package engine

import (
	"context"
	"fmt"
	"sync"
	"sync/atomic"
	"time"

	"github.com/robfig/cron/v3"
	"go.uber.org/zap"
)

// Job 定时任务接口
type Job interface {
	// ID 返回任务唯一标识
	ID() string
	// Start 启动任务
	Start(ctx context.Context) error
	// Stop 停止任务
	Stop() error
	// IsRunning 检查任务是否正在运行
	IsRunning() bool
	// NextRun 返回下次执行时间
	NextRun() time.Time
}

// JobFunc 任务执行函数类型
type JobFunc func(ctx context.Context) error

// Scheduler 定时任务调度器
type Scheduler struct {
	jobs    map[string]Job
	mu      sync.RWMutex
	logger  *zap.Logger
	ctx     context.Context
	cancel  context.CancelFunc
	wg      sync.WaitGroup
	running int32
}

// NewScheduler 创建新的调度器
func NewScheduler(logger *zap.Logger) *Scheduler {
	ctx, cancel := context.WithCancel(context.Background())
	return &Scheduler{
		jobs:   make(map[string]Job),
		logger: logger.Named("scheduler"),
		ctx:    ctx,
		cancel: cancel,
	}
}

// Start 启动调度器
func (s *Scheduler) Start() error {
	if !atomic.CompareAndSwapInt32(&s.running, 0, 1) {
		return fmt.Errorf("scheduler is already running")
	}

	s.mu.RLock()
	defer s.mu.RUnlock()

	// 启动所有任务
	for id, job := range s.jobs {
		if err := job.Start(s.ctx); err != nil {
			s.logger.Error("Failed to start job",
				zap.String("job_id", id),
				zap.Error(err))
			continue
		}
		s.logger.Info("Job started", zap.String("job_id", id))
	}

	s.logger.Info("Scheduler started", zap.Int("job_count", len(s.jobs)))
	return nil
}

// Stop 停止调度器
func (s *Scheduler) Stop() error {
	if !atomic.CompareAndSwapInt32(&s.running, 1, 0) {
		return fmt.Errorf("scheduler is not running")
	}

	s.cancel()

	s.mu.RLock()
	defer s.mu.RUnlock()

	// 停止所有任务
	for id, job := range s.jobs {
		if err := job.Stop(); err != nil {
			s.logger.Error("Failed to stop job",
				zap.String("job_id", id),
				zap.Error(err))
			continue
		}
		s.logger.Info("Job stopped", zap.String("job_id", id))
	}

	s.wg.Wait()
	s.logger.Info("Scheduler stopped")
	return nil
}

// AddJob 添加任务
func (s *Scheduler) AddJob(job Job) error {
	s.mu.Lock()
	defer s.mu.Unlock()

	id := job.ID()
	if _, exists := s.jobs[id]; exists {
		return fmt.Errorf("job with id %s already exists", id)
	}

	s.jobs[id] = job

	// 如果调度器正在运行，立即启动任务
	if atomic.LoadInt32(&s.running) == 1 {
		if err := job.Start(s.ctx); err != nil {
			delete(s.jobs, id)
			return fmt.Errorf("failed to start job: %w", err)
		}
		s.logger.Info("Job added and started", zap.String("job_id", id))
	} else {
		s.logger.Info("Job added", zap.String("job_id", id))
	}

	return nil
}

// RemoveJob 移除任务
func (s *Scheduler) RemoveJob(id string) error {
	s.mu.Lock()
	defer s.mu.Unlock()

	job, exists := s.jobs[id]
	if !exists {
		return fmt.Errorf("job with id %s not found", id)
	}

	if err := job.Stop(); err != nil {
		s.logger.Error("Failed to stop job during removal",
			zap.String("job_id", id),
			zap.Error(err))
	}

	delete(s.jobs, id)
	s.logger.Info("Job removed", zap.String("job_id", id))
	return nil
}

// GetJob 获取任务
func (s *Scheduler) GetJob(id string) (Job, bool) {
	s.mu.RLock()
	defer s.mu.RUnlock()
	job, exists := s.jobs[id]
	return job, exists
}

// GetAllJobs 获取所有任务
func (s *Scheduler) GetAllJobs() map[string]Job {
	s.mu.RLock()
	defer s.mu.RUnlock()

	result := make(map[string]Job, len(s.jobs))
	for id, job := range s.jobs {
		result[id] = job
	}
	return result
}

// IsRunning 检查调度器是否正在运行
func (s *Scheduler) IsRunning() bool {
	return atomic.LoadInt32(&s.running) == 1
}

// ============================================================================
// Job 实现
// ============================================================================

// CronJob 基于 Cron 表达式的任务
type CronJob struct {
	id      string
	spec    string
	handler JobFunc
	cron    *cron.Cron
	logger  *zap.Logger
	running int32
	nextRun time.Time
	mu      sync.RWMutex
}

// NewCronJob 创建 Cron 任务
func NewCronJob(id, spec string, handler JobFunc, logger *zap.Logger) (*CronJob, error) {
	parser := cron.NewParser(cron.Second | cron.Minute | cron.Hour | cron.Dom | cron.Month | cron.Dow | cron.Descriptor)
	c := cron.New(cron.WithParser(parser), cron.WithChain(cron.Recover(cron.DefaultLogger)))

	job := &CronJob{
		id:      id,
		spec:    spec,
		handler: handler,
		cron:    c,
		logger:  logger.Named("cron-job").With(zap.String("job_id", id)),
	}

	// 添加任务到 cron
	_, err := c.AddFunc(spec, func() {
		ctx := context.Background()
		if err := handler(ctx); err != nil {
			job.logger.Error("Cron job execution failed", zap.Error(err))
		}
		// 更新下次执行时间
		entries := c.Entries()
		job.mu.Lock()
		if len(entries) > 0 {
			// 找到最近的执行时间
			next := entries[0].Next
			for _, entry := range entries {
				if entry.Next.Before(next) {
					next = entry.Next
				}
			}
			job.nextRun = next
		}
		job.mu.Unlock()
	})

	if err != nil {
		return nil, fmt.Errorf("invalid cron spec: %w", err)
	}

	// 计算初始下次执行时间（需要先启动 cron 才能计算）
	// 这里先设置为零值，在 Start 时再计算
	job.mu.Lock()
	job.nextRun = time.Time{}
	job.mu.Unlock()

	return job, nil
}

func (j *CronJob) ID() string {
	return j.id
}

func (j *CronJob) Start(ctx context.Context) error {
	if !atomic.CompareAndSwapInt32(&j.running, 0, 1) {
		return fmt.Errorf("job is already running")
	}

	j.cron.Start()
	j.logger.Info("Cron job started", zap.String("spec", j.spec))

	// 更新下次执行时间
	entries := j.cron.Entries()
	if len(entries) > 0 {
		j.mu.Lock()
		// 找到最近的执行时间
		next := entries[0].Next
		for _, entry := range entries {
			if entry.Next.Before(next) {
				next = entry.Next
			}
		}
		j.nextRun = next
		j.mu.Unlock()
	}

	return nil
}

func (j *CronJob) Stop() error {
	if !atomic.CompareAndSwapInt32(&j.running, 1, 0) {
		return fmt.Errorf("job is not running")
	}

	ctx := j.cron.Stop()
	<-ctx.Done()
	j.logger.Info("Cron job stopped")
	return nil
}

func (j *CronJob) IsRunning() bool {
	return atomic.LoadInt32(&j.running) == 1
}

func (j *CronJob) NextRun() time.Time {
	j.mu.RLock()
	defer j.mu.RUnlock()
	return j.nextRun
}

// IntervalJob 固定间隔的任务
type IntervalJob struct {
	id       string
	interval time.Duration
	handler  JobFunc
	logger   *zap.Logger
	running  int32
	nextRun  time.Time
	mu       sync.RWMutex
	ticker   *time.Ticker
	ctx      context.Context
	cancel   context.CancelFunc
	wg       sync.WaitGroup
}

// NewIntervalJob 创建固定间隔任务
func NewIntervalJob(id string, interval time.Duration, handler JobFunc, logger *zap.Logger) *IntervalJob {
	return &IntervalJob{
		id:       id,
		interval: interval,
		handler:  handler,
		logger:   logger.Named("interval-job").With(zap.String("job_id", id)),
	}
}

func (j *IntervalJob) ID() string {
	return j.id
}

func (j *IntervalJob) Start(ctx context.Context) error {
	if !atomic.CompareAndSwapInt32(&j.running, 0, 1) {
		return fmt.Errorf("job is already running")
	}

	j.ctx, j.cancel = context.WithCancel(ctx)
	j.ticker = time.NewTicker(j.interval)

	j.mu.Lock()
	j.nextRun = time.Now().Add(j.interval)
	j.mu.Unlock()

	j.wg.Add(1)
	go j.run()

	j.logger.Info("Interval job started", zap.Duration("interval", j.interval))
	return nil
}

func (j *IntervalJob) run() {
	defer j.wg.Done()

	// 立即执行一次（可选，根据需求调整）
	// if err := j.handler(j.ctx); err != nil {
	// 	j.logger.Error("Interval job execution failed", zap.Error(err))
	// }

	for {
		select {
		case <-j.ticker.C:
			j.mu.Lock()
			j.nextRun = time.Now().Add(j.interval)
			j.mu.Unlock()

			if err := j.handler(j.ctx); err != nil {
				j.logger.Error("Interval job execution failed", zap.Error(err))
			}
		case <-j.ctx.Done():
			return
		}
	}
}

func (j *IntervalJob) Stop() error {
	if !atomic.CompareAndSwapInt32(&j.running, 1, 0) {
		return fmt.Errorf("job is not running")
	}

	if j.cancel != nil {
		j.cancel()
	}
	if j.ticker != nil {
		j.ticker.Stop()
	}
	j.wg.Wait()

	j.logger.Info("Interval job stopped")
	return nil
}

func (j *IntervalJob) IsRunning() bool {
	return atomic.LoadInt32(&j.running) == 1
}

func (j *IntervalJob) NextRun() time.Time {
	j.mu.RLock()
	defer j.mu.RUnlock()
	return j.nextRun
}

// OnceJob 单次延迟执行的任务
type OnceJob struct {
	id      string
	delay   time.Duration
	handler JobFunc
	logger  *zap.Logger
	running int32
	nextRun time.Time
	mu      sync.RWMutex
	timer   *time.Timer
	ctx     context.Context
	cancel  context.CancelFunc
	wg      sync.WaitGroup
}

// NewOnceJob 创建单次延迟执行任务
func NewOnceJob(id string, delay time.Duration, handler JobFunc, logger *zap.Logger) *OnceJob {
	return &OnceJob{
		id:      id,
		delay:   delay,
		handler: handler,
		logger:  logger.Named("once-job").With(zap.String("job_id", id)),
	}
}

func (j *OnceJob) ID() string {
	return j.id
}

func (j *OnceJob) Start(ctx context.Context) error {
	if !atomic.CompareAndSwapInt32(&j.running, 0, 1) {
		return fmt.Errorf("job is already running")
	}

	j.ctx, j.cancel = context.WithCancel(ctx)
	j.timer = time.NewTimer(j.delay)

	j.mu.Lock()
	j.nextRun = time.Now().Add(j.delay)
	j.mu.Unlock()

	j.wg.Add(1)
	go j.run()

	j.logger.Info("Once job started", zap.Duration("delay", j.delay))
	return nil
}

func (j *OnceJob) run() {
	defer j.wg.Done()

	select {
	case <-j.timer.C:
		if err := j.handler(j.ctx); err != nil {
			j.logger.Error("Once job execution failed", zap.Error(err))
		}
		atomic.StoreInt32(&j.running, 0)
	case <-j.ctx.Done():
		if !j.timer.Stop() {
			<-j.timer.C
		}
		return
	}
}

func (j *OnceJob) Stop() error {
	if !atomic.CompareAndSwapInt32(&j.running, 1, 0) {
		return fmt.Errorf("job is not running")
	}

	if j.cancel != nil {
		j.cancel()
	}
	if j.timer != nil {
		if !j.timer.Stop() {
			<-j.timer.C
		}
	}
	j.wg.Wait()

	j.logger.Info("Once job stopped")
	return nil
}

func (j *OnceJob) IsRunning() bool {
	return atomic.LoadInt32(&j.running) == 1
}

func (j *OnceJob) NextRun() time.Time {
	j.mu.RLock()
	defer j.mu.RUnlock()
	return j.nextRun
}

// ============================================================================
// 全局调度器 API（链式风格，延迟注册）
// ============================================================================

var (
	globalJobRegistry = make([]JobBuilder, 0)
	globalJobMu       sync.RWMutex
	jobCounter        int64
)

// JobBuilder 任务构建器接口（延迟注册）
type JobBuilder interface {
	// Build 构建任务实例（由依赖注入系统调用）
	Build(logger *zap.Logger) (Job, error)
}

// generateJobID 生成任务 ID
func generateJobID(prefix string) string {
	counter := atomic.AddInt64(&jobCounter, 1)
	return fmt.Sprintf("%s_%d", prefix, counter)
}

// CronJobBuilder Cron 任务构建器
type CronJobBuilder struct {
	id      string
	spec    string
	handler JobFunc
}

// Cron 创建 Cron 任务构建器（在 init 函数中调用）
func Cron(spec string) *CronJobBuilder {
	return &CronJobBuilder{
		id:   generateJobID("cron"),
		spec: spec,
	}
}

// Handle 设置处理函数并注册到全局注册表（延迟注册）
func (b *CronJobBuilder) Handle(handler JobFunc) {
	b.handler = handler
	if b.handler == nil {
		panic("scheduler: handler cannot be nil")
	}

	globalJobMu.Lock()
	defer globalJobMu.Unlock()
	globalJobRegistry = append(globalJobRegistry, b)
}

// Build 构建 Cron 任务
func (b *CronJobBuilder) Build(logger *zap.Logger) (Job, error) {
	return NewCronJob(b.id, b.spec, b.handler, logger)
}

// IntervalJobBuilder 固定间隔任务构建器
type IntervalJobBuilder struct {
	id       string
	interval time.Duration
	handler  JobFunc
}

// Interval 创建固定间隔任务构建器（在 init 函数中调用）
func Interval(interval time.Duration) *IntervalJobBuilder {
	return &IntervalJobBuilder{
		id:       generateJobID("interval"),
		interval: interval,
	}
}

// Handle 设置处理函数并注册到全局注册表（延迟注册）
func (b *IntervalJobBuilder) Handle(handler JobFunc) {
	b.handler = handler
	if b.handler == nil {
		panic("scheduler: handler cannot be nil")
	}

	globalJobMu.Lock()
	defer globalJobMu.Unlock()
	globalJobRegistry = append(globalJobRegistry, b)
}

// Build 构建固定间隔任务
func (b *IntervalJobBuilder) Build(logger *zap.Logger) (Job, error) {
	return NewIntervalJob(b.id, b.interval, b.handler, logger), nil
}

// OnceJobBuilder 单次延迟任务构建器
type OnceJobBuilder struct {
	id      string
	delay   time.Duration
	handler JobFunc
}

// Once 创建单次延迟任务构建器（在 init 函数中调用）
func Once(delay time.Duration) *OnceJobBuilder {
	return &OnceJobBuilder{
		id:    generateJobID("once"),
		delay: delay,
	}
}

// Handle 设置处理函数并注册到全局注册表（延迟注册）
func (b *OnceJobBuilder) Handle(handler JobFunc) {
	b.handler = handler
	if b.handler == nil {
		panic("scheduler: handler cannot be nil")
	}

	globalJobMu.Lock()
	defer globalJobMu.Unlock()
	globalJobRegistry = append(globalJobRegistry, b)
}

// Build 构建单次延迟任务
func (b *OnceJobBuilder) Build(logger *zap.Logger) (Job, error) {
	return NewOnceJob(b.id, b.delay, b.handler, logger), nil
}

// LoadAllJobs 加载所有已注册的任务（由依赖注入系统调用）
func LoadAllJobs(scheduler *Scheduler, logger *zap.Logger) error {
	globalJobMu.RLock()
	defer globalJobMu.RUnlock()

	for i, builder := range globalJobRegistry {
		job, err := builder.Build(logger)
		if err != nil {
			logger.Error("Failed to build job",
				zap.Int("index", i),
				zap.Error(err))
			continue
		}

		if err := scheduler.AddJob(job); err != nil {
			logger.Error("Failed to add job to scheduler",
				zap.String("job_id", job.ID()),
				zap.Error(err))
			continue
		}

		logger.Debug("Job loaded",
			zap.String("job_id", job.ID()))
	}

	logger.Info("All scheduled jobs loaded",
		zap.Int("job_count", len(globalJobRegistry)))

	return nil
}