feat: add Children and ChildNodes methods

Author: rmkane

node.go

@@ -142,6 +142,42 @@ func (n *Node) InnerText() string {
 	return b.String()
 }
 
+// IsElementLike returns true if the node type supports child nodes.
+func (n *Node) IsElementLike() bool {
+	switch n.Type {
+	case ElementNode, DocumentNode, DeclarationNode:
+		return true
+	default:
+		return false
+	}
+}
+
+// Children returns a slice of all direct child nodes of the current node.
+// This includes all node types that are children, without filtering.
+func (n *Node) Children() []*Node {
+	var children []*Node
+	for child := n.FirstChild; child != nil; child = child.NextSibling {
+		children = append(children, child)
+	}
+	return children
+}
+
+// ChildNodes returns a slice of all direct child nodes of the current node (excluding attributes, text, comments, and char data).
+// Returns an error if the node type does not support child nodes.
+func (n *Node) ChildNodes() ([]*Node, error) {
+	if !n.IsElementLike() {
+		return nil, fmt.Errorf("node type %v does not support child nodes", n.Type)
+	}
+
+	var children []*Node
+	for child := n.FirstChild; child != nil; child = child.NextSibling {
+		if child.IsElementLike() {
+			children = append(children, child)
+		}
+	}
+	return children, nil
+}
+
 func (n *Node) sanitizedData(preserveSpaces bool) string {
 	if preserveSpaces {
 		return n.Data

node_test.go

@@ -117,6 +117,44 @@ func verifyNodePointers(t *testing.T, n *Node) {
 	testTrue(t, parent == nil || parent.LastChild == cur)
 }
 
+func TestChildren(t *testing.T) {
+	t.Run("Has 3 children", func(t *testing.T) {
+		node := &Node{Type: ElementNode}
+
+		AddChild(node, &Node{Type: CommentNode})
+		AddChild(node, &Node{Type: ElementNode})
+		AddChild(node, &Node{Type: TextNode})
+
+		children := node.Children()
+
+		testTrue(t, len(children) == 3)
+	})
+}
+
+func TestChildNodes(t *testing.T) {
+	t.Run("Has 1 child node", func(t *testing.T) {
+		node := &Node{Type: ElementNode}
+
+		AddChild(node, &Node{Type: CommentNode})
+		AddChild(node, &Node{Type: ElementNode})
+		AddChild(node, &Node{Type: TextNode})
+
+		children, err := node.ChildNodes()
+
+		testTrue(t, err == nil)
+		testTrue(t, len(children) == 1)
+	})
+
+	t.Run("Cannot have child nodes", func(t *testing.T) {
+		node := &Node{Type: CommentNode}
+
+		children, err := node.ChildNodes()
+
+		testTrue(t, children == nil)
+		testTrue(t, err != nil)
+	})
+}
+
 func TestAddAttr(t *testing.T) {
 	for _, test := range []struct {
 		name     string
@@ -232,6 +270,59 @@ func TestRemoveAttr(t *testing.T) {
 	}
 }
 
+func TestIsElementLike(t *testing.T) {
+	for _, test := range []struct {
+		name     string
+		n        *Node
+		expected bool
+	}{
+		{
+			name:     "DocumentNode can have children",
+			n:        &Node{Type: DocumentNode},
+			expected: true,
+		},
+		{
+			name:     "DeclarationNode can have children",
+			n:        &Node{Type: DeclarationNode},
+			expected: true,
+		},
+		{
+			name:     "ElementNode can have children",
+			n:        &Node{Type: ElementNode},
+			expected: true,
+		},
+		{
+			name:     "TextNode cannot have children",
+			n:        &Node{Type: TextNode},
+			expected: false,
+		},
+		{
+			name:     "CharDataNode cannot have children",
+			n:        &Node{Type: CharDataNode},
+			expected: false,
+		},
+		{
+			name:     "CommentNode cannot have children",
+			n:        &Node{Type: CommentNode},
+			expected: false,
+		},
+		{
+			name:     "AttributeNode cannot have children",
+			n:        &Node{Type: AttributeNode},
+			expected: false,
+		},
+		{
+			name:     "NotationNode cannot have children",
+			n:        &Node{Type: NotationNode},
+			expected: false,
+		},
+	} {
+		t.Run(test.name, func(t *testing.T) {
+			testValue(t, test.n.IsElementLike(), test.expected)
+		})
+	}
+}
+
 func TestRemoveFromTree(t *testing.T) {
 	xml := `<?procinst?>
 		<!--comment-->