package task

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

	"gorm.io/gorm"

	"spider/internal/model"
)

// Scheduler checks enabled ScheduleJobs every minute and starts tasks when due.
type Scheduler struct {
	db      *gorm.DB
	manager *Manager

	mu   sync.Mutex
	jobs []model.ScheduleJob

	stopCh chan struct{}
	done   chan struct{}
}

// NewScheduler creates a new Scheduler.
func NewScheduler(db *gorm.DB, mgr *Manager) *Scheduler {
	return &Scheduler{
		db:      db,
		manager: mgr,
		stopCh:  make(chan struct{}),
		done:    make(chan struct{}),
	}
}

// Start loads jobs from DB and begins the ticker loop.
func (s *Scheduler) Start() {
	s.loadJobs()
	go s.loop()
	log.Println("[scheduler] started")
}

// Stop signals the loop to exit and waits.
func (s *Scheduler) Stop() {
	close(s.stopCh)
	<-s.done
	log.Println("[scheduler] stopped")
}

// Reload re-reads all enabled jobs from the database.
func (s *Scheduler) Reload() {
	s.loadJobs()
	log.Println("[scheduler] reloaded jobs")
}

func (s *Scheduler) loadJobs() {
	var jobs []model.ScheduleJob
	if err := s.db.Where("enabled = ?", true).Find(&jobs).Error; err != nil {
		log.Printf("[scheduler] load jobs error: %v", err)
		return
	}
	// Calculate NextRunAt for any job that doesn't have one yet
	now := time.Now()
	for i := range jobs {
		if jobs[i].NextRunAt == nil {
			next, err := calcNextRun(jobs[i].CronExpr, now)
			if err != nil {
				log.Printf("[scheduler] bad cron for job %d (%s): %v", jobs[i].ID, jobs[i].CronExpr, err)
				continue
			}
			jobs[i].NextRunAt = &next
			s.db.Model(&jobs[i]).Update("next_run_at", next)
		}
	}
	s.mu.Lock()
	s.jobs = jobs
	s.mu.Unlock()
}

func (s *Scheduler) loop() {
	defer close(s.done)

	ticker := time.NewTicker(1 * time.Minute)
	defer ticker.Stop()

	for {
		select {
		case <-s.stopCh:
			return
		case now := <-ticker.C:
			s.tick(now)
		}
	}
}

func (s *Scheduler) tick(now time.Time) {
	defer func() {
		if r := recover(); r != nil {
			log.Printf("[scheduler] PANIC in tick: %v", r)
		}
	}()

	s.mu.Lock()
	jobs := make([]model.ScheduleJob, len(s.jobs))
	copy(jobs, s.jobs)
	s.mu.Unlock()

	for _, job := range jobs {
		if job.NextRunAt == nil {
			continue
		}
		if !now.Before(*job.NextRunAt) {
			s.runJob(job, now)
		}
	}
}

func (s *Scheduler) runJob(job model.ScheduleJob, now time.Time) {
	defer func() {
		if r := recover(); r != nil {
			log.Printf("[scheduler] PANIC running job %d: %v", job.ID, r)
		}
	}()

	log.Printf("[scheduler] triggering job %d (%s) plugin=%s", job.ID, job.Name, job.PluginName)

	req := StartRequest{
		PluginName: job.PluginName,
	}
	_, err := s.manager.StartTask(req)
	if err != nil {
		log.Printf("[scheduler] job %d start error: %v", job.ID, err)
	}

	s.manager.notify("schedule_run", "定时任务触发",
		fmt.Sprintf("定时任务 [%s] (插件: %s) 已触发执行", job.Name, job.PluginName))

	// Update last_run_at and next_run_at
	lastRun := now
	next, calcErr := calcNextRun(job.CronExpr, now)
	updates := map[string]any{"last_run_at": lastRun}
	if calcErr == nil {
		updates["next_run_at"] = next
	}
	s.db.Model(&model.ScheduleJob{}).Where("id = ?", job.ID).Updates(updates)

	// Update in-memory copy
	s.mu.Lock()
	for i := range s.jobs {
		if s.jobs[i].ID == job.ID {
			s.jobs[i].LastRunAt = &lastRun
			if calcErr == nil {
				s.jobs[i].NextRunAt = &next
			}
			break
		}
	}
	s.mu.Unlock()
}

// calcNextRun computes the next run time from a cron expression.
// Supported formats:
//   - */N * * * *  — every N minutes
//   - 0 H * * *    — daily at hour H
//   - 0 H * * D    — weekly on day D at hour H (0=Sunday)
func calcNextRun(expr string, after time.Time) (time.Time, error) {
	parts := strings.Fields(expr)
	if len(parts) != 5 {
		return time.Time{}, fmt.Errorf("invalid cron: need 5 fields, got %d", len(parts))
	}

	minute, hour, _, _, dow := parts[0], parts[1], parts[2], parts[3], parts[4]

	// Case 1: */N * * * * — every N minutes
	if strings.HasPrefix(minute, "*/") && hour == "*" && dow == "*" {
		nStr := strings.TrimPrefix(minute, "*/")
		n, err := strconv.Atoi(nStr)
		if err != nil || n <= 0 {
			return time.Time{}, fmt.Errorf("invalid interval: %s", nStr)
		}
		next := after.Add(time.Duration(n) * time.Minute)
		// Truncate seconds
		next = next.Truncate(time.Minute)
		return next, nil
	}

	// Minute must be a number for the remaining patterns
	m, err := strconv.Atoi(minute)
	if err != nil {
		return time.Time{}, fmt.Errorf("invalid minute: %s", minute)
	}
	h, err := strconv.Atoi(hour)
	if err != nil {
		return time.Time{}, fmt.Errorf("invalid hour: %s", hour)
	}

	// Case 2: 0 H * * * — daily at hour H
	if dow == "*" {
		candidate := time.Date(after.Year(), after.Month(), after.Day(), h, m, 0, 0, after.Location())
		if !candidate.After(after) {
			candidate = candidate.AddDate(0, 0, 1)
		}
		return candidate, nil
	}

	// Case 3: 0 H * * D — weekly on day D at hour H
	d, err := strconv.Atoi(dow)
	if err != nil {
		return time.Time{}, fmt.Errorf("invalid day of week: %s", dow)
	}
	targetDay := time.Weekday(d)
	candidate := time.Date(after.Year(), after.Month(), after.Day(), h, m, 0, 0, after.Location())
	// Move to target weekday
	daysUntil := int(targetDay) - int(candidate.Weekday())
	if daysUntil < 0 {
		daysUntil += 7
	}
	candidate = candidate.AddDate(0, 0, daysUntil)
	if !candidate.After(after) {
		candidate = candidate.AddDate(0, 0, 7)
	}
	return candidate, nil
}