import { prisma } from '@/lib/prisma'

/**
 * 作品过稿是首轮通过指标的唯一权威数据源。这个任务不复制作品数据，
 * 只用 updatedAt 增量检查项目、版本和评审记录，给看板提供可观测的
 * 后台同步心跳；看板查询仍直接读取作品过稿后台，避免出现两套事实。
 */
export type WorkReviewDashboardSyncStatus = 'idle' | 'syncing' | 'ready' | 'error'

export type WorkReviewDashboardSyncState = {
  status: WorkReviewDashboardSyncStatus
  lastSyncedAt: string | null
  sourceCursor: string | null
  rowsChecked: number
  lastError: string | null
}

type MutableState = {
  status: WorkReviewDashboardSyncStatus
  lastSyncedAt: Date | null
  sourceCursor: Date | null
  rowsChecked: number
  lastError: string | null
  running: boolean
}

type SyncGlobal = typeof globalThis & {
  __workReviewDashboardSync?: MutableState
  __workReviewDashboardSyncStarted?: boolean
}

const INITIAL_SYNC_DELAY_MS = 5_000
const DEFAULT_SYNC_INTERVAL_MS = 60 * 60 * 1_000
// A small overlap prevents a write that races the query from being skipped.
const CURSOR_OVERLAP_MS = 60_000

function getState(): MutableState {
  const globalState = globalThis as SyncGlobal
  if (!globalState.__workReviewDashboardSync) {
    globalState.__workReviewDashboardSync = {
      status: 'idle',
      lastSyncedAt: null,
      sourceCursor: null,
      rowsChecked: 0,
      lastError: null,
      running: false,
    }
  }
  return globalState.__workReviewDashboardSync
}

export function getWorkReviewDashboardSyncState(): WorkReviewDashboardSyncState {
  const state = getState()
  return {
    status: state.status,
    lastSyncedAt: state.lastSyncedAt?.toISOString() || null,
    sourceCursor: state.sourceCursor?.toISOString() || null,
    rowsChecked: state.rowsChecked,
    lastError: state.lastError,
  }
}

function getIncrementalWhere(cursor: Date | null) {
  if (!cursor) return { versions: { some: { version: 1 } } }
  const changedAfter = new Date(cursor.getTime() - CURSOR_OVERLAP_MS)
  return {
    versions: { some: { version: 1 } },
    OR: [
      { updatedAt: { gt: changedAfter } },
      { versions: { some: { version: 1, updatedAt: { gt: changedAfter } } } },
      {
        versions: {
          some: {
            version: 1,
            reviews: { some: { updatedAt: { gt: changedAfter } } },
          },
        },
      },
    ],
  }
}

function maxDate(values: Array<Date | null | undefined>) {
  return values.reduce<Date | null>((current, value) => {
    if (!value) return current
    return !current || value.getTime() > current.getTime() ? value : current
  }, null)
}

/** Run one idempotent, read-only incremental source check. */
export async function syncWorkReviewDashboardIncremental() {
  const state = getState()
  if (state.running) return { skipped: true, rowsChecked: 0, lastSyncedAt: state.lastSyncedAt }
  state.running = true
  state.status = 'syncing'
  state.lastError = null

  try {
    const rows = await prisma.workReviewProject.findMany({
      where: getIncrementalWhere(state.sourceCursor),
      select: {
        updatedAt: true,
        versions: {
          where: { version: 1 },
          select: {
            updatedAt: true,
            reviews: { select: { updatedAt: true } },
          },
        },
      },
      orderBy: [{ updatedAt: 'asc' }, { id: 'asc' }],
    })

    const sourceCursor = rows.reduce<Date | null>((cursor, project) => {
      const projectDates = project.versions.flatMap((version) => [
        version.updatedAt,
        ...version.reviews.map((review) => review.updatedAt),
      ])
      return maxDate([cursor, project.updatedAt, ...projectDates])
    }, state.sourceCursor)

    state.sourceCursor = sourceCursor || state.sourceCursor
    state.rowsChecked = rows.length
    state.lastSyncedAt = new Date()
    state.status = 'ready'
    return { skipped: false, rowsChecked: rows.length, lastSyncedAt: state.lastSyncedAt }
  } catch (error) {
    state.status = 'error'
    state.lastError = (error instanceof Error ? error.message : String(error)).slice(0, 500)
    throw error
  } finally {
    state.running = false
  }
}

export function ensureHourlyWorkReviewDashboardSyncStarted() {
  const globalState = globalThis as SyncGlobal
  if (globalState.__workReviewDashboardSyncStarted) return
  globalState.__workReviewDashboardSyncStarted = true

  const configuredHours = Number(process.env.WORK_REVIEW_SYNC_INTERVAL_HOURS || 1)
  const intervalMs = Number.isFinite(configuredHours) && configuredHours > 0
    ? Math.max(5 * 60 * 1_000, configuredHours * 60 * 60 * 1_000)
    : DEFAULT_SYNC_INTERVAL_MS

  const runOnce = () => {
    void syncWorkReviewDashboardIncremental()
      .then((result) => {
        if (result.skipped) {
          console.info('[work-review-dashboard-sync] 上一轮仍在检查，本轮跳过')
          return
        }
        console.info(`[work-review-dashboard-sync] 增量检查完成：${result.rowsChecked} 个变更项目`)
      })
      .catch((error) => console.warn('[work-review-dashboard-sync] 增量检查失败：', error))
  }

  const initialTimer = setTimeout(runOnce, INITIAL_SYNC_DELAY_MS)
  initialTimer.unref?.()
  const interval = setInterval(runOnce, intervalMs)
  interval.unref?.()
  console.info(
    `[work-review-dashboard-sync] 已调度每小时增量检查，周期 ${Math.round(intervalMs / 60_000)} 分钟`,
  )
}