import { QueryClient } from '@tanstack/react-query';

/**
 * QueryClient configuration for TanStack Query
 *
 * Default options:
 * - staleTime: 5 minutes (data considered fresh)
 * - gcTime: 10 minutes (garbage collection time - unused data kept in cache)
 * - refetchOnWindowFocus: true (refetch when window regains focus)
 * - retry: 3 attempts with exponential backoff
 *
 * @returns Configured QueryClient instance
 */
export const queryClient = new QueryClient({
  defaultOptions: {
    queries: {
      staleTime: 5 * 60 * 1000,        // 5 minutes
      gcTime: 10 * 60 * 1000,          // 10 minutes (replaces cacheTime in v5)
      refetchOnWindowFocus: true,       // Refetch when user returns to tab
      refetchOnReconnect: true,         // Refetch when network reconnects
      retry: 3,                         // Retry failed requests 3 times
      retryDelay: (attemptIndex) => Math.min(1000 * 2 ** attemptIndex, 30000),
    },
    mutations: {
      retry: 1,                         // Retry mutations once
    },
  },
});