Add virtual tree graphviz printing methods

vt.go

@@ -1,8 +1,15 @@
+// Package arbo > vt.go implements the Virtual Tree, which computes a tree
+// 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 (
 	"bytes"
+	"encoding/hex"
 	"fmt"
+	"io"
 )
 
 type node struct {
@@ -11,7 +18,7 @@ type node struct {
 	k    []byte
 	v    []byte
 	path []bool
-	h    []byte
+	// h    []byte
 }
 
 type params struct {
@@ -177,3 +184,87 @@ func (n *node) downUntilDivergence(p *params, currLvl int, oldLeaf, newLeaf *nod
 func (n *node) computeHashes() ([]kv, error) {
 	return nil, nil
 }
+
+func (t *vt) graphviz(w io.Writer) error {
+	fmt.Fprintf(w, `digraph hierarchy {
+node [fontname=Monospace,fontsize=10,shape=box]
+`)
+	if _, err := t.root.graphviz(w, t.params, 0); err != nil {
+		return err
+	}
+	fmt.Fprintf(w, "}\n")
+	return nil
+}
+
+func (n *node) graphviz(w io.Writer, p *params, nEmpties int) (int, error) {
+	nChars := 4 // TODO move to global constant
+	if n == nil {
+		return nEmpties, nil
+	}
+
+	t := n.typ()
+	switch t {
+	case vtLeaf:
+		leafKey, _, err := newLeafValue(p.hashFunction, n.k, n.v)
+		if err != nil {
+			return nEmpties, err
+		}
+		fmt.Fprintf(w, "\"%p\" [style=filled,label=\"%v\"];\n", n, hex.EncodeToString(leafKey[:nChars]))
+
+		fmt.Fprintf(w, "\"%p\" -> {\"k:%v\\nv:%v\"}\n", n,
+			hex.EncodeToString(n.k[:nChars]),
+			hex.EncodeToString(n.v[:nChars]))
+		fmt.Fprintf(w, "\"k:%v\\nv:%v\" [style=dashed]\n",
+			hex.EncodeToString(n.k[:nChars]),
+			hex.EncodeToString(n.v[:nChars]))
+	case vtMid:
+		fmt.Fprintf(w, "\"%p\" [label=\"\"];\n", n)
+
+		lStr := fmt.Sprintf("%p", n.l)
+		rStr := fmt.Sprintf("%p", n.r)
+		eStr := ""
+		if n.l == nil {
+			lStr = fmt.Sprintf("empty%v", nEmpties)
+			eStr += fmt.Sprintf("\"%v\" [style=dashed,label=0];\n",
+				lStr)
+			nEmpties++
+		}
+		if n.r == nil {
+			rStr = fmt.Sprintf("empty%v", nEmpties)
+			eStr += fmt.Sprintf("\"%v\" [style=dashed,label=0];\n",
+				rStr)
+			nEmpties++
+		}
+		fmt.Fprintf(w, "\"%p\" -> {\"%v\" \"%v\"}\n", n, lStr, rStr)
+		fmt.Fprint(w, eStr)
+		nEmpties, err := n.l.graphviz(w, p, nEmpties)
+		if err != nil {
+			return nEmpties, err
+		}
+		nEmpties, err = n.r.graphviz(w, p, nEmpties)
+		if err != nil {
+			return nEmpties, err
+		}
+
+	case vtEmpty:
+	default:
+		return nEmpties, fmt.Errorf("ERR")
+	}
+
+	return nEmpties, nil
+}
+
+func (t *vt) printGraphviz() error {
+	w := bytes.NewBufferString("")
+	fmt.Fprintf(w,
+		"--------\nGraphviz:\n")
+	err := t.graphviz(w)
+	if err != nil {
+		fmt.Println(w)
+		return err
+	}
+	fmt.Fprintf(w,
+		"End of Graphviz --------\n")
+	fmt.Println(w)
+	return nil
+}