module.hpp

#ifndef LIBSBX_CORE_MODULE_HPP_
#define LIBSBX_CORE_MODULE_HPP_
 
#include <type_traits>
#include <unordered_set>
#include <unordered_map>
#include <typeindex>
#include <functional>
#include <memory>
#include <cinttypes>
#include <cmath>
 
#include <libsbx/utility/noncopyable.hpp>
 
namespace sbx::core {
 
template<typename Derived, typename Base>
concept derived_from = std::is_base_of_v<Base, Derived>;
 
class module_manager {
 
  template<typename>
  friend class module;
 
  friend class engine;
 
public:
 
  module_manager() = delete;
  
  ~module_manager() = default;
 
private:
 
  enum class stage : std::uint8_t {
    pre,
    normal,
    post,
    fixed,
    rendering,
  }; // enum class stage
 
  template<typename... Types>
  struct dependencies {
    auto get() const noexcept -> std::unordered_set<std::type_index> {
      auto types = std::unordered_set<std::type_index>{};
      (types.insert(std::type_index{typeid(Types)}), ...);
      return types;
    }
  }; // struct dependencies
 
  struct module_base {
    virtual ~module_base() = default;
    virtual auto update() -> void = 0;
  }; // struct module_base
 
  struct module_factory {
    module_manager::stage stage{};
    std::unordered_set<std::type_index> dependencies{};
    std::function<module_base*()> create{};
    std::function<void(module_base*)> destroy{};
  }; // module_factory
 
  static auto _factories() -> std::unordered_map<std::type_index, module_factory>& {
    static auto instance = std::unordered_map<std::type_index, module_factory>{};
    return instance;
  }
 
}; // class module_manager
 
template<typename Derived>
class module : public module_manager::module_base, public utility::noncopyable {
 
public:
 
  virtual ~module() {
    static_assert(!std::is_abstract_v<Derived>, "Class may not be abstract.");
    static_assert(std::is_base_of_v<module<Derived>, Derived>, "Class must inherit from module<Class>.");
  }
 
protected:
 
  using base_type = module_manager::module_base;
 
  template<typename... Dependencies>
  using dependencies = module_manager::dependencies<Dependencies...>;
 
  using stage = module_manager::stage;
 
  template<derived_from<base_type>... Dependencies>
  static auto register_module(stage stage, dependencies<Dependencies...>&& dependencies = {}) -> bool {
    module_manager::_factories().insert({std::type_index{typeid(Derived)}, module_manager::module_factory{
      .stage = stage,
      .dependencies = dependencies.get(),
      .create = [](){
        auto* instance = reinterpret_cast<Derived*>(std::malloc(sizeof(Derived)));
 
        if (!instance) {
          throw std::bad_alloc{};
        }
 
        std::construct_at(instance);
 
        return instance;
      },
      .destroy = [](module_base* instance){
        std::destroy_at(reinterpret_cast<Derived*>(instance));
        std::free(instance);
      }
    }});
 
    return true;
  }
 
}; // class module
 
} // namespace sbx::core
 
#endif // LIBSBX_CORE_MODULE_HPP_