Add bounded sources and strict YAML parsing

internal/document/document.go

@@ -0,0 +1,62 @@
+// Package document defines ConfigKit's parser-independent configuration tree.
+package document
+
+// Kind identifies a configuration node category.
+type Kind uint8
+
+const (
+	Mapping Kind = iota + 1
+	Sequence
+	String
+	Boolean
+	Number
+	Null
+)
+
+// Location identifies a source coordinate. Root depth and unavailable coordinates
+// are represented independently by callers; line and column are one-based when set.
+type Location struct {
+	SourceID string
+	Line     int
+	Column   int
+}
+
+// Entry is an ordered mapping entry with separate key and value locations.
+type Entry struct {
+	Key           string
+	KeyLocation   Location
+	ValueLocation Location
+	Value         *Node
+}
+
+// Node is ConfigKit's owned configuration representation. Number Text retains its
+// exact validated decimal spelling; Boolean Text is "true" or "false".
+type Node struct {
+	Kind     Kind
+	Location Location
+	Text     string
+	Mapping  []Entry
+	Sequence []*Node
+}
+
+// Clone returns a detached copy of a node tree.
+func Clone(node *Node) *Node {
+	if node == nil {
+		return nil
+	}
+	cloned := *node
+	if node.Mapping != nil {
+		cloned.Mapping = make([]Entry, len(node.Mapping))
+		for i, entry := range node.Mapping {
+			cloned.Mapping[i] = entry
+			cloned.Mapping[i].Value = Clone(entry.Value)
+		}
+	}
+	if node.Sequence != nil {
+		cloned.Sequence = make([]*Node, len(node.Sequence))
+		for i, child := range node.Sequence {
+			cloned.Sequence[i] = Clone(child)
+		}
+	}
+	return &cloned
+}