From a5a92ad7959b232ff30421ed1e395e56a069897d Mon Sep 17 00:00:00 2001
From: JacksonCampolattaro <jackcamp@vt.edu>
Date: Tue, 11 Apr 2023 12:17:32 +0200
Subject: [PATCH] Traversal is now done by index (internally)

---
 Orthtree/include/CGAL/Orthtree.h              | 18 ++++++++---
 .../CGAL/Orthtree/Traversal_iterator.h        | 32 ++++++++++++-------
 2 files changed, 33 insertions(+), 17 deletions(-)

diff --git a/Orthtree/include/CGAL/Orthtree.h b/Orthtree/include/CGAL/Orthtree.h
index 8ccb5155a63..77423037461 100644
--- a/Orthtree/include/CGAL/Orthtree.h
+++ b/Orthtree/include/CGAL/Orthtree.h
@@ -123,7 +123,7 @@ public:
 #ifdef DOXYGEN_RUNNING
   typedef unspecified_type Node_range;
 #else
-  typedef boost::iterator_range<Traversal_iterator<const Node>> Node_range;
+  typedef boost::iterator_range<Traversal_iterator<Self>> Node_range;
 #endif
 
   /// \cond SKIP_IN_MANUAL
@@ -449,6 +449,12 @@ public:
     return std::distance(m_nodes.data(), &node);
   }
 
+  boost::optional<std::size_t> index(const Node* node) const {
+    if (node == nullptr) return {};
+    return index(*node);
+  }
+
+
   const Node& operator[](std::size_t index) const {
     return m_nodes[index];
   }
@@ -480,12 +486,14 @@ public:
 
     const Node* first = traversal.first();
 
-    Node_traversal_method_const next = [=](const Node* n) -> const Node* {
-      return traversal.next(n);
+    auto next = [=](const Self& tree, std::size_t index) -> boost::optional<std::size_t> {
+      auto n = traversal.next(&tree[index]);
+      if (n == nullptr) return {};
+      return tree.index(*n);
     };
 
-    return boost::make_iterator_range(Traversal_iterator<const Node>(first, next),
-                                      Traversal_iterator<const Node>());
+    return boost::make_iterator_range(Traversal_iterator<Self>(*this, first, next),
+                                      Traversal_iterator<Self>());
   }
 
   // todo: document this convenience function
diff --git a/Orthtree/include/CGAL/Orthtree/Traversal_iterator.h b/Orthtree/include/CGAL/Orthtree/Traversal_iterator.h
index d69783260b7..ba0e0f78f0a 100644
--- a/Orthtree/include/CGAL/Orthtree/Traversal_iterator.h
+++ b/Orthtree/include/CGAL/Orthtree/Traversal_iterator.h
@@ -15,6 +15,7 @@
 #include <CGAL/license/Orthtree.h>
 
 #include <boost/function.hpp>
+#include <boost/optional.hpp>
 #include <boost/iterator/iterator_facade.hpp>
 
 /// \cond SKIP_IN_MANUAL
@@ -30,9 +31,9 @@ namespace CGAL {
  *
  * \tparam Value
  */
-template <class Value>
+template <class Tree>
 class Traversal_iterator
-  : public boost::iterator_facade<Traversal_iterator<Value>, Value, boost::forward_traversal_tag> {
+  : public boost::iterator_facade<Traversal_iterator<Tree>, const typename Tree::Node, boost::forward_traversal_tag> {
 public:
 
   /// \name Types
@@ -43,7 +44,7 @@ public:
    *
    * \todo
    */
-  typedef std::function<Value*(Value*)> Traversal_function;
+  typedef std::function<boost::optional<std::size_t>(const Tree&, std::size_t)> Traversal_function;
 
   /// @}
 
@@ -53,43 +54,50 @@ public:
   /// @{
 
   /*!
-   * \brief
+   * \brief Default constructor, creates an end sentinel
    *
    * \todo
    */
-  Traversal_iterator() : m_value(nullptr), m_next() {}
+  Traversal_iterator() : m_next() {}
 
   /*!
    * \brief
    *
    * \todo
    *
+   * \param tree
    * \param first
    * \param next
    */
-  Traversal_iterator(Value* first, const Traversal_function& next) : m_value(first), m_next(next) {}
+  Traversal_iterator(const Tree& tree, const typename Tree::Node* first, const Traversal_function& next) :
+    m_tree(&tree), m_index(tree.index(first)), m_next(next) {}
 
   /// @}
 
 private:
+
   friend class boost::iterator_core_access;
 
-  bool equal(Traversal_iterator<Value> const& other) const {
-    return m_value == other.m_value;
+  bool equal(Traversal_iterator<Tree> const& other) const {
+    return m_index == other.m_index;
   }
 
   void increment() {
-    m_value = m_next(m_value);
+    // invoking increment on the sentinel is undefined behavior
+    m_index = m_next(*m_tree, m_index.get());
   }
 
-  Value& dereference() const {
-    return *m_value;
+  const typename Tree::Node& dereference() const {
+    return (*m_tree)[m_index.get()];
   }
 
 private:
 
-  Value* m_value;
   Traversal_function m_next;
+
+  boost::optional<std::size_t> m_index = {};
+  const Tree* m_tree = nullptr;
+
 };
 }