/**
 * uds-auth 角色存储 + 权限管理
 *
 * 角色（身份标签；admin 级权限相同）:
 *   super_admin     身份：首位扫码 bootstrap / 显式提权；权限 = admin 级
 *   fallback_admin  身份：应急账号 administrator；权限 = admin 级
 *   admin           身份：用户管理中提权；权限 = admin 级
 *   user            仅看自己会话，无设置 / 不可建工作区
 *
 * admin 级（isAdminClass）权限相同：用户管理、设置、建工作区、默认可看全部会话。
 * 超管只是身份；默认可持有该身份的包括 admin，以及首位扫码加入者（bootstrap）。
 * prefs.viewAllSessions === false 时关闭全览。
 * 持久化: roles.json (roles + prefs + fallbackPasswordHash)
 */
import { createHash, randomBytes } from 'node:crypto'
import { readFile, writeFile, mkdir } from 'node:fs/promises'
import { dirname, resolve } from 'node:path'
import { ROLE_LABELS_ZH } from './i18n.js'

function codedError(code) {
  const err = new Error(code)
  err.code = code
  return err
}

export const ROLES = {
  SUPER_ADMIN: 'super_admin',
  ADMIN: 'admin',
  USER: 'user',
  FALLBACK_ADMIN: 'fallback_admin', // 特殊，UAC 挂了时用，等同 super_admin 权限
}

/** zh labels for list/search; UI should translate via i18n role.* keys. */
export const ROLE_LABELS = ROLE_LABELS_ZH

/** admin 级身份：超管 / 应急 / 管理员（权限相同，仅身份标签不同） */
export function isAdminClass(role) {
  return role === ROLES.SUPER_ADMIN
    || role === ROLES.FALLBACK_ADMIN
    || role === ROLES.ADMIN
}

/**
 * 计算角色权限 (纯函数)
 * @param {string} role
 * @param {{ viewAllSessions?: boolean }} [opts] 个人偏好；admin 级默认可见全部
 */
export function computePermissions(role, opts = {}) {
  const viewAll = !!opts.viewAllSessions
  if (isAdminClass(role)) {
    return {
      canManageUsers: true,
      canAccessSettings: true,
      canToggleViewAllSessions: true,
      canViewAllSessions: viewAll,
      canViewSystemSessions: true,
      canCreateWorkspace: true,
    }
  }
  // user / undefined
  return {
    canManageUsers: false,
    canAccessSettings: false,
    canToggleViewAllSessions: false,
    canViewAllSessions: false,
    canViewSystemSessions: false,
    canCreateWorkspace: false,
  }
}

/** 角色是否允许开启「查看全部会话」（admin 级） */
export function canToggleViewAllSessions(role) {
  return isAdminClass(role)
}

function hashPassword(password) {
  return createHash('sha256').update(password).digest('hex')
}

/** 初始部署默认兜底密码（扫码不可用时用）；可在设置里改密或关闭。 */
export const DEFAULT_FALLBACK_PASSWORD = 'Admin@123'
export const DEFAULT_FALLBACK_USERNAME = 'administrator'

/**
 * RolesStore — 角色存储
 * 内存 Map + 可选 JSON 文件持久化
 *
 * fallback admin: 默认启用，密码 Admin@123；roles.json 显式 null 表示已关闭。
 *   登录路径: POST /uds-auth/api/fallback/login { username, password }
 */
export class RolesStore {
  constructor(options = {}) {
    this._roles = new Map()              // empNo → role
    this._prefs = new Map()              // empNo → { viewAllSessions?: boolean }
    this._firstBootLock = Promise.resolve()
    this._rolesFile = options.rolesFile ? resolve(options.rolesFile) : null
    this._fallbackPasswordHash = null     // SHA-256 hex，null = 未启用
    this._fallbackRateLimit = new Map()   // ip → { count, resetAt }
    this._dirty = false
    this._saveTimer = null
  }

  _ensureDefaultFallback() {
    if (this._fallbackPasswordHash) return
    this._fallbackPasswordHash = hashPassword(DEFAULT_FALLBACK_PASSWORD)
    this._markDirty()
    console.info(
      '[uds-auth] fallback_admin enabled by default'
      + ` (user=${DEFAULT_FALLBACK_USERNAME}, change password in settings)`,
    )
  }

  // === 持久化 ===

  async init() {
    let loadedHash = undefined // undefined = missing / new file; null = explicitly cleared
    if (this._rolesFile) {
      try {
        const raw = await readFile(this._rolesFile, 'utf-8')
        const data = JSON.parse(raw)
        for (const [empNo, role] of Object.entries(data.roles || {})) {
          this._roles.set(empNo, role)
        }
        for (const [empNo, prefs] of Object.entries(data.prefs || {})) {
          if (prefs && typeof prefs === 'object') {
            this._prefs.set(String(empNo), { ...prefs })
          }
        }
        if (Object.prototype.hasOwnProperty.call(data, 'fallbackPasswordHash')) {
          loadedHash = data.fallbackPasswordHash || null
          if (loadedHash) this._fallbackPasswordHash = loadedHash
        }
      } catch (err) {
        if (err.code === 'ENOENT') {
          // 首次启动，文件不存在 — 走默认兜底
        } else {
          console.warn('[uds-auth:RolesStore] Failed to load roles file:', err.message)
        }
      }
    }
    // 无持久化哈希（新部署或旧文件未写该字段）→ 默认开启；显式 null 表示超管已关闭
    if (loadedHash === undefined && !this._fallbackPasswordHash) {
      this._ensureDefaultFallback()
    }
  }

  _markDirty() {
    this._dirty = true
    if (this._saveTimer) return
    this._saveTimer = setTimeout(() => { void this._save() }, 2000)
  }

  /** Flush pending roles/prefs to disk immediately (e.g. view-all toggle). */
  async flush() {
    if (this._saveTimer) {
      clearTimeout(this._saveTimer)
      this._saveTimer = null
    }
    await this._save()
  }

  async _save() {
    this._saveTimer = null
    if (!this._dirty || !this._rolesFile) return
    this._dirty = false
    try {
      const data = {
        roles: Object.fromEntries(this._roles),
        prefs: Object.fromEntries(this._prefs),
        fallbackPasswordHash: this._fallbackPasswordHash,
        savedAt: new Date().toISOString(),
      }
      await mkdir(dirname(this._rolesFile), { recursive: true })
      await writeFile(this._rolesFile, JSON.stringify(data, null, 2), 'utf-8')
    } catch (err) {
      this._dirty = true
      console.warn('[uds-auth:RolesStore] Failed to save roles file:', err.message)
    }
    // Changes during await writeFile — schedule another save.
    if (this._dirty) this._markDirty()
  }

  // === 首次部署 bootstrap ===

  /**
   * 原子 check-and-set: 第一个登录的用户 = super_admin
   * 返回 { role, bootstrapped } bootstrapped=true 表示本次是 bootstrap
   */
  async bootstrapFirstUser(empNo) {
    // 用锁保证原子性
    this._firstBootLock = this._firstBootLock.then(async () => {
      if (this._roles.size === 0) {
        this._roles.set(empNo, ROLES.SUPER_ADMIN)
        this._markDirty()
        return { role: ROLES.SUPER_ADMIN, bootstrapped: true }
      }
      if (!this._roles.has(empNo)) {
        this._roles.set(empNo, ROLES.USER)
        this._markDirty()
        return { role: ROLES.USER, bootstrapped: false }
      }
      return { role: this._roles.get(empNo), bootstrapped: false }
    })
    return this._firstBootLock
  }

  // === 角色查询 ===

  getRole(empNo) {
    if (empNo === 'administrator') return ROLES.FALLBACK_ADMIN
    return this._roles.get(empNo) || ROLES.USER
  }

  /**
   * 个人偏好：admin 级默认开启查看全部；显式 false 才关闭。
   * user 不会走到这里（resolvePermissions 里 allowToggle=false）。
   */
  isViewAllSessionsEnabled(empNo) {
    if (!empNo) return false
    const prefs = this._prefs.get(String(empNo))
    if (prefs && Object.prototype.hasOwnProperty.call(prefs, 'viewAllSessions')) {
      return !!prefs.viewAllSessions
    }
    return true
  }

  /**
   * 设置「查看全部会话」偏好（调用方需校验 canToggleViewAllSessions）
   * @param {string} empNo
   * @param {boolean} enabled
   */
  setViewAllSessions(empNo, enabled) {
    const key = String(empNo || '').trim()
    if (!key) throw codedError('emp_no_required')
    const role = this.getRole(key)
    if (!canToggleViewAllSessions(role)) {
      throw codedError('forbidden_view_all_sessions')
    }
    const cur = { ...(this._prefs.get(key) || {}) }
    // Persist explicit true/false — deleting the key would fall back to default-on.
    cur.viewAllSessions = !!enabled
    this._prefs.set(key, cur)
    this._markDirty()
    return true
  }

  /** 角色 + 个人偏好 → 有效权限 */
  resolvePermissions(empNo, role) {
    const id = empNo != null ? String(empNo) : ''
    const r = role || this.getRole(id)
    const allowToggle = canToggleViewAllSessions(r)
    return computePermissions(r, {
      viewAllSessions: allowToggle && this.isViewAllSessionsEnabled(id),
    })
  }

  hasRole(empNo) {
    return this._roles.has(empNo)
  }

  getAll() {
    return Array.from(this._roles.entries()).map(([empNo, role]) => ({ empNo, role }))
  }

  /** 角色表是否为空（用于 bootstrap） */
  isEmpty() {
    return this._roles.size === 0
  }

  /**
   * 分页 + 工号模糊搜索（上千用户场景）
   * @param {{ page?: number, pageSize?: number, q?: string }} opts
   */
  listPage(opts = {}) {
    const page = Math.max(1, Number(opts.page) || 1)
    const pageSize = Math.min(200, Math.max(1, Number(opts.pageSize) || 50))
    const q = String(opts.q || '').trim().toLowerCase()

    let rows = Array.from(this._roles.entries()).map(([empNo, role]) => ({ empNo, role }))
    if (q) {
      rows = rows.filter((r) => String(r.empNo).toLowerCase().includes(q)
        || String(ROLE_LABELS[r.role] || r.role).toLowerCase().includes(q))
    }
    rows.sort((a, b) => String(a.empNo).localeCompare(String(b.empNo), 'zh'))
    const total = rows.length
    const start = (page - 1) * pageSize
    const users = rows.slice(start, start + pageSize).map(({ empNo, role }) => ({
      empNo,
      role,
      roleLabel: ROLE_LABELS[role] || role,
    }))
    return {
      users,
      total,
      page,
      pageSize,
      totalPages: Math.max(1, Math.ceil(total / pageSize)),
    }
  }

  async countByRole(role) {
    let n = 0
    for (const r of this._roles.values()) if (r === role) n++
    return n
  }

  // === 角色管理 (admin 级) ===

  /**
   * 设置用户角色
   * 保护性 invariant: 至少保留 1 个 super_admin 身份（若表中曾有）
   */
  async setRole(empNo, newRole, currentAdminRole) {
    if (!isAdminClass(currentAdminRole)) {
      throw codedError('forbidden_set_role')
    }

    // invariant: 不能让系统变成 0 个 super_admin（身份仍保留）
    const currentRole = this._roles.get(empNo)
    if (currentRole === ROLES.SUPER_ADMIN && newRole !== ROLES.SUPER_ADMIN) {
      const superAdmins = await this.countByRole(ROLES.SUPER_ADMIN)
      if (superAdmins <= 1) {
        throw codedError('last_super_admin_demote')
      }
    }

    this._roles.set(empNo, newRole)
    this._markDirty()
    return true
  }

  /** 删除用户 */
  async removeUser(empNo, currentAdminRole) {
    if (!isAdminClass(currentAdminRole)) {
      throw codedError('forbidden_remove_user')
    }
    const currentRole = this._roles.get(empNo)
    if (currentRole === ROLES.SUPER_ADMIN) {
      const superAdmins = await this.countByRole(ROLES.SUPER_ADMIN)
      if (superAdmins <= 1) {
        throw codedError('last_super_admin_delete')
      }
    }
    this._roles.delete(empNo)
    this._prefs.delete(empNo)
    this._markDirty()
    return true
  }

  /** 确保用户存在 (如果不存在设为 user) */
  ensureUser(empNo, currentAdminRole) {
    if (!isAdminClass(currentAdminRole)) {
      throw codedError('forbidden_add_user')
    }
    if (!this._roles.has(empNo)) {
      this._roles.set(empNo, ROLES.USER)
      this._markDirty()
    }
    return true
  }

  // === Fallback Administrator ===

  setFallbackPassword(password, currentAdminRole) {
    if (!isAdminClass(currentAdminRole)) {
      throw codedError('forbidden_set_fallback')
    }
    if (!password || password.length < 6) {
      throw codedError('password_too_short')
    }
    this._fallbackPasswordHash = hashPassword(password)
    this._markDirty()
    return true
  }

  clearFallbackPassword(currentAdminRole) {
    if (!isAdminClass(currentAdminRole)) {
      throw codedError('forbidden_clear_fallback')
    }
    this._fallbackPasswordHash = null
    this._markDirty()
    return true
  }

  isFallbackEnabled() {
    return this._fallbackPasswordHash !== null
  }

  /**
   * 验证 fallback 密码 + rate limit
   * @returns {boolean}
   */
  verifyFallback(password, ip) {
    if (!this._fallbackPasswordHash) return false
    const now = Date.now()

    // rate limit: 5 tries per minute per IP
    let bucket = this._fallbackRateLimit.get(ip)
    if (!bucket || now > bucket.resetAt) {
      bucket = { count: 0, resetAt: now + 60_000 }
      this._fallbackRateLimit.set(ip, bucket)
    }
    bucket.count++
    if (bucket.count > 5) {
      return false // rate limited
    }

    return hashPassword(password) === this._fallbackPasswordHash
  }
}