test_dashboard/dashboard/src/hooks/useStats.js

import { useQuery, useQueryClient } from '@tanstack/react-query'
import { useEffect } from 'react'
import { getScanStatus, getStats } from '../lib/api'

export function useStats() {
  const queryClient = useQueryClient()

  // Subscribe to SSE updates once; invalidate both stats and tests on any update
  useEffect(() => {
    const es = new EventSource('/api/events')
    es.onmessage = (e) => {
      try {
        const data = JSON.parse(e.data)
        if (data.type === 'update') {
          queryClient.invalidateQueries({ queryKey: ['stats'] })
          queryClient.invalidateQueries({ queryKey: ['tests'] })
        }
      } catch { /* ignore malformed */ }
    }
    return () => es.close()
  }, [queryClient])

  const scanStatusQuery = useQuery({
    queryKey: ['scanStatus'],
    queryFn: getScanStatus,
    refetchInterval: (query) => (query.state.data?.scanning ? 1000 : 5000),
  })

  const isScanning = scanStatusQuery.data?.scanning ?? true

  const statsQuery = useQuery({
    queryKey: ['stats'],
    queryFn: getStats,
    enabled: !isScanning,
    refetchInterval: isScanning ? false : 30_000,
  })

  return {
    ...statsQuery,
    isScanning,
  }
}