import { pipeline } from "node:stream";
import { addStream, deleteStream } from "~/server/streams";

export default defineEventHandler(async (event) => {
	const encoder = new TextEncoder();
	const source = event.headers.get("x-forwarded-for");
	console.log(`starting event stream for ${source}`)
	const stream = new TransformStream<string, Uint8Array>({
		transform(chunk, controller) {
			controller.enqueue(encoder.encode(chunk));
		},
		flush(controller) {
			console.log(`finished event stream for ${source}`);
			deleteStream(stream.writable);
		},
		// @ts-expect-error experimental API
		cancel(reason) {
			console.log(`cancelled event stream for ${source}`);
			deleteStream(stream.writable);
		}
	})
	addStream(stream.writable);

	// Workaround to properly handle stream errors. See https://github.com/unjs/h3/issues/986
	setHeader(event, "Access-Control-Allow-Origin", "*");
	setHeader(event, "Content-Type", "text/event-stream");
	event.node.res.write("data: connected\n\n"); // Produce a response immediately to avoid the reply waiting for content.
	pipeline(stream.readable as unknown as NodeJS.ReadableStream, event.node.res, (err) => { /* ignore */ });
	event._handled = true;
});