cpp-stateful-serializer/include/serializer/shared_cache.h

//
//  shared_cache.h
//  serializer
//
//  Created by Sam Jaffe on 3/15/23.
//

#pragma once

#include <memory>
#include <string>

namespace serializer {
class SharedCache {
public:
  using Key = std::string;
  template <typename T> using Record = std::shared_ptr<T const>;

protected:
  struct Impl {
    virtual ~Impl() = default;
  };

private:
  std::unique_ptr<Impl> p_impl = std::make_unique<Impl>();

public:
  SharedCache() = default;

  /**
   * @brief Store an object within this cache, returning a pointer to the
   * cached object. In order to be nullptr-safe, the unspecialized version
   * of this function returns a shared_ptr containing a copy of value.
   * Specialized versions exist in shared_cache.cxx, which actually perform
   * caching.
   * @param key The name of the value, for looking up later
   * @param value The value to store within this cache
   * @return A shared_ptr containing the cached value
   */
  template <typename T> Record<T> store(Key const & key, T const & value) {
    return std::make_shared<T>(value);
  }
  /**
   * @brief Fetch an object that was cached within this object.
   * @param key The name of the cached object, as called in store()
   * @return A shared_ptr containing the requested object, or null if it isn't
   * found in this cache.
   * @throws std::domain_error if no specialization is defined
   */
  template <typename T> Record<T> fetch(Key const & key) const {
    throw std::domain_error(typeid(T).name());
  }

protected:
  template <typename T>
  SharedCache(std::unique_ptr<T> ptr) : p_impl(std::move(ptr)) {}
};
}