package config

import (
	"log"
	"path/filepath"
	"time"

	"github.com/fsnotify/fsnotify"
)

// ConfigWatcher 配置文件监控器
type ConfigWatcher struct {
	watcher    *fsnotify.Watcher
	configPath string
	stopCh     chan struct{}
}

// NewConfigWatcher 创建配置文件监控器
func NewConfigWatcher(configPath string) (*ConfigWatcher, error) {
	watcher, err := fsnotify.NewWatcher()
	if err != nil {
		return nil, err
	}

	// 转换为绝对路径
	absPath, err := filepath.Abs(configPath)
	if err != nil {
		return nil, err
	}

	return &ConfigWatcher{
		watcher:    watcher,
		configPath: absPath,
		stopCh:     make(chan struct{}),
	}, nil
}

// Start 启动配置文件监控
func (w *ConfigWatcher) Start() error {
	// 监控配置文件所在目录
	configDir := filepath.Dir(w.configPath)
	if err := w.watcher.Add(configDir); err != nil {
		return err
	}

	go w.watchLoop()
	return nil
}

// Stop 停止配置文件监控
func (w *ConfigWatcher) Stop() {
	close(w.stopCh)
	if w.watcher != nil {
		w.watcher.Close()
	}
	log.Println("配置文件监控已停止")
}

// watchLoop 监控循环
func (w *ConfigWatcher) watchLoop() {
	// 防抖动：在短时间内多次文件变化只处理一次
	var debounceTimer *time.Timer
	const debounceDelay = 500 * time.Millisecond

	for {
		select {
		case event, ok := <-w.watcher.Events:
			if !ok {
				return
			}

			// 只处理配置文件的写入或创建事件
			if filepath.Base(event.Name) == filepath.Base(w.configPath) {
				if event.Op&fsnotify.Write == fsnotify.Write || event.Op&fsnotify.Create == fsnotify.Create {
					// log.Printf("检测到配置文件变化: %s", event.Name)

					// 重置防抖动定时器
					if debounceTimer != nil {
						debounceTimer.Stop()
					}

					debounceTimer = time.AfterFunc(debounceDelay, func() {
						if err := ReloadConfig(); err != nil {
							log.Printf("重新加载配置失败: %v", err)
						} else {
							log.Println("✅ 配置热更新成功！")
						}
					})
				}
			}

		case err, ok := <-w.watcher.Errors:
			if !ok {
				return
			}
			log.Printf("配置文件监控错误: %v", err)

		case <-w.stopCh:
			if debounceTimer != nil {
				debounceTimer.Stop()
			}
			return
		}
	}
}

// StartConfigWatcher 启动配置文件监控（全局函数）
func StartConfigWatcher(configPath string) (*ConfigWatcher, error) {
	watcher, err := NewConfigWatcher(configPath)
	if err != nil {
		return nil, err
	}

	if err := watcher.Start(); err != nil {
		return nil, err
	}

	return watcher, nil
}