package Plugins

import (
	"fmt"
	"github.com/gosnmp/gosnmp"
	"github.com/shadow1ng/fscan/Common"
	"strconv"
	"strings"
	"time"
)

// SNMPScan 执行SNMP服务扫描
func SNMPScan(info *Common.HostInfo) (tmperr error) {
	if Common.DisableBrute {
		return
	}

	maxRetries := Common.MaxRetries
	portNum, _ := strconv.Atoi(info.Ports)
	defaultCommunities := []string{"public", "private", "cisco", "community"}
	timeout := time.Duration(Common.Timeout) * time.Second

	Common.LogDebug(fmt.Sprintf("开始扫描 %v:%v", info.Host, info.Ports))
	Common.LogDebug(fmt.Sprintf("尝试默认 community 列表 (总数: %d)", len(defaultCommunities)))

	tried := 0
	total := len(defaultCommunities)

	// 遍历所有 community
	for _, community := range defaultCommunities {
		tried++
		Common.LogDebug(fmt.Sprintf("[%d/%d] 尝试 community: %s", tried, total, community))

		// 重试循环
		for retryCount := 0; retryCount < maxRetries; retryCount++ {
			if retryCount > 0 {
				Common.LogDebug(fmt.Sprintf("第%d次重试: community: %s", retryCount+1, community))
			}

			// 执行SNMP连接
			done := make(chan struct {
				success bool
				err     error
			}, 1)

			go func(community string) {
				success, err := SNMPConnect(info, community, portNum)
				select {
				case done <- struct {
					success bool
					err     error
				}{success, err}:
				default:
				}
			}(community)

			// 等待结果或超时
			var err error
			select {
			case result := <-done:
				err = result.err
				if result.success && err == nil {
					// 连接成功
					successLog := fmt.Sprintf("SNMP服务 %v:%v community: %v 连接成功",
						info.Host, info.Ports, community)
					Common.LogSuccess(successLog)
					return nil
				}
			case <-time.After(timeout):
				err = fmt.Errorf("连接超时")
			}

			// 处理错误情况
			if err != nil {
				errlog := fmt.Sprintf("SNMP服务 %v:%v 尝试失败 community: %v 错误: %v",
					info.Host, info.Ports, community, err)
				Common.LogError(errlog)

				// 检查是否需要重试
				if retryErr := Common.CheckErrs(err); retryErr != nil {
					if retryCount == maxRetries-1 {
						continue
					}
					continue // 继续重试
				}
			}

			break // 如果不需要重试，跳出重试循环
		}
	}

	Common.LogDebug(fmt.Sprintf("扫描完成，共尝试 %d 个 community", tried))
	return tmperr
}

// SNMPConnect 尝试SNMP连接
func SNMPConnect(info *Common.HostInfo, community string, portNum int) (bool, error) {
	host := info.Host
	timeout := time.Duration(Common.Timeout) * time.Second

	snmp := &gosnmp.GoSNMP{
		Target:    host,
		Port:      uint16(portNum),
		Community: community,
		Version:   gosnmp.Version2c,
		Timeout:   timeout,
		Retries:   1,
	}

	err := snmp.Connect()
	if err != nil {
		return false, err
	}
	defer snmp.Conn.Close()

	oids := []string{"1.3.6.1.2.1.1.1.0"}
	result, err := snmp.Get(oids)
	if err != nil {
		return false, err
	}

	if len(result.Variables) > 0 {
		success := fmt.Sprintf("SNMP服务 %v:%v community: %v",
			host, portNum, community) // 使用portNum替换port

		if result.Variables[0].Type != gosnmp.NoSuchObject {
			sysDesc := strings.TrimSpace(string(result.Variables[0].Value.([]byte)))
			success += fmt.Sprintf(" System: %v", sysDesc)
		}

		Common.LogSuccess(success)
		return true, nil
	}

	return false, fmt.Errorf("认证失败")
}