package filesys

import (
	"context"
	"fmt"
	"math"
	"os"
	"sync"
	"time"

	"github.com/karlseguin/ccache"
	"google.golang.org/grpc"

	"github.com/chrislusf/seaweedfs/weed/filer2"
	"github.com/chrislusf/seaweedfs/weed/glog"
	"github.com/chrislusf/seaweedfs/weed/pb/filer_pb"
	"github.com/chrislusf/seaweedfs/weed/util"
	"github.com/seaweedfs/fuse"
	"github.com/seaweedfs/fuse/fs"
)

type Option struct {
	FilerGrpcAddress   string
	GrpcDialOption     grpc.DialOption
	FilerMountRootPath string
	Collection         string
	Replication        string
	TtlSec             int32
	ChunkSizeLimit     int64
	DataCenter         string
	DirListCacheLimit  int64
	EntryCacheTtl      time.Duration
	Umask              os.FileMode

	MountUid   uint32
	MountGid   uint32
	MountMode  os.FileMode
	MountCtime time.Time
	MountMtime time.Time
}

var _ = fs.FS(&WFS{})
var _ = fs.FSStatfser(&WFS{})

type WFS struct {
	option                    *Option
	listDirectoryEntriesCache *ccache.Cache

	// contains all open handles, protected by handlesLock
	handlesLock sync.Mutex
	handles     []*FileHandle

	bufPool sync.Pool

	stats statsCache

	// nodes, protected by nodesLock
	nodesLock sync.Mutex
	nodes     map[uint64]fs.Node
	root      fs.Node
}
type statsCache struct {
	filer_pb.StatisticsResponse
	lastChecked int64 // unix time in seconds
}

func NewSeaweedFileSystem(option *Option) *WFS {
	wfs := &WFS{
		option:                    option,
		listDirectoryEntriesCache: ccache.New(ccache.Configure().MaxSize(option.DirListCacheLimit * 3).ItemsToPrune(100)),
		bufPool: sync.Pool{
			New: func() interface{} {
				return make([]byte, option.ChunkSizeLimit)
			},
		},
		nodes: make(map[uint64]fs.Node),
	}

	wfs.root = &Dir{Path: wfs.option.FilerMountRootPath, wfs: wfs}

	return wfs
}

func (wfs *WFS) Root() (fs.Node, error) {
	return wfs.root, nil
}

func (wfs *WFS) WithFilerClient(ctx context.Context, fn func(filer_pb.SeaweedFilerClient) error) error {

	return util.WithCachedGrpcClient(ctx, func(grpcConnection *grpc.ClientConn) error {
		client := filer_pb.NewSeaweedFilerClient(grpcConnection)
		return fn(client)
	}, wfs.option.FilerGrpcAddress, wfs.option.GrpcDialOption)

}

func (wfs *WFS) AcquireHandle(file *File, uid, gid uint32) (fileHandle *FileHandle) {

	fullpath := file.fullpath()
	glog.V(4).Infof("%s AcquireHandle uid=%d gid=%d", fullpath, uid, gid)

	wfs.handlesLock.Lock()
	defer wfs.handlesLock.Unlock()

	fileHandle = newFileHandle(file, uid, gid)
	for i, h := range wfs.handles {
		if h == nil {
			wfs.handles[i] = fileHandle
			fileHandle.handle = uint64(i)
			glog.V(4).Infof( "%s reuse fh %d", fullpath,fileHandle.handle)
			return
		}
	}

	wfs.handles = append(wfs.handles, fileHandle)
	fileHandle.handle = uint64(len(wfs.handles) - 1)
	glog.V(4).Infof( "%s new fh %d", fullpath,fileHandle.handle)

	return
}

func (wfs *WFS) ReleaseHandle(fullpath filer2.FullPath, handleId fuse.HandleID) {
	wfs.handlesLock.Lock()
	defer wfs.handlesLock.Unlock()

	glog.V(4).Infof("%s ReleaseHandle id %d current handles length %d", fullpath, handleId, len(wfs.handles))
	if int(handleId) < len(wfs.handles) {
		wfs.handles[int(handleId)] = nil
	}

	return
}

// Statfs is called to obtain file system metadata. Implements fuse.FSStatfser
func (wfs *WFS) Statfs(ctx context.Context, req *fuse.StatfsRequest, resp *fuse.StatfsResponse) error {

	glog.V(4).Infof("reading fs stats: %+v", req)

	if wfs.stats.lastChecked < time.Now().Unix()-20 {

		err := wfs.WithFilerClient(ctx, func(client filer_pb.SeaweedFilerClient) error {

			request := &filer_pb.StatisticsRequest{
				Collection:  wfs.option.Collection,
				Replication: wfs.option.Replication,
				Ttl:         fmt.Sprintf("%ds", wfs.option.TtlSec),
			}

			glog.V(4).Infof("reading filer stats: %+v", request)
			resp, err := client.Statistics(ctx, request)
			if err != nil {
				glog.V(0).Infof("reading filer stats %v: %v", request, err)
				return err
			}
			glog.V(4).Infof("read filer stats: %+v", resp)

			wfs.stats.TotalSize = resp.TotalSize
			wfs.stats.UsedSize = resp.UsedSize
			wfs.stats.FileCount = resp.FileCount
			wfs.stats.lastChecked = time.Now().Unix()

			return nil
		})
		if err != nil {
			glog.V(0).Infof("filer Statistics: %v", err)
			return err
		}
	}

	totalDiskSize := wfs.stats.TotalSize
	usedDiskSize := wfs.stats.UsedSize
	actualFileCount := wfs.stats.FileCount

	// Compute the total number of available blocks
	resp.Blocks = totalDiskSize / blockSize

	// Compute the number of used blocks
	numBlocks := uint64(usedDiskSize / blockSize)

	// Report the number of free and available blocks for the block size
	resp.Bfree = resp.Blocks - numBlocks
	resp.Bavail = resp.Blocks - numBlocks
	resp.Bsize = uint32(blockSize)

	// Report the total number of possible files in the file system (and those free)
	resp.Files = math.MaxInt64
	resp.Ffree = math.MaxInt64 - actualFileCount

	// Report the maximum length of a name and the minimum fragment size
	resp.Namelen = 1024
	resp.Frsize = uint32(blockSize)

	return nil
}

func (wfs *WFS) cacheGet(path filer2.FullPath) *filer_pb.Entry {
	item := wfs.listDirectoryEntriesCache.Get(string(path))
	if item != nil && !item.Expired() {
		return item.Value().(*filer_pb.Entry)
	}
	return nil
}
func (wfs *WFS) cacheSet(path filer2.FullPath, entry *filer_pb.Entry, ttl time.Duration) {
	if entry == nil {
		wfs.listDirectoryEntriesCache.Delete(string(path))
	} else {
		wfs.listDirectoryEntriesCache.Set(string(path), entry, ttl)
	}
}
func (wfs *WFS) cacheDelete(path filer2.FullPath) {
	wfs.listDirectoryEntriesCache.Delete(string(path))
}

func (wfs *WFS) getNode(fullpath filer2.FullPath, fn func() fs.Node) fs.Node {
	wfs.nodesLock.Lock()
	defer wfs.nodesLock.Unlock()

	node, found := wfs.nodes[fullpath.AsInode()]
	if found {
		return node
	}
	node = fn()
	if node != nil {
		wfs.nodes[fullpath.AsInode()] = node
	}
	return node
}

func (wfs *WFS) forgetNode(fullpath filer2.FullPath) {
	wfs.nodesLock.Lock()
	defer wfs.nodesLock.Unlock()

	delete(wfs.nodes, fullpath.AsInode())

}