package discovery

import (
	"fmt"
	"net"
	"os/exec"
	"runtime"
	"time"

	"auto-check/pkg/model"
)

// Scanner 网段扫描器（串行，按顺序逐个探测）
type Scanner struct {
	CIDR    string
	Timeout time.Duration
}

// NewScanner 创建扫描器
func NewScanner(cidr string, timeout time.Duration) *Scanner {
	return &Scanner{
		CIDR:    cidr,
		Timeout: timeout,
	}
}

// Scan 扫描网段，返回存活设备列表（含 MAC 地址）
// 串行逐个探测，每个 IP 有超时保护
func (s *Scanner) Scan() []model.Device {
	ips, ok := s.candidateIPs()
	if !ok {
		return nil
	}
	fmt.Printf("[扫描] 网段 %s，共 %d 个IP，开始探测...\n", s.CIDR, len(ips))

	var results []model.Device
	for _, ip := range ips {
		if dev, ok := s.probe(ip); ok {
			results = append(results, dev)
		}
	}

	fmt.Printf("[扫描] 完成，发现 %d 台存活设备\n", len(results))
	return results
}

// candidateIPs 解析网段并生成候选 IP 列表（排除网络地址和广播地址）
func (s *Scanner) candidateIPs() ([]net.IP, bool) {
	ip, ipnet, err := net.ParseCIDR(s.CIDR)
	if err != nil {
		fmt.Printf("[扫描] 网段解析失败: %v\n", err)
		return nil, false
	}
	var ips []net.IP
	for ip := ip.Mask(ipnet.Mask); ipnet.Contains(ip); inc(ip) {
		dst := make(net.IP, len(ip))
		copy(dst, ip)
		ips = append(ips, dst)
	}
	if len(ips) > 2 {
		ips = ips[1 : len(ips)-1]
	}
	return ips, true
}

// probe 探测单个 IP，存活则返回设备信息（MAC 通过 ARP 表查询）
func (s *Scanner) probe(ip net.IP) (model.Device, bool) {
	if !s.isAlive(ip) {
		return model.Device{}, false
	}
	mac := lookupMAC(ip.String())
	desc := "无MAC"
	if mac != "" {
		desc = mac
	}
	fmt.Printf("  [+] %s 存活 (MAC: %s)\n", ip, desc)
	return model.Device{IP: ip.String(), MAC: mac}, true
}

// isAlive 用 ping 探测单个 IP 是否存活（内置超时保护）
func (s *Scanner) isAlive(ip net.IP) bool {
	waitMs := s.Timeout.Milliseconds()
	if waitMs < 1000 {
		waitMs = 1000
	}
	var args []string
	switch runtime.GOOS {
	case "windows":
		args = []string{"-n", "1", "-w", fmt.Sprintf("%d", waitMs), ip.String()}
	case "darwin":
		args = []string{"-c", "1", "-W", fmt.Sprintf("%d", waitMs), ip.String()}
	default:
		args = []string{"-c", "1", "-W", fmt.Sprintf("%d", waitMs/1000), ip.String()}
	}
	return exec.Command("ping", args...).Run() == nil
}

// inc IP 递增
func inc(ip net.IP) {
	for j := len(ip) - 1; j >= 0; j-- {
		ip[j]++
		if ip[j] > 0 {
			break
		}
	}
}