// 身份认证：账号与密码哈希只保存在服务器（PBKDF2）
// 本机仅保存"会话标识"与自动登录凭据（localStorage），用于免重复登录
// 业务数据一律在服务器，本机数据库只是缓存（由同步引擎全量刷新）
import { bindDatabase, db, unbindDatabase, WorklogDB } from './schema'
import { lockVault } from './vault'
import { getSyncBase } from '../lib/server'

const LEGACY_DB_NAME = 'intern_worklog'
const SESSION_KEY = 'dsh_session_user'

export interface Session {
  userId: string
  username: string
}

// ---------- 本地会话与凭据 ----------

export function getSession(): Session | null {
  try {
    const raw = localStorage.getItem(SESSION_KEY)
    if (!raw) return null
    const s = JSON.parse(raw)
    if (s && s.userId && s.username) return s as Session
  } catch { /* 忽略损坏会话 */ }
  return null
}

function setSession(s: Session): void {
  localStorage.setItem(SESSION_KEY, JSON.stringify(s))
}

function clearSession(): void {
  localStorage.removeItem(SESSION_KEY)
}

// 云端凭据：同用户名同密码，用于应用启动时免输密码的自动登录
const CREDS_KEY = 'dsh_cloud_creds'
export function setCloudCreds(username: string, password: string): void {
  localStorage.setItem(CREDS_KEY, JSON.stringify({ username, password }))
}
export function getCloudCreds(): { username: string; password: string } | null {
  try {
    const raw = localStorage.getItem(CREDS_KEY)
    if (!raw) return null
    const c = JSON.parse(raw)
    if (c && c.username && c.password) return c as { username: string; password: string }
  } catch { /* 忽略损坏数据 */ }
  return null
}
export function clearCloudCreds(): void {
  localStorage.removeItem(CREDS_KEY)
}

// ---------- 用户数据库（本地缓存实例） ----------

let openedFor: string | null = null

export function openUserDatabase(userId: string): void {
  if (openedFor === userId && db) return
  if (db) unbindDatabase()
  bindDatabase(new WorklogDB(LEGACY_DB_NAME + '_' + userId))
  openedFor = userId
}

// ---------- 登录 / 注册（全部经由服务器） ----------

async function serverAuth(path: 'login' | 'register', username: string, password: string): Promise<{ userId: string; username: string }> {
  const base = await getSyncBase()
  let resp: Response
  try {
    resp = await fetch(base + '/api/auth/' + path, {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ username: username.trim(), password })
    })
  } catch {
    throw new Error('无法连接同步服务器：请检查网络后重试')
  }
  const j = await resp.json().catch(() => ({}))
  if (!resp.ok) {
    const msg = (j && j.error) || ('服务返回 ' + resp.status)
    if (path === 'register' && resp.status === 409) throw new Error('云端已有同名账号且密码一致，直接登录即可')
    throw new Error(String(msg))
  }
  if (!j.userId || !j.username) throw new Error('登录响应异常')
  return { userId: String(j.userId), username: String(j.username) }
}

async function establishSession(username: string, password: string, path: 'login' | 'register'): Promise<Session> {
  const info = await serverAuth(path, username, password)
  openUserDatabase(info.userId)
  const session: Session = { userId: info.userId, username: info.username }
  setSession(session)
  setCloudCreds(info.username, password)
  return session
}

export async function login(username: string, password: string): Promise<Session> {
  const name = (username || '').trim()
  if (!name || !password) throw new Error('请输入用户名与密码')
  return establishSession(name, password, 'login')
}

export interface RegisterOptions { migrateLegacy?: boolean }

export async function createUser(username: string, password: string): Promise<Session>
export async function createUser(username: string, password: string, migrateLegacy: boolean): Promise<Session>
export async function createUser(username: string, password: string, _migrateLegacy?: boolean): Promise<Session> {
  const name = (username || '').trim()
  if (name.length < 2 || name.length > 20) throw new Error('用户名需 2 到 20 个字符')
  if (password.length < 6) throw new Error('登录密码至少 6 位')
  return establishSession(name, password, 'register')
}

// 启动引导：已保存过凭据则静默登录，直接进入应用
export async function bootstrapSession(): Promise<Session | null> {
  const creds = getCloudCreds()
  if (!creds) return null
  try {
    return await establishSession(creds.username, creds.password, 'login')
  } catch {
    return null
  }
}

export async function logoutUser(): Promise<void> {
  lockVault()
  unbindDatabase()
  openedFor = null
  // 保留云端凭据：退出登录后再次打开仍可一键重新进入；如需彻底退出请删除用户
  clearSession()
}

export function forgetDevice(): void {
  lockVault()
  unbindDatabase()
  openedFor = null
  clearSession()
  clearCloudCreds()
}

export async function changeLoginPassword(oldPwd: string, newPwd: string): Promise<void> {
  const s = getSession()
  if (!s) throw new Error('未登录')
  if (newPwd.length < 6) throw new Error('新密码至少 6 位')
  const creds = getCloudCreds()
  if (!creds || creds.password !== oldPwd) throw new Error('旧密码不正确')
  const base = await getSyncBase()
  let resp: Response
  try {
    resp = await fetch(base + '/api/auth/password', {
      method: 'POST',
      headers: { 'Content-Type': 'application/json', Authorization: 'Bearer ' + getCachedToken() },
      body: JSON.stringify({ oldPassword: oldPwd, newPassword: newPwd })
    })
  } catch {
    throw new Error('无法连接同步服务器')
  }
  if (!resp.ok) {
    const j = await resp.json().catch(() => ({}))
    throw new Error((j && j.error) || ('修改失败 ' + resp.status))
  }
  setCloudCreds(creds.username, newPwd)
}

export async function deleteCurrentUser(): Promise<void> {
  const s = getSession()
  if (!s) throw new Error('未登录')
  const base = await getSyncBase()
  let resp: Response
  try {
    resp = await fetch(base + '/api/auth/delete', {
      method: 'POST',
      headers: { Authorization: 'Bearer ' + getCachedToken() }
    })
  } catch {
    throw new Error('无法连接同步服务器')
  }
  if (!resp.ok) {
    const j = await resp.json().catch(() => ({}))
    throw new Error((j && j.error) || ('删除失败 ' + resp.status))
  }
  forgetDevice()
}

// 令牌由同步引擎负责登录换取/续期；此处读取共享的本地令牌副本
import { getToken } from '../lib/server'
function getCachedToken(): string {
  return getToken()
}

// 兼容旧导出：纯在线模式下不再存在本机旧数据迁移（账号与数据都在服务器）
export async function legacyDataExists(): Promise<boolean> {
  void LEGACY_DB_NAME
  return false
}