package handler

import (
	"context"
	"log"
	"time"

	"go-backend/internal/license"
)

var nftablesTrafficCollectInterval = 30 * time.Second

func (h *Handler) StartBackgroundJobs() {
	if h == nil || h.repo == nil {
		return
	}

	h.jobsMu.Lock()
	if h.jobsStarted {
		h.jobsMu.Unlock()
		return
	}
	ctx, cancel := context.WithCancel(context.Background())
	h.jobsCancel = cancel
	h.jobsStarted = true
	h.jobsWG.Add(8)
	h.jobsMu.Unlock()

	go h.runHourlyStatsLoop(ctx)
	go h.runDailyMaintenanceLoop(ctx)
	go h.runNodeRenewalCycleLoop(ctx)
	go h.runMetricsIngestion(ctx)
	go h.runHealthChecks(ctx)
	go h.runTunnelQualityProber(ctx)
	go h.runValidateLicenseJob(ctx)
	go h.runNftablesTrafficCollectLoop(ctx)
}

func (h *Handler) runValidateLicenseJob(ctx context.Context) {
	defer h.jobsWG.Done()
	ticker := time.NewTicker(12 * time.Hour)
	defer ticker.Stop()

	for {
		select {
		case <-ctx.Done():
			return
		case <-ticker.C:
			h.validateLicenseJob()
		}
	}
}

func (h *Handler) validateLicenseJob() {
	if h == nil || h.repo == nil {
		return
	}

	accountID := "1bc96cac-09de-4cf4-af34-26afdad63a90"

	key, _ := h.repo.GetViteConfigValue("license_key")
	isCommercial, _ := h.repo.GetViteConfigValue("is_commercial")

	if key == "" || isCommercial != "true" {
		return // Nothing to validate
	}

	fingerprint, _ := h.repo.GetViteConfigValue("machine_fingerprint")
	client := license.NewKeygenClient(accountID, "")
	valResp, err := client.ValidateKeyWithFingerprint(key, fingerprint)

	if err != nil {
		// Network error or timeout. Grace period by not revoking immediately here.
		return
	}

	if !valResp.Meta.Valid {
		// License is invalid (e.g., revoked, suspended, expired). Downgrade the system.
		now := time.Now().UnixMilli()
		_ = h.repo.UpsertConfig("is_commercial", "false", now)
	} else {
		now := time.Now().UnixMilli()
		expiry := valResp.Data.Attributes.Expiry
		if expiry == "" {
			expiry = "never"
		}
		_ = h.repo.UpsertConfig("license_expiry", expiry, now)
	}
}

func (h *Handler) StopBackgroundJobs() {
	if h == nil {
		return
	}

	h.jobsMu.Lock()
	if !h.jobsStarted {
		h.jobsMu.Unlock()
		return
	}
	cancel := h.jobsCancel
	h.jobsCancel = nil
	h.jobsStarted = false
	h.jobsMu.Unlock()

	if cancel != nil {
		cancel()
	}
	h.jobsWG.Wait()
}

func (h *Handler) runMetricsIngestion(ctx context.Context) {
	defer h.jobsWG.Done()
	if h.metrics != nil {
		h.metrics.Start(ctx)
	}
}

func (h *Handler) runHealthChecks(ctx context.Context) {
	defer h.jobsWG.Done()
	if h.healthCheck != nil {
		h.healthCheck.Start(ctx)
	}
}

func (h *Handler) runTunnelQualityProber(ctx context.Context) {
	defer h.jobsWG.Done()
	if h == nil || h.qualityProber == nil {
		return
	}

	h.qualityProber.Start(ctx)
}

func (h *Handler) runNftablesTrafficCollectLoop(ctx context.Context) {
	defer h.jobsWG.Done()
	h.runNftablesStartupReconcile(ctx)
	select {
	case <-ctx.Done():
		return
	default:
		h.runNftablesTrafficCollectJob(time.Now())
	}

	interval := nftablesTrafficCollectInterval
	if interval <= 0 {
		interval = 30 * time.Second
	}
	ticker := time.NewTicker(interval)
	defer ticker.Stop()

	for {
		select {
		case <-ctx.Done():
			return
		case <-ticker.C:
			h.runNftablesTrafficCollectJob(time.Now())
		}
	}
}

func (h *Handler) runNftablesStartupReconcile(ctx context.Context) {
	if h == nil || h.repo == nil {
		return
	}
	nodes, err := h.repo.ListNftablesNodesForCollection()
	if err != nil {
		log.Printf("nftables startup reconcile failed op=list_nodes err=%v", err)
		return
	}
	for _, node := range nodes {
		select {
		case <-ctx.Done():
			return
		default:
		}
		if err := h.syncNftablesNode(node.NodeID); err != nil {
			log.Printf("nftables startup reconcile failed node_id=%d err=%v", node.NodeID, err)
		}
	}
}

func (h *Handler) runHourlyStatsLoop(ctx context.Context) {
	defer h.jobsWG.Done()

	for {
		wait := durationUntilNextHour(time.Now())
		timer := time.NewTimer(wait)
		select {
		case <-ctx.Done():
			if !timer.Stop() {
				<-timer.C
			}
			return
		case <-timer.C:
			h.runStatisticsFlowJob(time.Now())
		}
	}
}

func (h *Handler) runDailyMaintenanceLoop(ctx context.Context) {
	defer h.jobsWG.Done()

	for {
		wait := durationUntilNextDailyMaintenance(time.Now())
		timer := time.NewTimer(wait)
		select {
		case <-ctx.Done():
			if !timer.Stop() {
				<-timer.C
			}
			return
		case <-timer.C:
			h.runResetAndExpiryJob(time.Now())
		}
	}
}

func durationUntilNextHour(now time.Time) time.Duration {
	next := now.Truncate(time.Hour).Add(time.Hour)
	return next.Sub(now)
}

func durationUntilNextDailyMaintenance(now time.Time) time.Duration {
	next := time.Date(now.Year(), now.Month(), now.Day(), 0, 0, 5, 0, now.Location())
	if !next.After(now) {
		next = next.Add(24 * time.Hour)
	}
	return next.Sub(now)
}

func (h *Handler) runStatisticsFlowJob(now time.Time) {
	if h == nil || h.repo == nil {
		return
	}

	nowMs := now.UnixMilli()
	cutoffMs := nowMs - int64((48*time.Hour)/time.Millisecond)
	_ = h.repo.PurgeOldStatisticsFlows(cutoffMs)

	hourMark := now.Truncate(time.Hour)
	hourText := hourMark.Format("15:04")
	createdTime := hourMark.UnixMilli()

	users, err := h.repo.ListAllUserFlowSnapshots()
	if err != nil {
		return
	}

	for _, user := range users {
		currentTotal := user.InFlow + user.OutFlow
		increment := currentTotal

		lastTotal, err := h.repo.GetLastStatisticsFlowTotal(user.UserID)
		if err == nil && lastTotal.Valid {
			increment = currentTotal - lastTotal.Int64
			if increment < 0 {
				increment = currentTotal
			}
		}

		_ = h.repo.CreateStatisticsFlow(user.UserID, increment, currentTotal, hourText, createdTime)
	}
}

func (h *Handler) runResetAndExpiryJob(now time.Time) {
	if h == nil || h.repo == nil {
		return
	}

	h.resetMonthlyFlow(now)
	h.resetUserQuotaWindows(now)
	h.disableExpiredUsers(now.UnixMilli())
	h.disableExpiredUserTunnels(now.UnixMilli())
}

func (h *Handler) resetMonthlyFlow(now time.Time) {
	currentDay := now.Day()
	lastDay := time.Date(now.Year(), now.Month()+1, 0, 0, 0, 0, 0, now.Location()).Day()

	_ = h.repo.ResetUserMonthlyFlow(currentDay, lastDay)
	_ = h.repo.ResetUserTunnelMonthlyFlow(currentDay, lastDay)
}

func (h *Handler) disableExpiredUsers(nowMs int64) {
	userIDs, err := h.repo.ListExpiredActiveUserIDs(nowMs)
	if err != nil {
		return
	}

	for _, userID := range userIDs {
		forwards, err := h.listActiveForwardsByUser(userID)
		if err == nil {
			h.pauseForwardRecords(forwards, nowMs)
		}
		_ = h.repo.DisableUser(userID)
	}
}

func (h *Handler) disableExpiredUserTunnels(nowMs int64) {
	items, err := h.repo.ListExpiredActiveUserTunnels(nowMs)
	if err != nil {
		return
	}

	for _, item := range items {
		forwards, err := h.listActiveForwardsByUserTunnel(item.UserID, item.TunnelID)
		if err == nil {
			h.pauseForwardRecords(forwards, nowMs)
		}
		_ = h.repo.DisableUserTunnel(item.ID)
	}
}

func (h *Handler) runNodeRenewalCycleLoop(ctx context.Context) {
	defer h.jobsWG.Done()

	for {
		wait := durationUntilNextNodeRenewalCycle(time.Now())
		timer := time.NewTimer(wait)
		select {
		case <-ctx.Done():
			if !timer.Stop() {
				<-timer.C
			}
			return
		case <-timer.C:
			h.runNodeRenewalCycleJob(time.Now())
		}
	}
}

func durationUntilNextNodeRenewalCycle(now time.Time) time.Duration {
	next := now.Truncate(6 * time.Hour).Add(6 * time.Hour)
	return next.Sub(now)
}

func (h *Handler) runNodeRenewalCycleJob(now time.Time) {
	if h == nil || h.repo == nil {
		return
	}

	advanced, err := h.repo.AdvanceNodeRenewalCycles(now.UnixMilli())
	if err != nil {
		return
	}

	_ = advanced
}