Predicate.hpp

#pragma once
 
#include <functional>
#include <map>
#include <optional>
#include <string>
 
namespace modulo_core {
 
class Predicate {
public:
  explicit Predicate(const std::function<bool(void)>& predicate_function) : predicate_(std::move(predicate_function)) {
    previous_value_ = !predicate_();
  }
 
  bool get_value() const { return predicate_(); }
 
  void set_predicate(const std::function<bool(void)>& predicate_function) { predicate_ = predicate_function; }
 
  std::optional<bool> query() {
    if (const auto new_value = predicate_(); new_value != previous_value_) {
      previous_value_ = new_value;
      return new_value;
    }
    return {};
  }
 
private:
  std::function<bool(void)> predicate_;
  bool previous_value_;
};
 
}// namespace modulo_core