package routing

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

	"github.com/vishvananda/netlink"
)

const (
	StaticRoutesStorePath = "/etc/debtik/routing/static_routes.json"
	PolicyRulesStorePath  = "/etc/debtik/routing/policy_rules.json"
	CustomTablesStorePath = "/etc/debtik/routing/custom_tables.json"
	RTTableFilePath       = "/etc/iproute2/rt_tables"
)

type RoutingManager struct {
	mu           sync.Mutex
	staticRoutes []RouteItem
	policyRules  []PolicyRuleItem
	customTables []RoutingTableItem
	stopChan     chan struct{}
}

func NewRoutingManager() *RoutingManager {
	m := &RoutingManager{
		staticRoutes: make([]RouteItem, 0),
		policyRules:  make([]PolicyRuleItem, 0),
		customTables: make([]RoutingTableItem, 0),
		stopChan:     make(chan struct{}),
	}
	m.initRTTableFile()
	m.load()
	m.syncCustomTablesToSystem()
	m.applyAll()
	m.startHealthCheckWorker()
	m.startRouteSyncWorker()
	return m
}

func (m *RoutingManager) initRTTableFile() {
	_ = os.MkdirAll(filepath.Dir(RTTableFilePath), 0755)
	if _, err := os.Stat(RTTableFilePath); os.IsNotExist(err) {
		// Copy from /usr/share/iproute2/rt_tables or seed default
		content, err := os.ReadFile("/usr/share/iproute2/rt_tables")
		if err == nil {
			_ = os.WriteFile(RTTableFilePath, content, 0644)
		} else {
			defaultContent := "# reserved values\n255\tlocal\n254\tmain\n253\tdefault\n0\tunspec\n"
			_ = os.WriteFile(RTTableFilePath, []byte(defaultContent), 0644)
		}
	}
}

func (m *RoutingManager) load() {
	if data, err := os.ReadFile(StaticRoutesStorePath); err == nil {
		_ = json.Unmarshal(data, &m.staticRoutes)
	}
	if data, err := os.ReadFile(PolicyRulesStorePath); err == nil {
		_ = json.Unmarshal(data, &m.policyRules)
	}
	if data, err := os.ReadFile(CustomTablesStorePath); err == nil {
		_ = json.Unmarshal(data, &m.customTables)
	}
	for i := range m.staticRoutes {
		if !m.staticRoutes[i].Disabled && m.staticRoutes[i].HealthStatus != "offline" {
			m.staticRoutes[i].Active = true
		}
	}
}

func (m *RoutingManager) save() error {
	_ = os.MkdirAll("/etc/debtik/routing", 0755)

	if data, err := json.MarshalIndent(m.staticRoutes, "", "  "); err != nil {
		return err
	} else if err = os.WriteFile(StaticRoutesStorePath, data, 0600); err != nil {
		return err
	}
	if data, err := json.MarshalIndent(m.policyRules, "", "  "); err != nil {
		return err
	} else if err = os.WriteFile(PolicyRulesStorePath, data, 0600); err != nil {
		return err
	}
	if data, err := json.MarshalIndent(m.customTables, "", "  "); err != nil {
		return err
	} else if err = os.WriteFile(CustomTablesStorePath, data, 0600); err != nil {
		return err
	}
	return nil
}

func (m *RoutingManager) syncCustomTablesToSystem() {
	content, _ := os.ReadFile(RTTableFilePath)
	str := string(content)

	var sb strings.Builder
	sb.WriteString(str)

	for _, t := range m.customTables {
		check := fmt.Sprintf("\t%s", t.Name)
		if !strings.Contains(str, check) {
			sb.WriteString(fmt.Sprintf("%d\t%s\n", t.TableID, t.Name))
		}
	}

	_ = os.WriteFile(RTTableFilePath, []byte(sb.String()), 0644)
}

func (m *RoutingManager) cleanRogueDefaultRoutes() {
	hasManagedDefault := false
	for _, r := range m.staticRoutes {
		if normalizeDst(r.DstAddress) == "default" && !r.Disabled {
			hasManagedDefault = true
			break
		}
	}

	if !hasManagedDefault {
		return
	}

	routes, err := netlink.RouteList(nil, netlink.FAMILY_V4)
	if err != nil {
		return
	}

	links, _ := netlink.LinkList()
	linkMap := make(map[int]string)
	for _, l := range links {
		linkMap[l.Attrs().Index] = l.Attrs().Name
	}

	for _, r := range routes {
		if (r.Table == 254 || r.Table == 0) && r.Dst == nil && len(r.MultiPath) == 0 {
			gw := ""
			if r.Gw != nil {
				gw = r.Gw.String()
			}
			ifName := linkMap[r.LinkIndex]
			// If priority is 0 (unmetered route from dhclient or boot) and protocol != RTPROT_STATIC:
			if r.Priority == 0 && int(r.Protocol) != 4 {
				log.Printf("[RouteManager] Removing rogue unmanaged default route: via %s dev %s proto %d", gw, ifName, r.Protocol)
				_ = netlink.RouteDel(&r)
			}
		}
	}
}

func (m *RoutingManager) getTableIDByName(name string) int {
	name = strings.TrimSpace(name)
	if name == "" || name == "main" {
		return 254
	}
	if name == "default" {
		return 253
	}
	if name == "local" {
		return 255
	}
	for id, n := range m.getTableMap() {
		if strings.EqualFold(n, name) {
			return id
		}
	}
	if id, err := strconv.Atoi(name); err == nil {
		return id
	}
	return 254
}

func (m *RoutingManager) startRouteSyncWorker() {
	ticker := time.NewTicker(3 * time.Second)
	go func() {
		for {
			select {
			case <-m.stopChan:
				ticker.Stop()
				return
			case <-ticker.C:
				m.syncAllRoutesWorker()
			}
		}
	}()
}

func (m *RoutingManager) syncAllRoutesWorker() {
	m.mu.Lock()
	defer m.mu.Unlock()

	// Unmanaged routes belong to DHCP, the host or other routing daemons.

	liveRoutes, err := netlink.RouteList(nil, netlink.FAMILY_V4)
	if err != nil {
		return
	}

	type groupKey struct {
		dst   string
		table int
		dist  int
	}

	kernelRouteGroups := make(map[groupKey]bool)
	for _, lr := range liveRoutes {
		dst := "default"
		if lr.Dst != nil {
			dst = lr.Dst.String()
		}
		tbl := lr.Table
		if tbl == 0 {
			tbl = 254
		}
		k := groupKey{dst: normalizeDst(dst), table: tbl, dist: lr.Priority}
		kernelRouteGroups[k] = true
	}

	seen := make(map[groupKey]bool)
	for _, r := range m.staticRoutes {
		if r.Disabled || r.HealthStatus == "offline" {
			continue
		}
		normDst := normalizeDst(r.DstAddress)
		tableID := m.getTableIDByName(r.RoutingTable)
		k := groupKey{dst: normDst, table: tableID, dist: r.Distance}
		if !seen[k] {
			seen[k] = true
			if !kernelRouteGroups[k] {
				log.Printf("[RouteSync] Missing kernel route %s table %s (id %d) metric %d -> Restoring", normDst, r.RoutingTable, tableID, r.Distance)
				if err := m.syncRouteGroupToKernel(r.DstAddress, r.RoutingTable, r.Distance); err != nil {
					log.Printf("route synchronization failed: %v", err)
				}
			}
		}
	}
}

func (m *RoutingManager) applyAll() {
	// Unmanaged routes belong to DHCP, the host or other routing daemons.

	// Apply all static routes grouped by (dst, table, distance) for ECMP
	type groupKey struct {
		dst   string
		table string
		dist  int
	}
	seen := make(map[groupKey]bool)
	for _, r := range m.staticRoutes {
		normDst := normalizeDst(r.DstAddress)
		tbl := strings.TrimSpace(r.RoutingTable)
		if tbl == "" {
			tbl = "main"
		}
		k := groupKey{dst: normDst, table: tbl, dist: r.Distance}
		if !seen[k] {
			seen[k] = true
			_ = m.syncRouteGroupToKernel(r.DstAddress, r.RoutingTable, r.Distance)
		}
	}

	// Apply policy rules
	for _, pr := range m.policyRules {
		_ = m.applyRuleToKernel(pr)
	}
}

// ==================== Routes (/ip route) ====================

func isDynamicProtocol(proto netlink.RouteProtocol) bool {
	switch int(proto) {
	case 11, // RTPROT_ZEBRA
		12,  // RTPROT_BIRD
		16,  // RTPROT_DHCP
		42,  // RTPROT_BABEL
		186, // RTPROT_BGP
		187, // RTPROT_ISIS
		188, // RTPROT_OSPF
		189, // RTPROT_RIP
		192: // RTPROT_EIGRP
		return true
	default:
		return false
	}
}

func getRouteProtocolName(proto netlink.RouteProtocol, priority int, isDirect bool, isMulticast bool) string {
	if isMulticast {
		return "multicast"
	}
	switch int(proto) {
	case 16:
		return "dhcp"
	case 4:
		return "static"
	case 186:
		return "bgp"
	case 188:
		return "ospf"
	case 189:
		return "rip"
	case 11:
		return "zebra"
	case 42:
		return "babel"
	case 12: // RTPROT_BIRD
		if priority == 20 {
			return "bgp"
		} else if priority == 200 {
			return "ibgp"
		} else if priority == 110 {
			return "ospf"
		} else if priority == 120 {
			return "rip"
		}
		return "bgp"
	case 2:
		return "connected"
	case 3:
		return "boot"
	default:
		if isDirect {
			return "connected"
		}
		if priority == 20 {
			return "bgp"
		} else if priority == 200 {
			return "ibgp"
		} else if priority == 110 {
			return "ospf"
		} else if priority == 120 {
			return "rip"
		}
		return "static"
	}
}

func (m *RoutingManager) listLiveRoutesLocked() []RouteItem {
	tableNames := m.getTableMap()
	links, _ := netlink.LinkList()
	linkMap := make(map[int]string)
	for _, l := range links {
		linkMap[l.Attrs().Index] = l.Attrs().Name
	}

	var liveRoutes []RouteItem
	routes, err := netlink.RouteList(nil, netlink.FAMILY_V4)
	if err == nil {
		for _, r := range routes {
			dst := "0.0.0.0/0"
			if r.Dst != nil {
				dst = r.Dst.String()
			}
			gw := ""
			if r.Gw != nil {
				gw = r.Gw.String()
			}

			tableName := "main"
			if name, ok := tableNames[r.Table]; ok {
				tableName = name
			} else if r.Table != 254 && r.Table != 0 {
				tableName = strconv.Itoa(r.Table)
			}

			isDyn := isDynamicProtocol(r.Protocol)
			isDirect := (r.Scope == netlink.SCOPE_LINK || r.Protocol == netlink.RouteProtocol(2)) && !isDyn && r.Protocol != 4
			isStatic := !isDirect && !isDyn
			isMulticast := r.Type == 5 || strings.HasPrefix(dst, "224.") || strings.HasPrefix(dst, "ff") || dst == "224.0.0.0/4"
			protoName := getRouteProtocolName(r.Protocol, r.Priority, isDirect, isMulticast)

			if len(r.MultiPath) > 0 {
				for _, nh := range r.MultiPath {
					nhGw := ""
					if nh.Gw != nil {
						nhGw = nh.Gw.String()
					}
					nhIfName := linkMap[nh.LinkIndex]
					cleanDst := strings.ReplaceAll(dst, "/", "_")
					cleanGw := nhGw
					if cleanGw == "" {
						cleanGw = nhIfName
					}
					routeID := fmt.Sprintf("kr-%d-%s-%s", r.Table, cleanDst, cleanGw)

					liveRoutes = append(liveRoutes, RouteItem{
						ID:           routeID,
						DstAddress:   dst,
						Gateway:      nhGw,
						Interface:    nhIfName,
						Distance:     r.Priority,
						Protocol:     protoName,
						RoutingTable: tableName,
						TableID:      r.Table,
						Active:       true,
						Connect:      isDirect,
						Dynamic:      isDyn,
						Static:       isStatic,
						ECMP:         true,
						IsMultiPath:  true,
						Multicast:    isMulticast,
						Disabled:     false,
					})
				}
				continue
			}

			ifName := linkMap[r.LinkIndex]
			act := "lookup"
			if r.Type == 6 { // RTN_BLACKHOLE
				gw = "blackhole"
				act = "blackhole"
			}

			cleanDst := strings.ReplaceAll(dst, "/", "_")
			cleanGw := gw
			if cleanGw == "" {
				cleanGw = ifName
			}
			routeID := fmt.Sprintf("kr-%d-%s-%s", r.Table, cleanDst, cleanGw)

			liveRoutes = append(liveRoutes, RouteItem{
				ID:           routeID,
				DstAddress:   dst,
				Gateway:      gw,
				Action:       act,
				Interface:    ifName,
				Distance:     r.Priority,
				Protocol:     protoName,
				RoutingTable: tableName,
				TableID:      r.Table,
				Active:       true,
				Connect:      isDirect,
				Dynamic:      isDyn,
				Static:       isStatic,
				Multicast:    isMulticast,
				Disabled:     false,
			})
		}
	}
	return liveRoutes
}

func (m *RoutingManager) ListRoutes() []RouteItem {
	m.mu.Lock()
	defer m.mu.Unlock()

	liveRoutes := m.listLiveRoutesLocked()

	// Merge static routes that might be disabled or have custom metadata
	for _, sr := range m.staticRoutes {
		found := false
		for i, lr := range liveRoutes {
			if lr.DstAddress == sr.DstAddress && lr.RoutingTable == sr.RoutingTable && (sr.Gateway == "" || lr.Gateway == sr.Gateway) {
				liveRoutes[i].Comment = sr.Comment
				liveRoutes[i].Static = true
				liveRoutes[i].Dynamic = false
				liveRoutes[i].Protocol = "static"
				liveRoutes[i].ID = sr.ID
				if sr.Distance > 0 && liveRoutes[i].Distance == 0 {
					liveRoutes[i].Distance = sr.Distance
				}
				liveRoutes[i].CheckGateway = sr.CheckGateway
				liveRoutes[i].CheckTarget = sr.CheckTarget
				liveRoutes[i].CheckInterval = sr.CheckInterval
				liveRoutes[i].CheckThreshold = sr.CheckThreshold
				liveRoutes[i].HealthStatus = sr.HealthStatus
				liveRoutes[i].HealthRTT = sr.HealthRTT
				liveRoutes[i].HealthLossPct = sr.HealthLossPct
				liveRoutes[i].HealthFailCount = sr.HealthFailCount
				liveRoutes[i].HealthLastCheck = sr.HealthLastCheck
				found = true
				break
			}
		}
		if !found {
			// Inactive or disabled static route
			srCopy := sr
			srCopy.Active = false
			srCopy.Static = true
			srCopy.Dynamic = false
			srCopy.Protocol = "static"
			liveRoutes = append(liveRoutes, srCopy)
		}
	}

	// Detect Equal-Cost Multi-Path (ECMP) routes
	groupCounts := make(map[string]int)
	for _, r := range liveRoutes {
		if r.Active && !r.Disabled {
			key := fmt.Sprintf("%s|%s|%d", r.DstAddress, r.RoutingTable, r.Distance)
			groupCounts[key]++
		}
	}

	for i := range liveRoutes {
		key := fmt.Sprintf("%s|%s|%d", liveRoutes[i].DstAddress, liveRoutes[i].RoutingTable, liveRoutes[i].Distance)
		if liveRoutes[i].IsMultiPath || (liveRoutes[i].Active && !liveRoutes[i].Disabled && groupCounts[key] > 1) {
			liveRoutes[i].ECMP = true
		}
		if liveRoutes[i].DstAddress == "224.0.0.0/4" || strings.HasPrefix(liveRoutes[i].DstAddress, "224.") || strings.HasPrefix(liveRoutes[i].DstAddress, "ff") {
			liveRoutes[i].Multicast = true
		}
	}

	sort.Slice(liveRoutes, func(i, j int) bool {
		if liveRoutes[i].RoutingTable != liveRoutes[j].RoutingTable {
			return liveRoutes[i].RoutingTable < liveRoutes[j].RoutingTable
		}
		if liveRoutes[i].DstAddress != liveRoutes[j].DstAddress {
			return liveRoutes[i].DstAddress < liveRoutes[j].DstAddress
		}
		return liveRoutes[i].Gateway < liveRoutes[j].Gateway
	})

	return liveRoutes
}

func (m *RoutingManager) SaveRoute(r RouteItem) (err error) {
	m.mu.Lock()
	defer m.mu.Unlock()
	before := append([]RouteItem(nil), m.staticRoutes...)
	dirty, applied := false, false
	defer func() {
		if err != nil && dirty {
			m.staticRoutes = before
			if applied {
				_ = m.syncRouteGroupToKernel(r.DstAddress, r.RoutingTable, r.Distance)
			}
			m.applyAll()
			_ = m.save()
		}
	}()

	if r.DstAddress == "" {
		return fmt.Errorf("destination address is required")
	}
	if r.DstAddress == "default" {
		r.DstAddress = "0.0.0.0/0"
	}
	if r.RoutingTable == "" {
		r.RoutingTable = "main"
	}
	if _, _, parseErr := net.ParseCIDR(r.DstAddress); parseErr != nil && net.ParseIP(r.DstAddress) == nil {
		return fmt.Errorf("invalid destination: %s", r.DstAddress)
	}
	dirty = true
	r.Static = true

	// 1. If old route details are provided from edit modal, remove old route first
	if r.OldDstAddress != "" {
		oldDist := 0
		if r.OldDistance != nil {
			oldDist = *r.OldDistance
		}
		oldRoute := RouteItem{
			DstAddress:   r.OldDstAddress,
			Gateway:      r.OldGateway,
			RoutingTable: r.OldRoutingTable,
			Distance:     oldDist,
			Interface:    r.OldInterface,
		}
		_ = m.removeRouteFromKernel(oldRoute)
	}

	// 2. If existing entry in m.staticRoutes exists, remove its old route from kernel
	foundIndex := -1
	for i, existing := range m.staticRoutes {
		matchByID := r.ID != "" && existing.ID == r.ID
		matchByExactParams := r.ID == "" &&
			normalizeDst(existing.DstAddress) == normalizeDst(r.DstAddress) &&
			existing.RoutingTable == r.RoutingTable &&
			existing.Gateway == r.Gateway &&
			existing.Interface == r.Interface &&
			existing.Distance == r.Distance

		if matchByID || matchByExactParams {
			foundIndex = i
			_ = m.removeRouteFromKernel(existing)
			break
		}
	}

	// 3. If r.ID starts with kr- (kernel static route being edited/adopted), remove it from kernel
	if strings.HasPrefix(r.ID, "kr-") {
		for _, lr := range m.listLiveRoutesLocked() {
			if lr.ID == r.ID {
				_ = m.removeRouteFromKernel(lr)
				break
			}
		}
		r.ID = fmt.Sprintf("route-%d", time.Now().UnixNano())
	}

	if r.ID == "" {
		r.ID = fmt.Sprintf("route-%d", time.Now().UnixNano())
	}

	if r.CheckInterval <= 0 {
		r.CheckInterval = 5
	}
	if r.CheckThreshold <= 0 {
		r.CheckThreshold = 3
	}
	if r.CheckGateway == "internet" && strings.TrimSpace(r.CheckTarget) == "" {
		r.CheckTarget = "1.1.1.1"
	}
	if r.CheckGateway != "" && r.CheckGateway != "none" {
		if r.HealthStatus == "" {
			r.HealthStatus = "checking"
		}
	} else {
		r.CheckGateway = "none"
		r.HealthStatus = "none"
	}

	if foundIndex >= 0 {
		if r.HealthStatus == "checking" && m.staticRoutes[foundIndex].HealthStatus != "" && m.staticRoutes[foundIndex].CheckGateway == r.CheckGateway {
			r.HealthStatus = m.staticRoutes[foundIndex].HealthStatus
			r.HealthRTT = m.staticRoutes[foundIndex].HealthRTT
			r.HealthLossPct = m.staticRoutes[foundIndex].HealthLossPct
			r.HealthLastCheck = m.staticRoutes[foundIndex].HealthLastCheck
		}
		m.staticRoutes[foundIndex] = r
	} else {
		m.staticRoutes = append(m.staticRoutes, r)
	}

	for i := range m.staticRoutes {
		if m.staticRoutes[i].ID == r.ID {
			if !m.staticRoutes[i].Disabled && m.staticRoutes[i].HealthStatus != "offline" {
				m.staticRoutes[i].Active = true
			} else {
				m.staticRoutes[i].Active = false
			}
			break
		}
	}

	if saveErr := m.save(); saveErr != nil {
		return saveErr
	}

	if err := m.syncRouteGroupToKernel(r.DstAddress, r.RoutingTable, r.Distance); err != nil {
		return err
	}
	applied = true
	if r.OldDstAddress != "" {
		oldDist := 0
		if r.OldDistance != nil {
			oldDist = *r.OldDistance
		}
		if r.OldDstAddress != r.DstAddress || r.OldRoutingTable != r.RoutingTable || oldDist != r.Distance {
			if err := m.syncRouteGroupToKernel(r.OldDstAddress, r.OldRoutingTable, oldDist); err != nil {
				return err
			}
		}
	}

	return nil
}

func (m *RoutingManager) DeleteRoute(id string) error {
	m.mu.Lock()
	defer m.mu.Unlock()

	var updated []RouteItem
	var target *RouteItem
	for _, r := range m.staticRoutes {
		if r.ID == id {
			target = &r
		} else {
			updated = append(updated, r)
		}
	}

	if target != nil {
		m.staticRoutes = updated
		_ = m.save()
		_ = m.syncRouteGroupToKernel(target.DstAddress, target.RoutingTable, target.Distance)
		return nil
	}

	// If not in staticRoutes, could be a live route (e.g. kr-...)
	for _, lr := range m.listLiveRoutesLocked() {
		if lr.ID == id {
			_ = m.removeRouteFromKernel(lr)
			return nil
		}
	}

	return fmt.Errorf("route not found")
}

func (m *RoutingManager) SetRouteState(id string, disabled bool) error {
	m.mu.Lock()
	defer m.mu.Unlock()

	for i := range m.staticRoutes {
		if m.staticRoutes[i].ID == id {
			m.staticRoutes[i].Disabled = disabled
			if !disabled && m.staticRoutes[i].HealthStatus != "offline" {
				m.staticRoutes[i].Active = true
			} else if disabled {
				m.staticRoutes[i].Active = false
			}
			_ = m.save()
			_ = m.syncRouteGroupToKernel(m.staticRoutes[i].DstAddress, m.staticRoutes[i].RoutingTable, m.staticRoutes[i].Distance)
			return nil
		}
	}

	// If not in staticRoutes, could be a kernel static route to disable
	if disabled {
		for _, lr := range m.listLiveRoutesLocked() {
			if lr.ID == id {
				lr.Disabled = true
				lr.Static = true
				lr.Active = false
				lr.ID = fmt.Sprintf("route-%d", time.Now().UnixNano())
				m.staticRoutes = append(m.staticRoutes, lr)
				_ = m.save()
				_ = m.syncRouteGroupToKernel(lr.DstAddress, lr.RoutingTable, lr.Distance)
				return nil
			}
		}
	}

	return fmt.Errorf("route not found")
}

func normalizeDst(dst string) string {
	dst = strings.TrimSpace(dst)
	if dst == "" || dst == "default" || dst == "0.0.0.0/0" {
		return "default"
	}
	if !strings.Contains(dst, "/") && net.ParseIP(dst) != nil {
		return dst + "/32"
	}
	return dst
}

func (m *RoutingManager) syncRouteGroupToKernel(dstAddress, routingTable string, distance int) error {
	normDst := normalizeDst(dstAddress)
	tbl := strings.TrimSpace(routingTable)
	if tbl == "" {
		tbl = "main"
	}

	var activeRoutes []RouteItem
	for _, r := range m.staticRoutes {
		rDst := normalizeDst(r.DstAddress)
		rTbl := strings.TrimSpace(r.RoutingTable)
		if rTbl == "" {
			rTbl = "main"
		}
		if rDst == normDst && rTbl == tbl && r.Distance == distance {
			if !r.Disabled && r.Active && r.HealthStatus != "offline" {
				activeRoutes = append(activeRoutes, r)
			}
		}
	}

	if len(activeRoutes) == 0 {
		// Safety guard: if all default routes are marked offline, do NOT delete the default route into a blackout!
		// Fallback to keeping all enabled static routes in the group active so recovery traffic and emergency pings can flow.
		if normDst == "default" {
			var fallbackRoutes []RouteItem
			for _, r := range m.staticRoutes {
				rDst := normalizeDst(r.DstAddress)
				rTbl := strings.TrimSpace(r.RoutingTable)
				if rTbl == "" {
					rTbl = "main"
				}
				if rDst == normDst && rTbl == tbl && r.Distance == distance && !r.Disabled {
					fallbackRoutes = append(fallbackRoutes, r)
				}
			}
			if len(fallbackRoutes) > 0 {
				log.Printf("[RouteManager] All default routes offline in group! Keeping fallback routes active to prevent blackout")
				activeRoutes = fallbackRoutes
			}
		}
	}

	if len(activeRoutes) == 0 {
		args := []string{"route", "del", normDst}
		if distance > 0 {
			args = append(args, "metric", strconv.Itoa(distance))
		}
		if tbl != "main" {
			args = append(args, "table", tbl)
		}
		args = append(args, "proto", "static")
		_ = exec.Command("ip", args...).Run()

		// Also delete blackhole route variant if it existed
		bhArgs := []string{"route", "del", "blackhole", normDst}
		if distance > 0 {
			bhArgs = append(bhArgs, "metric", strconv.Itoa(distance))
		}
		if tbl != "main" {
			bhArgs = append(bhArgs, "table", tbl)
		}
		_ = exec.Command("ip", bhArgs...).Run()
		return nil
	}

	if len(activeRoutes) == 1 {
		r := activeRoutes[0]
		gw := strings.TrimSpace(r.Gateway)
		isBlackhole := strings.EqualFold(gw, "blackhole") || strings.EqualFold(r.Action, "blackhole")

		var args []string
		if isBlackhole {
			args = []string{"route", "replace", "blackhole", normDst}
		} else {
			args = []string{"route", "replace", normDst}
			if gw != "" {
				if net.ParseIP(gw) != nil {
					args = append(args, "via", gw)
				} else {
					args = append(args, "dev", gw)
				}
			}
			iface := strings.TrimSpace(r.Interface)
			if iface != "" && gw != iface && (gw == "" || net.ParseIP(gw) != nil) {
				args = append(args, "dev", iface)
			}
			if gw != "" && iface != "" && net.ParseIP(gw) != nil {
				args = append(args, "onlink")
			}
		}
		if distance > 0 {
			args = append(args, "metric", strconv.Itoa(distance))
		}
		if tbl != "main" {
			args = append(args, "table", tbl)
		}
		args = append(args, "proto", "static")

		cmd := exec.Command("ip", args...)
		if out, err := cmd.CombinedOutput(); err != nil {
			return fmt.Errorf("failed to apply route (%s): %s: %w", strings.Join(args, " "), string(out), err)
		}
		return nil
	}

	// Multiple routes: ECMP multipath route
	args := []string{"route", "replace", normDst, "scope", "global"}
	if distance > 0 {
		args = append(args, "metric", strconv.Itoa(distance))
	}
	if tbl != "main" {
		args = append(args, "table", tbl)
	}
	args = append(args, "proto", "static")

	for _, r := range activeRoutes {
		args = append(args, "nexthop")
		gw := strings.TrimSpace(r.Gateway)
		if gw != "" && net.ParseIP(gw) != nil {
			args = append(args, "via", gw)
		}
		iface := strings.TrimSpace(r.Interface)
		if iface == "" && gw != "" && net.ParseIP(gw) == nil {
			iface = gw
		}
		if iface != "" {
			args = append(args, "dev", iface)
		}
		if gw != "" && iface != "" && net.ParseIP(gw) != nil {
			args = append(args, "onlink")
		}
		args = append(args, "weight", "1")
	}

	cmd := exec.Command("ip", args...)
	if out, err := cmd.CombinedOutput(); err != nil {
		return fmt.Errorf("failed to apply multipath route (%s): %s: %w", strings.Join(args, " "), string(out), err)
	}
	return nil
}

func (m *RoutingManager) applyRouteToKernel(r RouteItem) error {
	return m.syncRouteGroupToKernel(r.DstAddress, r.RoutingTable, r.Distance)
}

func (m *RoutingManager) removeRouteFromKernel(r RouteItem) error {
	return m.syncRouteGroupToKernel(r.DstAddress, r.RoutingTable, r.Distance)
}

// ==================== Policy Rules (/ip route rule) ====================

func (m *RoutingManager) ListPolicyRules() []PolicyRuleItem {
	m.mu.Lock()
	defer m.mu.Unlock()

	// Query live rules from kernel
	rules, err := netlink.RuleList(netlink.FAMILY_V4)
	if err != nil {
		return m.policyRules
	}

	tableNames := m.getTableMap()
	var res []PolicyRuleItem

	userRulesByPrio := make(map[int]PolicyRuleItem)
	for _, pr := range m.policyRules {
		userRulesByPrio[pr.Priority] = pr
	}

	for _, r := range rules {
		tableName := "main"
		if name, ok := tableNames[r.Table]; ok {
			tableName = name
		} else if r.Table != 254 && r.Table != 0 {
			tableName = strconv.Itoa(r.Table)
		}

		src := ""
		if r.Src != nil {
			src = r.Src.String()
		}
		dst := ""
		if r.Dst != nil {
			dst = r.Dst.String()
		}

		markStr := ""
		if r.Mark > 0 {
			markStr = fmt.Sprintf("0x%x (%d)", r.Mark, r.Mark)
		}

		id := fmt.Sprintf("rule-%d-%d", r.Priority, r.Table)
		comment := ""
		isDefault := false
		isSystem := false

		if r.Priority == 0 || r.Priority == 32766 || r.Priority == 32767 {
			isDefault = true
			isSystem = true
		} else if userRule, ok := userRulesByPrio[r.Priority]; ok {
			if userRule.ID != "" {
				id = userRule.ID
			}
			comment = userRule.Comment
			isDefault = false
			isSystem = false
		} else {
			// System/daemon rule not added by user in debtik (e.g. WireGuard, IPsec)
			isSystem = true
		}

		res = append(res, PolicyRuleItem{
			ID:          id,
			Priority:    r.Priority,
			SrcAddress:  src,
			DstAddress:  dst,
			RoutingMark: markStr,
			Table:       tableName,
			TableID:     r.Table,
			Action:      "lookup",
			Comment:     comment,
			IsDefault:   isDefault,
			IsSystem:    isSystem,
		})
	}

	return res
}

func (m *RoutingManager) SavePolicyRule(pr PolicyRuleItem) error {
	m.mu.Lock()
	defer m.mu.Unlock()

	if pr.Table == "" {
		pr.Table = "main"
	}
	if pr.ID == "" {
		pr.ID = fmt.Sprintf("prule-%d", time.Now().UnixNano())
	}
	if pr.Priority == 0 {
		pr.Priority = 1000 + len(m.policyRules)*10
	}

	if err := m.applyRuleToKernel(pr); err != nil {
		return err
	}

	m.policyRules = append(m.policyRules, pr)
	return m.save()
}

func (m *RoutingManager) DeletePolicyRule(id string) error {
	m.mu.Lock()
	defer m.mu.Unlock()

	var updated []PolicyRuleItem
	var target *PolicyRuleItem
	for _, pr := range m.policyRules {
		if pr.ID == id || fmt.Sprintf("rule-%d-%d", pr.Priority, pr.TableID) == id {
			target = &pr
		} else {
			updated = append(updated, pr)
		}
	}

	if target != nil {
		_ = m.removeRuleFromKernel(*target)
	} else if strings.HasPrefix(id, "rule-") {
		parts := strings.Split(id, "-")
		if len(parts) >= 2 {
			if prio, err := strconv.Atoi(parts[1]); err == nil && prio > 0 {
				_ = exec.Command("ip", "rule", "del", "pref", strconv.Itoa(prio)).Run()
			}
		}
	}
	m.policyRules = updated
	return m.save()
}

func (m *RoutingManager) applyRuleToKernel(pr PolicyRuleItem) error {
	args := []string{"rule", "add"}
	if pr.Priority > 0 {
		args = append(args, "pref", strconv.Itoa(pr.Priority))
	}
	if pr.SrcAddress != "" {
		args = append(args, "from", pr.SrcAddress)
	}
	if pr.DstAddress != "" {
		args = append(args, "to", pr.DstAddress)
	}
	if pr.RoutingMark != "" {
		// Clean mark string if it has (hex)
		markClean := pr.RoutingMark
		if strings.Contains(markClean, "(") {
			markClean = strings.TrimSpace(markClean[:strings.Index(markClean, "(")])
		}
		args = append(args, "fwmark", markClean)
	}
	if pr.Table != "" {
		args = append(args, "lookup", pr.Table)
	}

	cmd := exec.Command("ip", args...)
	out, err := cmd.CombinedOutput()
	if err != nil {
		return fmt.Errorf("failed to add rule (%s): %s: %w", strings.Join(args, " "), string(out), err)
	}
	return nil
}

func (m *RoutingManager) removeRuleFromKernel(pr PolicyRuleItem) error {
	if pr.Priority > 0 {
		_ = exec.Command("ip", "rule", "del", "pref", strconv.Itoa(pr.Priority)).Run()
		return nil
	}
	args := []string{"rule", "del"}
	if pr.RoutingMark != "" {
		markClean := pr.RoutingMark
		if strings.Contains(markClean, "(") {
			markClean = strings.TrimSpace(markClean[:strings.Index(markClean, "(")])
		}
		args = append(args, "fwmark", markClean)
	}
	if pr.Table != "" {
		args = append(args, "lookup", pr.Table)
	}

	_ = exec.Command("ip", args...).Run()
	return nil
}

// ==================== Routing Tables ====================

func (m *RoutingManager) ListTables() []RoutingTableItem {
	m.mu.Lock()
	defer m.mu.Unlock()

	tables := []RoutingTableItem{
		{Name: "main", TableID: 254, Comment: "Default system routing table"},
		{Name: "default", TableID: 253, Comment: "Default fallback table"},
		{Name: "local", TableID: 255, Comment: "Local kernel device table"},
	}

	tables = append(tables, m.customTables...)
	return tables
}

func (m *RoutingManager) SaveTable(t RoutingTableItem) error {
	m.mu.Lock()
	defer m.mu.Unlock()

	if t.Name == "" {
		return fmt.Errorf("table name is required")
	}
	if t.TableID == 0 {
		// Auto assign FIB ID starting at 100
		t.TableID = 100 + len(m.customTables)
	}

	for _, existing := range m.customTables {
		if existing.Name == t.Name || existing.TableID == t.TableID {
			return fmt.Errorf("table with name %q or ID %d already exists", t.Name, t.TableID)
		}
	}

	m.customTables = append(m.customTables, t)
	_ = m.save()
	m.syncCustomTablesToSystem()
	return nil
}

func (m *RoutingManager) getTableMap() map[int]string {
	tableMap := map[int]string{
		254: "main",
		253: "default",
		255: "local",
	}

	// Read /etc/iproute2/rt_tables
	if f, err := os.Open(RTTableFilePath); err == nil {
		defer f.Close()
		scanner := bufio.NewScanner(f)
		for scanner.Scan() {
			line := strings.TrimSpace(scanner.Text())
			if line == "" || strings.HasPrefix(line, "#") {
				continue
			}
			parts := strings.Fields(line)
			if len(parts) >= 2 {
				if id, err := strconv.Atoi(parts[0]); err == nil {
					tableMap[id] = parts[1]
				}
			}
		}
	}

	for _, t := range m.customTables {
		tableMap[t.TableID] = t.Name
	}

	return tableMap
}

func (m *RoutingManager) Stop() {
	if m.stopChan != nil {
		select {
		case <-m.stopChan:
		default:
			close(m.stopChan)
		}
	}
}

// RenameInterface updates static routes and policy rules when an interface is renamed.
func (m *RoutingManager) RenameInterface(oldName, newName string) {
	m.mu.Lock()
	defer m.mu.Unlock()

	changed := false
	for i := range m.staticRoutes {
		if m.staticRoutes[i].Interface == oldName {
			m.staticRoutes[i].Interface = newName
			changed = true
		}
		if m.staticRoutes[i].Gateway == oldName {
			m.staticRoutes[i].Gateway = newName
			changed = true
		}
	}
	if changed {
		_ = m.save()
	}
}