package runtimelogs

import (
	"context"
	"fmt"
	"log"
	"strings"
	"sync"
	"time"

	"evobgp/internal/store"

	"github.com/robfig/cron/v3"
)

// SchedulerDeps configures the runtime log auto-cleanup background scheduler.
type SchedulerDeps struct {
	Service      *Service
	Store        store.Backend
	PolicyTenant string
}

// ResolvePolicyTenant picks the tenant whose settings drive auto-cleanup.
func ResolvePolicyTenant(st store.Backend, explicit string) (string, error) {
	explicit = strings.TrimSpace(explicit)
	if explicit != "" {
		return explicit, nil
	}
	if st == nil {
		return "", fmt.Errorf("runtimelogs: store required")
	}
	ids, err := st.ListTenantIDs()
	if err != nil {
		return "", err
	}
	for _, id := range ids {
		settings, err := st.ListGlobalSettings(id)
		if err != nil {
			continue
		}
		if PolicyFromSettings(settings).Enabled {
			return id, nil
		}
	}
	if len(ids) > 0 {
		return ids[0], nil
	}
	return "", fmt.Errorf("runtimelogs: no tenants configured")
}

// StartAutoCleanupScheduler runs periodic auto-cleanup on evobgp-all when FS is available.
func StartAutoCleanupScheduler(ctx context.Context, deps SchedulerDeps, tick time.Duration) {
	if deps.Service == nil || !deps.Service.Available() {
		log.Printf("runtimelogs: auto-cleanup scheduler disabled (FS unavailable)")
		return
	}
	if deps.Store == nil {
		log.Printf("runtimelogs: auto-cleanup scheduler disabled (no store)")
		return
	}
	if tick <= 0 {
		tick = 30 * time.Second
	}

	go func() {
		parser := cron.NewParser(cron.Minute | cron.Hour | cron.Dom | cron.Month | cron.Dow)
		var mu sync.Mutex
		lastFired := map[string]time.Time{}

		t := time.NewTicker(tick)
		defer t.Stop()
		for {
			select {
			case <-ctx.Done():
				return
			case <-t.C:
				tenantID, err := ResolvePolicyTenant(deps.Store, deps.PolicyTenant)
				if err != nil {
					continue
				}
				settings, err := deps.Store.ListGlobalSettings(tenantID)
				if err != nil {
					continue
				}
				policy := PolicyFromSettings(settings)
				if !policy.Enabled {
					continue
				}
				sched, err := parser.Parse(policy.Schedule)
				if err != nil {
					log.Printf("runtimelogs: invalid cron %q: %v", policy.Schedule, err)
					continue
				}

				now := time.Now().UTC()
				mu.Lock()
				prev := lastFired[policy.Schedule]
				if prev.IsZero() {
					prev = now.Add(-time.Minute)
				}
				next := sched.Next(prev)
				if next.After(now) {
					mu.Unlock()
					continue
				}
				slot := next.Unix() / 60
				if lf, ok := lastFired[policy.Schedule]; ok && lf.Unix()/60 == slot {
					mu.Unlock()
					continue
				}
				lastFired[policy.Schedule] = next
				mu.Unlock()

				_, err = RunAutoCleanup(ctx, AutoCleanupDeps{
					Service:  deps.Service,
					Store:    deps.Store,
					TenantID: tenantID,
				}, policy, false, "scheduler")
				if err != nil {
					log.Printf("runtimelogs: auto-cleanup run failed: %v", err)
				}
			}
		}
	}()
	log.Printf("runtimelogs: auto-cleanup scheduler started (tick=%s)", tick)
}