package scanner

import (
	"fmt"
	"net"
	"sync"
	"time"

	sshclient "network-topology-discovery/internal/ssh"
)

// Scanner 网络扫描器
type Scanner struct {
	concurrency int
	timeout     time.Duration
}

// NewScanner 创建扫描器
func NewScanner(concurrency int, timeout time.Duration) *Scanner {
	if concurrency <= 0 {
		concurrency = 10
	}
	if timeout == 0 {
		timeout = 2 * time.Second
	}
	return &Scanner{
		concurrency: concurrency,
		timeout:     timeout,
	}
}

// ScanRange 扫描IP范围
func (s *Scanner) ScanRange(cidr string) ([]string, error) {
	_, ipNet, err := net.ParseCIDR(cidr)
	if err != nil {
		return nil, fmt.Errorf("invalid CIDR: %w", err)
	}

	var ips []string
	for ip := ipNet.IP.Mask(ipNet.Mask); ipNet.Contains(ip); incIP(ip) {
		ips = append(ips, ip.String())
	}

	return ips, nil
}

// CheckHosts 检查主机是否存活
func (s *Scanner) CheckHosts(ips []string) []string {
	var aliveHosts []string
	var mu sync.Mutex
	var wg sync.WaitGroup

	semaphore := make(chan struct{}, s.concurrency)

	for _, ip := range ips {
		wg.Add(1)
		semaphore <- struct{}{}

		go func(ip string) {
			defer wg.Done()
			defer func() { <-semaphore }()

			if sshclient.Ping(ip, s.timeout) {
				mu.Lock()
				aliveHosts = append(aliveHosts, ip)
				mu.Unlock()
			}
		}(ip)
	}

	wg.Wait()
	return aliveHosts
}

// CheckSSHHosts 检查哪些主机开启了SSH
func (s *Scanner) CheckSSHHosts(ips []string, port int) []string {
	var sshHosts []string
	var mu sync.Mutex
	var wg sync.WaitGroup

	semaphore := make(chan struct{}, s.concurrency)

	for _, ip := range ips {
		wg.Add(1)
		semaphore <- struct{}{}

		go func(ip string) {
			defer wg.Done()
			defer func() { <-semaphore }()

			if sshclient.CheckSSH(ip, port, s.timeout) {
				mu.Lock()
				sshHosts = append(sshHosts, ip)
				mu.Unlock()
			}
		}(ip)
	}

	wg.Wait()
	return sshHosts
}

// ScanAndDiscover 扫描并发现设备
func (s *Scanner) ScanAndDiscover(cidr string, sshPort int) ([]string, error) {
	// 解析IP范围
	ips, err := s.ScanRange(cidr)
	if err != nil {
		return nil, err
	}

	// 检查存活主机
	aliveHosts := s.CheckHosts(ips)

	// 检查SSH
	sshHosts := s.CheckSSHHosts(aliveHosts, sshPort)

	return sshHosts, nil
}

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