import { useEffect } from 'react';
import { useQueryClient } from '@tanstack/react-query';
import { io, type Socket } from 'socket.io-client';
import { API_URL } from '../api/client';
import { useAuth } from '../auth/AuthContext';

let sharedSocket: Socket | null = null;

function getSocket(token: string): Socket {
  if (!sharedSocket) {
    sharedSocket = io(API_URL, { auth: { token }, transports: ['websocket', 'polling'] });
  }
  return sharedSocket;
}

// Joins the Socket.io room for a campaign and keeps React Query's cache in
// sync with server-pushed events (HP/condition changes, encounter rounds,
// new characters) so every open tab in the campaign updates live.
export function useCampaignSocket(campaignId: string | undefined) {
  const { token } = useAuth();
  const qc = useQueryClient();

  useEffect(() => {
    if (!campaignId || !token) return;
    const socket = getSocket(token);
    socket.emit('campaign:join', campaignId);

    const onCharacterUpdated = () => {
      qc.invalidateQueries({ queryKey: ['campaign', campaignId, 'characters'] });
      qc.invalidateQueries({ queryKey: ['character'] });
    };
    const onCharacterCreated = () => {
      qc.invalidateQueries({ queryKey: ['campaign', campaignId, 'characters'] });
    };
    const onParticipantUpdated = () => {
      qc.invalidateQueries({ queryKey: ['encounter'] });
    };
    const onRoundAdvanced = () => {
      qc.invalidateQueries({ queryKey: ['encounter'] });
    };

    socket.on('character:updated', onCharacterUpdated);
    socket.on('character:created', onCharacterCreated);
    socket.on('encounter:participant-updated', onParticipantUpdated);
    socket.on('encounter:round-advanced', onRoundAdvanced);

    return () => {
      socket.emit('campaign:leave', campaignId);
      socket.off('character:updated', onCharacterUpdated);
      socket.off('character:created', onCharacterCreated);
      socket.off('encounter:participant-updated', onParticipantUpdated);
      socket.off('encounter:round-advanced', onRoundAdvanced);
    };
  }, [campaignId, token, qc]);
}