Made progress on the design for mutability

The work is now almost fully reflective, and *drumroll* the original order of the data is maintained when re-rendering. new elements pop in at the top of the object, but everything else will remain in the sequence it was originally added.

datamodel/low/reference.go

@@ -26,6 +26,11 @@ type HasValueNode[T any] interface {
 	*T
 }
 
+// HasValueNodeUntyped is implemented by NodeReference and ValueReference to return the yaml.Node backing the value.
+type HasValueNodeUntyped interface {
+	GetValueNode() *yaml.Node
+}
+
 // Hashable defines any struct that implements a Hash function that returns a 256SHA hash of the state of the
 // representative object. Great for equality checking!
 type Hashable interface {
@@ -39,6 +44,13 @@ type HasExtensions[T any] interface {
 	GetExtensions() map[KeyReference[string]]ValueReference[any]
 }
 
+// HasExtensionsUntyped is implemented by any object that exposes extensions
+type HasExtensionsUntyped interface {
+
+	// GetExtensions returns generic low level extensions
+	GetExtensions() map[KeyReference[string]]ValueReference[any]
+}
+
 // HasValue is implemented by NodeReference and ValueReference to return the yaml.Node backing the value.
 type HasValue[T any] interface {
 	GetValue() T
@@ -101,6 +113,15 @@ func (n NodeReference[T]) IsEmpty() bool {
 	return n.KeyNode == nil && n.ValueNode == nil
 }
 
+func (n NodeReference[T]) NodeLineNumber() int {
+	if !n.IsEmpty() {
+		return n.ValueNode.Line
+	} else {
+		return 0
+	}
+}
+
+// IsReferenceNode will return true if the key node contains a $ref key.
 func (n NodeReference[T]) IsReferenceNode() bool {
 	if n.KeyNode != nil {
 		for k := range n.KeyNode.Content {
@@ -142,6 +163,15 @@ func (n ValueReference[T]) IsEmpty() bool {
 	return n.ValueNode == nil
 }
 
+// NodeLineNumber will return the line number of the value node (or 0 if the value node is empty)
+func (n ValueReference[T]) NodeLineNumber() int {
+	if !n.IsEmpty() {
+		return n.ValueNode.Line
+	} else {
+		return 0
+	}
+}
+
 // GenerateMapKey will return a string based on the line and column number of the node, e.g. 33:56 for line 33, col 56.
 func (n ValueReference[T]) GenerateMapKey() string {
 	return fmt.Sprintf("%d:%d", n.ValueNode.Line, n.ValueNode.Column)