package cache

import (
	"fmt"
	"io"
	"os"
	"path/filepath"
	"sync"
	"time"

	"gitlink.org.cn/cloudream/common/pkgs/logger"
	"gitlink.org.cn/cloudream/common/utils/io2"
	"gitlink.org.cn/cloudream/common/utils/lo2"
	"gitlink.org.cn/cloudream/common/utils/math2"
	"gitlink.org.cn/cloudream/common/utils/serder"
	"gitlink.org.cn/cloudream/jcs-pub/client/internal/mount/fuse"
	jcstypes "gitlink.org.cn/cloudream/jcs-pub/common/types"
)

type CacheLevel int

const (
	// 未加载
	LevelNotLoaded CacheLevel = iota
	// 缓存数据都完整，但仅加载了一次元数据，只能读取，不能修改。
	LevelReadOnly
	// 缓存数据都完整存在，但仅加载了元数据，没有加载文件数据
	LevelMetaLoaded
	// 缓存数据都完整存在，且已加载到内存中
	LevelComplete
)

func (l CacheLevel) String() string {
	var levels = []string{"NotLoaded", "ReadOnly", "MetaLoaded", "Complete"}
	return levels[l]
}

type FileInfo struct {
	// 文件总大小。可能会超过对应的远端文件的大小。
	// 此大小可能与本地缓存文件大小也不同，需要定时将本地缓存文件大小修正到与这个值相同。
	Size int64
	// 文件数据的版本号。如果大于0，则代表有未提交的修改
	DataRevision int
	// 文件元数据的版本号
	MetaRevision int
	// 数据段列表，按照段开始位置从小到大排列
	Segments []*Range
	// 文件对应的对象ID，仅在文件是一个缓存文件时才有值
	// ObjectID cdssdk.ObjectID
	// 文件对应的对象大小，仅在文件是一个缓存文件时才有值。
	// 此值代表有多少数据应该从远端加载，所以可能会小于远端实际大小
	ObjectSize int64
	// 如果本文件完全是一个缓存文件，那么这个字段记录了其内容的哈希值，用于在下载缓存数据时，检查远端文件是否被修改过
	// Hash cdssdk.FileHash
	// 文件的最后修改时间
	ModTime time.Time
	// 文件的权限
	Perm os.FileMode
}

func (f *FileInfo) Clone() FileInfo {
	n := *f
	n.Segments = make([]*Range, len(f.Segments))
	for i, seg := range f.Segments {
		n.Segments[i] = &Range{
			Position: seg.Position,
			Length:   seg.Length,
		}
	}

	return n
}

type Range struct {
	Position int64
	Length   int64
}

func (r *Range) GetPosition() int64 {
	return r.Position
}

func (r *Range) SetPosition(pos int64) {
	r.Position = pos
}

func (r *Range) GetLength() int64 {
	return r.Length
}

func (r *Range) SetLength(length int64) {
	r.Length = length
}

func (r *Range) End() int64 {
	return r.Position + r.Length
}

// 所有读写过程共用同一个CacheFile对象。
// 不应该将此结构体保存到对象中
type CacheFile struct {
	cache        *Cache
	pathComps    []string
	info         FileInfo
	remoteObj    *jcstypes.Object
	rwLock       *sync.RWMutex
	readers      []*CacheFileHandle
	writers      []*CacheFileHandle
	saveMetaChan chan any
	saveMetaLock *sync.Mutex
	stopSaveMeta *bool
	isDeleted    bool

	level           CacheLevel
	refCount        int
	freeTime        time.Time
	changeLevelTime time.Time

	metaFile  *os.File
	dataFile  *os.File
	writeLock *sync.RWMutex

	// 缓存文件的状态，用于管理缓存文件的生命周期。不受rwLock保护，而是由Cache管理
	state cacheState
}

type cacheState struct {
	uploading *uploadingObject
}

func createNewCacheFile(cache *Cache, pathComps []string) (*CacheFile, error) {
	metaPath := cache.GetCacheMetaPath(pathComps...)
	dataPath := cache.GetCacheDataPath(pathComps...)

	info := FileInfo{
		DataRevision: 1,
		ModTime:      time.Now(),
		Perm:         0755,
	}

	infoData, err := serder.ObjectToJSON(info)
	if err != nil {
		return nil, err
	}

	err = os.MkdirAll(filepath.Dir(metaPath), 0755)
	if err != nil {
		return nil, err
	}

	metaFile, err := os.OpenFile(metaPath, os.O_CREATE|os.O_RDWR|os.O_TRUNC, 0644)
	if err != nil {
		return nil, fmt.Errorf("create cache meta file: %w", err)
	}

	err = io2.WriteAll(metaFile, infoData)
	if err != nil {
		metaFile.Close()
		return nil, fmt.Errorf("save cache meta file: %w", err)
	}

	dataFile, err := os.OpenFile(dataPath, os.O_CREATE|os.O_RDWR|os.O_TRUNC, 0644)
	if err != nil {
		metaFile.Close()
		return nil, fmt.Errorf("create cache data file: %w", err)
	}

	ch := &CacheFile{
		cache:           cache,
		pathComps:       pathComps,
		info:            info,
		rwLock:          &sync.RWMutex{},
		saveMetaChan:    make(chan any, 1),
		saveMetaLock:    &sync.Mutex{},
		stopSaveMeta:    new(bool),
		level:           LevelComplete,
		freeTime:        time.Now(),
		changeLevelTime: time.Now(),
		metaFile:        metaFile,
		dataFile:        dataFile,
		writeLock:       &sync.RWMutex{},
		state:           cacheState{},
	}

	go ch.serving(ch.saveMetaChan, ch.stopSaveMeta)

	return ch, nil
}

func loadCacheFile(cache *Cache, pathComps []string) (*CacheFile, error) {
	metaPath := cache.GetCacheMetaPath(pathComps...)
	dataPath := cache.GetCacheDataPath(pathComps...)

	dataFile, err := os.OpenFile(dataPath, os.O_RDWR, 0644)
	if err != nil {
		// 不要包装这里的err
		return nil, err
	}

	info := &FileInfo{}

	metaFile, err := os.OpenFile(metaPath, os.O_RDWR, 0644)
	if err != nil {
		// 如果有数据文件，而没有元数据文件，则创建一个元数据文件
		if !os.IsNotExist(err) {
			dataFile.Close()
			return nil, err
		}

		stat, err := dataFile.Stat()
		if err != nil {
			dataFile.Close()
			return nil, err
		}

		err = os.MkdirAll(filepath.Dir(metaPath), 0755)
		if err != nil {
			dataFile.Close()
			return nil, err
		}

		metaFile, err = os.OpenFile(metaPath, os.O_CREATE|os.O_RDWR|os.O_TRUNC, 0644)
		if err != nil {
			dataFile.Close()
			return nil, err
		}

		info.Size = stat.Size()
		info.ModTime = stat.ModTime()
		info.Perm = stat.Mode().Perm()
		info.Segments = []*Range{{Position: 0, Length: info.Size}}
		info.MetaRevision = 1 // 未同步的文件视为已修改
		info.DataRevision = 1

	} else {
		err = serder.JSONToObjectStream(metaFile, info)
		if err != nil {
			dataFile.Close()
			return nil, err
		}
	}

	ch := &CacheFile{
		cache:           cache,
		pathComps:       pathComps,
		info:            *info,
		rwLock:          &sync.RWMutex{},
		saveMetaChan:    make(chan any, 1),
		saveMetaLock:    &sync.Mutex{},
		stopSaveMeta:    new(bool),
		level:           LevelComplete,
		freeTime:        time.Now(),
		changeLevelTime: time.Now(),
		metaFile:        metaFile,
		dataFile:        dataFile,
		writeLock:       &sync.RWMutex{},
		state:           cacheState{},
	}

	go ch.serving(ch.saveMetaChan, ch.stopSaveMeta)

	return ch, nil
}

func newCacheFileFromObject(cache *Cache, pathComps []string, obj *jcstypes.Object) (*CacheFile, error) {
	metaPath := cache.GetCacheMetaPath(pathComps...)
	dataPath := cache.GetCacheDataPath(pathComps...)

	info := FileInfo{
		Size:       obj.Size,
		ObjectSize: obj.Size,
		ModTime:    obj.UpdateTime,
		Perm:       0755,
	}

	infoData, err := serder.ObjectToJSON(info)
	if err != nil {
		return nil, err
	}

	err = os.MkdirAll(filepath.Dir(metaPath), 0755)
	if err != nil {
		return nil, err
	}

	metaFile, err := os.OpenFile(metaPath, os.O_CREATE|os.O_RDWR|os.O_TRUNC, 0644)
	if err != nil {
		return nil, fmt.Errorf("create cache meta file: %w", err)
	}

	err = io2.WriteAll(metaFile, infoData)
	if err != nil {
		metaFile.Close()
		return nil, fmt.Errorf("save cache meta file: %w", err)
	}

	dataFile, err := os.OpenFile(dataPath, os.O_CREATE|os.O_RDWR|os.O_TRUNC, 0644)
	if err != nil {
		metaFile.Close()
		return nil, fmt.Errorf("create cache file: %w", err)
	}

	ch := &CacheFile{
		cache:           cache,
		pathComps:       pathComps,
		info:            info,
		remoteObj:       obj,
		rwLock:          &sync.RWMutex{},
		saveMetaChan:    make(chan any, 1),
		saveMetaLock:    &sync.Mutex{},
		stopSaveMeta:    new(bool),
		level:           LevelComplete,
		freeTime:        time.Now(),
		changeLevelTime: time.Now(),
		metaFile:        metaFile,
		dataFile:        dataFile,
		writeLock:       &sync.RWMutex{},
		state:           cacheState{},
	}

	go ch.serving(ch.saveMetaChan, ch.stopSaveMeta)

	return ch, nil
}

func loadReadOnlyCacheFile(cache *Cache, pathComps []string) (*CacheFile, error) {
	metaPath := cache.GetCacheMetaPath(pathComps...)
	dataPath := cache.GetCacheDataPath(pathComps...)

	dataStat, err := os.Stat(dataPath)
	if err != nil {
		// 不要包装这里的err
		return nil, err
	}
	if dataStat.IsDir() {
		return nil, fmt.Errorf("target is a directory")
	}

	info := &FileInfo{}

	metaData, err := os.ReadFile(metaPath)
	if err != nil {
		if !os.IsNotExist(err) {
			return nil, err
		}

		err = os.MkdirAll(filepath.Dir(metaPath), 0755)
		if err != nil {
			return nil, err
		}

		info.Size = dataStat.Size()
		info.ModTime = dataStat.ModTime()
		info.Perm = dataStat.Mode().Perm()
		info.Segments = []*Range{{Position: 0, Length: info.Size}}
		info.MetaRevision = 1 // 未同步的文件视为已修改
		info.DataRevision = 1

		// 实际的元数据文件在LevelUp时才创建

	} else {
		err = serder.JSONToObject(metaData, info)
		if err != nil {
			return nil, err
		}
	}

	ch := &CacheFile{
		cache:           cache,
		pathComps:       pathComps,
		info:            *info,
		rwLock:          &sync.RWMutex{},
		saveMetaChan:    nil,
		saveMetaLock:    &sync.Mutex{},
		stopSaveMeta:    nil,
		level:           LevelReadOnly,
		freeTime:        time.Now(),
		changeLevelTime: time.Now(),
		metaFile:        nil,
		dataFile:        nil,
		writeLock:       &sync.RWMutex{},
		state:           cacheState{},
	}

	return ch, nil
}

func loadCacheFileInfo(cache *Cache, pathComps []string, dataFileInfo os.FileInfo) (*CacheEntryInfo, error) {
	metaPath := cache.GetCacheMetaPath(pathComps...)

	metaData, err := os.ReadFile(metaPath)
	if err == nil {
		info := &FileInfo{}
		err = serder.JSONToObject(metaData, info)
		if err != nil {
			return nil, err
		}

		return &CacheEntryInfo{
			PathComps: pathComps,
			Size:      info.Size,
			Perm:      info.Perm,
			ModTime:   info.ModTime,
			IsDir:     false,
		}, nil
	}

	if !os.IsNotExist(err) {
		return nil, err
	}

	return &CacheEntryInfo{
		PathComps: pathComps,
		Size:      dataFileInfo.Size(),
		Perm:      dataFileInfo.Mode(),
		ModTime:   dataFileInfo.ModTime(),
		IsDir:     false,
	}, nil
}

// 增加一个引用计数。不应该被Cache之外的代码调用。
func (f *CacheFile) IncRef() {
	f.rwLock.Lock()
	defer f.rwLock.Unlock()

	f.refCount++
}

// 减少一个引用计数
func (f *CacheFile) Release() {
	f.rwLock.Lock()
	defer f.rwLock.Unlock()

	f.refCount--
	if f.refCount == 0 {
		f.freeTime = time.Now()
	}
}

func (f *CacheFile) LevelDown(level CacheLevel) bool {
	if level <= LevelReadOnly {
		// 如果降级到不需要保存元数据的级别，就要先暂停保存元数据的操作
		f.saveMetaLock.Lock()
		defer f.saveMetaLock.Unlock()
	}

	f.rwLock.Lock()
	defer f.rwLock.Unlock()

	if level >= f.level {
		return true
	}

	// 缓存正在被使用时，不能降级
	if f.refCount > 0 {
		return false
	}

	switch f.level {
	case LevelComplete:
		f.dataFile.Close()

		f.level = LevelMetaLoaded
		if level >= f.level {
			break
		}
		fallthrough

	case LevelMetaLoaded:
		if !f.isDeleted {
			// TODO 日志
			f.saveMeta(f.info)
		}
		f.saveMetaChan = nil
		// 由于已经获取了saveMetaLock，所以这里设置true之后调用metaFile.Close不会导致saveMeta线程的保存失败
		// 因为saveMeta线程会先检查stopSaveMete的值
		*f.stopSaveMeta = true
		f.stopSaveMeta = nil
		f.metaFile.Close()

		f.level = LevelReadOnly
		if level >= f.level {
			break
		}
		fallthrough

	case LevelReadOnly:
		f.level = LevelNotLoaded
		if level >= f.level {
			break
		}
		fallthrough

	case LevelNotLoaded:
	}

	f.changeLevelTime = time.Now()

	return true
}

func (f *CacheFile) LevelUp(level CacheLevel) bool {
	f.rwLock.Lock()
	defer f.rwLock.Unlock()

	if level <= f.level {
		return true
	}

	// 缓存正在使用时，可以升级

	switch f.level {
	case LevelNotLoaded:
		f.level = LevelReadOnly
		if level <= f.level {
			break
		}
		fallthrough

	case LevelReadOnly:
		metaPath := f.cache.GetCacheMetaPath(f.pathComps...)
		metaFile, err := os.OpenFile(metaPath, os.O_RDWR|os.O_CREATE, 0644)
		if err != nil {
			logger.Warnf("open meta file %v: %v", metaPath, err)
			return false
		}

		f.saveMetaChan = make(chan any, 1)
		f.stopSaveMeta = new(bool)
		f.metaFile = metaFile
		f.level = LevelMetaLoaded

		go f.serving(f.saveMetaChan, f.stopSaveMeta)

		if level <= f.level {
			break
		}
		fallthrough

	case LevelMetaLoaded:
		dataPath := f.cache.GetCacheDataPath(f.pathComps...)
		dataFile, err := os.OpenFile(dataPath, os.O_RDWR|os.O_CREATE, 0644)
		if err != nil {
			logger.Warnf("open data file %v: %v", dataPath, err)
			return false
		}

		f.dataFile = dataFile
		f.level = LevelComplete

		if level <= f.level {
			break
		}
		fallthrough

	case LevelComplete:
	}

	f.changeLevelTime = time.Now()

	return true
}

func (f *CacheFile) RevisionUploaded(dataRev int, metaRev int) {
	f.rwLock.Lock()
	defer f.rwLock.Unlock()

	if dataRev != 0 && f.info.DataRevision == dataRev {
		f.info.DataRevision = 0
	}

	if metaRev != 0 && f.info.MetaRevision == metaRev {
		f.info.MetaRevision = 0
	}

	f.letSave()
}

func (f *CacheFile) Info() CacheEntryInfo {
	f.rwLock.RLock()
	defer f.rwLock.RUnlock()

	return CacheEntryInfo{
		PathComps:       f.pathComps,
		Size:            f.info.Size,
		Perm:            f.info.Perm,
		ModTime:         f.info.ModTime,
		IsDir:           false,
		MetaRevision:    f.info.MetaRevision,
		DataRevision:    f.info.DataRevision,
		RefCount:        f.refCount,
		FreeTime:        f.freeTime,
		Level:           f.level,
		ChangeLevelTime: f.changeLevelTime,
	}
}

func (f *CacheFile) Delete() {
	f.writeLock.Lock()
	defer f.writeLock.Unlock()

	f.rwLock.Lock()
	defer f.rwLock.Unlock()

	metaPath := f.cache.GetCacheMetaPath(f.pathComps...)
	dataPath := f.cache.GetCacheDataPath(f.pathComps...)
	os.Remove(metaPath)
	os.Remove(dataPath)

	// 不可能将isDeleted从true改为false，所以这里不需要使用stopSaveChan来等待saveMeta线程退出
	f.isDeleted = true

	if f.saveMetaChan != nil {
		f.letSave()
	}
}

func (f *CacheFile) Move(newPathComps []string) {
	f.writeLock.Lock()
	defer f.writeLock.Unlock()

	f.rwLock.Lock()
	defer f.rwLock.Unlock()

	f.pathComps = newPathComps

	if f.saveMetaChan != nil {
		f.letSave()
	}
}

// 打开一个写入句柄，同时支持读取
func (f *CacheFile) Open(flags uint32) *CacheFileHandle {
	logger.Tracef("CacheFile.Open: %v, %#x", f.pathComps, flags)

	f.rwLock.Lock()
	defer f.rwLock.Unlock()

	f.refCount++

	h := &CacheFileHandle{
		file:       f,
		remoteLock: &sync.Mutex{},
		revision:   f.info.DataRevision,
	}

	if flags&uint32(os.O_RDWR) == uint32(os.O_RDWR) {
		h.readable = true
		h.writeable = true
	} else if flags&uint32(os.O_WRONLY) == uint32(os.O_WRONLY) {
		h.writeable = true
	} else if flags&uint32(os.O_RDONLY) == uint32(os.O_RDONLY) {
		h.readable = true
	}

	if f.remoteObj != nil {
		h.remote = newRemoteLoader(f)
	}

	if h.writeable {
		f.writers = append(f.writers, h)
	} else {
		f.readers = append(f.readers, h)
	}

	return h
}

// 打开一个读取句柄，用于同步本地文件到远端
func (f *CacheFile) OpenReadWhenScanning() *CacheFileHandle {
	f.rwLock.Lock()
	defer f.rwLock.Unlock()

	f.refCount++

	h := &CacheFileHandle{
		file:       f,
		remoteLock: &sync.Mutex{},
		revision:   f.info.DataRevision,
		readable:   true,
	}

	if f.remoteObj != nil {
		h.remote = newRemoteLoader(f)
	}

	f.readers = append(f.readers, h)
	return h
}

func (f *CacheFile) SetModTime(modTime time.Time) error {
	logger.Tracef("CacheFile.SetModTime: %v, %v", f.pathComps, modTime)

	f.rwLock.Lock()
	f.info.ModTime = modTime
	f.info.MetaRevision++
	f.rwLock.Unlock()

	f.letSave()
	return nil
}

func (f *CacheFile) Truncate(size int64) error {
	logger.Tracef("CacheFile.Truncate: %v, %v", f.pathComps, size)

	// 修改文件大小前不允许写入
	f.writeLock.Lock()
	defer f.writeLock.Unlock()

	err := f.dataFile.Truncate(size)
	if err != nil {
		return err
	}

	f.rwLock.Lock()
	defer f.rwLock.Unlock()

	// 调整能从远端下载的大小
	f.info.ObjectSize = math2.Min(f.info.ObjectSize, size)

	// 调整本地缓存文件里的有效数据大小
	if size < f.info.Size {
		f.info.Segments = TruncateRange(f.info.Segments, size)
	} else if size > f.info.Size {
		f.info.Segments = AddRange(f.info.Segments, &Range{Position: f.info.Size, Length: size - f.info.Size})
	}
	if f.info.Size != size {
		f.info.DataRevision++
	}
	f.info.Size = size

	f.letSave()
	return nil
}

func (f *CacheFile) serving(saveMetaChan chan any, stopSaveMeta *bool) {
	ticker := time.NewTicker(time.Second * 30)
	defer ticker.Stop()

	for {
		select {
		case _, ok := <-saveMetaChan:
			if !ok {
				return
			}

		case <-ticker.C:
		}

		f.saveMetaLock.Lock()
		if *stopSaveMeta {
			f.saveMetaLock.Unlock()
			break
		}

		f.rwLock.RLock()
		info := f.info.Clone()
		// 如果文件已被删除，则不能再保存元数据，防止覆盖掉新创建的同名文件
		if f.isDeleted {
			f.rwLock.RUnlock()
			f.saveMetaLock.Unlock()
			break
		}

		f.rwLock.RUnlock()

		// TODO 错误日志
		f.saveMeta(info)
		f.metaFile.Sync()
		f.saveMetaLock.Unlock()
	}
}

func (f *CacheFile) saveMeta(info FileInfo) error {
	jsonData, err := serder.ObjectToJSON(info)
	if err != nil {
		return err
	}

	err = f.metaFile.Truncate(0)
	if err != nil {
		return err
	}

	_, err = f.metaFile.Seek(0, io.SeekStart)
	if err != nil {
		return err
	}

	err = io2.WriteAll(f.metaFile, jsonData)
	if err != nil {
		return err
	}

	return nil
}

func (f *CacheFile) letSave() {
	select {
	case f.saveMetaChan <- nil:
	default:
	}
}

type CacheFileHandle struct {
	file       *CacheFile
	readable   bool
	writeable  bool
	remote     *RemoteLoader
	remoteLock *sync.Mutex
	revision   int // 打开文件时，文件的版本号
}

func (h *CacheFileHandle) ReadAt(buf []byte, off int64) (int, error) {
	log := logger.WithField("F", "CacheFileHandle.ReadAt").
		WithField("Path", h.file.pathComps)
	log.Tracef("buf: %v, off: %v", len(buf), off)

	if !h.readable {
		return 0, fuse.ErrPermission
	}

	// 读取数据必须读满整个buf，否则就会被认为是文件已经结束了
	totalReadLen := 0
	for totalReadLen < len(buf) {
		curBuf := buf[totalReadLen:]
		curOff := off + int64(totalReadLen)

		h.file.rwLock.RLock()

		if curOff >= h.file.info.Size {
			h.file.rwLock.RUnlock()
			break
		}

		/// 1. 先尝试从本地缓存文件里读取
		rngIdx := FirstContainsIndex(h.file.info.Segments, curOff)
		if rngIdx >= 0 && h.file.info.Segments[rngIdx].End() > curOff {
			readLen := math2.Min(int64(len(curBuf)), h.file.info.Segments[rngIdx].End()-curOff)
			realReadLen, err := h.file.dataFile.ReadAt(curBuf[:readLen], curOff)
			totalReadLen += realReadLen
			h.file.rwLock.RUnlock()

			if err != nil {
				log.Tracef("read from local cache: %v", err)
				return totalReadLen, err
			}
			continue
		}

		// 否则从远端下载，计算一下要加载的长度
		loadLen := math2.Min(int64(len(curBuf)), h.file.info.ObjectSize-curOff)
		if rngIdx+1 < len(h.file.info.Segments) {
			// 最多加载到下一个段的开头
			loadLen = math2.Min(loadLen, h.file.info.Segments[rngIdx+1].Position-curOff)
		}

		h.file.rwLock.RUnlock()

		/// 2. 开始从远端下载数据

		if h.remote == nil {
			log.Warnf("no remote file")
			return totalReadLen, fmt.Errorf("no remote file")
		}

		// 由于RemoteLoader的Load方法没有加锁，所以这里要加锁，防止并发Seek导致的问题
		// 可以考虑在RemoteLoader里加锁，这样可以实现跨Writer共用Loader
		h.remoteLock.Lock()
		realLoadLen, err := h.remote.Load(curBuf[:loadLen], curOff)
		totalReadLen += realLoadLen
		if err != nil {
			h.remoteLock.Unlock()
			return totalReadLen, err
		}
		h.remoteLock.Unlock()
		log.Tracef("load from remote: %v", realLoadLen)

		/// 3. 数据加载完毕，写入到本地文件

		// 在写入到本地之前，先停止其他的写入，防止冲突
		h.file.writeLock.Lock()

		// 停止其他写入后，就可以计算一下实际要写回的长度。
		h.file.rwLock.RLock()
		loadRng := &Range{Position: curOff, Length: int64(realLoadLen)}
		DifferentRange(loadRng, h.file.info.Segments)
		h.file.rwLock.RUnlock()

		if loadRng.Length == 0 {
			h.file.writeLock.Unlock()
			continue
		}

		// 写入到本地缓存文件
		writeStart := loadRng.Position - curOff
		_, err = h.file.dataFile.WriteAt(curBuf[writeStart:writeStart+loadRng.Length], curOff)
		if err != nil {
			h.file.writeLock.Unlock()

			log.Warnf("save to local file: %v", err)
			return totalReadLen, err
		}

		log.Tracef("save to local: %v", loadRng.Length)

		h.file.writeLock.Unlock()

		// 提交到段列表里
		h.file.rwLock.Lock()
		h.file.info.Segments = AddRange(h.file.info.Segments, loadRng)
		h.file.rwLock.Unlock()
		h.file.letSave()
	}

	return totalReadLen, nil
}

func (h *CacheFileHandle) WriteAt(buf []byte, off int64) (int, error) {
	log := logger.WithField("F", "CacheFileHandle.WriteAt").WithField("Path", h.file.pathComps)
	log.Tracef("buf: %v, off: %v", len(buf), off)

	if !h.writeable {
		return 0, fuse.ErrPermission
	}

	// 允许多线程并行写入，但在数据加载期间不能写入
	h.file.writeLock.RLock()
	defer h.file.writeLock.RUnlock()

	// 写入到本地缓存文件
	writeLen, err := h.file.dataFile.WriteAt(buf, off)
	if err != nil {
		log.Tracef("save to local file: %v", err)
		return writeLen, err
	}

	// 提交到段列表里
	h.file.rwLock.Lock()
	defer h.file.rwLock.Unlock()

	h.file.info.Segments = AddRange(h.file.info.Segments, &Range{Position: off, Length: int64(writeLen)})
	h.file.info.Size = math2.Max(h.file.info.Size, off+int64(writeLen))
	h.file.info.DataRevision++

	h.file.letSave()

	return writeLen, nil
}

func (f *CacheFileHandle) Sync() error {
	log := logger.WithField("Path", f.file.pathComps)

	err := f.file.dataFile.Sync()
	if err != nil {
		log.Tracef("sync local file: %v", err)
		return err
	}

	return nil
}

func (f *CacheFileHandle) Close() error {
	f.Sync()

	if f.remote != nil {
		f.remote.Close()
	}

	f.file.rwLock.Lock()
	defer f.file.rwLock.Unlock()

	f.file.refCount--
	if f.file.refCount == 0 {
		f.file.freeTime = time.Now()
	}

	if f.writeable {
		f.file.writers = lo2.Remove(f.file.writers, f)
	} else if f.readable {
		f.file.readers = lo2.Remove(f.file.readers, f)
	}
	return nil
}