package models

import (
	"log"
	"strings"
	"sync"
	"time"

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

var (
	schedMu     sync.Mutex
	schedCron   *cron.Cron
	entryTarget = map[cron.EntryID]targetRef{}
)

type targetRef struct {
	scope    string // "node" or "svc:<serviceID>"
	targetID string
}

// StartScheduler starts the in-process cron scheduler and performs an initial
// sync from the current configuration. Call once from main.go before
// beego.Run() — not from the scan/info CLI paths.
func StartScheduler() {
	schedMu.Lock()
	schedCron = cron.New(cron.WithChain(cron.Recover(cron.DefaultLogger)))
	schedCron.Start()
	schedMu.Unlock()
	SyncSchedule()
}

// SyncSchedule rebuilds all cron entries from the current backup target
// definitions (node + every service). Called once at startup and after any
// target add/update/delete so the running scheduler reflects the latest
// definitions.
func SyncSchedule() {
	schedMu.Lock()
	defer schedMu.Unlock()
	if schedCron == nil {
		return
	}
	for _, e := range schedCron.Entries() {
		schedCron.Remove(e.ID)
	}
	entryTarget = map[cron.EntryID]targetRef{}

	mu.RLock()
	nodeTargets := make([]BackupTarget, len(cfg.Node.Backup.Targets))
	copy(nodeTargets, cfg.Node.Backup.Targets)
	services := make([]Service, len(cfg.Services))
	copy(services, cfg.Services)
	mu.RUnlock()

	for _, t := range nodeTargets {
		registerJob("node", t)
	}
	for _, s := range services {
		if s.Backup == nil {
			continue
		}
		for _, t := range s.Backup.Targets {
			registerJob("svc:"+s.ID, t)
		}
	}
	refreshNextRunLocked()
}

// registerJob schedules a single target's cron job. Caller must hold schedMu.
func registerJob(scope string, t BackupTarget) {
	if t.Schedule == "" {
		return
	}
	schedule, err := cron.ParseStandard(t.Schedule)
	if err != nil {
		// Already validated at CRUD time; defensively skip a bad schedule
		// rather than let it wedge the whole sync.
		return
	}
	targetID := t.ID
	job := cron.NewChain(cron.SkipIfStillRunning(cron.DefaultLogger)).Then(cron.FuncJob(func() {
		runScheduledTarget(scope, targetID)
	}))
	id := schedCron.Schedule(schedule, job)
	entryTarget[id] = targetRef{scope: scope, targetID: targetID}
}

func runScheduledTarget(scope, targetID string) {
	var err error
	switch {
	case scope == "node":
		err = RunNodeBackup([]string{targetID})
	case strings.HasPrefix(scope, "svc:"):
		err = RunServiceBackup(strings.TrimPrefix(scope, "svc:"), []string{targetID})
	}
	if err != nil {
		log.Printf("nodemaster: scheduled backup %s/%s failed: %v", scope, targetID, err)
	}
	schedMu.Lock()
	refreshNextRunLocked()
	schedMu.Unlock()
}

// refreshNextRunLocked writes each scheduled target's NextRun from the cron
// entries' computed next-fire time. Caller must hold schedMu.
func refreshNextRunLocked() {
	if schedCron == nil {
		return
	}
	updates := map[targetRef]time.Time{}
	for _, e := range schedCron.Entries() {
		if ref, ok := entryTarget[e.ID]; ok {
			updates[ref] = e.Next
		}
	}
	if len(updates) == 0 {
		return
	}
	mu.Lock()
	for ref, next := range updates {
		n := next
		if ref.scope == "node" {
			for i, t := range cfg.Node.Backup.Targets {
				if t.ID == ref.targetID {
					cfg.Node.Backup.Targets[i].NextRun = &n
					break
				}
			}
			continue
		}
		svcID := strings.TrimPrefix(ref.scope, "svc:")
		for i, s := range cfg.Services {
			if s.ID != svcID || s.Backup == nil {
				continue
			}
			for j, t := range s.Backup.Targets {
				if t.ID == ref.targetID {
					cfg.Services[i].Backup.Targets[j].NextRun = &n
					break
				}
			}
			break
		}
	}
	_ = persist()
	mu.Unlock()
}