Closes #22

core/tree_node.cpp

@@ -10,6 +10,7 @@
  */
 
 #include "tree_node.h"
+#include <stdexcept>
 
 TreeNode::TreeNode()
     : m_type(NodeType::Root), m_name("dbc") {
@@ -23,8 +24,14 @@ TreeNode::TreeNode(const SignalInfo &signal)
     : m_type(NodeType::Signal), m_name(signal.name), m_signal(std::make_unique<SignalInfo>(signal)) {
 }
 
-void TreeNode::AddChild(std::unique_ptr<TreeNode> child) {
+void TreeNode::AddChild(std::unique_ptr<TreeNode> &&child) {
     if (child) {
+        for (const TreeNode *ancestor = this; ancestor; ancestor = ancestor->m_parent) {
+            if (ancestor == child.get())
+                throw std::invalid_argument("Cannot insert a node into its own subtree");
+        }
+        if (child->m_parent)
+            throw std::invalid_argument("Child is already attached");
         m_children.push_back(std::move(child));
         m_children.back()->m_parent = this;
         m_children.back()->m_row = m_children.size() - 1U;
@@ -72,3 +79,18 @@ const TreeNode *TreeNode::GetParent() const {
 std::size_t TreeNode::GetRow() const {
     return m_row;
 }
+
+std::optional<FrameKey> TreeNode::GetFrameKey() const {
+    if (m_frame)
+        return FrameKey(m_frame->canId, m_frame->isExtended);
+    if (m_signal && m_parent && m_parent->GetType() == NodeType::Frame)
+        return m_parent->GetFrameKey();
+    return std::nullopt;
+}
+
+std::optional<SignalKey> TreeNode::GetSignalKey() const {
+    const std::optional<FrameKey> frame = GetFrameKey();
+    if (m_signal && frame)
+        return SignalKey(*frame, m_signal->name);
+    return std::nullopt;
+}

core/tree_node.h

@@ -14,9 +14,11 @@
 
 #include <cstddef>
 #include <memory>
+#include <optional>
 #include <string>
 #include <vector>
 
+#include "definition_key.h"
 #include "frame_info.h"
 #include "signal_info.h"
 
@@ -56,14 +58,19 @@ public:
     TreeNode(const TreeNode &) = delete;
     TreeNode &operator=(const TreeNode &) = delete;
 
+    // Node addresses are stable. Transfer unique_ptr ownership instead of nodes.
     TreeNode(TreeNode &&) = delete;
     TreeNode &operator=(TreeNode &&) = delete;
 
     /**
      * @brief Add child node.
      * @param child Child node to add.
+     * A null child is ignored. Existing children keep their addresses and rows.
+     * Ownership must be exclusive; attached nodes cannot be reparented.
+     * @throws std::invalid_argument for self/ancestor insertion or an attached child.
+     * Rejected ownership remains with the caller.
      */
-    void AddChild(std::unique_ptr<TreeNode> child);
+    void AddChild(std::unique_ptr<TreeNode> &&child);
 
     /** Non-owning parent; nullptr for a detached node or the root. */
     const TreeNode *GetParent() const;
@@ -71,6 +78,12 @@ public:
     /** Zero-based sibling position; zero for a detached node or the root. */
     std::size_t GetRow() const;
 
+    /** Frame identity for frame nodes and signals attached to a frame; otherwise empty. */
+    std::optional<FrameKey> GetFrameKey() const;
+
+    /** Signal identity (owning frame key and name); empty for other/detached nodes. */
+    std::optional<SignalKey> GetSignalKey() const;
+
     /**
      * @brief Get child count.
      * @return Number of children.