implement building system

src/lib/sim/Simulation.h

@@ -1,21 +1,25 @@
 #pragma once
 
+#include <memory>
 #include <random>
 #include <vector>
 
+#include "BeltSystem.h"
+#include "BlueprintDropEvent.h"
 #include "EntityId.h"
 #include "FireEvent.h"
-#include "BlueprintDropEvent.h"
 #include "GameConfig.h"
 #include "Tick.h"
 
+class BuildingSystem;
+
 class Simulation
 {
 public:
     explicit Simulation(const GameConfig& config, unsigned int seed = 0);
+    ~Simulation();
 
     // Advances the simulation by one tick. Tick order per architecture.md §Tick Order.
-    // Currently a stub; subsystems are plugged in across Steps 3-7.
     void tick();
 
     // Returns all fire events accumulated since the last drain, clearing the
@@ -26,6 +30,12 @@ public:
     std::vector<BlueprintDropEvent> drainBlueprintDropEvents();
 
     Tick currentTick() const;
+    int  buildingBlocksStock() const;
+
+    BuildingSystem&       buildings();
+    const BuildingSystem& buildings() const;
+    BeltSystem&           belts();
+    const BeltSystem&     belts() const;
 
 private:
     EntityId allocateId();  // Strictly increasing; never returns kInvalidEntityId.
@@ -33,9 +43,13 @@ private:
     const GameConfig& m_config;
     std::mt19937 m_rng;
 
-    Tick m_currentTick;
-    EntityId m_nextId;  // starts at 1; 0 is kInvalidEntityId.
+    Tick     m_currentTick;
+    EntityId m_nextId;
+    int      m_buildingBlocksStock;
 
-    std::vector<FireEvent> m_fireEvents;
+    BeltSystem                      m_beltSystem;
+    std::unique_ptr<BuildingSystem> m_buildingSystem;
+
+    std::vector<FireEvent>          m_fireEvents;
     std::vector<BlueprintDropEvent> m_blueprintDropEvents;
 };