/**
 * 素材归属转移
 *
 * 此前系统里的"转移"是隐式发生的：在编辑素材时改掉作者，`Material.userId`
 * 被直接覆盖，既不留转移流水，也查不到最初的上传者是谁。而 `MaterialTransfer`
 * 表和 `Material` 上的 originalOwnerId / transferredAt / transferredBy / transferNote
 * 四个字段虽然早已建好，却从未被写入过。
 *
 * 本模块把归属变更收敛成一件有据可查的事：
 *   - `MaterialTransfer` 记录每一次转移的流水（谁转给谁、谁操作的、为什么）
 *   - `Material` 上的四个字段保存当前状态（最初属于谁、最近一次何时被谁转移）
 *
 * originalOwnerId 只在首次转移时落定，之后不再变动，用于永久保留"最初是谁上传的"。
 */

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

/** 转移来源，便于区分是人工单条操作还是离职批量交接 */
export const TRANSFER_REASON = {
  /** 编辑素材时更换作者 */
  EDIT: '编辑素材时更换归属人',
  /** 账号离职/归档后的批量交接 */
  HANDOVER: '账号离职交接',
} as const

/**
 * 计算随归属变更一并写入素材的转移字段。
 *
 * @param currentOwnerId 变更前的归属人
 * @param existingOriginalOwnerId 素材上已有的最初所有者，为空表示这是第一次转移
 */
export function buildMaterialTransferFields(params: {
  currentOwnerId: string
  existingOriginalOwnerId?: string | null
  operatorUserId: string
  note?: string | null
}) {
  const { currentOwnerId, existingOriginalOwnerId, operatorUserId, note } = params
  return {
    // 首次转移时记下最初的上传者，后续转移不再覆盖
    originalOwnerId: existingOriginalOwnerId || currentOwnerId,
    transferredAt: new Date(),
    transferredBy: operatorUserId,
    transferNote: note ?? null,
  }
}

/** 写入一条转移流水。可传入事务客户端以保证与素材更新的原子性。 */
export async function recordMaterialTransfer(
  client: { materialTransfer: { create: (args: any) => Promise<any> } },
  params: {
    materialId: string
    fromUserId: string
    toUserId: string
    operatorUserId: string
    note?: string | null
  }
): Promise<void> {
  await client.materialTransfer.create({
    data: {
      materialId: params.materialId,
      fromUserId: params.fromUserId,
      toUserId: params.toUserId,
      transferredBy: params.operatorUserId,
      transferNote: params.note ?? null,
    },
  })
}

export interface BulkTransferResult {
  /** 转出账号名下的素材总数 */
  total: number
  /** 实际完成转移的条数 */
  transferred: number
  /** 失败条数 */
  failed: number
  /** 是否为预演，预演不写入任何数据 */
  dryRun: boolean
  failures: Array<{ materialId: string; reason: string }>
}

/**
 * 把某个账号名下的素材整体转移给另一个账号。
 *
 * 主要面向离职交接：账号归档后无法登录，其名下素材无人可维护，而系统此前
 * 只能在编辑页里一条一条改作者。
 *
 * 逐条使用事务，保证「素材归属 + 署名 + 转移流水」三者一致；单条失败不影响
 * 其余素材，失败明细一并返回，便于重试与核对。
 */
export async function transferMaterialsBetweenUsers(params: {
  fromUserId: string
  toUserId: string
  operatorUserId: string
  note?: string | null
  /** 仅转移指定素材类型，不传则转移全部 */
  materialTypes?: string[]
  /** 预演模式：只统计不写入 */
  dryRun?: boolean
}): Promise<BulkTransferResult> {
  const {
    fromUserId,
    toUserId,
    operatorUserId,
    note = TRANSFER_REASON.HANDOVER,
    materialTypes,
    dryRun = false,
  } = params

  if (fromUserId === toUserId) {
    throw new Error('转出与接收账号不能是同一个人')
  }

  const toUser = await prisma.user.findUnique({
    where: { id: toUserId },
    select: { id: true, username: true, isActive: true, archivedAt: true },
  })
  if (!toUser) throw new Error('接收账号不存在')
  if (toUser.archivedAt || !toUser.isActive) {
    throw new Error('接收账号已归档或已停用，不能作为素材归属人')
  }

  const materials = await prisma.material.findMany({
    where: {
      userId: fromUserId,
      deletedAt: null,
      ...(materialTypes?.length ? { materialType: { in: materialTypes } } : {}),
    },
    select: { id: true, userId: true, originalOwnerId: true },
  })

  const result: BulkTransferResult = {
    total: materials.length,
    transferred: 0,
    failed: 0,
    dryRun,
    failures: [],
  }

  if (dryRun) return result

  for (const material of materials) {
    try {
      await prisma.$transaction(async (tx) => {
        await tx.material.update({
          where: { id: material.id },
          data: {
            userId: toUserId,
            // 署名与归属保持一致，避免出现"作者写着甲、归属却是乙"
            authorName: toUser.username,
            ...buildMaterialTransferFields({
              currentOwnerId: material.userId,
              existingOriginalOwnerId: material.originalOwnerId,
              operatorUserId,
              note,
            }),
          },
        })

        await recordMaterialTransfer(tx, {
          materialId: material.id,
          fromUserId: material.userId,
          toUserId,
          operatorUserId,
          note,
        })
      })
      result.transferred += 1
    } catch (error) {
      result.failed += 1
      result.failures.push({
        materialId: material.id,
        reason: error instanceof Error ? error.message : String(error),
      })
    }
  }

  return result
}

/** 统计某账号名下待交接的素材数量，用于离职处理前的预览 */
export async function countMaterialsByOwner(userId: string): Promise<number> {
  return prisma.material.count({ where: { userId, deletedAt: null } })
}

/** 读取一条素材的完整转移历史，最近一次在前 */
export async function listMaterialTransferHistory(materialId: string) {
  return prisma.materialTransfer.findMany({
    where: { materialId },
    orderBy: { transferredAt: 'desc' },
    select: {
      id: true,
      transferredAt: true,
      transferNote: true,
      fromUser: { select: { id: true, username: true, realName: true } },
      toUser: { select: { id: true, username: true, realName: true } },
      operator: { select: { id: true, username: true, realName: true } },
    },
  })
}

// ============================================================
// 部门托管
// ============================================================

export const CUSTODY_REASON = {
  RESIGNATION: '原归属人离职，素材由所在部门接管',
} as const

export interface CustodyResult {
  /** 待托管素材数 */
  total: number
  /** 实际完成托管数 */
  custodied: number
  departmentName: string | null
  dryRun: boolean
}

/**
 * 把某个账号名下的素材托管给部门。
 *
 * 与 `transferMaterialsBetweenUsers` 的本质区别：**托管不转移归属人，也不改署名**。
 * `userId` 与 `authorName` 保持原样——素材是谁做的，永远记在谁名下；变的只是
 * 「现在谁负责维护它」。人离职后，其所在部门的成员即可接手。
 *
 * 不指定部门时自动落到该账号所属部门。已处于托管状态的素材会被跳过。
 */
export async function custodyMaterialsToDepartment(params: {
  fromUserId: string
  /** 不指定时自动取该账号所属部门 */
  departmentId?: string
  reason?: string
  dryRun?: boolean
}): Promise<CustodyResult> {
  const { fromUserId, reason = CUSTODY_REASON.RESIGNATION, dryRun = false } = params

  const user = await prisma.user.findUnique({
    where: { id: fromUserId },
    select: { username: true, departmentId: true, department: true },
  })
  if (!user) throw new Error('账号不存在')

  // 优先用显式指定的部门，其次是账号的部门外键，最后按部门名称兜底反查
  let departmentId = params.departmentId ?? user.departmentId ?? null
  if (!departmentId && user.department?.trim()) {
    const matched = await prisma.department.findUnique({
      where: { name: user.department.trim() },
      select: { id: true },
    })
    departmentId = matched?.id ?? null
  }
  if (!departmentId) {
    throw new Error(
      `账号「${user.username}」没有可识别的所属部门，无法自动托管，请显式指定部门`,
    )
  }

  const department = await prisma.department.findUnique({
    where: { id: departmentId },
    select: { id: true, name: true },
  })
  if (!department) throw new Error('托管部门不存在')

  const where = {
    userId: fromUserId,
    deletedAt: null,
    custodyDepartmentId: null,
  }
  const total = await prisma.material.count({ where })

  if (dryRun) {
    return { total, custodied: 0, departmentName: department.name, dryRun: true }
  }

  const updated = await prisma.material.updateMany({
    where,
    data: {
      custodyDepartmentId: department.id,
      custodyAt: new Date(),
      custodyReason: reason,
    },
  })

  return {
    total,
    custodied: updated.count,
    departmentName: department.name,
    dryRun: false,
  }
}

/**
 * 把所有已归档（离职）账号名下尚未托管的素材，批量交由各自部门接管。
 *
 * 逐个账号处理，某个账号失败（例如识别不出部门）不影响其余账号。
 */
export async function custodyMaterialsOfArchivedUsers(params: {
  reason?: string
  dryRun?: boolean
} = {}): Promise<{
  accounts: number
  totalMaterials: number
  custodied: number
  details: Array<{ username: string; department: string | null; count: number }>
  skipped: Array<{ username: string; count: number; reason: string }>
}> {
  const { reason = CUSTODY_REASON.RESIGNATION, dryRun = false } = params

  const archived = await prisma.user.findMany({
    where: { archivedAt: { not: null } },
    select: { id: true, username: true },
  })

  const details: Array<{ username: string; department: string | null; count: number }> = []
  const skipped: Array<{ username: string; count: number; reason: string }> = []
  let totalMaterials = 0
  let custodied = 0

  for (const user of archived) {
    const pending = await prisma.material.count({
      where: { userId: user.id, deletedAt: null, custodyDepartmentId: null },
    })
    if (pending === 0) continue

    totalMaterials += pending
    try {
      const result = await custodyMaterialsToDepartment({
        fromUserId: user.id,
        reason,
        dryRun,
      })
      custodied += result.custodied
      details.push({
        username: user.username,
        department: result.departmentName,
        count: dryRun ? result.total : result.custodied,
      })
    } catch (error) {
      skipped.push({
        username: user.username,
        count: pending,
        reason: error instanceof Error ? error.message : String(error),
      })
    }
  }

  return { accounts: details.length, totalMaterials, custodied, details, skipped }
}