Strategy.hpp

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#pragma once
 
#include "utils/Invariant.hpp"
#include "utils/Types.hpp"
 
#include <map>
#include <memory>
#include <optional>
#include <set>
#include <stdexcept>
#include <string>
 
#include <nlohmann/json.hpp>
 
namespace ppforest2::strategies {
  inline std::map<std::string, std::string>& primary_params_registry() {
    static std::map<std::string, std::string> r;
    return r;
  }

  inline bool register_primary_param(std::string const& strategy, std::string const& param) {
    auto [it, inserted] = primary_params_registry().try_emplace(strategy, param);
    invariant(inserted, "Conflicting primary_param for '" + strategy + "': '" + it->second + "' vs '" + param + "'");
    return true;
  }

  inline std::optional<std::string> primary_param_for(std::string const& strategy) {
    auto& r = primary_params_registry();
    if (auto it = r.find(strategy); it != r.end()) {
      return it->second;
    }
    return std::nullopt;
  }
}

template<typename Derived> class Strategy {
public:
  using Ptr = std::shared_ptr<Derived>;

  using Factory = Ptr (*)(nlohmann::json const&);
 
  virtual ~Strategy() = default;

  virtual nlohmann::json to_json() const = 0;

  virtual std::string display_name() const = 0;

  virtual std::set<ppforest2::types::Mode> supported_modes() const = 0;

  static bool register_strategy(std::string const& name, Factory factory) {
    registry()[name] = factory;
    return true;
  }

  static Ptr from_json(nlohmann::json const& j) {
    auto name = j.at("name").get<std::string>();
    auto& reg = registry();
    auto it   = reg.find(name);
 
    if (it == reg.end()) {
      throw std::runtime_error("Unknown strategy: " + name);
    }
 
    return it->second(j);
  }
 
private:
  static std::map<std::string, Factory>& registry() {
    static std::map<std::string, Factory> r;
    return r;
  }
};

#define PPFOREST2_REGISTER_STRATEGY(StrategyBase, name) \
  inline static const bool registered_ = StrategyBase::register_strategy(name, from_json);
 

#define PPFOREST2_REGISTER_PRIMARY_PARAM(strategy_name, param_name) \
  inline static const bool registered_primary_param_ =              \
      ppforest2::strategies::register_primary_param(strategy_name, param_name);