// Save stores data in the backend at the handle.
func (r *SFTP) Save(h backend.Handle, p []byte) (err error) {
	if err := h.Valid(); err != nil {
		return err
	}

	filename, tmpfile, err := r.tempFile()
	debug.Log("sftp.Save", "save %v (%d bytes) to %v", h, len(p), filename)

	n, err := tmpfile.Write(p)
	if err != nil {
		return err
	}

	if n != len(p) {
		return errors.New("not all bytes writen")
	}

	err = tmpfile.Close()
	if err != nil {
		return err
	}

	err = r.renameFile(filename, h.Type, h.Name)
	debug.Log("sftp.Save", "save %v: rename %v: %v",
		h, filepath.Base(filename), err)
	if err != nil {
		return fmt.Errorf("sftp: renameFile: %v", err)
	}

	return nil
}

// Save stores data in the backend at the handle.
func (be s3) Save(h backend.Handle, p []byte) (err error) {
	if err := h.Valid(); err != nil {
		return err
	}

	debug.Log("s3.Save", "%v bytes at %d", len(p), h)

	path := s3path(h.Type, h.Name)

	// Check key does not already exist
	_, err = be.client.StatObject(be.bucketname, path)
	if err == nil {
		debug.Log("s3.blob.Finalize()", "%v already exists", h)
		return errors.New("key already exists")
	}

	<-be.connChan
	defer func() {
		be.connChan <- struct{}{}
	}()

	debug.Log("s3.Save", "PutObject(%v, %v, %v, %v)",
		be.bucketname, path, int64(len(p)), "binary/octet-stream")
	n, err := be.client.PutObject(be.bucketname, path, bytes.NewReader(p), "binary/octet-stream")
	debug.Log("s3.Save", "%v -> %v bytes, err %#v", path, n, err)

	return err
}

// Load returns the data stored in the backend for h at the given offset
// and saves it in p. Load has the same semantics as io.ReaderAt.
func (r *SFTP) Load(h backend.Handle, p []byte, off int64) (n int, err error) {
	if err := h.Valid(); err != nil {
		return 0, err
	}

	f, err := r.c.Open(r.filename(h.Type, h.Name))
	if err != nil {
		return 0, err
	}

	defer func() {
		e := f.Close()
		if err == nil && e != nil {
			err = e
		}
	}()

	if off > 0 {
		_, err = f.Seek(off, 0)
		if err != nil {
			return 0, err
		}
	}

	return io.ReadFull(f, p)
}

func memLoad(be *MemoryBackend, h backend.Handle, p []byte, off int64) (int, error) {
	if err := h.Valid(); err != nil {
		return 0, err
	}

	be.m.Lock()
	defer be.m.Unlock()

	if h.Type == backend.Config {
		h.Name = ""
	}

	debug.Log("MemoryBackend.Load", "get %v offset %v len %v", h, off, len(p))

	if _, ok := be.data[entry{h.Type, h.Name}]; !ok {
		return 0, errors.New("no such data")
	}

	buf := be.data[entry{h.Type, h.Name}]
	if off > int64(len(buf)) {
		return 0, errors.New("offset beyond end of file")
	}

	buf = buf[off:]

	n := copy(p, buf)

	if len(p) > len(buf) {
		return n, io.ErrUnexpectedEOF
	}

	return n, nil
}

// Stat returns information about a blob.
func (r *SFTP) Stat(h backend.Handle) (backend.BlobInfo, error) {
	if err := h.Valid(); err != nil {
		return backend.BlobInfo{}, err
	}

	fi, err := r.c.Lstat(r.filename(h.Type, h.Name))
	if err != nil {
		return backend.BlobInfo{}, err
	}

	return backend.BlobInfo{Size: fi.Size()}, nil
}

// Stat returns information about a blob.
func (b *Local) Stat(h backend.Handle) (backend.BlobInfo, error) {
	if err := h.Valid(); err != nil {
		return backend.BlobInfo{}, err
	}

	fi, err := os.Stat(filename(b.p, h.Type, h.Name))
	if err != nil {
		return backend.BlobInfo{}, err
	}

	return backend.BlobInfo{Size: fi.Size()}, nil
}

func memStat(be *MemoryBackend, h backend.Handle) (backend.BlobInfo, error) {
	be.m.Lock()
	defer be.m.Unlock()

	if err := h.Valid(); err != nil {
		return backend.BlobInfo{}, err
	}

	if h.Type == backend.Config {
		h.Name = ""
	}

	debug.Log("MemoryBackend.Stat", "stat %v", h)

	e, ok := be.data[entry{h.Type, h.Name}]
	if !ok {
		return backend.BlobInfo{}, errors.New("no such data")
	}

	return backend.BlobInfo{Size: int64(len(e))}, nil
}

// Save stores data in the backend at the handle.
func (b *Local) Save(h backend.Handle, p []byte) (err error) {
	if err := h.Valid(); err != nil {
		return err
	}

	tmpfile, err := writeToTempfile(filepath.Join(b.p, backend.Paths.Temp), p)
	debug.Log("local.Save", "saved %v (%d bytes) to %v", h, len(p), tmpfile)

	filename := filename(b.p, h.Type, h.Name)

	// test if new path already exists
	if _, err := os.Stat(filename); err == nil {
		return fmt.Errorf("Rename(): file %v already exists", filename)
	}

	// create directories if necessary, ignore errors
	if h.Type == backend.Data {
		err = os.MkdirAll(filepath.Dir(filename), backend.Modes.Dir)
		if err != nil {
			return err
		}
	}

	err = os.Rename(tmpfile, filename)
	debug.Log("local.Save", "save %v: rename %v -> %v: %v",
		h, filepath.Base(tmpfile), filepath.Base(filename), err)

	if err != nil {
		return err
	}

	// set mode to read-only
	fi, err := os.Stat(filename)
	if err != nil {
		return err
	}

	return setNewFileMode(filename, fi)
}

func memSave(be *MemoryBackend, h backend.Handle, p []byte) error {
	if err := h.Valid(); err != nil {
		return err
	}

	be.m.Lock()
	defer be.m.Unlock()

	if h.Type == backend.Config {
		h.Name = ""
	}

	if _, ok := be.data[entry{h.Type, h.Name}]; ok {
		return errors.New("file already exists")
	}

	debug.Log("MemoryBackend.Save", "save %v bytes at %v", len(p), h)
	buf := make([]byte, len(p))
	copy(buf, p)
	be.data[entry{h.Type, h.Name}] = buf

	return nil
}