func (rw *RefWriter) writeRefsRecursive(n *dag.Node) (int, error) {
	nkey, err := n.Key()
	if err != nil {
		return 0, err
	}

	var count int
	for i, ng := range rw.DAG.GetDAG(rw.Ctx, n) {
		lk := key.Key(n.Links[i].Hash)
		if rw.skip(lk) {
			continue
		}

		if err := rw.WriteEdge(nkey, lk, n.Links[i].Name); err != nil {
			return count, err
		}

		nd, err := ng.Get(rw.Ctx)
		if err != nil {
			return count, err
		}

		c, err := rw.writeRefsRecursive(nd)
		count += c
		if err != nil {
			return count, err
		}
	}
	return count, nil
}

func (rw *RefWriter) writeRefsSingle(n *dag.Node) (int, error) {
	nkey, err := n.Key()
	if err != nil {
		return 0, err
	}

	if rw.skip(nkey) {
		return 0, nil
	}

	count := 0
	for _, l := range n.Links {
		lk := key.Key(l.Hash)

		if rw.skip(lk) {
			continue
		}

		if err := rw.WriteEdge(nkey, lk, l.Name); err != nil {
			return count, err
		}
		count++
	}
	return count, nil
}

func randNode() (*merkledag.Node, key.Key) {
	node := new(merkledag.Node)
	node.Data = make([]byte, 32)
	util.NewTimeSeededRand().Read(node.Data)
	k, _ := node.Key()
	return node, k
}

func randNode() (*mdag.Node, key.Key) {
	nd := new(mdag.Node)
	nd.Data = make([]byte, 32)
	util.NewTimeSeededRand().Read(nd.Data)
	k, _ := nd.Key()
	return nd, k
}

func AddMetadataTo(n *core.IpfsNode, skey string, m *ft.Metadata) (string, error) {
	ukey := key.B58KeyDecode(skey)

	nd, err := n.DAG.Get(n.Context(), ukey)
	if err != nil {
		return "", err
	}

	mdnode := new(dag.Node)
	mdata, err := ft.BytesForMetadata(m)
	if err != nil {
		return "", err
	}

	mdnode.Data = mdata
	if err := mdnode.AddNodeLinkClean("file", nd); err != nil {
		return "", err
	}

	nk, err := n.DAG.Add(mdnode)
	if err != nil {
		return "", err
	}

	return nk.B58String(), nil
}

func (p *pinner) pinIndirectRecurse(ctx context.Context, node *mdag.Node) error {
	k, err := node.Key()
	if err != nil {
		return err
	}

	p.indirPin.Increment(k)
	return p.pinLinks(ctx, node)
}

func NewDagModifier(ctx context.Context, from *mdag.Node, serv mdag.DAGService, mp pin.ManualPinner, spl chunk.SplitterGen) (*DagModifier, error) {
	return &DagModifier{
		curNode:  from.Copy(),
		dagserv:  serv,
		splitter: spl,
		ctx:      ctx,
		mp:       mp,
	}, nil
}

func nodeFromTemplate(template string) (*dag.Node, error) {
	switch template {
	case "unixfs-dir":
		nd := new(dag.Node)
		nd.Data = ft.FolderPBData()
		return nd, nil
	default:
		return nil, fmt.Errorf("template '%s' not found", template)
	}
}

func Diff(ctx context.Context, ds dag.DAGService, a, b *dag.Node) []*Change {
	if len(a.Links) == 0 && len(b.Links) == 0 {
		ak, _ := a.Key()
		bk, _ := b.Key()
		return []*Change{
			&Change{
				Type:   Mod,
				Before: ak,
				After:  bk,
			},
		}
	}

	var out []*Change
	clean_a := a.Copy()
	clean_b := b.Copy()

	// strip out unchanged stuff
	for _, lnk := range a.Links {
		l, err := b.GetNodeLink(lnk.Name)
		if err == nil {
			if bytes.Equal(l.Hash, lnk.Hash) {
				// no change... ignore it
			} else {
				anode, _ := lnk.GetNode(ctx, ds)
				bnode, _ := l.GetNode(ctx, ds)
				sub := Diff(ctx, ds, anode, bnode)

				for _, subc := range sub {
					subc.Path = path.Join(lnk.Name, subc.Path)
					out = append(out, subc)
				}
			}
			clean_a.RemoveNodeLink(l.Name)
			clean_b.RemoveNodeLink(l.Name)
		}
	}

	for _, lnk := range clean_a.Links {
		out = append(out, &Change{
			Type:   Remove,
			Path:   lnk.Name,
			Before: key.Key(lnk.Hash),
		})
	}
	for _, lnk := range clean_b.Links {
		out = append(out, &Change{
			Type:  Add,
			Path:  lnk.Name,
			After: key.Key(lnk.Hash),
		})
	}

	return out
}

func (t *traversal) shouldSkip(n *mdag.Node) (bool, error) {
	if t.opts.SkipDuplicates {
		k, err := n.Key()
		if err != nil {
			return true, err
		}

		if _, found := t.seen[string(k)]; found {
			return true, nil
		}
		t.seen[string(k)] = struct{}{}
	}

	return false, nil
}

func (params *adder) addNode(node *dag.Node, path string) error {
	// patch it into the root
	if path == "" {
		key, err := node.Key()
		if err != nil {
			return err
		}

		path = key.Pretty()
	}

	if err := params.editor.InsertNodeAtPath(params.ctx, path, node, newDirNode); err != nil {
		return err
	}

	return outputDagnode(params.out, path, node)
}

func TestAppendSingleBytesToEmpty(t *testing.T) {
	ds := mdtest.Mock()

	data := []byte("AB")

	nd := new(merkledag.Node)
	nd.Data = ft.FilePBData(nil, 0)

	dbp := &h.DagBuilderParams{
		Dagserv:  ds,
		Maxlinks: 4,
	}

	spl := chunk.SizeSplitterGen(500)

	blks, errs := chunk.Chan(spl(bytes.NewReader(data[:1])))

	ctx := context.Background()
	nnode, err := TrickleAppend(ctx, nd, dbp.New(blks, errs))
	if err != nil {
		t.Fatal(err)
	}

	blks, errs = chunk.Chan(spl(bytes.NewReader(data[1:])))

	nnode, err = TrickleAppend(ctx, nnode, dbp.New(blks, errs))
	if err != nil {
		t.Fatal(err)
	}

	fread, err := uio.NewDagReader(ctx, nnode, ds)
	if err != nil {
		t.Fatal(err)
	}

	out, err := ioutil.ReadAll(fread)
	if err != nil {
		t.Fatal(err)
	}

	fmt.Println(out, data)
	err = arrComp(out, data)
	if err != nil {
		t.Fatal(err)
	}
}

// converts the Node object into a real dag.Node
func deserializeNode(node *Node) (*dag.Node, error) {
	dagnode := new(dag.Node)
	dagnode.Data = []byte(node.Data)
	dagnode.Links = make([]*dag.Link, len(node.Links))
	for i, link := range node.Links {
		hash, err := mh.FromB58String(link.Hash)
		if err != nil {
			return nil, err
		}
		dagnode.Links[i] = &dag.Link{
			Name: link.Name,
			Size: link.Size,
			Hash: hash,
		}
	}

	return dagnode, nil
}

func getOutput(dagnode *dag.Node) (*Object, error) {
	key, err := dagnode.Key()
	if err != nil {
		return nil, err
	}

	output := &Object{
		Hash:  key.Pretty(),
		Links: make([]Link, len(dagnode.Links)),
	}

	for i, link := range dagnode.Links {
		output.Links[i] = Link{
			Name: link.Name,
			Hash: link.Hash.B58String(),
			Size: link.Size,
		}
	}

	return output, nil
}

func (p *pinner) unpinLinks(ctx context.Context, node *mdag.Node) error {
	for _, l := range node.Links {
		node, err := l.GetNode(ctx, p.dserv)
		if err != nil {
			return err
		}

		k, err := node.Key()
		if err != nil {
			return err
		}

		p.indirPin.Decrement(k)

		err = p.unpinLinks(ctx, node)
		if err != nil {
			return err
		}
	}
	return nil
}

func insertNodeAtPath(ctx context.Context, ds dag.DAGService, root *dag.Node, path []string, toinsert *dag.Node, create func() *dag.Node) (*dag.Node, error) {
	if len(path) == 1 {
		return addLink(ctx, ds, root, path[0], toinsert)
	}

	nd, err := root.GetLinkedNode(ctx, ds, path[0])
	if err != nil {
		// if 'create' is true, we create directories on the way down as needed
		if err == dag.ErrNotFound && create != nil {
			nd = create()
		} else {
			return nil, err
		}
	}

	ndprime, err := insertNodeAtPath(ctx, ds, nd, path[1:], toinsert, create)
	if err != nil {
		return nil, err
	}

	_ = root.RemoveNodeLink(path[0])
	err = root.AddNodeLinkClean(path[0], ndprime)
	if err != nil {
		return nil, err
	}

	_, err = ds.Add(root)
	if err != nil {
		return nil, err
	}

	return root, nil
}

func addLink(ctx context.Context, ds dag.DAGService, root *dag.Node, childname string, childnd *dag.Node) (*dag.Node, error) {
	if childname == "" {
		return nil, errors.New("cannot create link with no name!")
	}

	// ensure that the node we are adding is in the dagservice
	_, err := ds.Add(childnd)
	if err != nil {
		return nil, err
	}

	// ensure no link with that name already exists
	_ = root.RemoveNodeLink(childname) // ignore error, only option is ErrNotFound

	if err := root.AddNodeLinkClean(childname, childnd); err != nil {
		return nil, err
	}

	if _, err := ds.Add(root); err != nil {
		return nil, err
	}
	return root, nil
}

// Pin the given node, optionally recursive
func (p *pinner) Pin(ctx context.Context, node *mdag.Node, recurse bool) error {
	p.lock.Lock()
	defer p.lock.Unlock()
	k, err := node.Key()
	if err != nil {
		return err
	}

	if recurse {
		if p.recursePin.HasKey(k) {
			return nil
		}

		if p.directPin.HasKey(k) {
			p.directPin.RemoveBlock(k)
		}

		err := p.pinLinks(ctx, node)
		if err != nil {
			return err
		}

		p.recursePin.AddBlock(k)
	} else {
		if _, err := p.dserv.Get(ctx, k); err != nil {
			return err
		}

		if p.recursePin.HasKey(k) {
			return fmt.Errorf("%s already pinned recursively", k.B58String())
		}

		p.directPin.AddBlock(k)
	}
	return nil
}

func setDataCaller(req cmds.Request, root *dag.Node) (key.Key, error) {
	if len(req.Arguments()) < 3 {
		return "", fmt.Errorf("not enough arguments for set-data")
	}

	nd, err := req.InvocContext().GetNode()
	if err != nil {
		return "", err
	}

	root.Data = []byte(req.Arguments()[2])

	newkey, err := nd.DAG.Add(root)
	if err != nil {
		return "", err
	}

	return newkey, nil
}

func rmLink(ctx context.Context, ds dag.DAGService, root *dag.Node, path []string) (*dag.Node, error) {
	if len(path) == 1 {
		// base case, remove node in question
		err := root.RemoveNodeLink(path[0])
		if err != nil {
			return nil, err
		}

		_, err = ds.Add(root)
		if err != nil {
			return nil, err
		}

		return root, nil
	}

	nd, err := root.GetLinkedNode(ctx, ds, path[0])
	if err != nil {
		return nil, err
	}

	nnode, err := rmLink(ctx, ds, nd, path[1:])
	if err != nil {
		return nil, err
	}

	_ = root.RemoveNodeLink(path[0])
	err = root.AddNodeLinkClean(path[0], nnode)
	if err != nil {
		return nil, err
	}

	_, err = ds.Add(root)
	if err != nil {
		return nil, err
	}

	return root, nil
}