import { emit } from "./bus.js";

/**
 * SSE client con reconnect exponencial y try-catch en parseo.
 * Si el server reinicia o un evento viene malformado, no rompe la app.
 */

let _es = null;
let _retryDelay = 1000;
let _retryTimer = null;
const MAX_RETRY = 30_000;

const EVENTS = [
  ["conversation.upsert", "conversation:upsert"],
  ["run.created", "run:created"],
  ["takeover.created", "takeover:created"],
  ["order.created", "order:created"],
];

function safeParse(rawData, evName) {
  try {
    return JSON.parse(rawData);
  } catch (err) {
    console.error(`[sse] bad payload for ${evName}:`, err?.message || err);
    return null;
  }
}

function attach(es) {
  es.addEventListener("hello", () => {
    _retryDelay = 1000; // reset on success
    emit("sse:status", { ok: true });
  });

  for (const [serverName, busName] of EVENTS) {
    es.addEventListener(serverName, (e) => {
      const data = safeParse(e.data, serverName);
      if (data !== null) emit(busName, data);
    });
  }

  es.onerror = () => {
    emit("sse:status", { ok: false });
    try { es.close(); } catch (_) {}
    if (_es === es) _es = null;
    scheduleReconnect();
  };
}

function scheduleReconnect() {
  if (_retryTimer) return;
  const delay = _retryDelay;
  _retryTimer = setTimeout(() => {
    _retryTimer = null;
    connectSSE();
  }, delay);
  _retryDelay = Math.min(_retryDelay * 2, MAX_RETRY);
}

export function connectSSE() {
  if (_retryTimer) {
    clearTimeout(_retryTimer);
    _retryTimer = null;
  }
  if (_es) {
    try { _es.close(); } catch (_) {}
  }
  _es = new EventSource("/stream");
  attach(_es);
  return _es;
}