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+#ifndef ENTITY_MANAGER_H_C5832F11
+#define ENTITY_MANAGER_H_C5832F11
+
+#include <map>
+#include <vector>
+#include <typeindex>
+#include <set>
+#include <stdexcept>
+#include "component.h"
+#include "algorithms.h"
+
+class EntityManager {
+private:
+
+  struct EntityData {
+    std::map<std::type_index, std::unique_ptr<Component>> components;
+  };
+
+  using database_type = std::vector<EntityData>;
+
+public:
+
+  using id_type = database_type::size_type;
+
+private:
+
+  database_type entities;
+  std::vector<bool> slotAvailable;
+  std::map<std::set<std::type_index>, std::set<id_type>> cachedComponents;
+
+  id_type nextEntityID = 0;
+
+  template <class T, class... R>
+  std::set<id_type> getEntitiesWithComponentsHelper(
+    std::set<std::type_index>& componentTypes)
+  {
+    componentTypes.insert(typeid(T));
+
+    return getEntitiesWithComponents<R...>(componentTypes);
+  }
+
+  template <class... R>
+  std::set<id_type> getEntitiesWithComponents(
+    std::set<std::type_index>& componentTypes)
+  {
+    return getEntitiesWithComponentsHelper<R...>(componentTypes);
+  }
+
+public:
+
+  EntityManager() = default;
+
+  EntityManager(const EntityManager& copy) = delete;
+
+  id_type emplaceEntity()
+  {
+    if (nextEntityID >= entities.size())
+    {
+      // If the database is saturated, add a new element for the new entity.
+      entities.emplace_back();
+      slotAvailable.push_back(false);
+
+      return nextEntityID++;
+    } else {
+      // If there is an available slot in the database, use it.
+      id_type id = nextEntityID++;
+      slotAvailable[id] = false;
+
+      // Fast forward the next available slot pointer to an available slot.
+      while ((nextEntityID < entities.size()) && !slotAvailable[nextEntityID])
+      {
+        nextEntityID++;
+      }
+
+      return id;
+    }
+  }
+
+  void deleteEntity(id_type entity)
+  {
+    if ((entity >= entities.size()) || slotAvailable[entity])
+    {
+      throw std::invalid_argument("Cannot delete non-existent entity");
+    }
+
+    // Uncache components
+    for (auto& cache : cachedComponents)
+    {
+      cache.second.erase(entity);
+    }
+
+    // Destroy the data
+    entities[entity].components.clear();
+
+    // Mark the slot as available
+    slotAvailable[entity] = true;
+
+    if (entity < nextEntityID)
+    {
+      nextEntityID = entity;
+    }
+  }
+
+  template <class T, class... Args>
+  T& emplaceComponent(id_type entity, Args&&... args)
+  {
+    if ((entity >= entities.size()) || slotAvailable[entity])
+    {
+      throw std::invalid_argument("Cannot delete non-existent entity");
+    }
+
+    EntityData& data = entities[entity];
+    std::type_index componentType = typeid(T);
+
+    if (data.components.count(componentType))
+    {
+      throw std::invalid_argument("Cannot emplace already-existent component");
+    }
+
+    // Initialize the component
+    std::unique_ptr<T> ptr(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<id_type>>& cache) {
+          return cache.first.count(componentType) == 1;
+        });
+
+    return component;
+  }
+
+  template <class T>
+  void removeComponent(id_type entity)
+  {
+    if ((entity >= entities.size()) || slotAvailable[entity])
+    {
+      throw std::invalid_argument("Cannot delete non-existent entity");
+    }
+
+    EntityData& data = entities[entity];
+    std::type_index componentType = typeid(T);
+
+    if (!data.components.count(componentType))
+    {
+      throw std::invalid_argument("Cannot delete non-existent component");
+    }
+
+    // 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(id_type entity)
+  {
+    if ((entity >= entities.size()) || slotAvailable[entity])
+    {
+      throw std::invalid_argument("Cannot delete non-existent entity");
+    }
+
+    EntityData& data = entities[entity];
+    std::type_index componentType = typeid(T);
+
+    if (!data.components.count(componentType))
+    {
+      throw std::invalid_argument("Cannot get non-existent component");
+    }
+
+    return *dynamic_cast<T*>(data.components[componentType].get());
+  }
+
+  template <class... R>
+  std::set<id_type> getEntitiesWithComponents()
+  {
+    std::set<std::type_index> componentTypes;
+
+    return getEntitiesWithComponentsHelper<R...>(componentTypes);
+  }
+};
+
+template <>
+std::set<EntityManager::id_type> EntityManager::getEntitiesWithComponents<>(
+  std::set<std::type_index>& componentTypes);
+
+#endif /* end of include guard: ENTITY_MANAGER_H_C5832F11 */