BiMap.hpp

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#pragma once
 
#include <unordered_map>
 
namespace shkyera::common {
 
template <typename First, typename Second, template <typename, typename> class Impl = std::unordered_map>
class BiMap {
 public:
  using ForwardMap = Impl<First, Second>;
  using BackwardMap = Impl<Second, First>;
 
  bool empty() const { return forward.empty(); }
 
  void clear() {
    forward.clear();
    backward.clear();
  }
 
  const Second& at(const First& first) const { return forward.at(first); }
 
  const First& at(const Second& second) const { return backward.at(second); }
 
  void insert(First first, Second second) {
    forward[first] = second;
    backward[second] = first;
  }
 
  void remove(First first) {
    const auto& second = at(first);
    backward.erase(second);
    forward.erase(first);
  }
 
  void remove(Second second) {
    const auto& first = at(second);
    forward.erase(first);
    backward.erase(second);
  }
 
 private:
  ForwardMap forward;
  BackwardMap backward;
};
 
}  // namespace shkyera::common