import { NextResponse } from 'next/server'
import type { NextRequest } from 'next/server'

function decodeJwtPayload(token: string): Record<string, unknown> | null {
  try {
    const parts = token.split('.')
    if (parts.length !== 3) return null
    let payload = parts[1].replace(/-/g, '+').replace(/_/g, '/')
    while (payload.length % 4) payload += '='
    return JSON.parse(atob(payload))
  } catch { return null }
}

function isValidPayload(payload: Record<string, unknown> | null): boolean {
  if (!payload) return false
  return !(payload.exp && (payload.exp as number) < Math.floor(Date.now() / 1000))
}

function noCache(response: NextResponse) {
  response.headers.set('Cache-Control', 'no-cache, no-store, must-revalidate')
  return response
}

export function middleware(request: NextRequest) {
  const { pathname } = request.nextUrl

  // 登录页：已登录用户自动跳转首页
  if (pathname === '/login') {
    const token = request.cookies.get('tlyq_session')?.value
    const payload = token ? decodeJwtPayload(token) : null
    if (isValidPayload(payload)) {
      return NextResponse.redirect(new URL('/', request.url))
    }
    return NextResponse.next()
  }

  // 设置密码/API 路径放行（API 路由自行验证）
  if (pathname === '/setup-password' || pathname.startsWith('/api/auth/') || pathname.startsWith('/api/admin/')) {
    return NextResponse.next()
  }
  // /admin 管理页面需要认证
  if (pathname.startsWith('/admin')) {
    const token = request.cookies.get('tlyq_session')?.value
    const payload = token ? decodeJwtPayload(token) : null
    if (!isValidPayload(payload)) {
      return NextResponse.redirect(new URL('/login', request.url))
    }
    return noCache(NextResponse.next())
  }

  // 静态资源放行（已有路径哈希，允许缓存）
  if (pathname.startsWith('/_next/') || pathname === '/favicon.ico') {
    return NextResponse.next()
  }

  const token = request.cookies.get('tlyq_session')?.value
  const payload = token ? decodeJwtPayload(token) : null

  if (isValidPayload(payload)) {
    const response = NextResponse.next()
    response.cookies.set('session', JSON.stringify({ username: payload!.username }), {
      httpOnly: true,
      sameSite: 'lax',
      path: '/',
    })
    return noCache(response)
  }

  return noCache(NextResponse.redirect(new URL('/login', request.url)))
}

export const config = { matcher: ['/((?!_next/static|_next/image|favicon.ico|public).*)'] }