#ifndef CONST_H
#define CONST_H

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

/**
 * @brief Structure to hold a constant's details.
 */
struct constant {
  std::string name;         ///< Name of the constant
  double value;             ///< Value of the constant
  double uncertainty;       ///< Uncertainty in the constant's value
  std::string unit;         ///< Unit of the constant
  std::string reference;    ///< Reference for the constant's value

  /**
   * @brief overload the << operator for pretty printing
   */
   friend std::ostream& operator<<(std::ostream& os, const constant& c) {
     os << "<" << c.name << ": ";
     os << c.value << "±" << c.uncertainty << " ";
     os << c.unit << " (" << c.reference << ")>\n";
     return os;
   }
};

/**
 * @brief Class to manage a collection of constants.
 */
class constants {
private:
  bool loaded_ = false; ///< Flag to indicate if constants are loaded
  const int col_widths_[6] = {25, 52, 20, 20, 17, 45}; // From the python script used to generate the constants file
  std::map<std::string, constant> constants_; ///< Map to store constants by name

  /**
   * @brief Load constants from a file.
   * @param filename The name of the file to load constants from.
   * @return True if loading was successful, false otherwise.
   */
  bool load(const std::string& filename);

  /**
   * @brief Trim leading and trailing whitespace from a string.
   * @param str The string to trim.
   * @return The trimmed string.
   */
  std::string trim(const std::string& str);

public:
  /**
   * @brief Default constructor.
   */
  constants();

  /**
   * @brief Constructor that initializes constants from a file.
   * @param filename The name of the file to load constants from.
   */
  constants(const std::string& filename);

  /**
   * @brief Check if constants are loaded.
   * @return True if constants are loaded, false otherwise.
   */
  bool is_loaded() { return loaded_; }

  /**
   * @brief Initialize constants from a file.
   * @param filename The name of the file to load constants from.
   * @return True if initialization was successful, false otherwise.
   */
  bool initialize(const std::string& filename);

  /**
   * @brief Get a constant by key.
   * @param key The name of the constant to retrieve.
   * @return The constant associated with the given key.
   */
  constant get(const std::string& key);

  /**
   * @brief Overloaded subscript operator to access constants by key.
   * @param key The name of the constant to retrieve.
   * @return The constant associated with the given key.
   * @throws std::out_of_range if the key is not found.
   */
  constant operator[](const std::string& key) const;

  /**
   * @brief Check if a constant exists by key.
   * @param key The name of the constant to check.
   * @return True if the constant exists, false otherwise.
   */
  bool has(const std::string& key) const;

  /**
   * @brief Get a list of all constant keys.
   * @return A vector of all constant keys.
   */
  std::set<std::string> keys() const;

};

#endif