From 5209e054e59cf1bfb779bedcbf835e59290bb01c Mon Sep 17 00:00:00 2001
From: Jan Mrna <mj370@protonmail.com>
Date: Thu, 16 Oct 2025 18:02:31 +0200
Subject: [PATCH] Positional container WIP

---
 cpp/src/positional_container.hpp   | 172 +++++++++++++++++++++++++++++
 cpp/test/collision_performance.cpp |  24 ++++
 2 files changed, 196 insertions(+)
 create mode 100644 cpp/src/positional_container.hpp

diff --git a/cpp/src/positional_container.hpp b/cpp/src/positional_container.hpp
new file mode 100644
index 0000000..0b4e94d
--- /dev/null
+++ b/cpp/src/positional_container.hpp
@@ -0,0 +1,172 @@
+#pragma once
+
+#include <vector>
+#include <memory>
+#include <cstdlib>
+
+#include "math.hpp"
+#include "log.hpp"
+
+template <typename T>
+concept HasPosition = requires(T t, WorldPos pos) {
+  { t.GetPosition() } -> std::convertible_to<WorldPos>;
+  t.SetPosition(pos);
+};
+
+template <typename T>
+concept HasCollisions = requires(T t) {
+  t.Dummy(); // TODO
+};
+
+template <typename T>
+requires HasPosition<T>
+class IPositionalContainer
+{
+public:
+  virtual ~IPositionalContainer() = default;
+  virtual bool Add(const T& t) = 0;
+  virtual std::vector<std::weak_ptr<T>> Get(const WorldPos& p, float radius) = 0;
+  virtual void UpdateAll() = 0;
+  virtual void Update(std::shared_ptr<T> item) = 0;
+};
+
+
+template <typename T>
+class IColliderContainer : public IPositionalContainer<T>
+{
+public:
+  virtual std::vector<std::weak_ptr<T>> GetCollisions() = 0;
+};
+
+template <typename T>
+class SimpleContainer : IPositionalContainer<T>
+{
+public:
+  bool Add(const T& t) override
+  {
+    m_Items.push_back(std::make_shared<T>(t));
+  }
+  
+  std::vector<std::weak_ptr<T>> Get(const WorldPos& center, float radius) override
+  {
+    std::vector<std::weak_ptr<T>> matched_items;
+    for (const auto& item : m_Items)
+    {
+      const auto& A = item->GetPosition();
+      if (center.DistanceTo(item->GetPosition()) < radius)
+      {
+        matched_items.push_back(item);
+      }
+    }
+    return matched_items;
+  }
+  
+  // no update needed here, as we have no smart lookup scheme
+  void UpdateAll() override {}
+  void Update(std::shared_ptr<T> item) override {}
+
+private:
+  std::vector<std::shared_ptr<T>> m_Items;
+};
+
+
+template <class T>
+class PositionalContainer : IPositionalContainer<T>
+{
+public:
+
+  PositionalContainer(const WorldSize& size, size_t chunks) :
+    m_GridSize{size},
+    m_GridStep{size / chunks},
+    m_ChunksPerAxis{chunks}
+  {
+    LOG_INFO("Size: ", m_GridSize, " step: ", m_GridStep);
+    m_Grid.reserve(chunks);
+    for (size_t i = 0; i < chunks; i++)
+    {
+      //m_Grid.push_back(std::vector<vector_wptr>{chunks});
+      m_Grid.emplace_back(chunks);
+      for (size_t j = 0; j < chunks; j++)
+      {
+        // let's try reserving place for 16 items
+        m_Grid[i][j].reserve(16);
+      }
+    }
+  }
+
+  // calling Add on object that is already in the container is UB
+  bool Add(const T& item) override
+  {
+    const auto& world_pos = item.GetPosition();
+    if (!CheckBounds(world_pos))
+    {
+      return false;
+    }
+    auto ptr = std::make_shared<T>(item);
+    m_Items.push_back(ptr);
+    auto coords = GetCoords(world_pos);
+    // here we assume that the object is not already in the grid!
+    m_Grid[coords.x()][coords.y()].push_back(ptr);
+
+    // TODO should we call Update instead?
+    //Update(ptr);
+  }
+  
+  std::vector<std::weak_ptr<T>> Get(const WorldPos& center, float radius) override
+  {
+    return vector_wptr{};
+  }
+
+  void Get(std::vector<std::weak_ptr<T>>& output_vec, const WorldPos& center, float radius)
+  {
+
+  }
+
+  void UpdateAll() override
+  {
+    for (auto ptr : m_Items)
+    {
+      // TODO is this efficient? Maybe use const ref?
+      Update(ptr);
+    }
+  }
+  void Update(std::shared_ptr<T> item) override
+  {
+    auto coords = GetCoords(item->GetPosition());
+    // remove the old weak ptr from the map
+    
+    // add new weak ptr to the map
+    m_Grid[coords.x()][coords.y()].push_back(item);
+  }
+
+private:
+  
+  using coord_type = vec<size_t, 2>;
+  using vector_wptr = std::vector<std::weak_ptr<T>>;
+  using grid_type = std::vector<std::vector<vector_wptr>>;
+
+  coord_type GetCoords(const WorldPos &wp)
+  {
+    auto coord_float = wp / m_ChunksPerAxis;
+    return coord_type{
+      static_cast<size_t>(coord_float.x()),
+      static_cast<size_t>(coord_float.y())
+    };
+  }
+
+  bool CheckBounds(const WorldPos& pos)
+  {
+    auto [x,y] = pos;
+    bool x_in_bounds = 0.0f < x && x < m_GridSize.x(); 
+    bool y_in_bounds = 0.0f < y && y < m_GridSize.y(); 
+    return x_in_bounds && y_in_bounds;
+  }
+
+  WorldSize m_GridSize;
+  WorldSize m_GridStep;
+  size_t m_ChunksPerAxis;
+  std::vector<std::shared_ptr<T>> m_Items;
+  
+
+  grid_type m_Grid;
+};
diff --git a/cpp/test/collision_performance.cpp b/cpp/test/collision_performance.cpp
index 3860f9f..3db6c73 100644
--- a/cpp/test/collision_performance.cpp
+++ b/cpp/test/collision_performance.cpp
@@ -3,6 +3,9 @@
 #include <iostream>
 #include <iomanip>
 
+
+#include "positional_container.hpp"
+
 // TODO: Add necessary includes for collision testing
 // #include "collision_shapes.hpp"
 // #include "entities.hpp"
@@ -74,8 +77,29 @@ void benchmark_function(const std::string& name, int iterations, Func func) {
               << " ops/sec" << std::endl;
 }
 
+/**
+ * @brief Simple dummy class that conforms to HasPosition concept
+ * Used for testing PositionalContainer without heavy dependencies
+ */
+class Dummy {
+public:
+    Dummy() : m_Position(0.0f, 0.0f) {}
+    Dummy(float x, float y) : m_Position(x, y) {}
+    Dummy(WorldPos pos) : m_Position(pos) {}
+    
+    WorldPos GetPosition() const { return m_Position; }
+    void SetPosition(WorldPos pos) { m_Position = pos; }
+    
+private:
+    WorldPos m_Position;
+};
+
 // Example test function 1
 void test_function_1() {
+  
+    PositionalContainer<Dummy> pos_cont{WorldSize{10.0f, 10.0f}, 10}; 
+    SimpleContainer<Dummy> simp_cont; 
+
     // TODO: Implement actual collision test
     volatile int sum = 0;
     for (int i = 0; i < 1000; ++i) {