1 files changed, 152 insertions, 0 deletions

@@ -0,0 +1,152 @@
+#ifndef ENTITY_MANAGER_H_C5832F11
+#define ENTITY_MANAGER_H_C5832F11
+
+#include <map>
+#include <typeindex>
+#include <set>
+#include <cassert>
+#include "component.h"
+#include "algorithms.h"
+
+class EntityManager {
+  private:
+    struct EntityData {
+      std::map<std::type_index, std::unique_ptr<Component>> components;
+    };
+  
+    std::map<int, EntityData> entities;
+    std::map<std::set<std::type_index>, std::set<int>> cachedComponents;
+  
+    int nextEntityID = 0;
+    
+    template <class T, class... R>
+    std::set<int> getEntitiesWithComponentsHelper(std::set<std::type_index>& componentTypes)
+    {
+      componentTypes.insert(typeid(T));
+      
+      return getEntitiesWithComponents<R...>(componentTypes);
+    }
+    
+    template <class... R>
+    std::set<int> getEntitiesWithComponents(std::set<std::type_index>& componentTypes)
+    {
+      return getEntitiesWithComponentsHelper<R...>(componentTypes);
+    }
+    
+  public:
+    EntityManager() = default;
+    EntityManager(const EntityManager& copy) = delete;
+    
+    int emplaceEntity()
+    {
+      // Find a suitable entity ID
+      while ((entities.count(nextEntityID) == 1) && (nextEntityID >= 0))
+      {
+        nextEntityID++;
+      }
+        
+      if (nextEntityID < 0)
+      {
+        nextEntityID = 0;
+        
+        while ((entities.count(nextEntityID) == 1) && (nextEntityID >= 0))
+        {
+          nextEntityID++;
+        }
+        
+        assert(nextEntityID >= 0);
+      }
+      
+      // Initialize the data
+      int id = nextEntityID++;
+      entities[id];
+      
+      return id;
+    }
+    
+    void deleteEntity(int entity)
+    {
+      assert(entities.count(entity) == 1);
+      
+      // Uncache components
+      for (auto& cache : cachedComponents)
+      {
+        cache.second.erase(entity);
+      }
+      
+      // Destroy the data
+      entities.erase(entity);
+    }
+    
+    template <class T, class... Args>
+    T& emplaceComponent(int entity, Args&&... args)
+    {
+      assert(entities.count(entity) == 1);
+      
+      EntityData& data = entities[entity];
+      std::type_index componentType = typeid(T);
+      
+      assert(data.components.count(componentType) == 0);
+      
+      // Initialize the component
+      std::unique_ptr<T> ptr = std::unique_ptr<T>(new T(std::forward<Args>(args)...));
+      T& component = *ptr;
+      data.components[componentType] = std::move(ptr);
+      
+      // Invalidate related caches
+      erase_if(cachedComponents, [&componentType] (std::pair<const std::set<std::type_index>, std::set<int>>& cache) {
+        return cache.first.count(componentType) == 1;
+      });
+      
+      return component;
+    }
+    
+    template <class T>
+    void removeComponent(int entity)
+    {
+      assert(entities.count(entity) == 1);
+      
+      EntityData& data = entities[entity];
+      std::type_index componentType = typeid(T);
+      
+      assert(data.components.count(componentType) == 1);
+      
+      // Destroy the component
+      data.components.erase(componentType);
+      
+      // Uncache the component
+      for (auto& cache : cachedComponents)
+      {
+        if (cache.first.count(componentType) == 1)
+        {
+          cache.second.erase(entity);
+        }
+      }
+    }
+    
+    template <class T>
+    T& getComponent(int entity)
+    {
+      assert(entities.count(entity) == 1);
+      
+      EntityData& data = entities[entity];
+      std::type_index componentType = typeid(T);
+      
+      assert(data.components.count(componentType) == 1);
+      
+      return *((T*)data.components[componentType].get());
+    }
+    
+    template <class... R>
+    std::set<int> getEntitiesWithComponents()
+    {
+      std::set<std::type_index> componentTypes;
+      
+      return getEntitiesWithComponentsHelper<R...>(componentTypes);
+    }
+};
+
+template <>
+std::set<int> EntityManager::getEntitiesWithComponents<>(std::set<std::type_index>& componentTypes);
+
+#endif /* end of include guard: ENTITY_MANAGER_H_C5832F11 */