package scans

import (
	"encoding/hex"
	"fmt"
	"log"
	"net"
	"net/netip"
	"os"
	"os/exec"
	"runtime"
	"sort"
	"strconv"
	"strings"
	"sync"
	"time"
	"unicode/utf8"

	"github.com/gosnmp/gosnmp"
)

type Runner struct {
	store Store
	cfg   RunnerConfig
}

type RunnerConfig struct {
	SNMPEnabled   bool
	SNMPCommunity string
}

func NewRunner(store Store, cfg RunnerConfig) *Runner {
	return &Runner{store: store, cfg: cfg}
}

func (r *Runner) Start(job ScanJob) {
	go r.run(job)
}

func (r *Runner) run(job ScanJob) {
	started := time.Now().UTC()
	_, _ = r.store.UpdateScan(job.ID, ScanUpdate{
		Status:    "running",
		Progress:  0,
		Stats:     ScanStats{},
		StartedAt: &started,
	})

	ips, err := expandTargets(job.CIDRs, job.ExcludeIPs)
	if err != nil {
		finished := time.Now().UTC()
		_, _ = r.store.UpdateScan(job.ID, ScanUpdate{
			Status:     "failed",
			Progress:   100,
			Stats:      ScanStats{},
			FinishedAt: &finished,
		})
		return
	}

	total := len(ips)
	if total == 0 {
		finished := time.Now().UTC()
		_, _ = r.store.UpdateScan(job.ID, ScanUpdate{
			Status:     "done",
			Progress:   100,
			Stats:      ScanStats{HostsTotal: 0, HostsUp: 0},
			FinishedAt: &finished,
		})
		return
	}

	maxWorkers := job.Options.MaxParallelHosts
	if maxWorkers <= 0 {
		maxWorkers = 64
	}

	var mu sync.Mutex
	var done int
	var up int
	workCh := make(chan string)
	wg := sync.WaitGroup{}

	worker := func() {
		defer wg.Done()
		for ip := range workCh {
			isUp := probeHost(ip, job.Options.PingTimeoutMS)
			checkedAt := time.Now().UTC()
			_ = r.store.SaveHostResult(job.ID, HostResult{
				IP:        ip,
				IsUp:      isUp,
				CheckedAt: checkedAt,
			})
			if isUp && job.Options.PortScanEnabled {
				for _, p := range job.Options.Ports {
					_ = r.store.SaveOpenPortResult(job.ID, OpenPortResult{
						IP:        ip,
						Port:      p,
						IsOpen:    probeTCPPort(ip, p, job.Options.PingTimeoutMS),
						CheckedAt: checkedAt,
					})
				}
			}
			if isUp && r.cfg.SNMPEnabled {
				snmpRes, lldpRes, ifRes, portDevRes := probeSNMPAndLLDP(ip, r.cfg.SNMPCommunity, checkedAt, job.Options.PingTimeoutMS)
				_ = r.store.SaveSNMPResult(job.ID, snmpRes)
				for _, lr := range lldpRes {
					if err := r.store.SaveLLDPResult(job.ID, lr); err != nil {
						log.Printf("scan %s: save LLDP для %s: %v", job.ID, lr.IP, err)
					}
				}
				for _, iface := range ifRes {
					if err := r.store.SaveInterfaceResult(job.ID, iface); err != nil {
						log.Printf("scan %s: save interface %s ifIndex=%d: %v", job.ID, iface.IP, iface.IfIndex, err)
					}
				}
				for _, pd := range portDevRes {
					if err := r.store.SavePortDeviceResult(job.ID, pd); err != nil {
						log.Printf("scan %s: save port-device %s ifIndex=%d mac=%s: %v", job.ID, pd.IP, pd.IfIndex, pd.MAC, err)
					}
				}
			}

			mu.Lock()
			done++
			if isUp {
				up++
			}
			progress := done * 100 / total
			stats := ScanStats{HostsTotal: total, HostsUp: up}
			mu.Unlock()

			_, _ = r.store.UpdateScan(job.ID, ScanUpdate{
				Status:   "running",
				Progress: progress,
				Stats:    stats,
			})
		}
	}

	for i := 0; i < maxWorkers; i++ {
		wg.Add(1)
		go worker()
	}

	for _, ip := range ips {
		workCh <- ip
	}
	close(workCh)
	wg.Wait()

	finished := time.Now().UTC()
	_, _ = r.store.UpdateScan(job.ID, ScanUpdate{
		Status:     "done",
		Progress:   100,
		Stats:      ScanStats{HostsTotal: total, HostsUp: up},
		FinishedAt: &finished,
	})
}

func probeSNMPAndLLDP(ip, community string, checkedAt time.Time, timeoutMS int) (SNMPResult, []LLDPResult, []InterfaceResult, []PortDeviceResult) {
	if timeoutMS <= 0 {
		timeoutMS = 700
	}
	if community == "" {
		community = "public"
	}

	client := &gosnmp.GoSNMP{
		Target:    ip,
		Port:      161,
		Version:   gosnmp.Version2c,
		Community: community,
		Timeout:   time.Duration(timeoutMS) * time.Millisecond,
		Retries:   1,
	}
	if err := client.Connect(); err != nil {
		return SNMPResult{IP: ip, Success: false, Error: err.Error(), CheckedAt: checkedAt}, nil, nil, nil
	}
	defer client.Conn.Close()

	oids := []string{
		".1.3.6.1.2.1.1.5.0",
		".1.3.6.1.2.1.1.1.0",
		".1.3.6.1.2.1.1.2.0",
	}
	pkt, err := client.Get(oids)
	if err != nil {
		return SNMPResult{IP: ip, Success: false, Error: err.Error(), CheckedAt: checkedAt}, nil, nil, nil
	}

	out := SNMPResult{IP: ip, Success: true, CheckedAt: checkedAt}
	for _, vb := range pkt.Variables {
		// Имена OID в ответах gosnmp всегда с ведущей «.», но сравниваем по нормализованной форме.
		switch snmpOIDTrim(vb.Name) {
		case "1.3.6.1.2.1.1.5.0":
			out.SysName = snmpValueToString(vb.Value)
		case "1.3.6.1.2.1.1.1.0":
			out.SysDescr = snmpValueToString(vb.Value)
		case "1.3.6.1.2.1.1.2.0":
			out.SysObjectID = snmpValueToString(vb.Value)
		}
	}

	// LLDP — несколько BulkWalk подряд; часть прошивок (в т.ч. Ubiquiti EdgeSwitch) отваливается по таймауту
	// или некорректно обрабатывает GET-BULK с большим MaxRepetitions — увеличиваем время и снижаем пакет,
	// при ошибке BulkWalk в walkAsMap делаем запасной SNMP Walk (GetNext).
	if min := time.Duration(3000) * time.Millisecond; client.Timeout < min {
		client.Timeout = min
	}
	client.MaxRepetitions = 12
	client.Retries = 2

	lldpRes := probeLLDP(client, ip, checkedAt)
	var ifList []InterfaceResult
	var portDevices []PortDeviceResult
	if out.Success {
		ifList = probeIfTable(client, ip, checkedAt)
		portDevices = probePortDevices(client, ip, checkedAt)
	}
	return out, lldpRes, ifList, portDevices
}

// probePortDevices собирает MAC-адреса за портами (BRIDGE-MIB) и пытается сопоставить им IP через ARP (ipNetToMedia).
func probePortDevices(client *gosnmp.GoSNMP, ip string, checkedAt time.Time) []PortDeviceResult {
	// dot1dBasePortIfIndex: bridge-port -> ifIndex
	basePortIfIndex := walkAsMap(client, ".1.3.6.1.2.1.17.1.4.1.2")
	// dot1dTpFdbPort: mac(6 octets) -> bridge-port
	fdbMacToBridgePort := walkAsMap(client, ".1.3.6.1.2.1.17.4.3.1.2")
	// dot1qTpFdbPort (Q-BRIDGE-MIB): vlan + mac(6 octets) -> bridge-port
	qFdbMacToBridgePort := walkAsMap(client, ".1.3.6.1.2.1.17.7.1.2.2.1.2")
	// ipNetToMediaPhysAddress: ifIndex.ip -> mac
	arpIfIPToMac := walkAsMap(client, ".1.3.6.1.2.1.4.22.1.2")

	if len(basePortIfIndex) == 0 || (len(fdbMacToBridgePort) == 0 && len(qFdbMacToBridgePort) == 0) {
		return nil
	}
	combinedFdb := make(map[string]string, len(fdbMacToBridgePort)+len(qFdbMacToBridgePort))
	for k, v := range fdbMacToBridgePort {
		combinedFdb[k] = v
	}
	for k, v := range qFdbMacToBridgePort {
		combinedFdb[k] = v
	}

	macToIPs := make(map[string]map[string]struct{})
	for key, mac := range arpIfIPToMac {
		mac = normalizeMACKey(mac)
		if mac == "" {
			continue
		}
		parts := strings.Split(key, ".")
		if len(parts) < 5 {
			continue
		}
		ipStr := strings.Join(parts[1:], ".")
		if net.ParseIP(ipStr) == nil {
			continue
		}
		if _, ok := macToIPs[mac]; !ok {
			macToIPs[mac] = make(map[string]struct{})
		}
		macToIPs[mac][ipStr] = struct{}{}
	}

	seen := make(map[string]struct{})
	out := make([]PortDeviceResult, 0, len(combinedFdb))
	for macTail, bridgePortRaw := range combinedFdb {
		mac := normalizeMACKey(dottedDecimalToMACTail(macTail))
		if mac == "" {
			continue
		}
		bridgePort, err := strconv.Atoi(strings.TrimSpace(snmpNumericString(bridgePortRaw)))
		if err != nil || bridgePort <= 0 {
			continue
		}
		ifIndexRaw, ok := basePortIfIndex[strconv.Itoa(bridgePort)]
		if !ok {
			continue
		}
		ifIndex, err := strconv.Atoi(strings.TrimSpace(ifIndexRaw))
		if err != nil || ifIndex <= 0 {
			continue
		}

		ipsSet := macToIPs[mac]
		if len(ipsSet) == 0 {
			key := fmt.Sprintf("%d|%s|", ifIndex, mac)
			if _, ok := seen[key]; ok {
				continue
			}
			seen[key] = struct{}{}
			out = append(out, PortDeviceResult{
				IP:         ip,
				IfIndex:    ifIndex,
				BridgePort: bridgePort,
				MAC:        mac,
				LearnedIP:  "",
				CheckedAt:  checkedAt,
			})
			continue
		}
		for learnedIP := range ipsSet {
			key := fmt.Sprintf("%d|%s|%s", ifIndex, mac, learnedIP)
			if _, ok := seen[key]; ok {
				continue
			}
			seen[key] = struct{}{}
			out = append(out, PortDeviceResult{
				IP:         ip,
				IfIndex:    ifIndex,
				BridgePort: bridgePort,
				MAC:        mac,
				LearnedIP:  learnedIP,
				CheckedAt:  checkedAt,
			})
		}
	}

	sort.Slice(out, func(i, j int) bool {
		if out[i].IfIndex != out[j].IfIndex {
			return out[i].IfIndex < out[j].IfIndex
		}
		if out[i].MAC != out[j].MAC {
			return out[i].MAC < out[j].MAC
		}
		return out[i].LearnedIP < out[j].LearnedIP
	})
	const maxRows = 20000
	if len(out) > maxRows {
		out = out[:maxRows]
	}
	return out
}

// snmpNumericString — значение SNMP как строка (int/float/[]byte) для Atoi.
func snmpNumericString(v any) string {
	switch x := v.(type) {
	case string:
		return x
	case []byte:
		return strings.TrimSpace(string(x))
	default:
		return strings.TrimSpace(fmt.Sprint(x))
	}
}

// normalizeMACKey приводит MAC к виду aa:bb:cc:dd:ee:ff для сопоставления FDB и ARP.
func normalizeMACKey(s string) string {
	s = strings.ToLower(strings.TrimSpace(s))
	if s == "" {
		return ""
	}
	s = strings.ReplaceAll(s, "-", ":")
	if strings.Count(s, ":") == 5 {
		parts := strings.Split(s, ":")
		if len(parts) != 6 {
			return ""
		}
		var b [6]byte
		for i, p := range parts {
			n, err := strconv.ParseUint(strings.TrimSpace(p), 16, 8)
			if err != nil {
				return ""
			}
			b[i] = byte(n)
		}
		return fmt.Sprintf("%02x:%02x:%02x:%02x:%02x:%02x", b[0], b[1], b[2], b[3], b[4], b[5])
	}
	if strings.HasPrefix(s, "0x") {
		h := strings.TrimPrefix(s, "0x")
		h = strings.ReplaceAll(h, ":", "")
		if len(h) != 12 {
			return ""
		}
		raw, err := hex.DecodeString(h)
		if err != nil || len(raw) != 6 {
			return ""
		}
		return fmt.Sprintf("%02x:%02x:%02x:%02x:%02x:%02x", raw[0], raw[1], raw[2], raw[3], raw[4], raw[5])
	}
	if len(s) == 12 {
		raw, err := hex.DecodeString(s)
		if err != nil || len(raw) != 6 {
			return ""
		}
		return fmt.Sprintf("%02x:%02x:%02x:%02x:%02x:%02x", raw[0], raw[1], raw[2], raw[3], raw[4], raw[5])
	}
	return ""
}

func dottedDecimalToMACTail(s string) string {
	p := strings.Split(strings.TrimSpace(s), ".")
	if len(p) < 6 {
		return ""
	}
	p = p[len(p)-6:]
	b := make([]byte, 6)
	for i := 0; i < 6; i++ {
		n, err := strconv.Atoi(p[i])
		if err != nil || n < 0 || n > 255 {
			return ""
		}
		b[i] = byte(n)
	}
	return fmt.Sprintf("%02x:%02x:%02x:%02x:%02x:%02x", b[0], b[1], b[2], b[3], b[4], b[5])
}

// probeIfTable собирает ifDescr, ifName (ifXTable), ifOperStatus по IF-MIB для списка портов в UI.
func probeIfTable(client *gosnmp.GoSNMP, ip string, checkedAt time.Time) []InterfaceResult {
	descr := walkAsMap(client, ".1.3.6.1.2.1.2.2.1.2")
	names := walkAsMap(client, ".1.3.6.1.2.1.31.1.1.1.1")
	oper := walkAsMap(client, ".1.3.6.1.2.1.2.2.1.8")
	idxs := mergeIFMIBKeys(descr, names, oper)
	const maxIF = 2048
	if len(idxs) > maxIF {
		idxs = idxs[:maxIF]
	}
	out := make([]InterfaceResult, 0, len(idxs))
	for _, ks := range idxs {
		idx, err := strconv.Atoi(ks)
		if err != nil || idx <= 0 {
			continue
		}
		out = append(out, InterfaceResult{
			IP:           ip,
			IfIndex:      idx,
			IfDescr:      descr[ks],
			IfName:       names[ks],
			IfOperStatus: mapIfOperStatus(oper[ks]),
			CheckedAt:    checkedAt,
		})
	}
	return out
}

func mergeIFMIBKeys(maps ...map[string]string) []string {
	seen := make(map[string]struct{})
	for _, m := range maps {
		for k := range m {
			seen[k] = struct{}{}
		}
	}
	out := make([]string, 0, len(seen))
	for k := range seen {
		out = append(out, k)
	}
	sort.Slice(out, func(i, j int) bool {
		ai, e1 := strconv.Atoi(out[i])
		bj, e2 := strconv.Atoi(out[j])
		if e1 != nil || e2 != nil {
			return out[i] < out[j]
		}
		return ai < bj
	})
	return out
}

func mapIfOperStatus(s string) string {
	s = strings.TrimSpace(s)
	switch s {
	case "1":
		return "up"
	case "2":
		return "down"
	case "3":
		return "testing"
	case "4":
		return "unknown"
	case "5":
		return "dormant"
	case "6":
		return "notPresent"
	case "7":
		return "lowerLayerDown"
	default:
		return s
	}
}

// snmpBytesToDisplay строка для OCTET STRING SNMP: UTF-8 текст, иначе MAC (6 байт) или 0x+hex.
func snmpBytesToDisplay(b []byte) string {
	if len(b) == 0 {
		return ""
	}
	if utf8.Valid(b) {
		s := strings.TrimSpace(string(b))
		if s != "" {
			return s
		}
	}
	// LLDP chassis/port id часто — MAC из 6 байт (не UTF-8).
	if len(b) == 6 {
		return fmt.Sprintf("%02x:%02x:%02x:%02x:%02x:%02x", b[0], b[1], b[2], b[3], b[4], b[5])
	}
	return "0x" + hex.EncodeToString(b)
}

func snmpValueToString(v any) string {
	if b, ok := v.([]byte); ok {
		return snmpBytesToDisplay(b)
	}
	return strings.TrimSpace(fmt.Sprint(v))
}

// lldpRemColsPrefix — колонки lldpRemEntry: ...1.1.<col>.<timeMark>.<localPort>.<remIndex>
const lldpRemColsPrefix = "1.0.8802.1.1.2.1.4.1.1"

// lldpRemTableOID — корень lldpRemTable (IEEE 802.1AB LLDP-MIB).
const lldpRemTableOID = "1.0.8802.1.1.2.1.4.1"

type lldpRemAggRow struct {
	localPort, chassis, portID, sysName string
}

func lldpRemRowsFromWalk(rows map[string]*lldpRemAggRow, pduName string, val any) {
	n := snmpOIDTrim(pduName)
	if !strings.HasPrefix(n, lldpRemColsPrefix+".") {
		return
	}
	rest := strings.TrimPrefix(n, lldpRemColsPrefix+".")
	parts := strings.Split(rest, ".")
	if len(parts) < 2 {
		return
	}
	col := parts[0]
	// Индекс строки таблицы — все субидентификаторы после номера колонки (часто 3 компонента, но оставляем произвольную длину).
	rowKey := strings.Join(parts[1:], ".")
	v := snmpValueToString(val)
	r := rows[rowKey]
	if r == nil {
		r = &lldpRemAggRow{}
		rows[rowKey] = r
	}
	switch col {
	case "2":
		r.localPort = v
	case "5":
		r.chassis = v
	case "7":
		r.portID = v
	case "9":
		r.sysName = v
	}
	// Индекс lldpRemEntry: { timeMark, localPortNum, remIndex } — часть прошивок не отдаёт колонку 2, но порт есть в суффиксе OID.
	idx := parts[1:]
	if len(idx) >= 3 && strings.TrimSpace(r.localPort) == "" {
		r.localPort = idx[1]
	}
}

// probeLLDPViaRemTableWalk один раз обходит всю lldpRemTable (стандарт IEEE 802.1AB).
// Сначала GET-BULK (меньше обменов); при пустом результате — Walk (GetNext). Отдельно есть цепочка GetNext
// в probeLLDPViaGetNextRemTable на случай сбоев внутреннего Walk у gosnmp на части прошивок.
func probeLLDPViaRemTableWalk(client *gosnmp.GoSNMP, ip string, checkedAt time.Time) []LLDPResult {
	rows := make(map[string]*lldpRemAggRow)

	record := func(pduName string, val any) {
		lldpRemRowsFromWalk(rows, pduName, val)
	}

	skipPDU := func(t gosnmp.Asn1BER) bool {
		return t == gosnmp.NoSuchObject || t == gosnmp.NoSuchInstance || t == gosnmp.EndOfMibView
	}

	walkOID := "." + lldpRemTableOID
	pdus, berr := client.BulkWalkAll(walkOID)
	if berr != nil {
		log.Printf("lldp remTable BulkWalkAll target=%s: %v", client.Target, berr)
	}
	for _, p := range pdus {
		if skipPDU(p.Type) {
			continue
		}
		record(p.Name, p.Value)
	}

	if len(rows) == 0 {
		if err := client.Walk(walkOID, func(pdu gosnmp.SnmpPDU) error {
			if skipPDU(pdu.Type) {
				return nil
			}
			record(pdu.Name, pdu.Value)
			return nil
		}); err != nil {
			log.Printf("lldp remTable Walk target=%s: %v", client.Target, err)
		}
	}

	out := make([]LLDPResult, 0, len(rows))
	for _, r := range rows {
		if r.localPort == "" && r.chassis == "" && r.portID == "" && r.sysName == "" {
			continue
		}
		out = append(out, LLDPResult{
			IP:              ip,
			LocalPortNum:    r.localPort,
			RemoteChassisID: r.chassis,
			RemotePortID:    r.portID,
			RemoteSysName:   r.sysName,
			CheckedAt:       checkedAt,
		})
	}
	return out
}

// probeLLDPViaGetNextRemTable — пошаговый GetNext по поддереву lldpRemTable без пакетной логики Walk/BulkWalk.
// Обходит случаи, когда snmpwalk с хоста работает, а внутренний walk gosnmp обрывается или не вызывает callback.
func probeLLDPViaGetNextRemTable(client *gosnmp.GoSNMP, ip string, checkedAt time.Time) []LLDPResult {
	rows := make(map[string]*lldpRemAggRow)
	record := func(pduName string, val any) {
		lldpRemRowsFromWalk(rows, pduName, val)
	}

	const maxSteps = 80000
	oid := "." + lldpRemTableOID
	for step := 0; step < maxSteps; step++ {
		pkt, err := client.GetNext([]string{oid})
		if err != nil {
			log.Printf("lldp remTable GetNext target=%s step=%d: %v", client.Target, step, err)
			break
		}
		if pkt == nil || len(pkt.Variables) == 0 {
			break
		}
		vb := pkt.Variables[0]
		if vb.Type == gosnmp.NoSuchObject || vb.Type == gosnmp.NoSuchInstance || vb.Type == gosnmp.EndOfMibView {
			break
		}
		n := snmpOIDTrim(vb.Name)
		if n != lldpRemTableOID && !strings.HasPrefix(n, lldpRemTableOID+".") {
			break
		}
		if n != lldpRemTableOID {
			record(vb.Name, vb.Value)
		}
		oid = vb.Name
	}

	out := make([]LLDPResult, 0, len(rows))
	for _, r := range rows {
		if r.localPort == "" && r.chassis == "" && r.portID == "" && r.sysName == "" {
			continue
		}
		out = append(out, LLDPResult{
			IP:              ip,
			LocalPortNum:    r.localPort,
			RemoteChassisID: r.chassis,
			RemotePortID:    r.portID,
			RemoteSysName:   r.sysName,
			CheckedAt:       checkedAt,
		})
	}
	return out
}

func probeLLDPViaColumnWalks(client *gosnmp.GoSNMP, ip string, checkedAt time.Time) []LLDPResult {
	const (
		lldpRemLocalPortNum = ".1.0.8802.1.1.2.1.4.1.1.2"
		lldpRemChassisID    = ".1.0.8802.1.1.2.1.4.1.1.5"
		lldpRemPortID       = ".1.0.8802.1.1.2.1.4.1.1.7"
		lldpRemSysName      = ".1.0.8802.1.1.2.1.4.1.1.9"
	)

	ports := walkAsMap(client, lldpRemLocalPortNum)
	chassis := walkAsMap(client, lldpRemChassisID)
	remotePorts := walkAsMap(client, lldpRemPortID)
	sysNames := walkAsMap(client, lldpRemSysName)

	keys := make(map[string]struct{})
	for k := range ports {
		keys[k] = struct{}{}
	}
	for k := range chassis {
		keys[k] = struct{}{}
	}
	for k := range remotePorts {
		keys[k] = struct{}{}
	}
	for k := range sysNames {
		keys[k] = struct{}{}
	}

	out := make([]LLDPResult, 0, len(keys))
	for k := range keys {
		lp := strings.TrimSpace(ports[k])
		if lp == "" {
			lp = lldpRemIndexLocalPortFromKey(k)
		}
		item := LLDPResult{
			IP:              ip,
			LocalPortNum:    lp,
			RemoteChassisID: chassis[k],
			RemotePortID:    remotePorts[k],
			RemoteSysName:   sysNames[k],
			CheckedAt:       checkedAt,
		}
		if item.LocalPortNum == "" && item.RemoteChassisID == "" && item.RemotePortID == "" && item.RemoteSysName == "" {
			continue
		}
		out = append(out, item)
	}
	return out
}

func probeLLDP(client *gosnmp.GoSNMP, ip string, checkedAt time.Time) []LLDPResult {
	out := probeLLDPViaRemTableWalk(client, ip, checkedAt)
	if len(out) == 0 {
		out = probeLLDPViaColumnWalks(client, ip, checkedAt)
	}
	if len(out) == 0 {
		out = probeLLDPViaGetNextRemTable(client, ip, checkedAt)
	}
	return enrichLLDPLocalPortLabels(client, out)
}

// lldpRemIndexLocalPortFromKey суффикс ключа walk: timeMark.localPortNum.remIndex (IEEE LLDP remTable).
func lldpRemIndexLocalPortFromKey(key string) string {
	parts := strings.Split(key, ".")
	if len(parts) >= 3 {
		return parts[1]
	}
	return ""
}

// lldpLocPortDescOIDs — lldpLocPortDesc по номеру порта (RFC 4502 и встречающийся в поле вариант).
var lldpLocPortDescOIDs = []string{
	".1.0.8802.1.1.2.1.2.1.7.1.3",
	".1.0.8802.1.1.2.1.3.7.1.3",
}

func probeLLDPLocPortDescByPortNum(client *gosnmp.GoSNMP) map[string]string {
	out := make(map[string]string)
	for _, base := range lldpLocPortDescOIDs {
		for k, v := range walkAsMap(client, base) {
			v = strings.TrimSpace(v)
			if v != "" {
				out[k] = v
			}
		}
	}
	return out
}

func formatLocalPortLabel(portNum, ifDescr string) string {
	portNum = strings.TrimSpace(portNum)
	ifDescr = strings.TrimSpace(ifDescr)
	if ifDescr != "" && portNum != "" && ifDescr != portNum {
		return portNum + " — " + ifDescr
	}
	if ifDescr != "" {
		return ifDescr
	}
	return portNum
}

// enrichLLDPLocalPortLabels подставляет lldpLocPortDesc (как в CLI) к номеру локального порта.
func enrichLLDPLocalPortLabels(client *gosnmp.GoSNMP, items []LLDPResult) []LLDPResult {
	if len(items) == 0 {
		return items
	}
	descByPort := probeLLDPLocPortDescByPortNum(client)
	if len(descByPort) == 0 {
		return items
	}
	for i := range items {
		num := strings.TrimSpace(items[i].LocalPortNum)
		items[i].LocalPortNum = formatLocalPortLabel(num, descByPort[num])
	}
	return items
}

func snmpOIDTrim(s string) string {
	return strings.TrimPrefix(strings.TrimSpace(s), ".")
}

// walkAsMap выполняет поддерево SNMP по base oid. Сначала GET-BULK (быстро); при ошибке — Walk (GetNext),
// что совместимо с большим числом встраиваемых коммутаторов.
func walkAsMap(client *gosnmp.GoSNMP, oid string) map[string]string {
	base := snmpOIDTrim(oid)
	prefix := base + "."
	out := make(map[string]string)

	record := func(pduName string, val any) {
		n := snmpOIDTrim(pduName)
		if !strings.HasPrefix(n, prefix) {
			return
		}
		key := strings.TrimPrefix(n, prefix)
		if key == "" {
			return
		}
		out[key] = snmpValueToString(val)
	}

	pdus, err := client.BulkWalkAll(oid)
	if err != nil {
		log.Printf("lldp snmp BulkWalkAll target=%s oid=%s: %v (fallback Walk)", client.Target, base, err)
		if werr := client.Walk(oid, func(pdu gosnmp.SnmpPDU) error {
			record(pdu.Name, pdu.Value)
			return nil
		}); werr != nil {
			log.Printf("lldp snmp Walk target=%s oid=%s: %v", client.Target, base, werr)
		}
		return out
	}
	for _, p := range pdus {
		record(p.Name, p.Value)
	}
	return out
}

func expandTargets(cidrs []string, excludeIPs []string) ([]string, error) {
	excluded := make(map[string]struct{}, len(excludeIPs))
	for _, ip := range excludeIPs {
		excluded[ip] = struct{}{}
	}

	seen := make(map[string]struct{})
	out := make([]string, 0, 256)
	for _, c := range cidrs {
		ip, ipnet, err := net.ParseCIDR(c)
		if err != nil {
			return nil, err
		}
		start := ip.Mask(ipnet.Mask).To4()
		if start == nil {
			continue
		}
		for current := dupIP(start); ipnet.Contains(current); incIP(current) {
			host := current.String()
			if _, ok := excluded[host]; ok {
				continue
			}
			if _, ok := seen[host]; ok {
				continue
			}
			seen[host] = struct{}{}
			out = append(out, host)
		}
	}
	return out, nil
}

func probeHost(ip string, timeoutMS int) bool {
	if timeoutMS <= 0 {
		timeoutMS = 700
	}
	timeoutSec := strconv.Itoa(max(1, timeoutMS/1000))

	var cmd *exec.Cmd
	if runtime.GOOS == "windows" {
		// -n 1 one packet, -w timeout in ms
		cmd = exec.Command("ping", "-n", "1", "-w", strconv.Itoa(timeoutMS), ip)
	} else {
		// -c 1 one packet, -W timeout in sec on Linux/macOS
		cmd = exec.Command("ping", "-c", "1", "-W", timeoutSec, ip)
	}
	if err := cmd.Run(); err != nil {
		// На Linux/macOS ping с -c 1 даёт exit 1 при отсутствии ответа — это ожидаемо для большинства
		// адресов в CIDR, не ошибка приложения. Логировать каждый такой случай бессмысленно засоряет journal.
		if os.Getenv("NETTOPO_LOG_PING_FAILURES") == "true" {
			log.Printf("ping: нет ответа от %s: %v", ip, err)
		}
		return false
	}
	return true
}

func probeTCPPort(ip string, port int, timeoutMS int) bool {
	if timeoutMS <= 0 {
		timeoutMS = 700
	}
	addr, err := netip.ParseAddr(ip)
	if err != nil {
		return false
	}
	target := net.JoinHostPort(addr.String(), strconv.Itoa(port))
	conn, err := net.DialTimeout("tcp", target, time.Duration(timeoutMS)*time.Millisecond)
	if err != nil {
		return false
	}
	_ = conn.Close()
	return true
}

func dupIP(ip net.IP) net.IP {
	out := make(net.IP, len(ip))
	copy(out, ip)
	return out
}

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

func max(a, b int) int {
	if a > b {
		return a
	}
	return b
}