package handler

import (
	"context"
	"time"
)

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(3)
	h.jobsMu.Unlock()

	go h.runHourlyStatsLoop(ctx)
	go h.runDailyMaintenanceLoop(ctx)
	go h.runNodeRenewalCycleLoop(ctx)
}

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) 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.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
}