// shared/lib/auth/middleware-v2.ts — V2 middleware 工厂（步骤 1a 新增，旧 middleware.ts 不动）
// 与 V1 的关键差异：单 cookie 模型、Edge 验签+iss 校验、无 admin 路径检查（鉴权下沉到 layout/API）
import { NextResponse, type NextRequest } from 'next/server'
import { verifyJwtEdge } from './jwt-edge'
import type { MiddlewareV2Config } from './types-v2'

// Edge Runtime 兼容的 JWT payload 解码（不验签）
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): NextResponse {
  response.headers.set('Cache-Control', 'no-cache, no-store, must-revalidate')
  return response
}

/** 创建 V2 middleware（单 cookie 模型，Edge 验签） */
export function createMiddlewareV2(cfg: MiddlewareV2Config) {
  const publicPaths = cfg.publicPaths || ['/login', '/api/auth', '/api/health', '/_next', '/favicon.ico']
  const allowedIssuers = cfg.allowedIssuers
  const enableApiKey = cfg.enableApiKey || false

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

    // 1. 公开路径放行
    if (publicPaths.some(p => pathname.startsWith(p))) {
      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.nextUrl.origin))
        }
      }
      return NextResponse.next()
    }

    // 2. API Key 认证（可选，迁移期间保留）
    if (enableApiKey) {
      const authHeader = request.headers.get('authorization')
      if (authHeader?.startsWith('Bearer ak_')) {
        const key = authHeader.slice(7)
        const allowedKeys = process.env.ALLOWED_API_KEYS || ''
        if (allowedKeys && allowedKeys.split(',').map(k => k.trim()).includes(key)) {
          return NextResponse.next()
        }
        if (pathname.startsWith('/api/')) {
          return NextResponse.json({ error: '无效的 API Key' }, { status: 401 })
        }
      }
    }

    // 3. 验证 tlyq_session
    const token = request.cookies.get('tlyq_session')?.value
    if (!token) {
      if (pathname.startsWith('/api/')) {
        return NextResponse.json({ error: '未登录' }, { status: 401 })
      }
      return noCache(NextResponse.redirect(new URL('/login', request.nextUrl.origin)))
    }

    // 4. 提取 iss → 验签（Edge Runtime）
    const payload = decodeJwtPayload(token)
    if (!payload || !isValidPayload(payload)) {
      if (pathname.startsWith('/api/')) {
        return NextResponse.json({ error: '登录已过期' }, { status: 401 })
      }
      const loginUrl = new URL('/login', request.nextUrl.origin)
      const response = NextResponse.redirect(loginUrl)
      response.cookies.delete('tlyq_session')
      return response
    }

    const iss = payload.iss as string | undefined

    // allowedIssuers 白名单校验（"*" 跳过，全量迁移后改为具体值）
    if (allowedIssuers.length === 1 && allowedIssuers[0] === '*') {
      // 迁移模式：跳过白名单校验，仅验签名+过期
    } else if (!iss || !allowedIssuers.includes(iss)) {
      if (pathname.startsWith('/api/')) {
        return NextResponse.json({ error: '无效的签发来源' }, { status: 401 })
      }
      return noCache(NextResponse.redirect(new URL('/login', request.nextUrl.origin)))
    }

    // 5. 验签（使用提取出的 iss 进行自引用校验）
    // 迁移模式（allowedIssuers = ["*"]）：跳过 iss 校验，仅验签名+过期
    // 全量迁移后（allowedIssuers 为具体白名单）：强制 iss 校验
    const jwtSecret = cfg.jwtSecret
    const isMigrationMode = allowedIssuers.length === 1 && allowedIssuers[0] === '*'
    const expectedIss = isMigrationMode ? (iss || '*') : (iss || '')
    const verified = await verifyJwtEdge(token, jwtSecret, expectedIss)

    if (!verified) {
      if (pathname.startsWith('/api/')) {
        return NextResponse.json({ error: '登录已过期' }, { status: 401 })
      }
      const loginUrl = new URL('/login', request.nextUrl.origin)
      const response = NextResponse.redirect(loginUrl)
      response.cookies.delete('tlyq_session')
      return response
    }

    // 6. 放行（设置 session cookie 供客户端展示用，httpOnly:false，仅含 username）
    const response = noCache(NextResponse.next())
    response.cookies.set('session', JSON.stringify({ username: verified.username }), {
      httpOnly: false,
      secure: process.env.NODE_ENV === 'production',
      sameSite: 'lax' as const,
      path: '/',
    })
    return response
  }
}