pimpl.hpp

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#ifndef MRS_LIB_EXPERIMENTAL_UTILITY_PIMPL_HPP_
#define MRS_LIB_EXPERIMENTAL_UTILITY_PIMPL_HPP_
 
 
#include <cassert>
#include <cstddef>
#include <memory>
#include <stdexcept>
#include <utility>
 
 
namespace mrs_lib
{

  template <typename Interface, typename StorageType = std::unique_ptr<Interface>>
  class Pimpl
  {
  public:
    explicit Pimpl(std::nullptr_t) = delete;

    explicit Pimpl(StorageType impl) : impl_(std::move(impl))
    {
      if (impl_ == nullptr)
      {
        throw std::logic_error("Cannot construct Pimpl from nullptr.");
      }
    }

    template <typename T, typename... Args>
    explicit Pimpl(std::in_place_type_t<T>, Args&&... args) : impl_(std::make_unique<T>(std::forward<Args>(args)...))
    {
    }

    ~Pimpl() = default;

    Pimpl(const Pimpl&) = delete;
    Pimpl& operator=(const Pimpl&) = delete;
    Pimpl(Pimpl&&) = default;
    Pimpl& operator=(Pimpl&&) = default;

    [[nodiscard]] Interface& operator*() noexcept
    {
      assert(impl_ != nullptr);
      return *impl_;
    }

    [[nodiscard]] const Interface& operator*() const noexcept
    {
      assert(impl_ != nullptr);
      return *impl_;
    }

    [[nodiscard]] Interface* operator->() noexcept
    {
      assert(impl_ != nullptr);
      return impl_.get();
    }

    [[nodiscard]] const Interface* operator->() const noexcept
    {
      assert(impl_ != nullptr);
      return impl_.get();
    }

    [[nodiscard]] bool valueless_after_move() const noexcept
    {
      return impl_ == nullptr;
    }
 
  private:
    StorageType impl_;
  };
 
} // namespace mrs_lib
 
 
#endif // MRS_LIB_EXPERIMENTAL_UTILITY_PIMPL_HPP_