package main

import (
	"log"
	"os"
    "context"
    "syscall"
	"github.com/hanwen/go-fuse/v2/fs"
	"github.com/hanwen/go-fuse/v2/fuse"
	"strconv"
	"strings"
)

func (i *Device) HeartRateBytes() ([]byte, error) {
	v, err := i.HeartRate()
	return []byte(strconv.Itoa(int(v)) + "\n"), err
}
func (i *Device) BatteryLevelBytes() ([]byte, error) {
	v, err := i.BatteryLevel()
	return []byte(strconv.Itoa(int(v)) + "\n"), err
}
func (i *Device) StepCountBytes() ([]byte, error) {
	v, err := i.StepCount()
	return []byte(strconv.Itoa(int(v)) + "\n"), err
}
func (i *Device) MotionBytes() ([]byte, error) {
	v, err := i.Motion()
	return []byte(strconv.Itoa(int(v.X)) + " " + strconv.Itoa(int(v.Y)) + " " + strconv.Itoa(int(v.Z)) + "\n"), err
}
func (i *Device) AddressBytes() ([]byte, error) {
	v := i.Address()
	return []byte(v + "\n"), nil
}
func (i *Device) VersionBytes() ([]byte, error) {
	v, err := i.Version()
	return []byte(v + "\n"), err
}


type ITProperty struct {
	name string
	Ino uint64
	f func() ([]byte, error)
}

type ITNode struct {
	fs.Inode
	kind int
	Ino uint64

	lst []DirEntry
	self DirEntry
	path string
}

var properties = []ITProperty {
	ITProperty{"heartrate", 2, nil},
	ITProperty{"battery", 3, nil},
	ITProperty{"motion", 4, nil},
	ITProperty{"stepcount", 5, nil},
	ITProperty{"version", 6, nil},
	ITProperty{"address", 7, nil},
}
var myfs *FS = nil;
var inodemap map[string]uint64 = nil;

var _ = (fs.NodeReaddirer)((*ITNode)(nil))

// Readdir is part of the NodeReaddirer interface
func (n *ITNode) Readdir(ctx context.Context) (fs.DirStream, syscall.Errno) {
	switch n.kind {
	case 0:
		// root folder
		r := make([]fuse.DirEntry, 2)
		r[0] = fuse.DirEntry{
			Name: "device",
			Ino:  0,
			Mode: fuse.S_IFDIR,
		}
		r[1] = fuse.DirEntry{
			Name: "fs",
			Ino:  1,
			Mode: fuse.S_IFDIR,
		}
		return fs.NewListDirStream(r), 0

	case 1:
		// device folder
		r := make([]fuse.DirEntry, 6)
		for ind, value := range properties {
			r[ind] = fuse.DirEntry{
				Name: value.name,
				Ino:  value.Ino,
				Mode: fuse.S_IFREG,
			}
		}

		return fs.NewListDirStream(r), 0

	case 2:
		// on device
		files, _ := myfs.ReadDir(n.path)
		r := make([]fuse.DirEntry, len(files))
		n.lst = files
		for ind, file := range files {
			name := file.path[strings.LastIndex(file.path, "/")+1:]

			ino := inodemap[file.path]
			if ino == 0 {
				ino = uint64(len(inodemap)) + 1
				inodemap[file.path] = ino
			}

			if file.flags & 0b1 == 1 {
				r[ind] = fuse.DirEntry{
					Name: name,
					Mode: fuse.S_IFDIR,
					Ino : ino + 10,
				}
			} else {
				r[ind] = fuse.DirEntry{
					Name: name,
					Mode: fuse.S_IFREG,
					Ino : ino + 10,
				}
			}
		}
		return fs.NewListDirStream(r), 0
	}
	r := make([]fuse.DirEntry, 0)
	return fs.NewListDirStream(r), 0
}

var _ = (fs.NodeLookuper)((*ITNode)(nil))
func (n *ITNode) Lookup(ctx context.Context, name string, out *fuse.EntryOut) (*fs.Inode, syscall.Errno) {
	switch n.kind {
	case 0:
		// root folder
		if name == "device" {
			stable := fs.StableAttr{
				Mode: fuse.S_IFDIR,
				Ino: uint64(0),
			}
			operations := &ITNode{kind: 1, Ino: 0}
			child := n.NewInode(ctx, operations, stable)
			return child, 0
		} else if name == "fs" {
			stable := fs.StableAttr{
				Mode: fuse.S_IFDIR,
				Ino: uint64(1),
			}
			operations := &ITNode{kind: 2, Ino: 1, path : ""}
			child := n.NewInode(ctx, operations, stable)
			return child, 0
		}
	case 1:
		// device folder
		for _, value := range properties {
			if value.name == name {
				stable := fs.StableAttr{
					Mode: fuse.S_IFREG,
					Ino: uint64(value.Ino),
				}
				operations := &ITNode{kind: 3, Ino: value.Ino}
				child := n.NewInode(ctx, operations, stable)
				return child, 0
			}
		}
		return nil, syscall.ENOENT

	case 2:
		// FS object
		for _, file := range n.lst {
			if file.path != n.path + "/" + name {
				continue;
			}
			log.Println("matched", name)

			if file.flags & 0b1 == 1 {
				stable := fs.StableAttr{
					Mode: fuse.S_IFDIR,
					Ino: inodemap[file.path],
				}
				operations := &ITNode{kind: 2, path: file.path}
				child := n.NewInode(ctx, operations, stable)
				return child, 0
			} else {
				stable := fs.StableAttr{
					Mode: fuse.S_IFREG,
					Ino: inodemap[file.path],
				}
				operations := &ITNode{
					kind: 2, path: file.path,
					self: file,
				}
				child := n.NewInode(ctx, operations, stable)
				return child, 0
			}
			break;
		}
	}
	return nil, syscall.ENOENT
}

type bytesFileReadHandle struct {
	content []byte
}
var _ = (fs.FileReader)((*bytesFileReadHandle)(nil))

func (fh *bytesFileReadHandle) Read(ctx context.Context, dest []byte, off int64) (fuse.ReadResult, syscall.Errno) {
	end := off + int64(len(dest))
	if end > int64(len(fh.content)) {
		end = int64(len(fh.content))
	}
	return fuse.ReadResultData(fh.content[off:end]), 0
}

type bytesFileWriteHandle struct {
	content []byte
	path string
}

var _ = (fs.FileWriter)((*bytesFileWriteHandle)(nil))
func (fh *bytesFileWriteHandle) Write(ctx context.Context, data []byte, off int64) (written uint32, errno syscall.Errno) {
	if off != int64(len(fh.content)) {
	}
	fh.content = append(fh.content[:], data[:]...)
	return uint32(len(data)), 0
}

var _ = (fs.FileFlusher)((*bytesFileWriteHandle)(nil))
func (fh *bytesFileWriteHandle) Flush(ctx context.Context) (errno syscall.Errno) {
	fp, err := myfs.Create(fh.path, uint32(len(fh.content)))
	if err != nil {
		return syscall.EROFS
	}
	nread, err := fp.Write(fh.content)
	if err != nil || nread != len(fh.content) {
		return syscall.EROFS
	}

	return 0
}

var _ = (fs.NodeGetattrer)((*ITNode)(nil))
func (bn *ITNode) Getattr(ctx context.Context, f fs.FileHandle, out *fuse.AttrOut) syscall.Errno {
	out.Ino = bn.Ino
	out.Mtime = bn.self.modtime
	out.Ctime = bn.self.modtime
	out.Atime = bn.self.modtime
	out.Size = uint64(bn.self.size)
	return 0
}

var _ = (fs.NodeSetattrer)((*ITNode)(nil))
func (bn *ITNode) Setattr(ctx context.Context, fh fs.FileHandle, in *fuse.SetAttrIn, out *fuse.AttrOut) syscall.Errno {
	out.Size = 0;
	out.Mtime = 0;
	return 0
}

var _ = (fs.NodeOpener)((*ITNode)(nil))
func (f *ITNode) Open(ctx context.Context, openFlags uint32) (fh fs.FileHandle, fuseFlags uint32, errno syscall.Errno) {
	switch f.kind {
	case 2:
		// FS file
		if openFlags&syscall.O_RDWR != 0 {
			return nil, 0, syscall.EROFS
		}

		if openFlags & syscall.O_WRONLY != 0 {
			fh = &bytesFileWriteHandle{
				path : f.path,
				content : make([]byte, 0),
			}
			return fh, fuse.FOPEN_DIRECT_IO, 0
		} else {
			fp, err := myfs.Open(f.path)
			if err != nil {
				return nil, 0, syscall.EROFS
			}

			buf := make([]byte, f.self.size);
			nread, err := fp.Read(buf)
			if err != nil || nread != int(f.self.size) {
				return nil, 0, syscall.EROFS
			}

			fh = &bytesFileReadHandle{
				content: buf,
			}
			return fh, fuse.FOPEN_DIRECT_IO, 0
		}

	case 3:
		// Device file

		// disallow writes
		if openFlags&(syscall.O_RDWR|syscall.O_WRONLY) != 0 {
			return nil, 0, syscall.EROFS
		}

		for _, value := range properties {
			if value.Ino == f.Ino {
				ans, err := value.f()
				if err != nil {
					return nil, 0, syscall.EROFS
				}

				fh = &bytesFileReadHandle{
					content: ans,
				}
				return fh, fuse.FOPEN_DIRECT_IO, 0
			}
		}
	}
	return nil, 0, syscall.EROFS
}

var _ = (fs.NodeCreater)((*ITNode)(nil))
func (f *ITNode) Create(ctx context.Context, name string, flags uint32, mode uint32, out *fuse.EntryOut) (node *fs.Inode, fh fs.FileHandle, fuseFlags uint32, errno syscall.Errno) {
	if f.kind != 2 {
		return nil, nil, 0, syscall.EROFS
	}

	path := f.path + "/" + name
	ino := uint64(len(inodemap)) + 11
	inodemap[path] = ino

	stable := fs.StableAttr{
		Mode: fuse.S_IFREG,
		Ino: ino,
	}
	operations := &ITNode{
		kind: 2, Ino: ino,
		path : path,
	}
	node = f.NewInode(ctx, operations, stable)

	fh = &bytesFileWriteHandle{
		path : path,
		content : make([]byte, 0),
	}

	errno = 0
	return node, fh, fuseFlags, 0
}

func main() {
	// This is where we'll mount the FS
	mntDir := "/tmp/x"
	os.Mkdir(mntDir, 0755)
	root := &ITNode{kind: 0}
	server, err := fs.Mount(mntDir, root, &fs.Options{
		MountOptions: fuse.MountOptions{
			// Set to true to see how the file system works.
			Debug: false,
		},
	})
	if err != nil {
		log.Panic(err)
	}

	dev := Device{};

	properties[0].f = dev.HeartRateBytes;
	properties[1].f = dev.BatteryLevelBytes;
	properties[2].f = dev.MotionBytes;
	properties[3].f = dev.StepCountBytes;
	properties[4].f = dev.VersionBytes;
	properties[5].f = dev.AddressBytes;

	log.Printf("Mounted on %s", mntDir)
	log.Printf("Unmount by calling 'fusermount -u %s'", mntDir)

	myfs = &FS{};
	inodemap = make(map[string]uint64)

	// Wait until unmount before exiting
	server.Wait()
}