// precalcNextBuf follows the next link in line and loads it from the DAGService,
// setting the next buffer to read from
func (dr *DagReader) precalcNextBuf() error {
	if dr.position >= len(dr.node.Links) {
		return io.EOF
	}
	nxt, err := dr.node.Links[dr.position].GetNode(dr.serv)
	if err != nil {
		return err
	}
	pb := new(ftpb.Data)
	err = proto.Unmarshal(nxt.Data, pb)
	if err != nil {
		return err
	}
	dr.position++

	switch pb.GetType() {
	case ftpb.Data_Directory:
		// A directory should not exist within a file
		return ft.ErrInvalidDirLocation
	case ftpb.Data_File:
		//TODO: this *should* work, needs testing first
		log.Warning("Running untested code for multilayered indirect FS reads.")
		subr, err := NewDagReader(nxt, dr.serv)
		if err != nil {
			return err
		}
		dr.buf = subr
		return nil
	case ftpb.Data_Raw:
		dr.buf = bytes.NewBuffer(pb.GetData())
		return nil
	default:
		return ft.ErrUnrecognizedType
	}
}

func UnwrapData(data []byte) ([]byte, error) {
	pbdata := new(pb.Data)
	err := proto.Unmarshal(data, pbdata)
	if err != nil {
		return nil, err
	}
	return pbdata.GetData(), nil
}

func (mb *MultiBlock) GetBytes() ([]byte, error) {
	pbn := new(pb.Data)
	t := pb.Data_File
	pbn.Type = &t
	pbn.Filesize = proto.Uint64(uint64(len(mb.Data)) + mb.subtotal)
	pbn.Blocksizes = mb.blocksizes
	pbn.Data = mb.Data
	return proto.Marshal(pbn)
}

// Returns Bytes that represent a Directory
func FolderPBData() []byte {
	pbfile := new(pb.Data)
	typ := pb.Data_Directory
	pbfile.Type = &typ

	data, err := proto.Marshal(pbfile)
	if err != nil {
		//this really shouldnt happen, i promise
		panic(err)
	}
	return data
}

func WrapData(b []byte) []byte {
	pbdata := new(pb.Data)
	typ := pb.Data_Raw
	pbdata.Data = b
	pbdata.Type = &typ

	out, err := proto.Marshal(pbdata)
	if err != nil {
		// This shouldnt happen. seriously.
		panic(err)
	}

	return out
}

func FilePBData(data []byte, totalsize uint64) []byte {
	pbfile := new(pb.Data)
	typ := pb.Data_File
	pbfile.Type = &typ
	pbfile.Data = data
	pbfile.Filesize = proto.Uint64(totalsize)

	data, err := proto.Marshal(pbfile)
	if err != nil {
		// This really shouldnt happen, i promise
		// The only failure case for marshal is if required fields
		// are not filled out, and they all are. If the proto object
		// gets changed and nobody updates this function, the code
		// should panic due to programmer error
		panic(err)
	}
	return data
}

func DataSize(data []byte) (uint64, error) {
	pbdata := new(pb.Data)
	err := proto.Unmarshal(data, pbdata)
	if err != nil {
		return 0, err
	}

	switch pbdata.GetType() {
	case pb.Data_Directory:
		return 0, errors.New("Cant get data size of directory!")
	case pb.Data_File:
		return pbdata.GetFilesize(), nil
	case pb.Data_Raw:
		return uint64(len(pbdata.GetData())), nil
	default:
		return 0, errors.New("Unrecognized node data type!")
	}
}

// NewDagReader creates a new reader object that reads the data represented by the given
// node, using the passed in DAGService for data retreival
func NewDagReader(n *mdag.Node, serv mdag.DAGService) (io.Reader, error) {
	pb := new(ftpb.Data)
	err := proto.Unmarshal(n.Data, pb)
	if err != nil {
		return nil, err
	}

	switch pb.GetType() {
	case ftpb.Data_Directory:
		// Dont allow reading directories
		return nil, ErrIsDir
	case ftpb.Data_File:
		return &DagReader{
			node: n,
			serv: serv,
			buf:  bytes.NewBuffer(pb.GetData()),
		}, nil
	case ftpb.Data_Raw:
		// Raw block will just be a single level, return a byte buffer
		return bytes.NewBuffer(pb.GetData()), nil
	default:
		return nil, ft.ErrUnrecognizedType
	}
}