Add computeHashes at virtual tree

vt.go

@@ -2,7 +2,6 @@
 // without computing any hash. With the idea of once all the leafs are placed in
 // their positions, the hashes can be computed, avoiding computing a node hash
 // more than one time.
-//nolint:unused,deadcode
 package arbo
 
 import (
@@ -18,7 +17,7 @@ type node struct {
 	k    []byte
 	v    []byte
 	path []bool
-	// h    []byte
+	h    []byte
 }
 
 type params struct {
@@ -60,6 +59,18 @@ func (t *vt) add(k, v []byte) error {
 	return nil
 }
 
+// computeHashes should be called after all the vt.add is used, once all the
+// leafs are in the tree
+func (t *vt) computeHashes() ([][2][]byte, error) {
+	var pairs [][2][]byte
+	var err error
+	pairs, err = t.root.computeHashes(t.params, pairs)
+	if err != nil {
+		return pairs, err
+	}
+	return pairs, nil
+}
+
 func newLeafNode(p *params, k, v []byte) *node {
 	keyPath := make([]byte, p.hashFunction.Len())
 	copy(keyPath[:], k)
@@ -150,10 +161,8 @@ func (n *node) downUntilDivergence(p *params, currLvl int, oldLeaf, newLeaf *nod
 		return fmt.Errorf("max virtual level %d", currLvl)
 	}
 
-	// if oldLeaf.path[currLvl+1] != newLeaf.path[currLvl+1] {
 	if oldLeaf.path[currLvl] != newLeaf.path[currLvl] {
 		// reached divergence in next level
-		// if newLeaf.path[currLvl+1] {
 		if newLeaf.path[currLvl] {
 			n.l = oldLeaf
 			n.r = newLeaf
@@ -181,10 +190,60 @@ func (n *node) downUntilDivergence(p *params, currLvl int, oldLeaf, newLeaf *nod
 	return nil
 }
 
-func (n *node) computeHashes() ([]kv, error) {
-	return nil, nil
+// returns an array of key-values to store in the db
+func (n *node) computeHashes(p *params, pairs [][2][]byte) ([][2][]byte, error) {
+	if pairs == nil {
+		pairs = [][2][]byte{}
+	}
+	var err error
+	t := n.typ()
+	switch t {
+	case vtLeaf:
+		leafKey, leafValue, err := newLeafValue(p.hashFunction, n.k, n.v)
+		if err != nil {
+			return pairs, err
+		}
+		n.h = leafKey
+		kv := [2][]byte{leafKey, leafValue}
+		pairs = append(pairs, kv)
+	case vtMid:
+		if n.l != nil {
+			pairs, err = n.l.computeHashes(p, pairs)
+			if err != nil {
+				return pairs, err
+			}
+		} else {
+			n.l = &node{
+				h: p.emptyHash,
+			}
+		}
+		if n.r != nil {
+			pairs, err = n.r.computeHashes(p, pairs)
+			if err != nil {
+				return pairs, err
+			}
+		} else {
+			n.r = &node{
+				h: p.emptyHash,
+			}
+		}
+		// once the sub nodes are computed, can compute the current node
+		// hash
+		k, v, err := newIntermediate(p.hashFunction, n.l.h, n.r.h)
+		if err != nil {
+			return nil, err
+		}
+		n.h = k
+		kv := [2][]byte{k, v}
+		pairs = append(pairs, kv)
+	default:
+		return nil, fmt.Errorf("ERR TMP") // TODO
+	}
+
+	return pairs, nil
 }
 
+//nolint:unused
 func (t *vt) graphviz(w io.Writer) error {
 	fmt.Fprintf(w, `digraph hierarchy {
 node [fontname=Monospace,fontsize=10,shape=box]
@@ -196,6 +255,7 @@ node [fontname=Monospace,fontsize=10,shape=box]
 	return nil
 }
 
+//nolint:unused
 func (n *node) graphviz(w io.Writer, p *params, nEmpties int) (int, error) {
 	nChars := 4 // TODO move to global constant
 	if n == nil {
@@ -254,6 +314,7 @@ func (n *node) graphviz(w io.Writer, p *params, nEmpties int) (int, error) {
 	return nEmpties, nil
 }
 
+//nolint:unused
 func (t *vt) printGraphviz() error {
 	w := bytes.NewBufferString("")
 	fmt.Fprintf(w,