | |
} | |
this.write("data: "); | |
this.write(text.replaceAll("\n", "\ndata: ")); // TODO - efficiency | |
this.write("\n\n"); | |
} | |
} |
In the browser:
const source = new EventSource('');
source.addEventListener('message', function(e) {
console.log(e.data);
}, false);
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const ec = new EventConnection(requestEvent);
ec.connect();
ec.sendMessage("any data");