package api

import (
	"encoding/json"
	"log"
	"net/http"
	"net/url"
	"sort"
	"strconv"
	"strings"
	"time"

	"nettopo-go/internal/scans"
	"nettopo-go/internal/webui"
)

type Handler struct {
	store         scans.Store
	run           *scans.Runner
	resetDBSecret string
}

type LinkView struct {
	SourceIP       string `json:"source_ip"`
	SourcePort     string `json:"source_port"`
	TargetIP       string `json:"target_ip,omitempty"`
	TargetSysName  string `json:"target_sys_name,omitempty"`
	TargetPort     string `json:"target_port,omitempty"`
	RemoteChassis  string `json:"remote_chassis_id,omitempty"`
	ResolvedBy     string `json:"resolved_by"`
}

type TopologyNode struct {
	ID   string `json:"id"`
	IP   string `json:"ip"`
	Name string `json:"name,omitempty"`
}

type TopologyEdge struct {
	SourceIP   string `json:"source_ip"`
	SourcePort string `json:"source_port,omitempty"`
	TargetIP   string `json:"target_ip,omitempty"`
	TargetName string `json:"target_name,omitempty"`
	TargetPort string `json:"target_port,omitempty"`
}

type ScanDiffResponse struct {
	FromScanID    string   `json:"from_scan_id"`
	ToScanID      string   `json:"to_scan_id"`
	NewHosts      []string `json:"new_hosts"`
	MissingHosts  []string `json:"missing_hosts"`
	NewLinks      []string `json:"new_links"`
	MissingLinks  []string `json:"missing_links"`
}

// MacLocationRow — где в FDB найден MAC: коммутатор (ip), порт, клиентский IP из ARP.
type MacLocationRow struct {
	SwitchIP      string    `json:"switch_ip"`
	SwitchSysName string    `json:"switch_sys_name,omitempty"`
	IfIndex       int       `json:"if_index"`
	BridgePort    int       `json:"bridge_port,omitempty"`
	Vlan          int       `json:"vlan"`
	MAC           string    `json:"mac"`
	ClientIP      string    `json:"client_ip,omitempty"`
	ClientName    string    `json:"client_name,omitempty"`
	MacsOnPort    int       `json:"macs_on_port"`
	PortKind      string    `json:"port_kind"` // access | ambiguous | strong_transit
	CheckedAt     time.Time `json:"checked_at"`
}

func NewHandler(store scans.Store, run *scans.Runner, resetDBSecret string) *Handler {
	return &Handler{store: store, run: run, resetDBSecret: strings.TrimSpace(resetDBSecret)}
}

func scanPathID(r *http.Request) string {
	raw := r.PathValue("id")
	if raw == "" {
		return ""
	}
	if dec, err := url.PathUnescape(raw); err == nil {
		return strings.TrimSpace(dec)
	}
	return strings.TrimSpace(raw)
}

func (h *Handler) Routes() http.Handler {
	mux := http.NewServeMux()
	webFS := http.FileServer(http.FS(webui.FS))
	mux.Handle("GET /", webFS)
	mux.Handle("GET /web/", http.StripPrefix("/web/", webFS))
	mux.HandleFunc("GET /health", h.health)
	mux.HandleFunc("POST /api/scans", h.createScan)
	mux.HandleFunc("GET /api/scans", h.listScans)
	mux.HandleFunc("GET /api/scans/diff", h.getScansDiff)
	mux.HandleFunc("GET /api/scans/{id}", h.getScan)
	mux.HandleFunc("POST /api/scans/{id}/cancel", h.postCancelScan)
	mux.HandleFunc("GET /api/scans/{id}/hosts", h.getScanHosts)
	mux.HandleFunc("GET /api/scans/{id}/ports", h.getScanPorts)
	mux.HandleFunc("GET /api/scans/{id}/snmp", h.getScanSNMP)
	mux.HandleFunc("GET /api/scans/{id}/lldp", h.getScanLLDP)
	mux.HandleFunc("GET /api/scans/{id}/interfaces", h.getScanInterfaces)
	mux.HandleFunc("GET /api/scans/{id}/port-devices", h.getScanPortDevices)
	mux.HandleFunc("GET /api/scans/{id}/mac-locations", h.getScanMacLocations)
	mux.HandleFunc("GET /api/scans/{id}/links", h.getScanLinks)
	mux.HandleFunc("GET /api/scans/{id}/topology", h.getScanTopology)
	mux.HandleFunc("POST /api/admin/purge-scans", h.postAdminPurgeScans)
	return withJSON(mux)
}

func (h *Handler) postAdminPurgeScans(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		writeError(w, http.StatusMethodNotAllowed, "use POST")
		return
	}
	if h.resetDBSecret == "" {
		writeError(w, http.StatusForbidden, "purge disabled: set NETTOPO_RESET_DB_SECRET in environment")
		return
	}
	key := strings.TrimSpace(r.Header.Get("X-Nettopo-Reset-Key"))
	if key == "" || key != h.resetDBSecret {
		writeError(w, http.StatusUnauthorized, "invalid or missing X-Nettopo-Reset-Key header")
		return
	}
	if err := h.store.PurgeAllScanData(); err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	writeJSON(w, http.StatusOK, map[string]any{
		"ok":      true,
		"message": "all scan data removed (scan_jobs and related rows)",
	})
}

func (h *Handler) health(w http.ResponseWriter, _ *http.Request) {
	writeJSON(w, http.StatusOK, map[string]any{
		"status": "ok",
		"time":   time.Now().UTC(),
	})
}

func (h *Handler) createScan(w http.ResponseWriter, r *http.Request) {
	var req scans.CreateScanRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "invalid json body")
		return
	}

	req.Name = strings.TrimSpace(req.Name)
	if req.Name == "" {
		req.Name = "manual-scan"
	}

	job, err := h.store.CreateScan(req)
	if err != nil {
		writeError(w, http.StatusBadRequest, err.Error())
		return
	}

	// Start до ответа клиенту: иначе возможен POST /cancel до регистрации cancel в Runner (задача останется queued/running).
	if h.run != nil {
		h.run.Start(job)
	}

	writeJSON(w, http.StatusCreated, map[string]any{
		"scan_id": job.ID,
		"status":  job.Status,
	})
}

func (h *Handler) listScans(w http.ResponseWriter, r *http.Request) {
	limit := 50
	if raw := r.URL.Query().Get("limit"); raw != "" {
		n, err := strconv.Atoi(raw)
		if err != nil || n <= 0 || n > 500 {
			writeError(w, http.StatusBadRequest, "limit must be between 1 and 500")
			return
		}
		limit = n
	}
	writeJSON(w, http.StatusOK, map[string]any{
		"items": h.store.ListScans(limit),
	})
}

func (h *Handler) getScansDiff(w http.ResponseWriter, r *http.Request) {
	fromID := strings.TrimSpace(r.URL.Query().Get("from"))
	toID := strings.TrimSpace(r.URL.Query().Get("to"))
	if fromID == "" || toID == "" {
		writeError(w, http.StatusBadRequest, "both from and to are required")
		return
	}
	if _, ok := h.store.GetScan(fromID); !ok {
		writeError(w, http.StatusNotFound, "from scan not found")
		return
	}
	if _, ok := h.store.GetScan(toID); !ok {
		writeError(w, http.StatusNotFound, "to scan not found")
		return
	}

	fromHosts := hostUpSet(h.store.ListHostResults(fromID, 200000))
	toHosts := hostUpSet(h.store.ListHostResults(toID, 200000))
	fromLinks := linkSet(h.store.ListLLDPResults(fromID, 200000))
	toLinks := linkSet(h.store.ListLLDPResults(toID, 200000))

	resp := ScanDiffResponse{
		FromScanID:   fromID,
		ToScanID:     toID,
		NewHosts:     setDiff(toHosts, fromHosts),
		MissingHosts: setDiff(fromHosts, toHosts),
		NewLinks:     setDiff(toLinks, fromLinks),
		MissingLinks: setDiff(fromLinks, toLinks),
	}
	writeJSON(w, http.StatusOK, resp)
}

func (h *Handler) getScan(w http.ResponseWriter, r *http.Request) {
	id := scanPathID(r)
	if id == "" {
		writeError(w, http.StatusBadRequest, "scan id is required")
		return
	}

	job, ok := h.store.GetScan(id)
	if !ok {
		log.Printf("getScan: not found id=%q (len=%d)", id, len(id))
		writeError(w, http.StatusNotFound, "scan not found")
		return
	}

	writeJSON(w, http.StatusOK, job)
}

func (h *Handler) postCancelScan(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		writeError(w, http.StatusMethodNotAllowed, "use POST")
		return
	}
	id := scanPathID(r)
	if id == "" {
		writeError(w, http.StatusBadRequest, "scan id is required")
		return
	}
	if _, ok := h.store.GetScan(id); !ok {
		log.Printf("postCancelScan: not found id=%q (len=%d)", id, len(id))
		writeError(w, http.StatusNotFound, "scan not found")
		return
	}
	runnerSignaled := false
	if h.run != nil {
		runnerSignaled = h.run.CancelScan(id)
	}
	if runnerSignaled {
		writeJSON(w, http.StatusOK, map[string]any{"ok": true, "runner_canceled": true})
		return
	}
	cur, _ := h.store.GetScan(id)
	if cur.Status == "queued" {
		fin := time.Now().UTC()
		_, _ = h.store.UpdateScan(id, scans.ScanUpdate{Status: "canceled", FinishedAt: &fin})
		writeJSON(w, http.StatusOK, map[string]any{"ok": true, "runner_canceled": false, "status": "canceled"})
		return
	}
	writeJSON(w, http.StatusOK, map[string]any{"ok": true, "runner_canceled": false})
}

func (h *Handler) getScanHosts(w http.ResponseWriter, r *http.Request) {
	id := scanPathID(r)
	if id == "" {
		writeError(w, http.StatusBadRequest, "scan id is required")
		return
	}
	if _, ok := h.store.GetScan(id); !ok {
		writeError(w, http.StatusNotFound, "scan not found")
		return
	}

	limit := 200000
	if raw := r.URL.Query().Get("limit"); raw != "" {
		n, err := strconv.Atoi(raw)
		if err != nil || n <= 0 || n > 500000 {
			writeError(w, http.StatusBadRequest, "limit must be between 1 and 500000")
			return
		}
		limit = n
	}

	writeJSON(w, http.StatusOK, map[string]any{
		"items": h.store.ListHostResults(id, limit),
	})
}

func (h *Handler) getScanPorts(w http.ResponseWriter, r *http.Request) {
	id := scanPathID(r)
	if id == "" {
		writeError(w, http.StatusBadRequest, "scan id is required")
		return
	}
	if _, ok := h.store.GetScan(id); !ok {
		writeError(w, http.StatusNotFound, "scan not found")
		return
	}

	limit := 1000
	if raw := r.URL.Query().Get("limit"); raw != "" {
		n, err := strconv.Atoi(raw)
		if err != nil || n <= 0 || n > 10000 {
			writeError(w, http.StatusBadRequest, "limit must be between 1 and 10000")
			return
		}
		limit = n
	}

	writeJSON(w, http.StatusOK, map[string]any{
		"items": h.store.ListOpenPortResults(id, limit),
	})
}

func (h *Handler) getScanSNMP(w http.ResponseWriter, r *http.Request) {
	id := scanPathID(r)
	if id == "" {
		writeError(w, http.StatusBadRequest, "scan id is required")
		return
	}
	if _, ok := h.store.GetScan(id); !ok {
		writeError(w, http.StatusNotFound, "scan not found")
		return
	}

	limit := 200000
	if raw := r.URL.Query().Get("limit"); raw != "" {
		n, err := strconv.Atoi(raw)
		if err != nil || n <= 0 || n > 500000 {
			writeError(w, http.StatusBadRequest, "limit must be between 1 and 500000")
			return
		}
		limit = n
	}

	writeJSON(w, http.StatusOK, map[string]any{
		"items": h.store.ListSNMPResults(id, limit),
	})
}

func (h *Handler) getScanLLDP(w http.ResponseWriter, r *http.Request) {
	id := scanPathID(r)
	if id == "" {
		writeError(w, http.StatusBadRequest, "scan id is required")
		return
	}
	if _, ok := h.store.GetScan(id); !ok {
		writeError(w, http.StatusNotFound, "scan not found")
		return
	}

	limit := 2000
	if raw := r.URL.Query().Get("limit"); raw != "" {
		n, err := strconv.Atoi(raw)
		if err != nil || n <= 0 || n > 20000 {
			writeError(w, http.StatusBadRequest, "limit must be between 1 and 20000")
			return
		}
		limit = n
	}

	writeJSON(w, http.StatusOK, map[string]any{
		"items": h.store.ListLLDPResults(id, limit),
	})
}

func (h *Handler) getScanInterfaces(w http.ResponseWriter, r *http.Request) {
	id := scanPathID(r)
	if id == "" {
		writeError(w, http.StatusBadRequest, "scan id is required")
		return
	}
	if _, ok := h.store.GetScan(id); !ok {
		writeError(w, http.StatusNotFound, "scan not found")
		return
	}
	ip := strings.TrimSpace(r.URL.Query().Get("ip"))
	if ip == "" {
		writeError(w, http.StatusBadRequest, "query parameter ip is required")
		return
	}
	limit := 4096
	if raw := r.URL.Query().Get("limit"); raw != "" {
		n, err := strconv.Atoi(raw)
		if err != nil || n <= 0 || n > 10000 {
			writeError(w, http.StatusBadRequest, "limit must be between 1 and 10000")
			return
		}
		limit = n
	}
	writeJSON(w, http.StatusOK, map[string]any{
		"items": h.store.ListInterfaceResults(id, ip, limit),
	})
}

func (h *Handler) getScanPortDevices(w http.ResponseWriter, r *http.Request) {
	id := scanPathID(r)
	if id == "" {
		writeError(w, http.StatusBadRequest, "scan id is required")
		return
	}
	if _, ok := h.store.GetScan(id); !ok {
		writeError(w, http.StatusNotFound, "scan not found")
		return
	}
	ip := strings.TrimSpace(r.URL.Query().Get("ip"))
	if ip == "" {
		writeError(w, http.StatusBadRequest, "query parameter ip is required")
		return
	}
	ifIndex := 0
	if raw := strings.TrimSpace(r.URL.Query().Get("if_index")); raw != "" {
		n, err := strconv.Atoi(raw)
		if err != nil || n < 0 {
			writeError(w, http.StatusBadRequest, "if_index must be >= 0")
			return
		}
		ifIndex = n
	}
	limit := 20000
	if raw := r.URL.Query().Get("limit"); raw != "" {
		n, err := strconv.Atoi(raw)
		if err != nil || n <= 0 || n > 100000 {
			writeError(w, http.StatusBadRequest, "limit must be between 1 and 100000")
			return
		}
		limit = n
	}
	snmpItems := h.store.ListSNMPResults(id, 200000)
	ipToName := make(map[string]string, len(snmpItems))
	for _, s := range snmpItems {
		if !s.Success {
			continue
		}
		name := strings.TrimSpace(s.SysName)
		if name == "" {
			continue
		}
		if _, ok := ipToName[s.IP]; !ok {
			ipToName[s.IP] = name
		}
	}
	items := h.store.ListPortDeviceResults(id, ip, ifIndex, limit)
	for i := range items {
		if lip := strings.TrimSpace(items[i].LearnedIP); lip != "" {
			if nm, ok := ipToName[lip]; ok {
				items[i].Hostname = nm
			}
		}
	}
	writeJSON(w, http.StatusOK, map[string]any{
		"items": items,
	})
}

func (h *Handler) getScanMacLocations(w http.ResponseWriter, r *http.Request) {
	id := scanPathID(r)
	if id == "" {
		writeError(w, http.StatusBadRequest, "scan id is required")
		return
	}
	if _, ok := h.store.GetScan(id); !ok {
		writeError(w, http.StatusNotFound, "scan not found")
		return
	}
	raw := strings.TrimSpace(r.URL.Query().Get("mac"))
	if raw == "" {
		writeError(w, http.StatusBadRequest, "query parameter mac is required")
		return
	}
	norm := scans.NormalizeMAC(raw)
	if norm == "" {
		writeError(w, http.StatusBadRequest, "invalid mac address")
		return
	}
	limit := 2000
	if lim := strings.TrimSpace(r.URL.Query().Get("limit")); lim != "" {
		n, err := strconv.Atoi(lim)
		if err != nil || n <= 0 || n > 10000 {
			writeError(w, http.StatusBadRequest, "limit must be between 1 and 10000")
			return
		}
		limit = n
	}
	accessMax := 8
	trunkMin := 32
	if v := strings.TrimSpace(r.URL.Query().Get("access_max_macs")); v != "" {
		n, err := strconv.Atoi(v)
		if err != nil || n < 1 || n > 4096 {
			writeError(w, http.StatusBadRequest, "access_max_macs must be between 1 and 4096")
			return
		}
		accessMax = n
	}
	if v := strings.TrimSpace(r.URL.Query().Get("trunk_min_macs")); v != "" {
		n, err := strconv.Atoi(v)
		if err != nil || n < 2 || n > 65536 {
			writeError(w, http.StatusBadRequest, "trunk_min_macs must be between 2 and 65536")
			return
		}
		trunkMin = n
	}
	if accessMax >= trunkMin {
		writeError(w, http.StatusBadRequest, "access_max_macs must be less than trunk_min_macs")
		return
	}

	counts, err := h.store.CountDistinctMACsPerSwitchPort(id)
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}

	snmpItems := h.store.ListSNMPResults(id, 200000)
	ipToName := make(map[string]string, len(snmpItems))
	for _, s := range snmpItems {
		if !s.Success {
			continue
		}
		name := strings.TrimSpace(s.SysName)
		if name == "" {
			continue
		}
		if _, ok := ipToName[s.IP]; !ok {
			ipToName[s.IP] = name
		}
	}
	items := h.store.ListPortDevicesByMac(id, norm, limit)
	out := make([]MacLocationRow, 0, len(items))
	for _, r := range items {
		key := scans.PortFDBLocationKey(r.IP, r.IfIndex, r.BridgePort, r.Vlan)
		nOn := counts[key]
		if nOn < 1 {
			nOn = 1
		}
		row := MacLocationRow{
			SwitchIP:   r.IP,
			IfIndex:    r.IfIndex,
			BridgePort: r.BridgePort,
			Vlan:       r.Vlan,
			MAC:        r.MAC,
			ClientIP:   strings.TrimSpace(r.LearnedIP),
			MacsOnPort: nOn,
			PortKind:   scans.ClassifyPortKind(nOn, accessMax, trunkMin),
			CheckedAt:  r.CheckedAt,
		}
		if nm, ok := ipToName[r.IP]; ok {
			row.SwitchSysName = nm
		}
		if row.ClientIP != "" {
			if nm, ok := ipToName[row.ClientIP]; ok {
				row.ClientName = nm
			}
		}
		out = append(out, row)
	}
	sort.Slice(out, func(i, j int) bool {
		ri, rj := scans.PortKindRank(out[i].PortKind), scans.PortKindRank(out[j].PortKind)
		if ri != rj {
			return ri < rj
		}
		if out[i].MacsOnPort != out[j].MacsOnPort {
			return out[i].MacsOnPort < out[j].MacsOnPort
		}
		if out[i].SwitchIP != out[j].SwitchIP {
			return out[i].SwitchIP < out[j].SwitchIP
		}
		if out[i].IfIndex != out[j].IfIndex {
			return out[i].IfIndex < out[j].IfIndex
		}
		if out[i].Vlan != out[j].Vlan {
			return out[i].Vlan < out[j].Vlan
		}
		return out[i].ClientIP < out[j].ClientIP
	})

	likely := make([]MacLocationRow, 0)
	for _, row := range out {
		if row.PortKind == "access" {
			likely = append(likely, row)
		}
	}
	sort.Slice(likely, func(i, j int) bool {
		if likely[i].MacsOnPort != likely[j].MacsOnPort {
			return likely[i].MacsOnPort < likely[j].MacsOnPort
		}
		if likely[i].SwitchIP != likely[j].SwitchIP {
			return likely[i].SwitchIP < likely[j].SwitchIP
		}
		if likely[i].IfIndex != likely[j].IfIndex {
			return likely[i].IfIndex < likely[j].IfIndex
		}
		return likely[i].Vlan < likely[j].Vlan
	})

	writeJSON(w, http.StatusOK, map[string]any{
		"mac":                 norm,
		"access_max_macs":     accessMax,
		"trunk_min_macs":      trunkMin,
		"likely_attachment":   likely,
		"items":               out,
	})
}

func (h *Handler) getScanLinks(w http.ResponseWriter, r *http.Request) {
	id := scanPathID(r)
	if id == "" {
		writeError(w, http.StatusBadRequest, "scan id is required")
		return
	}
	if _, ok := h.store.GetScan(id); !ok {
		writeError(w, http.StatusNotFound, "scan not found")
		return
	}

	limit := 2000
	if raw := r.URL.Query().Get("limit"); raw != "" {
		n, err := strconv.Atoi(raw)
		if err != nil || n <= 0 || n > 20000 {
			writeError(w, http.StatusBadRequest, "limit must be between 1 and 20000")
			return
		}
		limit = n
	}

	snmpItems := h.store.ListSNMPResults(id, 200000)
	lldpItems := h.store.ListLLDPResults(id, limit)

	sysNameToIP := make(map[string]string, len(snmpItems))
	for _, s := range snmpItems {
		name := strings.TrimSpace(strings.ToLower(s.SysName))
		if name == "" {
			continue
		}
		if _, exists := sysNameToIP[name]; !exists {
			sysNameToIP[name] = s.IP
		}
	}

	links := make([]LinkView, 0, len(lldpItems))
	for _, l := range lldpItems {
		targetNameNorm := strings.TrimSpace(strings.ToLower(l.RemoteSysName))
		targetIP := ""
		resolvedBy := "unresolved"
		if targetNameNorm != "" {
			if ip, ok := sysNameToIP[targetNameNorm]; ok {
				targetIP = ip
				resolvedBy = "remote_sys_name"
			}
		}

		links = append(links, LinkView{
			SourceIP:      l.IP,
			SourcePort:    l.LocalPortNum,
			TargetIP:      targetIP,
			TargetSysName: l.RemoteSysName,
			TargetPort:    l.RemotePortID,
			RemoteChassis: l.RemoteChassisID,
			ResolvedBy:    resolvedBy,
		})
	}

	writeJSON(w, http.StatusOK, map[string]any{
		"items": links,
	})
}

func (h *Handler) getScanTopology(w http.ResponseWriter, r *http.Request) {
	id := scanPathID(r)
	if id == "" {
		writeError(w, http.StatusBadRequest, "scan id is required")
		return
	}
	if _, ok := h.store.GetScan(id); !ok {
		writeError(w, http.StatusNotFound, "scan not found")
		return
	}

	limit := 5000
	if raw := r.URL.Query().Get("limit"); raw != "" {
		n, err := strconv.Atoi(raw)
		if err != nil || n <= 0 || n > 50000 {
			writeError(w, http.StatusBadRequest, "limit must be between 1 and 50000")
			return
		}
		limit = n
	}

	snmpItems := h.store.ListSNMPResults(id, 200000)
	lldpItems := h.store.ListLLDPResults(id, limit)

	sysNameToIP := make(map[string]string, len(snmpItems))
	nodesByIP := make(map[string]TopologyNode, len(snmpItems))
	for _, s := range snmpItems {
		nameNorm := strings.TrimSpace(strings.ToLower(s.SysName))
		if nameNorm != "" {
			if _, exists := sysNameToIP[nameNorm]; !exists {
				sysNameToIP[nameNorm] = s.IP
			}
		}
		nodesByIP[s.IP] = TopologyNode{
			ID:   s.IP,
			IP:   s.IP,
			Name: s.SysName,
		}
	}

	edges := make([]TopologyEdge, 0, len(lldpItems))
	for _, l := range lldpItems {
		targetIP := ""
		targetNameNorm := strings.TrimSpace(strings.ToLower(l.RemoteSysName))
		if targetNameNorm != "" {
			targetIP = sysNameToIP[targetNameNorm]
		}
		if _, exists := nodesByIP[l.IP]; !exists {
			nodesByIP[l.IP] = TopologyNode{ID: l.IP, IP: l.IP}
		}
		if targetIP != "" {
			if _, exists := nodesByIP[targetIP]; !exists {
				nodesByIP[targetIP] = TopologyNode{ID: targetIP, IP: targetIP, Name: l.RemoteSysName}
			}
		}

		edges = append(edges, TopologyEdge{
			SourceIP:   l.IP,
			SourcePort: l.LocalPortNum,
			TargetIP:   targetIP,
			TargetName: l.RemoteSysName,
			TargetPort: l.RemotePortID,
		})
	}

	nodes := make([]TopologyNode, 0, len(nodesByIP))
	for _, n := range nodesByIP {
		nodes = append(nodes, n)
	}

	writeJSON(w, http.StatusOK, map[string]any{
		"nodes": nodes,
		"edges": edges,
	})
}

func withJSON(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if strings.HasPrefix(r.URL.Path, "/api/") || r.URL.Path == "/health" {
			w.Header().Set("Content-Type", "application/json; charset=utf-8")
		}
		next.ServeHTTP(w, r)
	})
}

func hostUpSet(items []scans.HostResult) map[string]struct{} {
	out := make(map[string]struct{}, len(items))
	for _, h := range items {
		if h.IsUp {
			out[h.IP] = struct{}{}
		}
	}
	return out
}

func linkSet(items []scans.LLDPResult) map[string]struct{} {
	out := make(map[string]struct{}, len(items))
	for _, l := range items {
		key := l.IP + "|" + l.LocalPortNum + "|" + l.RemoteSysName + "|" + l.RemotePortID + "|" + l.RemoteChassisID
		out[key] = struct{}{}
	}
	return out
}

func setDiff(a, b map[string]struct{}) []string {
	out := make([]string, 0)
	for k := range a {
		if _, ok := b[k]; !ok {
			out = append(out, k)
		}
	}
	return out
}

func writeJSON(w http.ResponseWriter, status int, payload any) {
	w.WriteHeader(status)
	_ = json.NewEncoder(w).Encode(payload)
}

func writeError(w http.ResponseWriter, status int, message string) {
	writeJSON(w, status, map[string]string{"error": message})
}