import type { Heartbeat } from '$lib/types';

type Listener = (hb: Heartbeat) => void;

const listeners = new Set<Listener>();
let es: EventSource | null = null;

function connect() {
	if (es) return;

	es = new EventSource('/api/stream');

	es.addEventListener('connected', () => {
		console.log('[sse] conectado');
	});

	es.addEventListener('heartbeat', (event: MessageEvent) => {
		try {
			const hb: Heartbeat = JSON.parse(event.data);
			listeners.forEach((fn) => fn(hb));
		} catch {
			// ignore parse errors
		}
	});

	es.onerror = () => {
		console.warn('[sse] erro — reconectando...');
	};
}

export function subscribeHeartbeats(fn: Listener) {
	listeners.add(fn);
	connect();

	return () => {
		listeners.delete(fn);
		if (listeners.size === 0 && es) {
			es.close();
			es = null;
		}
	};
}