/**
 * useTrainingMetricsSSE Hook
 *
 * SSE (Server-Sent Events) hook for real-time training metrics.
 * Connects to the training metrics stream and provides live updates.
 */

'use client'

import { useState, useEffect, useCallback, useRef } from 'react'
import type { TrainingStatus } from './training-metrics-types'

/**
 * Custom hook for SSE-based training metrics
 */
export function useTrainingMetricsSSE(
  apiBase: string,
  jobId: string | null,
  onUpdate?: (status: TrainingStatus) => void
) {
  const [status, setStatus] = useState<TrainingStatus | null>(null)
  const [connected, setConnected] = useState(false)
  const [error, setError] = useState<string | null>(null)
  const eventSourceRef = useRef<EventSource | null>(null)

  useEffect(() => {
    if (!jobId) return

    const url = `${apiBase}/api/klausur/trocr/training/metrics/stream?job_id=${jobId}`
    const eventSource = new EventSource(url)
    eventSourceRef.current = eventSource

    eventSource.onopen = () => {
      setConnected(true)
      setError(null)
    }

    eventSource.onmessage = (event) => {
      try {
        const data = JSON.parse(event.data) as TrainingStatus
        setStatus(data)
        onUpdate?.(data)

        // Close connection when training is done
        if (data.status === 'completed' || data.status === 'failed' || data.status === 'cancelled') {
          eventSource.close()
          setConnected(false)
        }
      } catch (e) {
        console.error('Failed to parse SSE message:', e)
      }
    }

    eventSource.onerror = () => {
      setError('Verbindung zum Server verloren')
      setConnected(false)
      eventSource.close()
    }

    return () => {
      eventSource.close()
      setConnected(false)
    }
  }, [apiBase, jobId, onUpdate])

  const disconnect = useCallback(() => {
    eventSourceRef.current?.close()
    setConnected(false)
  }, [])

  return { status, connected, error, disconnect }
}