import type { TranscodeTaskFn } from './video-transcode-queue'

export const VIDEO_TRANSCODE_RECOVERY_INTERVAL_MS = 60_000

interface RecoverySchedulerOptions {
  scan?: () => Promise<number>
  intervalMs?: number
  onError?: (error: unknown) => void
}

export interface VideoTranscodeRecoveryScheduler {
  initial: Promise<number>
  runNow: () => Promise<number>
  stop: () => void
}

/**
 * 建立不会重叠的恢复调度器。一次扫描失败只记录错误，下一次周期仍会重新尝试。
 */
export function createVideoTranscodeRecoveryScheduler(
  options: RecoverySchedulerOptions = {},
): VideoTranscodeRecoveryScheduler {
  const scan = options.scan || (async () => {
    const [{ transcodeQueue, VIDEO_MATERIAL_TYPES }, { executeTranscodeTask }] = await Promise.all([
      import('./video-transcode-queue'),
      import('./video-transcode-task'),
    ])
    return transcodeQueue.runRecoveryScan(
      executeTranscodeTask as TranscodeTaskFn,
      { requeuePending: true, videoTypes: VIDEO_MATERIAL_TYPES },
    )
  })
  const onError = options.onError || ((error) => {
    console.error('[VideoTranscodeRecovery] Recovery scan failed:', error)
  })
  let inFlight: Promise<number> | null = null

  const runNow = (): Promise<number> => {
    if (inFlight) {
      return inFlight
    }
    inFlight = scan()
      .catch((error) => {
        onError(error)
        throw error
      })
      .finally(() => {
        inFlight = null
      })
    return inFlight
  }

  const initial = runNow()
  const timer = setInterval(() => {
    void runNow().catch(() => {
      // onError 已记录；保留定时器，让下一轮继续重试。
    })
  }, options.intervalMs || VIDEO_TRANSCODE_RECOVERY_INTERVAL_MS)
  ;(timer as NodeJS.Timeout).unref?.()

  return {
    initial,
    runNow,
    stop: () => clearInterval(timer),
  }
}