package main

import (
	"flag"
	"fmt"
	"github.com/gosnmp/gosnmp"
	"log"
	"os"
	"reflect"
	"strconv"
	"time"
)

var (
	oid      string
	oidValue string
)

func main() {
	version := flag.Int("v", 2, "SNMP version")
	community := flag.String("c", "pulic", "SNMP community")
	host := flag.String("h", "127.0.0.1", "SNMP server host")
	port := flag.Uint("p", 161, "SNMP server port")
	oidstr := flag.String("o", ".1.3.6.1.2.1.1.3.0", "SNMP oid")
	oidval := flag.String("s", "", "SNMP set value")
	flag.Parse()

	oid = *oidstr
	oidValue = *oidval

	if oidValue != "" {
		rping(*host, uint16(*port), *community)
	} else {
		switch *version {
		case 1:
			getV1(*host, uint16(*port), *community)
		case 3:
			getV3(*host, uint16(*port), *community)
		default:
			getV2c(*host, uint16(*port), *community)
		}
	}
}

func getV2c(target string, port uint16, community string) {
	gosnmp.Default.Target = target
	gosnmp.Default.Port = port
	gosnmp.Default.Version = gosnmp.Version2c
	gosnmp.Default.Community = community

	if err := gosnmp.Default.Connect(); err != nil {
		log.Fatal(err)
	}

	all, err := gosnmp.Default.WalkAll(".1.3.6.1.2.1.2.2.1")
	if err != nil {
		log.Fatal(err)
	}
	for _, r := range all {
		fmt.Println("Walk:", r.Name, r.Value, reflect.TypeOf(r.Value), r.Type)
	}

	res, err := gosnmp.Default.Get([]string{oid})
	if err != nil {
		log.Fatal(err)
	}

	for i, v := range res.Variables {
		num := strconv.Itoa(i + 1)
		fmt.Println("snmpOid" + num, v.Name)
		fmt.Println("snmpResult" + num, v.Value)
	}
}

func getV1(target string, port uint16, community string) {
	gosnmp.Default.Target = target
	gosnmp.Default.Port = port
	gosnmp.Default.Version = gosnmp.Version1
	gosnmp.Default.Community = community

	if err := gosnmp.Default.Connect(); err != nil {
		log.Fatal(err)
	}

	res, err := gosnmp.Default.Get([]string{oid})
	if err != nil {
		log.Fatal(err)
	}

	for i, v := range res.Variables {
		num := strconv.Itoa(i + 1)
		fmt.Println("snmpResult" + num, v.Value)
		fmt.Println("snmpOid" + num, v.Name)
	}
}

func getV3(target string, port uint16, community string) {
	// Default is a pointer to a GoSNMP struct that contains sensible defaults
	// eg port 161, community public, etc

	params := &gosnmp.GoSNMP{
		Target:        target,
		Port:          port,
		Version:       gosnmp.Version3,
		Community:     community,
		Timeout:       time.Duration(30) * time.Second,
		SecurityModel: gosnmp.UserSecurityModel,
		MsgFlags:      gosnmp.AuthPriv,
		Logger:        log.New(os.Stdout, "", 0),
		SecurityParameters: &gosnmp.UsmSecurityParameters{
			UserName:                 "user",
			AuthoritativeEngineID:    "1234",
			AuthenticationProtocol:   gosnmp.SHA,
			AuthenticationPassphrase: "password",
			PrivacyProtocol:          gosnmp.DES,
			PrivacyPassphrase:        "password",
		},
	}

	if err := params.Connect(); err != nil {
		log.Fatal(err)
	}

	res, err := params.Get([]string{oid})
	if err != nil {
		log.Fatal(err)
	}

	for i, v := range res.Variables {
		num := strconv.Itoa(i + 1)
		fmt.Println("snmpResult" + num, v.Value)
		fmt.Println("snmpOid" + num, v.Name)
	}
}

func rping(target string, port uint16, community string) {
	gosnmp.Default.Target = target
	gosnmp.Default.Port = port
	gosnmp.Default.Version = gosnmp.Version2c
	gosnmp.Default.Community = community

	if err := gosnmp.Default.Connect(); err != nil {
		log.Fatal(err)
	}

	// test oid: .1.3.6.1.2.1.1.5.0
	res, err := gosnmp.Default.Set([]gosnmp.SnmpPDU{
		{
			Name: oid,
			Type: gosnmp.OctetString,
			Value: oidValue,
		},
	})
	if err != nil {
		log.Fatal(err)
	}
	log.Println(res.Error)

	for _, v := range res.Variables {
		var val interface{}
		switch v.Type {
		case gosnmp.OctetString:
			val = string(v.Value.([]byte))
		case gosnmp.TimeTicks:
			a := gosnmp.ToBigInt(v.Value)
			val = fmt.Sprintf("%d", (*a).Int64())
		case gosnmp.ObjectIdentifier:
			val = v.Value
		default:
			val = v.Value
		}
		fmt.Println("Oid:", v.Name)
		fmt.Println("Type:", v.Type.String())
		fmt.Println("Val:", val)
	}
}

/*
SNMP System Group：

sysDescr 1.3.6.1.2.1.1.1
sysObjectID 1.3.6.1.2.1.1.2
sysUpTime 1.3.6.1.2.1.1.3
sysContact 1.3.6.1.2.1.1.4
sysName 1.3.6.1.2.1.1.5
sysLocation 1.3.6.1.2.1.1.6
sysServices 1.3.6.1.2.1.1.7
 */