package atlas

import (
	"strings"

	"crypto-miner-server/internal/strategy"
)

// GossipHint is one negative-knowledge skip shared between LAN siblings.
type GossipHint struct {
	Tier      string `json:"tier"`
	Condition string `json:"condition"`
	Reason    string `json:"reason,omitempty"`
}

// SubnetPrefix returns the /24 (IPv4) or /48-ish (IPv6) prefix used for LAN sibling matching.
func SubnetPrefix(ip string) string {
	return strategy.FingerprintFromAuth("", ip, false).Subnet
}

// NormalizeGossipHint trims and validates one gossip hint.
func NormalizeGossipHint(h GossipHint) (GossipHint, bool) {
	h.Tier = strings.TrimSpace(h.Tier)
	h.Condition = strings.TrimSpace(h.Condition)
	h.Reason = strings.TrimSpace(h.Reason)
	if h.Tier == "" || h.Condition == "" {
		return GossipHint{}, false
	}
	if h.Reason == "" {
		h.Reason = "lan gossip"
	}
	return h, true
}

// NormalizeGossipHints drops invalid hints while preserving order.
func NormalizeGossipHints(in []GossipHint) []GossipHint {
	if len(in) == 0 {
		return nil
	}
	out := make([]GossipHint, 0, len(in))
	for _, h := range in {
		if norm, ok := NormalizeGossipHint(h); ok {
			out = append(out, norm)
		}
	}
	return out
}

// SkipsFromHints converts gossip hints to atlas skips for agent merge.
func SkipsFromHints(hints []GossipHint) []AtlasSkip {
	out := make([]AtlasSkip, 0, len(hints))
	for _, h := range hints {
		if norm, ok := NormalizeGossipHint(h); ok {
			out = append(out, AtlasSkip{
				Tier:      norm.Tier,
				Condition: norm.Condition,
				Reason:    norm.Reason,
			})
		}
	}
	return out
}

// MergeGossipSkips merges incoming LAN hints into existing skips without duplicates.
func MergeGossipSkips(existing []AtlasSkip, incoming []GossipHint) []AtlasSkip {
	hints := NormalizeGossipHints(incoming)
	if len(hints) == 0 {
		return existing
	}
	have := make(map[string]bool, len(existing)+len(hints))
	out := append([]AtlasSkip(nil), existing...)
	for _, s := range existing {
		have[s.Tier+"|"+s.Condition] = true
	}
	for _, h := range hints {
		key := h.Tier + "|" + h.Condition
		if have[key] {
			continue
		}
		have[key] = true
		out = append(out, AtlasSkip{
			Tier:      h.Tier,
			Condition: h.Condition,
			Reason:    h.Reason,
		})
	}
	return out
}