import { useEffect } from 'react';
import { sessionEvents } from './sessionEvents';

const RECONNECT_INITIAL_MS = 1000;
const RECONNECT_MAX_MS = 30000;

export function useUserEvents(): void {
  useEffect(() => {
    let ws: WebSocket | null = null;
    let reconnectTimer: ReturnType<typeof setTimeout> | null = null;
    let reconnectDelay = RECONNECT_INITIAL_MS;
    let unmounted = false;

    const connect = () => {
      if (unmounted) return;
      const url = new URL('/api/ws/user', window.location.href);
      url.protocol = url.protocol === 'https:' ? 'wss:' : 'ws:';
      ws = new WebSocket(url.toString());

      ws.onopen = () => {
        reconnectDelay = RECONNECT_INITIAL_MS;
      };

      ws.onmessage = (ev) => {
        try {
          const parsed: unknown = JSON.parse(ev.data);
          if (parsed && typeof (parsed as { type?: unknown }).type === 'string') {
            sessionEvents.emit(parsed as import('./sessionEvents').SessionEvent);
          }
        } catch (err) {
          console.warn('useUserEvents: failed to parse frame', err);
        }
      };

      ws.onclose = () => {
        if (unmounted) return;
        const delay = reconnectDelay;
        reconnectDelay = Math.min(reconnectDelay * 2, RECONNECT_MAX_MS);
        reconnectTimer = setTimeout(connect, delay);
      };

      ws.onerror = () => {
        // close handler will trigger reconnect; best-effort, ignore failure
        // because the socket may already be closing
        try { ws?.close(); } catch {}
      };
    };

    connect();

    return () => {
      unmounted = true;
      if (reconnectTimer) clearTimeout(reconnectTimer);
      // best-effort cleanup; ignore failure because the socket may already be closed
      if (ws) try { ws.close(); } catch {}
    };
  }, []);
}