package filesys

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

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

	"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
	DirListingLimit    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
	handles           []*FileHandle
	pathToHandleIndex map[string]int
	pathToHandleLock  sync.Mutex
	bufPool           sync.Pool

	stats statsCache
}
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.DirListingLimit * 3).ItemsToPrune(100)),
		pathToHandleIndex:         make(map[string]int),
		bufPool: sync.Pool{
			New: func() interface{} {
				return make([]byte, option.ChunkSizeLimit)
			},
		},
	}

	return wfs
}

func (wfs *WFS) Root() (fs.Node, error) {
	return &Dir{Path: wfs.option.FilerMountRootPath, wfs: wfs}, 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) {
	wfs.pathToHandleLock.Lock()
	defer wfs.pathToHandleLock.Unlock()

	fullpath := file.fullpath()

	index, found := wfs.pathToHandleIndex[fullpath]
	if found && wfs.handles[index] != nil {
		glog.V(2).Infoln(fullpath, "found fileHandle id", index)
		return wfs.handles[index]
	}

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

	wfs.handles = append(wfs.handles, fileHandle)
	fileHandle.handle = uint64(len(wfs.handles) - 1)
	glog.V(2).Infoln(fullpath, "new fileHandle id", fileHandle.handle)
	wfs.pathToHandleIndex[fullpath] = int(fileHandle.handle)

	return
}

func (wfs *WFS) ReleaseHandle(fullpath string, handleId fuse.HandleID) {
	wfs.pathToHandleLock.Lock()
	defer wfs.pathToHandleLock.Unlock()

	glog.V(4).Infof("%s releasing handle id %d current handles length %d", fullpath, handleId, len(wfs.handles))
	delete(wfs.pathToHandleIndex, fullpath)
	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
}