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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 */
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