From c32fb24efb16893b35025570ab3bc0c62dfd10e7 Mon Sep 17 00:00:00 2001
From: Jackson Campolattaro <jackcamp@vt.edu>
Date: Thu, 25 Jun 2020 00:10:44 -0400
Subject: [PATCH] Begin implementing depth first traversal

---
 Octree/include/CGAL/Octree.h                  |  4 +--
 .../CGAL/Octree/Tree_walker_criterion.h       | 36 +++++++++++--------
 Octree/test/Octree/test_node_index.cpp        |  3 +-
 3 files changed, 25 insertions(+), 18 deletions(-)

diff --git a/Octree/include/CGAL/Octree.h b/Octree/include/CGAL/Octree.h
index 38013e4f60a..c85fbad429c 100644
--- a/Octree/include/CGAL/Octree.h
+++ b/Octree/include/CGAL/Octree.h
@@ -176,7 +176,7 @@ namespace CGAL {
 
     const Node &root() const { return m_root; }
 
-    void print(std::ostream &os, std::function<Node *(Node *)> tree_walker) {
+    void print(std::ostream &os, std::function<Node *(Node *, Node *)> tree_walker) {
 
       Node *node = &root();
 
@@ -188,7 +188,7 @@ namespace CGAL {
         os << "(" << node->location()[0] << "," << node->location()[1] << "," << node->location()[2] << ") ";
         os << std::endl;
 
-        node = tree_walker(node);
+        node = tree_walker(&root(), node);
       }
     }
 
diff --git a/Octree/include/CGAL/Octree/Tree_walker_criterion.h b/Octree/include/CGAL/Octree/Tree_walker_criterion.h
index ca36730bc0e..dbeca07810a 100644
--- a/Octree/include/CGAL/Octree/Tree_walker_criterion.h
+++ b/Octree/include/CGAL/Octree/Tree_walker_criterion.h
@@ -6,11 +6,11 @@ namespace CGAL {
   struct Siblings {
 
     template<class Node>
-    Node *operator()(Node *n) {
+    Node *operator()(Node *root, Node *n) {
 
-      // Null handler
+      // Passing null returns the first node
       if (nullptr == n)
-        return n;
+        return root;
 
       // If this node has no parent, it has no siblings
       if (nullptr == n->parent())
@@ -31,35 +31,43 @@ namespace CGAL {
   struct Depth_first {
 
     template<class Node>
-    Node *operator()(Node *n) {
+    Node *operator()(Node *root, Node *n) {
 
-      // Null handler
-      if (nullptr == n)
-        return n;
+      // Passing null returns the first node
+      if (nullptr == n) {
 
-      if (n->isLeaf()) {
+        return root;
+        // Find the deepest child on the left
+//        Node *first = root;
+//        while (!first->is_leaf())
+//          first = &(*first)[0];
+//        return first;
+      }
+
+      if (n->is_leaf()) {
+
+        Siblings siblings;
 
         // Check if this node is the last sibling
-        if (false) {
+        if (7 != n->index().to_ulong()) {
 
           // Return the next sibling
+          return (siblings(root, n));
 
         } else {
 
           // Return the next sibling of the parent
-
+          // FIXME: this should be able to search upwards at the last sibling
+          return (siblings(root, n->parent()));
         }
 
 
       } else {
 
         // Return the first child of this node
+        return &(*n)[0];
       }
 
-
-      // TODO: placeholder
-      return n;
-
     }
   };
 }
diff --git a/Octree/test/Octree/test_node_index.cpp b/Octree/test/Octree/test_node_index.cpp
index e11ece0e0eb..f2a0e4446de 100644
--- a/Octree/test/Octree/test_node_index.cpp
+++ b/Octree/test/Octree/test_node_index.cpp
@@ -41,9 +41,8 @@ int main(void) {
   Octree octree(points, point_map);
   octree.refine(10, 1);
 
-  auto treeWalker = CGAL::Siblings();
+  auto treeWalker = CGAL::Depth_first();
   octree.print(std::cout, treeWalker);
-  //std::cout << *treeWalker(&octree.root()[6]);
 
   return 0;
 }