Add a first version of obitag the successor of ecotag

pkg/obitax/lca.go

@@ -0,0 +1,25 @@
+package obitax
+
+func (t1 *TaxNode) LCA(t2 *TaxNode) (*TaxNode, error) {
+	p1, err1 := t1.Path()
+
+	if err1 != nil {
+		return nil, err1
+	}
+
+	p2, err2 := t2.Path()
+
+	if err2 != nil {
+		return nil, err2
+	}
+
+	i1 := len(*p1) - 1
+	i2 := len(*p2) - 1
+
+	for i1 >= 0 && i2 >= 0 && (*p1)[i1].taxid == (*p2)[i2].taxid {
+		i1--
+		i2--
+	}
+
+	return (*p1)[i1+1], nil
+}