#ifndef CONST_H
#define CONST_H

#include <string>
#include <fstream>
#include <iostream>
#include <vector>
#include <map>

struct constant {
  std::string name;
  double value;
  double uncertainty;
  std::string unit;
  std::string reference;
}

class constants {
private:
  bool loaded_ = false;
  std::map<std::string, constant> constants_;

  bool load(const std::string& filename);

public:
  constants();

  constants(const std::string& filename);

  bool is_loaded() { return loaded_; }

  bool initialize(const std::string& filename);

  constant get(const std::string& key);

  constant operator[](const std::string& key) const {
    auto it = constants_.find(key);
    if (it != constants_.end()) {
      return it->second;
    } else {
      throw std::out_of_range("Constant '" + key + "' not found.");
    }
  };
  
  bool has(const std::string& key) const {
    return constants_.find(key) != constants_.end();
  };

  std::Vector<std::string> keys() const {
    std::Vector<std::string> keys;
    for (auto it = constants_.begin(); it != constants_.end(); ++it) {
      keys.push_back(it->first);
    }
    return keys;
  };

};

#endif