package detector

import (
	"bufio"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"sysmonitord/internal/config"
	"sysmonitord/internal/scanner/hash"
	"sysmonitord/internal/storage"
	"sysmonitord/pkg/logger"
	"time"

	"go.uber.org/zap"
)

type FileDetector struct {
	cfg          *config.Config
	whiteList    map[string]string
	dubiousCache map[string]string
	storageDir   string
	mu           sync.RWMutex
	timer        map[string]*time.Timer
	debDuration  time.Duration
}

func NewFileDetector(cfg *config.Config) (*FileDetector, error) {
	d := &FileDetector{
		cfg:          cfg,
		storageDir:   cfg.Storage.DataDir,
		timer:        make(map[string]*time.Timer),
		debDuration:  1 * time.Second,
		dubiousCache: make(map[string]string),
	}

	if err := d.loadWhiteList(); err != nil {
		return nil, err
	}

	if err := d.loadDubiousCache(); err != nil {
		logger.Log.Warn("[monitor] 加载可疑文件缓存失败，使用空缓存...", zap.Error((err)))
	}

	return d, nil
}

func (d *FileDetector) loadDubiousCache() error {
	filePath := filepath.Join(d.storageDir, d.cfg.Storage.DubiousFileListFile)

	if _, err := os.Stat(filePath); os.IsNotExist(err) {
		return nil
	}

	file, err := os.Open(filePath)
	if err != nil {
		return err
	}
	defer file.Close()

	scanner := bufio.NewScanner(file)
	for scanner.Scan() {
		line := scanner.Text()
		if line == "" || strings.HasPrefix(line, "#") {
			continue
		}

		parts := strings.Split(line, ":")
		if len(parts) >= 2 {
			d.dubiousCache[parts[0]] = parts[1]
		}
	}

	logger.Log.Debug("[monitor] 可疑文件缓存加载成功", zap.Int("count", len(d.dubiousCache)))
	return scanner.Err()
}

func (d *FileDetector) loadWhiteList() error {
	whiteMap, err := storage.LoadFileSystemWhitelist(d.cfg.Storage.DataDir, d.cfg.Storage.FileSystemFile)
	if err != nil {
		logger.Log.Warn("[monitor] 加载文件白名单失败， 使用空白名单...", zap.Error((err)))
		d.whiteList = make(map[string]string)
		return nil
	}

	d.whiteList = whiteMap
	logger.Log.Info("[monitor] 文件白名单加载成功", zap.Int("count", len(d.whiteList)))
	return nil
}

func (d *FileDetector) HandleEvent(eventPath string, opStr string) {
	// Todo: 忽略临时文件等

	d.mu.Lock()
	defer d.mu.Unlock()

	if t, exists := d.timer[eventPath]; exists {
		t.Stop()
	}

	d.timer[eventPath] = time.AfterFunc(d.debDuration, func() {
		d.processEvent(eventPath)
		d.mu.Lock()
		delete(d.timer, eventPath)
		d.mu.Unlock()
	})
}

func (d *FileDetector) processEvent(eventPath string) {
	info, err := storage.GetFileInfo(eventPath)
	if err != nil {
		logger.Log.Warn("[monitor] 获取文件信息失败", zap.String("path", eventPath), zap.Error(err))
		return
	}

	if info.IsDir() {
		return
	}

	hashCfg, err := d.cfg.GetHashConfig()
	if err != nil {
		logger.Log.Warn("[monitor] 获取哈希配置失败", zap.Error(err))
		return
	}
	curHash, err := hash.Calculate(eventPath, info.Size(), hashCfg)
	if err != nil {
		logger.Log.Warn("[monitor] 计算文件哈希失败", zap.String("path", eventPath), zap.Error(err))
		return
	}

	d.mu.RLock()
	whiteHash, exist := d.whiteList[eventPath]
	d.mu.RUnlock()

	isSuspicious := false
	reason := ""

	if !exist {
		// 新文件
		isSuspicious = true
		reason = "新文件"
	} else if whiteHash != curHash {
		// 文件被修改
		isSuspicious = true
		reason = "文件被修改"
	}

	if isSuspicious {
		d.mu.Lock()

		cachedHash, exist := d.dubiousCache[eventPath]

		if !exist || cachedHash != curHash {
			d.dubiousCache[eventPath] = curHash

			d.mu.Unlock()

			logger.Log.Warn("[monitor] 可疑文件事件", zap.String("path", eventPath), zap.String("reason", reason), zap.String("hash", curHash))
			dubiousInfo := storage.DubiousFileInfo{
				Path:         eventPath,
				Hash:         curHash,
				DiscoveredAt: time.Now().Format("2006-01-02 15:04:05"),
			}
			if err := storage.SaveDubiousFiles(dubiousInfo, d.storageDir, d.cfg.Storage.DubiousFileListFile); err != nil {
				logger.Log.Error("[monitor] 保存可疑文件信息失败", zap.String("path", eventPath), zap.Error(err))
			}
		} else {
			d.mu.Unlock()
			logger.Log.Debug("[monitor] 文件事件已存在于可疑缓存中，忽略重复事件", zap.String("path", eventPath), zap.String("reason", reason), zap.String("hash", curHash))
		}
	}
}