Scrum4Me/lib/realtime/use-solo-realtime.ts

// ST-803 + ST-805 (refactor in ST-806-acceptance): client-side hook die de
// Solo Paneel realtime stream beheert.
//
// - Mount in de (app)-layout via SoloRealtimeBridge zodat hij Server Action-
//   refreshes overleeft (anders kapt Next.js' soft-navigation de SSE).
// - Opent EventSource('/api/realtime/solo?product_id=...') wanneer
//   productId niet null is; sluit de stream als productId null wordt.
// - Reconnect met exponential backoff (1s → 30s, reset bij ready).
// - Pauseert bij document.visibilityState === 'hidden', resumes bij visible.
// - Cleanup op unmount.
// - Connection-status (status, showConnectingIndicator) wordt naar de
//   solo-store geschreven; UI-componenten lezen daar uit.
// - Dispatcht events naar de solo-store via handleRealtimeEvent. Task-
//   updates worden in document.startViewTransition + flushSync gewikkeld
//   zodat het kanban-kaartje soepel naar zijn nieuwe kolom animeert
//   (animatie A — vereist view-transition-name op de cards).

'use client'

import { useEffect, useRef } from 'react'
import { flushSync } from 'react-dom'
import { useSoloStore } from '@/stores/solo-store'
import type { RealtimeEvent, RealtimeStatus } from '@/stores/solo-store'

const BACKOFF_START_MS = 1_000
const BACKOFF_MAX_MS = 30_000
const CONNECTING_INDICATOR_DELAY_MS = 2_000

export function useSoloRealtime(productId: string | null) {
  const sourceRef = useRef<EventSource | null>(null)
  const backoffRef = useRef<number>(BACKOFF_START_MS)
  const reconnectTimerRef = useRef<ReturnType<typeof setTimeout> | null>(null)
  const indicatorTimerRef = useRef<ReturnType<typeof setTimeout> | null>(null)

  useEffect(() => {
    const setStatus = useSoloStore.getState().setRealtimeStatus
    const handleEvent = useSoloStore.getState().handleRealtimeEvent

    if (!productId) {
      // Geen actief product (gebruiker zit niet op /solo) — stream uit
      setStatus('disconnected', false)
      return
    }

    const close = () => {
      if (sourceRef.current) {
        sourceRef.current.close()
        sourceRef.current = null
      }
      if (reconnectTimerRef.current) {
        clearTimeout(reconnectTimerRef.current)
        reconnectTimerRef.current = null
      }
    }

    const scheduleIndicator = (next: RealtimeStatus) => {
      if (indicatorTimerRef.current) {
        clearTimeout(indicatorTimerRef.current)
        indicatorTimerRef.current = null
      }
      if (next === 'open') {
        setStatus('open', false)
      } else {
        // Status meteen bijwerken, indicator pas na 2s — voorkomt flikker
        // bij microscopische disconnects.
        setStatus(next, false)
        indicatorTimerRef.current = setTimeout(() => {
          setStatus(useSoloStore.getState().realtimeStatus, true)
        }, CONNECTING_INDICATOR_DELAY_MS)
      }
    }

    const connect = () => {
      close()
      scheduleIndicator('connecting')

      const source = new EventSource(
        `/api/realtime/solo?product_id=${encodeURIComponent(productId)}`,
      )
      sourceRef.current = source

      source.addEventListener('ready', () => {
        backoffRef.current = BACKOFF_START_MS
        scheduleIndicator('open')
      })

      source.onmessage = (e) => {
        if (!e.data) return
        try {
          const payload = JSON.parse(e.data) as RealtimeEvent
          // Animatie A: kanban-move animeren via View Transitions API. Voor
          // task UPDATE-events wrap'en we de store-update in een view
          // transition. flushSync forceert React om synchroon te renderen
          // tijdens de transition-callback zodat de nieuwe DOM-state wordt
          // gesnapshot voor de animatie.
          const animate =
            payload.entity === 'task' &&
            payload.op === 'U' &&
            typeof document !== 'undefined' &&
            typeof (document as Document & { startViewTransition?: unknown }).startViewTransition ===
              'function'
          if (animate) {
            ;(
              document as Document & {
                startViewTransition: (cb: () => void) => unknown
              }
            ).startViewTransition(() => {
              flushSync(() => handleEvent(payload))
            })
          } else {
            handleEvent(payload)
          }
        } catch (err) {
          if (process.env.NODE_ENV !== 'production') {
            console.error('[realtime] failed to parse event', err, e.data)
          }
        }
      }

      source.onerror = () => {
        if (sourceRef.current !== source) return
        close()
        scheduleIndicator('disconnected')

        if (document.visibilityState === 'hidden') return
        const delay = backoffRef.current
        backoffRef.current = Math.min(backoffRef.current * 2, BACKOFF_MAX_MS)
        reconnectTimerRef.current = setTimeout(connect, delay)
      }
    }

    const onVisibility = () => {
      if (document.visibilityState === 'hidden') {
        close()
        scheduleIndicator('disconnected')
      } else if (sourceRef.current === null) {
        backoffRef.current = BACKOFF_START_MS
        connect()
      }
    }

    if (document.visibilityState === 'visible') {
      connect()
    }
    document.addEventListener('visibilitychange', onVisibility)

    return () => {
      document.removeEventListener('visibilitychange', onVisibility)
      if (indicatorTimerRef.current) clearTimeout(indicatorTimerRef.current)
      close()
    }
  }, [productId])
}