/**
 * useRealtimeSync — mounts the SSE connection once at the app level and
 * wires incoming events to React Query cache invalidation.
 *
 * Event → query key mapping:
 *   agent.status   → ['agents']
 *   agent.task     → ['tasks'], ['agents']
 *   agent.progress → ['tasks'], ['agents']
 *   fleet.update   → ['agents'], ['sessions'], ['tasks']
 */
import { useQueryClient } from '@tanstack/react-query'
import { useCallback } from 'react'
import { useSSE, type SSEMessage, type SSEStatus } from './useSSE'

export function useRealtimeSync(): { sseStatus: SSEStatus } {
  const queryClient = useQueryClient()

  const handleMessage = useCallback(
    (msg: SSEMessage) => {
      switch (msg.type) {
        case 'agent.status':
          queryClient.invalidateQueries({ queryKey: ['agents'] })
          break

        case 'agent.task':
          queryClient.invalidateQueries({ queryKey: ['tasks'] })
          queryClient.invalidateQueries({ queryKey: ['agents'] })
          break

        case 'agent.progress':
          queryClient.invalidateQueries({ queryKey: ['tasks'] })
          queryClient.invalidateQueries({ queryKey: ['agents'] })
          break

        case 'fleet.update':
          queryClient.invalidateQueries({ queryKey: ['agents'] })
          queryClient.invalidateQueries({ queryKey: ['sessions'] })
          queryClient.invalidateQueries({ queryKey: ['tasks'] })
          break

        default:
          // 'connected' and unknown events — no action needed
          break
      }
    },
    [queryClient],
  )

  const { status: sseStatus } = useSSE({ onMessage: handleMessage })

  return { sseStatus }
}