package mount

import (
	"context"
	"errors"
	"math/rand"
	"os"
	"path"
	"path/filepath"
	"sync/atomic"
	"time"

	"github.com/hanwen/go-fuse/v2/fuse"
	"google.golang.org/grpc"

	"github.com/seaweedfs/seaweedfs/weed/filer"
	"github.com/seaweedfs/seaweedfs/weed/mount/meta_cache"
	"github.com/seaweedfs/seaweedfs/weed/pb"
	"github.com/seaweedfs/seaweedfs/weed/pb/filer_pb"
	"github.com/seaweedfs/seaweedfs/weed/pb/mount_pb"
	"github.com/seaweedfs/seaweedfs/weed/storage/types"
	"github.com/seaweedfs/seaweedfs/weed/util"
	"github.com/seaweedfs/seaweedfs/weed/util/chunk_cache"
	"github.com/seaweedfs/seaweedfs/weed/util/grace"
	"github.com/seaweedfs/seaweedfs/weed/wdclient"

	"github.com/hanwen/go-fuse/v2/fs"
)

type Option struct {
	filerIndex         int32 // align memory for atomic read/write
	FilerAddresses     []pb.ServerAddress
	MountDirectory     string
	GrpcDialOption     grpc.DialOption
	FilerMountRootPath string
	Collection         string
	Replication        string
	TtlSec             int32
	DiskType           types.DiskType
	ChunkSizeLimit     int64
	ConcurrentWriters  int
	CacheDirForRead    string
	CacheSizeMBForRead int64
	CacheDirForWrite   string
	DataCenter         string
	Umask              os.FileMode
	Quota              int64
	DisableXAttr       bool

	MountUid         uint32
	MountGid         uint32
	MountMode        os.FileMode
	MountCtime       time.Time
	MountMtime       time.Time
	MountParentInode uint64

	VolumeServerAccess string // how to access volume servers
	Cipher             bool   // whether encrypt data on volume server
	UidGidMapper       *meta_cache.UidGidMapper

	uniqueCacheDirForRead  string
	uniqueCacheDirForWrite string
}

type WFS struct {
	// https://dl.acm.org/doi/fullHtml/10.1145/3310148
	// follow https://github.com/hanwen/go-fuse/blob/master/fuse/api.go
	fuse.RawFileSystem
	mount_pb.UnimplementedSeaweedMountServer
	fs.Inode
	option            *Option
	metaCache         *meta_cache.MetaCache
	stats             statsCache
	chunkCache        *chunk_cache.TieredChunkCache
	signature         int32
	concurrentWriters *util.LimitedConcurrentExecutor
	inodeToPath       *InodeToPath
	fhMap             *FileHandleToInode
	dhMap             *DirectoryHandleToInode
	fuseServer        *fuse.Server
	IsOverQuota       bool
	fhLockTable       *util.LockTable[FileHandleId]
	FilerConf         *filer.FilerConf
}

func NewSeaweedFileSystem(option *Option) *WFS {
	wfs := &WFS{
		RawFileSystem: fuse.NewDefaultRawFileSystem(),
		option:        option,
		signature:     util.RandomInt32(),
		inodeToPath:   NewInodeToPath(util.FullPath(option.FilerMountRootPath)),
		fhMap:         NewFileHandleToInode(),
		dhMap:         NewDirectoryHandleToInode(),
		fhLockTable:   util.NewLockTable[FileHandleId](),
	}

	wfs.option.filerIndex = int32(rand.Intn(len(option.FilerAddresses)))
	wfs.option.setupUniqueCacheDirectory()
	if option.CacheSizeMBForRead > 0 {
		wfs.chunkCache = chunk_cache.NewTieredChunkCache(256, option.getUniqueCacheDirForRead(), option.CacheSizeMBForRead, 1024*1024)
	}

	wfs.metaCache = meta_cache.NewMetaCache(path.Join(option.getUniqueCacheDirForRead(), "meta"), option.UidGidMapper,
		util.FullPath(option.FilerMountRootPath),
		func(path util.FullPath) {
			wfs.inodeToPath.MarkChildrenCached(path)
		}, func(path util.FullPath) bool {
			return wfs.inodeToPath.IsChildrenCached(path)
		}, func(filePath util.FullPath, entry *filer_pb.Entry) {
			// Find inode if it is not a deleted path
			if inode, inodeFound := wfs.inodeToPath.GetInode(filePath); inodeFound {
				// Find open file handle
				if fh, fhFound := wfs.fhMap.FindFileHandle(inode); fhFound {
					fhActiveLock := fh.wfs.fhLockTable.AcquireLock("invalidateFunc", fh.fh, util.ExclusiveLock)
					defer fh.wfs.fhLockTable.ReleaseLock(fh.fh, fhActiveLock)

					// Recreate dirty pages
					fh.dirtyPages.Destroy()
					fh.dirtyPages = newPageWriter(fh, wfs.option.ChunkSizeLimit)

					// Update handle entry
					newEntry, status := wfs.maybeLoadEntry(filePath)
					if status == fuse.OK {
						if fh.GetEntry().GetEntry() != newEntry {
							fh.SetEntry(newEntry)
						}
					}
				}
			}
		})
	grace.OnInterrupt(func() {
		wfs.metaCache.Shutdown()
		os.RemoveAll(option.getUniqueCacheDirForWrite())
		os.RemoveAll(option.getUniqueCacheDirForRead())
	})

	if wfs.option.ConcurrentWriters > 0 {
		wfs.concurrentWriters = util.NewLimitedConcurrentExecutor(wfs.option.ConcurrentWriters)
	}
	return wfs
}

func (wfs *WFS) StartBackgroundTasks() error {
	follower, err := wfs.subscribeFilerConfEvents()
	if err != nil {
		return err
	}

	startTime := time.Now()
	go meta_cache.SubscribeMetaEvents(wfs.metaCache, wfs.signature, wfs, wfs.option.FilerMountRootPath, startTime.UnixNano(), follower)
	go wfs.loopCheckQuota()

	return nil
}

func (wfs *WFS) String() string {
	return "seaweedfs"
}

func (wfs *WFS) Init(server *fuse.Server) {
	wfs.fuseServer = server
}

func (wfs *WFS) maybeReadEntry(inode uint64) (path util.FullPath, fh *FileHandle, entry *filer_pb.Entry, status fuse.Status) {
	path, status = wfs.inodeToPath.GetPath(inode)
	if status != fuse.OK {
		return
	}
	var found bool
	if fh, found = wfs.fhMap.FindFileHandle(inode); found {
		entry = fh.UpdateEntry(func(entry *filer_pb.Entry) {
			if entry != nil && fh.entry.Attributes == nil {
				entry.Attributes = &filer_pb.FuseAttributes{}
			}
		})
	} else {
		entry, status = wfs.maybeLoadEntry(path)
	}
	return
}

func (wfs *WFS) maybeLoadEntry(fullpath util.FullPath) (*filer_pb.Entry, fuse.Status) {

	// glog.V(3).Infof("read entry cache miss %s", fullpath)
	dir, name := fullpath.DirAndName()

	// return a valid entry for the mount root
	if string(fullpath) == wfs.option.FilerMountRootPath {
		return &filer_pb.Entry{
			Name:        name,
			IsDirectory: true,
			Attributes: &filer_pb.FuseAttributes{
				Mtime:    wfs.option.MountMtime.Unix(),
				FileMode: uint32(wfs.option.MountMode),
				Uid:      wfs.option.MountUid,
				Gid:      wfs.option.MountGid,
				Crtime:   wfs.option.MountCtime.Unix(),
			},
		}, fuse.OK
	}

	// read from async meta cache
	meta_cache.EnsureVisited(wfs.metaCache, wfs, util.FullPath(dir))
	cachedEntry, cacheErr := wfs.metaCache.FindEntry(context.Background(), fullpath)
	if errors.Is(cacheErr, filer_pb.ErrNotFound) {
		return nil, fuse.ENOENT
	}
	return cachedEntry.ToProtoEntry(), fuse.OK
}

func (wfs *WFS) LookupFn() wdclient.LookupFileIdFunctionType {
	if wfs.option.VolumeServerAccess == "filerProxy" {
		return func(fileId string) (targetUrls []string, err error) {
			return []string{"http://" + wfs.getCurrentFiler().ToHttpAddress() + "/?proxyChunkId=" + fileId}, nil
		}
	}
	return filer.LookupFn(wfs)
}

func (wfs *WFS) getCurrentFiler() pb.ServerAddress {
	i := atomic.LoadInt32(&wfs.option.filerIndex)
	return wfs.option.FilerAddresses[i]
}

func (option *Option) setupUniqueCacheDirectory() {
	cacheUniqueId := util.Md5String([]byte(option.MountDirectory + string(option.FilerAddresses[0]) + option.FilerMountRootPath + util.Version()))[0:8]
	option.uniqueCacheDirForRead = path.Join(option.CacheDirForRead, cacheUniqueId)
	os.MkdirAll(option.uniqueCacheDirForRead, os.FileMode(0777)&^option.Umask)
	option.uniqueCacheDirForWrite = filepath.Join(path.Join(option.CacheDirForWrite, cacheUniqueId), "swap")
	os.MkdirAll(option.uniqueCacheDirForWrite, os.FileMode(0777)&^option.Umask)
}

func (option *Option) getUniqueCacheDirForWrite() string {
	return option.uniqueCacheDirForWrite
}

func (option *Option) getUniqueCacheDirForRead() string {
	return option.uniqueCacheDirForRead
}