Entity.hpp

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// TODO(docs): Add file-level Doxygen header
//   - @file Entity.hpp
//   - @brief Brief description of Entity concept
//   - Overview of the entity-identifier system (index + generation)
//   - Example usage in context of ECS
#pragma once
#include <functional>
 
#include "SD/core/types.hpp"
 
 
namespace sd {
// TODO(docs): Document Entity struct
//   - Explain index vs generation semantics
//   - Describe entity lifecycle (created -> alive -> destroyed -> recycled)
//   - Note about generation preventing use-after-free
//   - Example: Entity e = manager.Create(); // e = {index: 0, generation: 0}
struct Entity {
  U32 index;
  U32 generation;
 
  bool operator==(Entity other) const {
    return index == other.index && generation == other.generation;
  }
  bool operator!=(Entity other) const { return !(*this == other); }
};
} // namespace sd
 
template<>
struct std::hash<sd::Entity> {
  inline std::size_t operator()(sd::Entity e) const noexcept {
    return std::hash<uint32_t>{}(e.index) ^ (std::hash<uint32_t>{}(e.generation) << 1);
  }
};