DebTik/internal/dhcp/server_manager.go

package dhcp

import (
	"encoding/json"
	"fmt"
	"log"
	"net"
	"os"
	"os/exec"
	"path/filepath"
	"sort"
	"strconv"
	"strings"
	"sync"
	"time"
)

const (
	DHCPServerStoreFile = "/etc/proxmox-router/dhcp_server.json"
	DnsmasqConfFile     = "/etc/dnsmasq.d/debtik_dhcp.conf"
	DnsmasqLeasesFile   = "/var/lib/misc/dnsmasq.leases"
)

type ServerManager struct {
	mu           sync.RWMutex
	storePath    string
	confPath     string
	leasesPath   string
	servers      map[string]DHCPServerInstance
	networks     map[string]DHCPNetwork
	staticLeases map[string]DHCPLease
	options      map[string]DHCPOption
}

func NewServerManager() *ServerManager {
	sm := &ServerManager{
		storePath:    DHCPServerStoreFile,
		confPath:     DnsmasqConfFile,
		leasesPath:   DnsmasqLeasesFile,
		servers:      make(map[string]DHCPServerInstance),
		networks:     make(map[string]DHCPNetwork),
		staticLeases: make(map[string]DHCPLease),
		options:      make(map[string]DHCPOption),
	}

	_ = os.MkdirAll(filepath.Dir(sm.storePath), 0755)
	_ = os.MkdirAll(filepath.Dir(sm.confPath), 0755)

	if err := sm.load(); err != nil {
		log.Printf("[DHCP-Server] Error loading config: %v", err)
	}

	// Initial render and reload dnsmasq
	if err := sm.applyDnsmasqConfigLocked(); err != nil {
		log.Printf("[DHCP-Server] Error applying dnsmasq config: %v", err)
	}

	return sm
}

func (sm *ServerManager) load() error {
	sm.mu.Lock()
	defer sm.mu.Unlock()

	data, err := os.ReadFile(sm.storePath)
	if err != nil {
		if os.IsNotExist(err) {
			// Populate default option presets (MikroTik standard presets)
			sm.initDefaultOptions()
			return nil
		}
		return err
	}

	var store DHCPServerConfigStore
	if err := json.Unmarshal(data, &store); err != nil {
		return err
	}

	for _, s := range store.Servers {
		sm.servers[s.ID] = s
	}
	for _, n := range store.Networks {
		sm.networks[n.ID] = n
	}
	for _, l := range store.StaticLeases {
		sm.staticLeases[l.ID] = l
	}
	for _, o := range store.Options {
		sm.options[o.ID] = o
	}

	if len(sm.options) == 0 {
		sm.initDefaultOptions()
	}

	return nil
}

func (sm *ServerManager) initDefaultOptions() {
	presets := []DHCPOption{
		{ID: "opt-ntp", Name: "ntp-servers", Code: 42, Value: "192.168.88.1", Comment: "NTP Time Servers (Option 42)"},
		{ID: "opt-tftp-name", Name: "tftp-server-name", Code: 66, Value: "192.168.88.50", Comment: "TFTP Server Name / IP (Option 66)"},
		{ID: "opt-bootfile", Name: "bootfile-name", Code: 67, Value: "pxelinux.0", Comment: "PXE Boot File (Option 67)"},
		{ID: "opt-unifi", Name: "unifi-controller", Code: 43, Value: "01:04:c0:a8:58:0a", Comment: "UniFi Inform Controller (Option 43 Hex IP)"},
		{ID: "opt-voip", Name: "cisco-voip-tftp", Code: 150, Value: "192.168.88.50", Comment: "Cisco VoIP TFTP (Option 150)"},
		{ID: "opt-capwap", Name: "capwap-ac", Code: 138, Value: "192.168.88.10", Comment: "CAPWAP Access Controller (Option 138)"},
		{ID: "opt-wpad", Name: "wpad-url", Code: 252, Value: "\"http://wpad/wpad.dat\"", Comment: "Web Proxy Auto-Discovery (Option 252)"},
	}
	for _, p := range presets {
		sm.options[p.ID] = p
	}
}

func (sm *ServerManager) saveLocked() error {
	store := DHCPServerConfigStore{
		Servers:      make([]DHCPServerInstance, 0, len(sm.servers)),
		Networks:     make([]DHCPNetwork, 0, len(sm.networks)),
		StaticLeases: make([]DHCPLease, 0, len(sm.staticLeases)),
		Options:      make([]DHCPOption, 0, len(sm.options)),
	}

	for _, s := range sm.servers {
		copyS := s
		copyS.Running = false
		copyS.ActiveLeases = 0
		store.Servers = append(store.Servers, copyS)
	}
	for _, n := range sm.networks {
		store.Networks = append(store.Networks, n)
	}
	for _, l := range sm.staticLeases {
		store.StaticLeases = append(store.StaticLeases, l)
	}
	for _, o := range sm.options {
		store.Options = append(store.Options, o)
	}

	data, err := json.MarshalIndent(store, "", "  ")
	if err != nil {
		return err
	}

	return os.WriteFile(sm.storePath, data, 0644)
}

func (sm *ServerManager) applyDnsmasqConfigLocked() error {
	var sb strings.Builder
	sb.WriteString("# ==================================================================\n")
	sb.WriteString("# DebTik DHCP Server Configuration (MikroTik RouterOS style)\n")
	sb.WriteString("# Auto-generated by DebTik Network Appliance. DO NOT EDIT DIRECTLY.\n")
	sb.WriteString("# ==================================================================\n\n")

	sb.WriteString("dhcp-authoritative\n")
	sb.WriteString("dhcp-leasefile=/var/lib/misc/dnsmasq.leases\n")
	sb.WriteString("log-dhcp\n")
	sb.WriteString("bind-dynamic\n\n")

	activeServerCount := 0
	for _, srv := range sm.servers {
		if srv.Disabled {
			continue
		}
		activeServerCount++
		tag := sanitizeTag(srv.Name)
		sb.WriteString(fmt.Sprintf("# --- DHCP Server: %s on %s ---\n", srv.Name, srv.Interface))
		sb.WriteString(fmt.Sprintf("interface=%s\n", srv.Interface))

		leaseTime := srv.LeaseTime
		if leaseTime == "" {
			leaseTime = "12h"
		}

		// Parse Address Pool range (e.g. 192.168.88.10-192.168.88.254)
		startIP, endIP, netmask := parseAddressPool(srv.AddressPool)
		if startIP != "" && endIP != "" {
			if netmask != "" {
				sb.WriteString(fmt.Sprintf("dhcp-range=set:%s,interface:%s,%s,%s,%s,%s\n", tag, srv.Interface, startIP, endIP, netmask, leaseTime))
			} else {
				sb.WriteString(fmt.Sprintf("dhcp-range=set:%s,interface:%s,%s,%s,%s\n", tag, srv.Interface, startIP, endIP, leaseTime))
			}
		}
		sb.WriteString("\n")
	}

	// Subnet Networks & Options
	sb.WriteString("# --- DHCP Networks & Options (/ip dhcp-server network) ---\n")
	for _, netw := range sm.networks {
		sb.WriteString(fmt.Sprintf("# Subnet: %s\n", netw.Address))
		_, ipNet, err := net.ParseCIDR(netw.Address)
		networkTag := ""
		if err == nil && ipNet != nil {
			networkTag = fmt.Sprintf("net_%s", strings.ReplaceAll(ipNet.IP.String(), ".", "_"))
			// Match server range tag or subnet tag
			sb.WriteString(fmt.Sprintf("dhcp-range=set:%s,%s,static\n", networkTag, ipNet.IP.String()))
		}

		// Determine target tag (either network tag or global/matched)
		targetTag := ""
		if networkTag != "" {
			targetTag = fmt.Sprintf("tag:%s,", networkTag)
		}

		// Option 3: Gateway (Router)
		if netw.Gateway != "" {
			sb.WriteString(fmt.Sprintf("dhcp-option=%soption:router,%s\n", targetTag, netw.Gateway))
		}

		// Option 6: DNS Servers
		if len(netw.DNSServers) > 0 {
			sb.WriteString(fmt.Sprintf("dhcp-option=%soption:dns-server,%s\n", targetTag, strings.Join(netw.DNSServers, ",")))
		}

		// Option 15: Domain Name
		if netw.Domain != "" {
			sb.WriteString(fmt.Sprintf("dhcp-option=%soption:domain-name,%s\n", targetTag, netw.Domain))
		}

		// Option 42: NTP Servers (MikroTik /ip dhcp-server network ntp-server)
		if len(netw.NTPServers) > 0 {
			sb.WriteString(fmt.Sprintf("dhcp-option=%soption:ntp-server,%s\n", targetTag, strings.Join(netw.NTPServers, ",")))
		}

		// Option 66: TFTP Server Name / IP (next-server)
		if netw.NextServer != "" {
			sb.WriteString(fmt.Sprintf("dhcp-option=%soption:tftp-server,%s\n", targetTag, netw.NextServer))
		}

		// Option 67: Boot File Name (PXE)
		if netw.BootFileName != "" {
			sb.WriteString(fmt.Sprintf("dhcp-option=%soption:bootfile-name,%s\n", targetTag, netw.BootFileName))
			if netw.NextServer != "" {
				sb.WriteString(fmt.Sprintf("dhcp-boot=%s%s,,%s\n", targetTag, netw.BootFileName, netw.NextServer))
			} else {
				sb.WriteString(fmt.Sprintf("dhcp-boot=%s%s\n", targetTag, netw.BootFileName))
			}
		}

		// Option 44: WINS Servers
		if len(netw.WINSServers) > 0 {
			sb.WriteString(fmt.Sprintf("dhcp-option=%soption:netbios-ns,%s\n", targetTag, strings.Join(netw.WINSServers, ",")))
		}

		// Linked custom DHCP options
		for _, optID := range netw.DHCPOptions {
			if opt, exists := sm.options[optID]; exists {
				sb.WriteString(fmt.Sprintf("dhcp-option=%s%d,%s # %s\n", targetTag, opt.Code, opt.Value, opt.Name))
			}
		}
		sb.WriteString("\n")
	}

	// Static Leases & Reservations (/ip dhcp-server lease)
	sb.WriteString("# --- Static Leases & Reservations (/ip dhcp-server lease) ---\n")
	for _, l := range sm.staticLeases {
		if l.Disabled {
			continue
		}
		mac := strings.ToLower(strings.TrimSpace(l.MACAddress))
		ip := strings.TrimSpace(l.Address)
		hostname := strings.TrimSpace(l.HostName)
		if hostname == "" {
			hostname = "reserved"
		}
		if mac != "" && ip != "" {
			sb.WriteString(fmt.Sprintf("dhcp-host=%s,%s,%s,infinite\n", mac, ip, hostname))
		}
	}

	// Write config to disk
	if err := os.WriteFile(sm.confPath, []byte(sb.String()), 0644); err != nil {
		return fmt.Errorf("failed to write dnsmasq config: %w", err)
	}

	// Restart or reload dnsmasq
	if activeServerCount > 0 {
		_ = exec.Command("systemctl", "restart", "dnsmasq").Run()
	} else {
		_ = exec.Command("systemctl", "reload", "dnsmasq").Run()
	}

	return nil
}

func (sm *ServerManager) ListServers() []DHCPServerInstance {
	sm.mu.RLock()
	defer sm.mu.RUnlock()

	activeLeases := sm.countActiveLeasesByServer()

	list := make([]DHCPServerInstance, 0, len(sm.servers))
	for _, s := range sm.servers {
		copyS := s
		copyS.Running = !s.Disabled && isInterfaceUp(s.Interface)
		copyS.ActiveLeases = activeLeases[s.Name]
		list = append(list, copyS)
	}

	sort.Slice(list, func(i, j int) bool {
		return list[i].Name < list[j].Name
	})

	return list
}

func (sm *ServerManager) GetServer(id string) (DHCPServerInstance, bool) {
	sm.mu.RLock()
	defer sm.mu.RUnlock()

	s, ok := sm.servers[id]
	if !ok {
		return DHCPServerInstance{}, false
	}
	s.Running = !s.Disabled && isInterfaceUp(s.Interface)
	return s, true
}

func (sm *ServerManager) SaveServer(inst DHCPServerInstance) (DHCPServerInstance, error) {
	sm.mu.Lock()
	defer sm.mu.Unlock()

	if inst.ID == "" {
		inst.ID = fmt.Sprintf("dhcp-%d", time.Now().UnixNano())
	}
	if inst.Name == "" {
		inst.Name = fmt.Sprintf("dhcp%d", len(sm.servers)+1)
	}
	if inst.LeaseTime == "" {
		inst.LeaseTime = "12h"
	}
	inst.Authoritative = true

	sm.servers[inst.ID] = inst
	if err := sm.saveLocked(); err != nil {
		return inst, err
	}

	_ = sm.applyDnsmasqConfigLocked()
	return inst, nil
}

func (sm *ServerManager) DeleteServer(id string) error {
	sm.mu.Lock()
	defer sm.mu.Unlock()

	delete(sm.servers, id)
	if err := sm.saveLocked(); err != nil {
		return err
	}

	return sm.applyDnsmasqConfigLocked()
}

func (sm *ServerManager) ToggleServerState(id string, disabled bool) error {
	sm.mu.Lock()
	defer sm.mu.Unlock()

	s, exists := sm.servers[id]
	if !exists {
		return fmt.Errorf("server not found: %s", id)
	}

	s.Disabled = disabled
	sm.servers[id] = s
	if err := sm.saveLocked(); err != nil {
		return err
	}

	return sm.applyDnsmasqConfigLocked()
}

// ======================== NETWORKS ========================
func (sm *ServerManager) ListNetworks() []DHCPNetwork {
	sm.mu.RLock()
	defer sm.mu.RUnlock()

	list := make([]DHCPNetwork, 0, len(sm.networks))
	for _, n := range sm.networks {
		list = append(list, n)
	}

	sort.Slice(list, func(i, j int) bool {
		return list[i].Address < list[j].Address
	})

	return list
}

func (sm *ServerManager) SaveNetwork(netw DHCPNetwork) (DHCPNetwork, error) {
	sm.mu.Lock()
	defer sm.mu.Unlock()

	if netw.ID == "" {
		netw.ID = fmt.Sprintf("net-%d", time.Now().UnixNano())
	}
	if netw.Address == "" {
		return netw, fmt.Errorf("subnet address (CIDR) is required")
	}

	sm.networks[netw.ID] = netw
	if err := sm.saveLocked(); err != nil {
		return netw, err
	}

	_ = sm.applyDnsmasqConfigLocked()
	return netw, nil
}

func (sm *ServerManager) DeleteNetwork(id string) error {
	sm.mu.Lock()
	defer sm.mu.Unlock()

	delete(sm.networks, id)
	if err := sm.saveLocked(); err != nil {
		return err
	}

	return sm.applyDnsmasqConfigLocked()
}

// ======================== LEASES ========================
func (sm *ServerManager) ListLeases() []DHCPLease {
	sm.mu.RLock()
	defer sm.mu.RUnlock()

	dynamicLeases := sm.readDnsmasqLeasesFile()
	staticMap := make(map[string]DHCPLease)
	for _, st := range sm.staticLeases {
		staticMap[strings.ToLower(st.MACAddress)] = st
	}

	result := make([]DHCPLease, 0)
	seenMACs := make(map[string]bool)

	// Combine dynamic leases
	for _, dl := range dynamicLeases {
		macLower := strings.ToLower(dl.MACAddress)
		seenMACs[macLower] = true

		if st, isStatic := staticMap[macLower]; isStatic {
			dl.Dynamic = false
			dl.Status = "static"
			dl.Comment = st.Comment
			dl.Disabled = st.Disabled
			dl.ExpiresIn = "never (static)"
		} else {
			dl.Dynamic = true
			dl.Status = "bound"
		}
		result = append(result, dl)
	}

	// Add static reservations that haven't acquired lease yet
	for macLower, st := range staticMap {
		if !seenMACs[macLower] {
			st.Dynamic = false
			st.Status = "waiting"
			st.ExpiresIn = "never (static)"
			result = append(result, st)
		}
	}

	sort.Slice(result, func(i, j int) bool {
		return compareIPs(net.ParseIP(result[i].Address), net.ParseIP(result[j].Address)) < 0
	})

	return result
}

func (sm *ServerManager) readDnsmasqLeasesFile() []DHCPLease {
	data, err := os.ReadFile(sm.leasesPath)
	if err != nil {
		return nil
	}

	lines := strings.Split(string(data), "\n")
	leases := make([]DHCPLease, 0, len(lines))

	now := time.Now()
	for _, line := range lines {
		line = strings.TrimSpace(line)
		if line == "" {
			continue
		}
		// Format: <timestamp> <mac> <ip> <hostname> <client-id>
		parts := strings.Fields(line)
		if len(parts) < 3 {
			continue
		}

		expTimestamp, _ := strconv.ParseInt(parts[0], 10, 64)
		mac := parts[1]
		ip := parts[2]
		hostname := "*"
		if len(parts) >= 4 && parts[3] != "*" {
			hostname = parts[3]
		}
		clientID := ""
		if len(parts) >= 5 && parts[4] != "*" {
			clientID = parts[4]
		}

		expiresAt := time.Unix(expTimestamp, 0)
		expiresIn := "expired"
		if expiresAt.After(now) {
			dur := expiresAt.Sub(now).Truncate(time.Minute)
			hours := int(dur.Hours())
			mins := int(dur.Minutes()) % 60
			expiresIn = fmt.Sprintf("%dh %dm", hours, mins)
		}

		// Determine server by matching IP against configured networks/pools
		serverName := sm.matchServerForIP(ip)

		leases = append(leases, DHCPLease{
			ID:         fmt.Sprintf("lease-%s", strings.ReplaceAll(mac, ":", "")),
			Address:    ip,
			MACAddress: mac,
			HostName:   hostname,
			ClientID:   clientID,
			Server:     serverName,
			ExpiresAt:  expiresAt,
			ExpiresIn:  expiresIn,
			Dynamic:    true,
			Status:     "bound",
		})
	}

	return leases
}

func (sm *ServerManager) matchServerForIP(ipStr string) string {
	targetIP := net.ParseIP(ipStr)
	if targetIP == nil {
		return "dhcp1"
	}

	for _, srv := range sm.servers {
		startIP, endIP, _ := parseAddressPool(srv.AddressPool)
		if startIP != "" && endIP != "" {
			s := net.ParseIP(startIP)
			e := net.ParseIP(endIP)
			if s != nil && e != nil && compareIPs(targetIP, s) >= 0 && compareIPs(targetIP, e) <= 0 {
				return srv.Name
			}
		}
	}
	return "dhcp1"
}

func (sm *ServerManager) countActiveLeasesByServer() map[string]int {
	counts := make(map[string]int)
	leases := sm.readDnsmasqLeasesFile()
	for _, l := range leases {
		counts[l.Server]++
	}
	return counts
}

func (sm *ServerManager) SaveStaticLease(lease DHCPLease) (DHCPLease, error) {
	sm.mu.Lock()
	defer sm.mu.Unlock()

	if lease.ID == "" {
		lease.ID = fmt.Sprintf("static-%d", time.Now().UnixNano())
	}
	if lease.MACAddress == "" || lease.Address == "" {
		return lease, fmt.Errorf("both MAC address and IP address are required")
	}

	lease.MACAddress = strings.ToLower(lease.MACAddress)
	lease.Dynamic = false
	lease.Status = "static"

	sm.staticLeases[lease.ID] = lease
	if err := sm.saveLocked(); err != nil {
		return lease, err
	}

	_ = sm.applyDnsmasqConfigLocked()
	return lease, nil
}

func (sm *ServerManager) DeleteStaticLease(id string) error {
	sm.mu.Lock()
	defer sm.mu.Unlock()

	delete(sm.staticLeases, id)
	if err := sm.saveLocked(); err != nil {
		return err
	}

	return sm.applyDnsmasqConfigLocked()
}

func (sm *ServerManager) MakeStaticLease(mac, ip, hostname, comment string) (DHCPLease, error) {
	sm.mu.Lock()
	defer sm.mu.Unlock()

	macLower := strings.ToLower(strings.TrimSpace(mac))
	// Check if already in static leases
	for _, st := range sm.staticLeases {
		if strings.ToLower(st.MACAddress) == macLower {
			st.Address = ip
			if hostname != "" && hostname != "*" {
				st.HostName = hostname
			}
			if comment != "" {
				st.Comment = comment
			}
			sm.staticLeases[st.ID] = st
			_ = sm.saveLocked()
			_ = sm.applyDnsmasqConfigLocked()
			return st, nil
		}
	}

	id := fmt.Sprintf("static-%d", time.Now().UnixNano())
	st := DHCPLease{
		ID:         id,
		MACAddress: macLower,
		Address:    ip,
		HostName:   hostname,
		Server:     "all",
		Comment:    comment,
		Dynamic:    false,
		Status:     "static",
	}

	sm.staticLeases[id] = st
	if err := sm.saveLocked(); err != nil {
		return st, err
	}

	_ = sm.applyDnsmasqConfigLocked()
	return st, nil
}

// ======================== OPTIONS ========================
func (sm *ServerManager) ListOptions() []DHCPOption {
	sm.mu.RLock()
	defer sm.mu.RUnlock()

	list := make([]DHCPOption, 0, len(sm.options))
	for _, o := range sm.options {
		list = append(list, o)
	}

	sort.Slice(list, func(i, j int) bool {
		return list[i].Code < list[j].Code
	})

	return list
}

func (sm *ServerManager) SaveOption(opt DHCPOption) (DHCPOption, error) {
	sm.mu.Lock()
	defer sm.mu.Unlock()

	if opt.ID == "" {
		opt.ID = fmt.Sprintf("opt-%d", time.Now().UnixNano())
	}
	if opt.Name == "" || opt.Code <= 0 || opt.Code > 254 {
		return opt, fmt.Errorf("valid option name and code (1-254) are required")
	}

	sm.options[opt.ID] = opt
	if err := sm.saveLocked(); err != nil {
		return opt, err
	}

	_ = sm.applyDnsmasqConfigLocked()
	return opt, nil
}

func (sm *ServerManager) DeleteOption(id string) error {
	sm.mu.Lock()
	defer sm.mu.Unlock()

	delete(sm.options, id)
	if err := sm.saveLocked(); err != nil {
		return err
	}

	return sm.applyDnsmasqConfigLocked()
}

// ======================== SETUP WIZARD (MikroTik style) ========================
func (sm *ServerManager) RunSetupWizard(req DHCPServerSetupRequest) error {
	sm.mu.Lock()
	defer sm.mu.Unlock()

	if req.Interface == "" {
		return fmt.Errorf("interface is required")
	}
	if req.AddressSpace == "" {
		req.AddressSpace = "192.168.88.0/24"
	}
	if req.Gateway == "" {
		req.Gateway = "192.168.88.1"
	}
	if req.AddressPool == "" {
		req.AddressPool = "192.168.88.10-192.168.88.254"
	}
	if len(req.DNSServers) == 0 {
		req.DNSServers = []string{req.Gateway, "1.1.1.1"}
	}
	if req.LeaseTime == "" {
		req.LeaseTime = "12h"
	}

	srvID := fmt.Sprintf("dhcp-%s", req.Interface)
	srv := DHCPServerInstance{
		ID:            srvID,
		Name:          fmt.Sprintf("dhcp-%s", req.Interface),
		Interface:     req.Interface,
		AddressPool:   req.AddressPool,
		LeaseTime:     req.LeaseTime,
		Authoritative: true,
		Disabled:      false,
		Comment:       "Created by DHCP Setup Wizard",
	}
	sm.servers[srvID] = srv

	netID := fmt.Sprintf("net-%s", strings.ReplaceAll(req.AddressSpace, "/", "_"))
	netw := DHCPNetwork{
		ID:           netID,
		Address:      req.AddressSpace,
		Gateway:      req.Gateway,
		DNSServers:   req.DNSServers,
		Domain:       req.Domain,
		NTPServers:   req.NTPServers,
		NextServer:   req.NextServer,
		BootFileName: req.BootFileName,
		Comment:      fmt.Sprintf("Network for %s", req.Interface),
	}
	sm.networks[netID] = netw

	if err := sm.saveLocked(); err != nil {
		return err
	}

	return sm.applyDnsmasqConfigLocked()
}

// ======================== SUMMARY ========================
func (sm *ServerManager) GetSummary() DHCPServerSummary {
	sm.mu.RLock()
	defer sm.mu.RUnlock()

	summary := DHCPServerSummary{
		TotalServers:  len(sm.servers),
		TotalNetworks: len(sm.networks),
		StaticLeases:  len(sm.staticLeases),
		TotalOptions:  len(sm.options),
	}

	for _, s := range sm.servers {
		if !s.Disabled && isInterfaceUp(s.Interface) {
			summary.ActiveServers++
		}
	}

	leases := sm.readDnsmasqLeasesFile()
	summary.ActiveLeases = len(leases)

	return summary
}

// ======================== HELPERS ========================
func sanitizeTag(name string) string {
	res := strings.Map(func(r rune) rune {
		if (r >= 'a' && r <= 'z') || (r >= 'A' && r <= 'Z') || (r >= '0' && r <= '9') || r == '_' {
			return r
		}
		return '_'
	}, name)
	return strings.ToLower(res)
}

func parseAddressPool(pool string) (startIP, endIP, netmask string) {
	pool = strings.TrimSpace(pool)
	parts := strings.Split(pool, "-")
	if len(parts) == 2 {
		return strings.TrimSpace(parts[0]), strings.TrimSpace(parts[1]), ""
	}
	return "", "", ""
}

func isInterfaceUp(ifaceName string) bool {
	iface, err := net.InterfaceByName(ifaceName)
	if err != nil {
		return false
	}
	return (iface.Flags & net.FlagUp) != 0
}

func compareIPs(a, b net.IP) int {
	a4 := a.To4()
	b4 := b.To4()
	if a4 == nil || b4 == nil {
		return 0
	}
	for i := 0; i < 4; i++ {
		if a4[i] < b4[i] {
			return -1
		}
		if a4[i] > b4[i] {
			return 1
		}
	}
	return 0
}