// +build cgo
// +build linux darwin freebsd windows

package cmount

import (
	"os"
	"path"
	"runtime"
	"sync"
	"time"

	"github.com/billziss-gh/cgofuse/fuse"
	"github.com/ncw/rclone/cmd/mountlib"
	"github.com/ncw/rclone/fs"
	"github.com/pkg/errors"
)

const fhUnset = ^uint64(0)

// FS represents the top level filing system
type FS struct {
	FS          *mountlib.FS
	f           fs.Fs
	openDirs    *openFiles
	openFilesWr *openFiles
	openFilesRd *openFiles
	ready       chan (struct{})
}

// NewFS makes a new FS
func NewFS(f fs.Fs) *FS {
	fsys := &FS{
		FS:          mountlib.NewFS(f),
		f:           f,
		openDirs:    newOpenFiles(0x01),
		openFilesWr: newOpenFiles(0x02),
		openFilesRd: newOpenFiles(0x03),
		ready:       make(chan (struct{})),
	}
	if noSeek {
		fsys.FS.NoSeek()
	}
	if noChecksum {
		fsys.FS.NoChecksum()
	}
	return fsys
}

type openFiles struct {
	mu    sync.Mutex
	mark  uint8
	nodes []mountlib.Noder
}

func newOpenFiles(mark uint8) *openFiles {
	return &openFiles{
		mark: mark,
	}
}

// Open a node returning a file handle
func (of *openFiles) Open(node mountlib.Noder) (fh uint64) {
	of.mu.Lock()
	defer of.mu.Unlock()
	var i int
	var oldNode mountlib.Noder
	for i, oldNode = range of.nodes {
		if oldNode == nil {
			of.nodes[i] = node
			goto found
		}
	}
	of.nodes = append(of.nodes, node)
	i = len(of.nodes) - 1
found:
	return uint64((i << 8) | int(of.mark))
}

// InRange to see if this fh could be one of ours
func (of *openFiles) InRange(fh uint64) bool {
	return uint8(fh) == of.mark
}

// get the node for fh, call with the lock held
func (of *openFiles) get(fh uint64) (i int, node mountlib.Noder, errc int) {
	receivedMark := uint8(fh)
	if receivedMark != of.mark {
		fs.Debugf(nil, "Bad file handle: bad mark 0x%X != 0x%X: 0x%X", receivedMark, of.mark, fh)
		return i, nil, -fuse.EBADF
	}
	i64 := fh >> 8
	if i64 > uint64(len(of.nodes)) {
		fs.Debugf(nil, "Bad file handle: too big: 0x%X", fh)
		return i, nil, -fuse.EBADF
	}
	i = int(i64)
	node = of.nodes[i]
	if node == nil {
		fs.Debugf(nil, "Bad file handle: nil node: 0x%X", fh)
		return i, nil, -fuse.EBADF
	}
	return i, node, 0
}

// Get the node for the file handle
func (of *openFiles) Get(fh uint64) (node mountlib.Noder, errc int) {
	of.mu.Lock()
	_, node, errc = of.get(fh)
	of.mu.Unlock()
	return
}

// Close the node
func (of *openFiles) Close(fh uint64) (errc int) {
	of.mu.Lock()
	i, _, errc := of.get(fh)
	if errc == 0 {
		of.nodes[i] = nil
	}
	of.mu.Unlock()
	return
}

// lookup a Node given a path
func (fsys *FS) lookupNode(path string) (node mountlib.Node, errc int) {
	node, err := fsys.FS.Lookup(path)
	return node, translateError(err)
}

// lookup a Dir given a path
func (fsys *FS) lookupDir(path string) (dir *mountlib.Dir, errc int) {
	node, errc := fsys.lookupNode(path)
	if errc != 0 {
		return nil, errc
	}
	dir, ok := node.(*mountlib.Dir)
	if !ok {
		return nil, -fuse.ENOTDIR
	}
	return dir, 0
}

// lookup a parent Dir given a path returning the dir and the leaf
func (fsys *FS) lookupParentDir(filePath string) (leaf string, dir *mountlib.Dir, errc int) {
	parentDir, leaf := path.Split(filePath)
	dir, errc = fsys.lookupDir(parentDir)
	return leaf, dir, errc
}

// lookup a File given a path
func (fsys *FS) lookupFile(path string) (file *mountlib.File, errc int) {
	node, errc := fsys.lookupNode(path)
	if errc != 0 {
		return nil, errc
	}
	file, ok := node.(*mountlib.File)
	if !ok {
		return nil, -fuse.EISDIR
	}
	return file, 0
}

// Get the underlying openFile handle from the file handle
func (fsys *FS) getOpenFilesFromFh(fh uint64) (of *openFiles, errc int) {
	switch {
	case fsys.openFilesRd.InRange(fh):
		return fsys.openFilesRd, 0
	case fsys.openFilesWr.InRange(fh):
		return fsys.openFilesWr, 0
	case fsys.openDirs.InRange(fh):
		return fsys.openDirs, 0
	}
	return nil, -fuse.EBADF
}

// Get the underlying handle from the file handle
func (fsys *FS) getHandleFromFh(fh uint64) (handle mountlib.Noder, errc int) {
	of, errc := fsys.getOpenFilesFromFh(fh)
	if errc != 0 {
		return nil, errc
	}
	return of.Get(fh)
}

// get a node from the path or from the fh if not fhUnset
func (fsys *FS) getNode(path string, fh uint64) (node mountlib.Node, errc int) {
	if fh == fhUnset {
		node, errc = fsys.lookupNode(path)
	} else {
		var n mountlib.Noder
		n, errc = fsys.getHandleFromFh(fh)
		if errc == 0 {
			node = n.Node()
		}
	}
	return
}

// stat fills up the stat block for Node
func (fsys *FS) stat(node mountlib.Node, stat *fuse.Stat_t) (errc int) {
	var Size uint64
	var Blocks uint64
	var modTime time.Time
	var Mode os.FileMode
	switch x := node.(type) {
	case *mountlib.Dir:
		modTime = x.ModTime()
		Mode = dirPerms | fuse.S_IFDIR
	case *mountlib.File:
		var err error
		modTime, Size, Blocks, err = x.Attr(noModTime)
		if err != nil {
			return translateError(err)
		}
		Mode = filePerms | fuse.S_IFREG
	}
	//stat.Dev = 1
	stat.Ino = node.Inode() // FIXME do we need to set the inode number?
	stat.Mode = uint32(Mode)
	stat.Nlink = 1
	stat.Uid = uid
	stat.Gid = gid
	//stat.Rdev
	stat.Size = int64(Size)
	t := fuse.NewTimespec(modTime)
	stat.Atim = t
	stat.Mtim = t
	stat.Ctim = t
	stat.Blksize = 512
	stat.Blocks = int64(Blocks)
	stat.Birthtim = t
	// fs.Debugf(nil, "stat = %+v", *stat)
	return 0
}

// Init is called after the filesystem is ready
func (fsys *FS) Init() {
	defer fs.Trace(fsys.f, "")("")
	close(fsys.ready)
}

// Destroy is called when it is unmounted (note that depending on how
// the file system is terminated the file system may not receive the
// Destroy call).
func (fsys *FS) Destroy() {
	defer fs.Trace(fsys.f, "")("")
}

// Getattr reads the attributes for path
func (fsys *FS) Getattr(path string, stat *fuse.Stat_t, fh uint64) (errc int) {
	defer fs.Trace(path, "fh=0x%X", fh)("errc=%v", &errc)
	node, errc := fsys.getNode(path, fh)
	if errc == 0 {
		errc = fsys.stat(node, stat)
	}
	return
}

// Opendir opens path as a directory
func (fsys *FS) Opendir(path string) (errc int, fh uint64) {
	defer fs.Trace(path, "")("errc=%d, fh=0x%X", &errc, &fh)
	dir, errc := fsys.lookupDir(path)
	if errc == 0 {
		fh = fsys.openDirs.Open(dir)
	} else {
		fh = fhUnset
	}
	return
}

// Readdir reads the directory at dirPath
func (fsys *FS) Readdir(dirPath string,
	fill func(name string, stat *fuse.Stat_t, ofst int64) bool,
	ofst int64,
	fh uint64) (errc int) {
	itemsRead := -1
	defer fs.Trace(dirPath, "ofst=%d, fh=0x%X", ofst, fh)("items=%d, errc=%d", &itemsRead, &errc)

	node, errc := fsys.openDirs.Get(fh)
	if errc != 0 {
		return errc
	}

	dir, ok := node.(*mountlib.Dir)
	if !ok {
		return -fuse.ENOTDIR
	}

	items, err := dir.ReadDirAll()
	if err != nil {
		return translateError(err)
	}

	// Optionally, create a struct stat that describes the file as
	// for getattr (but FUSE only looks at st_ino and the
	// file-type bits of st_mode).
	//
	// FIXME If you call host.SetCapReaddirPlus() then WinFsp will
	// use the full stat information - a Useful optimization on
	// Windows.
	//
	// NB we are using the first mode for readdir: The readdir
	// implementation ignores the offset parameter, and passes
	// zero to the filler function's offset. The filler function
	// will not return '1' (unless an error happens), so the whole
	// directory is read in a single readdir operation.
	fill(".", nil, 0)
	fill("..", nil, 0)
	for _, item := range items {
		name := path.Base(item.Obj.Remote())
		fill(name, nil, 0)
	}
	itemsRead = len(items)
	return 0
}

// Releasedir finished reading the directory
func (fsys *FS) Releasedir(path string, fh uint64) (errc int) {
	defer fs.Trace(path, "fh=0x%X", fh)("errc=%d", &errc)
	return fsys.openDirs.Close(fh)
}

// Statfs reads overall stats on the filessystem
func (fsys *FS) Statfs(path string, stat *fuse.Statfs_t) (errc int) {
	defer fs.Trace(path, "")("stat=%+v, errc=%d", stat, &errc)
	const blockSize = 4096
	fsBlocks := uint64(1 << 50)
	if runtime.GOOS == "windows" {
		fsBlocks = (1 << 43) - 1
	}
	stat.Blocks = fsBlocks  // Total data blocks in file system.
	stat.Bfree = fsBlocks   // Free blocks in file system.
	stat.Bavail = fsBlocks  // Free blocks in file system if you're not root.
	stat.Files = 1E9        // Total files in file system.
	stat.Ffree = 1E9        // Free files in file system.
	stat.Bsize = blockSize  // Block size
	stat.Namemax = 255      // Maximum file name length?
	stat.Frsize = blockSize // Fragment size, smallest addressable data size in the file system.
	return 0
}

// Open opens a file
func (fsys *FS) Open(path string, flags int) (errc int, fh uint64) {
	defer fs.Trace(path, "flags=0x%X", flags)("errc=%d, fh=0x%X", &errc, &fh)
	file, errc := fsys.lookupFile(path)
	if errc != 0 {
		return errc, fhUnset
	}
	rdwrMode := flags & fuse.O_ACCMODE
	var err error
	var handle mountlib.Noder
	switch {
	case rdwrMode == fuse.O_RDONLY:
		handle, err = file.OpenRead()
		if err != nil {
			return translateError(err), fhUnset
		}
		return 0, fsys.openFilesRd.Open(handle)
	case rdwrMode == fuse.O_WRONLY || (rdwrMode == fuse.O_RDWR && (flags&fuse.O_TRUNC) != 0):
		handle, err = file.OpenWrite()
		if err != nil {
			return translateError(err), fhUnset
		}
		return 0, fsys.openFilesWr.Open(handle)
	case rdwrMode == fuse.O_RDWR:
		fs.Errorf(path, "Can't open for Read and Write")
		return -fuse.EPERM, fhUnset
	}
	fs.Errorf(path, "Can't figure out how to open with flags: 0x%X", flags)
	return -fuse.EPERM, fhUnset
}

// Create creates and opens a file.
func (fsys *FS) Create(filePath string, flags int, mode uint32) (errc int, fh uint64) {
	defer fs.Trace(filePath, "flags=0x%X, mode=0%o", flags, mode)("errc=%d, fh=0x%X", &errc, &fh)
	leaf, parentDir, errc := fsys.lookupParentDir(filePath)
	if errc != 0 {
		return errc, fhUnset
	}
	_, handle, err := parentDir.Create(leaf)
	if err != nil {
		return translateError(err), fhUnset
	}
	return 0, fsys.openFilesWr.Open(handle)
}

// Truncate truncates a file to size
func (fsys *FS) Truncate(path string, size int64, fh uint64) (errc int) {
	defer fs.Trace(path, "size=%d, fh=0x%X", size, fh)("errc=%d", &errc)
	node, errc := fsys.getNode(path, fh)
	if errc != 0 {
		return errc
	}
	file, ok := node.(*mountlib.File)
	if !ok {
		return -fuse.EIO
	}
	// Read the size so far
	_, currentSize, _, err := file.Attr(true)
	if err != nil {
		return translateError(err)
	}
	fs.Debugf(path, "truncate to %d, currentSize %d", size, currentSize)
	if int64(currentSize) != size {
		fs.Errorf(path, "Can't truncate files")
		return -fuse.EPERM
	}
	return 0
}

func (fsys *FS) Read(path string, buff []byte, ofst int64, fh uint64) (n int) {
	defer fs.Trace(path, "ofst=%d, fh=0x%X", ofst, fh)("n=%d", &n)
	// FIXME detect seek
	handle, errc := fsys.openFilesRd.Get(fh)
	if errc != 0 {
		return errc
	}
	rfh, ok := handle.(*mountlib.ReadFileHandle)
	if !ok {
		// Can only read from read file handle
		return -fuse.EIO
	}
	data, err := rfh.Read(int64(len(buff)), ofst)
	if err != nil {
		return translateError(err)
	}
	n = copy(buff, data)
	return n
}

func (fsys *FS) Write(path string, buff []byte, ofst int64, fh uint64) (n int) {
	defer fs.Trace(path, "ofst=%d, fh=0x%X", ofst, fh)("n=%d", &n)
	// FIXME detect seek
	handle, errc := fsys.openFilesWr.Get(fh)
	if errc != 0 {
		return errc
	}
	wfh, ok := handle.(*mountlib.WriteFileHandle)
	if !ok {
		// Can only write to write file handle
		return -fuse.EIO
	}
	// FIXME made Write return int and Read take int since must fit in RAM
	n64, err := wfh.Write(buff, ofst)
	if err != nil {
		return translateError(err)
	}
	return int(n64)
}

// Flush flushes an open file descriptor or path
func (fsys *FS) Flush(path string, fh uint64) (errc int) {
	defer fs.Trace(path, "fh=0x%X", fh)("errc=%d", &errc)
	handle, errc := fsys.getHandleFromFh(fh)
	if errc != 0 {
		return errc
	}
	var err error
	switch x := handle.(type) {
	case *mountlib.ReadFileHandle:
		err = x.Flush()
	case *mountlib.WriteFileHandle:
		err = x.Flush()
	default:
		return -fuse.EIO
	}
	return translateError(err)
}

// Release closes the file if still open
func (fsys *FS) Release(path string, fh uint64) (errc int) {
	defer fs.Trace(path, "fh=0x%X", fh)("errc=%d", &errc)
	of, errc := fsys.getOpenFilesFromFh(fh)
	if errc != 0 {
		return errc
	}
	handle, errc := of.Get(fh)
	if errc != 0 {
		return errc
	}
	_ = of.Close(fh)
	var err error
	switch x := handle.(type) {
	case *mountlib.ReadFileHandle:
		err = x.Release()
	case *mountlib.WriteFileHandle:
		err = x.Release()
	default:
		return -fuse.EIO
	}
	return translateError(err)
}

// Unlink removes a file.
func (fsys *FS) Unlink(filePath string) (errc int) {
	defer fs.Trace(filePath, "")("errc=%d", &errc)
	leaf, parentDir, errc := fsys.lookupParentDir(filePath)
	if errc != 0 {
		return errc
	}
	return translateError(parentDir.Remove(leaf))
}

// Mkdir creates a directory.
func (fsys *FS) Mkdir(dirPath string, mode uint32) (errc int) {
	defer fs.Trace(dirPath, "mode=0%o", mode)("errc=%d", &errc)
	leaf, parentDir, errc := fsys.lookupParentDir(dirPath)
	if errc != 0 {
		return errc
	}
	_, err := parentDir.Mkdir(leaf)
	return translateError(err)
}

// Rmdir removes a directory
func (fsys *FS) Rmdir(dirPath string) (errc int) {
	defer fs.Trace(dirPath, "")("errc=%d", &errc)
	leaf, parentDir, errc := fsys.lookupParentDir(dirPath)
	if errc != 0 {
		return errc
	}
	return translateError(parentDir.Remove(leaf))
}

// Rename renames a file.
func (fsys *FS) Rename(oldPath string, newPath string) (errc int) {
	defer fs.Trace(oldPath, "newPath=%q", newPath)("errc=%d", &errc)
	oldLeaf, oldParentDir, errc := fsys.lookupParentDir(oldPath)
	if errc != 0 {
		return errc
	}
	newLeaf, newParentDir, errc := fsys.lookupParentDir(newPath)
	if errc != 0 {
		return errc
	}
	return translateError(oldParentDir.Rename(oldLeaf, newLeaf, newParentDir))
}

// Utimens changes the access and modification times of a file.
func (fsys *FS) Utimens(path string, tmsp []fuse.Timespec) (errc int) {
	defer fs.Trace(path, "tmsp=%+v", tmsp)("errc=%d", &errc)
	node, errc := fsys.lookupNode(path)
	if errc != 0 {
		return errc
	}
	var t time.Time
	if tmsp == nil || len(tmsp) < 2 {
		t = time.Now()
	} else {
		t = tmsp[1].Time()
	}
	var err error
	switch x := node.(type) {
	case *mountlib.Dir:
		err = x.SetModTime(t)
	case *mountlib.File:
		err = x.SetModTime(t)
	}
	return translateError(err)
}

// Mknod creates a file node.
func (fsys *FS) Mknod(path string, mode uint32, dev uint64) (errc int) {
	defer fs.Trace(path, "mode=0x%X, dev=0x%X", mode, dev)("errc=%d", &errc)
	return -fuse.ENOSYS
}

// Fsync synchronizes file contents.
func (fsys *FS) Fsync(path string, datasync bool, fh uint64) (errc int) {
	defer fs.Trace(path, "datasync=%v, fh=0x%X", datasync, fh)("errc=%d", &errc)
	// This is a no-op for rclone
	return 0
}

// Link creates a hard link to a file.
func (fsys *FS) Link(oldpath string, newpath string) (errc int) {
	defer fs.Trace(oldpath, "newpath=%q", newpath)("errc=%d", &errc)
	return -fuse.ENOSYS
}

// Symlink creates a symbolic link.
func (fsys *FS) Symlink(target string, newpath string) (errc int) {
	defer fs.Trace(target, "newpath=%q", newpath)("errc=%d", &errc)
	return -fuse.ENOSYS
}

// Readlink reads the target of a symbolic link.
func (fsys *FS) Readlink(path string) (errc int, linkPath string) {
	defer fs.Trace(path, "")("linkPath=%q, errc=%d", &linkPath, &errc)
	return -fuse.ENOSYS, ""
}

// Chmod changes the permission bits of a file.
func (fsys *FS) Chmod(path string, mode uint32) (errc int) {
	defer fs.Trace(path, "mode=0%o", mode)("errc=%d", &errc)
	// This is a no-op for rclone
	return 0
}

// Chown changes the owner and group of a file.
func (fsys *FS) Chown(path string, uid uint32, gid uint32) (errc int) {
	defer fs.Trace(path, "uid=%d, gid=%d", uid, gid)("errc=%d", &errc)
	// This is a no-op for rclone
	return 0
}

// Access checks file access permissions.
func (fsys *FS) Access(path string, mask uint32) (errc int) {
	defer fs.Trace(path, "mask=0%o", mask)("errc=%d", &errc)
	// This is a no-op for rclone
	return 0
}

// Fsyncdir synchronizes directory contents.
func (fsys *FS) Fsyncdir(path string, datasync bool, fh uint64) (errc int) {
	defer fs.Trace(path, "datasync=%v, fh=0x%X", datasync, fh)("errc=%d", &errc)
	// This is a no-op for rclone
	return 0
}

// Setxattr sets extended attributes.
func (fsys *FS) Setxattr(path string, name string, value []byte, flags int) (errc int) {
	return -fuse.ENOSYS
}

// Getxattr gets extended attributes.
func (fsys *FS) Getxattr(path string, name string) (errc int, value []byte) {
	return -fuse.ENOSYS, nil
}

// Removexattr removes extended attributes.
func (fsys *FS) Removexattr(path string, name string) (errc int) {
	return -fuse.ENOSYS
}

// Listxattr lists extended attributes.
func (fsys *FS) Listxattr(path string, fill func(name string) bool) (errc int) {
	return -fuse.ENOSYS
}

// Translate errors from mountlib
func translateError(err error) (errc int) {
	if err == nil {
		return 0
	}
	cause := errors.Cause(err)
	if mErr, ok := cause.(mountlib.Error); ok {
		switch mErr {
		case mountlib.OK:
			return 0
		case mountlib.ENOENT:
			return -fuse.ENOENT
		case mountlib.ENOTEMPTY:
			return -fuse.ENOTEMPTY
		case mountlib.EEXIST:
			return -fuse.EEXIST
		case mountlib.ESPIPE:
			return -fuse.ESPIPE
		case mountlib.EBADF:
			return -fuse.EBADF
		}
	}
	fs.Errorf(nil, "IO error: %v", err)
	return -fuse.EIO
}