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

export const dynamic = 'force-dynamic'

/**
 * 判断IP是否为内网地址
 */
function isIntranetIP(ip: string): boolean {
  if (!ip) return false
  
  // 处理可能存在的端口号
  const cleanIP = ip.split(':')[0]
  
  // localhost
  if (cleanIP === '127.0.0.1' || cleanIP === 'localhost' || cleanIP === '::1') {
    return true
  }
  
  // IPv4 内网IP段判断
  const ipv4Regex = /^(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})$/
  const match = cleanIP.match(ipv4Regex)
  
  if (match) {
    const [, a, b, c, d] = match.map(Number)
    
    // 验证IP有效性
    if (a > 255 || b > 255 || c > 255 || d > 255) {
      return false
    }
    
    // 10.0.0.0 - 10.255.255.255 (Class A)
    if (a === 10) return true
    
    // 172.16.0.0 - 172.31.255.255 (Class B)
    if (a === 172 && b >= 16 && b <= 31) return true
    
    // 192.168.0.0 - 192.168.255.255 (Class C)
    if (a === 192 && b === 168) return true
    
    // 169.254.0.0 - 169.254.255.255 (Link-local)
    if (a === 169 && b === 254) return true
  }
  
  return false
}

/**
 * 获取客户端真实IP地址
 */
function getClientIP(request: NextRequest): string {
  // 优先级：x-real-ip > x-forwarded-for > connection
  const xRealIP = request.headers.get('x-real-ip')
  if (xRealIP) return xRealIP
  
  const xForwardedFor = request.headers.get('x-forwarded-for')
  if (xForwardedFor) {
    // x-forwarded-for 可能包含多个IP，取第一个（客户端真实IP）
    return xForwardedFor.split(',')[0].trim()
  }
  
  const cfConnectingIP = request.headers.get('cf-connecting-ip') // Cloudflare
  if (cfConnectingIP) return cfConnectingIP
  
  const trueClientIP = request.headers.get('true-client-ip') // Akamai
  if (trueClientIP) return trueClientIP
  
  // 如果都没有，返回默认值
  return 'unknown'
}

/**
 * GET /api/network-status
 * 返回用户的网络环境状态
 */
export async function GET(request: NextRequest) {
  try {
    const clientIP = getClientIP(request)
    const isIntranet = isIntranetIP(clientIP)
    
    // 获取当前访问的域名
    const hostname = request.headers.get('host') || ''
    const publicDomains = (process.env.PUBLIC_DOMAINS || '').split(',').map(s => s.trim()).filter(Boolean)
    const isPublicDomain = publicDomains.length > 0 ? publicDomains.includes(hostname) : false
    
    console.log(`[Network Status] IP: ${clientIP}, isIntranet: ${isIntranet}, hostname: ${hostname}`)
    
    return NextResponse.json({
      success: true,
      isIntranet,
      isPublicDomain,
      // 不返回完整IP地址（隐私保护）
      ipMasked: clientIP.split('.').slice(0, 2).join('.') + '.xxx.xxx',
      message: isIntranet 
        ? '检测到内网访问' 
        : '检测到公网访问',
      intranetUrl: isIntranet && isPublicDomain 
        ? (process.env.NEXT_PUBLIC_INTRANET_URL || '') 
        : null
    })
  } catch (error) {
    console.error('[Network Status] Error:', error)
    return NextResponse.json({
      success: false,
      error: '网络状态检测失败'
    }, { status: 500 })
  }
}