Added node type

internal/tree/node.go

@@ -0,0 +1,39 @@
+package tree
+
+// Node is a struct containing nodes of a file tree.
+type Node struct {
+	// can be nil
+	Parent   *Node
+	Name     string
+	FileType string
+	// cannot be nil; may have len 0
+	Children []*Node
+}
+
+// NewNode constructs and returns a Node instance.
+// parent and children are optional and can be nil,
+// in which case Parent will be stored as nil,
+// but Children will be initialized as []*Node of len 0.
+func NewNode(name string, ft string, parent *Node, children []*Node) *Node {
+	var c []*Node
+	if children == nil {
+		c = make([]*Node, 0)
+	} else {
+		c = children
+	}
+	n := &Node{
+		Name:     name,
+		FileType: ft,
+		Parent:   parent,
+		Children: c,
+	}
+	return n
+}
+
+func (n *Node) IsRoot() bool {
+	return n.Parent == nil
+}
+
+func (n *Node) IsTail() bool {
+	return len(n.Children) == 0
+}