ping_service/input_service/http_input_service.go

package main

import (
	"bufio"
	"context"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"io"
	"log"
	"math/rand"
	"net"
	"net/http"
	"net/netip"
	"os"
	"os/signal"
	"path/filepath"
	"strings"
	"sync"
	"sync/atomic"
	"syscall"
	"time"
)

const (
	repoDir       = "cloud-provider-ip-addresses"
	port          = 8080
	stateDir      = "progress_state"
	saveInterval  = 30 * time.Second
	cleanupInterval = 5 * time.Minute
	generatorTTL  = 24 * time.Hour
	maxImportSize = 10 * 1024 * 1024 // 10MB
	interleavedGens = 10 // Number of concurrent CIDR generators to interleave
)

// GeneratorState represents the serializable state of a generator
type GeneratorState struct {
	RemainingCIDRs []string       `json:"remaining_cidrs"`
	CurrentGen     *HostGenState  `json:"current_gen,omitempty"`
	TotalCIDRs     int            `json:"total_cidrs"`
}

type HostGenState struct {
	CIDR    string `json:"cidr"`
	Current string `json:"current"`
	Done    bool   `json:"done"`
}

// IPGenerator generates IPs from CIDR ranges lazily
type IPGenerator struct {
	mu               sync.Mutex
	rng              *rand.Rand
	totalCIDRsCount  int
	remainingCIDRs   []string
	currentGen       *hostGenerator
	activeGens       []*hostGenerator // Multiple active generators for interleaving
	genRotationIdx   int              // Current rotation index
	consumer         string
	dirty            atomic.Bool
	seenIPs          map[string]bool  // Deduplication map
}

type hostGenerator struct {
	prefix  netip.Prefix
	current netip.Addr
	last    netip.Addr
	done    bool
}

func addrToUint32(a netip.Addr) uint32 {
	b := a.As4()
	return uint32(b[0])<<24 | uint32(b[1])<<16 | uint32(b[2])<<8 | uint32(b[3])
}

func uint32ToAddr(u uint32) netip.Addr {
	return netip.AddrFrom4([4]byte{byte(u >> 24), byte(u >> 16), byte(u >> 8), byte(u)})
}

func newHostGenerator(cidr string) (*hostGenerator, error) {
	prefix, err := netip.ParsePrefix(cidr)
	if err != nil {
		return nil, err
	}
	prefix = prefix.Masked()
	if !prefix.IsValid() || !prefix.Addr().Is4() {
		return nil, fmt.Errorf("invalid IPv4 prefix")
	}
	if prefix.Addr().IsMulticast() {
		return nil, fmt.Errorf("multicast network")
	}

	ip := prefix.Addr()
	maskLen := prefix.Bits()

	var first, last netip.Addr
	lastUint := addrToUint32(ip) | ((1 << (32 - uint(maskLen))) - 1)
	last = uint32ToAddr(lastUint)

	if maskLen == 32 {
		first = ip
		last = ip
	} else if maskLen == 31 {
		first = ip
		// last already ip + 1
	} else {
		first = ip.Next()
		last = last.Prev()
	}

	if !prefix.Contains(first) || !prefix.Contains(last) {
		return nil, fmt.Errorf("invalid range")
	}

	return &hostGenerator{
		prefix:  prefix,
		current: first,
		last:    last,
		done:    false,
	}, nil
}

func (hg *hostGenerator) next() (string, bool) {
	if hg.done {
		return "", false
	}

	if !hg.prefix.Contains(hg.current) || addrToUint32(hg.current) > addrToUint32(hg.last) {
		hg.done = true
		return "", false
	}

	if hg.current.IsMulticast() {
		hg.current = hg.current.Next()
		return hg.next()
	}

	ip := hg.current.String()
	hg.current = hg.current.Next()

	return ip, true
}

func (hg *hostGenerator) getState() HostGenState {
	return HostGenState{
		CIDR:    hg.prefix.String(),
		Current: hg.current.String(),
		Done:    hg.done,
	}
}

func newIPGenerator(s *Server, consumer string) (*IPGenerator, error) {
	gen := &IPGenerator{
		rng:        rand.New(rand.NewSource(time.Now().UnixNano())),
		consumer:   consumer,
		seenIPs:    make(map[string]bool),
		activeGens: make([]*hostGenerator, 0, interleavedGens),
	}

	// Try to load existing state
	if err := gen.loadState(); err == nil {
		log.Printf("📂 Loaded saved state for consumer: %s", consumer)
		return gen, nil
	}

	// No saved state, initialize fresh
	gen.remainingCIDRs = append([]string{}, s.allCIDRs...)
	gen.rng.Shuffle(len(gen.remainingCIDRs), func(i, j int) {
		gen.remainingCIDRs[i], gen.remainingCIDRs[j] = gen.remainingCIDRs[j], gen.remainingCIDRs[i]
	})
	gen.totalCIDRsCount = len(gen.remainingCIDRs)
	gen.dirty.Store(true)

	log.Printf("🆕 New generator for %s: %d total CIDRs", consumer, gen.totalCIDRsCount)

	return gen, nil
}

func (g *IPGenerator) Next() (string, error) {
	g.mu.Lock()
	defer g.mu.Unlock()

	// Ensure we have enough active generators for interleaving
	for len(g.activeGens) < interleavedGens && len(g.remainingCIDRs) > 0 {
		cidr := g.remainingCIDRs[0]
		g.remainingCIDRs = g.remainingCIDRs[1:]

		if !strings.Contains(cidr, "/") {
			cidr += "/32"
		}

		newGen, err := newHostGenerator(cidr)
		if err != nil {
			g.dirty.Store(true)
			continue
		}

		g.activeGens = append(g.activeGens, newGen)
		g.dirty.Store(true)
	}

	// Try to get IP from rotating generators
	maxAttempts := len(g.activeGens) * 100 // Avoid infinite loop
	for attempt := 0; attempt < maxAttempts || len(g.activeGens) > 0; attempt++ {
		if len(g.activeGens) == 0 {
			if len(g.remainingCIDRs) == 0 {
				return "", fmt.Errorf("no more IPs available")
			}
			// Refill active generators
			for len(g.activeGens) < interleavedGens && len(g.remainingCIDRs) > 0 {
				cidr := g.remainingCIDRs[0]
				g.remainingCIDRs = g.remainingCIDRs[1:]

				if !strings.Contains(cidr, "/") {
					cidr += "/32"
				}

				newGen, err := newHostGenerator(cidr)
				if err != nil {
					g.dirty.Store(true)
					continue
				}

				g.activeGens = append(g.activeGens, newGen)
				g.dirty.Store(true)
			}
			if len(g.activeGens) == 0 {
				return "", fmt.Errorf("no more IPs available")
			}
		}

		// Round-robin through active generators
		g.genRotationIdx = g.genRotationIdx % len(g.activeGens)
		gen := g.activeGens[g.genRotationIdx]

		ip, ok := gen.next()
		if !ok {
			// Remove exhausted generator
			g.activeGens = append(g.activeGens[:g.genRotationIdx], g.activeGens[g.genRotationIdx+1:]...)
			g.dirty.Store(true)
			if g.genRotationIdx >= len(g.activeGens) && len(g.activeGens) > 0 {
				g.genRotationIdx = 0
			}
			continue
		}

		// Check deduplication
		if g.seenIPs[ip] {
			g.genRotationIdx = (g.genRotationIdx + 1) % max(len(g.activeGens), 1)
			continue
		}

		g.seenIPs[ip] = true
		g.genRotationIdx = (g.genRotationIdx + 1) % max(len(g.activeGens), 1)
		g.dirty.Store(true)
		return ip, nil
	}

	return "", fmt.Errorf("no more unique IPs available")
}

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

func (g *IPGenerator) buildState() GeneratorState {
	// Assumes mu is held
	state := GeneratorState{
		RemainingCIDRs: append([]string{}, g.remainingCIDRs...),
		TotalCIDRs:     g.totalCIDRsCount,
	}
	if g.currentGen != nil && !g.currentGen.done {
		state.CurrentGen = &HostGenState{
			CIDR:    g.currentGen.prefix.String(),
			Current: g.currentGen.current.String(),
			Done:    false,
		}
	}
	return state
}

func (g *IPGenerator) getState() GeneratorState {
	g.mu.Lock()
	defer g.mu.Unlock()
	return g.buildState()
}

func (g *IPGenerator) saveState() error {
	g.mu.Lock()
	if !g.dirty.Load() {
		g.mu.Unlock()
		return nil
	}
	state := g.buildState()
	g.dirty.Store(false)
	g.mu.Unlock()

	// Ensure state directory exists
	if err := os.MkdirAll(stateDir, 0755); err != nil {
		return fmt.Errorf("failed to create state directory: %w", err)
	}

	// Use hash of consumer as filename
	hash := sha256.Sum256([]byte(g.consumer))
	filename := hex.EncodeToString(hash[:])
	filePath := filepath.Join(stateDir, filename+".json")

	// Write to temp file first, then rename
	tempPath := filePath + ".tmp"
	file, err := os.Create(tempPath)
	if err != nil {
		return fmt.Errorf("failed to create temp state file: %w", err)
	}
	defer file.Close()

	encoder := json.NewEncoder(file)
	encoder.SetIndent("", "  ")
	if err := encoder.Encode(state); err != nil {
		os.Remove(tempPath)
		return fmt.Errorf("failed to encode state: %w", err)
	}

	if err := os.Rename(tempPath, filePath); err != nil {
		os.Remove(tempPath)
		return fmt.Errorf("failed to rename state file: %w", err)
	}

	return nil
}

func (g *IPGenerator) loadState() error {
	// Use hash of consumer as filename
	hash := sha256.Sum256([]byte(g.consumer))
	filename := hex.EncodeToString(hash[:])
	filePath := filepath.Join(stateDir, filename+".json")

	file, err := os.Open(filePath)
	if err != nil {
		return err
	}
	defer file.Close()

	var state GeneratorState
	if err := json.NewDecoder(file).Decode(&state); err != nil {
		return fmt.Errorf("failed to decode state: %w", err)
	}

	// Restore state
	g.remainingCIDRs = state.RemainingCIDRs
	g.totalCIDRsCount = state.TotalCIDRs

	if state.CurrentGen != nil {
		gen, err := newHostGenerator(state.CurrentGen.CIDR)
		if err != nil {
			return err
		}
		gen.current, err = netip.ParseAddr(state.CurrentGen.Current)
		if err != nil {
			return err
		}
		gen.done = state.CurrentGen.Done
		g.currentGen = gen
	}

	return nil
}

// Server holds per-consumer generators
type Server struct {
	generators map[string]*IPGenerator
	lastAccess map[string]time.Time
	allCIDRs   []string
	globalSeen map[string]bool // Global deduplication across all sources
	mu         sync.RWMutex
	stopSaver  chan struct{}
	stopCleanup chan struct{}
	wg         sync.WaitGroup
}

func newServer() *Server {
	s := &Server{
		generators:  make(map[string]*IPGenerator),
		lastAccess:  make(map[string]time.Time),
		globalSeen:  make(map[string]bool),
		stopSaver:   make(chan struct{}),
		stopCleanup: make(chan struct{}),
	}

	if err := s.loadAllCIDRs(); err != nil {
		log.Fatalf("❌ Failed to load CIDRs: %v", err)
	}

	s.startPeriodicSaver()
	s.startCleanup()

	return s
}

func (s *Server) loadAllCIDRs() error {
	// Find all IP files
	var fileList []string
	err := filepath.Walk(repoDir, func(path string, info os.FileInfo, err error) error {
		if err != nil {
			return err
		}
		if !info.IsDir() && strings.HasSuffix(path, ".txt") && strings.Contains(strings.ToLower(path), "ips") {
			fileList = append(fileList, path)
		}
		return nil
	})
	if err != nil {
		return fmt.Errorf("failed to scan repo directory: %w", err)
	}

	if len(fileList) == 0 {
		return fmt.Errorf("no IP files found in %s", repoDir)
	}

	// Load all CIDRs
	for _, path := range fileList {
		file, err := os.Open(path)
		if err != nil {
			log.Printf("⚠️ Failed to open %s: %v", path, err)
			continue
		}
		scanner := bufio.NewScanner(file)
		for scanner.Scan() {
			line := strings.TrimSpace(scanner.Text())
			if line == "" || strings.HasPrefix(line, "#") {
				continue
			}
			fields := strings.Fields(line)
			for _, field := range fields {
				if field != "" {
					if strings.Contains(field, "/") || netip.MustParseAddr(field).IsValid() {
						s.allCIDRs = append(s.allCIDRs, field)
					}
				}
			}
		}
		file.Close()
		if err := scanner.Err(); err != nil {
			log.Printf("⚠️ Error reading %s: %v", path, err)
		}
	}

	log.Printf("📁 Found %d IP files", len(fileList))
	log.Printf("📊 Total CIDRs discovered: %d", len(s.allCIDRs))

	return nil
}

func (s *Server) startPeriodicSaver() {
	s.wg.Add(1)
	go func() {
		defer s.wg.Done()
		ticker := time.NewTicker(saveInterval)
		defer ticker.Stop()

		for {
			select {
			case <-ticker.C:
				s.saveAllStates()
			case <-s.stopSaver:
				s.saveAllStates()
				return
			}
		}
	}()
}

func (s *Server) startCleanup() {
	s.wg.Add(1)
	go func() {
		defer s.wg.Done()
		ticker := time.NewTicker(cleanupInterval)
		defer ticker.Stop()

		for {
			select {
			case <-ticker.C:
				s.cleanupOldGenerators()
			case <-s.stopCleanup:
				return
			}
		}
	}()
}

func (s *Server) cleanupOldGenerators() {
	s.mu.Lock()
	defer s.mu.Unlock()

	now := time.Now()
	for consumer, t := range s.lastAccess {
		if now.Sub(t) > generatorTTL {
			delete(s.generators, consumer)
			delete(s.lastAccess, consumer)

			// Remove state file
			hash := sha256.Sum256([]byte(consumer))
			fn := hex.EncodeToString(hash[:]) + ".json"
			p := filepath.Join(stateDir, fn)
			if err := os.Remove(p); err != nil && !os.IsNotExist(err) {
				log.Printf("⚠️ Failed to remove state file %s: %v", p, err)
			}
		}
	}
}

func (s *Server) saveAllStates() {
	s.mu.RLock()
	gens := make([]*IPGenerator, 0, len(s.generators))
	for _, gen := range s.generators {
		gens = append(gens, gen)
	}
	s.mu.RUnlock()

	for _, gen := range gens {
		if err := gen.saveState(); err != nil {
			log.Printf("⚠️ Failed to save state for %s: %v", gen.consumer, err)
		}
	}
}

func (s *Server) shutdown() {
	close(s.stopSaver)
	close(s.stopCleanup)
	s.wg.Wait()
	log.Println("💾 All states saved")
}

func (s *Server) getGenerator(consumer string) (*IPGenerator, error) {
	s.mu.RLock()
	gen, exists := s.generators[consumer]
	s.mu.RUnlock()

	if exists {
		s.mu.Lock()
		s.lastAccess[consumer] = time.Now()
		s.mu.Unlock()
		return gen, nil
	}

	s.mu.Lock()
	defer s.mu.Unlock()

	// Double-check
	if gen, exists := s.generators[consumer]; exists {
		s.lastAccess[consumer] = time.Now()
		return gen, nil
	}

	newGen, err := newIPGenerator(s, consumer)
	if err != nil {
		return nil, err
	}

	s.generators[consumer] = newGen
	s.lastAccess[consumer] = time.Now()
	log.Printf("🆕 New consumer: %s", consumer)

	return newGen, nil
}

func (s *Server) handleRequest(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
		return
	}

	addrPort, err := netip.ParseAddrPort(r.RemoteAddr)
	consumerStr := r.RemoteAddr
	if err == nil {
		consumerStr = addrPort.Addr().String()
	} else {
		host, _, err := net.SplitHostPort(r.RemoteAddr)
		if err == nil {
			consumerStr = host
		}
	}

	gen, err := s.getGenerator(consumerStr)
	if err != nil {
		log.Printf("❌ Failed to get generator for %s: %v", consumerStr, err)
		http.Error(w, "Internal server error", http.StatusInternalServerError)
		return
	}

	ip, err := gen.Next()
	if err != nil {
		log.Printf("❌ Failed to get IP for %s: %v", consumerStr, err)
		http.Error(w, "No more IPs available", http.StatusServiceUnavailable)
		return
	}

	log.Printf("📤 Serving IP to %s: %s", consumerStr, ip)

	w.Header().Set("Content-Type", "text/plain")
	fmt.Fprintf(w, "%s\n", ip)
}

type ConsumerStatus struct {
	Consumer       string `json:"consumer"`
	RemainingCIDRs int    `json:"remaining_cidrs"`
	HasActiveGen   bool   `json:"has_active_gen"`
	TotalCIDRs     int    `json:"total_cidrs"`
}

type StatusResponse struct {
	TotalConsumers int              `json:"total_consumers"`
	Consumers      []ConsumerStatus `json:"consumers"`
	StateDirectory string           `json:"state_directory"`
	SaveInterval   string           `json:"save_interval"`
}

func (s *Server) handleStatus(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
		return
	}

	s.mu.RLock()
	defer s.mu.RUnlock()

	response := StatusResponse{
		TotalConsumers: len(s.generators),
		Consumers:      make([]ConsumerStatus, 0, len(s.generators)),
		StateDirectory: stateDir,
		SaveInterval:   saveInterval.String(),
	}

	for consumer, gen := range s.generators {
		gen.mu.Lock()
		status := ConsumerStatus{
			Consumer:       consumer,
			RemainingCIDRs: len(gen.remainingCIDRs),
			HasActiveGen:   gen.currentGen != nil,
			TotalCIDRs:     gen.totalCIDRsCount,
		}
		gen.mu.Unlock()

		response.Consumers = append(response.Consumers, status)
	}

	w.Header().Set("Content-Type", "application/json")
	encoder := json.NewEncoder(w)
	encoder.SetIndent("", "  ")
	if err := encoder.Encode(response); err != nil {
		log.Printf("❌ Failed to encode status response: %v", err)
	}
}

type ExportResponse struct {
	ExportedAt time.Time                 `json:"exported_at"`
	States     map[string]GeneratorState `json:"states"`
}

func (s *Server) handleExport(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
		return
	}

	// Force save all current states first
	s.saveAllStates()

	s.mu.RLock()
	defer s.mu.RUnlock()

	response := ExportResponse{
		ExportedAt: time.Now(),
		States:     make(map[string]GeneratorState, len(s.generators)),
	}

	for consumer, gen := range s.generators {
		response.States[consumer] = gen.getState()
	}

	w.Header().Set("Content-Type", "application/json")
	w.Header().Set("Content-Disposition", fmt.Sprintf("attachment; filename=state-export-%s.json",
		time.Now().Format("2006-01-02-150405")))

	encoder := json.NewEncoder(w)
	encoder.SetIndent("", "  ")
	if err := encoder.Encode(response); err != nil {
		log.Printf("❌ Failed to encode export response: %v", err)
	}
}

func (s *Server) handleImport(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
		return
	}

	reader := http.MaxBytesReader(w, r.Body, maxImportSize)
	defer r.Body.Close()

	var exportData ExportResponse
	if err := json.NewDecoder(reader).Decode(&exportData); err != nil {
		if err == io.EOF || strings.Contains(err.Error(), "EOF") {
			http.Error(w, "Invalid or empty request body", http.StatusBadRequest)
		} else {
			http.Error(w, fmt.Sprintf("Failed to decode import data: %v", err), http.StatusBadRequest)
		}
		return
	}

	// Ensure state directory exists
	if err := os.MkdirAll(stateDir, 0755); err != nil {
		http.Error(w, fmt.Sprintf("Failed to create state directory: %v", err), http.StatusInternalServerError)
		return
	}

	imported := 0
	failed := 0

	for consumer, state := range exportData.States {
		// Use hash for filename
		hash := sha256.Sum256([]byte(consumer))
		filename := hex.EncodeToString(hash[:])
		filePath := filepath.Join(stateDir, filename+".json")

		file, err := os.Create(filePath)
		if err != nil {
			log.Printf("⚠️ Failed to create state file for %s: %v", consumer, err)
			failed++
			continue
		}

		encoder := json.NewEncoder(file)
		encoder.SetIndent("", "  ")
		if err := encoder.Encode(state); err != nil {
			file.Close()
			log.Printf("⚠️ Failed to encode state for %s: %v", consumer, err)
			failed++
			os.Remove(filePath)
			continue
		}

		file.Close()
		imported++
	}

	response := map[string]interface{}{
		"imported": imported,
		"failed":   failed,
		"total":    len(exportData.States),
		"message":  fmt.Sprintf("Successfully imported %d consumer states", imported),
	}

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(response)

	log.Printf("📥 Imported %d consumer states (%d failed)", imported, failed)
}

// HopsRequest is the payload from output_service
type HopsRequest struct {
	Hops []string `json:"hops"`
}

func (s *Server) handleHops(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
		return
	}

	defer r.Body.Close()

	var req HopsRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		http.Error(w, "Invalid JSON", http.StatusBadRequest)
		return
	}

	s.mu.Lock()
	defer s.mu.Unlock()

	added := 0
	duplicates := 0

	for _, hop := range req.Hops {
		// Validate IP
		addr, err := netip.ParseAddr(hop)
		if err != nil {
			log.Printf("⚠️ Invalid hop IP: %s", hop)
			continue
		}

		// Skip if not IPv4
		if !addr.Is4() {
			continue
		}

		// Skip multicast, private, loopback
		if addr.IsMulticast() || addr.IsLoopback() || addr.IsPrivate() {
			continue
		}

		// Check global deduplication
		if s.globalSeen[hop] {
			duplicates++
			continue
		}

		// Add to global pool
		s.globalSeen[hop] = true
		s.allCIDRs = append(s.allCIDRs, hop)
		added++
	}

	log.Printf("🔍 Received %d hops: %d new, %d duplicates", len(req.Hops), added, duplicates)

	response := map[string]interface{}{
		"status":     "ok",
		"received":   len(req.Hops),
		"added":      added,
		"duplicates": duplicates,
	}

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(response)
}

// ServiceInfo represents service metadata for discovery
type ServiceInfo struct {
	ServiceType  string   `json:"service_type"`
	Version      string   `json:"version"`
	Name         string   `json:"name"`
	InstanceID   string   `json:"instance_id"`
	Capabilities []string `json:"capabilities"`
}

func (s *Server) handleServiceInfo(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
		return
	}

	hostname, _ := os.Hostname()
	if hostname == "" {
		hostname = "unknown"
	}

	info := ServiceInfo{
		ServiceType:  "input",
		Version:      "1.0.0",
		Name:         "http_input_service",
		InstanceID:   hostname,
		Capabilities: []string{"target_generation", "cidr_import", "hop_discovery"},
	}

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(info)
}

func main() {
	// Check if repo directory exists
	if _, err := os.Stat(repoDir); os.IsNotExist(err) {
		log.Fatalf("❌ Error: Directory '%s' not found", repoDir)
	}

	server := newServer()

	mux := http.NewServeMux()
	mux.HandleFunc("/", server.handleRequest)
	mux.HandleFunc("/status", server.handleStatus)
	mux.HandleFunc("/service-info", server.handleServiceInfo)
	mux.HandleFunc("/export", server.handleExport)
	mux.HandleFunc("/import", server.handleImport)
	mux.HandleFunc("/hops", server.handleHops)

	httpServer := &http.Server{
		Addr:         fmt.Sprintf(":%d", port),
		Handler:      mux,
		ReadTimeout:  10 * time.Second,
		WriteTimeout: 10 * time.Second,
		IdleTimeout:  60 * time.Second,
	}

	// Graceful shutdown handling
	go func() {
		sigChan := make(chan os.Signal, 1)
		signal.Notify(sigChan, os.Interrupt, syscall.SIGTERM)
		<-sigChan

		log.Println("\n🛑 Shutting down gracefully...")

		ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
		defer cancel()

		// Stop savers and save final state
		server.shutdown()

		if err := httpServer.Shutdown(ctx); err != nil {
			log.Printf("❌ Error during shutdown: %v", err)
		}
	}()

	log.Printf("🌐 HTTP Input Server running on http://localhost:%d", port)
	log.Printf("   Serving individual IPv4 host addresses lazily")
	log.Printf("   In highly mixed random order per consumer")
	log.Printf("   🔄 Interleaving %d CIDRs to avoid same-subnet consecutive IPs", interleavedGens)
	log.Printf("   💾 Progress saved every %v to '%s' directory", saveInterval, stateDir)
	log.Printf("   📊 Status endpoint: http://localhost:%d/status", port)
	log.Printf("   📤 Export endpoint: http://localhost:%d/export", port)
	log.Printf("   📥 Import endpoint: http://localhost:%d/import (POST)", port)
	log.Printf("   🔍 Hops endpoint: http://localhost:%d/hops (POST)", port)
	log.Printf("   Press Ctrl+C to stop")

	if err := httpServer.ListenAndServe(); err != nil && err != http.ErrServerClosed {
		log.Fatalf("❌ Server error: %v", err)
	}

	log.Println("✅ Server stopped cleanly")
}