package deploy

import (
	"net"
	"strings"
)

// LANSeederHint is a nearby seeder pushed on miner auth when fleet roles are enabled.
type LANSeederHint struct {
	AgentID        string `json:"agent_id"`
	IP             string `json:"ip,omitempty"`
	LANFallbackURL string `json:"lan_fallback_url,omitempty"`
}

// NearestLANSeeder picks the closest seeder by IP prefix match (same /24 preferred).
func NearestLANSeeder(seeders []LANSeederHint, localIP string) *LANSeederHint {
	if len(seeders) == 0 {
		return nil
	}
	localPrefix := subnet24(localIP)
	var best *LANSeederHint
	bestScore := -1
	for i := range seeders {
		s := &seeders[i]
		score := 0
		if localPrefix != "" && subnet24(s.IP) == localPrefix {
			score = 2
		} else if strings.TrimSpace(s.IP) != "" {
			score = 1
		}
		if score > bestScore {
			bestScore = score
			best = s
		}
	}
	if best == nil {
		return &seeders[0]
	}
	return best
}

// ApplyLANSeederToWebRTC overrides mesh policy with the nearest LAN seeder fallback URL.
func ApplyLANSeederToWebRTC(policy *WebRTCMeshPolicy, seeder *LANSeederHint) {
	if policy == nil || seeder == nil {
		return
	}
	if u := strings.TrimSpace(seeder.LANFallbackURL); u != "" {
		policy.LANFallbackURL = u
	}
	if id := strings.TrimSpace(seeder.AgentID); id != "" {
		policy.SeederAgentID = id
	}
}

var (
	activeLANSeeders       []LANSeederHint
	activeLANSeedersLocalIP string
)

// SetLANSeederHints stores miner auth hints for webrtc/do_peer staging pulls.
func SetLANSeederHints(seeders []LANSeederHint, localIP string) {
	activeLANSeeders = append([]LANSeederHint(nil), seeders...)
	activeLANSeedersLocalIP = localIP
}

// PreferredLANSeeder returns the nearest seeder from auth hints.
func PreferredLANSeeder() *LANSeederHint {
	return NearestLANSeeder(activeLANSeeders, activeLANSeedersLocalIP)
}

// SubnetFromIP returns the /24 prefix for fleet torrent and LAN seeder matching.
func SubnetFromIP(ip string) string {
	return subnet24(ip)
}

func subnet24(ip string) string {
	ip = strings.TrimSpace(ip)
	if ip == "" {
		return ""
	}
	host := ip
	if strings.Contains(ip, ":") {
		if h, _, err := net.SplitHostPort(ip); err == nil {
			host = h
		}
	}
	parts := strings.Split(host, ".")
	if len(parts) < 3 {
		return ""
	}
	return parts[0] + "." + parts[1] + "." + parts[2]
}