import { onMounted, onUnmounted, ref } from "vue";
import { getToken } from "../api";

export interface SacDashboardStreamMessage {
  type?: string;
  last_event_id?: number | null;
}

/** SSE /api/v1/stream/events — вызывает onNewEvent при новом last_event_id (после первого тика). */
export function useSacLiveEventStream(onNewEvent: () => void) {
  const live = ref(false);
  let eventSource: EventSource | null = null;
  let lastKnownEventDbId: number | null = null;

  function handleStreamMessage(msg: SacDashboardStreamMessage) {
    if (msg.type !== "dashboard") return;
    const incoming = msg.last_event_id;
    if (incoming === undefined) return;

    if (incoming === null) {
      if (lastKnownEventDbId !== null) {
        onNewEvent();
      }
      lastKnownEventDbId = null;
      return;
    }

    if (lastKnownEventDbId === null) {
      lastKnownEventDbId = incoming;
      return;
    }

    if (incoming !== lastKnownEventDbId) {
      lastKnownEventDbId = incoming;
      onNewEvent();
    }
  }

  function connect() {
    const token = getToken();
    if (!token) return;

    eventSource?.close();
    const url = `/api/v1/stream/events`;
    eventSource = new EventSource(url);

    eventSource.onopen = () => {
      live.value = true;
    };

    eventSource.onmessage = (ev) => {
      try {
        handleStreamMessage(JSON.parse(ev.data) as SacDashboardStreamMessage);
      } catch {
        /* ignore malformed SSE */
      }
    };

    eventSource.onerror = () => {
      live.value = false;
    };
  }

  onMounted(() => connect());

  onUnmounted(() => {
    eventSource?.close();
    eventSource = null;
    live.value = false;
  });

  return { live };
}