implement GetNode on mapblock

mapblock.go

@@ -1,5 +1,7 @@
 package types
 
+import "fmt"
+
 type MapBlock struct {
 	Size         int            `json:"size"`
 	Version      byte           `json:"version"`
@@ -35,3 +37,18 @@ func (mb *MapBlock) GetNodeName(p *Pos) string {
 	id := mb.GetNodeId(p)
 	return mb.BlockMapping[id]
 }
+
+func (mb *MapBlock) GetNode(p *Pos) (*Node, error) {
+	i := p.Index()
+
+	if i > len(mb.Mapdata.ContentId) {
+		return nil, fmt.Errorf("unexpected index, got %d, len: %d, pos: %s", i, len(mb.Mapdata.ContentId), p)
+	}
+
+	return &Node{
+		Pos:    p,
+		Name:   mb.BlockMapping[mb.Mapdata.ContentId[i]],
+		Param1: mb.Mapdata.Param1[i],
+		Param2: mb.Mapdata.Param2[i],
+	}, nil
+}